JP2003291612A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve uniformity. <P>SOLUTION: In this pneumatic tire 1 provided with a bead core 5 in a bead section 4, the bead core 5 comprises a winder around which steel wires 10 are turned, and an organic fiber code 12 arranged in a gap section 11 to be formed between the steel wires 10 and 10. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pneumatic tire having an improved bead core.

[0002]

2. Description of the Related Art As schematically shown in FIG. 6, an annular bead core c is embedded in a bead portion b of a pneumatic tire. The general bead core c is formed by winding a single steel wire e in multiple stages and multiple rows (so-called single wind), or a tape-shaped body obtained by aligning a plurality of steel wires in parallel a plurality of times. Many are spirally wound (so-called tape beads). The bead core c maintains the bead diameter and firmly seats the bead portion b on the rim r. Further, the end portion of the carcass ply d that forms the skeleton of the tire is folded back and locked to the bead core c.

By the way, in the raw cover molding process,
As shown in FIG. 7, the bead core c has a carcass ply d.
It is sandwiched between the main body portion d1 and the folded portion d2 and receives a force in the compression direction. However, as shown in FIG. 8, in the vulcanization step, since the raw cover is pressed from the tire cavity side with, for example, a bladder, the carcass ply body portion d1 is indicated by the arrow A.
The tensile force in the direction of arrow B and the tensile force in the direction of arrow B acts on the folded portion d2 accordingly. Then, during the vulcanization molding, a slight sliding movement of the carcass ply d occurs due to this tensile force, and a force for rotating the bead core c around the center of its cross section acts along with the sliding movement.

Due to such a rotating force, the bead core c
The bead wire e wound on the
The “deformation” in which the cross-sectional shape of the bead core c changes is likely to occur. Further, the shape deformation of the bead core c causes the carcass cord path to be non-uniform in the tire circumferential direction, which further deteriorates the uniformity of the tire.

The present invention has been devised in view of the above problems, and is based on the provision of an organic fiber cord in the gap formed between the steel wires forming the bead core. It is an object of the present invention to provide a pneumatic tire in which the shape of the bead core is unlikely to be deformed even when it is molded, and by which the uniformity is excellent.

[0006]

The invention according to claim 1 of the present invention is a pneumatic tire in which a bead core is arranged in a bead portion, and the bead core comprises a wound body around which a steel wire is wound. At the same time, an organic fiber cord is arranged in a gap formed between the steel wires.

The diameter of the steel wire is, for example, 0.
Those having a diameter of 5 to 2.0 mm are preferable. As the organic fiber cord, for example, polyester cord, nylon cord or aramid cord can be preferably used. Further, the diameter of the organic fiber cord is preferably 0.2 to 0.8 times the diameter of the steel wire.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a tire meridian sectional view including a tire shaft of the pneumatic tire of the present embodiment.
In the figure, a pneumatic tire 1 of the present embodiment has a toroidal carcass 6 extending from a tread portion 2 to a bead core 5 of a bead portion 4 through a sidewall portion 3, and a carcass 6 on the outer side in the tire radial direction and on the tread portion 2. 1 illustrates a radial tire for a passenger vehicle, which includes a belt layer 7 that is disposed inside and that fastens the carcass 6 by tightening.

The carcass 6 has at least one radial structure in which carcass cords are arranged at an angle of, for example, 75 ° to 90 ° with respect to the tire equator C.
It is composed of one carcass ply 6A. As the carcass cord, a polyester cord is used in this example, but other than this, an organic fiber cord such as nylon, rayon, or aramid, or a steel cord if necessary can be used.

The carcass ply 6A includes a main body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4 and a tire axial direction extending from the main body portion 6a around the bead core 5 in the tire axial direction. It has integrally with the folding | returning part 6b by which the folding | returning from the inner side to the outer side was carried out and locked. The carcass ply 6A has a body portion 6a and a folded portion 6
A bead apex 8 extending from the bead core 5 to the outer side in the radial direction of the tire and made of hard rubber is arranged between the b and b to reinforce the bending rigidity of the bead portion 4.

The belt layer 7 has at least two belt cords arranged at a small angle of, for example, 10 to 45 ° with respect to the tire equator.
The belt plies 7A and 7B are superposed in a direction in which the cords cross each other. In this example, a belt layer 9 in which organic fiber cords are arranged substantially along the tire circumferential direction is provided outside the belt layer 7.

FIG. 2 shows an enlarged sectional view of the bead core 5. The bead core 5 of this example is exemplified by a so-called single-winding wound body in which a single wire steel wire 10 having a substantially circular cross section is wound in multiple stages and multiple rows.
In the case of the radial tire for passenger cars of the present embodiment, the diameter D1 of the steel wire 10 is preferably about 0.5 to 2.0 mm, more preferably about 0.8 to 1.6 mm. When the diameter D1 of the steel wire is less than 0.5 mm, it is necessary to increase the number of driving in order to maintain the rim detachment performance when a lateral force is applied, and there is a tendency that winding work takes time, Conversely, if it exceeds 2.0 mm,
The winding workability is deteriorated and the fitting pressure with the rim tends to be excessively high, which is not preferable.

The bead core 5 has an unvulcanized rubber attached to the outer surface of the steel wire 10 with a small thickness of, for example, about 0.3 mm. This can improve the adhesiveness between the steel wires 10 adjacent to each other during winding. In this example, such a steel wire 10 is wound in four rows in the tire axial direction and three steps in the tire radial direction (so-called 4 + 4).
+4 configuration), the cross-section is formed into a substantially oblong rectangular shape. When winding the steel wire 10, one steel wire 1 is used as in this example.
In addition to a single wind in which 0s are continuously wound in multiple stages and multiple rows, a tape bead method in which a wire bundle in which a plurality of steel wires 10 are arranged in the width direction and bundled in a tape shape is spirally wound is formed. Well, the form is not particularly limited.

One feature of the pneumatic tire 1 of the present invention is that an organic fiber cord 12 is arranged in a gap 11 formed between the steel wires 10 and 10 of the bead core 5.

In the conventional bead core, the steel wire 1
Air and rubber attached to the outer peripheral surface of the steel wire 10 are present in the gap 11 formed between 0 and 10. However, during the vulcanization molding, the rubber is in a fluidized state due to the vulcanization heat, so that the movement of the steel wire 10 cannot be effectively restricted when an external force acts on the bead core.

On the other hand, when the organic fiber cord 12 is interposed in the gap portion 11 as in the present invention, the steel wires 10 and 1 adjacent to the organic fiber cord 12 are provided.
By making contact with 0, the shape of the gap 11 can be maintained and the amount of movement of the steel wire 10 can be restricted to an extremely small amount. Therefore, during vulcanization molding, the carcass ply 6
Even if a tensile force is applied to the bead core 5, it is possible to substantially prevent the bead core 5 from losing its shape, and it is possible to prevent the carcass cord path length between the bead cores 5 and 5 from becoming uneven in the tire circumferential direction. Therefore, the pneumatic tire 1 having excellent uniformity can be provided. Further, the organic fiber cord 12 serves as an appropriate cushioning material against compressive strain, torsional strain, etc. that acts on the bead core 5 during traveling,
It is possible to improve steering stability without deteriorating riding comfort and rim assembly. In particular, the rigidity during turning is increased, and the initial responsiveness during steering is improved.

Such a bead core 5 is shown in FIG.
As shown in (A), a steel wire 10 is wound around the outer peripheral surface of a bead core forming drum R having flanges on both sides to first form a steel wire layer W1 of the first stage, and thereafter, the steel wire layer W1 is formed. The winding of 10 is once stopped, and the organic fiber cord 12 is wound around the outside of the steel wire layer W1. The organic fiber cord 12 is wound along the recess between the adjacent steel wires 10 and 10. That is, the winding pitch P2 of the organic fiber cord 12 is substantially equal to the winding pitch P1 of the steel wire 10 and is displaced in the width direction by the half pitch.

When the organic fiber cord 12 has been wound between the steel wires 10 and 10, the steel wire 10 is wound again on the outside thereof as shown in FIG. 3 (B). As a result, the second-stage steel wire layer W2 can be formed. By forming the second-stage steel wire layer W2, the organic fiber cord 12 can be interposed in the substantially closed gap portion 11 between the steel wires 10 and 10. Then, after forming the second steel wire layer W2, the winding of the steel wire 10 is once again stopped, and the organic fiber cord 12 is wound on the outer side of the second steel wire layer W2 in the same procedure as described above. Turn. By sequentially repeating such steps, as shown in FIG. 3C, the bead core 5 can be formed by interposing the organic fiber cord 12 in the gap portion 11 between the steel wires 10 and 10. The organic fiber cord 12 may be continuous, or may be interrupted at the gap 11 between the first and second stages and the gap 11 between the second and third stages. But good.

The organic fiber cord 12 can be wound in a natural state in which an external force is not substantially applied, but it is also preferably wound in a tensioned state or a loosened state. . When the organic fiber cord 12 is wound by being applied with tension, the organic fiber cord 12 is more closely adhered to the steel wires 10 and 10 and the positional deviation from the gap portion 11 is less likely to occur, and the wound state is even in the tire after vulcanization. Its stability makes it particularly desirable for uniformity. In this case, more specifically, it is more effective to wind the organic fiber cord 12 in a state where elastic elongation of about 2 to 3% is applied.
When applying tension to the organic fiber cord 12, it is preferable that the winding start end is fixed to the steel wire 10 and the winding speed is controlled by the rotation speed of the drum. Further, it is preferable to fix the winding end to the steel wire 10 as well as the winding start end.

On the contrary to the above, the organic fiber cord 12 can be wound with a slack that is about 2 to 3% of the actual winding length. For example, many organic fiber cords such as nylon cords and polyester cords 12
Since it has heat-shrinkability, it is also preferable to shrink the organic fiber cord 12 by vulcanization heat and arrange it in the gap portion 11 with an optimum winding length after vulcanization molding.

As another method of forming the bead core 5,
For example, as shown in FIG. 4, a plurality of steel wires 10 are preliminarily arranged in parallel in the width direction of the bead core to form an integrated wire bundle, and a concave portion between the steel wires 10 and 10 adjacent to one surface thereof is formed. Alternatively, the bead core 5 can be formed by using the tape-shaped body T in which the organic fiber cords 12 are adhered and integrated. In this case, the tape bead can be formed by continuously winding the tape-shaped body T in a spiral shape, and the same bead core as shown in FIG. 2 can be easily manufactured. In this embodiment, the organic fiber cord 12 appears on the outermost peripheral surface or the innermost peripheral surface of the bead core 5, but it can be appropriately cut off if it is unnecessary.

The organic fiber cord 12 is not particularly limited, but for example, polyester cord, nylon cord or aramid cord can be preferably used. The diameter D2 (shown in FIG. 2) of the organic fiber cord 12 is preferably about 0.2 to 0.8 times the diameter D1 of the steel wire 10, for example. When the diameter D2 of the organic fiber cord 12 is less than 0.2 times the diameter D1 of the steel wire 10, a large number are required to suppress the movement of the steel wire 10, which tends to reduce the productivity. 0.
If it exceeds 8 times, the dense winding of the steel wire 10 tends to be obstructed.

In particular, in the case of the bead core 5 in which the steel wire 10, 10 overlapping in the tire radial direction is wound with the cross-sectional center positions thereof substantially aligned as in this embodiment, the gap 11 is relatively large. . Therefore, in the case of such a bead core 5, more preferably, the diameter D2 of the organic fiber cord 12 is changed to the diameter D1 of the steel wire 10.
It is desirable to set 0.3 to 0.8 times, more preferably 0.4 to 0.6 times. Particularly preferably, the fineness of the organic fiber cord 12 is 700 to 1800 dtex / 2 (or 1).
400-2200 dtex / 1), more preferably 800-
1400dtex / 2 (or 1600-2000dtex / 1)
It is desirable to set the degree.

On the other hand, as shown in FIG. 5, in the case of the bead core 5 in which the center position of the cross section of the steel wire 10 overlapping in the tire radial direction is displaced in the tire axial direction by the radius of the steel wire 10 and wound. The gap portion 11 becomes relatively small. Therefore, in the case of such a bead core 5, the diameter D2 of the organic fiber cord 12 is 0.2 to 0.6 times, more preferably about 0.25 to 0.4 times the diameter D1 of the steel wire 10. It is desirable to do. Particularly preferably, the fineness of the organic fiber cord 12 is 500.
~ 1200dtex / 2 (or 800 ~ 1800dtex /
1), more preferably 600 to 800 dtex / 2 (or 9)
It is desirable to set it to about 00 to 1200 dtex / 1).

The number of the organic fiber cords 12 arranged in one gap portion 11 is preferably one as in this example, but when the diameter D2 of the organic fiber cords is small, two or more cords should be arranged. You can also At this time, two or more pieces may be twisted together, or may be simply aligned in parallel and bundled.

Although one embodiment of the present invention has been described in detail above, for example, the bead core 3 can be formed in various shapes such as a circular shape and a polygonal shape other than the rectangular cross section. Also, in this example, the organic fiber cords 12 are provided in substantially all the gaps 11.
However, the organic fiber cords 12 may be provided only in some of the gaps 11. In this case, it is desirable to arrange the organic fiber cords 12 in the gaps 11 of 80% or more in any cross section.

[0027]

[Example] A pneumatic tire for passenger cars having a tire size of 195 / 65R15 was prototyped according to the specifications shown in Table 1, and the difference between the maximum and the minimum of the uniformity, the fitting pressure with the rim, and the carcass cord path length was examined. It was In Conventional Examples 1 and 2, no organic fiber was arranged in the gap between the steel wires of the bead core. The test method was as follows.

<Uniformity> Using a tire uniformity tester, a radial runout (RRO), which is a radial runout of a rotating tire, a radial force variation (RFV), which is a vertical load fluctuation force appearing on a tire rotation axis, and The tangential force variation (TFV), which is the exciting force in the front-rear direction, was measured. The measurement condition is that the rotation speed is 60 for RRO.
rpm, internal pressure 200 kPa, vertical load 4.1 kN, R
For FV and TFV, speed 120km / h, internal pressure 20
The load was 0 kPa and the vertical load was 2.94 kN. The measurement was performed for each of eight tires, and the average value is displayed. The smaller the number, the better the uniformity.
The rim size used is an aluminum rim of 15 × 6JJ.

<Fitting pressure with rim> The fitting pressure between the bead seat surface and the rim seat surface when each test tire was assembled on the rim and filled with an internal pressure of 200 kPa was measured by a Hoffman tester. The measurement was carried out for two tires and the average value was shown.

<Steering stability> The test tire is 15 × 6JJ
The aluminum rim was assembled to the rim, the internal pressure was filled to 200 kPa, and the engine was mounted on all wheels of a domestic FR car with a displacement of 2000 cm ³ , and a sensory evaluation was conducted by driving one driver on the test course. The evaluation was performed by a 10-point method with the conventional example 1 being 7 with a focus on response and responsiveness. The larger the value, the better.

<Difference in carcass cord path length> The test tire was disassembled, and the carcass cord path length across the bead cores was measured at 10 points on the tire circumference. Was measured. The measurement was performed for each of two tires, and the average value is displayed. The smaller the value, the higher the uniformity and the better. Table 1 shows the test results
Shown in.

[0032]

[Table 1]

As a result of the test, it can be confirmed that the embodiment has improved uniformity as compared with the conventional example. Also, it can be confirmed that the riding comfort and road noise performance are improved while maintaining the steering stability as compared with the conventional example.

[0034]

As described above, according to the first aspect of the invention, the bead core is made of a wound body of steel wire and the organic fiber cord is arranged in the gap formed between the steel wires. Therefore, it is possible to prevent the steel wire from being displaced, and to effectively suppress the deformation of the bead core that tends to occur during vulcanization molding. This can provide a pneumatic tire with excellent uniformity. Also, as a result of the organic fiber cords being able to absorb the compressive strain, the torsional strain, etc. that act on the bead core during traveling, the steering stability,
In particular, it is possible to improve the feeling of rigidity and the initial responsiveness during steering.

In the bead core having a steel wire with a diameter of about 0.5 to 2.0 mm as in the second aspect of the present invention, the mold is likely to lose its shape. By applying the present invention to such a tire, It will be even more effective.

When the organic fiber cord is a polyester cord, a nylon cord or an aramid cord as in the third aspect of the invention, the weight can be reduced.

Further, when the diameter of the organic fiber cord is 0.2 to 0.8 times the diameter of the steel wire as in the invention of claim 4, the gap portion of the steel wire is more efficiently filled. Further, it is possible to further prevent the shape loss.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a passenger car radial tire showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the bead core.

3 (A) to (C) are cross-sectional views showing an example of a method for manufacturing a bead core.

FIG. 4 is a perspective view illustrating a tape-shaped body for forming a bead core.

FIG. 5 is a cross-sectional view showing another example of a bead core.

FIG. 6 is a cross-sectional view of a bead portion of a conventional tire.

FIG. 7 is a sectional view of a raw cover.

FIG. 8 is a cross-sectional view of the tire during the vulcanization process.

FIG. 9 is a cross-sectional view of a bead core of Conventional Example 1.

FIG. 10 is a sectional view of a bead core of Conventional Example 2.

FIG. 11 is a cross-sectional view showing the structure of the bead cores of Examples 2-5.

[Explanation of symbols]

2 tread section 3 Side wall part 4 bead part 5 bead core 6 carcass 6A carcass ply 7 Belt layer 10 steel wire 11 Gap 12 organic fiber cord T tape

Claims (4)

[Claims] 1. A pneumatic tire in which a bead core is arranged in a bead portion, wherein the bead core comprises a wound body in which a steel wire is wound, and an organic fiber cord is provided in a gap portion formed between the steel wires. A pneumatic tire characterized by being arranged. 2. The steel wire has a diameter of 0.5-2.
The pneumatic tire according to claim 1, which has a diameter of 0 mm. 3. The pneumatic tire according to claim 1, wherein the organic fiber cord is a polyester cord, a nylon cord or an aramid cord. 4. The pneumatic tire according to claim 1, wherein the diameter of the organic fiber cord is 0.2 to 0.8 times the diameter of the steel wire.