JP2892914B2 - Pneumatic tire - Google Patents

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 abrasion resistance and uneven wear resistance when traveling on a dry road surface while maintaining traveling performance on ice and snowy road surfaces.

[0002]

2. Description of the Related Art For example, vehicles running in cold and snowy areas such as the Hokkaido and Tohoku regions use spike tires in winter to run on snowy roads.

[0003] Such a spiked tire has a feature that when running on a snowy road, the spike digs into the snow to improve grip performance and improve running stability. On the other hand, when running on a dry road surface without snow, the spike causes the spike. The road surface is scraped off to reduce steering stability, such as the formation of ruts, and dust is generated by shaving the road surface.

In order to solve such problems, so-called studless tires having no protrusion on the tread surface and generating no dust are being used. The studless tire improves grip by reducing 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
It is often the case that a user wears a vehicle one or two months or more before full-scale snowfall, and thus may run on a dry road surface without snowfall.

[0006]

However, when driving on a dry road, the above-mentioned studless tires
There is a problem that the tread portion is rapidly worn or unevenly worn, and significantly deteriorates durability.

In order to solve one of the problems, (a) the depth of the siping is reduced. (B) Changing the siping interval. (C) Increase the block rigidity. Although proposals have been made to achieve both running performance on ice and snowy roads and maintaining abrasion resistance through such methods as described above, in (a), the tire appearance after being worn 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, and it is troublesome to replace the tire. Also, if the direction is wrong, the tire performance is significantly impaired. In addition, the method (c) is not practical because the running performance on snow is reduced.

Further, Japanese Patent Publication No. 62-28001 proposes to form a tread using an elastomeric material having pores, but also does not sufficiently improve the running performance in ice and snow.

As a result of repeated studies to solve the above problems, the inventors have found that two layers of tread rubber, a hard base rubber layer on the inside, and soft short fibers made of organic fibers on the outside. By disposing a cap rubber layer made of a mixed rubber composition, and further cutting the siping down to the base rubber layer at its deepest position, it was dried while maintaining running performance on ice and snow roads in winter. It has been found that abrasion resistance and uneven wear resistance can be enhanced with respect to traveling on a road surface.

An object of the present invention is to provide a pneumatic tire having improved abrasion resistance and uneven abrasion resistance against running on a dry road surface while maintaining running performance on icy and snowy roads, particularly braking performance on icy and snowy roads.

[0012]

SUMMARY OF THE INVENTION The present invention is directed to a carcass that is folded from a tread portion to a sidewall portion at a bead core of a bead portion, and a belt layer disposed radially outward of the carcass and inward of the tread portion. And a tire structure layer which is divided into a land surface forming an outer surface of the tread by forming a groove in the tread portion and a sea surface sandwiched by groove wall surfaces of the groove, and a tire structure layer is provided on the tread portion. A tread rubber comprising a base rubber layer extending in the tire axial direction along with the base rubber layer, and a cap rubber layer covering the land surface and the groove wall surface by extending in the tire axial direction on the radially outer side of the base rubber layer. The base rubber layer is harder than the cap rubber layer and has a J
The ISA hardness is made of rubber having a hardness of 58 to 68 degrees, and the cap rubber layer is made of a short fiber made of an organic fiber material having a JISA hardness of 50 to 60 degrees at 0 ° C.
10% by weight of the rubber composition, and the ratio t1 / T of the thickness t1 of the base rubber layer on the land surface to the total thickness T of the tread rubber is 0.3 to 0.6. ,
Moreover, at the land surface, at least one end is formed on the groove wall surface and a siping having a depth for cutting the base rubber layer is formed, and the maximum siping depth HS at the deepest position of the siping is determined by 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 maximum siping depth HS
A ratio HN / HS of 0.08 or more and 0.3 or less.

[0013]

The tread rubber is formed by a cap rubber layer and a cap rubber layer disposed radially outside the cap rubber layer.
The base rubber layer is formed of rubber having a JISA hardness at 0 ° C. of 58 to 68 degrees.

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, occurrence of uneven wear can be effectively suppressed. Further, by positioning the groove bottom of the siping in the base rubber layer, the breaking force generated at the groove bottom can be reduced, so that the generation and growth of cracks are suppressed, and the tread is damaged starting from the groove bottom of the siping. Can be prevented.

When the rubber hardness is less than the JISA hardness of 58 degrees, dynamic strain is not reduced and uneven wear is apt to occur. On the other hand, when the angle exceeds 68 degrees, the dimensional accuracy is not stable and the rubber thickness is not stable in manufacturing.

The cap rubber layer is formed using a rubber composition whose rubber has a JISA hardness of 50 to 60 degrees. 5
If the angle is less than 0 degree, the land surface forming the outer surface of the tread is soft and ordinary wear increases, resulting in poor durability. On the other hand, when the angle exceeds 60 degrees, the grip force decreases when traveling on ice and snow roads,
This leads to a decrease in traction performance and braking performance.

Further, the cap rubber layer is formed using a rubber composition in which short fibers composed of organic fibers are blended in a ratio of 2 to 10 parts by weight with respect to 100 parts by weight of rubber. By blending such short fibers, it is possible to prevent cutting of the land surface due to stone biting etc. when driving on a dry road surface while increasing the strength. The unevenness is formed, and the gripping effect and the braking performance are improved by enhancing the edge effect on the icy and snowy road surface. If the blending ratio of the short fibers is less than 2 parts by weight, the unevenness generated on the land surface is small and the edge effect is not exhibited. If it is added in a large amount exceeding 10 parts by weight, the reinforcing property of the rubber is reduced and the wear resistance is poor.

The ratio t1 / T of the thickness t1 of the base rubber on the land surface to the total thickness T of the tread rubber is 0.3 to 0.6.
And 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 base rubber layer is exposed to the surface early due to wear of less than 40% of the land surface. As a result, the running performance on ice and snow road surfaces is significantly reduced due to the exposure of the base rubber layer, so that the service life is significantly shortened.

Further, the maximum depth HS of the sampling at the deepest position of the siping is 0.6 to 0.1 of the groove depth g of the groove.
Nine times. If it is less than 0.6 times, the grip force on ice and snowy roads is insufficient, and the traction and braking performance are inferior.
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 tends to occur.

Further, the siping is performed at a ratio H between the cutting depth HN for cutting the base rubber layer and the maximum siping depth HS.
N / HS is set to 0.08 or more and 0.3 or less. By cutting the groove bottom of the siping into the base rubber layer in this way, it is possible to prevent the damage originating from the groove bottom of the siping as described above. The ratio HN / HS
If less than 0.08, the effect of preventing damage is small, and if more than 0.3, the base rubber layer is greatly deformed during running,
The occurrence of uneven wear increases.

As described above, according to the present invention, the above-mentioned components are organically combined with each other and integrated to provide abrasion resistance and uneven wear resistance on a dry road surface while maintaining running performance on icy and snowy roads. It can be raised.

[0022]

An embodiment of the present invention will be described below with reference to the drawings. The pneumatic tire 1 has sidewall portions 3, 3 extending inward in the tire radial direction from both ends of the tread portion 2.
And bead portions 4 and 4 located at radially inner ends of the sidewall portions 3 and 3. Further, the pneumatic tire 1 has a toroidal carcass 6 that is folded from the tread portion 2 through the sidewall portion 3 and around the bead core 5 of the bead portion 4.
And a tire structure layer 8 including a belt layer 7 radially outward and inside the tread portion 2.

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

In the present embodiment, the belt layer 7 is provided with two belt plies 7a, 7a from the carcass 6 side to the radial outside of the tire.

Each of the belt layers 7 is composed of a respective one of the belt plies 7.
a and 7a are provided with belt cords which are inclined and cross each other. As the belt cords, fiber cords such as nylon, polyester, rayon and aromatic polyamide are used in the same manner as the carcass 6.

The tire structure layer 8 includes the carcass 6,
In addition to the belt layer 7, a structural member such as a band layer disposed radially outside the belt layer 7 to prevent lifting of the belt layer may be added.

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

Therefore, the tread portion 2 is formed on the 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 surface 11 of the groove 10. In the present embodiment, the grooves 10 have substantially the same groove depth g.

The tread portion 2 includes the tire structure layer 8
A base rubber layer 16 extending in the tire axial direction along
A tread rubber 15 comprising a cap rubber layer 17 extending in the tire axial direction outside the base rubber layer 16 in the radial direction.
Is 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 a rubber harder than the cap rubber layer, and has a JISA hardness at 0 ° C. in the range of 58 to 68 degrees.

The cap rubber layer 17 is made of JIS at 0 ° C.
The hardness is set to 50 to 60 degrees and the short fibers are made of rubber 100.
It consists of a rubber composition in which 2 to 10 parts by weight are blended with respect to parts by weight. As the short fibers, organic fibers are used. In this example, natural plant fibers such as Celco are pulverized to 0.074.
About 0.177.

In the land surface 12, the base rubber layer 16
Of the tread rubber 15 and the total thickness T of the tread rubber 15 are set to 0.3 to 0.6. On the other hand, the groove depth g of the groove 10 is formed larger than the thickness t2 of the cap rubber layer 17 .
Therefore , the cap rubber layer 17 has a height of the thickness t2.
Thin groove wall surface that forms the groove wall surface 11 on the radial inside from the
And the base rubber layer 16
A recess 19 in which the base rubber layer 16 is recessed inward is formed by the groove wall surface forming portion .

Further, one end of the land surface 12 has a groove wall surface 11.
Are provided. In this embodiment, the siping 14 is opened at one groove wall 11 of the rib F, 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 of the rib F. 11, a second siping 14 which opens in the opposite direction to the first siping 14A and is interrupted at an intermediate position of the rib F.
B are alternately arranged in the tire circumferential direction in a staggered manner.

As shown in FIG. 3, these sipings 14 remain in the cap rubber layer 17 without cutting the siping depth HO of the groove wall surfaces 11 where the sipings 14 open into the base rubber layer 16. Groove 1
0, the siping depth is increased at a position beyond the concave portion 19 of the base rubber layer 16 in the tire axial direction.
Is cut into the base rubber layer 16. The maximum depth HS of the sipe at the deepest position of the sipe 14 is set to 0.6 to 0.9 times the groove depth g of the groove 10. Here, Tre
In the wear stage in which the rubber 15 is worn by the thickness t2,
On the ground, the base rubber layer 16 and rubber
The portion where the groove wall surface is formed by the rubber band 17 is exposed.
At this time, due to the difference in wear due to the difference in rubber hardness,
Uneven wear occurs around the groove, which is the groove wall forming portion. Special
The siping crosses the groove wall forming portion
When an opening is made, the rigidity near this opening is further reduced.
Therefore, the groove wall surface forming portion is soft,
Thus, uneven wear near the opening is promoted. Against this
However, the siping 14 of the present application has a thickness smaller than the thickness t2.
It has a shallow part that opens with an iping depth HO
Therefore, this shallow portion is exposed before the base rubber layer 16 is exposed.
It runs away and can close the opening on the groove wall 11
Thus, a decrease in rigidity due to the opening can be prevented. Only
Also, the soft groove wall forming part is a rubber composition containing short fibers
Consists of a hard base rubber layer with improved wear resistance
16 is also reduced. And these synergies
The effect further reduces uneven wear near the opening.
Can be suppressed.

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 between the value obtained by subtracting the thickness t2 of the cap rubber layer from S and the maximum siping depth HS is set to 0.08 or more and 0.3 or less. It is preferable that the groove width of the siping 14 is 1.5 mm or less and 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 grooves formed by providing lateral grooves in addition to the circumferential grooves in the tread portion. By doing
It can also be formed as a siping connecting the grooves, and the present invention can be modified into various forms.

[0037]

[Specific Examples] For tires having a tire size of 195 / 65R15 and having a configuration shown in FIGS. 1 to 3, tires having specifications of Examples 1 and 2 according to Test A shown in Table 1 and a groove depth of the above configuration and siping. Tires having different sizes (Comparative Examples 1 and 2) were each prototyped, and the performance was compared.

Example 3 by Test B shown in Table 1
And a tire with the base rubber layer having a reduced rubber thickness (Comparative Example 3) and a tire with a reduced base rubber layer hardness (Comparative Example 4) were tested and performance was compared. .

The test method is the same for Test A and Test B, and conforms to the following specifications. a) Braking performance test on ice A test vehicle was equipped with a speedometer, a braking distance measuring device, and test tires. The vehicle was driven at a constant speed of 40 km / H on the test road surface formed by the ice floe. To measure the braking distance until the vehicle stops, calculate the coefficient of friction from each value of the total weight, speed, and braking distance of the test vehicle, and display it as an index with Comparative Example 2 and Comparative Example 4 each being 100. did. The larger the value, the higher the friction coefficient and the better.

B) Snow braking performance test A snow-covered road surface was run at a constant speed of 40 km / H, and braking was evaluated according to the above-mentioned ice braking performance test.

C) Abrasion amount, heel and toe abrasion amount A test tire was mounted on an actual vehicle, a specified maximum load was applied, the test course was run at a speed of 60 km / H, and the remaining depth of the main groove was measured. Measurement was performed to determine the amount of wear. In the test, the grounding of the tire was performed in a dry state. Table 1 shows the test results.

[0042]

[Table 1]

As a result of the tests, it was confirmed that all of the examples can maintain the running performance on ice and snow which is almost equivalent to that of the comparative example, and that the wear resistance and the uneven wear resistance are improved.

[0044]

As described above, the pneumatic tire of the present invention has the following features.
By having the above-described configuration, the wear resistance and uneven wear resistance when traveling on a dry road surface can be enhanced while maintaining the traveling performance on an icy and snowy road surface, and the tire can be suitably used as a snow tire.

[Brief description of the drawings]

FIG. 1 is a right half sectional view of a tire showing one 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 of FIG.

[Explanation of symbols]

 2 Tread part 3 Side wall 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 siping maximum depth T tread rubber thickness t1 base rubber layer thickness t2 cap rubber layer thickness

Continuation of the front page (51) Int.Cl. ⁶ identification code FI B60C 11/24 B60C 11/24 Z (58) Investigation field (Int.Cl. ⁶ , DB name) B60C 11/00-11/24 B60C 1 / 00

Claims (1)

(57) [Claims] 1. A tire structure layer comprising a carcass folded from a tread portion to a sidewall portion at a bead core of a bead portion, and a belt layer disposed radially outward of the carcass and inward of the tread portion. By forming a groove in the tread portion, a land surface forming an outer surface of the tread is divided into a land surface forming an outer surface of the tread, and a sea surface sandwiched by groove wall surfaces of the groove, and the tread portion extends in the tire axial direction along the tire structure layer. A pneumatic tire provided with a tread rubber comprising a base rubber layer present and a cap rubber layer covering the land surface and a groove wall surface by extending in a tire axial direction on a radially outer side of the base rubber layer. The base rubber layer is harder than the cap rubber layer and has a thickness of 0%.
JISA hardness of at ℃ consists of 58 to 68 degrees of rubber, tooth
The thickness t1 of the base rubber layer on the land surface and the tread
The ratio t1 / T to the total thickness T of the rubber is 0.3 to 0.6.
And, the cap rubber layer 50 is JISA hardness at 0 ℃
The short fibers of 60 degrees and an organic fibrous material, Ri Na <br/> from rubber compositions containing 2-10 parts by weight per 100 parts by weight of rubber, moreover thickness at the land surface of the cap rubber layer T2
Is smaller than the groove depth g of the groove,
The rubber layer is radially inward from the height position of the thickness t2.
And a groove wall forming portion that forms the groove wall on the side.
Moni, the land surface has at least one end the groove wall surface at an opening to Lusa <br/> Ipingu, yet this siping, the thickness of the cap rubber layer
Having a maximum siping depth HS greater than t2.
And the depth of the deep bottom
Siping connected to the bottom and smaller than the thickness t2
A shallow portion having a depth HO and opening at the groove wall surface
Comprising the sipes maximum depth HS is 0.6 before Kimizo depth g
0.9 times, and the ratio HN / HS between the cutting depth HN at which the siping cuts the base rubber layer and the maximum siping depth HS.
Is not less than 0.08 and not more than 0.3 , and the base rubber layer is abraded by the cap rubber layer.
Prior to exposure, the siping was
A pneumatic tire that is worn and closes an opening in a groove wall .