JPH04244402A - Neumatic tire with reduced noise - Google Patents

Abstract

PURPOSE:To uniform surface pressure between respective blocks to reduce running noise to improve partial abrasion resistance by making depth of a lateral groove with a short pitch shallower than that of a lateral groove with to a long pitch in the tread circumferential surface of a tire. CONSTITUTION:The tread has the center circumferential groove 1 extending on the center circumferential line O thereof, and circumferential grooves 2a, 2b and 3a, 3b extending along both sides thereof and making a pair. Moreover, ribs 6a, 6b are defined on both sides of the center circumferential groove 1 by lateral grooves 4a, 4b and 5a, 5b extending to the crossing direction of these circumferential grooves and tying up between respective circumferential grooves or circumferential grooves 3a, 3b and tread ends T, and file block groups 7-10 are divided to the tread end sides thereof in two files in each side, so in four files in both sides. Depth of a lateral groove with a short pitch is formed shallower than that of a lateral groove with a long pitch, among many lateral grooves 4a-5b dividing file block groups 7-10, and generation of so-called pumping noise is prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a tread pattern with low tire noise, particularly 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.

0002

2. Description of the Related Art Pattern noise can be reduced by imparting so-called pitch variations to the tread pattern. In other words, a structural unit including one lateral groove on the opposite side of the block divided by the circumferential groove of the tire tread and the lateral groove that crosses this is generally called a pitch, and a plurality of blocks with different widths of the lateral grooves and lengths in the circumferential direction of the block are generally referred to as pitches. Pattern noise is reduced by arranging the pitches of seeds (3 to 5 types in a typical passenger car tire) randomly or with a certain regularity.

0003

[Problem to be Solved by the Invention] However, when this pitch variation is introduced, the surface pressure when the tire is pressed into the block is large for blocks with a long pitch and small for blocks with a short pitch. The sound of the collision with the bearing becomes uneven, which increases the noise, and a new problem has arisen in areas that are the core of uneven wear, as typified by polygonal wear. Therefore, an object of the present invention is to propose a tread structure that can equalize the surface pressure between each block in a block pattern that introduces pitch variations with low pattern noise.

0004

[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 extends in a direction crossing these circumferential grooves. It has a group of vertical blocks partitioned by a large number of horizontal grooves, and furthermore, each block in the block group has a pitch defined by the circumferential length of the block including one of the horizontal grooves forming the opposite side, and a pitch of a plurality of lengths. This pneumatic tire has reduced noise by making the depth of lateral grooves belonging to short pitches shallower than the depth of lateral grooves belonging to long pitches in a pneumatic tire in which vertical block groups are arranged in combination.

Now, FIG. 1 shows the main part of the tread of a pneumatic tire according to the present invention. Peripheral grooves 2a forming a pair on both sides of the line O,
2b, 3a, 3b, and lateral grooves 4a, 4b and 5a, 5b that extend in a direction across these circumferential grooves and connect between each circumferential groove or between the circumferential grooves 3a, 3b and the tread edge T, on both sides of the central circumferential groove 1. partitioning the ribs 6a and 6b,
Furthermore, on the tread end side, there are two rows on each side and four rows on both sides.
It is formed by dividing vertical block groups 7 to 10 of the column. Note 11
is the auxiliary circumferential groove. In this embodiment, the lateral grooves 4 and 5 are arranged in a herringbone shape toward the tread end T in association with a notch K provided on one side of the rib 6, so that the direction of rotation of the tire is designated by arrow A.

These vertical block groups 7 to 10 are arranged in a plurality of pitch combinations according to predetermined pitch variations, that is, the circumferential length of each block including one adjacent horizontal groove is varied according to a plurality of length pitches. do. The pitch variations to be introduced are four types of pitches P1 to P4 with different circumferential lengths (P1 > P2 > P3 >
P4), each column block group is composed of blocks of four different block lengths and horizontal grooves of four different widths corresponding to these pitches. For example, taking the vertical block group 9 as a representative, the block 9a and the adjacent horizontal groove 5a correspond to the pitch P1, the block 9b and the adjacent horizontal groove 5a correspond to the pitch P2, and the block 9c corresponds to the pitch P3. and the lateral groove 5a adjacent thereto, and the block 9d and the lateral groove 5a adjacent thereto correspond to the pitch P4, respectively.

[0007] Here, it is important that the depth of the lateral grooves adjacent to each block changes depending on the length of the pitch in which the lateral grooves are included. That is, the depth of the lateral grooves included in the short pitch is made shallower than the depth of the lateral grooves included in the pitch longer than this pitch. For example, as shown in FIG. 2 as a cross section taken along line II--II in FIG. 1, the depths d1 to d4 of the lateral grooves 5a are set to be d1>d2>d3>d4, corresponding to the pitches P1 to P4. Specifically, the ratio r to the longest pitch is 0.90<
The depth of the lateral groove belonging to the pitch of r≦0.99 is 0.975 to 0.988 of the depth D0 of the lateral groove belonging to the longest pitch.
Similarly, the ratio r is 0.80<r≦0.8
The depth of the lateral groove belonging to pitch 9 is 0.9 of the above depth D0.
00 to 0.974 times, and similarly the ratio r is 0.
．． The depth of the lateral grooves belonging to the pitch of 50<r≦0.79 is preferably in the range of 0.750 to 0.899 times the depth D0.

[0008] Other structures of the tire according to the present invention include:
It may be in accordance with conventional tire practices. In other words, the carcass consists of at least one (or at most three) plies whose ends are 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 in a direction (radial direction) substantially perpendicular to the equatorial plane of the tire. At least two of the belts arranged at an angle of
During its formation, at least one auxiliary belt layer having heat-shrinkable cords, typically nylon cords, arranged substantially parallel to the equatorial plane of the tire is provided over the entire width of the main belt layer, the layers of which are arranged crisscrossing each other. In this case, a ribbon formed by arranging a plurality of cords along the circumference of the main belt layer and spirally wound is used. Then, the above-described tread is placed on this belt layer.

[0009]

[Operation] In a block pattern that introduces pitch variations, the width of the lateral grooves is also increased or decreased according to the pitch. In other words, the width of the lateral grooves belonging to long pitches is larger than the width of lateral grooves belonging to short pitches, but the depth of the lateral grooves is It is usually constant. In other words, as shown in FIG. 3, which shows a circumferential cross-section of the tread of a conventional tire, a lateral groove with a width w1 belonging to a pitch P1 and a width w2 (w1
> w2 ) depths d1 and d2 with the lateral grooves are the same, but depending on the tread rubber quality (difference in ease of flow) the skid base gauge under each lateral groove (distance between the bottom of the lateral groove and the belt layer) a1 and a2 are not the same and a1 >
It has been newly discovered that a2 is likely to occur. This is because in the case of rubber with relatively poor fluidity, the resistance when the protrusions of the mold for forming the lateral grooves penetrate into the tread rubber during vulcanization molding is particularly large in the lateral grooves with a wide width w1, so the rubber under the groove bottom and the belt layer This is because the boundary protrudes toward the belt layer side, and therefore the skid base gauge at the lateral groove of width w1 becomes thicker than the design thickness (≈a2).

Next, when the tire that has been vulcanized and molded as described above is filled with air at a specified internal pressure, the belt layer is tensed by the internal pressure, and the protrusion under the lateral groove having the width w1 is restored. Then, the increment (≈a1 − a2 ) of the skid base gauge a1 relative to the design thickness appears as a partial protrusion on the block surface, especially at the edge. This partial protrusion is
Not only does this become the core of uneven wear in each block, but it also causes non-uniformity of the collision noise between the blocks and the road surface that occurs during tire rolling, increasing tire noise. This phenomenon is remarkable in blocks that have high block rigidity and belong to long pitches.

[0011] Therefore, by adjusting the depth of the lateral grooves in accordance with the width of the lateral grooves, that is, the pitch length, the skid base gauge after vulcanization molding can be made almost constant regardless of the width of the lateral grooves, and the specified internal pressure can be maintained in the tire. Even when the block is filled with air, the surface of the block is flattened to avoid uneven wear and increase in tire noise.

0012

[Example] According to the tread pattern shown in Fig. 1,
A pneumatic radial tire with a tire size of 195/60R15 was manufactured as a prototype. The introduced pitch variations are pitch P1: 30mm, pitch P2: 27mm, pitch P
3:25.5mm and pitch P4: 18mm, that is, pitch ratio P1:P2:P3:P4 is 10:9:8.5
:6. The widths of the lateral grooves 4a, 4b, 5a, and 5b are 5 mm for grooves belonging to pitch P1, 4.5 mm for grooves belonging to pitch P2, and 4 mm for grooves belonging to pitch P3.
．． 3mm, and the depth of the groove belonging to pitch P4 is 3.0mm, and the depth is 7.0mm for the groove belonging to pitch P1.
0 mm, 6.85 mm for grooves belonging to pitch P2, 6.7 mm for grooves belonging to pitch P3, and 6.0 mm for grooves belonging to pitch P4. The width of the central circumferential groove 1 is 4 mm, and the width of the circumferential grooves 2a, 2b, 3a, and 3b is 10 mm.
and depth were all 8.5 mm. Also, for comparison,
A trial tire with the same configuration as above was also manufactured, except that the depth of all lateral grooves was 7.0 mm.

After each of the above tires was mounted on a 5 1/2 J x 15 size rim, the tires were filled with air at an internal pressure of 2.2 kgf/mm2 and a load of 440 kg was applied on the drum, and the tire side was placed in an anechoic chamber. A microphone was installed 1m away from the side of the wall and 1m above the tread surface, and a coasting sound test at speeds of 100km/h to 20km/h was conducted.The sound pressure generated by the tire according to the present invention was compared. It showed a value 2.3 dBA lower than that of tires. Also, in the same way as above, after assembling the rim, the tire filled with air was installed on a passenger car, and the tire was driven at an average speed of 80 km/h for 10,000 km/h.
After driving for 2 km, the difference in level between blocks due to wear on the tread surface was examined and found that the comparison tire was 0.5 mm, while the tire according to the present invention was 0.1 mm.
Met.

[0014]

[Effects of the Invention] According to the present invention, it is possible to equalize the surface pressure between each block of a block pattern that introduces pitch variations, and to provide a pneumatic tire that has excellent noise characteristics and high uneven wear resistance. obtain.

[Brief explanation of the drawing]

FIG. 1 is a developed view of a main part of a tread of a pneumatic tire according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG. 1;

FIG. 3 is a sectional view of a main part of a tread of a conventional tire.

[Explanation of symbols]

1 Center circumferential groove 2a Circumferential groove 2b Circumferential groove 3a Circumferential groove 3b Circumferential groove 4a Horizontal groove 4b Horizontal groove 5a Horizontal groove 5b Horizontal groove 6a Rib 6b Rib 7 Column block group 8 Column block group 9 Column block group 10 Column block group 11 Auxiliary circumferential groove

Claims (1)

[Claims] Claim 1: A tread that extends in a toroidal shape between a pair of sidewalls and is defined by a plurality of circumferential grooves extending along the circumference of the tread and a number of lateral grooves extending across these circumferential grooves. A vertical block group is provided, and the vertical block groups are arranged by combining pitches of a plurality of lengths, with a pitch defined by the circumferential length of the block including one of the horizontal grooves forming the opposite side in each block of the block group. A pneumatic tire that reduces noise by making the depth of lateral grooves belonging to short pitches shallower than the depth of lateral grooves belonging to long pitches.