JPH0999712A - Pneumatic tire excellent in self cleaning performance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve drainage performance, and enhance a degree of freedom of design of groove arrangement by arranging a surface layer having high self-cleaning performance at least in a part or the whole area of a groove bottom and a groove wall of a groove to partition and form a land part. SOLUTION: A rubber layer 1 having high self-cleaning performance, an ordinary tread rubber layer 2 and a belt layer 3 are provided. In the rubber layer 1, when its thickness is denoted by (tC) and a thickness of the tread rubber layer 2 is denoted by (tG), it is better to set these in (tC<0.1 tG). With regard to a characteristic of the rubber layer 1, in order to enhance water repellency, when self-cleaning performance is expressed by a contact angled formed with a waterdrop on a surface of the rubber layer 1, it is preferable to set a difference from the tread rubber layer 2 not less than 5 degrees.

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, and particularly to an attempt to realize stable running by efficiently draining water existing on the ground contact surface of the tire during high speed running in rainy weather. . Here, the property of efficiently discharging water existing on the ground contact surface will be referred to as “self-cleaning property” hereinafter.

[0002]

2. Description of the Related Art With the recent trend toward higher performance in vehicles, there is a tendency toward higher performance in passenger car tires. In particular, tires with a low flatness ratio are predominant in order to obtain great rigidity when the vehicle turns. It is becoming.

By the way, such a tire having a low flatness ratio has a disadvantage that it tends to cause a so-called hydroplaning phenomenon because the drainage property on the contact surface of the tire during rainy running is reduced because the contact width becomes large.

In order to improve the critical speed for causing the hydroplaning phenomenon, various arrangements have been conventionally added to the arrangement of the grooves formed on the tread surface, but there is the following inconvenience, and an effective means is sought. It was the current situation.

That is, since the groove arrangement formed on the tread surface has the same meaning as that in which the land portion is divided into the tread portion, when it is not desired to change the rigidity distribution of the land portion from the viewpoint of other performance, drainage In some cases, such as when a groove arrangement that is different from the groove arrangement that is advantageous for improvement is desired, it may not be possible to determine the groove arrangement only for the purpose of improving drainage performance. There was a limit to what I could do.

[0006]

DISCLOSURE OF THE INVENTION An object of the present invention is to improve the drainage property without considering the groove arrangement in the tread portion, thereby increasing the degree of freedom in designing the groove arrangement. I am in the process of proposing an entry tire.

[0007]

According to the present invention, in a pneumatic tire having a plurality of land portions defined by grooves on the surface of a tire tread portion, the grooves that define the land portions are the groove bottom and the groove wall. A pneumatic tire having a surface layer having a high self-cleaning property at least partially or entirely.

Further, according to the present invention, in a pneumatic tire having a plurality of land portions defined by grooves on the surface of a tire tread portion, the pneumatic tire is characterized by having a surface layer having a high self-cleaning property over the entire area of the tread surface. It is a tire containing.

[0009] Self-cleaning highly surface layer the thickness (t _S), when the thickness of the tread and (t _G), and which satisfies the t _c <0.1 · t _G, the surface layer When the self-cleaning property is indicated by the contact angle formed by the water droplets with the water droplet, the difference between the self-cleaning surface layer and the tread inner layer is 5 degrees or more at the contact angle.

The surface layer having a high self-cleaning property is advantageous in the present invention when it is composed of a rubber layer in which fine particles of a fluorine-based resin are mixed, or in which a rubber layer is mixed with silicon oxide (silica). Conforms to.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In order to increase the critical speed of occurrence of hydroplaning phenomenon that occurs in high speed running in the presence of water on the road surface, such as during rainy weather, a water film should not be formed in the ground contact surface of the tire. The water present at that portion may be rapidly discharged to the outside of the ground contact surface, and for that purpose, it is advantageous to enhance the drainage capacity of the groove provided in the tread portion.

In addition to the arrangement and shape of the grooves, the resistance of the grooves to running water greatly affects the method of enhancing the drainage capacity of the grooves. Therefore, in the present invention, in order to reduce the resistance to running water in the tread portion and reduce the energy loss thereof, the groove bottom of the groove forming the land portion, the groove wall, or the entire tread surface including them is protected against water repellency (repellency). A surface layer having high water resistance, that is, a surface layer having high self-cleaning property is formed. According to this, even if a water film is formed on the ground surface, it is quickly discharged to the outside of the ground surface, Therefore, the critical speed at which the hydroplaning phenomenon occurs is improved.

The high self-cleaning property has an advantage that even if mud adheres to the groove of the tread portion when traveling on a mud wetland, the detachment thereof is easily promoted.

In the present invention, the surface layer having a high self-cleaning property is a rubber layer in which fine particles of a fluorine-based resin are mixed. Fine particles such as methoxysilane) can be used.

The size of the fine particles of the fluorine-based resin is preferably about 4 to 15 μm in view of dispersibility when mixed with rubber, and the content of the fine particles makes the water-repellent (water repellent) effect sufficiently exerted. For the reason, it is preferable to set it to about 20% by weight with respect to the rubber component. As the rubber used for the surface layer, natural rubber, S
BR (styrene-butazine rubber) or a rubber obtained by mixing the same can be used.

As a surface layer having a high self-cleaning property, a mixture of silicone rubber can be applied in addition to the above, but the silicone rubber is inferior in mechanical strength, particularly tensile strength, and the diene rubber and the silicone rubber are combined. Has problems such as inability to co-vulcanize. In the case where the above-mentioned fluorine-based resin is mixed, by using silica (silicon oxide), which has a large adsorptive power with the fluorine-based material, together with the fluorine-based resin, silica, and rubber via the silane coupling agent. Fluorine resin can be firmly bonded.

In a pneumatic tire having a tread pattern as shown in FIG. 1 having land portions r defined by grooves S, an example in which a surface layer having a high self-cleaning property is formed on the entire surface of the tread is shown. 2 shows.

In the figure, 1 is a rubber layer having a high self-cleaning property, 2 is a normal tread rubber layer, and 3 is a belt layer. In the present invention, the thickness of the rubber layer 1 is set to (t _C ), and the thickness of the tread rubber layer 2 is set to (t
_G ), it is preferable that t _c <0.1 t _G , which is about 0.5 to 1.0 mm for a pneumatic tire for a normal passenger car. In addition, regarding the characteristics of the rubber layer 1, in order to improve water repellency (water repellency), self-cleaning property is required
It is particularly preferable that the difference from the tread rubber layer 2 is 5 ° or more when expressed by the contact angle α with the water droplet on the surface of the rubber layer (see Fig. 2), and the contact angle in the rubber layer 1h is 110 ° C. The above is preferable.

When the surface layer is provided on the entire area of the tread, the self-cleaning performance on the land surface is reduced due to the wear due to the increase in the traveling distance, but the initial performance until the end of the tire life is reached for the groove portion. Is retained.

[0020]

EXAMPLE A passenger car tire having a pattern as shown in FIG. 1 and a studless tire having a structure as shown in FIG. (Same as tread rubber in tires)
And the displacement of passenger car tires
It is mounted on a 2500cc rear-wheel drive type domestic passenger car, and two people ride on this vehicle. On a test road with a water depth of 10mm, the limit speed of hydroplaning phenomenon is the same as that of a tire that does not have a surface layer. Based on a comparison, the studless tire was mounted on a front-wheel drive type domestic passenger car with an exhaust displacement of 2000cc, and two people were seated on this vehicle to brake from 40km / h on an icy road surface at -2 ° C. The distances were respectively investigated under comparison with the tire having the structure shown in FIG. 4 (without the surface layer). The results are shown in Table 1.

[0021]

[Table 1]

As is clear from Table 1, in the pneumatic tire according to the present invention, the water existing on the contact surface of the tire can be efficiently discharged, so that the critical speed (HP critical speed) of the hydroplaning phenomenon is It was confirmed that the speed was improved by 2 to 3 km / h and the braking distance was shortened by 5 m as compared with the conventional one.

In particular, in the application to the studless tire having the structure shown in FIG. 3, even if the tread portion is worn away and the surface layer disappears as the traveling distance increases, the surface layer on the sipe wall remains Since it is maintained as it is, good self-cleaning property can be maintained until the end of the life of the tire.

Further, as is clear from Table 1, the rubber mixed with the fluororesin has improved mechanical strength such as 100% modulus. Such studless tires usually use soft rubber such as foam rubber,
With the structure as shown in FIG. 3, the strength of the small blocks separated by sipes can be increased, and the reduction of the ground contact area due to partial lifting of the block surface can be suppressed.

Further, since the sipes can be provided more densely, the running performance on the road surface on ice (friction performance on ice) by the sipes can be further improved.

[0026]

According to the present invention, it is possible to enhance the drainage capacity on the ground contact surface of the tire regardless of the land pattern and groove shape, and to perform stable high speed running even in rainy weather.

[Brief description of drawings]

FIG. 1 is a view showing a main part of a tread pattern of a tire.

FIG. 2 is a diagram showing a configuration of a main part of a pneumatic tire according to the present invention.

FIG. 3 is a diagram showing another configuration of the pneumatic tire according to the present invention.

FIG. 4 is a diagram showing a configuration of a main part of a comparative tire.

[Explanation of symbols]

 1 surface layer 2 tread rubber layer 3 belt layer r land portion S groove portion

Claims (6)

[Claims] 1. A pneumatic tire having a plurality of land portions defined by grooves provided on the surface of a tire tread portion, wherein the grooves defining the land portion are formed on at least a part or the entire area of the groove bottom and groove wall. A pneumatic tire having a surface layer having high self-cleaning property. 2. A pneumatic tire having a plurality of land portions defined by grooves provided on the surface of a tire tread portion, wherein the pneumatic tire has a surface layer having a high self-cleaning property over the entire area of the tread surface. tire. 3. The surface layer having high self-cleaning property is t _S when the thickness is t _S and the tread thickness is t _G.
The pneumatic tire according to claim 1, wherein _c <0.1 · t _G. 4. When the self-cleaning property is indicated by the contact angle formed by the surface layer and water droplets, the difference between the self-cleaning surface layer and the tread inner layer is 5 degrees or more at the contact angle. The pneumatic tire according to claim 1, 2, or 3. 5. The pneumatic tire according to claim 1, wherein the surface layer having a high self-cleaning property is composed of a rubber layer in which fine particles of fluororesin are mixed. 6. The pneumatic tire according to claim 5, wherein the rubber layer is a mixture of silicon oxide.