JP5193448B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire having an asymmetric tread pattern, and in particular, proposes a technique for improving braking performance without deteriorating hydroplaning resistance.

A pneumatic tire having an asymmetric tread pattern is disclosed in Patent Document 1.
This pneumatic tire has a difference between the negative rate of one side tread located on one side in the tire width direction with respect to the tire equator line and the negative rate of the other side tread located on the other side in the tire width direction with reference to the tire equator line. Is 5% or less, and has a rib width that is 5% or more and 20% or less of the tread width of all treads, and is arranged offset to one side in the tire width direction with respect to the tire equator line, and the tire equator line of the center line A circumferentially continuous central rib continuous in the tire circumferential direction with an offset amount less than the rib width, and formed on the other side tread at intervals in the tire circumferential direction toward the outer end in the tire width direction. The number of blocks formed by the horizontal grooves is 40 or more and less than 60, and the one side tread includes a large block and a small block. The main block is arranged on the outer side in the tire width direction, and the large block is continuous with the main body portion and arranged in the tire width direction with respect to the main body portion and shifted in the tire circumferential direction. The number of pitches in the tire circumferential direction of the large block is equal to or less than one-third of the number of pitches of the block, and the small block is formed of each extension portion continuous in the tire circumferential direction. This tire is characterized by the fact that it is placed between the two, and in this tire, it is possible to achieve both steering stability and WET performance, and to minimize the wear difference between the outer tread and the inner tread with reference to the tire equator line. Suppose you can.
JP 2003-170705 A

  The present invention relates to such an improvement of the prior art, and in particular, in view of the fact that the braking performance of a tire is an important factor for improving the safety of a vehicle, the hydroplaning performance of a wet road surface is improved. It is an object of the present invention to provide a pneumatic radial tire that can effectively improve braking performance without lowering.

  The braking force of the tire is generated by the friction between the tire and the road surface, and the magnitude of the friction force depends on the rigidity of the land portion partitioned by the tread surface and the rubber property of the tread surface. The present invention focuses on the rigidity of the land portion and aims to increase the braking force by generating a larger frictional force by increasing the rigidity of the land portion. On the other hand, a decrease in the resistance to hydroplaning due to the decrease in the groove area is effectively prevented.

Therefore, the pneumatic radial tire according to the present invention includes a tread portion, a pair of sidewall portions that are continuous to the respective side portions of the tread portion, and a bead portion that is continuous to the inner peripheral side of each sidewall portion. In addition, a radial carcass composed of one or more carcass plies extending in a toroidal manner between bead cores arranged in the bead portion, and a layer disposed on the outer peripheral side of the crown region of the radial carcass. A belt composed of the above belt layer, and provided with a plurality of circumferential grooves extending continuously in the circumferential direction and a plurality of lateral grooves extending in the tread width direction on the tread surface. , shoulder block row which best formed in a vehicle inner side of the inner part which is to be positioned on the inside of the vehicle from the equator line in the mounting attitude of the vehicle, on the peripheral block Number 50 to 90 pieces of (N _iN), most vehicle outside the formed shoulder blocks circumferentially on the block number of the rows of outer portion to be positioned outside of the vehicle than the equator line at the same position of the tire (N _out) was 40-70 pieces, and Ri Do ratio of those blocks number of _(N iN _/ N _out) as a range of 1.1 to 1.5, said inner portion, shoulder blocks formed in the most inboard Ribs extending continuously in the circumferential direction were provided at positions adjacent to the equator side of the row .

Here, preferably, the belt is constituted by two steel cord belt layers, and a belt protective layer made of an organic fiber cord extending in the circumferential direction and covering the entire width of the belt is disposed on the outer peripheral side of the belt. .
Preferably, the steel cord belt layer is constituted by a steel wire cord having a two-layer structure of a core and a sheath.

  In the pneumatic radial tire according to the present invention, a rib is formed on the inner portion of the tire to give a high rigidity to the tread land portion on the inner portion, and the number of shoulder blocks on the outer portion of the tire is reduced. Since the tread surface land portion rigidity can be increased by increasing the block size, the entire tire can generate a large braking force by increasing the frictional force with the road surface under high land portion rigidity.

  On the other hand, by increasing the number of shoulder blocks in the inner part, it is possible to sufficiently secure the drainage performance by the large number of lateral grooves and to suppress the occurrence of hydroplaning phenomenon on the wet road surface.

Here, the reason why the number of blocks in the shoulder block row in the inner part is in the range of 50 to 90 (N _iN ) is to make the hydroplaning performance and braking performance compatible at a high level. If the number exceeds 50, the tread land portion rigidity becomes too low and the braking performance, steering stability and the like are deteriorated. On the other hand, if the number is less than 50, the number of lateral grooves is reduced and the drainage performance is deteriorated.

In addition, by setting the number of blocks (N _out ) in the shoulder block row of the outer portion to be in the range of 40 to 70, high tread land against the action of a large load on the outer portion during turning and braking. Part rigidity can be secured.
In other words, if the number of blocks exceeds 70, the land rigidity becomes too low, and if it is less than 40, the drainage performance becomes too low.

Also, here, by setting the ratio of the number of blocks (N _iN / N _out ) in the range of 1.1 to 1.5, the drainage performance is improved at the inner portion of the tire, and the land portion rigidity at the outer portion of the tire. It is possible to sufficiently adequately separate the functions of the inner and outer portions of the tire.
In other words, if the ratio is less than 1.1, it is difficult to make the inner and outer parts function as intended, while if the ratio exceeds 1.5, the shoulder blocks of the inner and outer parts of each part are difficult to function. The rigidity difference becomes too large, and uneven wear occurs between them.

  In such a pneumatic tire, for example, the belt is constituted by two steel cord belt layers whose belt layer cords extend in opposite directions with respect to the tire equatorial plane, and adjacent to the outer peripheral side of the belt, When a belt protective layer made of an organic fiber cord extending in the circumferential direction and covering the belt over its entire width is provided, the rigidity of the tread portion can be increased based on the increase in rigidity of the tread portion.

  Here, the belt protective layer itself also functions to restrain the protruding deformation of the tread portion due to the centrifugal force when the tire rotates.

  In this case, when the steel cord belt layer is formed of a steel wire cord having a two-layer structure of a core and a sheath, the rigidity of the tread land portion can be further increased as the belt rigidity increases.

FIG. 1 is a sectional view in the tire width direction showing an embodiment of the present invention, and FIG. 2 is a development view of a tread pattern on a tread surface.
In the figure, reference numeral 1 denotes a tread portion, 2 denotes a pair of side wall portions continuous to the respective side portions of the tread portion 1, and 3 denotes a bead portion continuous to the inner peripheral side of each side wall portion 2.

Reference numeral 4 denotes a bead core disposed in each bead portion 3, and 5 denotes a radial carcass composed of one or more carcass plies extending in a toroidal manner between the bead cores 4 to reinforce each of the portions 1, 2, and 3. Indicates.
Here, on the outer peripheral side of the crown region of the radial carcass 5, for example, a belt 6 made of two steel cord belt layers and an organic fiber cord extending in the circumferential direction, covering the belt 6 over its entire width, for example, one layer The belt protective layers 7 are sequentially disposed.

  Here, preferably, the steel cord belt layer is configured by a steel wire cord having a two-layer structure of a core and a sheath, and preferably, the steel wire cord of each belt layer is disposed between the belt layers on the tire equatorial plane. On the other hand, they are arranged so as to extend in opposite directions.

  Preferably, the belt protective layer 7 is made of a composite organic fiber cord having a cord elastic modulus of 10,000 MPa to 20,000 MPa, which is formed by twisting low-elasticity nylon fibers and high-elasticity aramid fibers.

  In FIG. 2 which shows the development view of the tread pattern of such a pneumatic radial tire, the right half of the figure is the inner portion where the tire is positioned on the inner side of the vehicle from the equator line E in the mounting posture on the vehicle. 8 and the left half of the figure is an outer portion that is located outside the vehicle in the same posture of the tire.

Here, a single rib 11 extending linearly and continuously in the circumferential direction is provided at a position adjacent to the equator line E side of the shoulder block row 10 formed on the innermost side of the inner portion 8, and the shoulder block is provided. A plurality of horizontal grooves 12 extending in the tread width direction are partitioned into rows 10 and blocks 13 having a total number (N _iN ) in the range of 50 to 90 are defined.

  Here, a plurality of ribs 11 can be provided, and the extending form of the ribs 11 can be a zigzag or other bent form.

On the other hand, the shoulder block row 14 formed on the outermost portion of the outer portion 9 and wider than the previous shoulder block row 10 has a total number (N on the circumference) by a plurality of lateral grooves 15 that also extend in the tread width direction. _OUT) will partition the block 16 of 40 to 70 pieces of range, the range of 1.1 to 1.5 the ratio _(N iN _{/ N OUT)} of the block number _(the number of blocks for _{N OUT) (N iN)} And

  2, the lateral groove 12 formed in the block row 10 is somewhat convex downward, and the lateral groove 15 formed in the block row 14 is somewhat upward convex. However, this is not essential. For example, both the lateral grooves 12 and 15 may be extended in a form that protrudes in the opposite direction as shown in the figure. It is also possible to extend both in a straight line.

  Further, here, a plurality of circumferential grooves 17 extending continuously in the circumferential direction are provided to extend in a straight line on the tread surface for partitioning the block rows 10 and 14 and the ribs 11 and the like. All or a part of these circumferential grooves 17 can be extended in a zigzag or other bent form.

  Further, as shown in FIG. 2, a center rib 18 is provided between the pair of wide circumferential grooves 17 positioned with the equator line E sandwiched therebetween, and slightly extends outwardly from the vehicle and extends linearly. Intermediate block rows 19 and 20 are provided on the inside and outside of the vehicle, respectively, of the circumferential grooves 17 that define 18, and the intermediate block row 19 of the inner portion 8 is blocked by an inclined groove 21 that extends upward in the figure. 22 is formed, and the block 24 is formed in the intermediate block row 20 of the outer portion 9 by the bent groove 23 which is bent in a substantially V shape but has a strong upward tendency.

  In addition, as shown in the figure, the inclined surfaces of the blocks 16, 22, and 23, in which the block height is gradually reduced toward the corner tips adjacent to the circumferential grooves 17 to ensure the corner rigidity, or A curved surface is formed.

In the figure, P _IN 1 and P _IN 2 indicate the respective pitch lengths in the inner portion 8 of the tread pattern, and P _OUT 1 and P _OUT 2 indicate the respective pitch lengths in the outer portion 9. Show.

The structure shown in FIG. 1 and the asymmetric tread pattern shown in FIG. 2 are provided. The inner shoulder block row 10 has 68 blocks (N _iN ) and the outer shoulder block row 14 has 52 blocks (N _out ). Example tires of size 245/40 R18,
The asymmetric tread pattern shown in FIG. 3 is used, and each of the comparative example tires having the same configuration as the example tires is mounted on a passenger car (Audi A4) except that the number of blocks in each shoulder block row is 68. Then, the vehicle was run, and the braking performance and anti-hydroplaning performance of each tire were measured.
The results are shown in Table 1.

Here, the braking performance is obtained by measuring a braking distance required for decelerating from 80 km / h to 20 km / h by dry test coating.
Further, the anti-hydroplaning performance was obtained by measuring the vehicle speed at which hydroplaning phenomenon occurred on a test course with a water depth of 5 mm.

According to Table 1, in the example tire in which the number of blocks in each shoulder block row is changed and the ratio of the number of blocks (N _IN / N _OUT ) is 1.31, the comparative tire in which the ratio is 1 It is clear that the braking performance can be effectively improved while ensuring the same anti-hydroplaning performance.

It is sectional drawing of the tire width direction which shows embodiment of this invention. It is a tread pattern development view of the tire shown in FIG. It is a tread pattern development view of a comparative example tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Radial carcass 6 Belt 7 Belt protective layer 8 Inner part 9 Outer part 10, 14 Shoulder block row 11 Rib 12, 15 Horizontal groove 13, 16, 22, 24 Block 17 Circumferential groove 18 Center rib 19, 20 Intermediate block row 21 Inclined groove 23 Bending groove E Equatorial line

Claims (3)

The tread portion includes a tread portion, a pair of sidewall portions, and a bead portion, a radial carcass extending in a toroidal manner between bead cores disposed in the bead portion, and a belt disposed on the outer peripheral side of the crown region of the radial carcass. A pneumatic radial tire having a plurality of circumferential grooves extending continuously in the circumferential direction and a plurality of lateral grooves extending in the tread width direction on the tread surface of
The number of blocks (N _iN ) on the circumference of the shoulder block row formed on the innermost side of the inner portion of the inner part that is located on the inner side of the vehicle in the mounting posture of the tire on the vehicle is 50 to 90, The number of blocks (N _out ) on the circumference of the shoulder block row formed on the outermost side of the outer portion of the tire, which is located outside the equator line with the same posture, is 40 to 70, and those Ri Do ratio of the block number of the _(N iN _/ N _out) as a range of 1.1 to 1.5,
A pneumatic radial tire in which a rib extending continuously in a circumferential direction is provided at a position adjacent to the equator side of a shoulder block row formed on the innermost side of the inner portion of the inner portion .   2. The belt is composed of two steel cord belt layers, and a belt protective layer made of an organic fiber cord extending in the circumferential direction and covering the entire width of the belt is disposed on the outer peripheral side of the belt. Pneumatic radial tire described in 2.   The pneumatic radial tire according to claim 2, wherein the steel cord belt layer is constituted by a steel wire cord having a two-layer structure of a core and a sheath.

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