JPH03295705A - Pneumatic radial tire for high speed running - Google Patents

Abstract

PURPOSE:To restrain generation of blow out without sacrificing wear resistance at a high speed turning especially by providing a shallow groove extending slantwise to a peripheral groove through the center of gravity of each land part, at the land sandwitched between lug grooves of a tread part. CONSTITUTION:At a tread part is provided peripheral grooves 1a, 1b, 2a, 2b forming pairs on both sides of a center peripheral line O of a tread part while extending parallel with the line O, and a plurality of lug grooves 3a - 3d extending to converge to the line O from the grooves 1a, 1b to grooves 2a, 2b, whereby a plurality of land parts 4a, 4b forming a block between lug grooves 3a, 3c or between lug grooves 3b 3d are partitioned. At land parts 4a, 4b, shallow grooves 9a, 9b are provided which are inclined in the same direction as the lug grooves 3a, 3c while extending on the diagonal line of each land part 4a, 4b and which has an average depth of e.g. 2mm or less. With the arrangement, generation of blow out can be restrained without sacrifycing steering stability wear resistance as well as partial wear resistance even under a super high speed running condition.

Description

[Detailed Description of the Invention] (Industrial Application Field) In recent years, due to technological innovations in passenger cars and the development of expressway networks,
It has become possible to run stably at ultra-high speeds exceeding 250 km/h, and along with this, flat radial tires with an aspect ratio of 0.6 or less have been developed that have sufficient performance even at ultra-high speeds. ing.

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

(Prior art) The tread of a tire used for this type of high-speed running is made up of a plurality of relatively wide circumferential grooves along the circumference of the tire and a large number of lateral grooves connecting these circumferential grooves. As an example, a group of blocks is partitioned.

When a tire with a tread pattern of this type is applied to ultra-high-speed running, each block in the column block group during load transfer is repeatedly compressed and stretched with the road surface every rotation, and this number of times increases as the running speed increases. . Particularly, when the block is not in contact with the ground, the central part of the block is stretched by centrifugal force and protrudes from the surrounding parts, and then is rapidly compressed as it touches the ground in this state. Therefore, when running at high speeds, the ground pressure becomes extremely large, especially in the center of the block, and heat is generated, and as this heat is not released, it becomes high temperature, leading to damage called rubber blowout, and in the worst case, This leads to block peeling, where the blocks peel off.

This phenomenon is noticeable in the center of the tread width and in blocks with large areas, and significantly reduces the durability of the tire.

Therefore, the inventors previously proposed in Japanese Unexamined Patent Publication No. 162308/1983 that they placed shallow grooves extending circumferentially in blocks in the central region of the tread, reducing ground pressure in this region and promoting heat dissipation by increasing the surface area. We proposed a flat radial tire for high-speed running, which was able to avoid blowouts by promoting heat dissipation.

(Problem to be solved by the invention) This type of tire is not only used for straight running, but also for cornering, so it is important that it has excellent durability when cornering. It is. When turning, especially when turning at high speeds, the input to the tread surface is large, and since the shallow grooves arranged in each block of the above tire extend in the circumferential direction, these shallow grooves can become a new core of uneven wear. There is sex.

Therefore, the present invention aims to provide a pneumatic radial tire that can suppress the occurrence of blowouts without sacrificing uneven wear resistance, especially during high-speed turning.

(Means for Solving the Problems) The inventors have discovered that the above-mentioned problems can be solved by tilting the shallow grooves provided in the tread land portion with respect to the circumferential grooves, and in completing this invention. It has arrived.

That is, the present invention combines a cylindrical crown portion and sidewall portions extending radially inward from both ends of the crown portion with a radial line extending from one sidewall portion through the crown portion to the other sidewall portion. The carcass is reinforced with a non-stretchable belt layer and a tread 1. The tread is a pneumatic radial tire having a plurality of circumferential grooves arranged in sequence, the tread having a plurality of circumferential grooves extending along the circumference of the tread, and a number of lug grooves extending from one side of the adjacent circumferential grooves toward the other. This pneumatic radial tire for high-speed running is characterized in that the land portions sandwiched between the lug grooves have shallow grooves that extend through the center of gravity of each land portion in a direction inclined to the circumferential groove.

Now, FIG. 1 shows the main part of the tread of a pneumatic radial tire according to the present invention, and this tread is formed by circumferential grooves 1a and lb that extend parallel to the center circumference line 0 of the tread and form a pair on both sides of the center circumference line O. and center circumference 0 at the center of the tread
circumferential grooves 2a, 2b extending along the central circumferential line O on both sides of the
A large number of lug grooves 3a to 3d extend from the circumferential grooves 1a and lb toward the circumferential grooves 2a and 2b in a direction that converges on the central circumferential line O, so that blocks are substantially formed between the lug grooves 3a and 3c or between 3b and 3d. While dividing a large number of land parts 4a, 4b,
A large number of lateral grooves or lug grooves 5a extending from the circumferential grooves 1a, lb to the outside of the tread end r to the shoulder S region of the tread,
5b, one row of vertical block groups 6a and 6b are defined on each side near the tread end T. Lug grooves 3a to 3d
are arranged at approximately equal intervals in the circumferential direction of the tread, and of the three lug grooves lined up in the circumferential direction, two adjacent lug grooves 3c and 3d open into the circumferential grooves 1a and lb, and the lug grooves are formed in these openings. A platform 7 is provided which is raised from the bottom to a position somewhat lower than the surface of the land portions 4a and 4b. This platform 7 suppresses block movement, maintains block rigidity, and at the same time suppresses occurrence of uneven wear, and can be arranged in a range of 0.1 to 0.5 times the lug groove length. Furthermore, 8 is a rib placed in the center of the tread.

In addition, the land portions 4a and 4b have lug grooves 3a and 3c for each land portion.
The average depth of each land area extending diagonally in the same direction is 21all! The following shallow grooves 9a and 9b are provided. As shown in FIG. 2, the shallow grooves 9a and 9b have a 7-shaped cross section.
By making the openings wider and shallower, the surface areas of the land portions 4a, 4b are increased, and heat dissipation from each land portion during tire load transfer is promoted. The cross-sectional shape of the shallow groove is 7.
Various shapes are possible, such as a U-shape or a U-shape.

In the illustrated example, the circumferential groove has four two-way connections on one side, but
Two to four circumferential grooves can be arranged on one side.

When a plurality of circumferential grooves are arranged between the tread end T and the center circumferential line O, it is preferable that the depth of the circumferential groove closer to the center circumferential line 0 is made deeper.

In addition, the angle of the lug grooves 3a and 3b with respect to the center circumferential line 0 is
It is preferable to arrange the lug grooves in a direction converging at 40 to 70".Furthermore, all the lug grooves may be opened to the circumferential grooves 2a and 2b. In this case, the platform 7 has a depth of 30 to 70% of the lug groove depth. It is preferable that the depths are not all the same, but that the depths are varied between circumferentially adjacent platforms.

In the illustrated example, the lug grooves 3a and 3b facing each other across the center circumferential line O are shifted in pitch in the circumferential direction of the lug grooves, introducing a so-called pitch variation, but they are line symmetrical with respect to the center circumferential line O. It can also be arranged.

Furthermore, the shallow grooves 9a, 9b provided in the land parts 4a, 4b do not need to be provided on the diagonal of each land part; for example, as shown in FIG. It is also possible to arrange the shallow grooves 9a, 9b to extend parallel to the central circumferential line O, preferably 15 to 75 mm.
It is important that it has an inclination of 10° and that it extends through the center of gravity of each land area (the center of gravity when the mass is uniformly distributed on the plan view of the land area). Further, the cross-sectional shape is not limited to the V-shape shown in FIG. 1, but may be U-shape as in the example shown in FIG. 3, or any other shape.

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 turnply (or at most three) wrapped around a bead core from the inside of the tire to the outside, while the braai consists of fiber cords typically made of rayon, nylon, and polyester wrapped around 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 degrees 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 . The auxiliary belt layer 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.

Further, although the illustrated example shows a tread pattern that is approximately line symmetrical with respect to the center circumferential line 0, it goes without saying that the present invention is advantageously applicable to tires with asymmetrical tread patterns.

(Function) Providing shallow grooves in the land area of the tire tread first reduces the mass of the area where the shallow grooves pass, thereby preventing the center of the land area from protruding due to centrifugal force, and also promotes heat dissipation by increasing the surface area of the land area. Therefore, it is possible to suppress the occurrence of blowouts.

In particular, it is advantageous for the shallow trench to pass through the center of gravity of the land area in order to reduce the mass in the center of the land area.

However, if these shallow grooves are arranged along the tread circumference, the input from the lateral direction applied to the tread surface during turning will be applied to the edges of the shallow grooves from a direction substantially perpendicular to the shallow grooves. There is a good chance that uneven wear will occur centered around the edges.

Therefore, the shallow grooves are arranged at an angle to the tread circumference to alleviate the input applied to the edges of the shallow grooves and improve uneven wear resistance.

Here, the shallow groove has an opening width W of 2 to 6, as shown in Fig. 2.
It is preferable that III11 and depth d be 0.5 to 3 mm. This is because if the depth is too deep, it becomes the core of uneven wear, which is undesirable. Furthermore, the depth d is 0.5 to 3IllI1
1, the average depth over the entire length of the shallow groove is 2 m.
It is important to keep the thickness below m, especially in terms of achieving both blowout resistance and uneven wear resistance.

(Example) Tire size 255/40ZR17 was prepared according to the tread pattern shown in Fig. 1 and the shallow groove structure shown in Fig. 2.
We prototyped a pneumatic radial tire.

The circumferential groove of this prototype tire is width: 10 mm and depth: 8.5 mm.
ae, the lateral grooves had an opening width of 10 mm, an intermediate width of 4 mm, and a depth of 5++n, and the lug grooves had a width of 4 mm and a depth of 511 Il, and were arranged to converge on the tread circumference at an angle of 30 to 90 @.

In addition, the angle of inclination of the shallow groove to the tread circumference is 50°,
The width W of the shallow groove shown in FIG. 2 was 3III11, and the depth d was 1 m.

Similarly, with the tread pattern shown in Figure 1, a conventional tire (1) with no shallow grooves on the land area and a tire (1) along the tread circumference (
Inclination angle: 0°) A conventional tire (2) having a shallow groove passing through the center of the land area was also prototyped in the same size.

These test tires were evaluated in a high-speed durability test, a handling stability test, an abrasion resistance test, and an uneven abrasion resistance test, respectively, and the results are shown in the table below.

The actual vehicle test was conducted using a regular passenger car, and the tire internal pressure was 2.5.
kgf/cm'' with multiple drivers on board, high-speed durability was evaluated by speed, and other values were evaluated by indexes when each test result of the comparative tire was set as 100.

And high-speed durability test: Internal pressure: 2.5 kgf/cm
” tires are placed on a drum with a load of 500kg, rotated at a speed of 1001u++/h,
The speed was increased by 10 km/h every 10 minutes from h to 10 minutes until the failure occurred, and the speed at which the failure occurred was used for evaluation. Wear resistance test was conducted on an oval test course with a circumference of 10 km at vehicle speeds of 100 and 200 km/h at 11,000 km/h.
The uneven wear resistance test was carried out on a test course with a radius of 50 m by measuring the level difference caused by wear G after running for 0 km, and measuring the level difference after 20 consecutive circular turns at a vehicle speed of 75 km/h. Evaluation was made by measuring the level difference between the blocks on both sides of the groove.

(Effects of the Invention) According to the present invention, it is possible to suppress the occurrence of blowouts even when traveling at ultra-high speeds without sacrificing handling stability, wear resistance, and uneven wear resistance. We can provide tires suitable for high-speed cars.

[Brief explanation of drawings]

FIG. 1 is a developed view of a tread pattern according to the present invention, FIG. 2 is a cross-sectional view taken along the line ■--■ in FIG. 1, and FIG. 3 is a developed view of another tread pattern according to the present invention. T...Tread edge S...Shoulder 0...
・Tread center circumferential lines 1a, 1b, 2a, 2b ・-peripheral grooves 3a to 3d...
・Lug grooves 4a, 4b...Land portions 5a, 5b...
・Horizontal grooves 6a, 6b... Vertical block group 7・
... Platform 8 ... Rib 9a, 9b ... Shallow groove No. 1
Figure 2 Figure 3

Claims (1)

[Claims] 1. A cylindrical crown portion and sidewall portions each extending radially inward from both ends of the crown portion, from one sidewall portion through the crown portion to the other sidewall portion. A pneumatic radial tire reinforced with a radial carcass extending over the entire area, and further comprising a non-stretchable belt layer and a tread sequentially arranged on the radial outside of the carcass at the crown portion, the tread extending along the tread circumference. It has a plurality of extending circumferential grooves and a large number of lug grooves extending from one side of the adjacent circumferential grooves to the other, and the land section sandwiched between the lug grooves is inclined with respect to the circumferential groove through the center of gravity of each land section. A pneumatic radial tire for high-speed running, characterized by having shallow grooves extending in the opposite direction.