JPH05229308A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve operational stability with buckling eliminated by forming a tread surface with three circular arcs, having given relations of radiuses of curvature each other, over from a tread center to a shoulder part in a tire meridian direction cross section. CONSTITUTION:A tread surface of a tire meridian direction cross section is formed with circular arcs having radiuses of curvature of R1, R2, and R3 respectively, and a distance from a tread center TC to the intersection point of curved surfaces of R1 and R2, a distance between intersection points of curved surfaces of R1 and R2 also R2 and R3, and a distance from the intersection point of curved surfaces of R2 and R3 to a shoulder part are named as K1, K2, and K3 respectively. Here, respective relations, when a tread extension width TDW is made 200 mm or more, are made as follows: R1=11.5XTDW+(-1800--1950); R2=3XTDW+(-250--400); R3=0.5XTDW+(20--20); K1, and K2, and K3 are 45-55%, 25-35%, and 17-23% of TDW/2; and R1/R2<=5, R2/R3<=5. Consequently buckling is eliminated to improve operational stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having a tread surface having a ground contact shape optimized for improved steering stability, and more particularly to a pneumatic radial tire having suitable performance as a racing tire. It is a thing.

[0002]

2. Description of the Related Art Conventionally, in pneumatic radial tires having a tread expansion width of 200 mm or more, especially racing tires, the tread surface has a two-step radius (curvature) from the tread center (tire equatorial line) to the shoulder in the tire meridian direction cross section. Radius) It is composed of an arc of R1 and R2. The ratio R2 / R1 between the radius R1 on the inner side in the tire width direction and the radius R2 on the outer side in the tire width direction is usually as small as 0.1 to 0.2.

Therefore, there is a large change in the radius of the tread surface near the intersection (inflection point) of the arc of curvature radius R1 and the arc of curvature radius R2, which causes buckling near this inflection point. There is a problem that the ground contact is hindered. That is, the tread surface ground contact shape 11 shown in FIG.
As can be seen from the contact pressure distribution 12 and the contact pressure distribution 12, the conventional pneumatic radial tire has a high ground contact pressure (contact pressure) near the shoulder S and the tread center TC. Since the surface pressure of the portion 15 mm inside, that is, the portion corresponding to the inflection point C tends to be extremely low, this inflection point C triggers buckling. This tendency was particularly remarkable in slick tires, because the tread surface does not have a tread pattern, and the change in radius near the inflection point cannot be canceled by the groove.

As described above, when there is a buckling tendency portion having a low surface pressure near the inflection point of the tread surface, when the tire changes the camber while the vehicle is running, that is, from a straight line to a corner or a corner. There was a risk that the behavioral changes would be large when the vehicle moved from a straight line to a straight line, resulting in extremely unstable steering stability.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems with the conventional pneumatic radial tires, and is an air system in which buckling is eliminated to improve steering stability. The purpose is to provide a radial tire with the inside.

[0006]

A pneumatic radial tire of the present invention comprises a tread surface formed of three arcs having radii of curvature R1, R2, and R3 from a tread center to a shoulder portion in a tire meridian section. The distance from the tread center on the tread surface to the intersection of the arc of curvature R1 and the arc of curvature R2 is K1, and from this intersection the arc of curvature R2 and the curvature radius R
When the distance to the intersection with the circular arc of 3 is K2 and the distance from this intersection to the shoulder end is K3 and the tread development width TDW is 200 mm or more, these are characterized by the following relationships.

R1 = 11.5 × TDW + (− 1800 to −1950) R2 = 3 × TDW + (− 250 to −400) R3 = 0.5 × TDW + (20 to −20) K1 is 45% to 55% of TDW / 2 K2 Is 25% to 35% of TDW / 2. K3 is 17% to 23% of TDW / 2. R1 / R2 ≦ 5, R2 / R3 ≦ 5 Thus, in the present invention, the radius of the arc forming the tread surface has three stages. And these radiuses R1 and R
Since the relationship between 2, R3 and K1, K2, K3, and TDW is defined, the radius of the tread surface changes gradually, and the contact shape becomes a shape close to a normal ellipse, so a uniform contact pressure distribution is obtained. Obtainable.

Therefore, in the pneumatic radial tire of the present invention, the deformation of the ground contact shape on the tread surface, especially the deformation of the ground contact shape due to the camber change is small, and the behavior change during running is suppressed, so that the steering stability is excellent. And has ideal performance as a racing tire. In the present invention, the reason why the radius is set to 3 steps and not 4 steps or more is that the effect is not particularly excellent compared to the case of 3 steps even if it is 4 steps or more, let alone 4 steps or more in tire manufacturing. Because the design of is complicated.

The structure of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a cross-sectional explanatory view in the meridian direction of an example of the pneumatic radial tire of the present invention, and FIG. 2 is an explanatory view showing the ground contact shape of the tread surface thereof. In FIG. 1, a pneumatic radial tire of the present invention comprises a cylindrical crown portion 1 forming a tread T, a pair of side portions each extending radially inward from both ends of the crown portion 1 and having a bead wire 2 embedded in a tip portion thereof. The wall 3 is continuous in a toroidal shape, and a portion extending from one side wall 3 to the crown portion 1 and the other side wall 3 is reinforced with a carcass 4, and both ends of the carcass 4 are inwardly axially inward around the bead wire 2 respectively. Winding outward from the carcass 4
The bead filler 5 is disposed between the winding portion and the winding portion, and two belt layers 6 in which cords intersect with each other between the plies are disposed outside the carcass 4 of the crown portion 1. ..

In the present invention, as shown in FIG. 1, the surface of the tread T, that is, the tread surface, is formed by three arcs having radii of curvature R1, R2, and R3 from the tread center TC to the shoulder portion in the tire meridian section. ing. These three arcs, the distance K1 from the tread center TC on the tread surface to the intersection of the arc of curvature radius R1 and the arc of curvature radius R2, the intersection of the arc of curvature radius R2 and the arc of curvature radius R3 from this intersection The following relationship is defined with respect to the distance K2, the distance K3 from this intersection to the shoulder end, and the tread development width TDW. The tread width TDW is 2
Greater than 00 mm, especially suitable for 230-380 mm tires.

R1 = 11.5 × TDW + (− 1800 to −1
950). When R1 is less than 11.5 × TDW + (-1800), the tread radius becomes too small, the contact length is long, the contact width is narrow, and the surface pressure distribution is high in the center and the shoulders are low, leading to a decrease in cornering force. , Turning performance is reduced. Also, 11.5 × TDW + (-1950)
If it exceeds, the tread radius will be too large, the contact length will be short, the contact width will be wide, the surface pressure distribution will be low at the center, and the shoulders will be high, so buckling will easily occur at the center and steering stability Is reduced.

R2 = 3 × TDW + (− 250 to −400)
To be. If R2 is less than 3 × TDW + (− 400), the rate of change with R1 becomes too large, buckling is likely to occur near the contact points of R1 and R2, and the surface pressure distribution is not uniform. This leads to a decrease in stability. 3 x TDW +
If it exceeds (-250), the rate of change with R3 increases, and R2
Buckling is likely to occur near the contact points of R3 and R3. A conventional tire has R1 as large as R2.

R3 = 0.5 × TDW + (20 to −20). If R3 is less than 0.5 × TDW + (− 20), the rate of change with R2 becomes large, and the surface pressure distribution near the contact tends to become uneven. Therefore, the steering stability is likely to deteriorate and the shoulder portion is likely to wear early. Also, 0.5 x TDW +
When it exceeds (20), the amount of depression (P1) of the shoulder portion tends to be insufficient, the surface pressure distribution becomes non-uniform, and the steering stability is deteriorated.

K1 is 45% to 55% of TDW / 2. On the other hand, if K1 is less than 45% of TDW / 2, K2 or K2
3 becomes large, the amount of depression (P1) of the shoulder point P becomes large, and sufficient ground contact pressure cannot be obtained up to the shoulder portion. If 55% of TDW / 2 is exceeded, K2 or K3 becomes smaller, the amount of depression (P1) at the shoulder point P is small, the ground contact pressure at the shoulder increases, and the buckling at a position 10 to 15 mm from the shoulder should be erased. Can't do enough.

K2 is 25% to 35% of TDW / 2. When K2 is less than 25% of TDW / 2, R2 for relaxing the difference in radius between R1 and R3 does not exert sufficient effect due to the short K2, and the surface pressure in the area of R2 decreases, causing buckling. It tends to occur. A tire having K2 of 0 is a conventional tire. When it exceeds 35% of TDW / 2, the width of the intermediate radius R2 becomes wider, the amount of depression (P1) of the shoulder point P increases, and the surface pressure in the portion from the intermediate region R2 to the shoulder decreases greatly, The pressure is not uniform.

K3 is 17% to 23% of TDW / 2. If K3 is less than 17% of TDW / 2, the width of R3 becomes insufficient, the surface pressure increases from the inflection point of R2 and R3 to the R3 portion, and the ground contact shape is not improved from the conventional tire. TDW
If it exceeds 23% of / 2, the width of the shoulder radius R3 becomes too wide and the amount of depression of the shoulder point P (P
1) becomes too low. Therefore, there is a drawback that the ground contact width cannot be made sufficiently wide and the performance is deteriorated.

R1 / R2 ≦ 5 and R2 / R3 ≦ 5. When R1 / R2> 5 and R2 / R3 ≦ 5, R1 / R2 ≦
5, R2 / R3> 5, or R1 / R2> 5, R
In the case of 2 / R3> 5, the change rate of the radius of R1 to R2 and R2 to R3 becomes large, causing non-uniformity of the surface pressure in the vicinity of each contact point, and buckling is likely to occur.

By constructing the tread surface in this way, the tread surface ground contact shape 10 and the surface pressure distribution of FIG. 2 are obtained.
As shown in Fig. 12, the contact pressure distribution of the contact surface becomes a shape close to an ellipse, which suppresses the occurrence of the extremely low contact pressure portion such as the conventional pneumatic radial tire described above. It is possible to ensure steering stability. In addition,
The distance from the shoulder point P to the end of the shoulder part (P1) is 12 mm
It is more preferably 13 to 15 mm or more.

[0019]

[Example] For a pneumatic radial tire having a tire size of 260/700 R18 and a tread development width TDW = 264 mm,
Using 1500 D / 2 polyester cord as the carcass and 2 + 2 (0.25) steel wire cord as the belt layer, the tread surface from the tread center TC to the shoulder is made into a three-step radius as shown in FIG. At the same time, the tire 1 of the present invention was obtained by setting each R1, R2, R3 and K1, K2, K3 to the numerical values (mm) shown in Table 1. In this case, R1 / R2 = 2.33, R2 / R3
= 3.46.

On the other hand, for comparison, with respect to the tire similar to the above, the tread surface from the tread center TC to the shoulder portion is formed into a two-step radius as shown in FIG. 3, and each R1, R2 and K1, K2 is used. The conventional tire 1 was obtained by setting the value to be the value (mm) shown in Table 1.
In this case, R1 / R2 = 10. These two types of tires were mounted on a rim of size 18 × 10J, the internal pressure was set to 1.6 kg / cm ² cold, and the ground contact shape of the tread surface was observed, and the test was carried out by the method shown below to stabilize the steering. The sex was evaluated. The results are also shown in Table 1.

Evaluation of driving stability Test method : Evaluation was carried out by mounting a test tire on a Gr-A specification vehicle and traveling at high speed on a circuit course. The content of the evaluation was the driver's feeling evaluation, lap time, and one corner was selected, and the evaluation was made on the three items of the passing time of that corner.
The results are shown as an index with the value of Conventional Tire 1 being 100. The larger the number, the better.

[0022] As is clear from the results of Table 1, the pneumatic radial tire of the present invention has a uniform contact surface pressure and suppressed buckling, and exhibits excellent steering stability.

[0023]

As described above in detail, in the pneumatic radial tire of the present invention, the deformation of the ground contact shape on the tread surface, especially the deformation of the ground contact shape due to the camber change is small, and the behavior change during running is suppressed. Therefore, it has excellent steering stability and is suitable as a racing tire.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view in the meridian direction of an example of a pneumatic radial tire of the present invention.

FIG. 2 is an explanatory diagram showing a ground contact shape and a surface pressure distribution on a tread surface in a pneumatic radial tire of the present invention and a conventional pneumatic radial tire.

FIG. 3 is a cross-sectional explanatory view in the meridian direction of an example of a conventional pneumatic radial tire.

[Explanation of reference numerals] 1 crown portion, 2 bead wire, 3 sidewall, 4 carcass, 5 bead filler, 6
Belt layer.

Claims (1)

[Claims] 1. A tread surface is formed by three arcs of curvature radii R1, R2, and R3 from a tread center to a shoulder portion in a tire meridian section, and an arc and a curvature of curvature radius R1 from the tread center on the tread surface. The distance to the intersection with the arc of radius R2 is K1, and from this intersection the arc of curvature radius R2 and the curvature radius R
A pneumatic radial tire having the following relationship when the distance from the intersection with the circular arc 3 is K2, the distance from the intersection to the shoulder end is K3, and the tread development width TDW is 200 mm or more. R1 = 11.5 x TDW + (-1800 to -1950) R2 = 3 x TDW + (-250 to -400) R3 = 0.5 x TDW + (20 to -20) K1 is 45% to 55% of TDW / 2 K2 is TDW / 25% to 35% of 2 K3 is 17% to 23% of TDW / 2 R1 / R2 ≦ 5, R2 / R3 ≦ 5