JPH0450003A - Pneumatic radial tire suitable to high-speed driving - Google Patents

Abstract

PURPOSE:To improve high-speed durability without deteriorating maneuvering stability and partial wear resistance by positioning a central land part of a tread at a separate position within a particular range in the inside in the diametrical direction of a tire. CONSTITUTION:The tread of a pneumatic radial tire is blocked into two respective vertical block groups 6a, 6b and 7a, 7b on both sides toward tread edges T, and a rib 8 which forms a central part of the tread from peripheral grooves 1a, 1b and 2a, 2b which are mated on both sides of an equator O, a number of horizontal grooves 3a, 3b, 4a, 4b, and 5a, 5b whose tapered ends extend toward the equator O. With this constitution, in forming a tread pattern, the surface of the rib 8 is positioned more inwardly than the surfaces of the other land parts, that is, the surfaces of the vertical block grooves 6a, 6b and 7a, 7b in the diametrical direction of the tire. Namely, the rib 8 is formed so that its surface may be positioned more inwardly than the virtual outline L of the tread which connects the vertical block group 7a and 7b on both the sides, getting over the rib 8, so as to separate within the range of a distance h: 0.1-1.5 mm inwardly in the diametrical direction of the tire.

Description

[Detailed Description of the Invention] (Industrial Application Field) In recent years, due to technological innovations in passenger cars, speeds of 200 to 3 QO
It is possible to run stably at ultra-high speeds of up to 100 km, and along with this, it has sufficient performance to run at ultra-high speeds.
For example, flat radial tires with an aspect ratio (ratio of the cross-sectional height to the tire's maximum width) of about 0.30 to 0.65 have been developed.

The present 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. The ribs are divided by the tread edge, while the lateral grooves extend from the tread edge towards these circumferential grooves at an angle converging on the ear's equator, so that the ground contact of the same lateral groove during load transfer is from the center of the tread to the outside. A so-called directional pattern is known in which the processes are performed sequentially.

(Problem to be Solved by the Invention) The tread thickness of this type of tire is thinner in the circumferential groove, and thicker in the land area divided by the -direction groove, and therefore the difference in mass between the circumferential groove and the land area is large. The amount by which the tires protrude outward in the radial direction due to the centrifugal force generated during high-speed, and even ultra-high-speed driving also differs greatly.

In other words, while the amount of protrusion in the circumferential groove is small, the amount of protrusion in the land area is large.In particular, the amount of protrusion in the rib at the center of the tread is large compared to other land areas, so the ground pressure of the block increases. becomes uneven. This impairs steering stability during ultra-high speed running and causes uneven wear.In addition, when running at ultra-high speed continuously, heat may be generated due to excessive ground pressure, especially in the ribs in the center of the tread, and this heat may cause damage to the tread rubber. Exceeding the heat resistance limit can lead to blowout 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 tire shaft of a central land portion and circumferential groove that are partitioned between these circumferential grooves and continuously extending on the equator of the tire. A pneumatic radial tire having lateral land sections partitioned outward in each direction, when mounted on a regular rim and filled with the proper internal pressure, the central land section of the tread is at least as wide as the land section in the axial direction of the tire. The tire is located at a position 0.1 to 1.5 mm inward in the radial direction of the tire with respect to the imaginary contour line of the tread that straddles the central land area and connects each side land area on both sides of the central land area. This is a pneumatic radial tire suitable for high-speed driving.

Now, FIG. 1(a) shows the main part of the tread of the pneumatic radial tire according to the present invention. A large number of lateral grooves connect the circumferential grooves 1a, lb and 2a, 2b forming pairs on both sides, the tread end T and each circumferential groove completely or with a portion remaining, and extend in a direction that converges on the equator 0. 3a, 3b, 4a, 4
b, 5a, 5b, vertical block groups 6a, 6b, 7a, 7 in two rows each on both sides near the tread end T.
b and a rib 8 forming the central land portion of the tread. A tire with such a directional pattern is used by being mounted on a vehicle with the direction in which the lateral grooves converge and the direction of rotation coincide.

Note that it is important that the central land portion be a rib that extends continuously on the equator 0, especially in order to suppress pattern noise of the tire and improve straight running performance. However, as long as the purpose of the present invention is not impaired, it is possible to form a narrow or shallow groove in the center of the rib, or to introduce cuts from the circumferential grooves on both sides, to further improve drainage performance, etc., as necessary. be.

Although the illustrated example has four circumferential grooves on one side, two to four circumferential grooves can be arranged on one side. Further, the circumferential grooves 2a and 2b are straight circumferential grooves 1a.

1b, the groove width is gradually increased (decreased) in accordance with the pitch of each block to improve the wear resistance of blocks 7a and 7b during high-speed cornering.

It is preferable that the transverse grooves converge at an angle of 75 to 85 degrees with respect to the equator 0, and 60 to 70'' for the transverse grooves 4a, 4b and 5a, 5b, and smaller than the former area. The groove width can be gradually increased from the equator 0 toward the tread edge T, and the groove depth can be equal to or less than the main groove.
All grooves are circumferential grooves 1a, as shown in the figure with circumferential grooves 1a on the al side, and lateral grooves 5a and 5b as types that do not open on the lb side.

There is no need to penetrate between 1b, 2a, and 2b.

Next, Figure (b') illustrates the structure of a tire according to the present invention.

In the figure, 9 is a carcass stretched like a toroid between a pair of peads (not shown), IO is a belt layer placed on the carcass 9, and 11 is a tread placed on the belt layer 9.

The carcass 9 consists of at least one layer (usually 1 to 2 layers) of organic fiber cords typified by polyester, rayon, and nylon arranged in a direction (radial direction) substantially perpendicular to the equatorial plane of the tire; This carcass layer (
Both ends of the braai are wound around the bead core from the inside of the tire to the outside to form a turn-up braai.

The belt layer IO includes at least two layers of belts in which non-extensible cords such as steel cords and aromatic polyamide fiber cords are arranged at an angle of 15 to 35 degrees with respect to the equatorial plane of the tire, and are arranged to cross each other. main belt layer 10
a, and an auxiliary belt layer 1 in which one or more rubberized heat-shrinkable cords (for example, nylon cords) are spirally wound over the entire width of the main belt layer 10a and arranged substantially parallel to the equatorial plane of the tire. ．． It consists of Ob. Then, a tread 11 is arranged on this belt layer 10.

When forming the above-mentioned tread pattern on the surface of the tread 11, the surface of the rib 8 is positioned on the inner side in the tire radial direction than the other land portions, that is, the surfaces of the column block groups 6a, 6b and 7a, 7b.

That is, from the surface of the rib 8 or from the imaginary line of the tread outline connecting the column blocks 7a and 7b on both sides of the rib 8, the distance h: 0.1 to 1 is inward in the radial direction of the tire.
．． Ribs 8 are formed so as to be separated by a range of 5 mm.

In addition, in FIG. 2(b), the entire surface of the rib 8 is shown as a tread structure separated from the virtual contour line within the above range, or as shown in FIG. The desired purpose can also be achieved by forming a depression in the center of the rib 8, separated from the virtual contour line by a range of .

(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 land areas on both sides of the second central land area, which leads to early blowout and reduces high-speed durability. The inventors investigated the cause of the especially intense heat generation in the central land area and found that the central land area has a larger rubber mass than other land areas, the amount of protrusion due to centrifugal force is large, and the heat dissipation ability is low. etc. were found. Therefore, we focused on the ground pressure in the central land area and found that the above problem could be solved by reducing this ground pressure.

That is, by separating the central land portion of the tread radially inward of the tire with respect to the above-described virtual contour line, the central land portion is configured to be in contact with the ground only during load transfer of the tire. Therefore, after ensuring straight running performance and uneven wear resistance,
Heat generation can be suppressed by reducing the rubber mass and the amount of protrusion caused by centrifugal force, making it possible to improve high-speed durability.

Here, it is advantageous for the central land portion to separate at least the axial center of the tire from the imaginary outline of the tread by a range of 0.1 to 1.5 m+n inward in the radial direction of the tire. This is because if this interval is less than 0.1 mm, the amount of protrusion at high speed will exceed 0.1 mm, so 150
If the speed exceeds km/h, the surface pressure in the central land area will eventually rise. On the other hand, if it exceeds 1.5 mm, the difference in level between it and the adjacent land area will become large during normal driving, causing uneven wear.

(Example) The tread pattern shown in Fig. 1(a) and the tread pattern shown in Fig. 1(b)
) or tire size 25 according to the structure shown in Figure 2.
5/40 Two types of ZR17 pneumatic radial tires (test tires A and B) were manufactured.

In these test tires, the circumferential grooves 1a and lb have a width of 10
mm and depth: 8.5 mm, the circumferential grooves 2a and 2b have a maximum width of 10, a minimum width of 28 mm and a depth of 8 mm, the lateral groove has a width of 5 mm and a depth of near mm, and is 30 degrees to the equator of the tire. The angle between the circumferential grooves 2a, 2b near the tread ends and the lateral groove was lOo, and the angle between the circumferential grooves 1a, 1b at the center of the tread and the lateral groove was 30°.

Further, the width of the rib 8 was 15 mm, and the ground contact width of the tread was 200 mm. Then, the surface of the rib 8 on the test tire is made flat, and the entire surface is drawn from the tread outline virtual line L to h = 0.
．． 3 mm apart, while the surface of the rib 8 of test tire B has a concave cross section with a radius of curvature or 10,000 mm outward in the tire radial direction, and the axial center of the tire is spaced h = 0.2 mm from the imaginary tread outline line. .

Note that the surface of the other land portion (vertical block group) of the rib 8 was made to have a convex cross-section with a radius of curvature of 6000111 [+1] outward in the tire radial direction.

On the outside of the Naori-Cass, there is a main belt layer in which two layers of steel cords with a ×5 structure are arranged at an angle of 20 degrees to the equator of the tire and are arranged to cross each other. An auxiliary belt layer covered with nylon cord (1260d/2) was placed.

Furthermore, as a comparison, the structure shown in FIGS. 1(a) and (b) is followed, but the rib 8 is the same size for the tires on the virtual line of the tread outline as well as on the surfaces of other land parts (column block group). I made a prototype.

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.

**Failure at the center (rib) of Nidred The test was conducted using a regular passenger car with the driver or 18 passengers on board, and the evaluation was based on the test results of the comparative tires.
It was an index when it was.

In the steering stability test, the driver evaluates the straightness and lane change performance when driving at 100 to 200 km/h, and in the high-speed durability test, the vehicle is placed on a drum with an internal pressure of 2.5 kg on a 2 m diameter drum.
10km/h every 10 minutes from 150km/h with a tire of g/cm2 pressed with a load of 500kg.
The speed increase was continued until failure occurred, and the evaluation was made at the speed at the time of failure. The uneven wear resistance test was conducted by turning at 70 km/h on a circular test course with a radius of 400 m, and the wear pattern was evaluated after driving 1100 km. did.

(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 a tread pattern according to the present invention, and FIG. 1(b) is a diagram showing the structure of the tread.
Line sectional view, FIG. 2 is a sectional view showing the structure of another tread. T...Tread edge ○...Tire equator L
... Tread outline imaginary lines la, lb, 2a, 2b - ... Circumferential grooves 3a, 3b
, 4a, 4b, 5a, 5b... Horizontal grooves 6a, 6b
, 7a, 7b - Column block group 8... Rib
9...Carcass 10...Belt layer
10a...Main belt layer 10b...Auxiliary belt layer 11...Tread same

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 equator of the tire; a central land section that is partitioned between these circumferential grooves and extends continuously on the equator of the tire; and a central land section that is partitioned on the outside of the circumferential groove in the axial direction of the tire. A pneumatic radial tire having lateral land areas, in which the center land area of the tread is filled with the normal internal pressure after being mounted on a normal rim, and the central land area of the tread is such that at least the center of the land area in the axial direction of the tire It is characterized by being arranged at a position that is spaced inward in the radial direction of the tire within a range of 0.1 to 1.5 mm with respect to the imaginary contour line of the tread that straddles the land area and connects each side land area on both sides. A pneumatic radial tire suitable for high-speed driving.