JPH0367701A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To increase the cornering power of a pneumatic radial tire and to improve its stability in operation by specifying the relation of radii of curvature of the ground center of a tread part of a tire, a shoulder side end of an outermost layer of a belt and a carcass layer at a position of the largest width thereof. CONSTITUTION:A radial tire has a tread portion 1, side wall portions 5 at both of right and left sides, a carcass layer 3 turned around a bead core 4 and belt layers 2u, 2d extending circumferentially, of the tire disposed at the tread portion 1 of the carcass layer 3. In this case, when the tire is mounted on a rim and normal internal pressure is filled, radii R1, R2, R3 of curvature of the ground center of the tread portion 1, the shoulder side end of an outermost layer of a belt and the carcass layer at a position of the largest width of the carcass layer satisfy R1 > R2 > R3 and the ratio of height h at the position of the largest width of the carcass layer to height H in section of the carcass layer determined in the direction orthogonal with an axis of rotation of the tire from a bead base is set so as to obtain h/H of 0.58 to 0.64.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a pneumatic radial tire (hereinafter referred to as a radial tire), and more specifically, it relates to a pneumatic radial tire (hereinafter referred to as a radial tire), and more specifically, a pneumatic radial tire that has excellent handling stability and uneven wear resistance, and is durable. Concerning improved radial tires.

[Conventional technology]

Conventionally, it has been known that the carcass line shape of a radial tire has a large effect on the tire's rolling resistance, riding comfort, handling stability, wear resistance, and other properties.

For example, Japanese Patent Application Laid-Open No. 59-48204 discloses, as shown in FIG. 3, when the internal pressure is filled to 5% of the normal internal pressure shown by the dotted line and when the normal internal pressure is filled to the normal internal pressure shown by the solid line.
The degree of change in the carcass line in the upper region from the maximum width point of the carcass layer to the crown portion and the lower region from the maximum width point to the bead portion is different, and the degree of change in the carcass line in the upper region is different from that in the lower region. A radial tire is disclosed in which the carcass line changes significantly.

However, in this radial tire, although the belt tension is large at the center of the tread when it is filled with the normal internal pressure, the belt tension decreases toward the shoulder side edge and the apparent rigidity decreases. The power was low and the handling stability did not improve. In addition, as mentioned above, the heald tension between the center part of the tread and the shoulder side edge is different, and the tension in the width direction of the heald layer is uneven, resulting in a large side force being applied during sharp cornering, etc. In some cases, buckling (wavy deformation) is likely to occur in the tread portion, which poses a problem in durability.Furthermore, since the belt tension at the shoulder side end is low, shoulder wear is likely to occur.

[Problem to be solved by the invention]

An object of the present invention is to provide a radial tire that has excellent handling stability and improved uneven wear resistance and durability.

[Means to solve the problem]

The object of the present invention is to provide the carcass layer at the ground contact center of the tread portion, the shoulder side end of the outermost layer of the belt, and the maximum width position of the carcass N when the radial tire is mounted on a regular rim and filled with a regular internal pressure. radius of curvature R
1 R2 and R8 satisfy R+ > Rz > R3, and the ratio h/H of the height h at the maximum width position of the carcass layer to the cross-sectional height H of the carcass layer measured from the bead base in a direction perpendicular to the axis of rotation of the tire. This can be achieved by using a radial tire with a ratio of 0.58 to 0.64.

Here, the regular internal pressure and regular rim refer to the regular internal pressure and regular rim specified by the Japan Automobile Tire Association Standards (JATMA).

Moreover, the carcass line refers to the shape obtained as follows. That is, after filling the tire with the proper internal pressure and stabilizing the shape of the tire in an inflated state, plaster is applied to the outer circumference of the tire and a mold is made. On the other hand, by cutting the tire in the radial direction and drawing the cross-sectional shape of the tire along the molded outer shape of the tire, the carcass line of the tire when inflated is specified.

A detailed description will be given below with reference to the drawings.

As shown in FIG. 1, the radial tire of the present invention includes a pair of bead portions on both left and right sides, a pair of sidewall portions 5 on both left and right sides connected to the bead portions, and a cord angle of substantially 90' with respect to the tire circumferential direction. The bead core 4 of the bead portion
a carcass layer 3 folded back from the inside to the outside of the tire around the carcass N3, two belt layers 2u and 2d extending in the tire circumferential direction disposed on the tread portion 1 of the carcass N3, and the pair of left and right sidewall portions 5. It consists of a tread portion l extending outward in the radial direction.

In the radial tire of the present invention having such a structure, the change in the carcass line between when the tire is inflated with the regular internal pressure and when the tire is inflated with the regular internal pressure is not particularly limited, but For example, it is desirable to have a carcass line shaped like the dotted line in Figure 2 when the normal internal pressure is not filled, and a carcass line shaped like the solid line after filling the normal internal pressure. By filling the internal pressure, the tire extends outward from the tire's maximum width position on the bead side B, and retracts inside the tire on the shoulder part side S, resulting in R, >
The carcass line satisfies R. However, in any case, the carcass line shape after normal internal pressure filling is R,>R,>R, and the ratio h/H=
It is important that it is between 0.58 and 0.64.

In order to provide the tire of the present invention having the above-mentioned characteristics, a layer made of steel cord is used as the belt layer, and the belt layer is composed of a plurality of layers whose narrowest width is 100x to 110x of the tread contact width. In addition, the innermost belt layer 2
A wedge-shaped rubber filler 7 is arranged between the shoulder side end of d and the carcass layer 3, and the carcass layer 3 at this position is
is preferably directed inward by 2 to 4 mm, while the maximum width position of the carcass layer is preferably located above the tire maximum width position by Δh. Moreover, the thickness of the tire case (rubber thickness) is made to be the thinnest at the maximum width position of the carcass layer 3. Also, the thickness of the tire case at the bead portion including the bead core is made to be the thickest in the sidewall in the area where it contacts the rim flange. Furthermore, the shape of the belt layer is made to be a curved line substantially parallel to the tread surface.

Now, in a radial tire, the relationship between this heald tension t and the radius of curvature R is t OCp R when the internal pressure is p, so the shape of the carcass line satisfies the above R2>R, and the belt layer is treaded. The tire of the present invention, which has a curved shape approximately parallel to the surface, maintains the maximum belt tension at a high level at the ground contact center CL of the tread portion without significantly reducing it even at the shoulder side end, and has a high apparent rigidity. increase Therefore, cornering power can be increased and steering stability can be improved.

Furthermore, since the belt tension at the shoulder side end of the heald layer is maintained high, uneven wear on the shoulder portion of the tread is reduced. Furthermore, since the heald tension at the shoulder side end of the belt layer is maintained at a high level and the difference with the heald tension at the tread center contact area CL is made small, the tension in the width direction of the belt layer becomes uniform and the tread bank The critical side force generated by the ring increases.

Therefore, the heald layer is less likely to be deformed, resulting in improved durability.

As mentioned above, the height h of the maximum position of the carcass layer measured from the bead base BB in the direction perpendicular to the rotational axis of the tire of the tire of the present invention is 0.58 to 0 of the cross-sectional height H of the tire.
．． The position is 64 times larger. When the tire maximum width position is lower than 0.58 times the cross-sectional height H of the carcass layer, the above-mentioned R, >R, >R specified in the present invention is satisfied, and the heald layer is on the surface of the tread portion. It is not possible to draw substantially parallel ll1J lines, and it is not possible to sufficiently improve the belt tension in a part of the shoulder side center. Also,
Tires with h/H exceeding 0.64 times are difficult to manufacture and are not practical.

〔Example〕

Hereinafter, the tire of the present invention will be explained in more detail with reference to Examples.

Regular internal pressure (1, 9 corresponding to JATMA design regular load)
R, , R2 and R3 when filled with Kg/c- air pressure) are R+ = 230 mm and R2 = 200 m, respectively.
Tire I of the present invention was prepared, with m, R1-40 mm, h/H=0.64, and having the structure shown in FIG.

Further, in the tire I of the present invention, R1+RZ+R.

Three types of radial tires were prepared: the present invention tire (2), comparative tires I, and (2), in which the and h/H were changed as shown in the table.

The size of these tires was 155SR13.

These four types of tires were each mounted on a 13X/1.5J rim, and the following steering stability, durability, and uneven wear resistance were evaluated, and the results are shown in the table.

(2) Cornering performance: Evaluation was made by cornering force at a load of 300 kg and a slip angle of 1 degree using an indoor flat plate tester.

The measurement results were expressed as an index with the measured value of Comparative Tire I set as 100. The larger this index value is, the better the steering stability is.

Rainbow fatigue: The tire was rotated on transparent glass under a load of 460 kg and a slip angle, and the tire was observed from below the transparent glass and evaluated based on the critical side force at which bank ring occurs on the tread surface.

The measurement results were expressed as an index with the measured value of Comparative Tire I set as 100. The larger the index value, the better the durability.

Random movement: An actual vehicle was driven in an excessive circular turn (figure 8) with a load of 308 kg per tire, and the amount of J'1 in a part of the shoulder of the tire was measured after traveling 60 km. It was evaluated.

The measurement results were expressed as an index, with the measured value of comparative tire ■ being set as 100. The smaller this index value is, the better the uneven wear resistance is.

As can be seen from the table above, both tires of the present invention ■ and ■
Compared to comparison tires ■ and ■, it has greater cornering power, excellent handling stability, and excellent uneven wear resistance. In addition, the tread buckling side force is high and deformation of the tread surface is suppressed, resulting in improved durability.

〔Effect of the invention〕

As explained above, according to the present invention, the radius of curvature R1 of the carcass layer at the ground contact center of the tread portion of the tire filled with normal internal pressure, the shoulder side end of the outermost belt layer, and the maximum width position of the carcass layer, respectively. , R2 and R
By specifying the relationship 1 and the ratio h/H of the cross-sectional height H of the carcass layer and the height h of the maximum width position of the carcass layer,
Since the belt tension at the shoulder side end is maintained at a high level without being reduced, cornering power is increased, steering stability is improved, and uneven wear on a portion of the shoulder is reduced. Moreover, since the belt tension in the width direction from the center of contact with the tread area to the shoulder side edge is almost uniform, the tread-buttering side force of the belt layer is improved, the belt layer is less likely to deform, and durability is improved. .

[Brief explanation of drawings]

FIG. 1 is a half-sectional view of the tire of the present invention, FIG. 2 is a half-sectional view of an example of the carcass line of the tire of the present invention, and FIG. 3 is a half-sectional view of the carcass line of a conventional tire. 1... Tread portion, 2u, 2d... Belt layer, 3.
... Carcass layer, 4... Bead core, 5... Side wall part. Figure 1

Claims (1)

[Scope of Claims] A pair of bead portions on both left and right sides, a pair of sidewall portions on both left and right sides connected to the bead portions, a tread portion extending radially outward of the sidewall portions, and a bead core of the bead portions. A radial tire comprising at least one carcass layer folded around the tire from the inside to the outside, and at least two belt layers disposed on the tread portion of the carcass layer, When attached to the rim and filled with normal internal pressure, the radii of curvature R_1, R_2, and R_3 of the carcass layer at the center of ground contact of the tread portion, the shoulder side end of the outermost belt layer, and the maximum width position of the carcass layer are R_1>R_2. >R_3, and the ratio h/H of the height h at the maximum width position of the carcass layer to the cross-sectional height H of the carcass layer measured from the bead base in a direction perpendicular to the rotational axis of the tire is 0.58 to 0. 64 pneumatic radial tires.