JPH0485109A - Pneumatic tire suppressed in partial wear - Google Patents

Abstract

PURPOSE:To suppress partial wear caused by difference in the pitch length of blocks by setting the height of the independent blocks formed at a tread being partitioned by circumferential main grooves and lateral grooves in such a way that the shorter the block is, the lower its height is. CONSTITUTION:A tread part T is provided with independent blocks B1-B3 partitioned by circumferential main grooves 1 to 1-3 and lateral grooves obliquely intersecting these circumferential grooves. In this case, the circumferential spacing of the lateral grooves 2 are changed to form three kinds of blocks, that is, a long block B1 of a large pitch P1, a medium block B2 of a medium pitch P2 and a short block B3 of a small pitch P1. The height of the respective blocks B1-B3, that is, the distance from the tire center to the surface of the respective blocks is so set that the block B1 is D/2, for instance, then the block B2 is D/2-alpha1 and the block B3 is D/2-alpha2 under the setting of alpha1<alpha2, thus the shorter the block is, the lower its height is set.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to the improvement of a pneumatic tire with a tread pattern, and more particularly, to the improvement of a pneumatic tire with a tread pattern. This relates to a pneumatic tire that effectively suppresses air pressure.〇(Prior art) Generally, the tread portion of pneumatic tires used for high-speed running has a pneumatic tire that satisfies required performance such as high-speed durability, drainage performance, and noise reduction. Various block patterns are formed for this purpose.

That is, FIG. 1 shows a developed view of the tread of a typical pneumatic tire, and the tread surface T has a plurality of circumferential grooves on both sides of a circumferential main groove (center groove) 1 along the circumferential center line. Grooves 1-2, 1-3 are provided parallel to the circumferential direction of the tire, and a large number of lateral grooves 2 are inclined toward the circumferential direction in a direction that intersects with these circumferential grooves, and are arranged at predetermined intervals. Many block rows 3-1.3-2.3-3.3
-4 is formed.

In addition, in order to suppress pattern noise generated from the lateral grooves 2, the circumferential spacing of the lateral grooves 2 is changed, and blocks with a large pitch length P1 (hereinafter referred to as long blocks) are A block B2 with a medium pitch length P2 (hereinafter referred to as a medium block) and a block B3 with a small pitch length P3 (hereinafter referred to as a similar block) are formed, and these are randomly or A so-called pitch variation pattern, which is arranged with a certain regularity, is known.

As shown in FIG. 3, the conventional pneumatic tire with pitch variations has a cross-sectional pattern (A-A line cross-sectional diagram in FIG. 1) that is a perfect circle when the tire is viewed from the axial direction. Each block B1, B
The heights of 2 and B3 were all constant.

(Problem to be Solved by the Invention) However, in the above-mentioned conventional pneumatic tires, each of the tires B1, B2 and B having different pitch lengths
Due to the fact that all blocks 3 have the same height, when a certain load is applied to the tire and the tire is driven, the amount of shear deformation within the ground contact surface of each block becomes significantly non-uniform.

In other words, the shearing force of the blocks acts in opposite directions in the tire rotational direction and tire travel direction within the contact patch, so during load transfer, the shearing deformation in the short blocks is large, and conversely, the shearing deformation in the long blocks is large. Deform or become smaller.

In addition, the wear work of the block during tire load transfer is expressed as the product of the amount of slippage based on the ground pressure and the amount of shear deformation, but compared to the amount of slippage in a long block whose circumferential block rigidity is large, Since the amount of slippage of the short and small blocks, which originally have low circumferential block rigidity, increases, the amount of wear work on the short blocks increases under the same ground contact conditions, and uneven wear in that portion becomes apparent.

Therefore, in the above-mentioned conventional pneumatic tires, as the mileage increases, uneven wear of the short blocks progresses, and in particular, some blocks on the tire shoulder tend to develop an uneven surface at an early stage. This tends to lead to vibrations and noise, which further impairs steering stability.

Therefore, an object of the present invention is to solve the problems of the conventional pneumatic tires described above.

Therefore, an object of the present invention is to provide a pneumatic tire that effectively suppresses uneven wear caused by differences in pitch length of blocks.

[Structure of the Invention] (Means for Solving the Problems) That is, the pneumatic tire of the present invention includes a pair of sidewalls and a tread extending between both sidewalls in a toroidal manner. It includes a plurality of circumferential grooves extending parallel to each other, a large number of lateral grooves extending across the circumferential grooves, and an independent block divided by the groove group, the block having a circumferential length. A tire having at least two types of pitch, long and short, is characterized in that the height of the blocks is configured such that the height of the short blocks is lower than that of the long blocks.

(Function) According to the pneumatic tire of the present invention, in a tire in which the blocks have at least two types of pitches in the circumferential direction, long and short, the height of the blocks is configured to be lower than that of the long blocks compared to the short blocks. Therefore, the ground pressure and shear deformation amount in the short block during load transfer of the tire are reduced, the amount of wear work in this portion is reduced, and the difference in the amount of wear with the long block is equalized.

Therefore, the pneumatic tire of the present invention advantageously suppresses uneven wear, particularly heel-and-toe wear, and as a result, a high-speed tire that effectively suppresses vibrations and noise caused by uneven wear is obtained. It has ideal performance as

(Example) Hereinafter, examples of the pneumatic tire of the present invention will be described in detail according to the drawings.

FIG. 1 is a developed view of a tread portion of a pneumatic tire as an example of the tread portion, and FIG. 2 is a cross section taken along the line A--A in FIG. 1.

Although parts other than the tread portion are not shown in FIG. 1, the parts other than those shown, such as the radial carcass, belt layer, and sidewalls, have a well-known structure.

In Fig. 1, the tread portion T includes a circumferential main groove (center groove) 1 along the circumferential center line, and two circumferential grooves 1-1 and 1-2 on both sides of the circumferential main groove (center groove) 1 extending in the axial direction of the tire. They are provided in a straight line and endlessly parallel to the circumferential direction at predetermined intervals, and on the other hand, they are inclined toward the circumferential direction from the center of the tread portion T in a direction that intersects with each of the above-mentioned circumferential grooves, and are provided at predetermined intervals. A large number of lateral grooves 2 are provided, and independent blocks B1, B2, B3, . . . are divided by groups of these grooves.

Note that the groove width and depth of the circumferential main groove 1, circumferential grooves 1-2 and 1-3 are generally wider and deeper than those of the lateral groove 2.

Further, the lateral grooves 2 can be provided so as to be inclined at an appropriate angle to the circumferential direction from the center of the tread to the tread ends, usually at an angle of 50 to 70 degrees.

The independent blocks in each block row 3-1.3-2.3-3 and 3-4 are, for example, block row 3-
4 as a representative example, by changing the circumferential interval of the lateral grooves 2, the pitch length P can be changed in this example.
It consists of three types: a long block B1 with a large pitch length P2, a medium block B2 with a medium pitch length P2, and a short block B with a small pitch length P3, and these are arranged randomly or with a certain regularity to form a pitch variation pattern. As a result, pattern noise generated from the lateral grooves 2 is suppressed.

Now, in the pneumatic tire of the present invention, as shown in Fig. 2, when the tire is assembled on a used rim and filled with internal pressure for use, the heights of each block B1, B2, and B3 are set to be shorter than the long blocks. The most distinctive feature is that the block is constructed to be lower, thereby suppressing uneven wear.

That is, in FIG. 2, if the dimension from the tire center O to the surface of the long block B1 is D/2, the dimension from the tire center O to the surface of the middle block 82 is D/2-α1, and from the tire center 0 The dimension to the surface of short block 83 is D/2
-α2, α1 and α2 are each 0.05 to 0.15
1+w and a range of 0.15 to 0.25 m+s, and a step is formed in the height of each block B1, B2, and B3.

In this way, by arranging the blocks by the distances α1 and α2 according to the circumferential length of the blocks, that is, by increasing the distance α as the length becomes shorter, the short block B3 and the medium block are The ground pressure and the amount of shear deformation at B2 are reduced, and the amount of work within the ground contact surface of the block is made uniform as a whole, and as a result, the uneven wear can be effectively suppressed.

Next, the structure and effects of the pneumatic tire of the present invention will be explained in more detail using test examples.

(Test example) Tire size: 185/70R14RH79A1 Rim used: 5-1/2JX14, Air pressure used: 20 kg
The block pattern shown in FIGS. 1 and 2 described above is formed on the tread portion of the radial tire of /
This tire was evaluated.・The other structures and manufacturing conditions of the tire, such as the radial carcass and belt layer, are the same as those of conventional tires, so details will be omitted.

That is, in FIG. 1, the width of the tread portion T: 144'
m+s, groove width of circumferential main groove 1: 8.0 length, depth 2 8.1
+IIm, groove width of circumferential groove 1-2.1-3 25° 4mm
, Depth: '8. 1mm, width of horizontal groove 2: 4.0m
A block pattern was formed with l11 depth: 6.6wn.

Then, the circumferential length of each block is Bl: 36°4w
S B2: 29.7mm, B3: 23.1+n, and the height of each block is B1: 6.6mm, B2:
6.5mm, B3: By setting it to 6.4mm,
A tire of the present invention was obtained. Note that each block had the same height throughout in the length direction.

On the other hand, for comparison, the height of each block is all 6゜6m.
A conventional tire was obtained in the same manner as above except that m was kept constant.

The abrasion durability of these two types of tires was evaluated under the following conditions, and the results are shown in the following table.

(Evaluation method) Tire load: 430 kg, internal pressure: 2. The vehicle equipped with the Okg/cd condition was subjected to an actual vehicle driving test, and the tire block wear ff1 (unit: dragon) was measured after 20,000 miles of driving, and from this measurement value, the heel and toe (
H/T) Wear index evaluation (index evaluation when long blocks are set as 100; larger index means less wear).

(Hereinafter, blank spaces) From the results shown in the table, it is clear that the pneumatic tire of the present invention effectively suppresses uneven wear (heel-and-toe wear) particularly in the medium blocks and short blocks.

[Effects of the Invention] As explained in detail above, the pneumatic tire of the present invention is a tire in which the blocks have at least two types of pitches in the circumferential direction, long and short. Since the comparative short block is configured to be low, the ground pressure and shear deformation in the short block during tire load transfer are reduced, and the amount of wear work in this area is almost uniformized, thereby Uneven wear of the block can be advantageously suppressed.

[Brief explanation of drawings]

FIG. 1 is a developed view of the tread portion of the pneumatic tire of the present invention;
FIG. 2 is an explanatory diagram of a cross-sectional pattern of a tire taken along line A--A in FIG. 1, and FIG. 3 is an explanatory diagram of a cross-sectional pattern of a conventional pneumatic tire viewed from the radial direction. T...Tread portion 1......Circumferential main groove 1-2...Circumferential groove 1-3...〃 2...... ...Horizontal groove 3-1...Block row 3-2-=7゜3-3...〃 3-4...〃 Bl...Long block B2... Medium 〃 B3... Short 〃

Claims (1)

[Claims] A pair of sidewalls and a tread that spans both sidewalls are connected in a toroidal manner, and the tread has a plurality of circumferential grooves that extend parallel to each other at predetermined intervals, and a plurality of circumferential grooves that extend across these circumferential grooves. lateral grooves, and independent blocks separated by the groove groups,
A tire in which the blocks have at least two types of pitch, long and short, in the circumferential direction, characterized in that the height of the blocks is configured such that the height of the short blocks is lower than that of the long blocks. Included tires.