JPH1128916A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the operational stability of a tire and comfortableness damping without worsening road-noise and rolling resistance of the tire as early as possible. SOLUTION: The radial tire is provided with a carcass 1 extending over between a pair of bead cores 2, 2 and bead fillers 3 adjacent to the bead cores 2 and extending along the carcass l beyond tire-maximum width positions 4. In this case, the upper part of the bead filler 3 is formed of a sectionally narrowed width part 5 arranged in state where it is overlapped with the tire- maximum width position 4, and the sectionally narrowed width part 5, in which the upper end part 6 and the lower end part 7 are the same in the section width, is connected to a sectionally thickened width part 8 constituting the lower part of the bead filler 3.

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, in particular, by improving the shape of a bead filler to improve steering stability and ride comfort damping without deteriorating road noise and rolling resistance as much as possible. The present invention relates to a pneumatic radial tire.

[0002]

2. Description of the Related Art Conventionally, as a technique for improving the steering stability and riding comfort of a tire, the sectional height of a bead filler is increased, a side ply is added, and the rigidity and height of a carcass material are increased. And so on. All of these means provide rigidity to the sidewall portion of the tire, thereby exhibiting riding comfort damping, that is, exhibiting stiff elasticity on uneven road surfaces, reducing tire vibration, and further improving steering stability. It is to ensure the nature.

[0003]

However, any of these means has a problem that the natural value of the primary vibration of the tire is increased and the weight is greatly increased, so that the road noise and the rolling resistance of the tire are deteriorated. . Therefore, in the above-described conventional technology, the steering stability of the tire and the riding comfort dumping,
It was difficult to achieve both the road noise and the rolling resistance of the tire.

An object of the present invention is to provide a pneumatic radial tire which can improve the steering stability and riding comfort of a tire without deteriorating road noise and rolling resistance of the tire as much as possible. is there.

[0005]

As a result of intensive studies to solve the above-mentioned problems, it has been found that the above-mentioned problems can be solved by setting the cross-sectional shape of the bead filler to a specific shape and disposing it at a fixed position. Was. That is, the present invention
In a pneumatic radial tire having a carcass extending between a pair of bead cores in a toroidal shape and a bead filler adjacent to the bead core and extending beyond the tire maximum width position along the carcass, an upper part of the bead filler is The cross-sectional narrow portion is disposed so as to overlap with the tire maximum width position, and the cross-sectional narrow portion has substantially the same cross-sectional width at its upper end and lower end,
A pneumatic radial tire which is continuous with a wide cross-sectional portion constituting a lower portion of the bead filler.

The sectional shape of a conventional bead filler is, for example, as shown in FIG.
Has a shape in which the sectional width gradually increases toward the lower part 11b. Therefore, if the height of the bead filler 11 is increased, the rigidity of the sidewall portion 12 is also increased, so that the steering stability and the riding comfort damping are improved, but the increase in the height of the bead filler 11 is increased in weight,
In addition, the primary vibration eigenvalue of the tire increases, which causes road noise. In FIG. 3, 13
Is the tire maximum width position.

According to the present invention, the upper portion of the bead filler is not made to have a cross-sectional shape in which the cross-sectional width gradually increases toward the lower portion of the wide width as in the prior art. By arranging the upper portion of the substantially identical bead filler so as to overlap the tire maximum width position, even if the height of the bead filler increases, the increase in tire weight and the increase in the primary vibration eigenvalue are suppressed. . In the tire of the present invention, the cross-sectional width of the upper portion of the bead filler is made substantially the same, but the upper portion of the bead filler having the substantially same cross-sectional width is arranged so as to overlap the tire maximum position. Thereby, the rigidity of the sidewall portion is secured, and the steering stability and the riding comfort damping are improved.

[0008]

FIG. 1 is a partial sectional view showing one embodiment of a radial tire according to the present invention. FIG. 2 is an enlarged sectional view of a main part in FIG.

In FIG. 1, 1 is a pair of bead cores 2,
A carcass 3 extends in a toroidal shape between the two, and 3 is a bead filler adjacent to the bead core 2 and extending along the carcass 1 beyond the tire maximum width position 4.

As shown in FIGS. 1 and 2, the upper portion of the bead filler 3 is formed of a narrow cross section 5, and is arranged so as to overlap the tire maximum width position 4 at the narrow cross section 5. ing. The narrow cross-sectional portion 5 of the bead filler 3 has a cross-sectional width of each of the upper end 6 and the lower end 7 thereof.
The width W1 and the cross-sectional width W2 are substantially the same, and are configured to be continuous with the wide cross-section 8 forming the lower portion of the bead filler 4. In FIG. 1, 9 is a belt, and 10 is a belt reinforcing layer.

In FIG. 1 and FIG. 2, the ratio A / B of the cross-sectional height B of the bead filler to the height A between the upper end 6 and the lower end 7 of the narrow section 5 is not particularly limited. .
15 to 0.35 is a preferable range. When the ratio of A / B is less than 0.15, the cross-sectional narrow portion 5 does not have a height even if the narrow cross-sectional portion 5 is arranged so as to overlap the tire maximum width position 4. Since the influence of the wide portion 8 relatively increases, the rolling resistance of the tire increases due to the increase in weight, and the road noise also tends to deteriorate. On the other hand, when the ratio of A / B exceeds 0.35, the height of the cross-sectional narrow portion 5 is too large, so that the rigidity of the sidewall portion is reduced, and the steering stability and the riding comfort damping are improved. Tends to be difficult to obtain. In the present invention,
The height A between the upper end and the lower end of the narrow cross section and the cross sectional height B of the bead filler are all measured by mounting the measurement tire on a standard rim specified by JATMA and applying an air pressure of 30 kP.
The values obtained by measuring the tire disassembly shape with the tire shape at time a are shown.

The upper end 6 and the lower end 7 of the narrow section 5
The specific cross-sectional widths W1 and W2 also vary according to the tire size, but are preferably designed to be 0.8 mm to 1.2 mm based on the tires for passenger cars.

In the present invention, the expression that the upper end portion and the lower end portion of the narrow cross-section have substantially the same cross-sectional width means that they have completely the same cross-sectional width and also include a cross-sectional width within an error range. Means that With respect to passenger car tires, the variation within the range of 0.8 to 1.2 mm is defined to be substantially the same.

The upper end 6 and the lower end 7 of the narrow section 5
The height A between the tires also varies according to the tire size. However, in the case of a tire for a passenger car, in order to reduce road noise and prevent deterioration of the rolling resistance of the tire, the height A is 15 mm or more (for example,
15 mm to 20 mm). More specifically, the ratio A / B of the cross-sectional height B of the bead filler to the height A between the upper end and the lower end of the narrow section is 0.15 to 0.15.
The above height A is 15 provided that it is 0.35.
It is preferably at least mm.

The sectional height B of the bead filler can be adopted as long as it is generally used for tires. Specifically, for example, a bead filler having a sectional height B of 30 to 60 mm can be used.

[0016]

EXAMPLE A 185 / 65R14 radial tire having the structure shown in FIG. 1 and having the bead filler shown in Table 1 was trial-produced, and its rolling resistance, road noise, steering stability and riding comfort damping were evaluated.

In Table 1, the tire lateral rigidity and the tire longitudinal rigidity are the force per unit length when a 350 kg load is applied to the tire and the tire is flexed in the lateral and longitudinal directions, respectively.
This is a value obtained by converting Comparative Example 1 as a control 100. The higher the value, the higher the rigidity.

Rolling resistance is standard rim (14 × 6JJ)
, And filled with air pressure of 200 kPa in a hot state, and measured with a drum type rolling resistance tester (the ambient temperature is 2
4 ± 1 ° C.), and Comparative Example 1 was represented as an index by taking 100 as an index.
The larger the value, the lower the rolling resistance.

The road noise was evaluated by mounting a tire on a 2000 cc domestic vehicle, driving at an air pressure of 200 kPa, and riding on a rough surface (road noise evaluation road) with two passengers, at a microphone position in the center of the front seat. The speed of the test vehicle is 60 km / h. The road noises in Table 1 are evaluated on the basis of the tires of Comparative Example 1 and are equal to the standards if they are equivalent to Comparative Example 1. If there is a difference from Comparative Example 1, the road noise is indicated by the road noise difference. I have. The higher the plus value of the road noise difference, the higher the road noise.

The steering stability was evaluated by operability during driving on asphalt pavement road surface by two panelists based on a five-point sensitivity evaluation. The larger the value, the better the steering stability.

The ride comfort dumping was evaluated by the sensitivity evaluation of a five-point scale, as well as the steering stability, in terms of the ride comfort damping performance when driving on asphalt paved road surface by two panelists. The higher the value, the better.

[0022]

[Table 1]

From Table 1, it can be seen that the example tires have improved handling stability and ride comfort damping while minimizing road noise and deterioration of rolling resistance as compared with the comparative example tires. In particular, the ratio A / B of the bead filler cross-sectional height B to the height A between the upper end and lower end of the narrow cross-section portion
Is a preferable range of 0.15 to 0.35. Tires in the same range have no road noise and no deterioration in rolling resistance as compared with the tire of Comparative Example 1, and have improved steering stability and ride comfort damping. The above A / B ratio is 0.1
In the case of less than 5, even if the narrow cross section is arranged so as to overlap the tire maximum width position, there is no height of the narrow cross section, so the influence of the wide cross section is relatively increased. It is recognized that the rolling resistance of the tire increases due to the weight increase, and the road noise also tends to deteriorate. On the other hand, when the ratio of A / B is more than 0.35, the rigidity of the sidewall portion is reduced because the height of the narrow cross section is too high, and it is difficult to improve the steering stability and the riding comfort dumping. There is a tendency. Further, in a tire in which the height A between the upper end and the lower end of the narrow section is less than 15 mm, the rolling resistance of the tire tends to increase and the road noise tends to deteriorate. Further, with a tire in which the cross-sectional width of each of the upper end portion and the lower end portion of the narrow cross-section portion is less than 0.8 mm, the steering stability and the riding comfort damping are not significantly improved. For tires with a cross-sectional width of more than 1.2 mm at the upper and lower ends of the narrow cross-section, the longitudinal stability and ride comfort damping are improved, but the rolling resistance of the tire is increased and road noise is also worsened. Is observed.

[0024]

As described above, the present invention includes a carcass extending in a toroidal manner across a pair of bead cores, and a bead filler adjacent to the bead core and extending along the carcass beyond the tire maximum width position. In the pneumatic radial tire, the upper portion of the bead filler is configured with a cross-sectional narrow portion arranged so as to overlap with the tire maximum width position, and the cross-sectional narrow portion is a cross section of each of an upper end portion and a lower end portion. Since it is a pneumatic radial tire having substantially the same width and continuing to the wide section in the lower part of the bead filler, the steering stability is reduced as much as possible to reduce road noise and rolling resistance. And riding comfort can be improved.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing one embodiment of a radial tire according to the present invention.

FIG. 2 is an enlarged sectional view of a main part in FIG.

FIG. 3 is a partial cross-sectional view showing an example of a radial tire on which a conventional bead filler is arranged.

[Explanation of symbols]

 Reference Signs List 1 carcass 2 bead core 3 bead filler 4 tire maximum width position 5 narrow cross section 6 upper end 7 lower end 8 wide cross section A height between upper end and lower end of narrow cross section B cross sectional height of bead filler Sa

Claims (4)

[Claims] 1. A pneumatic radial tire comprising: a carcass extending in a toroidal manner across a pair of bead cores; and a bead filler adjacent to the bead core and extending along a carcass beyond a tire maximum width position. The upper portion of the bead filler is formed of a narrow cross-sectional portion arranged so as to overlap the tire maximum width position, and the cross-sectional narrow portion has substantially the same cross-sectional width at its upper end and lower end. A pneumatic radial tire that is continuous with a wide-width section in the lower part of the bead filler. 2. The ratio A / B of the cross-sectional height B of the bead filler to the cross-sectional height A between the upper end and the lower end of the narrow section.
The pneumatic radial tire according to claim 1, wherein is 0.15 to 0.35. 3. The pneumatic radial tire according to claim 2, wherein a height A between an upper end and a lower end of the narrow section is 15 mm or more. 4. The pneumatic radial tire according to claim 1, wherein each of an upper end portion and a lower end portion of the narrow section has a sectional width of 0.8 mm to 1.2 mm.