JPH0761209A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve wear resistance and irregular wear resistance on a dry road with braking performance kept on an ice and snow road by forming a tread rubber in two layers, and arranging a base rubber layer on the inside and a cap rubber layer composed of a rubber composition in which a soft short fiber consisting of an organic fiber exists mixedly on the outside. CONSTITUTION:A tread part 1 is provided with a tread rubber 15 composed of a base rubber layer 16 extending along a tire constructing layer 8 in the direction of a tire axis and a cap rubber layer 17 to cover a land face 12 and a groove wall face 11. The base rubber layer 16 is formed of a hard rubber whose JISA hardness is 58 to 68 degrees at 0 deg.C, and the cap rubber layer 17 is formed of rubber composition which is 50 to 60 degrees in JISA hardness at 0 deg.C and has a short combined fiber formed of organic fiber material. The ratio ti/T of the thickness t1 of the base rubber layer 16 on the land face 12 to the whole thickness T of the tread rubber is 0.3 to 0.6. Siping 14 taking the base rubber layer 16 as the depth of cut is formed on the land face 12, and the maximum depth of the siping is 0.6 to 0.9 times as deep as a groove 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having improved wear resistance and uneven wear resistance in running on a dry road surface while maintaining running performance on an ice or snow road surface.

[0002]

2. Description of the Related Art For example, a vehicle that travels in a cold and snowy region such as Hokkaido or Tohoku region uses spike tires for traveling on a snowy road in winter.

In such a spiked tire, when the vehicle travels on a snowy road, the spike bites into the snow to improve grip performance and improve running stability, while when the vehicle travels on a dry road surface free of snow, the spiked tire is damaged. The road surface is scraped off, ruts are generated, which deteriorates the steering stability, and dust is generated by scraping the road surface.

In order to solve such a problem, so-called studless tires, which have no protrusion on the tread surface and do not generate dust, are being used. Studless tires have improved grip performance by lowering the hardness of rubber and increasing the radial edge component of siping provided on the tread surface.

On the other hand, such a studless tire is
The user is often fitted with full-scale snowfall on the vehicle within a month or two and before, and therefore may drive on a dry road surface without snowfall.

[0006]

However, when traveling on a dry road surface, the above-mentioned studless tire is
There is a problem that the tread portion is rapidly worn or unevenly worn, and the durability is significantly impaired.

In order to solve one of these problems, (a) the depth of siping is made shallow. (B) Change the siping interval. (C) Increase block rigidity. As a result, a proposal has been made in which both the running property on ice and snowy roads and the retention of wear resistance are achieved, but in (a), the appearance of the tire after wear is impaired and the commercial value is reduced.

In the case of (b), since the rotation direction of the tire is limited to one direction, it is necessary to confirm the direction of the tire at the time of mounting, tire replacement is troublesome, and the tire performance is remarkably impaired by the wrong direction. Moreover, in the case of (c), the running performance on snow is deteriorated, which is not practical.

Further, Japanese Patent Publication No. 62-28001 proposes to form the tread using an elastomeric material having pores, but this one also has not been able to sufficiently improve the running performance during ice and snow.

As a result of repeated studies to solve the above-mentioned problems, the inventors of the present invention have two layers of tread rubber, a hard base rubber layer on the inner side, and a soft and organic staple fiber on the outer side. By disposing a cap rubber layer made of mixed rubber composition and further cutting the sipe to the base rubber layer at the deepest position, it is possible to dry while maintaining the running performance on the ice and snow road in winter. It has been found that the wear resistance and the uneven wear resistance can be enhanced with respect to running on a road surface.

It is an object of the present invention to provide a pneumatic tire having improved wear resistance and uneven wear resistance against running on a dry road surface while maintaining the running performance on ice and snow roads, particularly the braking performance on ice and snow roads.

[0012]

SUMMARY OF THE INVENTION The present invention is directed to a carcass which folds from a tread portion to a sidewall portion and is folded back at a bead core of a bead portion, and a belt layer which is arranged radially outside the carcass and inside the tread portion. A tire structure layer comprising a tire structure layer including, and a land surface which forms a tread outer surface by recessing a groove in the tread portion, and a sea surface sandwiched by a groove wall surface of the groove, and the tire structure layer in the tread portion. Along with the base rubber layer extending in the tire axial direction, the tread rubber consisting of the cap rubber layer covering the land surface and the groove wall surface by extending in the tire axial direction on the radial outside of the base rubber layer. In the pneumatic tire arranged, the base rubber layer is harder than the cap rubber layer and has a J value at 0 ° C.
The ISA hardness is made of rubber of 58 to 68 degrees, and the cap rubber layer is made of short fibers made of organic fiber material having a JIS A hardness of 50 to 60 degrees at 0 ° C. and 2 to 100 parts by weight of rubber.
The rubber composition is composed of 10 parts by weight, and the ratio t1 / T between the thickness t1 of the base rubber layer on the land surface and the total thickness T of the tread rubber is 0.3 to 0.6. ,
Moreover, at least one end of the sipe is formed on the land surface so as to open at the groove wall surface and has a depth that cuts into the base rubber layer, and the sipe maximum depth HS at the deepest position of the sipe is the depth of the groove. 0.6 to 0.9 times the groove depth g, and the cutting depth HN at which the siping cuts the base rubber layer and the siping maximum depth HS.
And a ratio HN / HS of 0.08 or more and 0.3 or less.

[0013]

The tread rubber is formed by the cap rubber layer and the cap rubber layer arranged on the outer side in the radial direction,
The base rubber layer is formed of rubber having a JISA hardness of 58 to 68 degrees at 0 ° C.

By using a hard rubber for the base rubber layer, dynamic strain during running of the tire is reduced, and since rigidity and strength are high, uneven wear can be effectively suppressed. Furthermore, by locating the groove bottom of the siping on this base rubber layer, the breaking force generated at the groove bottom can be reduced, so that the occurrence and growth of cracks can be suppressed, and the tread portion damage originating from the groove bottom of the siping. Can be prevented.

If the rubber hardness is less than 58 degrees of JISA hardness, dynamic strain is not reduced and uneven wear is likely to occur. If it exceeds 68 degrees, the dimensional accuracy is not stable and the rubber thickness is not stable in manufacturing.

The cap rubber layer is formed by using a rubber composition having a JIS A hardness of 50 to 60 degrees. 5
If it is less than 0 degrees, the land surface, which is the outer surface of the tread, is soft and the normal wear is large, resulting in poor durability. On the other hand, if it exceeds 60 degrees, the grip force will decrease when traveling on ice and snow,
This leads to deterioration in traction and braking performance.

Further, the cap rubber layer is formed by using a rubber composition in which short fibers made of organic fibers are mixed in a ratio of 2 to 10 parts by weight with respect to 100 parts by weight of rubber. By adding such short fibers, the strength is increased and it is possible to prevent the land surface from being cut due to stone trapping etc. when driving on dry road surfaces. Since such unevenness is formed, the grip force and the braking performance are improved by enhancing the edge effect on the ice and snow road surface. If the mixing ratio of the short fibers is less than 2 parts by weight, the land surface will have less unevenness and the edge effect will not be exhibited. If a large amount of the compound is added in excess of 10 parts by weight, the reinforcing property of the rubber will be deteriorated and the abrasion resistance will be poor.

Further, the ratio t1 / T of the thickness t1 of the base rubber and the total thickness T of the tread rubber on the land surface is 0.3 to 0.6.
I am trying. When the ratio t1 / T is less than 0.3, the effect of suppressing wear on a dry road surface does not appear, and when it exceeds 0.6, the wear of less than 40% of the land surface exposes the base rubber layer to the surface early. As a result, the exposed performance of the base rubber layer significantly deteriorates the running performance on the snowy and snowy road surface, resulting in a marked reduction in the service life.

Further, the maximum depth HS of the sampling at the deepest position of the siping is from 0.6 to 0.
9 times. If it is less than 0.6 times, the grip force on the ice and snowy road will be insufficient, and the traction force and the braking performance will be poor.
If it exceeds 9 times, the deformation of the land portion becomes large during running and braking, and uneven wear such as heel and toe wear is likely to occur.

Moreover, the siping is a ratio H between the cutting depth HN for cutting the base rubber layer and the siping maximum depth HS.
N / HS is 0.08 or more and 0.3 or less. By thus cutting the bottom of the sipe groove into the base rubber layer, it is possible to prevent the damage from the groove bottom of the sipe as a starting point as described above. The ratio HN / HS
Is less than 0.08, the effect of preventing damage is small, and if it exceeds 0.3, the base rubber layer is greatly deformed during running,
Occurrence of uneven wear increases.

As described above, according to the present invention, the above-mentioned components are organically combined and integrated to maintain the running performance on an ice and snowy road, and at the same time, the wear resistance and the uneven wear resistance on a dry road surface are maintained. It can be raised.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The pneumatic tire 1 includes sidewall portions 3 and 3 extending inward in the tire radial direction from both ends of the tread portion 2.
And the bead portions 4 and 4 located at the inner ends of the sidewall portions 3 and 3 in the radial direction. Further, the pneumatic tire 1 has a toroidal carcass 6 that passes from the tread portion 2 through the sidewall portion 3 and folds back around the bead core 5 of the bead portion 4.
And the tire structure layer 8 including the belt layer 7 on the outer side in the radial direction and on the inner side of the tread portion 2.

The carcass 6 is a so-called radial or semi-radial direction array in which the carcass cords are arranged at an angle of 80 ° to 90 ° with respect to the equator C of the tire in the present embodiment, and a steel cord is used as the carcass cord. In addition, fiber cords such as nylon, polyester, rayon and aromatic polyamide are adopted.

In this embodiment, the belt layer 7 has two belt plies 7a, 7a arranged from the carcass 6 side toward the outer side in the radial direction of the tire.

The belt layer 7 is composed of the respective belt plies 7
In addition to steel, the belt cords are made of nylon, polyester, rayon, aromatic polyamide or the like fiber cords, which are inclined with respect to a and 7a and intersect with each other.

The tire structure layer 8 includes the carcass 6,
In addition to the belt layer 7, a structural member such as a band layer, which is arranged on the outer side in the radial direction of the belt layer 7 and prevents lifting of the belt layer, may be added.

In the present embodiment, the tread portion 2 is provided with grooves 10 formed of five circumferential grooves extending in the circumferential direction. The grooves 10 are provided between the grooves 10 and 10 and between the groove 10 and the tread edge. Six ribs are formed between the ribs and E.

Therefore, the tread portion 2 has an outer surface of the rib,
That is, it is divided into a land surface 12 formed by the outer surface of the tread and a sea surface 13 sandwiched by the groove wall surfaces 11 of the groove 10. In the present embodiment, the grooves 10 have the same groove depth g.

Further, the tire structure layer 8 is provided on the tread portion 2.
A base rubber layer 16 extending along the tire axial direction,
A tread rubber 15 composed of a cap rubber layer 17 extending in the tire axial direction outside the base rubber layer 16 in the radial direction.
Are arranged. Moreover, the cap rubber layer 17 covers the land surface 12 and the groove wall surface 11 of the groove 10.

The base rubber layer 16 is made of rubber harder than the cap rubber layer, and its JISA hardness at 0 ° C. is set in the range of 58 to 68 degrees.

The cap rubber layer 17 is formed according to JIS A at 0 ° C.
The hardness is 50 to 60 degrees and the short fibers are rubber 100.
The rubber composition comprises 2 to 10 parts by weight based on parts by weight. As the short fibers, organic fibers are used. In this embodiment, natural plant fibers such as celco are crushed to 0.074.
To about 0.177.

On the land surface 12, the base rubber layer 16
And the total thickness T of the tread rubber 15 is 0.3 to 0.6. On the other hand, the groove depth g of the groove 10 is formed to be larger than the thickness t2 of the cap rubber layer 17, and therefore the base rubber layer 16 is formed by the cap rubber layer 17 forming the groove wall surface 11. A recess 19 is formed in which 16 is recessed inward.

Further, one end of the land surface 12 has a groove wall surface 11
The sipings 14 ... In the present embodiment, the siping 14 is opened at one groove wall surface 11 of the rib F, the rib extends in the tire axial direction, and the other end is interrupted at an intermediate position of the rib F, and the other groove wall surface of the rib F. The second siping 14 that opens at 11 and extends in the opposite direction to the first siping 14A and is interrupted at an intermediate position of the rib F
B and B are alternately arranged in a zigzag pattern in the tire circumferential direction.

As shown in FIG. 3, the sipings 14 are retained in the cap rubber layer 17 without cutting the siping depth HO in the groove wall surface 11 where the siping 14 is opened into the base rubber layer 16. Groove 1
0 to a position beyond the recess 19 of the base rubber layer 16 in the tire axial direction to increase the siping depth.
Cut into the base rubber layer 16. Further, the maximum siping depth HS at the deepest position of the siping 14 is set to 0.6 to 0.9 times the groove depth g of the groove 10.

Further, the cutting depth HN at which the siping 14 cuts the base rubber layer, that is, the maximum groove depth H of the siping.
The ratio HN / HS of the value obtained by subtracting the thickness t2 of the cap rubber layer from S and the maximum siping depth HS is 0.08 or more and 0.3 or less. The groove width of the siping 14 is preferably 1.5 mm or less and is within a range having no substantial groove width.

In the present invention, a block pattern composed of a large number of blocks may be formed by a groove in which a lateral groove is provided in addition to the circumferential groove in the tread portion, and the siping is opened at both ends with groove wall surfaces. By doing
It can also be formed as a siping connecting the grooves, and the present invention can be modified into various modes.

[0037]

SPECIFIC EXAMPLE For a tire having a tire size of 195 / 65R15 and having the structure shown in FIGS. 1 to 3, tires according to the specifications of Examples 1 and 2 by Test A shown in Table 1 and the groove depth of the above structure and siping. Tires with different lengths (Comparative Examples 1 and 2) were made as prototypes and their performances were compared.

Example 3 according to Test B shown in Table 1
The tires according to the specifications, a tire in which the rubber thickness of the base rubber layer is thin (Comparative Example 3) and a tire in which the hardness of the base rubber layer is low (Comparative Example 4) among the above-described configurations were experimentally manufactured and their performances were compared. .

The test method is the same for both test A and test B, and is based on the following specifications. a) Braking performance test on ice A speedometer, braking distance measuring device, and test tires are attached to the test vehicle, and the vehicle is driven at a constant speed of 40 km / H on the test road surface formed by the ice board and suddenly braked with a four-wheel lock. The braking distance until the vehicle stops is calculated, and the friction coefficient is calculated from each value of the total weight, speed and braking distance of the test vehicle, and displayed as an index with 100 in Comparative Example 2 and Comparative Example 4, respectively. did. The larger the value, the higher the friction coefficient and the better.

B) Snow braking performance test: The vehicle was run on a snowy road surface at a constant speed of 40 km / H, and braking and evaluation were carried out in accordance with the above-mentioned ice braking performance test.

C) Abrasion amount, heel and toe abrasion amount After mounting a test tire on an actual vehicle and running a test course at a speed of 60 km / H with a specified maximum load, the remaining depth of the main groove was measured. The amount of wear was measured and determined. In the test, the tire was grounded in a dry state. The test results are shown in Table 1.

[0042]

[Table 1]

As a result of the test, it was confirmed that in all of the examples, the running performance on snow and ice which is substantially the same as that of the comparative example could be maintained and the abrasion resistance and the uneven abrasion resistance were improved.

[0044]

As described above, the pneumatic tire of the present invention is
By having the above-described structure, it is possible to enhance the wear resistance and uneven wear resistance during running on a dry road surface while maintaining the running performance on an icy and snowy road surface, and it can be suitably used as a snow tire.

[Brief description of drawings]

FIG. 1 is a right half sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is a plan view showing a part of the outer surface of the tread.

FIG. 3 is a sectional view taken along line XX.

[Explanation of symbols]

 2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 7 belt layer 8 tire structure layer 10 groove 11 groove wall surface 12 land part 13 sea part 14, 14A, 14B siping 15 tread rubber 16 base rubber layer 17 cap rubber layer 19 recess HN depth of cut HS maximum depth of siping T tread rubber thickness t1 base rubber layer thickness t2 cap rubber layer thickness

Claims (3)

[Claims] 1. A tire structure layer including a carcass folded back from a tread portion to a sidewall portion at a bead core of a bead portion, and a belt layer arranged radially outside the carcass and inside the tread portion. The groove is formed in the tread portion so as to be divided into a land surface forming an outer surface of the tread and a sea surface sandwiched by the groove wall surfaces of the groove, and extending in the tire axial direction along the tire structure layer in the tread portion. A pneumatic tire in which a tread rubber including an existing base rubber layer and a cap rubber layer that covers the land surface and the groove wall surface by extending in the tire axial direction radially outside the base rubber layer is provided. The base rubber layer is harder than the cap rubber layer and is 0 ° C.
2 to 10 parts by weight of short fibers made of organic fiber material and having a JIS A hardness of 50 to 60 degrees at 0 ° C. in the cap rubber layer. And a ratio t1 / T between the thickness t1 of the base rubber layer on the land surface and the total thickness T of the tread rubber is 0.3 to 0.6, and On the land surface, at least one end is opened at the groove wall surface, and a siping having a depth that cuts the base rubber layer is formed, and the siping maximum depth HS at the deepest position of the siping is the groove depth of the groove. 0.6 to 0.9 times the depth g, and the ratio HN / HS of the cutting depth HN at which the siping cuts the base rubber layer and the siping maximum depth HS is 0.08 or more and 0.3 or less. That Pneumatic tire and butterflies. 2. The base rubber layer, wherein the groove depth g of the groove is larger than the thickness t2 of the cap rubber layer,
2. The pneumatic tire according to claim 1, wherein the cap rubber layer forming the groove wall surface forms a recess inwardly recessing the base rubber layer. 3. The siping has a siping depth on a wall surface of the groove where the siping is open, which is shallower than a depth to a base rubber layer, and extends from the groove to the concave portion of the base rubber layer in the tire axial direction. The pneumatic tire according to claim 2, wherein the siping depth is increased at the open position.