JP2002127716A - Tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire which reconciles its performance on ice- or snow-covered roads with its resistance to partial abrasion, thereby suppressing deterioration in the performance on ice- or snow-covered roads even when the tire is worn out and reducing the frequency of tire rotation. SOLUTION: In a tire with a block pattern provided with blocks 5 formed by both plurality of main grooves of the circumferential direction 1a-1c extending consecutively in the circumferential direction and grooves of the widthwise direction dividing in the widthwise direction of the tire the lines of land parts formed between the main grooves of the circumferential direction, the respective blocks 5 are subdivided by at least two of sipeings 7 opening to the main grooves of the circumferential direction 1a-1c, protruding land parts 8a and 8b are formed in the circumferential direction at the bottom part of at least one of the main grooves of the circumferential direction 1a-1c, and the surfaces of the protruding land parts 8a and 8b form steps protruding above the outer contour of the tire so that the surfaces skid on and come into contact with the ground when the tire rotates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty winter tire mainly for running on ice and snow, and more particularly, to a performance on ice and snow from the time of new article to the time of wear by greatly improving uneven wear resistance. The present invention relates to a tire that has suppressed the decrease in the tire.

[0002]

2. Description of the Related Art Among pneumatic radial tires used for heavy-duty wheels such as trucks and buses, the tread pattern of an all-season type or braking / driving-oriented tire is effective in a lateral groove and a block pattern is effective. Widely used. It is also known that increasing the edge density caused by blocks and sipes projected in the width direction is generally effective for improving the performance on ice and snow.

[0003] As a pneumatic radial tire for heavy loads for which the performance on ice and snow is improved, for example, a tire having a tread pattern shown in Fig. 3 is known. In this tread pattern, three main grooves 11a, 11b, 11c contributing to ensuring drainage and a sub-groove 12a continuously extending in the circumferential direction between each of these main grooves 11a, 11b, 11c are provided on the outer periphery of the tread T. , 12b and six rows of land portions 13a-1
3f are defined, and these land rows are further divided by width direction grooves 14a to 14f extending in the tire width direction to form a block 15. Each block 15
Two sipes 1 opening in the circumferential main groove or circumferential sub groove
7 and a sipe 18 opening in one width direction groove.

[0004]

However, the conventional tires in which the performance on ice and snow is improved by increasing the edge density generated by the blocks and sipes, as compared with a tire having a rib mix pattern for a general good road. Since the pattern rigidity is small, the block rigidity at the time of rolling the tire is low, and when running on a road other than a general road on a dry road surface or a wet road surface, that is, a road surface other than an icy road with a low friction coefficient μ, is frequently used. Uneven wear (heel and toe wear step) due to the rotation direction occurs (FIG. 4 shows the step amount A). The occurrence of such uneven wear deteriorates the contact property between the tire road surfaces, and eventually causes a decrease in performance on ice and snow. For this reason, the user is forced to perform an appropriate tire rotation (reverse rotation direction) man-hour.

Accordingly, an object of the present invention is to provide a tire which achieves a balance between performance on ice and snow and resistance to uneven wear, suppresses a decrease in performance on ice and snow even when the tire is worn, and reduces the frequency of tire rotation. Is to do.

[0006]

In order to solve the above-mentioned problems, a tire according to the present invention comprises a plurality of circumferential main grooves extending continuously in a circumferential direction, and a land row formed between the circumferential main grooves. In a tire having a block pattern having blocks defined by width-directional grooves that divide the tire in the tire width direction, each block is subdivided by at least two sipes that open in the circumferential main groove, and At least one groove bottom of the circumferential main groove has a protrusion land portion formed in the circumferential direction,
The surface of the projecting land portion has a step so that the surface comes into sliding contact with the outer contour of the tire when the tire is rolling.

In the tire of the present invention, it is preferable that a circumferential sub-groove extending continuously in the circumferential direction is further provided between the circumferential main grooves, and the circumferential main groove has a circumferential length of each block. In contrast, it is preferable that the waves are waved at a phase of 30 to 70%.

The present invention realizes both the performance on ice and snow and the resistance to uneven wear based on the following findings, and suppresses the deterioration of the performance on ice and snow even when tires are worn. First, regarding the performance on ice and snow, it is important to suppress the generation of a water film by increasing an edge effect (scratching and removing a water film) generated by a block or a sipe and reducing a contact surface pressure by increasing a contact area. Here, in order to improve the edge effect, there is a means for increasing the number of sipes of the blocks in the ground plane, but on the other hand, the block rigidity is reduced and the uneven wear resistance is deteriorated. If uneven wear occurs, the effective contact area decreases, and if the vehicle continues to travel, uneven wear will progress, and the performance on ice and snow will be greatly reduced as compared with a new product. Therefore, in the present invention, uneven wear resistance is improved by applying the projecting land portion in the main groove, which has been known in the rib mix pattern, to a winter tire, and the performance on ice and snow is highly compatible. Is made possible. Here, the protrusion land portion in the main groove has an effect of reducing the uneven wear of other portions by concentrating the braking force generated during rolling of the tire on the rib in the main groove.

[0009]

FIG. 1 is a partial plan development view of a tread of a tire according to an embodiment of the present invention.

On the outer periphery of the tread T, there are three main grooves 1a, 1b, 1c which contribute to ensuring drainage, and these main grooves 1a, 1b, 1c.
b, 1c, the sub-grooves 2a, 2 extending continuously in the circumferential direction
b define six rows of land portions 3a to 3f. These land sections are provided with width direction grooves 4a to 4a extending in the tire width direction.
The block 5 is further divided by f.
The blocks 5 formed with the sub-grooves 2a and 2b interposed therebetween are preferably provided with widthwise grooves so as to be alternately arranged in the circumferential direction as shown in the figure. Further, it is preferable that the width direction grooves 4a to 4f are appropriately inclined with respect to the tire width direction, preferably, 5 to 25 degrees.

Each block 5 is subdivided by two sipes 7 opening in the circumferential main groove and the circumferential sub groove. The number of sipes should not be particularly limited,
It can be determined as appropriate.

In the illustrated preferred embodiment of the present invention, projecting land portions 8a and 8c are formed in the circumferential direction at the groove bottoms of the circumferential main grooves 1a and 1c, and the surface of the projecting land portions is formed on the outer contour of the tire. On the other hand, there is a step so that the surface comes into sliding contact when the tire is rolling. In other words, the uneven land portions 8a and 8c provided in the circumferential main grooves 1a and 1c have uneven surfaces by making the surface thereof a step with respect to the outer contour of the tire and slidingly contacting the surface when rolling the tire. It has the effect of concentrating the force to be applied to the protrusion in the groove and suppressing the generation of the force on other land portions. As shown in the cross section in FIG.
%, And the step d with respect to the outer contour is preferably 10 to 20% of the main groove depth D.

According to the present invention, the circumferential main groove has a phase H having an interval of 30 to 70% with respect to the circumferential length L of each block.
It is preferable to be shaken. This is for improving the edge component projected in the width direction, and is more preferably 50 to 65%.

In the case of the above preferred embodiment having three circumferential main grooves, the width of the main grooves 1a, 1b, 1c is preferably 3.
5 to 8.5 mm, and the width of the sub-grooves 2 a and 2 b is preferably 2.0 to 3.5 mm. Also, the sub-grooves 2a, 2b
Is preferably in the range of 40 to 60% of the main groove depth. Further, the width of the width direction grooves 4a to 4f is preferably 5 to 8 mm.

The tread of the tire of the present invention can be provided with a sipe or a lug groove as needed. In the preferred embodiment shown in the drawings, the sipe of each block is 0.5 mm to 1. A lug groove 9 having a depth of 5 mm is provided.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. As an example, a pneumatic radial tire of size TBR11R22.5 having a tread pattern shown in FIG. 1 was prototyped. The values of the tread pattern of such a tire are as follows.

Width of circumferential main grooves 1a, 1b, 1c: 5.1
mm, 7.4 mm, 5.1 mm Width of circumferential sub-grooves 2a, 2b: 2.8 mm Width of protrusion land portions 8a, 8b: 40% of main groove width Step of protrusion land portions 8a, 8b: Main groove depth The phase H of the circumferential main groove with respect to the circumferential length L of each block
Ratio: 44% Width of the width direction groove: 6.7 mm Main groove depth: 15 mm

As a comparative example, a radial tire having a tread pattern shown in FIG. 3 (each groove width and the like correspond to the pattern of the example) was prototyped.

The tires of the example and the comparative example were subjected to an internal pressure of 70
At 0kPa, mounted on 22D type vehicle (10 each)
The vehicle traveled on the field at a running distance of 20273 km, and the uneven wear resistance was evaluated by the number of rotations between the vehicles. In the evaluation, the tire of the comparative example was set to 100 and indicated by an index. The smaller the value, the better the result.

Next, the tires of the example and the comparative example were subjected to a μ test on indoor ice at an internal pressure of 700 kPa. Load 247
A brake test was performed under the conditions of 1 kN, and the tires of the example and the comparative example were each 30% assuming 100 as new.
The performance on ice during wear was indicated by an index. The higher the value, the better the result.

[0021]

[Table 1]

[0022]

As described above, in the tire according to the present invention, a reduction in performance on ice and snow at the time of tire wear is suppressed by achieving a balance between performance on ice and snow and resistance to uneven wear. Can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a partial development view of a tire tread according to an embodiment of the present invention.

FIG. 2 is a sectional view of a protrusion land portion in a main groove.

FIG. 3 is a sectional view showing uneven wear of a block.

FIG. 4 is a partial development view of a conventional tire tread.

[Explanation of Signs] 1a, 1b, 1c Circumferential main groove 2a, 2b Circumferential sub groove 3a-3f Land portion row 4a-4f Width direction groove 5 Block 7 Sipe 8a, 8b Projection land portion 9 Lug groove

Claims (3)

[Claims] 1. A block defined by a plurality of circumferential main grooves extending continuously in a circumferential direction, and a width direction groove formed between the circumferential main grooves to divide a land portion row in a tire width direction. In the tire having a block pattern, each block is subdivided by at least two sipes opening into the circumferential main groove, and a protrusion land portion is formed on a bottom of at least one groove of the circumferential main groove. The tire is characterized in that the surface of the protrusion land portion has a step so that the surface makes sliding contact with the outer contour of the tire when the tire rolls. 2. The tire according to claim 1, further comprising a circumferential auxiliary groove extending continuously in the circumferential direction between the circumferential main grooves. 3. The tire according to claim 1, wherein the circumferential main grooves are oscillated at a phase of 30 to 70% of a circumferential length of each block.