JPH03258603A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To absorb a pseudo water screen on an ice road surface and to ensure a coefficient of friction of a tread portion by burying a lot of fiber bundles where tread rubber will not penetrate the core portion in the tread rubber, and exposing the end surfaces of the respective fiber bundles to the surface of the tread portion. CONSTITUTION:A lot of blocks are formed by main grooves 1 and subsidiary grooves 2 on the surface of a tread portion T installed on a carcass layer 4. In this case, a lot of fiber bundles (f) are buried in the tread rubber for forming the respective blocks 3. The respective fiber bundles (f) buried in such a manner as to be paralleled substantially in the vertical direction with respect to the surface of the tread portion T, not to make the tread rubber penetrate into the core portion, and to expose the cut end surfaces to the surfaces of the respective blocks 3 (tread portion T). By this arrangement, the capillary phenomenon of each fiber bundle (f) is used to absorb a pseudo water screen, and the water content is discharged by the centrifugal force produced by the rotation of the tire so as to ensure a coefficient of friction of the tread portion T.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic tire with excellent running performance on ice.

[Conventional technology]

Spiked tires have been widely used for driving on icy and snowy roads, but their use is about to be legally prohibited because their running destroys the road surface and causes pollution such as the generation of large amounts of dust.

Therefore, as a tire that can be substituted for the above spike tires,
For example, there are pneumatic tires whose tread rubber has a lower hardness (Japanese Patent Application Laid-Open No. 63-314253) and pneumatic tires whose tread surface is provided with a foamed rubber layer containing closed cells (Japanese Patent Application Laid-open No. 62283001). Proposed. However, when these tires are driven on icy roads where a pseudo-water film is formed at temperatures around 0 to -5°C, their coefficient of friction decreases significantly, making them difficult to replace spiked tires with excellent on-ice performance. There wasn't.

[Problem to be solved by the invention]

An object of the present invention is to provide a pneumatic tire that can stably exhibit its performance on ice by suppressing a decrease in the coefficient of friction of the tread portion even when driving on an icy road surface where a pseudo-water film is formed. There is a particular thing.

[Means to solve the problem]

The object of the present invention is to provide a tread portion of a pneumatic tire with a large number of fiber bundles in a tread rubber having a JIS hardness of 45 to 60, so that the tread rubber does not substantially penetrate into the core, and the end surface is This can be achieved by providing a buried tread portion that is exposed on the surface.

In the present invention, JTS hardness refers to JIS-K 630
This refers to the value measured at 20°C according to the measurement method specified in 1.

FIG. 1 is a perspective sectional view for explaining the structure of the tread portion of the tire of the present invention. As shown in the figure, the lower part of the tread is placed on a carcass layer 4, and a large number of blocks 3 defined by main grooves 1 and sub-grooves 2 are formed on the surface thereof. A large number of fiber bundles f are embedded in the tread rubber constituting this block 3.

The fiber bundle f is buried so as to be aligned in a direction substantially perpendicular to the tread surface, and the tread rubber does not penetrate into the core, so that the cut end surface is aligned with the block 3 (+-
Red part) is exposed on the surface. In this way, the fiber bundles exposed on the tread surface absorb water from the cut end surface by capillary action, and at the same time release the water absorbed by the fiber bundles f by centrifugal force when the tire rotates. Therefore, the tire of the present invention effectively removes the pseudo water film on the icy road surface and does not reduce its coefficient of friction, so it can stably exhibit excellent ice performance.

The moisture absorption and release of the tire of the present invention described above is due to the capillarity of the core of the fiber bundle exposed on the surface of the tread portion. In order to effectively utilize this capillary phenomenon, it is necessary to prevent the tread rubber from penetrating into the core of the fiber bundle, but in addition, the thickness and length of the fiber bundle embedded in the tread rubber must be Further improvement can be achieved by increasing the embedding density.

As for the thickness of the fiber bundle, a bundle of 50 to 100 filaments of 1 to 40 deniers is used.

The burial density is 5 to 100 pieces per ground surface.
A range of cm2 is preferable. If the thickness of the fiber bundle is too small, durability will be poor, and if it is too thick, the rubber will be press-fitted into the fiber bundle during vulcanization, impairing water absorption. Furthermore, if the embedding density is less than 10 pieces/cm2, the desired effect of the present invention will not be fully achieved, and if it exceeds 100 pieces/cm2, the strength of the tread block itself will decrease, resulting in poor durability and impractical.

Furthermore, it is desirable that this fiber bundle is a twisted yarn. By applying twist, it is possible to make it difficult to pull out the fibers in the core portion, which are not penetrated by the tread rubber, from the tread surface.

Examples of fibers forming such fiber bundles include:
Various organic fibers such as nylon fiber, polyester fiber, polyolefin fiber, rayon fiber, ARA5 fiber, cotton,
There are natural fibers such as hemp, and inorganic fibers such as glass fibers and carbon fibers.

These fibers can be used not only alone, but also in combination of two or more types. Further, in order to ensure adhesion with the rubber matrix, it is preferable to perform an adhesive treatment such as resorcinol formalin latex (RF L) treatment.

It is desirable that the fiber bundles are buried straight so that the angles of their long axes with respect to the tread surface are the same for all the fiber bundles.

Normally, as shown in FIG. 2, the fiber bundle f at the center in the width direction of the block 1 is buried so as to be almost perpendicular to the tread surface, and as it moves away from the center to both sides, the tread surface side becomes larger. It is usually curved and buried so as to be inclined with respect to the tread surface. Further, as shown in FIG. 2, it is desirable that the tread portion T in which the fiber bundle f is embedded has an undertread rubber layer 5 at its lower part (carcass layer side). By providing this undertread rubber layer 5, it is possible to strengthen the groove bottom and prevent the occurrence of cranks and the like.

The tread rubber is composed of rubber having a JIS hardness of 45 to 60 in order to basically satisfy the performance of the tire of the present invention on icy and snowy roads. If the JIS hardness of the tread rubber exceeds 60, adhesion to icy road surfaces will be insufficient, and the performance of the tire on icy and snowy roads will deteriorate. Furthermore, if the JIS hardness is less than 45, the durability will decrease.

Such tread rubber includes, for example, natural rubber (NR), polyisoprene rubber (I) as a rubber component.
R), using polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), halogenated butyl rubber, etc., and adjusting the amount of compounding chemicals such as carbon black and oil so as to satisfy the rubber hardness within the above range. may be appropriately selected and blended.

Next, one example of the method for manufacturing the tire of the present invention will be described below.

FIGS. 3A and 3B are explanatory diagrams showing one example of a method for manufacturing the tread portion of the tire of the present invention.

As shown in FIG. 3(a), unvulcanized tread rubber 12 is extruded using an extruder for covering cords, for example, cold feed extruder E, and a plurality of unvulcanized tread rubbers 12 are aligned at predetermined intervals. A sheet-like rubber molded product 13 is produced by coating the fiber bundle f.

Next, the obtained sheet-like rubber molded product 13 is shown in FIG.
As shown in the figure, the rubber block is formed by inserting it into a frame consisting of two equally spaced plate-shaped bodies 14.14' and sequentially folding them and overlapping them to form a rubber block. By slicing the upper and lower surfaces of this rubber block to remove the bent portions of the sheet-like rubber molded product 13 (fiber bundle f), and cutting both sides of the rubber block, fiber bundles are formed as shown in FIG. A rubber sheet 15 is obtained in which the f is arranged substantially in parallel and the cut end faces thereof are exposed on the surface. In order to reinforce both sides of this rubber sheet 15 (constituting one end of the shoulder of the tread portion), triangular wing tips 16 made of the same unvulcanized tread rubber, which were separately produced, were pasted together as shown in FIG. Rubber sheet 17 for tread construction
Create.

The tire of the present invention can be manufactured by forming a green tire using the rubber sheet 17 for tread construction obtained in this manner and vulcanizing the green tire according to a conventional method.

〔Example〕

The rubber composition shown in the table was used as the tread rubber.

(Margins below on this page) In addition, we used RFL-treated nylon 6-fiber cord with a single yarn fineness of 6 denier, 140 filaments, and 49 twists as the fiber bundle, and created a tread as shown in Figure 4. A rubber sheet for construction was produced.

The thickness of this rubber sheet for tread construction is 10nv+.

The average length of the fiber bundles is 10 mm, and the average mutual spacing is 1.5 m.
m, and the buried density was 44 pieces/cm2.

A tire of the present invention having a tire size of 165/80R13 was produced using the rubber sheet for composition 1 to red.

For comparison, a rubber sheet for a trend structure without embedded fiber bundles was produced using the rubber composition, and a comparative tire of the same size was produced using this as a tread portion.

For these two types of tires, the temperature is -5°C1 freezing temperature-
The following performance test on ice was conducted on an icy road surface at 3°C.

丞± Hill Blood Run (Ice performance index: K) 1500 at a vehicle speed of 40 km/hr on a smooth icy road surface
The braking distance of a cc passenger car (FF car) from when it applied full braking to when it came to a complete stop was measured. The ratio of the braking distance Lo of the reference tire (comparison tire) to the braking distance expressed by the following formula was taken as the on-ice performance index.

K= (Lo/L)

The ice performance index of the tire of the present invention is 115,
It was found that on-ice performance was improved.

〔Effect of the invention〕

According to the present invention, a large number of fiber bundles in which the tread rubber does not substantially penetrate into the core part are embedded in a tread rubber having a specific rubber hardness, and the end surfaces of the fiber bundles are placed on the surface of the trend part. By providing an exposed tread part, the pseudo water film that forms on the icy road surface is absorbed by the capillary action of the fiber bundles exposed on the surface of this tread part, and the absorbed water is released by centrifugal force during rotation. Therefore, the friction coefficient of the trend portion does not decrease while driving on ice. Therefore, excellent on-ice performance can be stably exhibited.

[Brief explanation of drawings]

FIG. 1 is a perspective sectional view showing an example of the trend section of the tire of the present invention, FIG. 2 is a sectional view in the tire width direction of a block that takes over the tread section of FIG. B) is an explanatory view showing one example of a method for manufacturing a tread portion in which fiber bundles are embedded, and FIG. 4 is a cross-sectional view of 1 to tread obtained by the same manufacturing method. T: Tread portion, f: Fiber bundle, E: Extruder, 1: Main groove, 2: Minor groove, 3: Block, 12: Tread rubber.

Claims (1)

[Claims] A pneumatic tire having a tread portion in which a large number of fiber bundles are embedded in tread rubber having a JIS hardness of 45 to 60 in such a way that the tread rubber does not substantially penetrate into the core portion and end faces are exposed on the surface.