JP2009046052A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which is superior in both on-ice performance and on-snow performance, and maintains the on-ice/on-snow performance satisfactorily even after abrasion of a tread face. <P>SOLUTION: The pneumatic tire includes, on the tread face of the tire, a plurality of circumferential grooves extended along a tread circumferential line, and a plurality of main blocks divided by a plurality of lateral grooves extended in a tread width direction. In the pneumatic tire, sidewall blocks which are lower in height than the main blocks are provided at least one side of main block walls adjacent to the circumferential grooves, per at least one circumferential groove, and the sidewall blocks and the main blocks are divided by circumferential sipes extending along a direction of the tread circumferential line, and the sidewall blocks are provided with width direction sipes extending along the tread width direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and particularly intends to improve its snow and snow performance.

2. Description of the Related Art Conventionally, winter pneumatic tires are required to improve on-ice performance and on-snow performance such as acceleration and braking performance when starting on an icy road surface and a snowy road surface, that is, to improve icy and snow performance. Among the snow and snow performance, a technology has been proposed for the performance on snow, by increasing the groove width of the tread portion of the tire to ensure that the tire does not slip on the snow road surface.
On the other hand, with regard to the performance on ice, a technique has been proposed in which the contact area with the icy road surface is increased by increasing the contact area of the land portion (block) of the tread surface that contacts the icy road surface.

  However, if the groove width of the tread is increased to improve the performance on snow, the contact area of the land portion (block) on the tread surface that contacts the icy road surface decreases and the contact surface with the icy road surface becomes smaller. On the other hand, the performance on ice tended to decrease.

  On the other hand, when the contact area of the land part (block) on the tread surface that contacts the ice road surface is increased in order to improve the performance on ice, the groove width of the tread part cannot be increased, so the performance on snow. It will be difficult to improve.

In order to improve the above-mentioned snow and snow performance, Patent Document 1 is provided with a grip step extending in the longitudinal direction of the groove along the contour line of the side wall on at least one of both side walls of the circumferential groove in the tread portion of the tire. Pneumatic tires have been proposed.
However, the technique disclosed in Patent Document 1 has not yet achieved a sufficiently satisfactory effect with respect to ice / snow performance.
Japanese Patent No. 2865765

  In winter pneumatic tires, if the tread surface of the tire is worn and the groove depth decreases, the effect of the groove pressing and shearing the snow (hereinafter referred to as snow column shear force) decreases. The performance on snow tended to decrease after wear. Similarly to the above, as the groove depth decreases, the rigidity of the tread surface block or land portion increases, so the followability to the ice road surface deteriorates and the performance on ice tends to decrease. there were.

  Therefore, it has been desired to develop a pneumatic tire that is excellent in both on-ice performance and on-snow performance and can maintain the icy / snow performance even after wear.

  The present invention advantageously responds to the above-described demand, and provides a pneumatic tire that is excellent in both on-ice performance and on-snow performance, and that can maintain good on-ice performance even after the tread surface is worn. Objective.

As a result of intensive studies to achieve the above object, the inventors have provided an auxiliary block whose height is lower than that of the main block on the side wall of the main block defined by the circumferential groove and the lateral groove. In addition, we obtained knowledge that this auxiliary block is effective in achieving the intended purpose by dividing the block with sipes.
The present invention is based on the above findings.

That is, the gist of the present invention is as follows.
(1) A pneumatic tire having a plurality of main blocks partitioned by a plurality of circumferential grooves extending along a tread circumferential line and a plurality of lateral grooves extending in a tread width direction on a tread surface of the tire, For at least one of the circumferential grooves, a side wall block having a height lower than that of the main block is provided on at least one side of the main block wall adjacent to the circumferential groove, and the side wall block extends along the tread circumferential direction. A pneumatic tire characterized by having a plurality of widthwise sipes that are separated from the main block via an extending circumferential sipes and that extend along the tread width direction.

(2) The pneumatic tire according to (1), wherein the main block wall is provided with a plurality of side wall blocks whose height gradually decreases.

(3) When the main block is provided with a width-direction sipe, the interval between the width-direction sipes in the side wall block is made smaller than the interval between the width-direction sipes in the main block (1) Or the pneumatic tire as described in (2).

  According to the present invention, a side wall block whose height is lower than that of the main block is provided on at least one side of the main block wall in the circumferential groove, the side wall block is separated from the main block via the circumferential sipe, and the side wall block is provided. By providing the sipe in the width direction, the edge effect of the sipe of the side wall block is exhibited in addition to the snow column shear force on the snowy road, so that the performance on snow can be improved. Further, since the side wall block is separated from the main block by the circumferential sipe and the block rigidity is not increased, excellent on-ice performance can be maintained while ensuring on-snow performance.

The present invention will be specifically described below.
FIG. 1 shows a tread pattern of a pneumatic tire according to the present invention, and FIGS. 2A and 2B show an enlarged perspective view and a sectional view in the width direction of a part of the tread pattern.
In FIG. 1, reference numeral 1 is a tread surface, 2 is an illustrated example extending along the tread circumference, 3 circumferential grooves, 3 is a transverse groove extending in the tread width direction, and 4 is a circumferential groove 2 and a transverse groove 3. Shows the main block. In addition, CL shows the center periphery which passes along the width direction center of a tread, and S shows the edge part of the shoulder part of a tire.
2A and 2B, reference numerals 5 and 5a are side wall blocks whose height is lower than that of the main block 4, and 6 and 6a are circumferential directions that divide the main block 4, the side wall block 5, and the side wall blocks. A sipe 7 is a width direction sipe provided on the side wall blocks 5 and 5 a, and 8 is a plurality of small blocks in which the side wall blocks 5 and 5 a are partitioned by the width direction sipe 7. The side wall blocks 5 and 5a are divided into a plurality of small blocks 8 by the width direction sipe 7, thereby forming a small block row.
Moreover, in FIG. 1, although the example which provided the side wall blocks 5 and 5a in all the main block walls adjacent to the circumferential groove | channel 2 was shown, not only this example but the side wall blocks 5 and 5a are equipped with at least 1 piece. The example provided corresponding to the circumferential groove | channel may be sufficient.

  That is, since the side wall block is divided from the main block 4 via the circumferential sipe 6, the side wall block 5 does not affect the rigidity of the main block, and the increase in the rigidity of the main block can be suppressed. it can. As a result, the deterioration of the followability of the main block 4 with respect to the ice road surface is prevented, and the on-ice performance can be maintained.

  Further, by providing the side wall block 5 with the width direction sipe 7, an edge portion is formed in the side wall block 5, and an edge effect is exhibited by this edge portion, so that the snow that has been compacted in the circumferential groove 2 is scratched. be able to. As a result, in addition to the snow column shearing force, the edge effect is exhibited and the performance on snow can be improved.

Further, by making the height h ₁ of the side wall block 5 lower than the height H of the main block 4, the side wall block 5 appears on the tread surface when the main block 4 is worn, and the small block 8 of the side wall block 5. As a result of the edge portion of the small block 8 exhibiting the edge effect, excellent performance on ice can be maintained even after the main block 4 is worn.

  The advantageous effects of the present invention described above can be exhibited mainly when the vehicle is driven, but the advantageous effects of the present invention can also be exhibited when the vehicle is braked. That is, when the load on the front wheel tires increases due to the nose dive that causes the vehicle to descend forward during braking of the vehicle, the deformation of the main block 4 increases. At that time, the side wall blocks 5 and 5a come into contact with the ice road surface or the snow road surface, and the braking friction coefficient is improved, so that the braking performance of the vehicle is improved.

Here, the height h ₁ of the side wall block 5 is preferably 50% or more of the height H of the main block 4. This is because if the height H is less than 50%, the height h ₁ of the side wall block 5 is too low and the side wall block 5 does not appear on the icy road surface until the end of wear of the main block 4, so that the performance on ice is maintained. It is difficult to do. More preferably, the height H is 90% or more of the main block 4. Note that if the height h ₁ of the side wall block 5 and the height H of the main block 4 are the same, it is difficult to obtain the advantageous effects of the present invention, so the height h ₁ of the side wall block 5 is set to the main block 4. The height H is less than 100%.

The depth d ₁ of the circumferential sipe 6 is preferably 30 to 100% of the height h ₁ of the side wall block. This is because if the height h ₁ is less than 30%, the block rigidity of the side wall block 5 will increase too much, so that the edge effect cannot be exerted predominately. More preferably 60 to 100% of the height _{h 1.}

Further, the depth d ₃ of the width direction sipe is preferably 30 to 100% of the height h ₁ of the side wall block. This is because if the height h ₁ is less than 30%, the block rigidity of the small block 8 will increase too much, so that the edge effect cannot be exerted preferentially, whereas it exceeds 100%. This is because the block rigidity of the small block 8 is excessively reduced, and the edge effect cannot be exerted predominately due to excessive collapse.

  From the above results, the side wall block 5 lower than the height H of the main block 4 is provided on the wall of the main block 4 in the circumferential groove, the side wall block 5 and the main block 4 are divided by the circumferential sipe 6, and Since the side wall block 5 has the sipe 7 in the width direction, as described above, the performance on ice and the performance on snow can be maintained, and the performance on ice can be maintained even after wear. .

  1 and 2 show an example in which the side wall blocks 5 and 5a are provided on both sides of the wall of the main block 4 in the circumferential groove 2, the side wall blocks 5 and 5a are provided on the wall of the main block 4. Even if it is an example provided in any one of these, the advantageous effect of this invention can be acquired.

  Moreover, in FIG. 1 and FIG. 2, although the example which gave the width direction sipe 7 to the side wall blocks 5 and 5a and divided | segmented into the small block 8 was shown, it is not restricted to the example divided into the small block 8 by the width direction sipe 7, By providing a width-direction sipe that remains in the side wall blocks 5 and 5a, the edge portion is formed in the side wall blocks 5 and 5a, so that the advantageous effects of the present invention can be obtained.

  Next, the advantageous effect of the present invention can be obtained also by making the side wall block provided on the wall of the main block 4 one stage, but in order to obtain a more advantageous effect, the height is increased stepwise. It is preferable to provide a plurality of side wall blocks which are lowered. That is, as shown in FIGS. 2 (a) and 2 (b), two rows of side wall blocks 5 and 5a are provided on the main block wall adjacent to the circumferential groove 2 so as to be lowered stepwise. Since the side wall block 5a appears after the side wall block 5 is worn, the effect of improving the performance on ice can be further exhibited.

In order to minimize the change in performance on ice when the side wall block is worn, it is effective to reduce the step of the side wall block provided so as to be lowered stepwise. h ₂ is preferably set to more than 50% of the height _{h 1} of the side wall block 5, more preferably, it is better to 90% or more of the height _{h 1.} If the height h ₁ of the side wall block 5 and the height h ₂ of the side wall block 5a are the same, it is difficult to obtain the advantageous effects of the present invention, so the height h _{2 of the} side wall block 5a. Is preferably less than 100% of the height h ₁ of the side wall block 5.

Further, in order to ensure the flexibility of the side wall blocks 5 and 5a are preferably be separated by a circumferential sipe, time, depth d ₂ of the provided between the side walls blocks 5 and 5a circumferential sipe 6a is is preferably 30% to 100% of the height _{h 2} of the side wall blocks 5a. This is because if the height h ₂ is less than 30%, the block rigidity of the small block 8 will increase too much, and the edge effect cannot be exerted predominately. This is because the block rigidity of the small block 8 is excessively reduced, and the edge effect cannot be exerted predominately due to excessive collapse.

Next, as shown in FIG. 3, when the main block 4 is provided with the width direction sipes 7 a, the distance S ₁ between the width direction sipes 7 provided on the side wall blocks 5 and 5 a is set to the width direction sipes of the main block 4. 7a is preferably smaller than the interval S between each other.

That is, by less than spacing S ₁ apart S, since the flexibility of the side wall blocks 5 and 5a can be secured, thereby improving the followability to an icy road and snow road surface. Further, since the number of the width direction sipes 7 provided in the side wall blocks 5 and 5a is larger than the number of the width direction sipes 7a provided in the main block 4, a plurality of edges are produced in the side wall blocks 5 and 5a. Since the edge effect by the edge can be sufficiently secured, the performance on ice and the performance on snow can be improved.

In addition, while maintaining the block rigidity of the main block 4 appropriately, the flexibility on the side wall blocks 5 and 5a is maintained to improve the performance on ice, and the edge effect is increased by increasing the edge portion to improve the performance on snow. The sipe interval S ₁ is preferably 80% or less of the sipe interval S, more preferably 50% or less.

  Here, the direction of the circumferential sipes 6 and 6a with respect to the tread circumferential line can be adjusted within 40 ° with respect to the tread circumferential line. This is because when the angle exceeds 40 °, the edge effect on the lateral input is reduced, and the steering stability on snow and the steering stability on ice are deteriorated. More preferably, the adjustment is within 20 °.

  On the other hand, the direction of the width direction sipes 7 and 7a with respect to the circumferential direction sipe can be adjusted within 40 ° with respect to the direction orthogonal to the circumferential direction sipe 7. This is because when the angle exceeds 40 °, the edge effect in the front-rear direction decreases, and the braking performance and driving performance on snow and the braking performance and driving performance on ice deteriorate. More preferably, the adjustment is within 20 °.

  As shown in FIGS. 1 to 3, the circumferential sipe and the width sipe are not limited to a shape extending incline in the depth direction of the block, but, for example, a three-dimensional sipe bent in the depth direction of the block. Even if the shape is changed in the width direction of the sipe, the advantageous effects of the present invention can be obtained.

  In the block pattern shown in FIG. 1, pneumatic tires of size 195 / 65R15 were manufactured by applying various tread portions according to the corresponding diagram of Table 1 under various specifications shown in Table 1. The obtained tire was incorporated into a standard rim prescribed by JATMA, the internal pressure was adjusted to 200 kPa, and the tire was mounted on a passenger car. A start test and a braking test were performed on icy roads and snowy roads. From such tests, the acceleration on ice, the deceleration on ice, the acceleration on snow, and the deceleration on snow were investigated when the tire was new, when it was 30% worn and 60% worn from the new time. The results are shown in Table 1.

  The start test was performed on the icy and snowy roads by measuring the time (acceleration time) until the final speed of 45 km / h was reached by fully opening the accelerator from the above-mentioned passenger car at the initial speed of 10 km / h. The average acceleration calculated from the velocity, final velocity and acceleration time was evaluated as ice acceleration and snow acceleration. From this result, each was indexed with Comparative Example 1 as 100. The larger the index value, the better.

  In the braking test, on the icy and snowy roads, apply the full brake from the initial speed of 40 km / h on the above-mentioned passenger car, measure the braking distance until it becomes stationary, and calculate from the initial speed and the braking distance. The average deceleration was evaluated as ice deceleration and snow deceleration. From this result, each was indexed with Comparative Example 1 as 100. In addition, it is so favorable that an index value is large.

  From the results of Table 1, the invention example is provided with a side wall block lower than the main block, the side wall block is separated from the main block via a circumferential sipe, and the side wall block is provided with a width direction sipe. It can be seen that the acceleration on ice, the deceleration on ice, the acceleration on snow, and the deceleration on snow have improved from 60% wear to new.

FIG. 3 shows a tread surface according to the present invention. It is the perspective view and width direction sectional drawing which expanded and showed a part of tread pattern according to this invention. It is the figure which expanded and showed a part of tread pattern according to this invention. It is the figure which expanded and showed a part of tread pattern according to this invention. It is the figure which expanded and showed a part of tread pattern according to this invention. It is the figure which expanded and showed a part of tread pattern according to this invention. It is the figure which expanded and showed a part of tread pattern according to this invention. It is the figure which expanded and showed a part of tread pattern of the prior art example. It is the figure which expanded and showed a part of tread pattern of the prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread surface 2 Circumferential groove 3 Horizontal groove 4 Main block 5-5a Side wall block 6-6a Circumferential sipe 7-7a Width sipe 8 Small block

Claims (3)

  A pneumatic tire having a plurality of main blocks partitioned by a plurality of circumferential grooves extending along a tread circumferential line and a plurality of lateral grooves extending in a tread width direction on a tread surface of the tire, the circumferential direction For at least one of the grooves, a side wall block having a height lower than that of the main block is provided on at least one side of the main block wall adjacent to the circumferential groove, and the side wall block extends in the circumferential direction of the tread. A pneumatic tire characterized by having a plurality of widthwise sipes that are separated from the main block via sipes and extend along the tread width direction.   The pneumatic tire according to claim 1, wherein the main block wall is provided with a plurality of side wall blocks whose height gradually decreases.   The width of the width direction sipes in the side wall block when the width direction sipes are provided in the main block is smaller than the distance between the width direction sipes in the main block. The pneumatic tire according to any one of the above.

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