JP2899653B2 - Pneumatic radial 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 radial tire, and more particularly to a pneumatic radial tire having improved running performance on snow and suitable for use in winter.

[0002]

2. Description of the Related Art Conventionally, pneumatic radial tires having high running performance on ordinary dry road surfaces have been widely used, and their tread patterns generally have a plurality of vertical grooves and horizontal grooves. I have. However, a radial tire having a normal tread pattern has a problem in that grip performance and other running performance when traveling on a road surface with snow in winter or the like are insufficient. Running performance on snow generates traction by the sum of the frictional force between the tread and the compacted snow surface and the shearing force of the snow column between the blocks formed by the grooves provided in the tread pattern. In particular, the magnitude of the shear force of the snow column greatly affects the running performance on snow. Therefore, as means for improving the running performance by increasing the snow column shearing force, the width of the groove of the tread pattern is increased, or the groove is deepened.

[0003]

However, in the above-described conventional means for increasing the snow column shearing force in the pneumatic radial tire, the snow column shearing force is increased and the running performance on snow is improved, but the individual tread pattern is not improved. There was a problem that the rigidity of the block was reduced, and the steering stability on a dry road surface was reduced.

[0004] It is an object of the present invention to provide a pneumatic radial tire having improved on-snow performance and capable of ensuring steering stability on a dry road surface without impairing on-snow performance.

[0005]

In order to achieve the above object, a pneumatic radial tire according to the present invention is a pneumatic radial tire having at least one main groove including at least one longitudinal groove and a plurality of lateral grooves in a tread. An auxiliary block is provided in at least one of the vertical groove and the horizontal groove, and the width w and the height d of the auxiliary block are 0.1 <w / W <0.5 0.1 with respect to the width W and the depth D of the main groove. <D / D <0.8 is satisfied.

[0006]

By providing the auxiliary block in the main groove, the rigidity of the block located in the vicinity of the auxiliary block is increased, the steering stability on a dry road surface is ensured, and the width w and the height d of the auxiliary block are secured. Is set within a predetermined range with respect to the width W and the depth D of the main groove, so that the auxiliary block moves in the main groove at the rear end of the contact portion to smoothly discharge the snow in the groove, thereby improving the performance on snow. The steering stability on dry road surfaces can be ensured without compromising performance.

[0007]

An embodiment will be described with reference to the drawings. In FIG. 1, a tread 1 of a pneumatic radial tire suitable for use in winter is provided at a central portion of the tread 1 and is formed in a zigzag shape and extends in a circumferential direction. And a pair of intermediate longitudinal grooves 3 formed in a straight line and extending in the circumferential direction, and provided on the outer side in the tread width direction of the intermediate longitudinal grooves 3 and formed in a zigzag shape and extending in the circumferential direction. Both ends of the longitudinal groove 4, the central longitudinal groove 2, and the intermediate longitudinal groove 3 communicate with each other, and the central horizontal groove 5 extends in the tread width direction. The both ends communicate with the intermediate longitudinal groove 3 and the outer longitudinal groove 4, and extend in the tread width direction. An intermediate lateral groove 6 and an outer lateral groove 7 having both ends communicating with the outer longitudinal groove 4 and the tread end 1a and extending in the tread width direction are provided. These main grooves 2, 3, 4, 5, 6, 7 are:
In order to increase the snow column shearing force, the groove width W and the groove depth D are made larger than those of a normal radial tire. Central flute 2
And the inner vertical block 3 by the middle vertical groove 3 and the central horizontal groove 5,
The intermediate vertical groove 3, the outer vertical groove 4, and the intermediate horizontal groove 6 form the intermediate block 9, and the outer vertical groove 4, the tread end 1 a, and the outer horizontal groove 7
Forms a shoulder block 10. In addition,
Since the central longitudinal groove 2 and the outer longitudinal groove 4 are formed in a zigzag pattern, the edge of each of the blocks 8, 9, 10 facing the central longitudinal groove 2 or the outer longitudinal groove 4 is positioned on the circumferential straight line. Instead, they are arranged offset from each other, increasing the effect of digging into the snow surface and improving grip performance.

Each of the blocks 8, 9, 10 has a plurality of sipes 11, 12, 13 extending in the tread width direction and having one end communicating with the longitudinal grooves 2, 3, 4, respectively (in this embodiment, 4 sipes 11, 12, 13).
Book) is provided. Inside block 8 siping 11
The one in which one end communicates with the central longitudinal groove 2 and the one in which one end communicates with the intermediate longitudinal groove 3 are alternately arranged. The siping 11 of the intermediate block 9 has one end communicating with the intermediate longitudinal groove 3. And one whose one end communicates with the outer longitudinal groove 4 are alternately arranged, and the siping 12 of the shoulder block 10 is
Only communicates with These sipings increase the contact area between the block surface and the snowy road surface, improve grip performance on the snowy road surface, and improve traction performance on the snowy road surface due to the effect of excavating the snowy road surface. Further, the effect of the siping can be greatly improved by connecting the siping to the longitudinal groove. If the number of sipings provided in each of the blocks 8, 9, and 10 is less than three, the block rigidity is too high to improve the running performance on ice and snow road surfaces. And adversely affect steering stability, especially on a dry road.

An auxiliary block 14 extending in the tread width direction is provided in the outer lateral groove 7 between the shoulder blocks 10,
The auxiliary block 14 has a width w in the circumferential direction of the tread,
Is formed in a range satisfying 0.1 <w / W <0.5 0.1 <d / D <0.8 with respect to the groove width W and the groove depth D of the outer lateral groove 7 (see FIG. 4). 2 and FIG. 3).

With the above structure, the auxiliary block 14 located at the rear end of the ground contact portion moves in the outer lateral groove 7, so that the snow in the outer lateral groove 7 is smoothly discharged, and the performance on snow is not impaired. In addition, the rigidity of the shoulder block 10 is increased by the auxiliary block 14, and steering stability performance on a dry road surface can be secured (see FIGS. 4 and 5). In addition,
4 and 5 show the steering stability with respect to changes in w / W and d / D in an actual vehicle feeling test and are indicated by an index with the reference being 100.

When w / W ≦ 0.1, the rigidity of the auxiliary block 14 becomes too small and the durability decreases. When w / W ≧ 0.5, the groove width w of the outer lateral groove 7 becomes narrow and the groove depth D becomes shallow. The performance on snow rapidly decreases (see FIG. 6). When d / D ≦ 0.1, the effect due to the presence of the auxiliary block 14 cannot be sufficiently obtained.
When d / D ≧ 0.8, the rigidity of the auxiliary block 14 decreases, and the performance on snow rapidly decreases (see FIG. 7). 6 and 7 show that the performance on snow with respect to the change of w / W and d / D is 0 to 0.
The time required for 50m is measured and the index is displayed with the standard set to 100.

The auxiliary block 14 is provided at a position shifted rearward in the tire rotation direction from the center of the outer lateral groove 7,
60% of the distance W _M a groove width W of the outer lateral grooves 7 between the rear end of the front shoulder blocks 10 of the front end i.e. the auxiliary block 14 on the front end and the outer lateral grooves 7 of the auxiliary block 14 in this embodiment (W _M
= 0.6 W). With this configuration, the auxiliary block
The rigidity of the shoulder block 10 located behind the 14 can be increased. Further, in this embodiment, the auxiliary block
The height d of 14 is 70% of the groove depth D of the outer lateral groove 7 (d = 0.7
And D), a rear end and a depth D _M grooves of the outer lateral grooves 7 of the formed sub-groove 13a between the front end of the rear shoulder blocks 10 of the outer lateral grooves 7 of the rear end i.e. the auxiliary block 14 of the auxiliary block 14 It is set to 50% of the depth D (D _M = 0.5 D).

[0013]

Since the present invention is configured as described above, the following effects can be obtained. By providing the auxiliary block in the main groove, the rigidity of the block located in the vicinity of the auxiliary block is increased to ensure the steering stability on a dry road surface, and the width w and height d of the auxiliary block
Is set within a predetermined range with respect to the width W and the depth D of the main groove, so that the auxiliary block moves in the main groove at the rear end of the contact portion to smoothly discharge the snow in the groove, thereby improving the performance on snow. The steering stability on dry road surfaces can be ensured without compromising performance.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a graph of steering stability with respect to the width of an auxiliary block.

FIG. 5 is a graph of steering stability with respect to the height of an auxiliary block.

FIG. 6 is a graph of performance on snow with respect to the width of an auxiliary block.

FIG. 7 is a graph of performance on snow with respect to the height of an auxiliary block.

[Explanation of symbols]

1 tread, 2 central longitudinal groove, 3 intermediate longitudinal groove, 4 outer longitudinal groove, 5 central lateral groove 6 intermediate lateral groove, 7 outer lateral groove, 8 inner block, 9
Intermediate block 10 Shoulder block, 11, 12, 13 Siping, 14
Auxiliary block

Continuation of the front page (56) References JP-A-2-20407 (JP, A) JP-A-64-18706 (JP, A) JP-A-4-201608 (JP, A) JP-A-4-243605 (JP, A) JP-A-4-228308 (JP, A) JP-A-3-153404 (JP, A) JP-A-2-293204 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB Name) B60C 11 / 04,11 / 11

Claims (1)

(57) [Claims] 1. A pneumatic radial tire having a main groove including at least one vertical groove and a plurality of lateral grooves in a tread, an auxiliary block is provided at least in the lateral groove , and the width w and the height d of the auxiliary block are set to be equal to each other. The width W and the depth D of the main groove satisfy 0.1 <w / W <0.5 and 0.1 <d / D <0.8, and the auxiliary block provided in the lateral groove.
Is formed at a position shifted in the circumferential direction from the center of the lateral groove.
The auxiliary block and the block closer to the auxiliary block
The depth D _M from the minor groove of the tread surface between the click, the main
A pneumatic radial tire having a depth smaller than a groove depth D.