JPH04146805A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To avoid the lowering of the block rigidity in a block pattern to which pitch variation whose pattern noise is low is introduced by making the angle between the side wall facing to the cross groove of each block and the normal line of the contour of the surface of a tread larger at a short land section than at a longer land section in the length on the periphery of the tread. CONSTITUTION:The tread of a pneumatic tire is divided into 4 lines of block groups on one side of the central peripheral line O of the tread, i.e., 8 lines of groups on both sides 10a to 13a and 10b to 13b comprising peripheral grooves 1a, 1b to 4a, 4b extending along the central line O and making pairs on both sides, a central peripheral groove 5, and cross grooves 6a, 6b to 9a, 9b connecting each peripheral groove. In this case, the angle between the side wall facing to the cross groove of each block and the normal line of the contour of the surface of the tread(hereinafter called inclined angle) is increased and decreased according to the length of the block. That is, when the inclined angle of blocks 10a1 to 12a1 following to a pitch P1 is taken as gamma, the inclined angle of blocks 10a2 to 12a2 following to a pitch P2 as beta, and the inclined angle of blocks 10a3 to 12a3 following to a pitch P3 as alpha, these values are set to the order of alpha>beta>gamma.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a pneumatic tire having a tread pattern with low tire noise, especially low pattern noise.

Tire noise is generated by various causes, and among them, so-called pattern noise caused by the tread pattern accounts for a large proportion. This pattern noise is caused by the air compressed between the tread contact surface and the road surface rapidly flowing out to the outside of the tread contact surface through the tread grooves, and this phenomenon occurs intermittently. Also called noise.

(Prior Art) This pattern noise can be reduced by imparting so-called pitch variations to the tread pattern.

In other words, the pitch is a structural unit including one horizontally extending groove adjacent to each land section divided by a large number of grooves, and multiple types (3 to 5 types of normal passenger car tires) with different circumferential lengths are used. ) by arranging the pitches randomly or with a certain regularity to reduce pattern noise.

On the other hand, tire treads, particularly for passenger car tires, where emphasis is placed on braking performance, driving performance, and cornering performance, are mainly formed of a block pattern, and this block pattern is defined by circumferential grooves and lateral grooves.

(Problem to be Solved by the Invention) Introducing pitch variations to this block pattern will cause differences in the rigidity of each block. In other words, blocks with a small pitch will have low rigidity, and if a combination of different pitches is used, the Block stiffness becomes uneven. This deteriorates the ground contact during tire transfer, leading to a decline in maneuverability. Further, the rigidity step on the tread circumference becomes the core of uneven wear, and for example, polygonal wear inevitably occurs.

Therefore, an object of the present invention is to propose a tread structure that can avoid a decrease in block rigidity in a block pattern that introduces pitch variations with low pattern noise.

(Means for Solving the Problems) The present invention provides a tread that extends in a toroidal manner between a pair of sidewalls, has a plurality of circumferential grooves extending along the circumference of the tread, and has a cross section in a direction crossing these circumferential grooves. It has a land section divided by a large number of horizontal grooves extending in a V-shape, and the land section is made up of a mixed array of blocks of different types having different lengths along the tread circumference. The tire is characterized in that the angle between the side wall facing the lateral groove of the block and the normal line of the tread surface contour is made larger in the land part having a longer length on the tread circumference of the block than in the land part having a longer length on the tread circumference of the block. It is a pneumatic tire.

Now, FIG. 1 shows the main part of the tread of a pneumatic tire according to the present invention, and this tread is made up of circumferential grooves 1a, lb, which extend along the central circumferential line O of the tread and form a pair on both sides of the central circumferential line O, respectively. 2a, 2b, 3a, 3b.

4a, 4b and a central circumferential line 5 extending on the central circumferential line O, and a lateral groove 6 extending across these circumferential grooves and connecting each circumferential groove.
a, 6b, 7a, 7b, 8a, 8b and 9a, 9
b, the block groups 10a to 13a and 10b to 13b are divided into four rows on one side of the central circumferential line O and eight rows on both sides.

These block groups are divided into a plurality of types of blocks according to pitch variations, that is, in each block group, the length along the tread circumference of the block (hereinafter referred to as block length) also changes according to the plurality of types of pitches.

Block group 1 in one side area of the center circumferential line O of the tread
To explain about 0a-13a, there are three pitch variations to be introduced: P1 to P3 (P+>P2>P3
), each block group is composed of blocks of three types of block lengths corresponding to these pitches. That is, in the block groups 10a to 12a, blocks 10a1 to 12a1 correspond to pitch P1, blocks l0a2 to 12a2 correspond to pitch P2, and blocks 10a3 to 12a3 correspond to pitch P3, respectively.

Furthermore, the angle between the side wall facing the lateral groove of each block and the normal to the tread surface contour (hereinafter referred to as the inclination angle) is increased or decreased depending on the block length. That is, the inclination angle of a block with a short block length is set to be larger than the inclination angle of a block with a long block length.

Specifically, in the block groups 10a-12a, the pitch P
FIG. 2(a) shows a cross section of the horizontal groove between the blocks 10a1 to 12a1 according to the pitch P2 and the blocks 10a2 to 12a2 according to the pitch P2.
2 to 12a2 and blocks 10a3 to 12a with pitch P3
Figure 3(b) shows the cross section of the horizontal groove between the blocks 10as to 12a3 of pitch P3 and the block l of pitch P1.
The cross section of the horizontal groove between Oa l and I2a 1 is shown in the same figure (C
), block 1 according to pitch P1, as shown in FIG.
The inclination angle of blocks 0a and 12a1 is γ, the inclination angle of blocks 10a2 to 12a2 according to pitch P2 is β, and the pitch P
The inclination angles of the blocks 10a3 to 12a3 according to No. 3 are set to α, and the magnitudes of these angles are set in the order of α>β>γ. Here, the inclination angle of each block is preferably in the range of α: 5 to 15 degrees, β: 2 to 12 degrees, and γ: 0 to 10'.

In this illustrated example, the inclination angle of the same block is the same on both sides, but it does not necessarily have to be the same, and as long as the relationship between the inclination angles according to the block length is in accordance with the present invention, even if the same block has an inclination angle. It doesn't matter if the angle is different.

However, in the illustrated example, the inclination angle of the blocks in the block groups 13a and 13b, which are part of the tread shoulder, does not matter.

Furthermore, the width of the lateral groove also changes depending on the pitch, and as shown in FIG. Width is Y and pitch P3
The lateral groove width of the block with pitch P1 and the block with pitch P1 can be set to Z. In that case, the preferred ranges of these lateral groove widths are X: 3 to 12 mm, Y: 2 to 10 mm, and Z: 1 to 8 mm.

Note that the other structure of the tire according to the present invention may be in accordance with the practice of conventional tires.

In other words, the carcass consists of at least one turn-up ply (at most three) wrapped around a bead core from the inside of the tire to the outside of the tire. The belt layer consists of non-extensible cords such as steel cords and aromatic polyamide fiber cords arranged at an angle of 10 to 35° to the equatorial plane of the tire. At least one layer of heat-shrinkable cord, typically a nylon cord, is arranged substantially parallel to the equatorial plane of the tire over the entire width of the main belt layer, which has at least two layers of belts arranged at an angle of . In forming the auxiliary belt layer, each of the auxiliary belt layers is formed by spirally winding a ribbon in which a plurality of cords are arranged along the circumference of the main belt layer. Then, the above-described tread is placed on this belt layer.

(Function) In a block pattern that introduces pitch variation, by increasing the inclination angle of each block for blocks with short block lengths compared to blocks with long block lengths, it is possible to make the block rigidity on the tread circumference uniform. can.

That is, by making the inclination angle of a block with a short block length large, the block rigidity is made higher than that of the conventional type, and by making the inclination angle of a long block length smaller, the block rigidity is made lower than that of the conventional type. This eliminates the difference in rigidity between the rigidity of a block with a short block length and the rigidity of a block with a long block length, and makes it possible to make the block rigidity uniform around the tread circumference.

(Example) A pneumatic radial tire with a tire size of 195/65R14 was manufactured according to the tread pattern shown in FIG. 1.

Pitch variation is pitch P+: 24.3 mm,
Pitch P2: 31.3 mm and Pitch P3: 3
8.3 mm, that is, the pitch ratio P+:P2:Pa is 1
1:9 near, and the width of the horizontal groove between each pitch is
:3.8mm, Y:3.1mm and Z:2.5mm, and the inclination angle of the block corresponding to the pitch is α:
8°, β: 5.5°, and γ: 3°. The circumferential groove width of the tire is la, lb: 8.4mm, 2a, 2b:
3mm, 3a, 3b: 4.8mm, 4a.

4b: 2 mm and the depth was all 8.4 mm, and the depth of the lateral groove was 7.2 mm.

For comparison, the inclination angle of all blocks is 5.5°.
A prototype tire with the same configuration as the above tire was also manufactured.

For each of the above tires, we conducted an actual vehicle feeling test with 2 people riding, 50% city driving with 2 people, 50% high speed driving.
0%, uneven wear test was conducted and evaluated after a mileage of 10,000 km, and the results shown in the table below were obtained. The evaluation is expressed as an index when the measurement result of the comparative tire is set as 100, and the larger the index, the better the result.

(Effects of the Invention) According to the present invention, it is possible to equalize the block rigidity on the tread circumference in a tread with a block pattern that introduces pitch variations, and to create a pneumatic tire with low pattern noise and high uneven wear resistance. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a developed view of the main tread parts of a pneumatic tire according to the present invention, and FIG. 2(a) is a, -a,, b+ b+,
C, -C, and dl-(1, cross-sectional view along the line, same figure (b
) is a cross-sectional view taken along lines a2-a2, bz bz, C2-C2, and d2-d2 in Figure 1, and (C) is a cross-sectional view along lines a2-a2, bz bz, C2-C2, and d2-d2 in Figure 1.
3- A sectional view taken along lines a3, bs b3, C3-C3, and d3ds. 1a to 4a, ib to 4b...peripheral groove 5...
Central circumferential grooves 6a to 9a, 6b to 9b--horizontal grooves

Claims (1)

[Claims] 1. A tread extending in a toroidal shape between a pair of sidewalls, a plurality of circumferential grooves extending along the circumference of the tread, and a cross-section having a substantially V-shaped cross section in a direction crossing these circumferential grooves. A pneumatic tire comprising a land portion divided by a large number of extending lateral grooves, the land portion being a mixture of land portions of different types having different lengths on the tread circumference and arranged along the tread circumference. , A pneumatic tire characterized in that the angle between the side wall facing the lateral groove of the block and the normal line of the tread surface contour is made larger in the short land portion on the tread circumference of the block than in the long land portion on the tread circumference.