JP3078560B2 - Pneumatic radial tire for high-speed running - Google Patents

Description

[Detailed Description of the Invention] (Industrial application field) In recent years, technological innovations in passenger cars and the completion of an expressway network have made it possible to run at ultra-high speeds exceeding 250 km / h, and accordingly, this ultra-high speed For example, flat radial tires having an aspect ratio of 0.6 or less have been developed, which have sufficient performance for running on roads.

The present invention relates to a pneumatic radial tire for a passenger car, and more particularly to a flat radial tire used for ultra-high speed traveling.

(Prior Art) Generally, a tread of a tire used for this kind of high-speed running is composed of a group of tandem blocks formed by a plurality of relatively wide circumferential grooves along the circumference of the tire and a large number of horizontal grooves connecting the circumferential grooves. Is partitioned.

When a tire having this kind of pattern tread is applied to ultra-high-speed running, each block of the tandem block group during load rolling repeatedly compresses and stretches with the road surface every one rotation, and the number of times increases as the running speed increases. I do. Above all, especially the central portion of the block when not in contact with the ground is stretched by the centrifugal force to protrude from the surrounding portion, and is then rapidly compressed to contact the ground in this state. Therefore, in high-speed running, especially at the center of the block, the ground pressure becomes extremely large and heat is generated, and since this heat is not released, the temperature becomes high, leading to breakage called rubber blowout, and in the worst case, The block comes off, resulting in the removal of the block.

This phenomenon is remarkable in the center of the tread width and in a block having a large area, and significantly reduces the durability of the tire.

Therefore, the inventors have previously described in JP-A-63-162308,
A shallow groove extending in the circumferential direction is arranged in the block in the center area of the tread, and a flat radial tire for high-speed running was proposed, which promoted heat dissipation by reducing the contact pressure and increasing the surface area in this area. The promotion of blowouts could be achieved.

(Problems to be Solved by the Invention) This type of tire is not only used for straight running but also for cornering, and therefore it is important that the tire has excellent durability during cornering. It is. When turning, especially when turning at high speed, the input to the tread tread is large, and the shallow grooves arranged in each block in the above tires extend in the circumferential direction, so this shallow groove can be a new nucleus of uneven wear There is.

Accordingly, an object of the present invention is to provide a pneumatic radial tire that can suppress the occurrence of blowout without sacrificing the uneven wear resistance particularly during high-speed turning.

(Means for Solving the Problems) The present inventors have found that the above-mentioned problem can be solved by inclining a shallow groove provided on a tread land portion with respect to a circumferential groove, and have completed the present invention. It has arrived.

That is, the present invention provides a cylindrical crown portion and a radially extending sidewall portion extending radially inward from both ends of the crown portion, a radial portion extending from one sidewall portion through the crown portion to the other sidewall portion. A pneumatic radial tire in which a non-extensible belt layer and a tread are sequentially arranged on a radially outer side of the carcass in a crown portion, wherein the tread has a plurality of treads extending along a tread circumference. It has a peripheral groove and a large number of lug grooves extending from one of the adjacent peripheral grooves toward the other, and the land portions sandwiched between the lug grooves are oriented in a direction inclined with respect to the peripheral grooves through the center of gravity of each land portion. A pneumatic radial tire for high-speed running, characterized by having a shallow groove that extends, has an opening width of 2 to 6 mm, and has a V-shaped cross section.

FIG. 1 shows a main part of a tread of a pneumatic radial tire according to the present invention. The tread extends in parallel with a central circumferential line O of the tread, and a pair of circumferential grooves 1a and 1b are formed on both sides of the central circumferential line O. And peripheral grooves 2a, 2b extending along the central peripheral line O on both sides of the central peripheral line O in the central portion of the tread; and peripheral grooves 1a, 1b.
Between the lug grooves 3a, 3c or 3 by a large number of lug grooves 3a-3d extending from
b, 3d, while defining a large number of land portions 4a, 4b substantially forming a block, while a large number of lateral grooves or lug grooves extending from the circumferential grooves 1a, 1b to the outside of the tread end T to the shoulder S region of the tread.
By 5a and 5b, one side of each side of the tread edge T is divided into one column block group 6a and 6b. The lug grooves 3a to 3d are arranged at substantially equal intervals in the circumferential direction of the tread, and two adjacent lug grooves 3c and 3d of the three lug grooves arranged in the circumferential direction are opened to the circumferential grooves 1a and 1b. At the opening, there is provided a platform 7 raised from the bottom of the lug groove to a position slightly lower than the surface of the land portions 4a, 4b. This platform 7 suppresses the movement of the block, maintains the rigidity of the block and suppresses the occurrence of uneven wear, and can be arranged in the range of 0.1 to 0.5 times the lug groove length. Further, reference numeral 8 denotes a rib arranged at the center of the tread.

The land portions 4a and 4b have, for each land portion, shallow grooves 9a and 9b which are inclined in the same direction as the lug grooves 3a and 3c and extend on the diagonal of each land portion and have an average depth of 2 mm or less. As shown in FIG. 2, the shallow grooves 9a and 9b have a V-shaped cross section, and the surface area of the land portions 4a and 4b is increased by widening the opening and reducing the depth thereof.
It promotes heat radiation in each land area during tire load rolling.

In the illustrated example, the number of the circumferential grooves is two and the number of the circumferential grooves is four on each side. However, the number of the circumferential grooves can be two to four on one side. When a plurality of peripheral grooves are arranged between the tread end T and the central peripheral line O, the depth of the peripheral groove near the central peripheral line O may be increased.

The angle of the lug grooves 3a and 3b with respect to the central circumferential line O is 40 to 7
It is preferable to arrange in a direction to make it converge at 0 °. Further, all lug grooves may be opened in the circumferential grooves 2a and 2b. In this case, the platforms 7 are not all the same at a depth of 30 to 70% of the lug groove depth. It is preferable to change the depth by using.

In the illustrated example, the lug grooves 3a and 3b opposed to each other with the central peripheral line O interposed therebetween shift the pitch in the circumferential direction of the lug groove and introduce a so-called pitch variation. It may be arranged.

Further, the shallow grooves 9a, 9b provided on the land portions 4a, 4b do not need to be provided on diagonal lines of the land portions, and for example, as shown in FIG. 3, lug grooves 3a to 3d are formed at the center of each land portion. It is also possible to arrange so that the shallow grooves 9a and 9b are inclined with respect to the central circumferential line O, preferably at an inclination of 15 to 75 °, and the center of gravity of each land part (land part). It is important to extend through the center of gravity when the mass is uniformly distributed on the plane figure. Also, the cross-sectional shape is not limited to the V-shape in FIG. 1, but may be a U-shape or other shapes as in the example in FIG.

The other structure of the tire according to the present invention may be in accordance with the custom of a conventional tire.

That is, at least one carcass is wound around the bead core from the inside of the tire to the outside (at most three).
The turn-up ply is used, the ply is a fiber cord represented by rayon, nylon and polyester arranged in a direction (radial direction) substantially perpendicular to the equatorial plane of the tire, the belt layer is a steel cord, Over the entire width of a main belt layer in which at least two layers of a belt in which non-extensible cords such as aromatic polyamide fiber cords are arranged at an angle of 10 to 35 ° with respect to the equatorial plane of the tire are crossed with each other, nylon cords are used. At least one auxiliary belt layer in which a representative heat-shrinkable cord is disposed substantially in parallel with the equatorial plane of the tire, and in forming the auxiliary belt layer, a plurality of cords are arranged along the circumference of the main belt layer. Use spirally wound ones according to the state. Then, the tread described above is arranged on this belt layer.

Although the illustrated example shows a tread pattern that is substantially line-symmetric with respect to the central peripheral line O, the present invention is of course advantageously applicable to a tire having an asymmetric tread pattern.

(Operation) Providing shallow grooves on the land of the tire tread first reduces the mass of the part passing through the shallow groove to prevent overhang due to centrifugal force at the center of the land, and promotes heat dissipation by increasing the surface area of the land. This is extremely effective in suppressing the occurrence of blowout. In particular, the shallow trench advantageously passes through the center of gravity of the land to reduce the mass in the center of the land.

However, if this shallow groove is arranged along the tread circumference, the lateral input applied to the tread tread portion during turning or the like is applied to the edge of the shallow groove from a direction substantially orthogonal to the shallow groove. There is a glad that uneven wear occurs with the edge part of the core.

Therefore, the shallow groove is arranged in a direction inclined with respect to the tread circumferential line to reduce the input applied to the edge of the shallow groove, and to improve the uneven wear resistance.

The shallow groove has an opening width w of 2 to 2 as shown in FIG.
It is important that it is 6 mm, and furthermore, the depth d is 0.5-3 m
m is preferred. This is because if it is too deep, it becomes a nucleus of uneven wear, which is not preferable. Furthermore, the depth d is 0.5-3
2mm average depth over the entire length of the shallow groove
It is important to make the following, especially in terms of both the blowout resistance and the uneven wear resistance.

(Example) A pneumatic radial tire having a tire size of 255 / 40ZR17 was prototyped according to the tread pattern shown in FIG. 1 and the shallow groove structure shown in FIG.

The circumferential groove of this prototype tire is 10 mm in width and 8.5 mm in depth, the lateral groove is 10 mm in opening width, the intermediate width is 4 mm and depth: 5 mm, and the lug groove is 4 mm in width and 5 mm in depth: on the tread circumference It was arranged to converge at an angle of 30 to 90 °.

The inclination angle of the shallow groove with respect to the tread circumference is 50 °,
The width w of the shallow groove shown in FIG. 2 was 3 mm and the depth d was 1 mm.

Similarly, in the tread pattern shown in FIG. 1, the conventional tire (1) having no shallow groove on the land portion and the conventional tire having a shallow groove passing through the center of the land portion along the tread circumference (inclination angle: 0 °). (2) was also prototyped at the same size.

The results of the evaluation of these test tires in a high-speed durability test, a steering stability test, a wear resistance test and an uneven wear resistance test are shown in the following table.

The actual vehicle test was conducted using an ordinary passenger car and the tire internal pressure was 2.5k.
gf / cm ² with one driver on board. Evaluation was for high-speed durability and speed.
It was expressed as an index when it was set to 100.

The high-speed durability test, the internal pressure: 2.5 kgf / a cm ² of the tire placed under a load of 500kg on the drum is rotated at a speed of 100km / h, the speed of 100km / h to 10 km / h increments every 10 minutes Up to the point of failure and evaluated at the speed at the time of the failure.The driving stability test was performed on a 2 km test course at a limit speed, evaluated by lap time and feeling at that time, wear resistance The test measures the unevenness due to abrasion after traveling over 10,000 km at a vehicle speed of 100 and 200 km / h on an elliptical test course with a circumference of 10 km, and evaluates its uniformity.The uneven wear resistance test has a radius of 50 m. On the test course, the level difference between the blocks on both sides sandwiching the circumferential groove after a continuous round of 20 laps at a vehicle speed of 75 km / h was measured and evaluated.

(Effects of the Invention) According to the present invention, the occurrence of blowout can be suppressed without sacrificing steering stability, wear resistance, and uneven wear resistance even at ultra-high speed traveling. Tires suitable for high-speed vehicles can be provided.

[Brief description of the drawings]

1 is a developed view of a tread pattern according to the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a developed view of another tread pattern according to the present invention. T: tread edge, S: shoulder O: central tread line 1a, 1b, 2a, 2b ... circumferential groove 3a-3d ... lug groove, 4a, 4b ... land part 5a, 5b ... horizontal groove , 6a, 6b… tandem block group 7… platform 8… rib, 9a, 9b… shallow groove

Continuation of the front page (56) References JP-A-63-162308 (JP, A) JP-A-57-198102 (JP, A) JP-A-61-275007 (JP, A) JP-A-63-279904 (JP, A) JP-A-62-18305 (JP, A) JP-A-1-233104 (JP, A) JP-A-2-81773 (JP, A) JP-A-63-312205 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60C 11/00-11/13

Claims (1)

(57) [Claims] A radial portion extending from one side wall portion to the other side wall portion through the crown portion; and a cylindrical crown portion and side wall portions extending radially inward from both ends of the crown portion. A pneumatic radial tire in which a non-extensible belt layer and a tread are sequentially arranged on a radially outer side of the carcass in a crown portion, wherein the tread has a plurality of treads extending along a tread circumference. It has a peripheral groove and a large number of lug grooves extending from one of the adjacent peripheral grooves toward the other, and the land portions sandwiched between the lug grooves are oriented in a direction inclined with respect to the peripheral grooves through the center of gravity of each land portion. A pneumatic radial tire for high-speed running, characterized by having a shallow groove extending from 2 to 6 mm in opening width and having a V-shaped cross section.