JPS63279904A - Pneumatic tyre preventing occurrence of deviated wear - Google Patents

Abstract

PURPOSE:To prevent deviated wear of a tread by a method wherein blocks are divided into a plurality of regions, having different sizes, by means of a plurality of sipes having given depth and inclination angle so that the widths thereof satisfy respective specified relations. CONSTITUTION:Blocks 3 surrounded with circumferential main grooves 1 and lateral grooves 2 are divided into three or more regions 6 by means of sipes 5 with a depth being 0.4-1.0 time as large as the depth of a deepmost groove surrounding the block 3 and an average angle of 45-90 deg. with the circumferential direction of a tyre. The width of region 6a on both ends, each nipped by the sipe 5 and the lateral groove 2, of the regions 6 is set to a value lower than that of an intermediate region 6b nipped on both sides by the sipes 5, and a ratio b/a between the two widths is set to 0.8 or less. An average width (a) of the region 6a at least the one end is set to 25-40% of the length, in the circumferential direction of a tyre, of the block 3. This constitution enables prevention of deviated wear of a tyre.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a tire in which uneven tread wear is suppressed by improving the tread pattern.

[Conventional technology]

In uneven wear where the tread of a tire locally wears out prematurely, each block of the tread in a block pattern tread wears earlier at the rear than at the front end in the rolling direction of the tire, as shown in the cross-sectional view in Figure 3. As shown in Figure 2, so-called heel-and-toe wear, which causes serrated wear, is caused by relative slippage between the tire and the road surface during a load such as braking, and occurs on the tire where the braking force primarily acts. If slippage occurs during braking, a force is applied from the ground to the block on the tire's contact surface in the forward direction of the tire's rolling direction, and the front end of the block in the rolling direction easily deforms toward the front groove, resulting in vertical While the force is relaxed, the rear part of the block is prevented from deforming by the part in front of it, and the vertical force is not relaxed but is relaxed at the front end of the block. As a result of the wrinkling, the load on the rear part increases, causing a difference in the frictional force acting on the front end of the block in the rolling direction and the rear part of the block, resulting in a difference in the amount of wear, resulting in heel-and-toe wear.

As a method to prevent this uneven wear, (a) 45mm
(b) A method of arranging the lateral grooves at an angle of ~90° and providing a bridge in the lateral grooves; (b) A method of narrowing the width of the lateral grooves to close the lateral grooves when the tire makes contact with the ground to prevent deformation of the front end of the block; (C)
Method of reducing the angle of the lateral groove with respect to the main groove, (d)
Proposed methods include reducing the rigidity of the block by shortening the pitch of the horizontal grooves or dividing the block with sipes, and (e) making the cross-sectional shape of the horizontal grooves V-shaped.

[Problem that the invention seeks to solve]

Among the conventional uneven wear prevention methods mentioned above, (a), (b), (e
) deteriorates the drainage performance of the tread pattern and reduces running performance on wet roads. Method (C) narrows the selection range of the tread pattern design, and method (e) has a small radius of curvature of the groove bottom of the lateral groove, and the opening and closing of the groove and the bending of the groove bottom during driving cause
Cracks tend to occur at the bottom of the groove. Further, method (cl) has problems such as decreased wear resistance and increased noise, and all conventional methods have little effect on preventing uneven wear.

Therefore, an object of the present invention is to provide an r-copneumatic tire that suppresses the occurrence of uneven wear and improves wear resistance.

[Another way to solve the problem]

In order to achieve the above purpose, the present inventor has conducted repeated research.1 As a result,
In the rolling direction of the blocks in the tread pattern, by increasing the rigidity of the front end and decreasing the rigidity of the middle part,
The ground pressure distribution when slipping occurs can be made uniform over the entire contact surface of the block, which makes it possible to even out the wear of the block.To this end, the block is divided into three areas using two nearly parallel sipes. The present invention was completed based on the discovery that the rigidity of the central part of the block can be made smaller than that of both sides by dividing the block and making the central area narrower than both sides.

In other words, in a tire equipped with a tread having a block pattern in which blocks surrounded by grooves are arranged in a plurality of rows in the circumferential direction of the tire on the outer peripheral surface of the tread part, a small number of blocks surrounded by grooves are arranged in the circumferential direction of the tire. For blocks arranged in a row, the depth of the deepest groove surrounding the block is 0.
The block is made up of three or more sipes that have an average depth of 4 to 1.0 times and are substantially parallel to each other at an average angle of 45 to 90 degrees with respect to the tire circumferential direction. The area is divided into 1 parts, and each divided area has a different average width in the direction perpendicular to the sipe, and the ratio b/a of the width of the narrowest area to the width of the widest area is 0. .8 or less, and among the areas in which one block is divided by sipes, the average width of at least one end area is greater than the average width of each intermediate area, and the tire circumference of the block to which it belongs The gist of the present invention is a pneumatic tire that suppresses the occurrence of uneven wear, characterized by being 25 to 40% of the length in the direction.

Next, the contents of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a developed view of the tread pattern of the pneumatic tire of the present invention that suppresses uneven wear, and FIG. 2 is a partially enlarged view of the same. In Figure 1, main grooves (1) arranged parallel to the circumferential direction of the tire and lateral grooves (2) connecting the main grooves (1) are shown.
) surrounded by nr niblocks (3) arranged in multiple rows in the circumferential direction of the tire, and ribs (4) along the center line of the tread.
is arranged.

Each block (3) box is provided with a pair of mutually parallel sipes (5) parallel to the lateral groove (2). Sipe (5)
may reach the edge of the block (3) and communicate with the main groove (1), or may be independent within the block (3) without communicating with the main groove (1).

The sipe (5) may be straight or may be curved or bent in the middle. The pair of sipes do not need to be exactly parallel, but only need to be approximately parallel to the adjacent sipe in each portion. Also, there are 3 sipes arranged parallel to each other on one block.
More than one book may be provided.

Due to sipe (5), block (3) has three or more areas (
6). Of the sectioned area, the end area (6) sandwiched between the sipes (5) and horizontal grooves (2) on both sides
a) is narrower than the middle region (6b) sandwiched between sipes on both sides, and the ratio of the width a of the widest end region to the width of the middle region is b/a≦0.8. .

By increasing the width a of the end region (6a) in this way, the rigidity of the end head mounting is greater than that of the middle region, and when a horizontal frictional force is applied to the contact surface of the block, the block rolls. The deformation of the front end in the moving direction is reduced, and the ground pressure of the block is made uniform within the block.

When the ratio b/a of the width of the end region and the middle region becomes larger than 0.8 and approaches 1, the difference in stiffness between the end region and the middle region disappears, and the ground pressure of the block during braking becomes uniform. I can't plan.

Further, it is necessary that the average width a of at least one end region (6a) is 25 to 40% of the length of the block in the tire circumferential direction. If the average width a is smaller than this, the rigidity of the end region will be insufficient, and if the width of one end region is larger than this, the width of the other end region or the width of the middle region will become smaller and the plow of the block will be reduced. There is no way to equalize the ground pressure over the entire surface of the ground.

It is also possible to increase the width of only one of the two end regions. In this case, the width of the wide end region should be at least 1/8 of the length of the block. The mounting direction of this block pattern tire is limited so that the rotation direction is constant.

[Examples and comparative examples]

A tire with a size of 185/70H) Li2 was manufactured with main grooves and lateral grooves having the same shape as the tread pattern shown in Figure 1, and the number and position of sipes in each block were changed.
Attach it to the rim of a JX19 and the front wheel of a rear-wheel drive vehicle, drive it on public roads for approximately 15,000km, and measure the amount of uneven wear. The amount of uneven wear is expressed as the difference between the amount of wear at the front end and the rear end of the block in the tire rolling direction, and the amount of uneven wear of a tire with a tread pattern made of blocks without sipes is
An uneven wear index B was determined by relative comparison as OO. The results are shown in Table 1 and Figure 4. The tread patterns of the tested tires were such that in each block, the areas (6a) at both ends had the same width, and in the case of tires with three or more sipes, the area (6b) in the middle with two or more sipes had the same width. All widths are equal. The depth of the sipe is 0.7 times the depth of the main groove.

In Table 1, A indicates the width of the edge region and the width of the middle region, with (+) indicating a large width of the edge region and (-) - indicating a small width.

As shown in FIG. 4, when the width of both end regions is 25 to 40% of the length of the block and the width of the middle region is smaller than the end region, uneven wear is reduced.

[Brief explanation of drawings]

FIG. 1 is a developed view of the tread pattern of the tire of the present invention;
Figure 2 is a partially enlarged view of the developed view. FIG. 3 is a cross-sectional view of an f-cot tread where uneven wear occurs, and FIG. 4 is a graph showing the relationship between uneven wear and the ratio of the width of the wide area to the length of the block. (1)...Main groove, (2)...Horizontal groove, (
3)...Block, (4)...Rib, (5)...
Sipe, (6)...area.

Claims (3)

[Claims] (1) In a tire equipped with a tread having a block pattern in which blocks surrounded by grooves are arranged in multiple rows in the circumferential direction of the tire on the outer peripheral surface of the tread portion, the blocks are arranged in at least one row of the circumferential arrangement of the blocks. The blocks have an average depth of 0.4 to 1.0 times the depth of the deepest groove surrounding the block, and are mutually arranged at an average angle of 45 to 90 degrees with respect to the tire circumferential direction. The block is divided into three or more regions by providing two or more substantially parallel sipes, and each divided region has a different average width in the direction perpendicular to each sipe, and the width of the narrowest region is different. b and the width a of the widest area b/a is 0.8 or less, and among the areas in which one block is divided by sipes, the average width of the area at at least one end is A pneumatic tire that suppresses occurrence of uneven wear, characterized in that the area is larger than the average width of each area and is 25 to 40% of the circumferential length of the block to which the area belongs. (2) Among the regions belonging to one block, the average width of the frontmost region in the tire rolling direction is wider than the average width of each of the other regions of the same block, and the average width of the frontmost region is A pneumatic tire that suppresses occurrence of uneven wear according to claim 1, wherein the pneumatic tire is designated with a rotation direction that is 1/3 or more of the circumferential length of the block to which it belongs. (3) The average width of the regions at both ends of the block divided by the sipes is larger than the average width of the middle region, and the length of the block in the tire circumferential direction is 25 or more.
A pneumatic tire that suppresses the occurrence of uneven wear according to claim 1, which is 40%.