JP2002347413A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance on-ice running performance in the early period of usage with pattern rigidity secured. SOLUTION: A small siping group 12 comprising small sipings 11 whose maximum depth hs is 2 mm or less and both ends of which are broken off on a land section R comprising blocks Rb or rib Rr is provided on the land section R. The small siping group 12 substantially forms a row-shape section 13 which is intermittent in the longitudinal direction with a plurality of the small sipings 11 provided in a line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire suitable as a studless tire and capable of exhibiting excellent on-ice performance from the beginning of use while suppressing a decrease in rigidity of a tread pattern.

[0002]

2. Description of the Related Art In a studless tire, in order to improve performance on ice, it is necessary to increase road digging friction and adhesive friction.
Conventionally, various studies have been made to increase the coefficient of friction of the tread rubber against an icy road surface. As one of them, a technique has been proposed in which a foreign material such as a short fiber or rice hull is mixed into tread rubber, or the rubber is foamed to roughen the tread surface.

However, in a new tire taken out of a vulcanization mold, even when the tread rubber is foamed or foreign matter is mixed, the tread surface tends to be smoothly finished in a mirror-like shape due to the rubber flow during the vulcanization. is there. As a result, there is a problem that the original excellent road surface friction coefficient cannot be exhibited in the early stage of use.

[0004] Therefore, in this type of tire, a running-in run for roughening the tread surface is performed, for example, from 50 to 10 days.
Although it is necessary to perform about 0 km, there is a case where a general consumer has to run without running-in due to sudden snowfall. Therefore, the appearance of a tire capable of exhibiting an excellent road friction coefficient from the beginning of use is strongly desired.

[0005] On the other hand, it is known that by providing sipes on the tread surface, the performance on ice is improved by the edge effect. However, excessive use of siping tends to cause uneven wear such as a significant decrease in pattern rigidity, resulting in a decrease in ground contact area and impaired original performance on ice. Especially at the beginning of use (when new)
However, since the groove is deep, the pattern rigidity is low, which is disadvantageous for uneven wear.

Accordingly, the present invention is based on the fact that small sipes having a maximum depth of 2 mm or less are intermittently arranged in a straight line in a block or a rib, without causing a decrease in pattern rigidity, at the beginning of use. Pneumatic tires that can improve the performance on ice and can exhibit the original excellent performance on ice from the beginning of use by using in combination with the conventional siping technology, the technology of foaming tread rubber and mixing foreign matter, etc. The purpose is to provide.

[0007]

In order to achieve the above object, the invention of claim 1 of the present application is directed to a method in which a land portion formed of blocks or ribs formed on a tread portion extends in a direction intersecting the tire circumferential direction. A small siping group having a maximum depth of 2 mm or less, and small sipings having both ends interrupted in the land portion is provided. In this case, an intermittent row portion is formed.

In the invention according to claim 2, the length La of the small siping is not less than 2 mm and not more than 1/3 times the length Lb of the land portion in the small siping direction.

In the invention of claim 3, the small siping is characterized in that the depth increases from both ends toward the center.

According to a fourth aspect of the present invention, the small siping is characterized in that the depth changes in a curved shape including an arc and a sine.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described.
This will be described together with the illustrated example. FIG. 1 is a meridional sectional view when the pneumatic tire of the present invention is formed as a studless tire, and FIG. 2 is a developed view of the tread pattern.

Referring to FIG. 1, a pneumatic tire 1 (hereinafter referred to as a tire 1) has a carcass 6 extending from a tread portion 2 to a bead core 5 of a bead portion 4 through a sidewall portion 3.
And a belt layer 7 disposed radially outward of the carcass 6 and inside the tread portion 2.

The carcass 6 comprises one or more carcass plies 6A in which carcass cords are arranged at an angle of 75 to 90 degrees with respect to the tire circumferential direction, in this embodiment, one carcass ply 6A. It is folded around and locked. The belt layer 7 includes two or more belt cords, in this example, two belt plies 7A and 7B in which belt cords are arranged at an angle of 10 to 55 degrees with respect to the tire circumferential direction. , A strong truss structure is formed, and the tread portion 2 is reinforced with a tag effect.

In this embodiment, the tread rubber G constituting the tread portion 2 is formed of rubber mixed with foreign matters such as short fibers and rice hulls. When the tread rubber G has a two-layer structure of the cap rubber layer G1 forming the tread surface and the base rubber layer G2 on the radial inside thereof, at least the cap rubber layer G1 is formed of the mixed rubber.

Particularly, the present example illustrates a preferred case in which short fibers are used as the foreign matter and the short fibers are substantially oriented in the tread thickness direction. Since the tread rubber G has short fibers, the ability to excavate and raise the road surface is enhanced, and the softness in the thickness direction following fine irregularities on the road surface can be ensured. Can be greatly improved. However, the tread rubber G has a problem that the short fibers on the surface side have a strong tendency to lie down (along the tread surface) due to the rubber flow at the time of vulcanization, and the function is not achieved in the early stage of use. Therefore, this tread rubber G can be suitably adopted as the most suitable one for the present invention.

As short fibers to be blended, nonmetallic short fibers which do not damage the road surface and have a small difference in abrasion speed with rubber are used in order to ensure excellent grounding properties on icy road surfaces. Indispensable, as this non-metal short fiber, a non-metal short inorganic fiber is preferable. In particular, glass fiber or carbon fiber is preferable in terms of dispersion and orientation, since it is broken into an appropriate length and shortened in the process of kneading rubber. The short fibers have an average fiber diameter of 1 to 100 μm (preferably 3 to 50 μm) and an average fiber length of 0.1 to 5.0 mm (preferably 0.1 to 5.0 mm).
(3.0 mm).

In the tire 1 according to the present embodiment, as shown in FIGS. 2 and 3, a block Rb or a rib R
small sipe 1 extending in a direction intersecting the tire circumferential direction and having a maximum depth hs of 2 mm or less on a land portion R composed of
1 is provided.

In this embodiment, the land R is a block Rb.
In the illustrated example, the land portion R includes a block Rb and a rib Rr.
It may be a block pattern (shown in FIG. 6) or a rib pattern composed of ribs Rr.

Here, the length La of the small siping 11 is smaller than the length Lb of the land portion R in the length direction of the small siping 11, so that both ends are interrupted in the land portion R. ing. The small siping 11 is preferably formed at an angle of 70 to 90 degrees with respect to the tire circumferential direction in order to effectively exert the edge effect.

In the small siping group 12, a plurality of the small sipings 11 are provided substantially in a straight line, so that the small sipings 11 form a row-shaped portion 13 intermittently arranged in the longitudinal direction. ing. In this example, a case is shown in which the small siping group 12 is formed by three row-shaped portions 13 in which three small sipings 11 are arranged on a straight line.

As described above, the maximum depth hs of the small siping 11 is 2 mm or less, both ends of the small siping 11 are interrupted in the land portion R, and the small siping 11 By forming the shape portion 13, it is possible to maximize the total edge length of the small siping group 12 while securing the block rigidity.

If the maximum depth hs is larger than 2 mm and at least one end of the small siping 11 is opened by a groove wall, the rigidity of the block is remarkably reduced, causing uneven wear. Further, when the small siping 11 is formed without forming the row-shaped portions 13, the influence on the block rigidity is large, and the block rigidity decreases when the same total edge length is secured.

Here, the length La of the small siping 11 is preferably 2 mm or more and 1/3 or less of the length Lb of the land portion R. If the length La is less than 2 mm, The small siping 11 cannot effectively exert the edge effect. In order to obtain more edge effects while securing the block rigidity, the number of small sipings 11 in one row-shaped portion 13 should be as large as two or more,
That is, it is preferable that the number is three or more, more preferably four or more,
If the length La is larger than １ ／ times the length Lb of the land portion R, three or more small sipings 11 cannot be expected.

At this time, the distance Ka between the small sipings 11 in one row-shaped portion 13 and the distance Kb between the small sipings 11 on both sides and the wall surface of the land R are determined by the block rigidity, the edge effect, and the like. From the viewpoint of manufacturing damage, 1.0
It is preferable to set the range to 5.0 mm. If it is less than 1.0 mm, the rigidity of the block may be reduced and damage may be caused during manufacturing. Conversely, if it exceeds 5.0 mm, the edge effect becomes insufficient.

Here, the lengths La and Lb, the distance Ka,
Kb and the like are values measured on the tread surface.

As shown in FIG. 4, the small siping 11 is formed such that the depth h is gradually increased from both ends toward the center, and the maximum hs is obtained at the center. preferable. As a result, the edge effect can be effectively exerted while further suppressing a decrease in block rigidity. It also helps to reduce damage during manufacturing. From such a viewpoint, it is particularly preferable that the small siping 11 is formed in a shape in which the depth h is changed into a curved shape including an arc and a sine. FIG. 4 illustrates the case of a sine curve.

Next, in this example, the case where the maximum depths hs of the small sipes 11 are equal to each other in one row-shaped portion 13 is illustrated.
Differences can be made within the following ranges. At this time, FIG.
As shown in (1), in order to secure the block rigidity, it is preferable that the maximum depth hs1 of the small sipes 11 on both outer sides in the tire axial direction be smaller than the maximum depth hs2 of the small sipes 11 therebetween.

Further, a plurality of row-shaped portions 13...
Is provided, the maximum depth hs of the small siping 11 of the row 13 on both outer sides in the tire circumferential direction is set to the row 1
It is preferable to make the smaller than the maximum depth hs of the small siping 11 of No. 3 in order to secure the block rigidity.

Further, in the present embodiment, a conventional siping 15 (shown in FIG. 3) which is deeper and longer than the small siping 11 can be formed between the row-shaped portions 13. The siping 15 is not particularly limited, but usually has a depth H of 0.6 to 1.
An open type in which the length Lc is 0 times and the length Lc is 0.5 times or more of the length Lb and at least one end is opened by a groove wall can be suitably used.

FIG. 6 shows another example of the small siping group 12. In this example, the land portion R is composed of a block Rb and a rib R
In the block Rb and the rib Rr, a row-like portion 13 in which the small sipings 11 are intermittently arranged in a straight line is arranged. Row-shaped part 13
Are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment, but may be implemented in various forms.

[0032]

EXAMPLE A studless tire having a tire size of 195 / 65R15 based on the block pattern of FIG.
Prototypes were manufactured based on the specifications shown in Table 1, and each of the test tires was tested for block rigidity, performance on ice, resistance to uneven wear, and the like. The results are shown in Table 1. In addition, the conventional example, the embodiment,
FIG. 7 shows the state of formation of sipings in Comparative Example and Comparative Example
(A) to (C), and the total edge length s of the siping is indicated by an index with the conventional example being 1.

(1) Block rigidity; internal pressure (200 kP
Using the test tire with the rim assembled in a), the vertical deformation (5.4 kN) and the circumferential load (2.4 kN) were applied to one of the blocks, and the amount of circumferential deformation of the block was observed. Is shown as an index with 100 as the index. The smaller the value, the smaller the deformation and the higher the block rigidity.

(2) Performance on ice; using an indoor ice tray tester,
Friction coefficient when tire is completely locked (lock μ)
Was measured, and indicated by an index with the conventional example being 100. The larger the value, the better the performance on ice. The measurement conditions are as follows. Internal pressure (200kPa), vertical load (3.4k
N), speed (30 km / h), ice surface (-1 ° C. Miller burn). The performance on ice in the conventional example after running-in of 100 km was 115.

(3) Uneven wear resistance: The test tire was mounted on the front wheel (driven wheel) of a vehicle (2000 cc) under the condition of an internal pressure (200 kPa), and on a test course from 90 km / h to 50 km / h. During this period, the block was decelerated every 1500 m (deceleration by 0.45 G), and the heel & toe wear of the block after traveling 500 km was measured.
The index was set to 00. The smaller the value, the lower the uneven wear resistance.

[0036]

[Table 1]

[0037]

As described above, according to the present invention, small sipes having a maximum depth of 2 mm or less are intermittently arranged in a straight line in a block or a rib. The performance on ice at the initial stage can be improved. Therefore, for example, by using in combination with a conventional siping technique, a technique for foaming tread rubber, or a technique for mixing foreign matter, original excellent performance on ice can be exhibited from the beginning of use.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a pneumatic tire of the present invention.

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

FIG. 3 is an enlarged perspective view showing a land portion.

FIG. 4 is a cross-sectional view showing a row of small sipes cut in the length direction.

FIG. 5 is a cross-sectional view showing another example of the row portion of the small siping.

FIG. 6 is a development view showing another example of the tread pattern.

FIGS. 7A to 7C are diagrams showing siping in the test tires used in Table 1. FIG.

[Explanation of symbols]

 2 Tread part 11 Small siping 12 Small siping group 13 Row part R Land part Rb Block Rr Rib

Claims (4)

[Claims] 1. A small siping comprising a small siping extending in a direction intersecting the circumferential direction of the tire and having a maximum depth of 2 mm or less and having both ends interrupted in the land, the land comprising a block or a rib formed on a tread portion. A pneumatic tire, wherein a group is provided, and the small siping group forms a row-shaped portion that is intermittent in a length direction by a plurality of the small sipings being provided substantially on a straight line. 2. The pneumatic tire according to claim 1, wherein a length La of the small siping is not less than 2 mm and not more than １ ／ of a length Lb of the land portion in the small siping direction. 3. The small siping according to claim 1, wherein the depth increases from both ends toward the center.
The pneumatic tire as described. 4. The pneumatic tire according to claim 3, wherein the small siping changes in a curved shape including an arc and a sine.