JP2000071714A - Pneumatic radial tire for motor vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for a motor vehicle that realizes improvement of riding comfort and weight reduction without sacrificing controlling stability. SOLUTION: A carcass 2 is formed of a ply as an organic fiber chord arranged across the distance between a pair of bead cores 1, 1 in the radial direction, which serves as a framework. In the pneumatic radial tire, a crown portion of the carcass 2 is reinforced using a belt of a plurality of layers. The crown portion of at least one ply of the carcass 2 has a missing part 5. A carcass auxiliary layer 6 is provided close to the missing part 5.

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 for a passenger car, which has both driving stability and ride comfort.

[0002]

2. Description of the Related Art In pneumatic radial tires for passenger cars,
It is customary to ensure both ride comfort and steering stability by forming the carcass from one to three plies of organic fiber cord.

[0003] In recent years, since passenger cars have a strong tendency to be upgraded, further improvement in riding comfort of tires for passenger cars has been desired.

[0004]

However, the riding comfort and the driving stability are in a trade-off relationship, that is, the driving stability generally deteriorates when the riding comfort is improved. There is a need for a new way to achieve both driving stability and stability.

Accordingly, an object of the present invention is to provide a pneumatic radial tire for a passenger car which realizes improvement in ride comfort and weight reduction without sacrificing steering stability.

[0006]

Means for Solving the Problems The inventors of the present invention reviewed the basic structure of tires to achieve both steering stability and ride comfort. To improve ride comfort, the carcass under the belt was improved. It is advantageous to reduce the stiffness of the tire crown by removing it, by making up for the belt width direction stiffness of the part from which the carcass has been removed by appropriate means,
They have respectively found that excellent steering stability can be maintained, and have completed the present invention.

That is, the gist of the present invention is as follows. (1) A pneumatic radial tire for a passenger car in which a carcass composed of a ply of organic fiber cords arranged in a radial direction across a pair of bead cores is used as a skeleton, and a crown portion of the carcass is reinforced with a plurality of layers of belts. And
A pneumatic radial tire for a passenger car, wherein at least one ply of the carcass has a cutout portion in a crown portion thereof, and a carcass auxiliary layer is provided adjacent to the cutout portion.

(2) The pneumatic radial tire for a passenger car according to (1), wherein the elastic modulus of the carcass auxiliary layer is lower than the elastic modulus of the carcass.

(3) In the above (1) or (2), the length of the carcass lacking portion in the tire width direction is equal to the maximum width of the belt of 20%.
A pneumatic radial tire for a passenger car, characterized in that the tire is 70%.

(4) The passenger car according to any one of the above (1) to (3), wherein the carcass auxiliary layer is formed by coating a plurality of organic fiber cords having a diameter of 0.1 to 0.3 mm with rubber. Pneumatic radial tires.

(5) The pneumatic radial tire for a passenger car according to (4), wherein the organic fiber cord has a melting point of 150 ° C. or less.

(6) The pneumatic radial tire for a passenger car according to any one of the above (1) to (5), wherein a belt reinforcing layer is provided on at least a side of the belt in a radial direction so as to cover at least a side of the belt. .

[0013]

FIG. 1 shows a cross section of a pneumatic radial tire for a passenger car according to the present invention, wherein 1 is a bead core, 2 is a carcass, 3 is a belt, and 4 is a tread.

The carcass 2 is composed of one or a plurality of plies made of organic fiber cords arranged radially across a pair of bead cores 1, and at least one ply has a cutout 5 in its crown. That is important. That is, by removing the crown portion of the carcass 2 and giving flexibility to the tire crown portion,
Vibration from the road surface is absorbed by the tire crown to achieve improved ride comfort and reduced noise. Also, the missing part 5
Is to reduce the amount of carcass material, so that weight reduction is also realized.

Here, it is preferable that the missing portion 5 has a length D in the tire width direction of 20 to 70% of the maximum width L of the belt 3 around the tire equatorial plane O. If the length D of the missing portion 5 is less than 20%, the effect of improving the ride comfort cannot be sufficiently obtained, while if it exceeds 70%, the function as a carcass for maintaining the tire air pressure is hindered, and the durability of the tire is deteriorated. Is reduced.

On the other hand, a missing portion 5
In such a case, the rigidity of the tire is reduced, and the steering stability is deteriorated. Therefore, at least the missing portion 5 is provided adjacent to the missing portion 5 and radially outside the
Is provided with a carcass auxiliary layer 6 having a width sufficient to cover the layer. The carcass auxiliary layer 6 is provided on the belt 3 at the tire crown.
This is intended to suppress the deterioration of steering stability by compensating for the rigidity in the width direction of the vehicle.

When the carcass auxiliary layer 6 supplements the rigidity of the belt 3 in the width direction, if the rigidity is excessively increased, there is a possibility that the above-described effect of improving the ride comfort by the missing portion 5 may be reduced. Therefore, it is preferable to use the carcass auxiliary layer 6 whose elastic modulus is lower than that of the carcass 2. Specifically, about 1 to 30 kgf / mm is recommended.

In particular, the carcass auxiliary layer 6 is
It is advantageous to work so as to maintain steering stability by mainly compensating for the tensile rigidity in the width direction of the above, while maintaining the steering stability without affecting the bending rigidity. It is. For that purpose, it is preferable that the thickness of the carcass auxiliary layer 6 is thin, specifically, 0.5 mm or less. However, if the thickness of the carcass auxiliary layer 6 is less than 0.1 mm, the diameter of the organic fiber cord disposed on the reinforcing layer becomes small, and it becomes difficult to obtain the tensile rigidity required for maintaining steering stability. Preferably, the thickness of the layer is at least 0.1 mm.

Here, the carcass auxiliary layer 6 can be used by embedding a cloth or a non-woven fabric in rubber.
It is recommended to use a rubber-covered composite of organic fiber cords of ~ 0.3 mm arranged side by side in parallel with each other.
That is, it is advantageous to configure the carcass auxiliary layer 6 with a rubber composite in which organic fiber cords such as nylon, polyester, rayon, and vinylon are arranged in a radially extending arrangement at a number of 50/50 mm. .

The carcass auxiliary layer 6 only needs to have a width sufficient to cover at least the missing portion 5, but for example, as shown in FIG. 2, the carcass auxiliary layer 6 is extended until both ends of the carcass auxiliary layer 6 reach the bead portion. Is also good. Further, in the illustrated example, the carcass auxiliary layer 6 is arranged radially outside the carcass 2 having the cutout 5, but may be installed radially inside.

Further, if the carcass 2 has the missing portion 5 in the crown portion, it is difficult to stabilize the manufacture of the tire, which may affect the uniformity of the manufactured tire. That is, when the green tire is inflated in the mold during vulcanization, the carcass ply is not continuous,
It is difficult to inflate uniformly, and there is a possibility that shape variation occurs particularly on both sides in the tire width direction. In that case,
The uniformity of the tire may worsen. Therefore, until the vulcanization of the tire is completed, it is desirable that the rigidity required at the time of vulcanization be maintained in the missing portion 5 and that the elastic modulus in the missing portion 5 be reduced after vulcanization. Therefore,
The carcass auxiliary layer 6 covering the notch 5 is preferably made of an organic fiber cord that melts at a vulcanization temperature of about 150 to 200 ° C. so that the elastic modulus decreases at the boundary of the vulcanization step. is there.

Next, the belt 3 is composed of at least two belt plies covered with rubber by arranging a plurality of steel cords.
And, preferably, two to three sheets are laminated, and the steel cords are arranged in such a direction that the steel cords intersect each other between the laminated plies and are inclined at an angle of 15 to 30 degrees with respect to the equatorial plane of the tire.
Further, in order to suppress the separation at the ply end of the belt 3, a belt auxiliary layer 7 formed by winding a textile cord in a circumferential direction as shown in the figure may be provided.

Further, FIGS. 1 and 2 show a carcass 2
Has shown the case of one ply, but for example, as shown in FIG. 3, the carcass 2 may be composed of a plurality of plies.

The ply cord of the carcass 2 includes rayon, polyethylene-2,6-naphthalate (PE)
Organic fiber cords such as N), polyethylene naphthalate (PET), polyolefin ketone (POK) and nylon are advantageously suitable, and it is preferred that these organic fiber cords are arranged with 40 to 70 cords / 50 mm.

[0025]

EXAMPLES Example 1 Various structures shown in Table 1 were applied to the tire carcass shown in FIGS. 1 and 2 to produce 205 / 60R15 radial tires for passenger cars. In addition, the belt 3
Is a 40 × 50 steel cord with 1 × 5 structure and 0.25mm diameter
The ply was struck in two mm, and the steel cords were arranged so as to cross each other between the laminated plies and inclined at 20 ° to the tire equatorial plane. Further, the belt reinforcing layer 7 is made of 1260 d / 2 nylon cords 40/50.
It is arranged along the tire equatorial plane with the number of shots of mm.

Further, in the tire shown in FIG. 1, a conventional tire having a continuous carcass without a missing portion was prototyped in the same size.

The uniformity of each of the tires thus obtained was measured, and the tires were subjected to driving stability and riding comfort tests. Table 1 shows the measurement and test results.
It is described together.

Here, the uniformity of the tire is determined by assembling the tire on a standard rim, adjusting the internal pressure to 2.0 kgf / mm, and then applying a load corresponding to the air pressure specified by JATMA to a metal drum having a diameter of 3 m. Pressing the upper side, rotating the drum at a very low speed in this state, the lateral force fluctuation (LE
V) was measured and evaluated. Then, several tens of tires of the same type were prototyped, and the lateral force fluctuation was measured for each. When the tires with lateral force fluctuations of 50 N or more were out of the standard, the ratio of the nonstandard tire to the total tires of the same type (%).

In the steering stability test, each tire was mounted on a standard rim, adjusted to an air pressure corresponding to the maximum added capacity, and then mounted on a passenger car having a displacement of 2500 cc class.
Sensory evaluation was performed on items such as straight running stability, turning stability and handling properties when traveling at a speed of 0 km / h. The evaluation result is indicated by an index using the score of the comparative tire as a reference (0), and the higher the numerical value, the higher the performance.

Further, in the riding comfort test, each tire was mounted on a passenger car, and a sensory test for riding comfort was performed in the same manner as in the steering stability test, and the evaluation was performed in the same manner as in the steering stability test.

[0031]

[Table 1]

Example 2 Various structures shown in Table 2 were applied to the carcass of the tires shown in FIGS. 1 and 2, and prototypes of radial tires for passenger cars having a size of 205 / 60R15 were produced. In addition, the belt 3
The specifications of the belt reinforcing layer 7 are the same as those in the first embodiment.

For comparison, a conventional tire having a continuous carcass without any missing portion in the tire shown in FIG. 1 and a comparative tire having no carcass auxiliary layer in the tire shown in FIG. Prototype made.

The uniformity of each of the tires thus obtained was measured, and the tires were subjected to driving stability and riding comfort tests. Table 2 shows the measurement and test results.
It is described together. The measurement and test methods are the same as in Example 1 described above.

[0035]

[Table 2]

[0036]

According to the present invention, it is possible to improve the ride comfort by providing the carcass with a missing portion and to achieve a reduction in weight while reducing the steering stability due to the missing portion by providing a carcass auxiliary layer. In order to prevent this from happening, the ride comfort is improved without sacrificing excellent steering stability, so that it is possible to deal with the trend toward luxury without losing the basic performance of the car.

[Brief description of the drawings]

FIG. 1 is a diagram showing a tire structure of the present invention.

FIG. 2 is a diagram showing another tire structure of the present invention.

FIG. 3 is a view showing still another tire structure of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 3 Belt 4 Tread 5 Missing part 6 Carcass auxiliary layer 7 Belt reinforcement layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B60C 9/08 B60C 9/08 K 9/22 9/22 D

Claims (6)

[Claims] 1. A pneumatic vehicle for passenger cars in which a carcass comprising a ply of organic fiber cords arranged radially across a pair of bead cores is used as a skeleton, and a crown portion of the carcass is reinforced by a plurality of belts. A pneumatic radial tire for a passenger car, wherein the carcass has a cutout portion in a crown portion thereof, and further has a carcass auxiliary layer provided adjacent to the cutout portion. 2. The pneumatic radial tire for a passenger car according to claim 1, wherein the elastic modulus of the carcass auxiliary layer is lower than the elastic modulus of the carcass. 3. The belt according to claim 1, wherein the length of the carcass missing portion in the tire width direction is 20 to 70 times the maximum width of the belt.
% Pneumatic radial tires for passenger cars. 4. The pneumatic radial tire for a passenger car according to claim 1, wherein the carcass auxiliary layer is formed by covering a plurality of organic fiber cords having a diameter of 0.1 to 0.3 mm with rubber. . 5. The pneumatic radial tire for a passenger car according to claim 4, wherein the melting point of the organic fiber cord is 150 ° C. or less. 6. The method according to claim 1, wherein
Radially outside the belt, at least cover the belt side end,
A pneumatic radial tire for a passenger car, comprising a belt reinforcing layer.