JPH0995108A - Radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the riding comfortableness on a rough road, and prevent the follow-up property of a vehicle from worsening at the time when the steering angle is very small on a highway. SOLUTION: This tire is composed of a carcass consisting of at least one carcass ply containing cords inclined substantially at 90 degrees to the tire- equatorial plane, and two layers, each of which contains cords inclined at 22 to 40 degrees to the tire-equatorial plane. The tire is further provided with belts 3, 4 extended in the direction in which the cords of the two layers are crossed between the layers. In this case, a rubber layer 5 having a hardness of 60 degrees or more JIS Shoe A is arranged between the belts 3, 4 symmetrically with respect to the equatorial plane at a width of 25 to 44% of the total axial width BW of the belts 3, 4 and in thickness of 1 to 3.5mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire, and more particularly to improving the riding comfort of a radial tire for passenger cars on uneven roads.

[0002]

2. Description of the Related Art As a radial tire having a good ride comfort by reducing vibrations generated by contact with a road surface, particularly an uneven road surface, for example, a method of reducing the bending rigidity of a belt, A method of reducing the bending rigidity, a method of reducing the elastic modulus of the tread rubber, and the like are adopted.

[0003]

However, in the above method, although it is possible to obtain a good riding comfort, there is a drawback in that the steering stability is adversely affected. Particularly in the method of reducing the bending rigidity of the belt, which has a remarkable improvement effect, the following ability of the vehicle at the time of a small steering angle of the steering wheel deteriorates, and the high speed running has increased in recent years. Has become.

Therefore, an object of the present invention is to propose a radial tire that improves the riding comfort on uneven roads and does not deteriorate the followability of the vehicle at a small steering angle on a highway.

[0005]

In order to achieve the above object, a radial tire according to the present invention comprises a carcass consisting of at least one carcass ply including a cord forming substantially 90 degrees with respect to the equatorial plane of the tire. , Two-layer cord layers each including cords that form a relatively high angle of 22 to 40 degrees with respect to the equatorial plane of the tire, and these two-layer cord layers extend in a direction intersecting with each other. In a radial tire including a belt, a rubber layer having a JIS Shore A hardness of 60 degrees or more is symmetrically sandwiched between the belts with an equatorial plane interposed between the belts and the total axial width BW of the belt is 25 to 4
The width is 0% and the thickness is 1 to 3.5 mm.

[0006] As described above, the cords are composed of two layers each including cords forming an angle of 22 to 40 degrees, which is a relatively high angle with respect to the equatorial plane of the tire. By adopting the belt structure extending in the intersecting direction, it is possible to reduce the bending rigidity in the tire radial direction with respect to the protrusion as compared with the belt structure adopting a relatively low intersecting angle. However, by adopting such a structure, there is a drawback that the following ability of the vehicle at the time of a small steering angle of the steering wheel is deteriorated. Therefore, as a result of various studies, the inventor has obtained the following findings. That is, (1) even if the belts are crossed at a relatively high angle to reduce the bending rigidity of the belt portion, the followability of the vehicle at the time of a small steering angle of the steering wheel is deteriorated, and other required performances are at a practical level. is there. (2) In order to improve the riding comfort on the uneven road, it is more effective to reduce the bending rigidity of the belt axially outer side portion of the belt portion than to reduce the bending rigidity of the central portion of the belt portion. (3) In order to improve the followability of the vehicle when the steering wheel has a small steering angle, the bending rigidity of the central portion of the belt portion in the tire axial direction may be increased. (4) As a means for increasing the bending rigidity of the central portion of the belt portion described above, as a method that can be easily manufactured, JIS between belts is used.
A rubber layer having a Shore A hardness of 60 degrees or more is provided between the belts with a width of 25 to 40% of the total axial width BW of the belt and a thickness of 1 to 3.
It has been proved to be effective if they are arranged at 5 mm.

The rubber layer having a JIS Shore A hardness of 60 degrees or more is used because at least this hardness is necessary to increase the bending rigidity of the belt portion. The upper limit of hardness is
If the hardness is too high, heat generation deteriorates, causing failure, or rolling resistance of the tire increases, so the upper limit is about 70 degrees. Also, the width of the rubber layer is 25 to 4 with respect to the belt width.
The reason for setting it to 0% is that if it is 25% or less, the bending rigidity of the central portion of the belt portion cannot be sufficiently increased, and if it is 40% or more, the belt portion rigidity becomes too high as a whole to improve the riding comfort. Moreover, the thickness of the rubber layer is 1 to 3.5 m.
Similarly to the above, the value of m is 1 mm or less, so that the bending rigidity of the central portion of the belt portion cannot be sufficiently increased,
If it is 3.5 mm or more, the weight is increased and rolling resistance is increased, which is not preferable.

The rubber layer is arranged between the first belt and the second belt so that the rubber layer can be prevented from flowing to other portions due to pressure during vulcanization, and the first rubber layer can prevent the rubber layer from flowing. This is because the deformation of the belt and the second belt due to the external force can be suppressed at the same time.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The tires prototyped as examples are
The tire shown in FIG. 1 has a tire size of 195 / 65R1.
The width of the first belt 3 buried in the tire is 180 mm, which is made by rubberizing the steel cord, and the width of the second belt 4 is 170 mm.
A rubber layer 5 having a hardness of 65 degrees is used, and as shown in Table 1, three types of prototypes were manufactured. For comparison, three types of tires having the same size according to the structure shown in FIG. 2 were manufactured as comparative examples except that the rubber layer 5 was removed as shown in Table 1 except that the tires were the same.

The test was carried out on 6 tires of each of the above 6 sets.
The JJ-14 rim was assembled and filled with an internal pressure of 2.0 kg / cm2 and mounted on a domestic 2000 cc passenger car. Sensory evaluation was performed on the followability of the. The results are also shown in Table 1. Here, the evaluation criteria are as follows. ⊚: Good, ◯: No problem in practical use, Δ: There is a problem in practical use (+ and − are more finely divided into good and poor)

[0011]

[Table 1]

As is apparent from the above, according to the present invention, it is possible to improve the riding comfort while improving the followability of the vehicle at the minute steering angle. Here, it was also clarified that if the steering stability is emphasized, the inclination angle of the belt with respect to the tire equatorial plane should be small, and if the riding comfort is emphasized, the opposite is preferable.

[0013]

As is apparent from the above description, according to the present invention, it is possible to improve the riding comfort while improving the followability of the vehicle at the minute steering angle.

[Brief description of drawings]

FIG. 1 is a sectional view in a tire width direction showing an application example of the present invention.

FIG. 2 is a sectional view in the tire width direction of a conventional example.

[Explanation of symbols]

 1 Radial tire 2 Carcass 3 First belt 4 Second belt 5 Rubber layer

Claims (1)

[Claims] 1. A carcass comprising at least one carcass ply including a cord forming substantially 90 degrees with respect to the tire equatorial plane, and a cord forming an angle of 22 to 40 degrees with respect to the tire equatorial plane. A radial tire comprising a belt composed of two cord layers, and a belt in which the cords of the two layers extend in a direction intersecting with each other, in a JIS Shore A hardness symmetrically with an equatorial plane sandwiched between the belts. A rubber layer of 60 degrees or more is used to measure the total width B of the belt in the axial direction.
A radial tire having a width of 25 to 40% of W and a thickness of 1 to 3.5 mm.