JPH07101210A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To secure excellent driving and braking performance on the icy or snowy road surface, and improve the cornering quality by providing a block land part which is not communicated to lateral gap communicated to lateral groove, and providing semi-blind longitudinal siping to longitudinally divide the block land part opposite to either of the lateral grooves. CONSTITUTION:Circumferential grooves 2 extending to the circumference of a tread part, and semi-blind longitudinal sipings 6 which demarcate the block land part 4 by the lateral groove 3 extending across the circumferential groove, is communicated to the lateral gap 5 and the lateral groove 3, and is not communicated with the lateral gap 5 and longitudinally divides the block land part 4 are formed on a tread part 1. This constitution secures the rigidity of the block land part 4, can generate a large lateral force by the edge effect, and allows the water film between the road surface and the block land part 4 to be absorbed and discharged outside by the semi-blind longitudinal sipings to remove the water film when the tire is rolled. Thus, excellent driving and braking performance can be secured even on the slippery road and the cornering quality is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a block land portion in which a plurality of circumferential grooves extending around the tread portion and a plurality of lateral grooves extending across the circumferential grooves are defined in the tread portion. The present invention relates to a tread pattern of a studless tire having improved running performance on a snowy and snowy surface, in a pneumatic tire having a lateral gap (sipe or narrow groove) in a block land portion.

[0002]

2. Description of the Related Art A studless tire has a tread portion having a large number of block land portions defined by a plurality of circumferential grooves extending around the tread portion and a plurality of lateral grooves extending across the circumferential grooves. In order to improve the running performance on the snowy and snowy road surface by the edge effect, a plurality of sipes, especially lateral sipes are generally arranged on the land portion of the block.

[0003]

However, when a large number of lateral sipes are arranged in the block, the edge effect is increased, but the circumferential rigidity of the block tends to be decreased.
When the block touches the ground, the collapse deformation becomes large, the ground contact area decreases, and the frictional force with the road surface decreases. As a result, the running performance on the icy and snowy road surface cannot be sufficiently improved, and in addition, there is a possibility that the sipes may be chipped.

Further, the lateral sipe is mainly effective in improving the driving / braking performance, but is not so effective in the cornering performance. Therefore, in order to obtain a well-balanced running performance, it is important not only to arrange the lateral sipes that exhibit driving / braking performance but also to improve the cornering performance while ensuring the circumferential rigidity of the block.

Therefore, it is an object of the present invention to improve cornering properties of a pneumatic tire having a block land portion having a lateral gap while ensuring good driving / braking performance on an icy and snowy road surface.

[0006]

According to the present invention, a tread portion has a block land portion defined by a plurality of circumferential grooves extending around the tread portion and a plurality of lateral grooves extending across the circumferential grooves. However, in this pneumatic tire having a lateral gap in the block land portion, the block land portion communicates with the lateral groove and at least a plurality of semi-blind vertical sipes that vertically divide the block land portion without communicating with the lateral gap. A pneumatic tire characterized by being provided so as to face one of the lateral grooves. Here, the lateral gap means a sipe or a narrow groove. Further, it is preferable to provide a semi-blind vertical sipe that communicates with the lateral gap and does not communicate with the lateral groove.

[0007]

The pneumatic tire of the present invention is provided with a plurality of semi-blinds which are connected to a block land portion having a lateral gap (sipe or narrow groove) and which are vertically connected to the lateral groove without communicating with the lateral gap. By providing the vertical sipes, it is possible to generate a large lateral force due to the edge effect while securing the rigidity of the block land portion.

Here, when the vertical sipes are communicated not only with the lateral groove but also with the lateral gap, the edge effect is enhanced, but the rigidity of the block is reduced, as in the case where many lateral sipes are arranged in the prior art. When the vehicle comes into contact with the ground, the collapse deformation becomes large, the contact area is reduced, the frictional force with the road surface is reduced, and sometimes the sipe is chipped. Therefore, the present invention is semi-blind.

As an unexpected effect, the semi-blind vertical sipes improve braking / driving performance when traveling straight on ice. This is because the vertical sipe is provided facing the lateral groove, so when the tire rolls, the semi-blind vertical sipe on the stepping side absorbs the water film interposed between the road surface and the land portion of the block, This is because it is effectively drained by being continuously drained to the outside.

In addition, by providing a semi-blind vertical sipe in communication with the lateral gap, the road surface and the block land portion (particularly the central portion of the block land portion) are slippery even on slippery road surfaces called Miller Burn. A thick water film between
Since the semi-blind vertical sipe absorbs water and drains from the lateral gap, an excellent water film removing effect can be achieved. Here, if the lateral gap is a narrow groove, the water can be drained more effectively.

[0011]

1 shows a tread pattern of a pneumatic tire according to the present invention, and FIG. 2 shows an enlarged one block land portion of the tread pattern. In the figure, 1 is a tread portion,
Reference numeral 2 is a circumferential groove, 3 is a lateral groove, 4 is a block land portion, 4'is a sub block, 5 is a lateral gap, 6 is a semi-blind vertical sipe, and 7 is a tire equatorial plane. This pneumatic tire has a tread portion 1
And the four circumferential grooves 2 that extend around it and these circumferential grooves 2
It has a block land portion 4 partitioned by a number of lateral grooves 3 extending across the lateral groove 5. The block land portion 4 has a lateral gap 5 and, in addition to this, a lateral gap 5 communicating with the lateral groove 3. There are provided a total of eight semi-blind vertical sipes 6 that vertically divide the block land portion 4 without communicating with and facing both lateral grooves 3 that divide the block land portion 4. In this tire, a sipe was used for the lateral gap 5.

In FIG. 2, the block width of the block land portion 4 is Wb, the length of the sub block 4'formed by dividing the block land portion 4 by the lateral gap 5 (sipe) is Lb, and the groove of the circumferential groove 2 is defined. Let Dc be the depth. The semi-blind vertical sipe 6 has a sipe width Ws of 1 mm or less. Further, the sipe length Ls is preferably 0.06 Lb to 0.70 Lb with respect to the sub-block length Lb at the position where the sipe is arranged. This is because when the sipe length Ls is less than 0.06 Lb, the edge effect due to the semi-blind vertical sipe 6 is weakened and the water absorption / drainage function becomes insufficient. On the other hand, when it exceeds 0.70 Lb, especially on a dry road surface. This is because the deformation of the land portion of the block in the width direction during cornering is increased and the sipes are likely to be chipped. Also, the sipe depth Ds is 0.5 Dc
It is preferably set to 1.0 Dc. This is because if the sipe depth Ds is less than 0.5 Dc, the sipe will be lost by the middle stage of wear and good running performance on ice and snow roads will not be maintained, while if it exceeds 1.0 Dc, the rigidity of the block land area will decrease. Is large.

Regarding the mutual relationship between the semi-blind vertical sipes 6, the sipe width, sipe length, sipe depth, and sipe disposition intervals may be constant, but are preferably varied. Is desirable. Specifically, when the block land portion 4 is divided into a block center portion 8 and both block side portions 9 along the circumferential direction as shown in FIG. 3 (a), the block land portion 4 is arranged in the block land portion 4. The relationship between the semi-blind vertical sipes 6 is that the sipe length is 8
It is preferable that the sipe located in the block is long and the sipe located in the side part of the block is short (Fig. 3 (a)). It is preferable that the sipes located in the portion 9 be shallow (FIG. 3 (b)). Further, the sipe arrangement interval Ys is narrow between the sipes located in the block central portion 8,
It is preferable to widen it between the sipes located on the side portion 9 of the block (FIG. 3 (c)). Regarding the sipe width, the sipe located in the block central portion 8 is wide, and the sipe width is 9
It is preferable to narrow the sipe located at (Fig. 3 (d)).
These preferable examples enhance the effect of removing the water film in the block central portion 8 where the water film is thicker between the road surface and the block land portion, and avoid the sipe chipping which tends to occur in the block side portion 9. Intended to do. These preferable examples can be variously combined as needed, but in short, the sum of the cut volumes of the sipes located in the block central portion 8 can be calculated from the sum of the cut volumes of the sipes located in the side portion 9 of the block. Is also increased.

Regarding the sipe shape of each semi-blind vertical sipe 6, the width, length and depth of the sipe can be changed in the arrangement direction. For example, in order to improve the frictional force on ice at the initial stage of use of the tire, it is preferable to make the sipe depth shallow from the lateral groove 3 to the lateral gap 5 as shown in FIG.

Further, as shown in FIG. 5, the semi-blind vertical sipes 6
It is preferable to arrange each of them so as to be inclined with respect to the tire equatorial plane because the rigidity of the side portions of the block where cracks are likely to occur when a lateral force is input can be secured. If further rigidity is required, the block reinforcement 10 may be formed by shallowing a part of the circumferential groove or the lateral groove adjacent to the block land portion provided with the semi-blind vertical sipe 6 (FIG. 6 (a)). (b)).

Further, in order to prevent cracks in the semi-blind vertical sipe 6, it is desirable that the end of the sipe has a shape in which stress is less likely to concentrate, for example, a so-called flask sipe having a curved shape (FIG. 7 (a) ( b)).

In the case of a tire having a directional pattern,
As shown in FIG. 8, the semi-blind vertical sipes 6 may be provided on the same direction side with respect to the lateral groove and the lateral gap in each sub-block. In addition, as shown in FIGS. 9 (a) to 9 (c),
When utilizing the anisotropy depending on the shape of the block land portion 4 or the arrangement of the lateral gaps 5, it is preferable that the sipe length of the semi-blind vertical sipe 6 is also changed to more effectively exhibit the edge effect. In addition to the single lateral gap 5 having both ends open to the main groove, a plurality of lateral gaps can be arranged when the driving / braking force is more important (FIG. 9).
(c), FIG. 10 (a) (b)). Furthermore, FIG. 9 (c) and FIG.
As shown in (b), considering the rigidity of the block, if there are multiple lateral gaps 5 and the lateral gaps 5 include semi-blind gaps, the sipe length of the semi-blind vertical sipes 6 is The circumferential distance between the lateral gaps or the lateral gaps and the lateral grooves at the positions where they are arranged is defined as the sub-block length Lb.
Should be considered and defined.

The lateral gap 5 should be arranged in the range of -30 ° to + 30 ° with respect to the plane including the tire rotation axis.
It is preferable for obtaining an effective edge effect for generating the braking force. When the lateral gap 5 is a sipe, the sipe width is in the range of 0.3 to 1.0 mm, and the groove depth is the circumferential groove 2 and the lateral groove 3.
It is preferable that the groove depth is less than or equal to.

Further, of the ice and snow road surface, a semi-blind vertical sipe 6 communicating with the lateral gap is further provided for a road surface such as Miller Burn where the water film is thick and exists on the surface (FIG. 11). If the lateral gap 5 is a narrow groove, it is suitable for quickly draining the water existing between the block land portion 4 and the road surface to the outside of the block (Fig. 12 (a)-
(c)).

When the lateral gap 5 is formed by a narrow groove, the groove width is in the range of 1.0 to 5.0 mm, and the groove depth is the circumferential groove 2 and the lateral groove 3.
It is preferable that the groove depth is less than or equal to.

(Test Example) A pneumatic radial tire of size 11R22.5 according to the tread pattern shown in FIG. 1 was experimentally manufactured. The tread portion 1 of this tire is a tire equatorial plane 7
Has four peripheral grooves 2 extending substantially along the horizontal groove 2, a plurality of lateral grooves 3 substantially orthogonal to the peripheral grooves 2, and a large number of block land portions 4 divided by these. In addition, one lateral gap (sipe) 5 that communicates with the circumferential groove 2 and divides the block land portion 4 into two sub-blocks is provided, and in addition to this, a lateral gap (sipe) 5 that communicates with the lateral groove 3 is provided. Is equipped with a total of eight semi-blind vertical sipes 6 that vertically divide the block land portion 4 without communicating with each other, facing both lateral grooves 3 that divide the block land portion 4. The block land portion 4 has a sub-block length Lb of 11 mm and a block width Wb of 30 mm,
The groove depth Dc of the circumferential groove 2 was 20 mm, and the groove depth of the lateral groove 3 was 15 mm. The semi-blind vertical sipe 6 has a sipe width Ws of 0.5 mm, a sipe length Ls of 4 mm (= 0.36 Lb), and a sipe depth Ds of 10 mm.
(= 0.5 Dc). The sipe forming the lateral gap 5 had a sipe width of 0.5 mm and a sipe depth of 10 mm. In each block land row, the block land portions 4 were arranged at an interval of 7 mm and the number of block land portions 4 was 111. The other structures are the same as those of the conventional pneumatic radial tire, and a pair of bead cores, a carcass that is locked by folding back around the bead cores and extends in a toroidal shape, and a carcass crown part 4 It has a structure having a belt in which layers are arranged in layers (not shown). This is Example 1.

The tire prototyped as Example 2 is shown in FIG.
It has the block land part shown in (a), and this block land part 4
In addition, one lateral gap (sipe) 5 communicating with the circumferential groove 2 is provided, and in addition to this, the block land portion 4 is vertically divided without communicating with the lateral groove (sipe) 5 and communicating with the lateral groove 3. Eight semi-blind vertical sipes 6 were provided facing the lateral grooves 3 that partition the block land portion 4, and a total of eight semi-blind vertical sipes 6 were provided. The second embodiment differs from the first embodiment in the sipe length Ls of the semi-blind vertical sipe 6. That is, 4 located in the central portion 8 of the block
The book is 6 mm (= 0.54 Lb) and the four located on the block lateral part 9 are 2 mm (= 0.18 Lb), and the sum of the cut volumes of the sipes located at the block central part 8 is the block lateral part 9
It is larger than the sum of the cut volumes of the sipes located at. However, the sipe depth Ds is 10 mm for each sipe, which is different from that shown in FIG. 3 (b). Structures and shapes other than the above are the same as those in the first embodiment.

The tire prototyped as Example 3 is shown in FIG.
It has the block land part shown in (a), and this block land part 4
Is provided with one lateral gap (narrow groove) 5 that communicates with the circumferential groove 2 and divides the block land portion 4 into two sub-blocks. In addition to this, the lateral groove 3 or the lateral gap (narrow groove) 5 is provided. A total of 12 semi-blind vertical sipes that communicate with each other and terminate inside the block land part to vertically divide the block land part 4 (6 facing the lateral groove, 6 facing the lateral gap (narrow groove)). Equipped with 6. The block land portion 4 has a sub-block length Lb of 11 mm,
The block width Wb is 30 mm, and the groove depth Dc of the peripheral groove 2 is 20 m.
The groove depth of the horizontal groove 3 was 15 mm. The semi-blind vertical sipe 6
Sipe width Ws is 0.5 mm and sipe length Ls is 3 mm (= 0.27
Lb) and the sipe depth Ds were set to 10 mm (= 0.5 Dc).
The narrow groove forming the lateral gap 5 had a width of 2.0 mm and a depth of 10 mm. Further, the arrangement interval of the block land portions 4 in each block land portion row was 5.5 mm, and the number of the block land portions 4 was 111. Structures and shapes other than the above are the same as those in the first embodiment.

A tire made as a trial as a conventional example has block land portions shown in FIG. 13 and each block land portion 4 of the tread portion.
However, it has one lateral gap (sipe) 5 which communicates with the circumferential groove 2 and divides the block land portion 4 into two sub-blocks, but does not have a semi-blind vertical sipe. Except for this point, it had the same structure and shape as in Example 1.

Each of the above-mentioned test tires was mounted on a vehicle, and a test was performed on straight-line braking performance and cornering performance when traveling on a road surface set under two different types of ice and snow conditions. The braking performance during straight running was evaluated by running on the road surface at a speed of 20 km / h, then applying a sudden brake, and measuring the braking distance from the point where the brake was applied to the point where the brake was stopped.
On the other hand, the cornering property was evaluated by rotating a disc-shaped course having a radius of 50 m under the above-mentioned ice and snow condition and measuring the maximum orbital speed (average orbital speed during one round of the course) at this time. Table 1 shows the results of these tests. The values for braking performance and cornering performance when traveling straight ahead in the table are 100
It is shown by the index ratio, and the larger these figures are, the better.

[0026]

[Table 1]

From the test results, Examples 1 to 3 are superior to the conventional example in braking performance on straight roads and cornering on icy and snowy road surfaces. It was revealed that both of the cornering performances were even better.

[0028]

The pneumatic tire of the present invention is provided with a plurality of blocks which are vertically connected to a block land portion having a lateral gap (sipe or narrow groove) and which communicate with the lateral groove and do not communicate with the lateral gap. By providing the semi-blind vertical sipe, it is possible to generate a large lateral force by the edge effect while securing the rigidity of the block land portion. Further, since the semi-blind vertical sipe communicates with the lateral groove, the water film present between the road surface and the block land portion is absorbed by the block when the tire rolls, and the semi-blind vertical sipe on the stepping side absorbs water. The water film is effectively removed by being continuously drained to the outside. In addition, by providing a semi-blind vertical sipe that communicates with the lateral gap, it is possible to intervene between the road surface and the block land portion (particularly the central portion of the block land portion) even on a slippery road surface called Miller Burn. The semi-blind vertical sipe absorbs the thick water film and drains it from the lateral gap, resulting in excellent water film removal effect. Here, if the lateral gap is a narrow groove, the water can be drained more effectively.

[Brief description of drawings]

FIG. 1 is a diagram showing a tread pattern of a pneumatic tire according to the present invention.

FIG. 2 is an enlarged view of the block land portion 4 of the tread pattern shown in FIG.

FIG. 3 is a block land portion 4 of a pneumatic tire according to the present invention.
FIG.

FIG. 4 is a block land portion 4 of a pneumatic tire according to the present invention.
FIG.

FIG. 5 is a block land portion 4 of a pneumatic tire according to the present invention.
FIG.

FIG. 6 is a block land portion 4 of a pneumatic tire according to the present invention.
FIG.

FIG. 7 is a block land portion 4 of a pneumatic tire according to the present invention.
FIG.

FIG. 8 is a block land portion 4 of the pneumatic tire according to the present invention.
FIG.

FIG. 9 is a block land portion 4 of a pneumatic tire according to the present invention.
FIG.

FIG. 10 is an enlarged view of the block land portion 4 of the pneumatic tire according to the present invention.

FIG. 11 is an enlarged view of the block land portion 4 of the pneumatic tire according to the present invention.

FIG. 12 is an enlarged view of the block land portion 4 of the pneumatic tire according to the present invention.

FIG. 13 is an enlarged view of a block land portion 4 of a conventional pneumatic tire.

[Explanation of symbols]

 1 Tread part 2 Circumferential groove 3 Transverse groove 4 Block land part 5 Transverse gap 6 Semi-blind vertical sipe 7 Tire equatorial plane 8 Block center part 9 Block side part

Claims (4)

[Claims] 1. The tread portion has a block land portion partitioned by a plurality of circumferential grooves extending around the tread portion and a plurality of lateral grooves extending across the circumferential grooves, and the block land portion includes: In a pneumatic tire with a lateral gap, the block land portion is provided with a plurality of semi-blind vertical sipes facing at least one lateral groove, which communicates with the lateral groove and vertically divides the block land portion without communicating with the lateral gap. A pneumatic tire characterized by the following. 2. The pneumatic tire according to claim 1, wherein the lateral gap is a sipe. 3. The pneumatic tire according to claim 1, wherein the lateral gap is a narrow groove. 4. The pneumatic tire according to claim 1, further comprising a semi-blind vertical sipe that communicates with the lateral gap and does not communicate with the lateral groove.