JP3068220B2 - Pneumatic radial tires with excellent handling stability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a tread of a pneumatic radial tire, particularly a radial tire for a passenger car.

[0002]

2. Description of the Related Art In a tire of this type, it is customary to reinforce the outside of a carcass forming a skeleton of the tire with a belt layer. In particular, in the case of a tire used for high-speed running, the tire corresponds to a side portion in a tread width direction. Multiple belt layers may be placed in an area.

[0003]

In the tire having the above structure, the tread stiffness is higher at the side portions than at the center portion due to the arrangement of the belt layer, so that the contact pressure distribution is also higher at both side portions near the tread edge. Then, since the grip force against the ground contact surface at the time of cornering is biased to the side of the tread, the change in the grip force generated due to steering angle change and disturbance from the road surface etc. increases, especially reaching the so-called limit, in which sliding starts at cornering. The behavior of the vehicle immediately before or when the vehicle exceeds the limit changes abruptly, and there is a disadvantage that steering stability is impaired. Accordingly, an object of the present invention is to provide a pneumatic radial tire excellent in steering stability, in which the behavior of the vehicle near the above-mentioned limit is gentle and easy to control when exceeding the limit.

[0004]

Means for Solving the Problems The inventors of the present invention have studied means for solving the above-mentioned problems, and have found that a change in vehicle behavior near the cornering limit can be minimized by making the tread contact pressure an appropriate distribution. After confirming that the invention can be suppressed to the minimum, the present invention has been completed. 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 reinforced with a carcass and further provided with a belt layer of a non-extensible cord extending over the entire width of the tread between the radial carcass and the tread arranged in the crown portion, wherein the tire is filled with a specified internal pressure after mounting the applicable rim. In the section including the rotation axis of the tire in the state where
The contour curve of the tread surface that protrudes radially outward of the tire should be at least 2.5% of the tire radius in the central tread area, which accounts for 25-40% of the tread width centered on the equator of the tire
The radius of curvature is twice as large, and the tread side area continuously extending on both sides of the tread central area has a smaller radius of curvature than the radius of curvature in the tread central area, and furthermore, the tire rotation axis passing through the tread edge is reduced. Intersection of a perpendicular and a line parallel to the tire rotation axis through a point on the tread surface where the distance to the tread surface measured along this perpendicular is the largest,
A pneumatic radial tire with excellent steering stability, characterized in that the distance between the intersection of the vertical line and the extension of the contour curve of the tread side section is in the range of 5.5 to 7.5% of the tread width.

[0005] The above-mentioned tread width indicates an effective ground contact width when a specified load is applied after a tire is mounted on an applicable rim and a specified internal pressure is applied. Similarly, a tire radius is a half of an outer diameter of the tire. Show. Further, the extension of the contour curve of the tread side area indicates an imaginary line extending from the tread side area toward the tread edge at the same curvature as the tread side area.

FIG. 1 shows the structure of a tire according to the present invention in a cross section including the rotation axis of the tire. 1 in the figure
Is a carcass, 2 is a belt layer, 3 is a tread and 4 is a bead core. In the illustrated example, the tread 3 extends along the tread circumference and is substantially parallel to and spaced from the equator of the tire (tread of the tread). Circumference at center of width) O
The center part of the tread is divided into two rows of land portions 6 by two pairs of circumferential grooves 5 forming a pair on the left and right. In this example, at least one carcass 1 is wound around the bead core 4 from the inside to the outside of the tire (usually 1 carcass 1).
(2) turn-up plies, in which organic fiber cords represented by polyester, rayon and nylon are arranged in a direction (radial direction) substantially perpendicular to the equatorial plane of the tire. The belt layer 2 is made of a non-extensible cord typified by steel and an aromatic polyamide fiber at 10 to 40 ° with respect to the equatorial plane of the tire, preferably 15 to 35
At least two layers of belts arranged at an angle of ° cross each other. Then, the tread 3 is disposed on the belt layer 2.

Further, the tread 3 has a convex shape outward in the radial direction of the tire, and has a contour curve of the surface of the tread 3 in a cross section shown in the drawing, that is, a cross section including the rotation axis of the tire in a state where the normal internal pressure is applied after the normal rim is mounted. It is important that the following conditions are met. That is, the surface of the tread 3 has a radius of curvature A which is at least 2.5 times the tire radius r in a tread central area C occupying 25 to 40% of the tread width W centered on the equator O of the tire, and the tread central area C In the tread side area S continuously connected to both sides of the tread center section C and has a radius of curvature B smaller than the radius of curvature in the tread center area C. Further, the contour curve of the surface of the tread 3 is obtained by passing the perpendicular L of the tire rotation axis J passing through the tread edge T and the point on the tread surface at which the distance to the tread surface measured along the perpendicular L becomes the maximum. From the intersection P ₁ with the line H parallel to J, the tread side area S
K extending from the contour curve under the same curvature and the perpendicular L
The distance to the intersection P ₂ of a (hereinafter referred to as the tread edge drop)
is set in the range of 5.5 to 7.5% of the tread width W.

[0008]

In the tire according to the present invention, for example, the tread center area C and the tread side area S have different curvatures of the surface contour curves, and the tread edge drop is within a predetermined range, so that the contact pressure distribution can be improved. 3 is changed from the conventional shape shown in FIG. 2 to the shape shown in FIG. 3, and the behavior change near the limit of the tire is moderated. That is, if the contact pressure distribution is shaped as shown in FIG. 3, the generation of the grip force on the contact surface at the time of cornering becomes uniform, and the change in the grip force due to a change in the steering angle near the limit of the tire, disturbance from the road surface, etc. is reduced. Therefore, the behavior near the limit becomes gentle.

Here, the radius of curvature A in the tread central area C
The reason why the tire radius is at least 2.5 times the tire radius is that if it is less than 2.5 times, it is difficult to obtain a sufficient abrasion resistance and steering stability, particularly when a contact area required for a tire for a passenger car cannot be secured. On the other hand, the upper limit is preferably 8 times or less. Furthermore, the reason why the radius of curvature B in the tread side section S is A> B with respect to the above-mentioned radius of curvature A is that if A ≦ B, the protrusion of the tread central section C becomes large and the straight running stability is impaired. . Further, the reason why the tread edge drop δ is set to 5.5 to 7.5% of the tread width W is that if it is less than 5.5%, the contact pressure at the shoulder near the tread edge cannot be reduced, whereas if it exceeds 7.5%, the shoulder This is because the contact area is insufficient and the wear resistance and the steering stability are deteriorated.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Tire size 255 / 50R16 having the structure shown in FIG.
The pneumatic radial tire of No. was prototyped according to the specifications shown in Table 1. The circumferential grooves of these prototype tires were 11 mm in width and 8.5 mm in depth, and the transverse grooves crossing the circumferential grooves were 5 mm in width and 7.5 mm in depth. Polyester cord (1500 d
/ 2) on the outside of the carcass, which is a two-layer ply
Rubber belted steel cord (1x5 structure) is wound along the equator of the tire. Two layers of belt layers and 66 nylon (1260d / 2) arranged further outside of this belt layer are applied to the equator of the tire. And a single auxiliary belt layer (two layers on the tread side) wound along the auxiliary belt layer.

[0011]

[Table 1]

FIG. 4 and Table 2 show the results of the steering stability test and various feeling tests performed on actual tires on the tires thus obtained.

[0013]

[Table 2]

In the steering stability test, the side force generated was measured by changing the tire slip angle in the range of 0 to 15 ° using a flat belt type testing machine.
In the feeling test, when running on a test road with various corners with a corner radius of 20 to 150 m and wet and dry road surface conditions at a maximum speed of 180 km / h, Based on the ease of sensing the tail slide start point during cornering, the limit controllability is the controllability of the vehicle after the tail slide, that is, the tire is controlled while the tail slide state without spinning after the tail slide. Based on the ability to recover the grip of the vehicle and shift to normal driving, the behavior at the time of recovery depends on the behavior of the vehicle during the transition from running in the tail slide state to normal driving, whether the steering operation and the accelerator operation are smooth. The standard was used.

[0015]

According to the present invention, it is possible to easily understand the limit of the tire and to give a gentle characteristic of a change in behavior before and after the limit, and particularly to a tire which greatly contributes to the improvement of steering stability in a passenger car. Can provide.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a tire according to the present invention.

FIG. 2 is a graph showing a contact pressure distribution of a conventional tire.

FIG. 3 is a graph showing a contact pressure distribution of a tire according to the present invention.

FIG. 4 is a graph showing the results of a steering stability test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carcass 2 Belt layer 3 Tread 4 Bead core 5 Circumferential groove 6 Land part O Equatorial of tire T Tread end J Tire rotation axis

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-60404 (JP, A) JP-A-60-148702 (JP, A) JP-A-1-309805 (JP, A) JP-A-3-306 204309 (JP, A) Fully open Sho 61-35004 (JP, U) Fully open Sho 64-49402 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 11/00

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 reinforced with a carcass and further provided with a belt layer of a non-extensible cord extending over the entire width of the tread between the radial carcass and the tread arranged in the crown portion, wherein the tire is filled with a specified internal pressure after mounting the applicable rim. In the cross section including the rotation axis of the tire in the tired state, the contour curve of the tread surface projecting radially outward of the tire has a tread width centered on the equator of the tire.
The tread central area occupying 25 to 40% has a radius of curvature of at least 2.5 times the tire radius, and is smaller than the tread central area in the tread side area that is continuous on both sides of the tread central area. Has a radius of curvature,
Furthermore, the intersection of the perpendicular of the tire rotation axis passing through the tread end and the line parallel to the tire rotation axis passing through the point on the tread surface where the distance to the tread surface measured along this perpendicular is the largest, and The distance between the intersection of the extension line of the contour curve of the section area and the perpendicular line is 5.5 to 7.5 of the tread width.
% Of pneumatic radial tires having excellent steering stability.