JP2000255211A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire which is considerably improved in comfortableness against vibration in addition to retaining control stability at a high level. SOLUTION: This pneumatic radial tire comprises a pair of bead parts 1, a pair of side wall parts 2, and a tread part 3 troidally extending between both side wall parts 2, and is provided with a radial carcass 5 which reinforces each of these part over between a pair of bead cores buried in the bead parts 1, a belt 6 which strengthened the tread part 3 around an outer circumference of a crown part of a carcass layer. A carcass has a folding part which is folded from the inside to the outside of the tire around each bead core. The tire also provided with a bead filler rubber 7 taperingly extending from the bead core toward the tread part 3 between the folding part and the carcass. The tire is placed an integral composite member 8 composed of plain cloth and rubber where fibers made of a steel are crossingly arranged each other to be reticulate shape at the side wall part.

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, and more particularly to a vibration riding comfort (hereinafter abbreviated as a ride) and a steering stability (hereinafter abbreviated as a drivability).
And pneumatic radial tires that simultaneously achieve excellent levels.

[0002]

2. Description of the Related Art The demand for higher performance of radial tires for passenger cars has been increasing more and more. For example, as one effective means for realizing a high degree of controllability, the tire flatness ｛(tire Height / width of tire) × 100 °.

[0003] When the flattening rate is reduced, excellent maneuverability can be easily realized, but on the other hand, it is inevitable that the swinging performance tends to decrease, and in order to improve this disadvantage, a bead core is required. 2. Description of the Related Art Techniques for reducing the volume of a bead filler rubber disposed outside in the tire radial direction or replacing the rubber with a softer rubber have been widely adopted.

[0004]

However, any of the above-mentioned methods is necessarily regarded as the most important as a high performance tire because the rigidity between the bead portion and the portion of the sidewall portion near the bead portion is reduced. This leads to a decrease in maneuverability. As a result, it is necessary to determine the level of the tremor in consideration of the degree of decrease in maneuverability. As a result, none of the performances is improved to a satisfactory degree.

[0005] Accordingly, an object of the present invention is to provide a pneumatic radial tire in which the rideability is greatly improved while maintaining a high level of controllability.

[0006]

That is, the pneumatic radial tire of the present invention comprises a pair of beads, a pair of sidewalls, and a tread portion extending between the sidewalls in a toroidal shape. A carcass layer provided with a radial arcus which reinforces each of these portions over a space between a pair of bead cores embedded in the bead portion, and a belt which strengthens a tread portion around the crown portion of the carcass layer. A bead filler rubber extending in a tapered shape from the bead core toward the tread portion between the folded portion and the carcass, and the steel fibers are cross-arranged to form a mesh shape. An integral composite member of a plain woven fabric and rubber is disposed on the sidewall portion. Preferably, the steel fibers are monofilaments.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to FIGS. 1 and 2, 1 is a bead portion, 2 is a sidewall portion, 3 is a tread portion, and the radial carcass 5 is a bead portion 1 extending between a pair of bead cores 4 embedded in the bead portion 1. , The sidewall portion 2 and the tread portion 3 are reinforced. The radial carcass 5 in the illustrated example has one ply, but two or more plies are allowed. Further, it is customary to use a radially arranged organic fiber cord, for example, a rubberized ply of a polyester cord.

A belt 6 is disposed around the outer periphery of a radial carcass (hereinafter simply referred to as a carcass) 5 to reinforce the crown portion. The belt 6 has at least two steel cord cross layers.

The carcass 5 has a folded portion 5a which is turned around the bead core 4 from the inside to the outside of the tire. In other words, between the carcass 5 which may be called a carcass body and the folded portion 5a, the bead core 4 is provided. A bead filler rubber 7 extending in a tapered shape is provided from the outer periphery toward the tread portion 3. The bead filler rubber 7 is preferably a hard rubber as much as possible, and its hardness is preferably 70 ° or more (in the range of 70 ° to 100 °) in JIS-A hardness.

FIG. 1 and FIG. 2 are diagrams schematically showing a left half section from a tire equatorial plane E according to an embodiment of the present invention. In the drawing, a member indicated by a broken line and denoted by reference numeral 8 is an integrated composite member of a plain woven fabric and rubber in which steel fibers are cross-arranged to form a mesh shape. In the example shown in FIG.
Are disposed along the outer surface of the bead filler rubber 7, and in the example shown in FIG. 2, the composite member 8 is disposed outside the turn-back portion 5 a of the carcass 5. Here, the above outside and inside refer to the outside and inside of the tire.

Further, FIGS. 3 (A), (B), (C),
(D) shows various examples of the cross section of the main part.

Here, the plain woven fabric of steel monofilament refers to a fabric in which steel fibers are cross-arranged to form a mesh, and the diameter of the filament applied to the plain woven fabric, the material of the steel filament, The fineness of the plain woven cloth (distance between filaments) is appropriately selected according to the application. For example, when used for a tire for a passenger car, the diameter of the filament is 0.1 to 0.3 mm.
Hard steel wire with a distance between filaments of 0.5 to 0.8 m
Those arranged in m are preferred. Further, in order to enhance the adhesiveness with the matrix rubber, those having a plated surface are preferable.

In order to make the steel plain woven fabric described above into the composite member 8, the unvulcanized rubber composition is applied to the steel plain woven fabric in advance to form a composite. This compounding is performed, for example, by pressing a sheet-like unvulcanized rubber composition from both upper and lower surfaces of a plain steel woven fabric with a press or a roll, etc., and blowing the air inside the steel plain woven fabric with the unvulcanized rubber. It is performed by sufficiently replacing the composition. A green tire is formed by applying the unvulcanized composite member thus obtained.

Regarding the physical properties of the rubber composition used for the composite member 8, the tensile stress at 50% elongation is preferably in the range of 1 to 9 MPa, and the hardness is preferably 60 ° or more in JIS-A hardness.

Also, the height H ₀ of the tapered end of the bead filler rubber 7 measured from the bead base line BL and the maximum height H ₁ of the composite member 8 measured in the same manner are compared with the tire section height SH measured in the same manner. , H ₀ = (0.25 to 0.6) × SH H ₁ = (0.33 to 0.6) × SH. Reference numeral H ₂ shown in FIG. 2 is a tire inner end height of the composite member 8.

In the conventional means for reducing the cross-sectional area of the bead filler rubber or for making the rubber softer, the longitudinal spring constant (longitudinal stiffness) of the tire is reduced to improve the oscillating property. It has been said that the lateral spring constant (lateral stiffness) is also reduced, resulting in deterioration of the steerability.

Therefore, the correlation between the maneuverability and the tire rigidity was investigated in further detail. As a result, the torsional rigidity (torsion spring) around the axis perpendicular to the rotation axis of the tire on the tire equatorial plane E was determined. Constant) has a greater effect than lateral stiffness. Inspection of the above means in this regard revealed that the torsional stiffness was also greatly reduced, and this was the main cause of the decrease in steerability.

On the other hand, by disposing an integral composite member 8 of a steel plain woven fabric and rubber having a cross-type multidirectional arrangement of fibers outside the bead filler rubber 7, the volume or cutoff of the bead filler rubber 7 is improved. Even if the area is greatly reduced,
Compared with a tire exhibiting excellent maneuverability before the volume or cross-sectional area of the rubber 7 is reduced, it is possible to maintain not only the lateral rigidity but also the torsional rigidity equivalently.

Regarding the longitudinal rigidity, which has a great influence on the oscillating property, by arranging the composite member 8 along the outer surface of the bead filler rubber 7, the outer side of the bead filler rubber 7 under the load of the tire is reduced. Since the fibers are in the compression area, the fibers hardly exhibit rigidity.Furthermore, the fibers themselves exhibit a smaller compression rigidity than cords and use a steel plain woven fabric, so the rate of bearing the compression load is also large. As a result, the effect of suppressing the improvement in rigidity can be advantageously obtained, so that the improvement in longitudinal rigidity can be advantageously avoided. Even when the composite member 8 is disposed along the outer surface of the carcass 5 as in the case of the composite member 8, it is also possible to advantageously avoid the improvement in the vertical rigidity under the load as described above.

As described above, by arranging the composite member 8, even if the volume of the bead filler rubber 7 is reduced, the same high level of controllability as a tire that does not modify the bead filler rubber can be obtained. It is possible to maintain and significantly improve the riding performance of this tire.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic radial tire for passenger cars of size 205 / 65R15, in which the carcass 5 has a one-ply configuration in which a polyester cord is radially arranged, and a composite member 8 is disposed inside the folded portion of the carcass. . The belt 6 comprises two steel cord cross layers and one 6,6-nylon cap layer disposed around the outer periphery of the steel cord cross layer.
Bead filler rubber 7 has a 50% modulus of 8.0M.
Pa (95 ° in JISA hardness), and the cross-sectional area is 1.
1 cm ² , height H ₀ is 40 mm (0.33 × SH).

In common with the above, the diameters (mm) and the distances (mm) of the filaments of the steel plain woven fabric of the composite member 8 and the arrangement position of the composite member 8 were changed in Examples 1 to 5. The tire was prepared. In the arrangement position A, H ₂ is adjusted to the outer peripheral position of the bead core 4 (the inner peripheral position of the bead filler rubber 7), H ₁ = 0.5SH, and the arrangement position B is H ₁ = 0.5SH, H ₂ = 0. .2SH, position C was H ₁ = 0.6SH, and H ₂ = 0.35SH. In addition, in all tires, the composite member has a steel filament inside that is 45 ° with the carcass ply cord.
It was arranged so that it might intersect.

The unvulcanized rubber composition integrated with the plain steel woven fabric has a 50% modulus after vulcanization of 5.0 MPa.
In a, a rubber having a JIS A hardness of 75 ° was applied, and this rubber sheet was pressed between both rolls on both surfaces of a steel plain woven fabric.

In order to verify the effects of Examples 1 to 5, a conventional tire in which the volume of the bead filler rubber was 135% of that of the Example was prepared without disposing the composite member 8 from each Example. The maneuverability and the shaking performance were compared and evaluated according to the test conditions and evaluation method described.

That is, the test vehicle has a domestically produced 2000 cc
Using a front-wheel-drive vehicle, filling the maximum internal pressure determined by JATMA, and driving on a test course at a speed of 80 to 120 km / h
h, straight running, lane change running, and circular turning running are repeated, and the riding performance is good at 40 to 80 km / h on good roads, seam roads, and bad roads. The points are scored as a perfect score, and the scores are shown in Table 1 as numerical values. A score of 8 (points) or higher is a pass level.

[0026]

[Table 1]

As is clear from Table 1, while the tire of the conventional example is excellent in steerability, the shaking property is insufficient, while the tire of the comparative example has improved shaking property to a satisfactory degree. On the other hand, the maneuverability is significantly reduced, and it can be expected that this maneuverability level is dangerous. On the other hand, it has been proved that all of the tires of Examples 1 to 12 can exhibit a sufficient level of maneuverability and shaking performance at an acceptable level, and the tires of Examples having a slight difference between the two performances Has the advantage that it can be used properly according to the purpose.

[0028]

According to the present invention, it is possible to provide a pneumatic radial tire for a passenger car, in which the steering performance is remarkably improved while maintaining excellent steering performance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a left half of a cross section of a tire according to the present invention cut along an equatorial plane.

FIG. 2 is a diagram showing a left half of a cross section of the tire according to the present invention, cut along an equatorial plane.

FIG. 3 is a diagram showing a main part of a tire according to the present invention.

[Explanation of symbols]

 1: bead portion 2: side wall portion 3: tread portion 4: bead core 5: carcass 5a: carcass folded portion 6: belt portion 7: bead filler 8: composite member 10: pneumatic radial tire

Claims (2)

[Claims] 1. A pair of bead portions, a pair of sidewall portions, and a tread portion extending in a toroidal shape between both sidewall portions, and each of these portions extends between a pair of bead cores embedded in the bead portion. A radial arcus to be reinforced; and a belt around the outer periphery of the crown portion of the carcass layer for reinforcing the tread portion. The carcass has a folded portion that is folded around each bead core from inside to outside. In a pneumatic radial tire having a bead filler rubber extending in a tapered shape from a bead core to a tread portion, steel fibers are cross-arranged, and an integral composite member of a plain woven fabric and rubber in a mesh form Is arranged on a sidewall portion of the pneumatic radial tire. 2. The pneumatic radial tire according to claim 1, wherein the steel fiber is a monofilament.