JPH10147111A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve performance on ice by forming at least a grounding part in a tread of a lamination, in which rubber layers possessing different abrasion resistances are layered adjacently at a specific density, and using a rubber layer containing multiple short fibers for at least one rubber layer in the rubber layers layered in two or more layers. SOLUTION: In a tread 12 provided with a plurality of blocks 18 which are dividedly formed by means of a plurality of circumferential grooves 14 and a plurality of lateral grooves crossing the circumferential grooves 14, an upper layer cap part 12A directly grounding the road surface and a lower layer base part 12B arranged on the inside adjacently to the cap part 12A are provided. The cap part 12A is formed by layering low abrasion resistance rubber layers 20 and high abrasion resistance rubber layers 22 alternately in the tire width direction, and these rubber layers 20, 22 are layered at a density of two layers or more per 10mm. Each rubber layers 20, 22 is formed of rubber containing multiple short fibers, and the percentage content of the fibers is set to 16-30% by weight in the layer 20, while it is set to 1-15% by weight in the rubber layer 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having improved performance on ice.

[0002]

2. Description of the Related Art In recent years, studless tires have been used as tires having improved performance on ice and snow.

In a tread of this kind of studless tire, a crop pattern composed of a plurality of blocks is formed in order to improve the performance on snow.

On the other hand, in order to improve the performance on ice, the tread of this type of studless tire uses a rubber material that is more flexible than a normal tire in order to obtain a frictional force with an icy road surface.

[0005]

It is conceivable to make the rubber material of the tread softer in order to improve the performance on ice, but there is a limit because problems such as a decrease in block rigidity and a decrease in wear resistance occur. In addition, it is conceivable to use many sipes, but there is a limit to the excessive use of sipes because it leads to uneven wear and a decrease in block rigidity.

The present invention has been made in consideration of the above-described circumstances, and has as its object to provide a pneumatic tire capable of improving on-ice performance without deteriorating other performances.

[0007]

The invention according to claim 1 is a pneumatic tire in which a reinforcing layer and a tread are sequentially arranged on the outer periphery of a crown portion of a carcass straddling in a toroidal manner between a pair of bead cores. At least the ground contact portion of the tread is such that rubber layers having different abrasion resistances are adjacent to each other in one section perpendicular to the tread surface, and the rubber layer has a thickness of 10 mm.
And two or more rubber layers, and at least one of the two or more rubber layers has an infinite number of short fibers.

Next, the operation of the pneumatic tire according to the first aspect will be described. When a rubber layer having high wear resistance is compared with a rubber layer having low wear resistance, the rubber layer having low wear resistance has a faster wear development rate. Therefore, when the tread surface (the tread surface) is worn by running, the rubber layer portion having low wear resistance is lower than the rubber layer portion having high wear resistance, and a large number of narrow grooves having a relatively shallow depth are formed on the tread surface. Appear.
The grooves that appear in this way provide drainage and edge effects, and improve on-ice braking performance, on-ice traction performance, and wet performance.

In addition, since this state can be maintained not only at the beginning of wear but also as wear progresses, it is possible to continuously improve on-ice braking performance, on-ice traction performance and wet performance.

Here, when the rubber layer having the highest abrasion resistance, that is, the layer which becomes the convex portion of the uneven surface of the tread when worn, has short fibers, when the tread is worn by running, Innumerable short fibers appear on the tread of the rubber layer having high wear resistance, and the innumerable short fibers appearing on the tread scratch the ice surface, so that the on-ice braking performance and the on-ice traction performance can be improved.

When the countless short fibers appearing on the tread fall off from the rubber due to friction with the road surface, etc., minute recesses are formed where the short fibers fall off. The innumerable concave portions formed on the tread absorb the moisture between the tread and the road surface, so that the braking performance on ice, the traction performance on ice, and the wet performance can be improved.

That is, when the rubber layer having the highest abrasion resistance has short fibers, the effect of scratching the short fibers protruding from the tread surface and the effect of absorbing water by the concave portions after the short fibers fall off can be obtained. .

As specific examples of the short fibers, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyethylene, polypropylene and the like can be mentioned, but other fibers may be used.

The diameter of the short fibers is preferably 10 μm to 1.0 mm, and the length of the short fibers is preferably 2 to 50 mm. Further, the ratio between the length of the short fibers and the diameter of the short fibers is preferably (length of short fibers / diameter of short fibers)> 10.

When the content of short fibers in the rubber layer having the highest abrasion resistance is increased, braking performance on ice, traction performance on ice and wet performance are improved, but abrasion resistance is reduced.

On the other hand, when the rubber layer having low abrasion resistance has countless short fibers, the rubber layer having low abrasion resistance can be more easily worn and the groove can be further deepened.

As a result, the ability to absorb moisture can be enhanced, and the braking performance on ice, traction performance on ice, and wet performance can be improved.

It is sufficient that the grounding portion of the tread has such a laminated structure of rubber layers having different wear resistances, and the entire tread does not necessarily have to have a laminated structure of rubber layers having different wear resistances. . For example, when the tread has a cap-base structure, only the cap portion may have such a laminated structure.

When a rubber layer having high wear resistance and a rubber layer having low wear resistance are alternately laminated, the thickness of the rubber layer having low wear resistance is larger than the thickness of the rubber layer having high wear resistance. It is also preferable that it is thin. If the rubber layer having high abrasion resistance becomes too thick, water does not easily reach the groove, and the drainage property is not improved and the performance on ice is not improved. Conversely, if the rubber layer with low abrasion resistance increases too much, the rubber layer with high abrasion resistance decreases, so that the on-ice performance and abrasion resistance decrease due to a decrease in the actual contact area. Therefore, the ratio of the thickness of the rubber layer having a high abrasion resistance to the thickness of the rubber layer having a low abrasion resistance that appears on the tread contact surface is low when the rubber layer having a high abrasion resistance is 100. It is preferable that the rubber layer has a thickness of 5 to 40.

Further, the thickness of the rubber layer having low abrasion resistance is set to 0.1.
If the thickness is less than 05 mm, even if the tread surface is worn, it is difficult to form a groove on the tread surface. If the thickness of the highly wear-resistant rubber layer is 5.0 mm or more, the thickness of the highly wear-resistant rubber layer is large. The distance to the water becomes longer, the water hardly reaches the ditch, and the performance on ice does not improve.

As a method for providing a difference in abrasion resistance between adjacent rubber layers, a method of changing the hardness of each rubber layer can be used. Alternatively, the rubber type of each rubber layer may be changed.

The low and high abrasion resistance of rubber is determined, for example, according to JIS K 6264 by a Lambourn test under standard test conditions (speed 80 m / min, slip rate 30).
%, A load weight of 40 N, and a falling sand amount of 20 g / min).

When a difference in hardness is provided between adjacent rubber layers, the degree of hardness between adjacent rubber layers is 3 degrees (JIS K6).
Value measured at room temperature according to 301. ), And preferably a hardness difference of 5 degrees or more.

Further, the tread may be any pattern such as a block pattern, a rib pattern, a lug pattern, or the like, and may be without a pattern (without a groove).

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the rubber layer having the highest abrasion resistance among the rubber layers has countless short fibers, and the content thereof is 1%. -15% by weight.

Next, the operation of the pneumatic tire according to claim 2 will be described. The pneumatic tire according to claim 2,
The most abrasion-resistant rubber layer serving as a convex portion has countless short fibers, and the content thereof is set to 1 to 15% by weight. The effect of absorbing moisture by the minute concave portions formed by the fibers falling off the rubber is sufficiently ensured.

When the content of the short fibers is less than 1% by weight, the number of short fibers appearing on the tread decreases, and the scratching action cannot be obtained. Further, the number of minute concave portions formed by the short fibers falling off the rubber is reduced, and the water absorbing action which could not be absorbed and discharged by the groove obtained due to the difference in wear is eliminated. For this reason, the on-ice braking performance, on-ice traction performance, and wet performance are not improved.

On the other hand, when the content of the short fibers exceeds 15% by weight, the wear resistance of the rubber layer having high wear resistance decreases, and the difference in wear resistance between the rubber layer having low wear resistance and the wear resistance decreases. In addition, it is difficult to form a groove obtained by a difference in wear.

According to a third aspect of the present invention, in the pneumatic tire according to the first aspect, the rubber layer having the lowest abrasion resistance among the rubber layers has countless short fibers, and the content thereof is 16%. -30% by weight.

Next, the operation of the pneumatic tire according to claim 3 will be described. By including short fibers in the rubber, the wear resistance of the rubber can be reduced. In the pneumatic tire according to the third aspect, the rubber layer having the lowest wear resistance has countless short fibers, and the content thereof is 16 to
It is 30% by weight. For this reason, the wear resistance of the rubber layer having the lowest wear resistance can be further reduced, and the wear of the rubber layer having the lowest wear resistance can be promoted to form a groove on the tread surface reliably. Become.

When the content of short fibers is less than 16%,
The effect of further reducing the abrasion resistance of the rubber by including short fibers is reduced, and the abrasion resistance of the rubber layer having the lowest abrasion resistance cannot be sufficiently reduced. It becomes difficult to form a groove to be formed.

On the other hand, when the content of the short fibers exceeds 30% by weight, the wear resistance of the entire tread is reduced.

According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects,
Among the rubber layers, the rubber layer with the highest wear resistance and the rubber layer with the lowest wear resistance have countless short fibers, and the shortest of the rubber layer with the highest wear resistance and the rubber layer with the lowest wear resistance are used. The difference in fiber content is 10% by weight or more.

The operation of the pneumatic tire according to claim 4 will be described. In the pneumatic tire according to the fourth aspect, the difference in the short fiber content between the rubber layer having the highest abrasion resistance and the rubber layer having the lowest abrasion resistance is 10% or more. The rubber layer can be surely worn, and the groove can be reliably formed on the tread surface.

Here, when the difference in the content is less than 10%, the wear resistance of the rubber layer having high wear resistance and the rubber layer having low wear resistance are close to each other, and the formation of the groove obtained by the difference in wear is difficult. It becomes difficult.

According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects,
At least the rubber layer having the highest abrasion resistance is characterized by having countless particles.

Next, the operation of the pneumatic tire according to claim 5 will be described. The pneumatic tire according to claim 5,
The rubber layer having the highest abrasion resistance, that is, the layer that becomes the convex portion of the unevenness of the worn tread when worn, has countless particles. When the tread is worn due to running, countless particles appear on the tread, and the countless particles appearing on the tread scratch the ice surface, thereby improving on-ice braking performance and on-ice traction performance.

Further, when these innumerable particles appearing on the tread fall off the rubber due to friction with the road surface or the like, minute recesses are formed where the particles have fallen. The innumerable concave portions formed on the tread absorb the moisture between the tread and the road surface, so that the braking performance on ice, the traction performance on ice, and the wet performance can be improved.

That is, in the present invention, the effect of scratching the particles protruding on the tread surface and the effect of absorbing water by the concave portions after the particles fall off can be obtained.

Specific examples of the particles include those having an aluminum-bonded hydroxyl group and a silicon-bonded hydroxyl group on the surface (for example, Hygilite (trade name) manufactured by Showa Denko), SPB
A resin (crystalline syndiotactic-1,2-polybutadiene resin) or the like is preferable, but other resins may be used. Further, the diameter of the particles is preferably 5 μm to 250 μm. The shape of the particles is not particularly limited.

When the content of particles is increased, braking performance on ice, traction performance on ice and wet performance are improved, but wear resistance is lowered. Therefore, the content of particles is
1-15% by weight is preferred. If the content of the particles is less than 1% by weight, braking performance on ice, traction performance on ice and wet performance will not be improved, and if it exceeds 15% by weight, wear resistance will decrease.

According to a sixth aspect of the present invention, in the pneumatic tire according to any one of the first to fifth aspects,
The rubber layer is laminated along the tire width direction.

Next, the operation of the pneumatic tire according to claim 6 will be described. In the pneumatic tire according to claim 6,
Since the direction of the groove generated by the wear is the tire circumferential direction, the performance of draining the water film on the road surface to the kicking side, that is, the drainage property, can be improved, and in particular, the braking performance on ice can be improved. Further, the coefficient of friction in the lateral direction can be increased, and the cornering performance can be improved.

According to a seventh aspect of the present invention, in the pneumatic tire according to any one of the first to fifth aspects,
The rubber layer is laminated along the tire width direction.

Next, the operation of the pneumatic tire according to claim 7 will be described. In the pneumatic tire according to claim 7, since the direction of the groove that has appeared due to wear is the tire width direction, the drainage action of the edge component extending in the width direction causes
Particularly, traction performance on ice is improved.

The invention according to claim 8 provides the pneumatic tire according to any one of claims 1 to 5,
The rubber layer is laminated in a ring shape.

Next, the operation of the pneumatic tire according to claim 8 will be described. In the pneumatic tire according to claim 8, when the tread surface is worn by running, a large number of thin annual ring-shaped grooves having a relatively shallow depth appear on the tread surface.

Therefore, both the braking performance on ice and the traction performance on ice can be improved by the drainage of the grooves along the tire circumferential direction and the edge components of the portions extending in the width direction of the grooves.

If there are blocks on the tread, it is desirable to form at least one annual ring in one block. In the case where the rib is formed along the circumferential direction of the tire, it is desirable to form a plurality of annual rings along the longitudinal direction of the rib.

The specific shape of the annual ring may be rectangular, circular or the like, but in the present invention, other shapes may be used.

[0051]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment A pneumatic tire 10 according to a first embodiment of the present invention will be described with reference to FIGS.

The pneumatic tire of this embodiment (size: 1)
85 / 70R13, rim: 51 / 2J-13, internal pressure 1.
9 kg / cm ² ) 10 is a pneumatic tire having a radial structure in which a belt and a tread as a reinforcing layer are sequentially arranged on the outer periphery of a crown portion of a carcass straddling a pair of bead cores in a toroidal manner. The internal structure other than the tread is not different from the structure of a general radial tire, and therefore the description is omitted.

As shown in FIG. 1, a plurality of blocks 18 are formed in the tread 12 by a plurality of circumferential grooves 14 and a plurality of lateral grooves 16 intersecting with the circumferential grooves 14.

Each block 18 is formed with four sipes 19 extending linearly in the tire width direction at equal intervals in the tire circumferential direction, and both ends are opened on the side surfaces of the block 18. The block 18 has a length in the tire circumferential direction of 25 mm and a width in the tire axial direction of 20 mm. The sipe 19 has a width of 0.4 mm and is formed at intervals of about 5 mm in the tire circumferential direction.

As shown in FIG. 2, the tread 12 includes an upper cap portion 12A directly in contact with the road surface, and a lower base portion 12B disposed adjacent to the inside of the tire of the cap portion 12A. And a so-called cap-base structure.

In the cap portion 12A, rubber layers 20 having low wear resistance and rubber layers 22 having high wear resistance are alternately laminated in the tire width direction.

As shown in FIG. 3A, the rubber layer 22 having high abrasion resistance is made of a rubber containing countless short fibers 50.

The pneumatic tire 10 provided with such a tread 12 has a rubber layer 20 having low wear resistance and a rubber layer 22 having high wear resistance including short fibers 50 as shown in FIG. Raw (unvulcanized) rubber bands 24 alternately laminated
Is formed, and this is affixed to the outer periphery of a raw tire and vulcanized with a mold. (Operation) Next, the operation of the present embodiment will be described.

When the surface of the tread 12 is worn by running, the rubber layer 20 having low wear resistance develops more than the rubber layer 22 having high wear resistance. As shown in FIG. 5, the rubber layer 20 has high wear resistance. The portion of the rubber layer 20 having low wear resistance is lower than that of the rubber layer 22, and a large number of narrow grooves 26 having a relatively shallow depth appear on the surface of the tread 12.

The grooves 26 appearing in this way have a shape extending along the circumferential direction of the tire, and the grooves 26 appearing plurally provide drainage, thereby improving the braking performance on ice, traction performance on ice, and wet performance. The braking performance on ice is improved.

When the rubber layer 22 having high abrasion resistance is worn, as shown in FIG.
Appears, and these countless short fibers 50 appearing on the tread surface scratch the ice surface, and the braking performance on ice and the traction performance on ice can be further improved.

The countless short fibers 5 appearing on the treads
When 0 falls off from the rubber due to friction with the road surface or the like, a minute concave portion 52 is formed where the short fiber 50 has fallen off. The innumerable concave portions 52 formed on the tread absorb the moisture between the tread and the road surface, so that the braking performance on ice, the traction performance on ice, and the wet performance can be further improved.

Since this state can be maintained not only at the beginning of wear but also as wear progresses, it is possible to continuously improve on-ice braking performance, on-ice traction performance and wet performance.

Further, since a groove 26 extending along the tire circumferential direction appears on the tread surface, an effect of preventing a side slip during cornering can be obtained. Second Embodiment A pneumatic tire 10 according to a second embodiment of the present invention will be described with reference to FIG. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 6, in the pneumatic tire 10 according to the second embodiment, the cap portion 12A is composed of a rubber layer 20 having low wear resistance and a rubber layer 22 having high wear resistance. The layers are alternately stacked in the direction (the direction of arrow A in FIG. 6).

Next, the operation of the present embodiment will be described. When the surface of the tread 12 is worn by running, as described in the first embodiment, the portion of the rubber layer 20 having low wear resistance is lower than that of the rubber layer 22 having high wear resistance. In the embodiment, a plurality of grooves 26 extending along the tire width direction appear on the surface of the tread 12. Since the direction of the emerged groove 26 is the tire width direction, the pneumatic tire 10 of the present embodiment particularly has improved traction performance on ice due to the drainage action of the edge component extending in the width direction.

Further, the short fibers 50 appearing on the tread of the rubber layer 22 having high wear resistance scratch the ice surface, and the concave portions 52 (not shown in FIG. 6) after the short fibers 50 fall off the road surface. Since the water in between is absorbed, braking performance on ice, traction performance on ice, and wet performance can be further improved. Third Embodiment A pneumatic tire 10 according to a third embodiment of the present invention will be described with reference to FIGS.
The same components as those of the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 7, the block 18 of the pneumatic tire 10 according to the third embodiment has a rubber layer having low abrasion resistance when viewed in a cross section orthogonal to the tire radial direction (the direction of arrow R). 20 and a rubber layer 22 having high wear resistance are laminated in the shape of a tree ring.

In the pneumatic tire 10 provided with such a tread 12, a rubber layer 20 having low wear resistance and a rubber layer 22 having high wear resistance as shown in FIG. 8 are alternately laminated in the thickness direction. It can be formed by forming a raw (unvulcanized) rubber band 34, pasting it on a belt of a green tire, and vulcanizing with a mold. When the rubber band 34 is pressed against the inner surface of the mold, the rubber band 34 composed of a plurality of layers enters into a plurality of concave portions (portions forming blocks) formed on the inner surface of the mold, thereby forming an annual ring.

The block 1 formed by the above method
A predetermined range C on the outer peripheral side of the rubber layer 8 is a rubber layer 20 having low wear resistance.
Since the rubber layer 22 and the highly wear-resistant rubber layer 22 overlap in the tire radial direction, it is preferable that the rubber in the predetermined range C is shaved off by buffing or the like after vulcanization molding.

Next, the operation of the present embodiment will be described. When the surface of the tread 12 is worn by running, as described above, the portion of the rubber layer 20 having low wear resistance is lower than the portion of the rubber layer 22 having high wear resistance, but in the present embodiment,
A plurality of annual ring-shaped grooves 26 appear on the surface of the tread 12. Since the direction of the emerged groove 26 has both the component in the tire width direction and the component in the tire circumferential direction, the draining action by the edge effect by the component in the tire width direction and the drainage by the component in the tire circumferential direction are reduced. At the same time, the brake performance on ice and the traction performance on ice can be improved.

Further, the short fibers 50 appearing on the tread of the rubber layer 22 having high abrasion resistance scratch the ice surface, and the concave portions 52 (not shown in FIG. 7) after the short fibers 50 fall off the road surface. Since the water in between is absorbed, braking performance on ice, traction performance on ice, and wet performance can be further improved. Fourth Embodiment A pneumatic tire 10 according to a fourth embodiment of the present invention will be described with reference to FIG. The same components as those of the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 9, a block 18 of the pneumatic tire 10 according to the fourth embodiment includes a sipe 1 similar to the pneumatic tire 10 described in the first embodiment.
9 are formed.

The pneumatic tire 10 according to the present embodiment is manufactured in the same manner as the pneumatic tire 10 according to the third embodiment, except that an annual ring is formed for each small block defined by the sipe 19. .

The pneumatic tire 10 of the present embodiment also has a draining action due to an edge effect due to a component in the tire width direction of a groove generated by running, similarly to the above-described pneumatic tire 10 of the third embodiment. The drainage property of the component can be obtained at the same time, and the edge effect by the sipe 19 can be obtained.

Further, the short fibers 50 appearing on the tread of the rubber layer 22 having high abrasion resistance scratch the ice surface, and the recesses 52 (not shown in FIG. 9) after the short fibers 50 fall off the road surface. Since the water in between is absorbed, braking performance on ice, traction performance on ice, and wet performance can be further improved. (Test Example) The braking performance on ice, the traction performance on ice and the abrasion resistance performance were compared using one kind of conventional tire, 16 kinds of tires of the example to which the present invention was applied, and one kind of tire of the comparative example.

Next, a method of testing the brake performance on ice will be described. The tire was mounted on an actual vehicle and the vehicle was driven on a flat road on ice. At a speed of 20 km / h, the brake was depressed to lock the tire, and the distance to stop was measured. The result is shown as an index with the reciprocal of the distance as the conventional tire 100. The larger the value, the better the braking performance on ice.

Test Method of Traction Performance on Ice The tire was mounted on an actual vehicle, the vehicle was started from a state where the flat road on ice was stopped, and the reciprocal of the time required to reach a distance of 50 m was indicated as an index as a conventional tire 100 as an index. The larger the value, the better the traction performance on ice.

Test Method for Wear Resistance Performance The tire was mounted on an actual vehicle, and the amount of wear (depth of a worn groove) after running 10,000 km was measured. The larger the value, the better the abrasion resistance performance.

Next, the test tire will be described. Each of the test tires has the block pattern shown in FIG. 1, and four blocks are arranged in the tire width direction and at a pitch of 50 mm in the tire circumferential direction. The size of the block is 25 mm in the tire circumferential direction and 20 mm in the tire width direction.
It is.

A rubber having a hardness of 38 degrees was used for the rubber layer having low wear resistance, and a rubber having a hardness of 50 degrees was used for the rubber layer having high wear resistance.

The tires of Examples 1 to 16 are tires having short fibers in a rubber layer having low wear resistance and / or a rubber layer having high wear resistance. The short fibers have an average diameter of 50μ.
m, a cylindrical PET having an average length of 2000 μm was used. The short fiber content is as shown in Tables 1 to 3 below.

The tires of Examples 11 and 12 are tires using a rubber layer having high abrasion resistance using foamed rubber.

Here, the porosity Vs of the foamed rubber is given by:
It is represented by (ρ ₀ / ρ ₁ -1) × 100 (%). In addition,
ρ ₁ is the density (g / cm ³ ) of the rubber having microcavities, ρ
₀ is the density (g / cm) of the solid phase portion of the rubber having microcavities.
³ ). When the foaming rate Vs of the foamed rubber increases, the abrasion resistance decreases.

In order to efficiently absorb the water film,
The average cavity diameter of the microcavities is desirably 5 to 150 µm, preferably 10 to 100 µm.

If the rubber layer having the highest abrasion resistance has a porosity of less than 2%, the effect of absorbing water that could not be discharged by the groove cannot be obtained. On the other hand, if the porosity of the rubber layer having the highest wear resistance exceeds 20%, the wear resistance is reduced, and the rubber layer becomes closer to the wear resistance of the rubber layer having low wear resistance. For this reason, it becomes impossible to deepen the groove appearing on the tread, and the drainage performance is reduced.

The tires of Examples 13 and 14 are tires in which innumerable particles falling off the rubber due to friction with the treads and the like are contained in a rubber layer having high wear resistance. Note that SPB resin having an average diameter of 50 μm was used for the particles. The particle content is as shown in Tables 1 to 3 below.

The tire of Example 16 is a tire in which a rubber layer having high abrasion resistance and a rubber layer having low abrasion resistance are laminated on a block in an annual ring shape. Note that the number of layers described in the table is the maximum number of layers appearing in the block, and the thickness is an average value.

The tire of the comparative example is a tire in which a low-wear rubber layer containing no short fibers and a high-wear rubber layer are alternately laminated in the tire width direction. The hardness of the rubber layer, sipes, and the size and arrangement of the blocks are the same as those of the tire of Example 1. The thickness and the number of laminated rubber layers are as shown in Table 1 below.

The conventional tire is a tire in which the cap portion of the tread is entirely formed of a highly wear-resistant rubber layer containing short fibers. The size and arrangement of the sipes and blocks are the same as those of the tire of the first embodiment.

Number of rubber layers laminated, thickness, shape, short fiber content, difference in content, particle content, test results on ice traction performance, test results on traction performance on ice, test results on wear resistance Is as shown in Tables 1 to 3 below.

[0092] In the test, a tire having a groove formed on the tread surface after running was used.

[0093]

[Table 1]

[0094]

[Table 2]

[0095]

[Table 3]

Short fiber = Material: PET, average diameter: 50 μm, average length:
A cylinder having a size of 2000 μm. Particle = Material: SPB resin, sphere having an average diameter of 50 μm.

As shown in Tables 1 to 3 above, the tires of Examples 1 to 16 in which the lamination direction of the rubber layer is the circumferential direction of the tire and the rubber layer contains short fibers have the braking performance on ice and the traction performance on ice. It can be seen that the tire is improved as compared with the conventional tire and the comparative tire.

In particular, it can be seen that the tires of Examples 1 to 14 in which the laminating direction of the rubber layer is the tire width direction have more improved on-ice braking performance than on-ice traction performance.

Further, it can be seen that the traction performance on ice is further improved as compared with the brake performance on ice in Example 15 in which the lamination direction of the rubber layer was the circumferential direction of the tire.

Example 16 in which the rubber layer had an annual ring shape
It can be seen that the tire of No. 1 has improved both the braking performance on ice and the traction performance on ice at substantially the same level.

[0101] Regarding the abrasion resistance, if the index is 90 or more, there is no practical problem.

In the pneumatic tire 10 of the above embodiment, the groove 26 does not appear on the surface of the tread when it is new, so that it is necessary to perform a break-in run although the distance is extremely short. For this reason, in order to obtain high performance on ice from the time of new product, until the groove 26 appears due to the difference in rubber wear, the groove 26 has almost the same size as the groove 26 appearing due to the difference in wear, and the groove 26 appears. A large number of shallow narrow grooves which may disappear at the time may be formed on the surface of the tread 12.

In the pneumatic tires 10 of the first and second embodiments, the rubber layer 20 having a low wear resistance and the rubber layer 22 having a high wear resistance have a linear shape on the surface of the tread 12. , But may be wavy or zigzag.

[0104]

As described above, in the pneumatic tire according to the first aspect, a large number of narrow grooves having a relatively shallow depth appear on the tread surface, and the drainage action and the edge effect of these grooves cause braking on ice. It has an excellent effect of improving performance, traction performance on ice and wet performance. Furthermore, since this state can be maintained not only at the beginning of wear but also as wear progresses, it is possible to continuously improve the braking performance on ice, the traction performance on ice, and the wet performance. Has an effect.

In the pneumatic tire according to the second aspect, the innumerable short fibers appearing on the tread of the rubber layer having the highest abrasion resistance, which is the convexity of the unevenness of the worn tread, scratches the ice surface by braking action on ice. And the traction performance on ice can be further improved. Furthermore, the minute recesses formed after the short fibers appearing on the treads fall off the rubber can absorb the water film that could not be discharged by the grooves formed on the treads. It has an excellent effect that traction performance and wet performance can be further improved.

In the pneumatic tire according to the third aspect, a groove can be reliably formed on the tread by promoting abrasion of the rubber layer having the lowest abrasion resistance, and high braking performance on ice, traction performance on ice and wetness can be achieved. It has an excellent effect that performance can be ensured.

In the pneumatic tire according to the fourth aspect, the difference in the short fiber content between the rubber layer having the highest abrasion resistance and the rubber layer having the lowest abrasion resistance is 10% by weight or more. This has an excellent effect that a rubber layer having low abrasion can be surely worn and a groove can be reliably formed on the tread surface.

The pneumatic tire according to the fifth aspect has an excellent effect that the innumerable particles appearing on the tread can scratch the ice surface to further improve the braking performance on ice and the traction performance on ice. further,
The minute recesses formed after the particles appearing on the tread have fallen from the rubber can absorb the water film that could not be discharged by the groove formed on the tread, and this allows braking performance on ice, traction performance on ice and It has an excellent effect that the wet performance can be further improved.

[0109] In the pneumatic tire according to the sixth aspect, the direction of the groove that appears due to wear becomes the tire circumferential direction, so that the performance of draining the water film on the road surface to the kicking side, that is, the drainage property can be improved. It has an excellent effect that the braking performance on ice can be improved. Further, the coefficient of friction in the lateral direction can be increased, and the cornering performance can be improved.

In the pneumatic tire according to the seventh aspect, since the direction of the groove that appears due to wear is the tire width direction, the traction on ice can be particularly improved by the drainage action of the edge component extending in the width direction. , Which is an excellent effect.

In the pneumatic tire according to the eighth aspect, when the tread surface is worn by running, a large number of thin annual ring-shaped grooves having a relatively shallow depth appear on the tread surface, and these grooves are formed in the tire circumferential direction. And the traction performance on ice can be improved by the drainage property of the portion along the width and the edge component of the portion extending in the width direction of these grooves.

[Brief description of the drawings]

FIG. 1 is a plan view of a tread of a pneumatic tire according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the tread shown in FIG. 1 along a tire width direction.

FIG. 3A is an enlarged sectional view of a highly wear-resistant rubber layer containing short fibers, and FIG. 3B is an enlarged sectional view of a worn and highly wear-resistant rubber layer.

FIG. 4 is a perspective view of a rubber band-shaped material which will later become a cap portion of the tread shown in FIG. 2;

FIG. 5 is a cross-sectional view of the tread after wear.

FIG. 6 is a cross-sectional view taken along a tire circumferential direction of a tread of a pneumatic tire according to a second embodiment of the present invention.

FIG. 7 is a perspective view showing a cross section of a part of a block of a pneumatic tire according to a third embodiment of the present invention.

FIG. 8 is a perspective view of a rubber band for forming the block shown in FIG. 6;

FIG. 9 is a perspective view showing a cross section of a part of a block of a pneumatic tire according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 20 Rubber layer with low wear resistance 22 Rubber layer with high wear resistance 50 Short fiber

Claims (8)

[Claims] 1. A pneumatic tire in which a reinforcing layer and a tread are sequentially arranged on the outer periphery of a crown portion of a carcass straddling in a toroidal manner between a pair of bead cores, at least a ground contact portion of the tread is orthogonal to a tread surface. In one section, rubber layers having different abrasion resistances are adjacent to each other, the rubber layers are laminated at least two layers per 10 mm, and at least one of the rubber layers laminated at least two is innumerable. A pneumatic tire having short fibers. 2. The air according to claim 1, wherein the rubber layer having the highest abrasion resistance among the rubber layers has countless short fibers, and has a content of 1 to 15% by weight. Containing tires. 3. The air according to claim 1, wherein the rubber layer having the lowest abrasion resistance among the rubber layers has countless short fibers, and the content thereof is 16 to 30% by weight. Containing tires. 4. The rubber layer having the highest wear resistance and the rubber layer having the lowest wear resistance among the rubber layers have countless short fibers, and the rubber layer having the highest wear resistance and the rubber layer having the highest wear resistance The pneumatic tire according to any one of claims 1 to 3, wherein the difference in the short fiber content of the low rubber layer is 10% by weight or more. 5. The pneumatic tire according to claim 1, wherein at least the rubber layer having the highest wear resistance has countless particles. 6. The pneumatic tire according to claim 1, wherein the rubber layer is laminated along a tire width direction. 7. The pneumatic tire according to claim 1, wherein the rubber layer is laminated along a tire circumferential direction. 8. The pneumatic tire according to claim 1, wherein the rubber layers are laminated in a ring shape.