JPH04100704A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To obtain a pneumatic radial tire excellent in turning performance by arranging additional plies of narrow width consisting of cords arranged so as to incline to the equator of the tire, along the circumferential grooves of the tread so as to be closely in contact with the main belt layer, for respective regions of the main belt layer corresponding to the circumferential grooves. CONSTITUTION:A belt layer 2 is made up of a main belt layer 8 in which a plurality of plies made by arranging inextensible cords at a narrow inclination angle to the equator of a tire are arranged in such a state that the cords are crossed to each other, and an auxiliary belt layer 9 in which thermocontractive cords covered with rubber are arranged in parallel with the equator of the tire over the entire width of the main belt layer 8; and a tread 3 is arranged on the belt layer 2. Further, for respective regions corresponding to the circumferential grooves 4a, 4b of the tread 3 of the main belt layer 8, at least one additional ply 10 that is closely in contact with the ply of the belt layer between the layers of the main belt layer 8 is additionally arranged along each of the circumferential grooves 4a, 4b. By the additional ply, buckling at the belt layer under the circumferential grooves can be restrained, and even at the time of turning, the ground contact pressure can be uniformly maintained.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention relates to pneumatic radial tires for passenger cars, especially those used for ultra-high-speed running exceeding 200 km/h. The present invention relates to an improvement of a belt layer in a flat radial tire having a ratio of cross-sectional height to 0.65 or less.

(Conventional technology) When tires are used for ultra-high-speed running, problems such as separation between the tread and belt and chipping of the tread rubber occur, so it is important that tires have high durability against these problems, so-called excellent high-speed durability. It is essential.

The tire structure takes this high-speed durability into consideration.The belt layer consists of two plies of steel cords arranged at a relatively shallow angle to the equator of the tire on the outside of the carcass, with the cords intersecting each other. Furthermore, some tires have an auxiliary layer on the outside made of organic fiber cords arranged along the equator of the tire. On the other hand, tire treads are made up of multiple land rows of blocks using multiple circumferential grooves that extend relatively wide along the equator of the tire and a large number of lateral grooves that extend across these circumferential grooves in consideration of drainage performance. It will be divided.

(Problems to be Solved by the Invention) The flat tire described above exhibits stable performance from low speeds to high speeds when driving in a straight line, but when driving in corners, especially when turning where strong lateral force is applied. The problem remains that the performance is low.

In other words, if the width of the circumferential groove of the tread is relatively wide, the circumferential groove has lower rigidity than the row of land parts between the circumferential grooves, so when lateral force is applied during cornering, the belt layer under the circumferential groove will sit. Bending may occur.

As a result, the ground pressure of the tire becomes significantly higher in areas close to the circumferential groove of the block, and the ground pressure distribution becomes uneven, causing the belt's load-bearing capacity to be quickly exceeded in areas where the load is concentrated, which impairs the tire's turning performance. or decrease. Among these, tires with low cornering power have the disadvantage that when the slip angle increases, the cornering force reaches its maximum value and then rapidly decreases, resulting in extremely poor cornering performance.

Therefore, an object of the present invention is to propose a belt layer structure that can contribute to improving turning performance.

(Means for Solving the Problems) 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 It has a plurality of circumferential grooves extending along the equator and a land section between these circumferential grooves, and the belt layer includes a plurality of plies in which non-extensible cords are arranged at a shallow angle of inclination to the equator of the tire. A pneumatic radial tire consisting of a main belt layer in which the non-stretchable cords are stacked so as to cross each other, and an auxiliary belt layer in which heat-shrinkable cords are arranged substantially parallel to the equator of the tire over the entire width of the main belt layer. Then, in each area of the main belt layer that substantially corresponds to the circumferential groove of the tread, an additional narrow ply consisting of cords arranged obliquely with respect to the equator of the tire is placed in close contact with the main belt layer and extends along the circumferential groove. This is a pneumatic radial tire characterized by the fact that it is arranged with

Now, FIG. 1 illustrates the structure of a tire according to the present invention.

In the figure, 1 is a carcass, 2 is a belt layer, and 3 is a tread.This tread 3 is located at the equator of the tire (at the center of the width of the tread) extending along the tread circumference and arranged substantially parallel to each other at intervals. In this embodiment, two sets of circumferential grooves 4a and 4b, which form a pair on the left and right in this embodiment, are used to divide the tread into one row in the center and two rows of land portions 5a to 5c on either side of the tread. . Further, 6 is a bead core and 7 is a bead filler consisting of a hard comb.

The carcass 1 consists of at least one ply (usually 1 to 2 plies) in which organic fiber cords such as polyester, rayon, and nylon are arranged in a direction (radial direction) substantially perpendicular to the equator of the tire. Both ends of the carcass ply are wound around the bead core 6 from the inside of the tire to the outside to form a turnup ply.

The belt layer 2 is made of a small number of plies (two of which are arranged in a direction in which the cords intersect with each other), which are made of non-stretchable organic fiber cords arranged at a shallow angle of inclination of 10 to 35 degrees with respect to the equator of the tire. The main belt layer 8 and a ribbon-like body of a heat-shrinkable cord (for example, a nylon cord) coated with one or more rubbers are wound in a spiral shape over the entire width of the main belt layer 8, so that the main belt layer 8 is substantially at the equator of the tire. and an auxiliary belt layer 9 arranged in parallel with the heald foot 2. Then, a tread 3 is arranged on this heald foot 2.

In this example, the auxiliary belt layer 9 includes two additional layers of auxiliary belts in the area from the circumferential groove 4b to the tread ends, and each tread end side is reinforced with three layers.

Further, in each area of the main belt layer 8 corresponding to the circumferential grooves 4a, 4b of the tread 3, at least one additional ply lO that is in close contact with the ply of the belt layer is placed between the layers of the main belt layer 8 in each circumferential groove 4a, 4b. Additional placement along.

This additional ply 10 consists of non-stretchable cords, preferably polyester, rayon, aromatic polyamide fibers and steel, arranged obliquely relative to the equator of the tire and the non-stretchable cords of the main belt layer 8. A narrow ply made of a cord made of the same material as the tire, and the cord is arranged at an angle of inclination of 10 to 35 degrees with respect to the equator of the tire, and at an angle that also intersects the non-extensible cord of the tight ply of the main belt layer 8. is preferred. When the plies of the main belt i that are in close contact with the additional ply exist on both sides in the radial direction, as in the example shown in FIG. 1, it is preferable to intersect the cords of the plies on the outside in the radial direction. The area corresponding to the circumferential grooves 4a and 4b is
When the center of the circumferential groove opening width is set as the center of the area, the area has a length of 1.5 to 2.5 times the circumferential groove width.

The additional ply may be arranged between the plies in the main belt layer 8 shown in FIG. 1, between the main belt layer 8 and the auxiliary belt layer 9, or between the main belt layer 8 and the carcass 1.

(Function) If a large lateral force is applied to the tire during turning, the belt layer will buckle, especially under the circumferential groove of the tread, leading to a decrease in turning performance, so the belt layer under the circumferential groove should be reinforced. This avoided deterioration in turning performance.

That is, for each area corresponding to the circumferential groove of the tread of the main belt layer, an additional ply that is in close contact with the ply of the belt layer is additionally arranged between the layers of the main belt layer along each circumferential groove, so that the belt layer below the circumferential groove is Reinforce. This additional ply suppresses buckling in the belt layer under the circumferential groove, so it is possible to maintain a uniform ground pressure even when cornering, thereby avoiding a decrease in cornering force. In addition, even when the slip angle is large, belt buckling is minimized,
Even when lateral force increases, the ground contact area can be kept large, making it possible to avoid a sudden drop in cornering force after it reaches its maximum value.

(Example) According to the structure shown in Figure 1, tire size 255150
ZR]6 pneumatic radial tire was prototyped.

The circumferential grooves 4a and 4b of this prototype tire have a width of 12 mm and a depth of 8 mrn, and lateral grooves of a width of 4 mm and a depth of near mm converging at an angle of 70° to the equator of the tire are equally spaced in the circumferential direction of the tread. (33 mm intervals).

In addition, on the outside of the carcass, there is a main belt layer 8 with a two-layer structure in which steel cords with a 1×5 structure are arranged at an angle of 24 degrees to the equator of the tire, and a nylon cord with rubber covering the entire width of the main belt layer 8. (1260d/2) Three layers were arranged in the area from the circumferential groove 4b to the tread edge, and one layer of the auxiliary belt layer 9 was arranged in the other areas.

Furthermore, between the layers of the main belt layer 8, there is a
Width 2 consisting of steel cord arranged at an angle of 4°
An additional ply 10 of 4 mm was placed corresponding to each circumferential groove 4a, 4b. In this case, the cords of the additional ply intersect with the cords of the radially outer ply and the cords of the radially inner ply in the main belt layer are in the same direction.

Similarly, tires of the same size that conformed to the structure shown in FIG.

These test tires were placed on a drum with a diameter of 3000 mm at an internal pressure of 2.3 kgf/mm2 and a load of 400 k.
By pushing with g, rotating at 30 km/h, and increasing the slip angle by 1 degree, the slip angle-corner link force curve shown in Figure 2 is obtained, and the results for each item are shown below. It was as shown in the table.

The evaluation is based on an index when each test result of the comparative tire is set as 100, and the larger the index, the better the characteristics.

(*) Cornering force is the amount of fall from the maximum value after taking the maximum value, and back link occurs when the cornering force is a dog. (Effect of the invention) According to this invention, the turning performance is It is possible to provide a pneumatic radial tire that can avoid deterioration and has excellent not only straight running performance but also turning performance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a pneumatic radial tire according to the present invention, and FIG. 2 is a graph showing a slip angle-cornering force curve. ■...Carcass 2...Belt layer 3...
・Tread 5a to 5C...Land part 6...
Bead core 7... Beat filler 8...
・Main heald layer 9...Auxiliary belt layer lO...
・Additional ply Figure 2's 7° angle

Claims (1)

[Claims] 1. A belt layer and a tread are sequentially arranged radially outward of the tire in the crown portion of a radial carcass extending in a toroidal shape between a pair of beads, and the tread extends along the equator of the tire. The belt layer includes a plurality of circumferential grooves and a land section defined between these circumferential grooves, and the belt layer includes a plurality of plies in which non-stretchable cords are arranged at a shallow inclination angle with respect to the equator of the tire. A pneumatic radial tire consisting of a main belt layer stacked in a crosswise arrangement and an auxiliary belt layer in which heat-shrinkable cords are arranged substantially parallel to the equator of the tire over the entire width of the main belt layer, In each area of the belt layer substantially corresponding to the circumferential groove of the tread, a narrow additional ply consisting of cords arranged obliquely with respect to the equator of the tire is arranged along the circumferential groove in close contact with the main belt layer. Features pneumatic radial tires.