JPH07172113A - Studless tire - Google Patents

Abstract

PURPOSE:To provide a studless tire having remarkably improved deep snow traveling performance without deteriorating on-ice traveling performance of a conventional studless tire. CONSTITUTION:A studless tire 1 has a plurality of blocks divided by main grooves 20 extending toward a tire circumferential direction and lateral grooves 40 extending toward the tire lateral direction and formed sipes 50 extending to a tire lateral direction in the block 10. Negative ratio is 36-40% and side wall angle theta of a tread aperture of the main groove is in the range of 15 deg.-25 deg.. The sipe 50 is paired up and the block 10 is divided into a narrow area 12 between the sipes and wide areas 14 positioned on both sides of the narrow area through the sipes 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a studless tire,
In particular, the present invention relates to a studless tire for heavy-duty vehicles such as trucks and buses, and provides a pattern for significantly improving the snowability.

[0002]

2. Description of the Related Art Studless tires have a large groove area to enhance the effect of stepping on snow in order to improve the running performance on snow, while a large ground contact area is required to improve the running performance on ice. At the same time, a large number of sipes are formed on the block of the tire tread to remove the water film by the edge effect. The conventional heavy load studless tire shown in FIG. 4 has a groove ratio of 32 to 32 in order to secure both the conventional snow running performance and ice running performance.
The groove side wall inclination angle of the main groove extending in the circumferential direction was set to 13 ° or less.

[0003]

When such a conventional studless tire as described above is used especially in a deep snow region, the negative ratio is insufficient and the effect of stepping on the snow coming out of the contact surface is insufficient, It was found that there is a problem that the snow is not discharged because the groove is clogged even if it is separated from the ground, and as a result, the deep snow running performance is not sufficiently exhibited. In order to improve the running performance on deep snow, it is sufficient to increase the volume of the groove, that is, the negative ratio, but if the negative ratio is too large, the ground contact area decreases and the running performance on ice deteriorates. The present invention is
It is an object of the present invention to provide a studless tire having a drastically improved running performance on deep snow without deteriorating the running performance on ice of a conventional studless tie.

[0004]

Therefore, the present invention has a plurality of blocks defined by a main groove extending in the tire circumferential direction and a lateral groove extending in the tire width direction, and a sipe extending in the tire width direction is formed in the block. In the studless tire described above, the negative ratio is 36 to 40%, the sidewall angle of the tread opening of the main groove is in the range of 15 ° to 25 °, and two sipes form one set, and the block is placed between the sipes. It is characterized in that it is divided into a narrow region to be sandwiched and a wide region located on both sides of the narrow region via the sipes.

[0005]

FIG. 5 is a diagram showing the relationship between the negative ratio and the snow performance and ice performance. The point Q indicates the conventional tire, and the performance on snow and the performance on ice change as indicated by the chain double-dashed line as the negative ratio increases and decreases.
Here, when the negative ratio becomes large, the performance on ice deteriorates, and particularly when it exceeds 40%, it rapidly deteriorates. On the other hand, the smaller the negative ratio, the better the performance on ice. The inventors have studied to significantly improve the performance on snow without deteriorating the performance on ice, and as a result, by providing the block with a pair of two sipes, a negative ratio of 36 to 40 is obtained.
%, The performance on ice will not deteriorate compared to conventional tires (dashed line), and the sidewall angle of the main groove will be increased to further improve snow performance (solid line).
I found out.

That is, since the negative ratio is set to 36 to 40%, which is larger than the conventional value, the effect of compacting snow on the ground contact surface is improved, and the groove wall angle at the tread opening of the groove is set to 15 ° to 25 °. By doing so, it is possible to improve the deep snow traveling property by the interaction thereof without causing snow clogging when leaving the ground contact surface. further,
With a pair of sipes, a narrow region where the block is sandwiched between the sipes and a wide region located on both sides of the narrow region through the sipes are divided, so that the narrow region has low rigidity. 12 deforms due to the frictional force from the road surface due to traveling, and the edge is pressed against the ice surface, so the ice surface is slightly scraped off. Then, the wide area 14 having high rigidity is placed on the newly appearing fresh ice surface, and the friction coefficient is increased. In this way, the traveling performance on ice can be ensured even if the negative ratio becomes large.

If the negative ratio is less than 36%,
If the snow running performance is not sufficiently exerted and conversely exceeds 40%, the snow running performance improves, but the running performance on ice rapidly deteriorates. If the groove wall angle of the tread opening of the main groove is less than 15 °, snow jam tends to occur, and if it is 25 ° or more, the effect of stepping on the snow is rather reduced, and the edges do not act on the snow surface to reduce the skidability. As a result, the traveling performance on snow is reduced.

[0008]

Embodiments of the present invention will be described with reference to FIGS.

The studless tire 1 according to the present invention shown in FIG. 1 has a block pattern. The block 10 has three main grooves 20 extending in a zigzag shape in the tire circumferential direction, and sub-grooves 30 extending in a zigzag shape between the main grooves 20.
The sub groove 32 extends in a zigzag shape between the main groove 20 and the tread end, and the lateral groove 40 extends linearly in the tire width direction.

Here, the negative ratio of the tire 1 is 36 to
The range is set to 40%, and in this embodiment 38%
Is. Further, in the main groove 20, as shown in FIG. 2, the sidewall angle θ of the tread opening 22 is set in the range of 15 ° to 25 °, which is 18 ° in this embodiment. Thereby, snow jam can be prevented and the performance on snow can be improved.

Here, at least three main grooves 20 are preferably provided in order to improve snow performance, and the width w1 of the tread opening is preferably in the range of 8 to 15 mm. In this example, the width w1 is 12 mm. The depth d1 of the main groove is 15
It is preferably not less than mm and 20 mm in this embodiment. The width w2 of the sub groove 30 is 4 mm, the width w3 of the sub groove 32 is 1 mm, and the depth d2 is 30 to 80% of the depth d1 of the main groove.
In this embodiment, both are 10 mm. Lateral groove 4
A width of 0 mm is preferably 7 mm or more in order to improve the performance on snow. In this embodiment, the width is 10 mm, and the depth d3 is 30 to 80% of the depth d1 of the main groove 20.
Is.

Also, in this embodiment, the main groove 20 is provided with a bent portion P and has a two-step shape. The side wall of the bottom portion 24 below the bent portion is substantially perpendicular to the tread surface.
In this case, the bent portion is 30 to 70% of the groove depth d1 from the groove bottom.
It is preferable to be in the position. Thus, by forming the main groove 20 into a two-step shape having the opening 22 and the bottom 24, the groove depth is deepened to maintain the wear life, prevent groove bottom cracks, and prevent snow clogging. can do. That is, when a single groove is formed within the above angle range, the groove becomes shallow and wear resistance is poor, or the radius of curvature of the groove bottom cannot be made large, and groove bottom cracking is likely to occur.

The block 10 has two sipes 5 each.
0s are provided in parallel to each other in the tire width direction, and divide the narrow region 12 sandwiched by the sipes 50 and the wide regions 14 located on both sides of the narrow region 12 through the sipes 50 in the circumferential direction. . FIG. 3 shows a cross-sectional view seen from the width direction of the block. Here, the width t of the sipe 50 is 1.2 mm or less, and is 0.6 mm in this embodiment. The depth D of the sipe is preferably 0.3 to 0.8 times the depth d1 of the main groove, and is 10 mm in this embodiment. An enlarged portion 52 is formed at the bottom of the sipe 50. The radius of curvature R of the enlarged portion 52 is preferably 0.5 mm to 3 mm in order to prevent sipe bottom cracks, but is 1.5 mm in this embodiment.

As described above, the sipe 50 is divided into the narrow region 12 sandwiched by the sipe 50 and the wide regions 14 located on both sides of the narrow region 12 with the sipe 50 interposed therebetween. The narrow area 12 is deformed by the frictional force from the road surface due to traveling, and the edge is pressed against the ice surface, so that the ice surface is slightly scraped off. Then, the wide area 14 having high rigidity is placed on the newly appearing fresh ice surface, and the friction coefficient is increased. Ratio TS of the circumferential width TS of the narrow region 12 to the circumferential width TL of the wide region 14
/ TL is 0.05 to 0.8, preferably 0.1 to 0.5
The range is good. In this way, good performance on ice can be achieved despite a large negative ratio.

Further, in this embodiment, the side wall angle of the lateral groove 40 is 10 ° and has no bent portion, but like the main groove, the side wall angle is set within the negative ratio of 36 to 40%. It may be set in a range of 15 ° to 25 °, which can further prevent snow jam.

(Test Example) A comparative test of the invention tire, the conventional tire, and the comparative tire with respect to the deep snow running performance and the ice running performance will be described below. The invention tire is a tire having the tread pattern shown in FIG. 1 described in the examples, and the conventional tire has a negative ratio of 33 shown in FIG.
% Tires and comparative tires have the same tread pattern as in FIG.
The tire has a negative ratio of 42% and a sidewall angle of the tread opening of the main groove of 27 °. The tire sizes are all 11R22.5.

The test tires were each filled with a specified internal pressure and mounted on all wheels of a 10-ton truck with a constant load. For the deep snow running property, a sudden brake was applied while running 30 km / h on compressed snow, and its position The distance from to the stop position was measured and the reciprocal thereof was taken. Regarding the runnability on ice, a rapid break was applied while running on ice at -5 ° for 20 km / h, the distance from that position to the stop position was measured, and the reciprocal thereof was taken. The results of these tests are shown in Table 1 by using an index display (the larger the value, the better) with the conventional tire being 100.

[0018]

[Table 1]

From the results shown in Table 1, the comparative tire having a large negative ratio is excellent in running on deep snow, but the running on ice is significantly deteriorated. On the other hand, it has been revealed that the tire of the present invention has excellent running performance on deep ice while maintaining good running performance on ice.

[0020]

Since the studless tire of the present invention has the above-mentioned structure, it has an effect of significantly improving the running performance on deep snow without impairing the running performance on ice which the conventional studless tie or the like has.

[Brief description of drawings]

FIG. 1 is a tread pattern of a studless tire of the present invention.
FIG.

FIG. 2 is a cross-sectional view of the main groove of the studless tire of the present invention (AA in FIG. 1).

FIG. 3 is a cross-sectional view (BB of FIG. 1) seen from the width direction of the block of the studless tire of the present invention.

FIG. 4 is a view showing a tread pattern of a conventional studless tire.

FIG. 5 is a diagram showing a relationship between a negative ratio and performance on snow and performance on ice.

[Explanation of reference numerals] 1 studless tire 10 block 12 narrow region 14 wide region 20 main groove P bent portion 22 opening 24 bottom portion 30, 32 auxiliary groove 40 lateral groove 50 sipe 52 enlarged portion

Claims (1)

[Claims] 1. A plurality of blocks defined by a main groove extending in a tire circumferential direction and a lateral groove extending in a tire width direction,
In a studless tire in which a sipe extending in the tire width direction is formed in a block, a negative ratio is 36 to 40%, a side wall angle of a tread opening of a main groove is in a range of 15 to 25, and the sipe is 2 A studless tire, comprising a set of blocks, and dividing a block into a narrow region sandwiched between the sipes and a wide region located on both sides of the narrow region via the sipes.