JPH0781326A - Tire for icy and snowy road - Google Patents

Abstract

PURPOSE:To enhance the stability of traveling on a dry road surface as well as to improve durability by making improvements in block rigidity as keeping the performance of traveling on ice and snow and preventing any crush of a tire block pattern from occurring. CONSTITUTION:This is an ice-and-snow road tire consisting in a block pattern where a block 3 made up as an upper surface forming a tread surface 2 with an upper end of a wall surface 7 rising from a groove bottom surface 6, and in this constitution, tread rubber 10 doubles as a wall surface while it extends into the block from outer cover rubber 15 being interrupted at a peripheral layer 12 forming a peripheral edge 11 of the upper surface 9 and a core part 13 forming an inner part of the peripheral edge 11, including core part rubber 14 being softer than the outer cover rubber 15, and an area Sa of the peripheral edge 11 is limited to 5 to 50% of the total area S of the upper surface 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ice / snow road tire capable of increasing block rigidity and preventing pattern collapse while maintaining running performance on ice and snow.

[0002]

2. Description of the Related Art In recent years, studless tires have been widely used as tires that run on ice and snow.

Such a studless tire has improved running performance on snow by obtaining a shearing force from snow compacted in the groove a as shown in FIG. 5, and a block pattern composed of blocks is formed on the tread surface. is doing.

On the other hand, the block is made of a soft rubber material in order to enhance the adhesive frictional force f with the ice road surface even when traveling on ice.

[0005]

However, in the tire having the above-mentioned structure, the block is softer and has a lower rigidity than the general tire that travels on a normal road surface, so that the wear is caused early and the pattern is crushed. . In particular, this pattern collapse is remarkable when the vehicle is run with a tire chain attached.

Therefore, it is necessary to prevent pattern collapse while maintaining ice / snow running performance even in ice / snow road tires.

It is an object of the present invention to provide a tire for ice and snow roads, which can improve the rigidity of the block and prevent the pattern flow while maintaining the running performance on ice and snow, and the durability and the utilization thereof.

[0008]

DISCLOSURE OF THE INVENTION The present invention is a tire for ice and snow roads having a block pattern in which blocks are arranged so that the upper end of the wall surface rising from the groove bottom surface forms the tread surface, and the tread rubber is the wall surface. And a peripheral rubber portion that forms a peripheral portion of the upper surface and is interrupted by a peripheral layer, and a core portion rubber that extends from the core portion forming the inside of the peripheral portion into the block and is softer than the peripheral rubber portion, and the peripheral portion. Area S
a is a tire for snow and snow roads, which is 5 to 50% of the total area S of the upper surface.

Further, the block is provided on the tread surface,
A main groove having the deepest deepest groove bottom surface among the groove bottom surfaces;
It is preferably formed by a sub-groove having a shallow groove bottom surface having a depth of ⅔ or more and less than 1 time the main groove.

[0010]

Since the tread surface is formed as a block pattern in which the blocks are arranged side by side, the snow running performance is maintained by obtaining a shearing force from snow compacted in the grooves between the blocks.

Further, the tread rubber includes an outer skin rubber forming a peripheral portion of a wall surface and an upper surface of the block, and a core rubber extending from a core portion inside the peripheral portion into the block,
The core rubber is softer than the outer rubber.
Since the soft core rubber is exposed on the upper surface in this way, the adhesive frictional force between the soft core rubber and the icy road surface is increased when traveling on ice, and braking performance on ice, traction performance on ice, etc. I am.

Further, since the wall surface and the peripheral portion of the upper surface of the block are formed by the outer rubber that is harder than the core rubber, the rigidity of the block is higher than that of the conventional tire formed for running on snow and snow roads. , It is possible to secure driving stability when driving on a dry road such as an ordinary road. Moreover, the deformation of the block is slight even when the tire chain is mounted during traveling on snow, and it is possible to prevent deterioration of traveling stability due to pattern collapse and improve durability.

The area Sa of the peripheral portion is 5 to 50 of the total area S of the upper surface as the area distribution of the outer rubber forming the peripheral portion and the core rubber forming the core of the upper surface of the block. The range is%.

The area Sa of the peripheral portion is 5 of the total area S of the upper surface.
If it is less than 50%, the rigidity of the block is insufficient, and the pattern is likely to be crushed. If it exceeds 50%, the performance on ice cannot be maintained.

As described above, according to the present invention, by organically integrating the above-described components, the pattern collapse is prevented while the ice running performance and the snow running performance are maintained, and the running stability during dry road running is improved. And the durability can be improved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 3, the ice and snow road tire 1 is a pneumatic tire in which the tread surface 2 is formed as a block pattern in which blocks 3 are arranged.

The ice / snow road tire 1 has the tread surface 2
Pneumatic tire having sidewall portions 23, 23 extending inward in the tire radial direction from both ends of a tread portion 22 forming a groove, and bead portions 24, 24 located at radially inner ends of the sidewall portions 23, 23. Formed as. Further, in the tire 1 for ice and snow roads, a toroidal carcass 26 that passes from the tread portion 22 through the sidewall portion 23 and folds back around the bead core 25 of the bead portion 24, and is arranged radially outside and inside the tread portion 2. Belt layer 27
And with. In this embodiment, a bead apex 28 is provided between the main body of the carcass 26 and the folded-back portion so as to rise from the bead core 25 outward in the radial direction.

The carcass 26 is composed of one carcass ply in this embodiment, and the carcass ply has a carcass cord of 80 in this embodiment with respect to the equator C of the tire.
A so-called radial or semi-radial direction arrayed sheet body arranged at an angle of 90 ° to 90 ° and covered with a topping rubber, and as a carcass cord, an organic fiber cord such as nylon, polyester, rayon, aromatic polyamide or a steel cord Is adopted.

In this embodiment, the belt layer 27 is composed of three belt plies 27A, 27A and 27A. These belt plies 27A are made of nylon, polyester, rayon, aromatic polyamide or the like organic fiber cord or steel. The cords are arranged so that the plies cross each other.

The tread surface 2 is shown in FIG.
As shown in Figure 4, a central main groove 4A that folds and circulates in a zigzag along the tire equator C, and a pair of main grooves 4B and 4B that are arranged between the tire equator C and the tread edge E and that circulate in a zigzag shape. Are provided with three main grooves 4 ...

Between the main groove 4A at the center and the main groove 4B at the side, there are sub-grooves 5A ... Connecting the main grooves 4A and 4B, and between the main groove 4B at the other side and the tread edge E. Outer sub-grooves 5B ... Are provided between them.

In this way, the main grooves 4 and the inner and outer sub-grooves 5 are formed.
By partitioning the tread surface 2 with the sub-grooves 5 composed of A and 5B, the main grooves 4 are formed on the tread surface 2.
A block pattern in which a plurality of blocks 3 surrounded by the sub-grooves 5 are arranged in the circumferential direction is formed.

Therefore, such a block 3 has a wall surface 7 rising from the groove bottom surface 6A of the main groove 4 and a groove bottom surface 6B of the sub groove 5, and an upper surface 9 having the tread surface 2 at the upper end of the wall surface 7. Equipped with.

The main groove 4 has a tread surface 2 in this example.
The groove depth GH, which is the distance from the groove bottom surface 6A to the groove bottom surface 6A, is 0.07 to 0.16 times the tread width WT, which is the tire axial direction distance between the tread edges E.

Further, in the main groove 4, the main groove 4 and the sub groove 5
While having the deepest groove bottom surface among these groove bottom surfaces 6, the groove bottom surface 6B of the auxiliary groove 5 is not less than ⅔ times and not more than 1 time the depth of the groove bottom surface 6A of the main groove 4. It is formed as a shallow groove bottom having a depth of.

If the groove bottom surface 6B of the auxiliary groove 5 is less than ⅔ times the deepest groove bottom surface of the main groove 4, the grip force will decrease during running on snow, and the traction performance and braking performance will be poor.
If it exceeds 1 times, the rigidity of the block 3 is lowered, the steering stability on the dry road surface is deteriorated, and the peripheral portion 11 of the block 3 is deteriorated.
The durability is reduced due to uneven wear.

In the tread portion 22, the tread rubber 10 forming the tread surface 2 on the outer side in the radial direction of the belt layer 27 is arranged.

The tread rubber 10 includes a base rubber 16 disposed adjacent to the belt layer 27 and the base rubber 1
It is formed by three rubber layers, namely, a core rubber 14 arranged on the outer side in the radial direction of 6 and covering the base rubber 16, and an outer rubber 15 forming the wall surface 7.

The base rubber 16 has a JISA hardness of 67-
It is made of a hard rubber composition of 80 ° and maintains the rigidity of the tread portion 22 which is repeatedly bent when the tire touches the ground. In addition, the core rubber 14 is JIS A in this embodiment.
The outer rubber 15 is formed of a hard rubber having a JISA hardness of 67 to 85 [deg.], While the soft rubber having a hardness of 55 to 64 [deg.]. Therefore, the core rubber 14 is formed softer than the outer rubber 15.

The outer rubber 15 has a JIS A hardness of 67 °.
If it is less than the above range, the rigidity of the block 3 is insufficient, and as described above, the pattern is likely to be crushed.

In the block 3, the outer rubber 15
Forms the wall surface 7 of the block 3 and is interrupted by the peripheral layer 12 forming the peripheral edge portion 11 of the upper surface 9 thereof.

In the block 3, a core rubber 14 is formed between the core 13 located inside the peripheral edge 11 on the upper surface 9 and extending to the base rubber 16 in the block.

The rubber composition of the tread rubber 10 in the block 3 is, for example, raw tread rubber before vulcanization molding from bottom to top, the base rubber 16 and the core rubber 1.
4. The outer rubber layer 15 is overlaid in this order, and a tread pattern is formed by vulcanization molding using a full mold. At this stage, the upper surface 9 of the block 3 is covered with the outer rubber layer 15 as shown by the one-dot chain line in FIG.

As described above, after the vulcanization molding, the upper surface 9 is buffed and scraped off, as shown in FIG.
As shown by the solid line, the core rubber 14 can be exposed on the upper surface 9.

As another method for removing the outer skin rubber 15 remaining on the core portion 13 of the upper surface 9 during molding and vulcanization, a new tire is mounted on the vehicle and the tire is acclimated for running, thereby It can also be removed by abrasion. By the way, tires for ice and snow roads are usually mounted on the vehicle one to two months prior to the full-fledged snow season or freezing season, and run on a dry road surface. Since the vehicle runs, it is possible to secure a sufficient period for performing the above-mentioned running.

The groove width of each of the main groove 4 and the sub groove 5 is preferably at least 2 mm or more. If it is less than 2 mm, there is a risk that the outer rubber forming the wall surface 7 may be split when the block 3 is press-molded by the vulcanization mold, and the outer rubber 15 may not cover the entire wall surface.

In the core portion 13 of the block 3, the rubber thickness TS of the core rubber 14 is 0.degree. Of the main groove depth GH which is a radial distance from the upper surface 9 to the groove bottom surface 6A of the main groove 4.
It is preferably 55 times or more and 1.0 times or less. This is to maintain the running performance on ice up to the 1/2 groove depth which is the wear limit of the tread surface 2.

[0038]

【Concrete example】

A) Test 1 For a tire having a tire size of 10.00R20 and having the configuration shown in FIGS. 1 and 2, the area Sa of the peripheral portion made of the outer rubber 15 with respect to the total area S of the upper surface of the block is Sa.
The change in the friction coefficient during braking on ice was investigated by varying the ratio Sa / S of.

The test was conducted in the following manner. Measurement of friction coefficient during braking on ice After mounting a test tire on an actual vehicle and running for 20,000 km, a speedometer and a braking distance measuring device were attached to this vehicle, and the test road surface formed by the ice sheet was fixed at 30 km / H. The vehicle was driven at a speed, and sudden braking was applied with a four-wheel lock, the braking distance until the vehicle stopped was measured, and the friction coefficient was calculated from the total weight of the vehicle, the speed, and the braking distance.

The test results are shown in the graph of FIG. In the graph, the ratio Sa / S is 0, that is, an index is set to 100 when the upper surface S is entirely made of a core rubber, and the larger the value, the larger the friction coefficient.

B) Test 2 For a tire of the same size as in Test 1, the ratio Sa /
S of 10% (Example 1) and ratio Sa / S of 30%
(Example 2) Sa / S of 50% (Example 3) was investigated for braking performance on ice, traveling on snow and pattern collapse. Tests were also carried out on a conventional tire having a conventional structure in which no outer rubber is provided, and a tire having a ratio Sa / S of 2% (Comparative Example 1) and a tire having a Sa / S ratio of 60% (Comparative Example 2). The performance was compared. The test method is as follows

1) Performance on ice The friction coefficient of each sample tire was measured in the same manner as in Test 1 and expressed as an index with the conventional example being 100. The larger the value, the larger the friction coefficient.

2) Snow-braking test The vehicle was run on a snow-covered road surface at a constant speed of 40 km / H, braked and evaluated according to the above-mentioned ice-braking test.

3) Collapse of pattern A tire chain was wound around each test tire mounted on an actual vehicle, and after traveling 100 km on an ice or snow road surface, the tread surface was visually inspected. The test results are shown in Table 1.

[0045]

[Table 1]

[0046]

As described above, the ice and snow road tire of the present invention is
The wall surface and the peripheral portion of the upper surface of the block are formed of outer rubber, and the inner core portion of the peripheral portion is formed of a core rubber softer than the outer rubber, and the peripheral area is 5 times the total area of the upper surface.
Since it is set to -50%, while maintaining the ice running performance and snow running performance, it prevents pattern collapse, especially block deformation due to tire chain installation, enhances stable running on dry road surface and improves durability To do.

[Brief description of drawings]

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

FIG. 2 is a developed plan view showing the tread pattern.

FIG. 3A is an end view of the block taken along line XX,
(B) is the perspective view.

FIG. 4 is a graph showing the relationship between the area ratio of the peripheral portion of the upper surface and the friction coefficient.

FIG. 5 is a front view showing an operation when traveling on snow.

FIG. 6 is a front view showing the operation when traveling on ice.

[Explanation of symbols]

 2 tread surface 3 block 4, 4A, 4B main groove 5, 5A, 5B auxiliary groove 6, 6A, 6B groove bottom surface 7 wall surface 9 upper surface 10 tread rubber 11 peripheral portion 12 peripheral layer 13 core portion 14 core rubber 15 outer rubber Sa Area of peripheral part S Total area of upper surface

Claims (2)

[Claims] 1. A tire for ice and snow roads having a block pattern in which the upper end of the wall surface rising from the bottom of the groove forms an upper surface which forms a tread surface, in which blocks are arranged, and the tread rubber forms the wall surface and a peripheral edge of the upper surface. The outer peripheral surface of the peripheral portion forming a part, and the outer peripheral rubber, and a core rubber that extends from the inner portion of the peripheral portion into the block and is softer than the outer peripheral rubber. 5 of the total area S
A tire for ice and snow roads, which is 50%. 2. A main groove having a deepest deepest groove bottom surface among the groove bottom surfaces on the tread surface, and a depth of 2/3 times or more and less than 1 time the main groove. The ice and snow road tire according to claim 1, wherein the tire is formed by providing an auxiliary groove having a shallow groove bottom surface.