JPH05178031A - Pneumatic tire - Google Patents

Abstract

(57) [Summary] (Corrected) [Purpose] To maintain the on-ice performance from the beginning to the end of wear while suppressing uneven wear. [Structure] By a longitudinal groove 3 extending in the tire circumferential direction and a lateral groove 5 intersecting with the longitudinal groove 3, the tread surface 2 is divided into block rows 11, 11 on both sides and a central block row 1 between 1 and 3 rows.
Divide into 5. Lateral groove 5 that divides the central block row 15
Includes a shallow lateral groove 6 that is shallower than the vertical groove 3 and a shallow lateral groove 6
The siping 20 is formed on the bottom surface 6S. The shallow lateral groove 6 and the siping 20 have specific shapes and arrangements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of exhibiting on-ice performance from the initial stage to the final stage of wear while suppressing uneven wear.

[0002]

2. Description of the Related Art In recent years, with the improvement of road networks and the high performance of vehicles, studless tires have been widely used which are capable of running on a shallow snowy road while maintaining high-speed running performance. In general, this type adopts a block pattern with a high sea ratio and sipes are formed on the block surface in order to improve the running performance on ice and snow roads.

This is because the block pattern with a high sea ratio is used to increase the ground contact pressure and enhance the snow bite, while the formation of siping causes a scratching effect on the road surface, and the synergistic effect of these increases the road surface friction coefficient. Is intended.

[0004]

However, in such a conventional block pattern, the groove depths of the circumferential longitudinal grooves that divide the normal block and the transverse grooves that cross the ordinary blocks are set to be substantially the same. , Pattern rigidity becomes insufficient. As a result, the movement of the block in the circumferential direction during driving becomes excessive, leading to uneven wear such as heel-and-toe wear, resulting in reduced wear life and reduced running performance on good roads and snowy roads. To do.

An object of the present invention is to provide a pneumatic tire capable of suppressing uneven wear and exhibiting ice performance at the end of wear, based on the use of shallow lateral grooves having sipes formed on the groove bottom surface. ..

[0006]

In order to achieve the above object, the present invention provides a pneumatic tire comprising a plurality of vertical grooves (3) extending in the tire circumferential direction on a tread surface (2) and the vertical grooves (3). By providing a transverse groove (5) intersecting with 3), on the tread surface (2), a block row (11) (11) on the side composed of blocks (10) arranged in the circumferential direction along the tread edge,
25 arranged in the circumferential direction between the side block rows (11) (11)
A tire having a block pattern divided into 1 or more and 3 or less central block rows (15) consisting of 1 or more and 60 or less blocks (13), wherein the blocks of the central block row (15) ( The lateral groove (5) for partitioning 13) has a depth A smaller than the depth P of the vertical groove (3).
By including the shallow lateral groove (6) of the bottom surface (6S) higher than the bottom surface (3S) of the vertical groove (3), the tire shaft of the bottom surface (6S) is provided on the bottom surface (6S) of the shallow lateral groove (6). Direction length X or less and 0.7 times (0.7X) or more of the length X in the tire axial direction and a groove width Z of 0.2 to 1.1 mm.
While forming the siping (20) which is interrupted at both ends of the bottom surface (6S), the depth A of the shallow lateral groove (6) is
Is 0.2 times or more and 0.5 times or less of the depth P of the vertical groove (3), and the depth B of the siping 20 is 0.2 times or more and 0..0 or more of the depth P of the vertical groove (3). It is 5 times or less, and the sum (A + B) of the depth A and the depth B is 0.7 times or less of the depth P.

[0007]

The horizontal groove that divides the central block row includes a shallow horizontal groove that is shallower than the vertical groove. Therefore, the movement of the blocks during traveling can be restrained and uneven wear can be suppressed as compared with the conventional block pattern including the horizontal grooves having the same depth as the vertical grooves. Further, the siping provided on the bottom surface of the shallow lateral groove is exposed on the tread surface due to the loss of the shallow lateral groove due to wear, and by suppressing the decrease in the edge component of the block pattern due to the loss, the ice performance is maintained from the initial stage to the final stage of wear. ..

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a pneumatic tire 1 includes a tread portion 22 having a tread surface 2 provided with a block pattern, a pair of sidewall portions 23 extending inward in the tire radial direction from both ends of the tread portion 22, and each sidewall portion 23. A bead portion 24 located at the inner end of the tire in the radial direction,
In this example, the tire is for a heavy-duty vehicle. Further, a carcass 26 whose both ends are folded back around the bead core 25 of the bead part 24 from the tread part 22 to the sidewall part 23 is spanned between the bead parts 24, 24, and the carcass 26 in the radial direction. Outside and tread portion 22
A tough belt layer 27 of, for example, four layers using a steel cord is wound inside the sheet, and the tread portion 22 is reinforced with a hoop effect.

As shown in FIG. 2, the block pattern has vertical grooves 3 extending in the tire circumferential direction and lateral grooves 5 intersecting the vertical grooves 3. The vertical grooves 3 and the lateral grooves 5 form the tread. A block row 11 on the side extending in the circumferential direction along the tread edge and one or more and three or less central block rows 1 arranged between the block rows 11 on the side.
It is divided into 5.

In this example, the vertical groove 3 is composed of a substantially zigzag inner vertical groove 3a arranged on both sides of the tire equator and a substantially linear outer vertical groove 3b arranged outside thereof. It consists of four. Therefore, in this example, the central block row 15 has a three-row structure including a central inner block row 15a passing on the tire equator and an outer central outer block row 15b, and the central inner block row 15a is It is formed by 25 to 60 inner blocks 13a surrounded by the inner vertical grooves 3a and the inner horizontal grooves 5a that cross the inner vertical grooves 3a, and the outer block row 15b at the center includes the inner and outer vertical grooves 3a and 3b. It is formed by 25 to 60 outer blocks 13b surrounded by the outer lateral grooves 5b that traverse.

The block row 11 on the side is provided with an outer vertical groove 3b.
And the block 10 on the side surrounded by the tread edge and the lateral groove 5c that traverses the tread edge. In order to distinguish the vertical groove 3 from the horizontal groove 5 in FIG. 2, the vertical groove 3 is provided with a dot pattern for convenience.

In the present invention, the lateral grooves 5 that partition the blocks 13 of the central block row 15, that is, the inner lateral grooves 5a and the outer lateral grooves 5b, each include a shallow lateral groove 6.

Shallow lateral groove 6a included in the lateral groove 5a.
3 is a shallow-bottom lateral groove having a bottom surface 6S higher than the bottom surface 3S of the vertical groove 3 by having a depth A smaller than the depth P of the vertical groove 3, as shown in FIGS. In this example, the inner lateral groove 5a is composed of a deep lateral groove 7a having a depth equal to the depth P of the vertical groove 3 and the shallow lateral groove 6a, and the lateral grooves 6a, 7a are arranged in the circumferential direction. Are arranged alternately. 3 is a projection of the MM line cross section of FIG. 2 in the tire circumferential direction, and FIG. 4 is NN of FIG.
A line cross section is shown.

Therefore, at least one block wall surface of the inner block 13 is adjacent to the shallow lateral groove 6a to enhance the pattern rigidity and effectively restrain the movement of each block 13 in the circumferential direction.

On the bottom surface 6S of the shallow lateral groove 6a, 0.2 to 0.2
A sipe 20 having a groove width Z of 1.1 mm and extending along the center line of the shallow lateral groove 6a and having both ends interrupted in the bottom surface 6S is formed in this example.

The siping 20 is exposed on the tread surface 2 when the wear corresponding to the depth A progresses on the tread surface 2 and the shallow lateral groove 6a is lost. Therefore siping 20
The pattern edge component does not decrease due to the loss of the shallow lateral grooves 6a, and the opening edge scratches the road surface to maintain the on-ice performance of the tire up to the end of wear.

Further, in order to effectively maintain the performance on ice and restrain the movement of the block, the length Y of the siping 20 in the tire axial direction is set to the bottom surface 6S of the shallow lateral groove 6. Of tire axial length X of 0.7
The depth A of the shallow lateral groove 6 is 0.2 times or more and 0.5 times or less the depth P of the vertical groove 3, and the depth B of the siping 20 is vertical. It is necessary that the depth P of the groove 3 is 0.2 times or more and 0.5 times or less, and the sum (A + B) of the depth A and the depth B is 0.7 times or less of the depth P. is there.

That is, when the depth A is more than 0.5 times the depth P, the movement of the block 13 cannot be sufficiently suppressed due to insufficient reinforcement of the pattern rigidity, which causes uneven wear. To do. On the contrary, when the depth is less than 0.2 times the depth P, the groove volume of the shallow lateral groove 6 becomes too small, impairing the snow chewability and deteriorating the snow performance at the initial stage of wear. Further, when the length Y of the siping portion 20 is less than 0.7 times the length X of the shallow lateral groove 6, the road surface scratching effect when the siping portion 20 is exposed becomes insufficient and the performance on ice at the end of wear is improved. descend.

The depth B of the siping portion 20 is the depth P.
When it is larger than 0.5 times, especially the sum of the depth A (A +
When B) is greater than 0.7 times the depth P, the pattern rigidity is impaired, and when the depth B is less than 0.2 times the depth P, the loss of the siping portion 20 due to wear is accelerated and braking on ice is prevented. Shorten the maintenance period.

Even when such regulation is performed, it is recognized that there is a certain difference between the performance on ice by the shallow lateral groove 6a and the performance on ice by the siping 20. Therefore, in this example, In order to optimize the balance of performance on ice from the initial stage to the final stage of wear, the above sum (A
The ratio A / (A + B) of the depth A to + B) is 0.3 or more and 0.7 or less, and the groove width Z of the siping 20 is 0.1 or more and 0.3 of the groove width W of the shallow lateral groove 6. It is less than twice.

A shallow lateral groove 6b included in the outer lateral groove 5b.
Is a shallow-bottom lateral groove having a bottom surface 6S higher than the bottom surface 3S of the vertical groove 3, similar to the shallow lateral groove 6a.
All of the outer lateral grooves 5b are constituted by the shallow lateral grooves 6b. Further, on the bottom surface 6S of each shallow lateral groove 6b, similarly to the shallow lateral groove 6a, a siping 20 is formed that extends along the center line of the shallow lateral groove 6b and has both ends interrupted within the bottom surface 6S.
The length Y, the groove width Z, and the depth B are regulated as described above.

The ground pressure of the central block row 15 is larger than that of the side block row 11, so that the shallow lateral groove 6 having such siping 20 is formed in the central block row 15.
The effect of suppressing wear and the effect of improving performance on ice can be most effectively exerted by providing the above.

Further, in this example, in order to further improve the performance on ice, each block 10, 13 is formed with a siping 21 having a depth corresponding to the sum (A + B).

The siping 20 and the siping 2 are provided.
1 preferably extends at an angle θ of 30 degrees or less with respect to the tire axial direction, and if the angle exceeds 30 degrees, the road surface scratchability is significantly reduced.

[0025]

As described above, since the pneumatic tire of the present invention is provided with the shallow lateral groove having a predetermined size of siping, uneven wear can be suppressed and the performance on ice can be maintained from the initial stage to the final stage of wear. ..

[Brief description of drawings]

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

FIG. 2 is a development view showing the block pattern.

FIG. 3 is a diagram in which a MM line cross section showing a shallow lateral groove is projected in the circumferential direction.

FIG. 4 is a sectional view taken along the line N-N showing shallow lateral grooves.

[Explanation of symbols]

 2 tread surface 3, 3a, 3b vertical groove 3S vertical groove bottom surface 5, 5a, 5b, 5c horizontal groove 6, 6a, 6b shallow horizontal groove 6S shallow horizontal groove bottom surface 10, 13, 13a, 13b block 11 side block row 15, 15a, 15b central block row 20 siping

Claims (1)

[Claims] 1. The tread surface (2) is provided with a plurality of vertical grooves (3) extending in the tire circumferential direction and lateral grooves (5) intersecting with the vertical grooves (3) on the tread surface (2). , A block row (11) (11) on the side composed of blocks (10) arranged in the circumferential direction along the tread edge, and a block row (1) on the side
1) A tire having a block pattern divided into 1 or more and 3 or less central block rows (15) consisting of 25 or more and 60 or less blocks (13) arranged in the circumferential direction between (11), , The lateral groove (5) for partitioning the blocks (13) of the central block row (15) has a depth A smaller than the depth P of the vertical groove (3), so that A shallow lateral groove (6) having a bottom surface (6S) higher than the bottom surface (3S) is included, and the bottom surface (6S) of the shallow lateral groove (6) has a length X or less in the tire axial direction of the bottom surface (6S) and the length. X
A length Y in the tire axial direction of 0.7 times (0.7X) or more, a groove width Z of 0.2 to 1.1 mm, and a sipe (20) that is cut off at both ends of the bottom surface (6S). Meanwhile, the depth A of the shallow lateral groove (6) is 0.2 times or more and 0.5 times or less the depth P of the vertical groove (3),
The depth B of 0 is 0.2 times or more and 0.5 times or less the depth P of the vertical groove (3), and the sum of the depth A and the depth B (A +
A pneumatic tire in which B) is 0.7 times or less of the depth P.