JPH08324211A - Pneumatic tire - Google Patents

Abstract

PURPOSE: To improve uneven abrasion resistance by reducing shearing force by absorbing a rubber movement by a cargo loading load of a land part such as a block and a rib of a tread pattern by a central part, and preventing heel and toe abrasion and uneven abrasion such as river wear without impairing the other performance such as a wetting road traveling characteristic. CONSTITUTION: In a pneumatic tire having a pattern having a longitudinal groove such as a circumferential directional main groove and a lateral groove crossing this in a tread part of a tread and a land part such as a block 3 and a rib defined by these grooves, a large number of small blocks 5 surrounded by narrow groove-shaped slits 4 having a depth of 0.3h to 0.5h of a depth (h) of an adjacent longitudinal groove are arranged in the land part so as to form a continuous shape or a group 50 on the inside from the edge of the land part.

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 mainly for heavy loads, which is excellent in uneven wear resistance.

[0002]

2. Description of the Related Art A so-called block pattern having a plurality of vertical grooves such as main grooves and sub-grooves in the tire circumferential direction and a large number of transverse grooves intersecting with the grooves, and having a large number of blocks defined by these grooves. In a tire, uneven wear caused by running is referred to as heel-and-toe wear that causes a difference in wear mainly at both circumferential ends of the block.

That is, looking at the wear state of the block,
Due to the relationship between the motion of the block during running and the deformation due to the load, the wear is more severe on one end side in the running direction and less on the other end, resulting in wear that is inclined in a sawtooth cross section as shown in FIG. 8. The wear of the block (30) in the inclined state is called heel and toe wear.

Such wear will be described with reference to FIG.
When a vertical load is applied to the block surface of the tire tread, the shearing force that accompanies the movement of rubber that deforms and moves in all directions from the center of the block to the sides forming the periphery of the block due to this load Since f1 and the shearing force f2 due to the circumferential difference of tire rotation, driving force, braking force, etc. act, the shearing force f1 is larger toward both ends in the tire circumferential direction and opposite to each other. +
f2 and f1-f2 on the other end side, the absolute values of the shearing force differ, and as a result, the friction force between the road surface and the tread tread portion is easily exceeded between the one end side and slippage occurs. It is easy and has a large amount of wear, and at the other end, the shearing force does not easily exceed the frictional force between the road surface and the road surface.

When such wear occurs, vibration and noise are generated, the steering stability is deteriorated, and the wear is further facilitated.

[0006] As a countermeasure against this, in general, a method of increasing the rigidity in the circumferential direction of the block by shallowing a part of the lateral groove that defines the block, or a straight line in the circumferential direction of the block to move in and out in the width direction The method of reducing it is adopted.

However, in the case of the method of making the lateral groove shallow, the drainage performance of the tread portion is impaired, so that the lubrication road running characteristic as an all-weather tire is lost.
Further, at the initial stage of wear, the blocks are continuous in the circumferential direction to form ribs, and as a result, the traction and braking properties deteriorate, and the tire performance on wet roads is mainly impaired. Even when the blocks are arranged in a straight line in the circumferential direction, the traction property and the braking property are deteriorated. Therefore, designing to satisfy all of these characteristics is extremely difficult.

Further, in the case of a tire having a so-called rib pattern in which the lateral groove is originally extremely shallow or has no lateral groove, the side end portions of the rib along the longitudinal groove in the tire circumferential direction are selectively worn. As a result, stepwise wear that is continuous in the circumferential direction, that is, so-called river wear, occurs.

As a countermeasure, for example, Japanese Patent Laid-Open No. 2-883.
In JP 11 publication, a part of the tread is provided with an uneven wear preventing portion due to a stepped region that makes sliding contact with the road surface, so that shearing force acting on the surface, which is one of the causes of uneven wear, that is, rubber deformation under load is applied. The shearing force of the surface involved and the shearing force associated with the circumferential difference, the driving force, the braking force, etc. are absorbed by positively sliding the latter shearing force in the stepped region, thereby preventing uneven wear. Is proposed.

However, in this case, since the ground contact area is reduced, the wear resistance is impaired. If the wear resistance is to be ensured, the rubber material of the tire is upgraded or the ground contact width of the tire is reduced. It is necessary to increase the size, which results in high cost.

Further, it has been considered to provide a narrow groove in the circumferential direction along the shoulder ground contact width of the shoulder rib, but even if it has the effect of preventing uneven wear of the river rib of the shoulder rib, it can be used in areas other than the shoulder portion. It is not effective in preventing uneven wear in the part and is not satisfactory.

Further, it has been proposed to provide a continuous or discontinuous groove or recess along the longitudinal groove in the tire circumferential direction at the end of the rib closer to the center, but the rib end is more damaged than uneven wear. It is unpractical because it is easily received, cracks, cracks, and the like are likely to occur, and uneven wear starting from that may occur.

The present invention has been made in view of the above, and in a tire having a block pattern or a rib pattern, uneven wear caused in land portions of blocks, ribs, etc. deteriorates wet road running performance, which is contrary to this. The purpose of the present invention is to prevent the above-mentioned problems, to secure the characteristics such as drainage, drivability, and braking performance required for an all-weather tire, and to improve the uneven wear resistance.

[0014]

SUMMARY OF THE INVENTION According to the present invention, a longitudinal groove in the tread surface and a transverse groove intersecting with the tread, and a block or rib defined by these grooves or a combination of both of them are provided. In a pneumatic tire of a pattern having a land portion, in order to solve the above problems, in the land portion, adjacent vertical grooves (main grooves and main grooves when there are sub-grooves narrower than the main grooves) A large number of small blocks surrounded by narrow groove-shaped slits with a depth of 0.3h to 0.5h are arranged continuously or in groups inward from the edge of the land. It is characterized by

In the above, it is preferable that the slits surrounding the small blocks forming a continuous or group form a part of the slits that communicate with the slits surrounding the adjacent small blocks.

Further, as described above, in the case where the respective slits are communicated with each other, it is preferable that a part of the slits is communicated with a groove defining a land portion such as a block or a rib so that the drainage performance and the wet road running performance can be improved. Is more preferable from the viewpoint of improvement of

[0017]

[Practice] According to the pneumatic tire of the present invention described above, a large number of small blocks surrounded by narrow groove slits are continuously or in a land portion such as a block in a block pattern or a rib in a rib pattern. Since they are provided in groups, each slit absorbs the rubber trying to move to the end of the land, that is, each side forming the block or rib when a vertical load is applied to the land. Thus, the generation of shearing force can be suppressed.

That is, when the vertical force acts and the land is bent and the rubber moves, a part of the rubber escapes into the space defined by the slits surrounding a large number of small blocks, and the edges of the land, that is, the sides forming the blocks or ribs. The amount of rubber moving to the ground is reduced, and as a result, the shear force generated on the land surface such as blocks and ribs due to the vertical load is reduced.

When the tip force becomes small, the difference between the added and subtracted values of the driving force in one direction at the block ends facing each other in the circumferential direction in the block pattern, the shearing force in the circumferential direction due to the braking force, and the like becomes small. Since the effect on the frictional force between the road surface and the tire tread portion is small and the difference in slip, that is, the difference in wear is small, uneven wear can be suppressed.

When the land portion is a rib, the rib end portion slides in the tire rotation axis direction due to the shearing force at the rib width direction end portion, which becomes larger toward the rib end portion. At this time, this slippage causes a circumferential driving force. Since the friction coefficient of the frictional force that opposes the circumferential shearing force due to the braking force is reduced, the rib end with a large widthwise slip also slides in the circumferential direction, promoting friction at the rib end and producing river wear. To tighten. Therefore, when the shearing force becomes smaller, the slip in the width direction becomes smaller, and the friction coefficient of the frictional force that opposes the shearing force in the circumferential direction does not become smaller. Since there is no particular increase compared to the parts other than the end part, as a result, the rib end wears ahead,
So-called river wear, which is less likely to cause side wear.

In particular, when a load is applied, the land cross-section of the portion closer to the land surface is generally larger toward the base side.
Although the amount of rubber movement is larger than that on the base side of the land part, the slit surrounding the small block has a depth of 0.3h to 0.5h relative to the depth h of the vertical groove adjacent to the land part, and the small block is on the surface side. Since it is provided on the surface of the land portion, the followability and absorption of the rubber movement on the surface of the land portion are increased, while at the base of the land portion, sufficient rigidity for suppressing the movement of the entire land portion can be secured. Further, the narrow groove-like slit is easily closed by the deformation of the small block, and it is possible to prevent the decrease in rigidity from further progressing, and to secure an appropriate rigidity.

Further, since the small blocks are provided inward from the edges of the land portion such as blocks and ribs and have a blank portion between the group of small blocks and the groove in the periphery thereof, the rubber on the center side of the land portion is provided. Even if the movement is absorbed before it affects the land edge and mechanical strength can be maintained moderately, a strong braking force or drive is applied to the land surface, and the ground contact pressure is biased to one end side in the circumferential direction, The rigidity of the block is kept large at the end portion, and it is possible to prevent the bending from increasing.

Further, due to the water film destruction action due to the presence of a large number of slits surrounding a large number of small blocks in a net-like manner, the running performance on wet roads is improved.

In particular, when the slits surrounding the small blocks are formed so as to communicate with the slits of the adjacent small blocks in part, as in claim 2, the slits may have a mesh shape. Therefore, the movement of water becomes smooth, the drainage property and the water film destruction effect are excellent, and the wet road running performance is further improved.

When a part of the slit is communicated with a groove defining a land portion such as a block as in claim 3, the fluid flows from or into the slit.
Outflow becomes possible, drainage performance during traveling on a wet passage is further improved, and the effect of improving traveling performance on a wet passage becomes greater.

In the present invention, the depth of the slit surrounding the small block is set to 0.3 h to 0.5 h, which is the depth h of the vertical groove, because the rigidity of the small block becomes greater when the depth becomes deeper than 0.5 h. As a result, the rigidity of the land portion such as the block is weakened, the effect of preventing uneven wear is rather reduced, and the wear resistance and mechanical strength are reduced.
This is because if the depth is shallower, the effect of preventing uneven wear due to absorption of rubber movement becomes smaller.

For example, the rubber movement due to the load of the block is generally 7 to 10% of the block volume, and the rubber movement amount which causes the shearing force of the tread portion is 3 to half of the tread portion side, that is, 1/2 of the entire block. It is about 5%. Therefore, it is preferable that the slits have the above-mentioned depth to form a small block surrounded by the slits on the surface.

If the groove width of the slit is too large,
When the rubber flexes, it is not easily blocked, and the rigidity of the small block surrounded by the slits is weakened. As a result, the effect of preventing uneven wear is rather reduced, and the mechanical strength is weakened. If the groove width is too small, the effect of preventing uneven wear due to absorption of rubber movement is reduced. Therefore, the preferable range of the groove width of the slit is 0.4 to 1.3 mm, particularly preferably 0.6 to 1.0 mm.

It is to be noted that the slits of the small block group for each block in the block pattern are set to have the above-described groove width so that the total volume is 4 to 6% of the block volume. It is preferable in terms of the effect of uneven wear and improvement of running performance on wet roads.

Also, the size of the one small block,
That is, the surface area (top surface area) is not particularly limited,
If this surface area is too large, the escape area of the rubber is small and the effect of absorbing and moving the rubber is small, and the effect of preventing uneven wear is also small. Further, if the surface area is too small, the rigidity and strength of the small block will decrease. Therefore, in practice, about ²⁰ to 60 mm ² is preferable in relation to the depth of the slit.

The shape of the small blocks may be circular or elliptical in a plane, but hexagons, squares, or other polygonal shapes may partially cover each slit of the small block group. It is particularly suitable for common communication, and the small blocks can be adjacent to each other in a well-balanced manner via slits having a constant groove width.

[0032]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a partially developed view showing the pattern of the tread portion of one embodiment of the pneumatic tire of the present invention, and FIG.
FIG. 3 is an enlarged plan view of one block, and FIG. 3 is an enlarged sectional view.

As a pattern of this tread portion, a plurality of main grooves (1) are formed on the tread surface as longitudinal grooves in the tire circumferential direction.
And a lateral groove (2) extending in the cross direction from the main groove (1) is provided, and a large number of blocks (3) are arranged in the tire circumferential direction as land portions defined by these grooves. A so-called block pattern is formed.

Each block (3) contains the block (3)
0.3h to 0.5 of the depth (h) of the main groove (1) adjacent to
At a depth of h, groove width 0.4-1.3 mm, preferably 0.
A large number of small blocks (5) each having a planar hexagon surrounded by narrow slits (4) in the range of 6 to 1.0 mm are formed into a group (5).
0), the blocks (3) are arranged in a dense state in the vicinity of the central portion slightly inward from the edge. Usually, the surface area of the small blocks (5) is set to 20 to 60 mm ² , and the number of the small blocks (5) and the grooves of the slits (4) are set so that the total volume of the slits (4) is 4 to 6% of the block volume. Width, depth, etc. are set.

In the small block group (50), the slits (4) surrounding each small block (5) are slits (4) surrounding the adjacent small blocks (5) as shown in an enlarged view in FIG. The slit (4) in the small block group (50) communicates with a part of the
The whole has a hexagonal mesh shape.

According to the pneumatic tire of this embodiment, when the block (3) is flexed under vertical load and the rubber moves, the rubber of the small block group (50) is formed by the gaps of the slits (4). The movement is effectively absorbed on the center side of the block (3) and is less likely to be transmitted to the circumferential end of the block, the shearing force generated on the surface of the block by the vertical load can be reduced, and the heel and toe wear can be prevented from occurring.

Moreover, the small block (5) is the block (3).
On the front surface side, sufficient rigidity can be ensured on the base side, and since the small blocks (5) are located slightly inward from the edges of the blocks, the small blocks (50) are closer to the blank part than the peripheral part. The rigidity is kept large at the end portion, and even when the ground contact surface pressure is biased to one end side in the tire circumferential direction, the bending is not increased and sufficient strength can be secured.

Further, since the slits (4) communicate with each other in a mesh shape, the drainage property and the water film destruction effect are good, and the wet road running performance is improved.

Each small block (5) of the small block group (50) has a small space (S) between the slits (4) and (4) surrounding the small block (5) as shown in FIG. However, in practice, it is preferable that they are communicated with each other as described above.

In the embodiment shown in FIGS. 4 and 5,
Similar to the above-described embodiment, each block (3) is provided with small blocks (5) surrounded by slits (4) so as to form a group (50), and each slit () in this small block group (50) is formed. 4) communicated with each other, a part of the slit (4) is formed by a communicating slit (6) having the same depth and width as the slit (4), which defines a block (3), for example, in the drawing. The case where the main groove (1) and the lateral groove (2) are communicated with each other is shown. As a result, the drainage property and the water film destruction effect by the large number of mesh-shaped slits (4) are further improved.

In the embodiment of FIG. 7, the blocks (3) defined by the main groove (1) and the lateral groove (2) in the tire circumferential direction are arranged in a substantially straight line in the tire circumferential direction, and the left and right sides are arranged. 7 shows an example in a pattern having a rib (7) continuous in the tire shoulder portion in the circumferential direction.

In this embodiment, each block (3)
The small blocks (5) surrounded by the slits (4) similar to the above are arranged so as to form a group (50) continuously in a substantially H shape, and the ribs (7) of the shoulder portion have the same shape. Small blocks (5) surrounded by a large number of slits (4) of depth and groove width are formed in a group (51) that are continuous in the circumferential direction slightly inward from the edges of the ribs (7) and are partially concentrated. )
It is arranged so that

Also in the case of this embodiment, uneven wear (heel and toe wear) of each block (3) can be prevented, and the rib (7) is bent by the vertical load of the shoulder rib (7). When the rubber moves, the slit (4) surrounding each small block (5) on its surface part
With this, the rib (7) can be effectively absorbed, and excessive lowering of rigidity and deformation of the rib (7) can be suppressed, and uneven wear (river wear wear) that is continuous in the circumferential direction at the edge of the rib (7) can be prevented. .

In this embodiment, the small blocks (5) arranged on the ribs (7) are circumferentially continuous as shown in the figure, and a large number of them are intermittently arranged circumferentially. It is also possible to carry out.

In each of the above embodiments, it is possible to arrange a plurality of small block groups (50) in one block (3). Further, the small blocks (5) having different shapes and sizes (surface areas) may be arranged in one small block group (50) for implementation.

The small block (5) is replaced with the block (3)
The ribs and ribs (7) are formed so that they are distributed so that they approach the side near the midpoint of each side forming the main part of the outer peripheral contour shape of the land and away from the corners. If left, the rubber movement to the outside can be effectively suppressed.

Further, in each of the above-mentioned embodiments, the small blocks (5) are provided on the land portions of all the blocks (3) and ribs (7), but the shoulder blocks (3) and ribs (7) are provided. It is also possible to dispose the above-mentioned small block (5) only in ().

Table 1 below shows the uneven wear resistance, wet road braking property, and wear durability of the example tires of the present invention (Examples 1 to 6) and the comparative example tires (Comparative Examples 1 to 3). A comparison is shown.

The tires of Examples 1 to 6 and Comparative Examples 1 to 3 were the following tires based on the block pattern of FIG. 1, and were tested by the following test method.

Tire size: 11R22.5 14PR Depth of main groove h: 17 mm Rim: 22.5 × 7.00 Air pressure: 700 kPa Controlled by giving a given braking force, driving force, speed, etc. to the uneven wear resistant tire With a wear tester that can be used, the road surface (running surface of the tester) is a fine safety walk, and 20,000k
The amount of step difference in heel and toe wear that occurred in the tire during m running was measured, and the value of the conventional tire was set as 100 and shown as an index. The smaller the number, the less uneven wear.

Wet road braking property A running speed of 3 on a test road surface maintained at a constant wettability.
The distance until the axle comes to rest when the vehicle enters the test road at a speed of 0 km / h and is suddenly braked
It was displayed as an index of 0. The smaller the value, the better the result.

Abrasion Durability With respect to the uneven wear resistance measuring tire, the tire weight before and after the test was accurately measured, and the wear amount was calculated from the difference. The value of the conventional tire was set to 100 and displayed as an index. The smaller the value, the better the result.

[0054]

[Table 1] As is clear from the above, in any of Examples 1 to 6, the uneven wear resistance and the wet road braking property are improved, and the wear durability is also good, as compared with the tire of Comparative Example 3 having no small block. Met. Particularly, as in Examples 1 to 4, the width of the slit is 1 mm or less, and the surface of the small block is 20 to 60 mm ^2.
With respect to the above, the uneven wear resistance could be significantly improved.

On the other hand, when the slit depth is smaller than the main groove depth h of 0.3 h (Comparative Example 1),
The one having a small effect of preventing uneven wear and having a length of more than 0.5 h (Comparative Example 2) had a problem in wear durability.

[0056]

As described above, according to the present invention, a fine groove shape having a depth h of 0.3h to 0.5h of adjacent vertical grooves is formed on the land portion of the block or rib in the block pattern or rib pattern. Since a large number of small blocks surrounded by the slits are arranged continuously or in groups, the heel and heel can be maintained without impairing drainage performance, braking performance, that is, other performance such as wet road running performance. Uneven wear such as toe wear and riverwear wear can be prevented, and uneven wear resistance can be greatly improved. Further, this makes it possible to prevent the generation of noise and vibration due to uneven wear, and the wear durability is not impaired.

Particularly, in the case where the slits surrounding the respective small blocks are communicated with each other as in the invention of claim 2, the invention further comprises:
When the slit is opened to communicate with the groove that defines the land portion as in the invention of (1), it facilitates the movement of water between the surface of the block or rib and the road surface in the pattern through the slit, and drainage and water The membrane breaking effect is improved, and the wet road running performance is improved.

[Brief description of drawings]

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

FIG. 2 is an enlarged plan view of one block portion of the above.

FIG. 3 is an enlarged cross-sectional view taken along the line AA of FIG.

FIG. 4 is a partial development view showing a tread pattern of another embodiment.

FIG. 5 is an enlarged plan view of one block portion of the above.

FIG. 6 is an enlarged plan view of one block portion of the embodiment in which the slits of each small block are arranged in an isolated state.

FIG. 7 is a partial development view showing a tread pattern of still another embodiment.

FIG. 8 is a cross-sectional explanatory view of heel and toe wear.

FIG. 9 is an explanatory diagram of a state where a block is bent and a shearing force is generated due to a load.

[Explanation of symbols]

 (1) Main groove (2) Lateral groove (3) Block (4) Slit (5) Small block (6) Communication slit (7) Shoulder rib (50) (51) Small block group

Claims (3)

[Claims] 1. A pattern air having a circumferential longitudinal groove and a lateral groove intersecting with the tread surface, and a land portion formed by one or a combination of blocks and ribs defined by these grooves. In the filled tire, the land portion has a depth h of 0.3 h to 0.
A pneumatic tire, characterized in that a large number of small blocks surrounded by narrow groove-shaped slits having a depth of 5 h are arranged continuously or in groups inward from the edge of the land portion. 2. The slits surrounding the small blocks forming a continuous shape or a group are formed so as to communicate with the slits surrounding the adjacent small blocks in part in common. Pneumatic tire described. 3. The pneumatic tire according to claim 2, wherein the slits communicate with each other, and a part of the slits communicates with a groove defining a land portion such as a block or a rib.