JPH0999708A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reconcile excellent maneuvering stability with comfortableness to ride in by arranging anisotropic coating rubber in a carcass part, and arranging anisotropic rubber on which the ratio of a circumferential directional modulus to a radial directional modulus is set not less than a specific value, particularly, to increase circumferential directional rigidity of a tire as well as to reduce radial directional rigidity. SOLUTION: A single carcass ply 2 where a polyester cord is arranged in a radial shape of extending in a toroidal shape is arranged in a toroidal shape so as to stride over a pair of bead cores. A carcass has a folding-back part 2b to roll up the periphery of the bead cores besides a main body part 2a to reinforce respective parts. A belt 5 composed of rubber-coated layers of two layers and tread rubber 6 to cover an outside surface of this belt 5 are provided on the outer periphery of a crown part of this carcass ply 2. Here, in the case where anisotropic rubber is arranged in carcass coating rubber, when the ration (b/a) of a circumferential directional modulus (b) to a radial directional modulus (a) is set not less than 1.4, circumferential directional rigidity can be improved.

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 which achieves good steering stability, riding comfort and noise at the same time without increasing weight, and more particularly to a radial tire for passenger cars.

[0002]

2. Description of the Related Art Conventionally, in order to improve steering stability in a pneumatic radial tire, a means for arranging a reinforcing member made of an organic fiber or a metal fiber in a carcass has been adopted. However, with the above means, not only the cost increase due to the increase in weight and the deterioration of rolling resistance but also the riding comfort are deteriorated, and it is difficult to satisfy all of these.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The inventor has studied the improvement of rigidity in a carcass in order to satisfy both steering stability and riding comfort without using a reinforcing member. The carcass mainly consists of organic fibers or metal fibers and coating rubber.If a highly rigid material is used for the fiber members, the rigidity of the entire carcass will increase, and although the steering stability will improve, the riding comfort will deteriorate. Will end up. Therefore, the inventor tried to improve the carcass coating rubber.

Further, the inventor has found that the rigidity with respect to the input in the tire radial direction (hereinafter referred to as "tire radial rigidity"), and
A detailed examination was conducted by dividing the stiffness with respect to the input in the tire circumferential direction (hereinafter referred to as "tire circumferential stiffness"). As a result, it was found that the rigidity in the tire circumferential direction should be increased to improve the steering stability, and that the rigidity in the tire radial direction should be decreased to improve the riding comfort. did.

As described above, if the rigidity of the carcass-coated rubber in the circumferential direction of the tire is increased and the rigidity in the tire radial direction is reduced, both steering stability and riding comfort can be achieved without increasing the weight. However, conventionally, particularly in carcass coated rubber, tires having substantially the same tire radial rigidity and tire circumferential rigidity have been used, and it has been difficult to adjust the rigidity in each of the above directions with the carcass coated rubber.

[0006]

An object of the present invention is to dispose an anisotropic coating rubber on a carcass portion, and in particular to increase tire circumferential rigidity and decrease radial rigidity. (EN) A pneumatic radial tire in which an anisotropic rubber having a high circumferential modulus relative to a radial modulus is arranged to achieve both good steering stability and riding comfort, and particularly a radial tire for passenger cars.

As described above, the inventor arranges the anisotropic rubber having a circumferential modulus higher than the radial modulus in the carcass coating rubber to achieve both improved steering stability and riding comfort. As such an anisotropic rubber, a rubber produced by using an extruder or the like capable of producing an anisotropic rubber having a circumferential modulus higher than a radial modulus, or a rubber in which short fibers are arranged in one direction is used. It is possible if you do.

The term "modulus" as used herein means a value obtained by measuring 100% modulus by making the same test piece in a radial direction and a circumferential direction with a rubber member constituting a tire.

Next, in order to make a study for satisfying both steering stability and riding comfort without using a reinforcing member, the inventor divides the carcass into a main body portion and a folded portion in the conventional structure. Surveyed. As a result, it has been found that the folded-back portion located on the outer side in the tire axial direction has an effect of suppressing the carcass body portion from falling toward the outer side in the tire axial direction during cornering. Therefore, it has been found that steering stability is effectively improved by applying a coating rubber having anisotropy in which the modulus in the circumferential direction is higher than the modulus in the radial direction to the carcass folded portion.

Here, when the anisotropic rubber is arranged on the carcass coating rubber, the radial modulus a
The reason that the ratio b / a of the modulus b in the circumferential direction to 1.4 is 1.4 or more is that if it is 1.4 or more, the rigidity in the circumferential direction can be sufficiently improved and the steering stability is significantly improved.

When the noise such as road noise and harshness is emphasized, the coating rubber of the carcass in the main body portion has a modulus ratio b / a.
Is preferably less than 1.4.

Further, in the carcass turn-back portion,
The free end of the folded carcass has lower rigidity than the vicinity of the bead. Therefore, the modulus ratio b / a
However, it is more effective that the number increases from the vicinity of the bead core toward the carcass folded end.

Usually, when the rigidity of the bead portion needs to be strengthened, a bead filler is disposed so as to be close to the outside of the bead core in the tire radial direction. In this case, it is desirable that the bead filler and the carcass coating rubber having anisotropy at the folded-back portion overlap in the tire radial direction. Because, with the bead filler,
If there is a gap between the carcass-coated rubber that has anisotropy at the folded-back portion, a rigidity difference is created between the ends, and the tire deformation becomes excessive with the gap as an inflection point during cornering, resulting in sufficient steering stability. This is because the effect of improving the sex cannot be obtained.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION To confirm the above effects,
Several types of pneumatic radial tires having a tire size of 195 / 65R15 were prepared and the following tests were carried out.

First, a ride comfort test was conducted on a test course by running an actual vehicle at a speed of 40 to 80 km / h on a step road surface, a joint road surface, a Belgian road, and the like, and a feeling was evaluated by a test driver. For the evaluation, the control tire was evaluated by a 10-point perfect score method, and the other test tires were evaluated in ± 10 grades in comparison with the control tire.

In addition, the indoor noise was measured at the same time during the above running, and the evaluation was made with an index when the noise of the control tire at that time is 100. In this case, the smaller the index, the better.

Next, a steering stability test was carried out. Go straight on the actual vehicle at a speed of 60 to 120 km / h on the test course,
I made a lane change and made a circle turn to evaluate the feeling with a test driver. The evaluation was performed by the 10-point perfect score method and ± 10 grades as in the ride comfort test.

[0018]

Embodiment An embodiment of the present invention will be described with reference to FIGS.

Example 1 A tire according to the present invention has a tire cross section shown in FIG. 1, and a carcass ply 2 in which polyester cords are radially arrayed extending in a toroidal shape is formed in a toroidal shape across a pair of bead cores 3. The carcass has a folded-back portion 2b that winds up around the bead core 3 in addition to the main body portion 2a that reinforces the above-mentioned respective portions. 5, and a tread rubber 6 for covering the outer surface of the belt 5, the coating rubber of the carcass body 2a and the folded portion 2b has a ratio b / a of a radial modulus a and a radial modulus b.
An anisotropic rubber having a value of 1.6 was placed.

Example 2 The tire of the present invention has the same cross section as that of the tire shown in FIG. 1, and the modulus ratio b / of the carcass folded-back portion 2b is
An anisotropic rubber having a of 1.6 and a modulus ratio b / a of the carcass body 2a of 1.1 was arranged. Other structures and sizes are almost the same as those of the tire of Example 1.

Conventional Example 1 In this conventional tire, the anisotropic rubber is not arranged in the coating rubber of the carcass 2, and other structures and sizes are almost the same as those of the tire of Example 1. .

Example 3 The tire of the present invention has the same cross section as that of the tire shown in FIG. 2, has a bead filler 4 radially above the bead core 3, and has an anisotropy coating for the carcass folded-back portion 2b. The rubber and the bead filler 4 overlap in the radial direction. Other structures and sizes are almost the same as those of the tire of Example 2.

Conventional Example 2 In this conventional tire, the anisotropic rubber is not arranged in the coating rubber of the carcass 2, and the other structures and sizes are almost the same as those of the tire of Example 3. .

Comparative Example In this comparative tire, between the bead filler 4 and the coating rubber having the anisotropy of the carcass folded portion 2b,
It has a gap of 6 mm in the radial direction. Other than that, it is almost the same as the tire of Example 3.

[0025]

EFFECTS OF THE INVENTION The test results are shown in Table 1 below.

[0026]

[Table 1]

From the results shown in Table 1, it was confirmed that Examples 1, 2 and 3 can improve the steering stability without deteriorating the riding comfort as compared with other test tires. According to the invention,
Place an anisotropic coating rubber on the carcass part,
In particular, it is possible to provide a pneumatic radial tire in which an anisotropic rubber having a high modulus in the circumferential direction with respect to the modulus in the radial direction is arranged to achieve both good steering stability, riding comfort and noise.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of pneumatic radial tires of Conventional Example 1, Example 1, and Example 2 of the present invention.

FIG. 2 is a cross-sectional view of pneumatic radial tires of Conventional Example 2, Example 3, and Comparative Example of the present invention.

[Explanation of symbols]

 1 Pneumatic radial tire 2 Carcass ply 2a Carcass ply body 2b Carcass ply folding back 3 Bead core 4 Stiffener 5 Belt 6 Tread

Claims (5)

[Claims] 1. A carcass of at least one layer of radial ply for reinforcing a tread and a pair of sidewall parts connected to the bead part between the bead cores embedded in the pair of bead parts, wherein the carcass reinforces each part. In addition to the main body part, there is a folded part that winds up around the bead core, and the carcass coating rubber of the folded part has a large anisotropy in the radial modulus with respect to the circumferential modulus. Radial tires. 2. The coating rubber of the carcass turn-up portion has a ratio b / a of a circumferential modulus b to the radial modulus a that increases from the vicinity of the bead core toward the carcass turn-up end. 1. The pneumatic radial tire according to 1. 3. The air according to claim 1, wherein the coating rubber of the main body of the carcass has a ratio b / a of the circumferential modulus b to the radial modulus a of 1.0. Radial tires with. 4. The coating rubber of the folded back portion of the carcass has a ratio b / a of the circumferential modulus b to the radial modulus a of 1.4 or more. The pneumatic radial tire according to claim 1. 5. The bead filler, which is adjacent to the outer side of the bead core in the radial direction of the tire, and the carcass coating rubber having anisotropy in the folded portion overlap in the radial direction of the tire. The pneumatic radial tire according to claim 1.