JPH0478701A - Pneumatic radial tire suitable for high speed running - Google Patents

Abstract

PURPOSE:To improve durability in high speed by arranging small grooves inclined to the tire equator alternately in the inclined direction on periphery of the center land between peripheral grooves on a pneumatic radial tire suitable for high speed running for a passenger car and the like. CONSTITUTION:Extending small grooves 9a, 9b obliquely crossing the equator 0 between peripheral grooves 1a, 1b are arranged over whole periphery of a tread in such a manner that their inclination to an equator 0 is alternately reverse to each other between the small grooves 9a, 9b neighboring with each other in the tread peripheral direction on a rib 8 forming the center land part of the tread. At this time, it is desirable to set a width of the rib 8 to 0.006-0.15 times the tread width and an inclination angle theta of the small grooves 9a, 9b within a range of about 20-60 deg.. Furthermore, a width of a groove is set to such a degree that both side walls close to join together during load operation, for instance, 0.5-3.0 mm, and a depth of the groove load operation, for instance, 0.5-3.0 mm and a depth of the groove is set to about 0.3-0.8 of the peripheral grooves 1a, 1b.

Description

[Detailed Description of the Invention] (Industrial Application Field) In recent years, due to technological innovations in passenger cars, speeds of 200 to 300
It is possible to run stably at ultra-high speeds of up to 1.5 km, and along with this, it also has sufficient performance for running at ultra-high speeds, for example, with an aspect ratio (ratio of the tire's cross-sectional height to its maximum width) of 0. A flat radial tire with a diameter of about 30-0.65 has been developed.

The second invention relates to improvements in the tread of pneumatic radial tires for passenger cars, particularly flat radial tires used for high-speed running.

(Prior art) Many tread patterns applied to this type of tire place particular emphasis on drainage performance and handling stability, and a typical tread pattern consists of a pair of circumferential grooves on both sides of the tire's equator. While dividing the ribs, horizontal grooves are provided that extend from the tread edge toward these circumferential grooves in a direction that converges on the tire's equator, and the same horizontal grooves contact the ground from the center of the tread to the outside during load transfer. A so-called directional pattern in which the processes are performed sequentially is known.

(Problem to be Solved by the Invention) The tread thickness of this type of tire is thinner at the circumferential groove and thicker at the ridge section divided by the horizontal grooves.Therefore, the difference in mass between the circumferential groove and the ridge section is large; Furthermore, the amount by which the tires protrude outward in the radial direction due to the centrifugal force generated when driving in the Zhao high speed range also differs greatly. In other words, while the amount of protrusion in the grooves is small, the amount of protrusion in the ridges is large. In particular, the amount of protrusion at the ribs in the center of the tread is the largest compared to other ridges, so the ground pressure distribution of the block becomes uneven. This impairs steering stability during ultra-high-speed running and causes uneven wear. In addition, when ultra-high-speed running continues, heat due to excessive ground pressure is generated, especially in the ribs in the center of the tread, and this heat damages the tread rubber. Exceeding the heat resistance limit can lead to blowouts and reduce the tire's high-speed durability.

Therefore, the present invention aims to provide a pneumatic radial tire that improves high-speed durability without sacrificing handling stability and uneven wear resistance, and has high performance that can withstand use at ultra-high speeds. It is something to do.

(Means for Solving the Problem) The present invention sequentially arranges a belt layer and a tread outward in the radial direction of the tire on the crown portion of a radial carcass extending in a toroidal shape between a pair of beads, and the tread At least one pair of circumferential grooves extending along the equator of the tire and forming a pair on both sides of the equator of the tire, and a lateral groove extending in a direction transverse to the equator of the tire on the outside of these circumferential grooves in the axial direction of the tire, and a lateral groove partitioned between the circumferential grooves. A pneumatic radial tire comprising a central land portion that extends continuously on the equator of the tire, and a narrow groove that crosses the central land portion in a direction inclined with respect to the equator of the tire between the circumferential grooves. A high speed vehicle in which tires are lined up on the same side of the central land area in an arrangement including alternating positions with opposite inclinations, or in which thin grooves extending in series on or along the equator of the tires are arranged in the central land area. Pneumatic radial tires suitable for driving.

Now, FIG. 1(a) shows the main part of the tread of the pneumatic radial tire according to the present invention, and the tread is connected substantially along the equator (circumference at the center of the width of the tread) 0 of the tire. The circumferential grooves 1a, lb and 2a, 2b forming a pair on both sides connect the tread end T and each circumferential groove, or extend from the circumferential grooves 2a, 2b to the front of la, lb, and converge at the equator 0. A large number of horizontal grooves 3 arranged in
a, 3b, 4a, 4b and 5a, 5b,
Two vertical row block groups 6a on each side near the tread end T;
6b, 7a, 7b, and a rib 8 forming the central land portion of the tread. This central land area has a rib 8 that extends continuously on the equator 0, especially in order to improve the pattern noise and straightness of the tire.
．． It is preferable to have a width of 0.006 to 0.15 times.

A tire with a directional pattern like the illustrated example is used by being mounted on a vehicle with the direction in which the lateral grooves converge and the direction of rotation coincide.

Further, in the rib 8, thin grooves 9a and 9b extending obliquely across the equator O between the circumferential grooves 1a and lb are formed so that the inclinations with respect to the equator O are in opposite directions in the narrow grooves that are adjacent to each other in the tread circumferential direction. In the example, narrow grooves 9a and 9 are provided all around the circumference.
b are arranged alternately on the tread circumference. Regardless of which side the narrow grooves 9a and 9b are inclined toward the equator O, it is preferable that the inclination angle e thereof is in the range of 20 to 60''. Furthermore, as shown in the same figure, the narrow grooves 9a and 9b The width W is preferably narrow enough to allow both side walls to close together during load transfer, specifically in the range of 0.5 to 3.0 aem, and the groove depth h is 0.3 to 0.5 mm of the circumferential grooves 1a and 1b. 8
A double range is preferred.

The narrow grooves 9a, 9b can be fixed at one end or both ends near the end of the lip, and there is no need to arrange them alternately over the entire circumference in different directions of inclination, but in the same direction as long as the purpose is not impaired. Of course, a predetermined number of inclined narrow grooves 98 or 9b can be arranged in succession in the circumferential direction.

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.

Also, unlike the straight circumferential grooves 1a, lb, the circumferential grooves 2a, 2b have groove widths that gradually increase (decrease) in accordance with the pitch of each block, so that the width of the circumferential grooves 2a, 2b is gradually increased (decreased) in accordance with the pitch of each block, so that the width of the circumferential grooves 2a, 2b is different from that of the straight circumferential grooves 1a, lb. Contributes to improved wear resistance.

The angle of the transverse grooves with respect to the equator 0 is 7 in the transverse grooves 3a and 3b.
5 to 85 @ and 60 for horizontal grooves 4a, 4b and 5a, 5b
It is preferred to converge at an angle of ~70° and less than the former zone. Also, the groove width is from equator 0 to tread edge T.
It is possible to gradually increase the groove depth toward the main groove, or the groove depth can be equal to or less than the main groove. The lateral grooves are a circumferential groove 1a in Fig. 1(a) and a lateral groove 5a as a type that does not open on the lb side.
, 5b, it is not necessary for all the grooves to penetrate between the circumferential grooves la, lb and the circumferential grooves 2a, 2b.

Next, the tread pattern shown in FIG. 2 is an example in which the narrow grooves arranged in the lip 8 are not diagonally across the rib 8, but are narrow grooves 10 extending on or along the equator 0. It may be meandering or zigzag as long as it extends substantially continuously. In this case, the width and depth of the narrow groove 10 are also the first.
This corresponds to the narrow grooves 9a and 9b in the figure.

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 is made up of at least one turnply (3 at most) wrapped around a bead core from the inside of the tire to the outside. The belt layer consists of non-extensible cords such as steel cords and aromatic polyamide fiber cords arranged at an angle of 5 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.

(Function) The heat generated in the central land area of the tread during high-speed running is more intense than the heat generated in the ridges on both sides of the central land area, which leads to early blowout and reduced high-speed durability. The inventors investigated the causes of particularly intense heat generation in the central land area and found that the central land area has a larger rubber mass than other ridges, the amount of protrusion due to centrifugal force is large, and the heat dissipation ability is low. etc. were found. When we investigated a structure that would promote heat dissipation without sacrificing the straight-line stability that the central land area provides, we found that it would be advantageous to form narrow grooves in the central land area.

That is, the narrow grooves are grooves that cross the central land portion in a direction inclined to the equator of the tire, and these narrow grooves are arranged on the circumference of the central land portion in an alternating arrangement such that the slopes of the tire relative to the equator are opposite to each other. Then, the surface area of the central land area increases, and therefore the heat dissipation capacity also increases, making it possible to avoid a decrease in durability due to heat generation.

Here, the angle of inclination of the narrow groove tire with respect to the equator is 20 to 60.
It is preferable that the angle of inclination is in the range of ', because the angle of inclination is 60
If the angle exceeds 20 degrees, the total length of the narrow grooves in the central land area becomes too short and sufficient heat dissipation effect cannot be obtained. As a result, the block rigidity in this portion is insufficient, and the rigidity of the central land portion is therefore reduced, impairing steering stability.

When a narrow groove is provided across the central land area as described above, if the slope of the narrow groove becomes small, the rigidity of the central land area becomes insufficient. As shown in , if the narrow grooves are to extend in a series on or along the equator of the tire within the central land area, even if the angle of inclination of the narrow grooves with respect to the equator of the tire is less than 20°, the narrow grooves will not extend in the central land area. It is possible to enhance the heat dissipation effect without reducing the rigidity.

(Example) Two types of pneumatic radial tires (test tires A and B) with a tire size of 255/40 ZR17 were manufactured according to the tread patterns shown in FIG. 1(a) and FIG. 2.

In these test tires, the circumferential grooves 1a and lb have a width of 1
0m and depth: 8.5+ui, circumferential grooves 2a and 2b are maximum width: 10m, minimum width: 8m and depth: 811-, horizontal groove is width: 5m and depth: 1mm, and 30m at the equator of the tire. The angle between the circumferential grooves 2a and 2b near the tread edge and the lateral groove is 80°, and the angle between the circumferential grooves 1a and lb at the center of the tread and the lateral groove is 30°, and the angle between the lateral groove and the circumferential grooves 2a and 2b near the tread edge is 30°. Ribs 8 with a diameter of 20 mm were sectioned.

In this rib 8, a narrow groove with a width of 1.5 mm and a depth of 6++n+ is formed in the tread pattern of Fig. 1 (a) (tire A).
In the case of the tread pattern (tire B) shown in FIG. 2, the tire was placed at an angle θ of 45°, and on the equator of the tire.

On the outside of the Naori-Cass, there is a main belt layer consisting of two layers of 1x5 steel cords arranged at an angle of 20 degrees to the equator of the tire, arranged so as to cross each other, and a main belt layer with the entire width of the main belt layer. An auxiliary belt layer covered by circumferential spiral wrapping of nylon cord (1260 d/2) was arranged.

Further, as a comparison, a comparative tire C having the same size and conforming to the tread pattern shown in FIG. 1(a) but without having narrow grooves in the ribs 8 was also manufactured.

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

The evaluation of each test was based on an index when each test result of the comparative tire was set as 100.

The steering stability test was conducted using a regular passenger car with an internal tire pressure of 2.5 kg/am and one driver on board.
The driver evaluates the feeling of straight-line performance and lane change performance when driving at 150 to 200 km/h.The high-speed durability test was conducted using an internal pressure of 2.5 k on a drum with a diameter of 2 m.
10km/h every 10 minutes from 1100k/h with a tire of 500kg
Continue to increase the speed until failure occurs, and evaluate at the speed at the time of failure. The uneven wear resistance test was conducted at 70) am/
The vehicle was run at a speed of 10 km, and the amount of uneven wear after running for 10 km was examined and evaluated.

(Effects of the Invention) According to the present invention, there is provided a high-performance tire that can improve high-speed durability without sacrificing handling stability and uneven wear resistance, and can withstand running at ultra-high speeds. becomes possible.

[Brief explanation of the drawing]

FIG. 1(a) is a developed view of the tread pattern according to the present invention, and FIG. 1(a) shows the structure of the tread.
2 is a developed view of another tread pattern. T...Tread edge O...Tire equator 1a
, 1b, 2a, 2b - Circumferential grooves 3a, 3b, 4a, 4b, 5a, 5b - Horizontal grooves 6a, 6b, 7a, 7b... - Column block group 8
...Ribs 9a, 9b, 10...
Narrow groove Figure 1 (b) Figure 2

Claims (1)

[Claims] 1. A belt layer and a tread are sequentially arranged radially outward of the tire on the crown portion of a radial carcass extending in a toroidal shape between a pair of beads, and the tread is arranged along the equator of the tire. At least one pair of circumferential grooves that extend and form a pair on both sides of the tire's equator, a lateral groove that extends in a direction transverse to the tire's equator on the outside of these circumferential grooves in the tire's axial direction, and a lateral groove that is partitioned between the circumferential grooves and that is located on the tire's equator. A pneumatic radial tire having a continuously extending central land section, wherein narrow grooves between the circumferential grooves cross the central land section in a direction inclined with respect to the equator of the tire, and grooves with narrow grooves extending in the opposite direction with respect to the equator. This pneumatic radial tire is suitable for high-speed driving and is arranged around a central land area in an arrangement that includes an alternating arrangement. 2. A belt layer and a tread are sequentially arranged radially outward of the tire on the crown part of the radial carcass extending in a toroidal shape between a pair of beads, and the tread extends along the equator of the tire and extends along the equator of the tire. At least one pair of circumferential grooves forming a pair on both sides, a lateral groove extending in a direction crossing the equator of the tire on the axially outer side of these circumferential grooves, and a center partitioned between these circumferential grooves and extending continuously on the equator of the tire. What is claimed is: 1. A pneumatic radial tire suitable for high-speed running, comprising: a land portion; the central land portion has narrow grooves extending on or along the equator of the tire;