JP2002067628A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an early breakage of a carcass ply cord and to improve the endurance of a bead. SOLUTION: Around a bead core 2 provided at the tire bead 1, the bead core 2 having a hexagon cross section, the side part of a carcass ply 3 is wound up, while the tip 3b of the wounded-up part 3a is arranged near the bead core 2, wherein a rubber 4, allowed to intervene between the outer circumference 2a of the bead core 2 and a top part 3c of the wounded-up part of the carcass ply 3, has the maximum thickness ranging from 0.5 to 8.0 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic tire,
Above all, a flat pneumatic tire for heavy load has improved bead portion durability in particular.

[0002]

2. Description of the Related Art For example, in a heavy-duty tire used for a truck, a bus, or the like, a side portion of a carcass ply is radially moved around a bead core having a hexagonal cross section disposed at a bead portion. In order to solve the problem of economy and resource saving caused by winding up to the side and the problem of durability of the bead portion caused by reducing the winding height, the side portion of the carcass ply is used. Japanese Patent Application Laid-Open No. H11-32244 discloses a technique in which a portion is wound substantially one round around a bead core, and a side portion thereof is terminated around the bead core.

[0003]

However, in this disclosed technique, there is no specific description as to how the side portion of the carcass ply occupies the outer peripheral surface of the bead core. However, with this disclosed technique, it was not possible to impart sufficient durability to the bead portion, and the carcass ply cord itself sometimes broke early.

The present invention has been made in view of such problems, and sufficiently prevents early breakage of a carcass ply cord due to fretting and the like, and greatly improves bead portion durability. It is an object of the present invention to provide a pneumatic tire.

[0005]

A pneumatic tire having a radial structure according to the present invention has at least one bead around a bead core disposed in a tire bead portion and having a polygonal cross section, often a quadrangle to a hexagon. The side portion of the carcass ply is wound from the inside in the tire width direction to the outside or in the opposite direction, and the tip of the winding portion is located near the bead core, The maximum thickness of the rubber interposed between the outer peripheral surface of the bead core, more precisely, the outer peripheral surface of the tire under the rim assembly posture, and the winding portion of the carcass ply is set to a range of 0.5 to 8.0 mm. More preferably, the maximum thickness is 1.0
It is set to a range of up to 5.0 mm.

In this tire, in particular, by setting the maximum thickness of the rubber interposed between the outer peripheral surface of the bead core and the carcass ply winding portion to be in a range of 0.5 to 8.0 mm, the rubber to the winding portion is formed. In addition, it is possible to sufficiently prevent the occurrence of early breakage or the like due to fretting or the like, and sufficiently prevent peeling or the like of the wound portion, thereby greatly improving the durability of the bead portion.

That is, the thickness of the rubber between them is as shown in FIG.
As shown in (a), when they are 0 mm and they are in contact with each other, the wound part will be broken at an early stage, and the thickness thereof is more than 0 mm and less than 0.5 mm. Then, the wound portion is peeled off because the relaxing action of the relative motion by the rubber is too small,
Further, when the maximum thickness of the rubber exceeds 8.0 mm as shown in FIG. 5 (b), the deformation of the tire at the time of load rolling causes a large distortion at the leading end of the wound portion, and In addition to the early peeling at the tip of the wound portion, there is a problem that air is easily trapped in the interposed rubber when molding the tire, which causes poor adhesion of the wound portion.

[0008] Here, when the 50% modulus of the rubber interposed between the outer peripheral surface of the bead core and the carcass ply winding portion is set to 1.0 to 8.5 MPa, the load on the tire is rolled. The distortion generated in the wound portion due to fretting by the relative movement between the outer peripheral surface of the bead core and the wound portion is reduced, and the durability is improved.

[0009] In other words, if it is less than 1.0 MPa, the rubber is too soft and the strain relief action is small.
If it exceeds 8.5 MPa, the rubber is too hard, and there is a high possibility that breakage will occur in the rubber.

[0010] In this tire, it is preferable that at least one of the winding portions is provided with a bent portion where the winding portion is bent toward the bead core so that the winding of the winding portion around the bead core can be performed reliably and accurately at all times. In addition, when the bent portion is located in correspondence with the corner of the polygonal bead core, the variation in the gap between the two exactly along the peripheral surface of the bead core. Less winding can be performed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view in the tire width direction showing an essential part of an embodiment of the present invention. This is achieved by disposing a bead core 2 having a polygonal cross section and a hexagonal shape in the figure in a tire bead portion 1 and a single carcass ply 3 around the bead core 2.
Is wound from the inside to the outside in the tire width direction, and the tip 3b of the wound portion 3a formed by this is positioned near the bead core 2. In the radial tire, the bead core 2 An outer peripheral surface 2a facing outward in the radial direction in a rim assembly posture of the tire, and a winding tip 3 substantially parallel to the outer peripheral surface 2a in the figure.
1c, the maximum thickness t of the rubber 4 having a 50% modulus in the range of 1.0 to 8.5 MPa is 0.5 mm as shown in FIG. b)
Is 8.0 mm as shown in FIG.

Further, as shown in FIG. 1, the wound portion 3a is inserted into the bead core 2 at two positions of the wound portion 3a.
Each bent portion 3d, 3e bent toward the side contributes to the definition of each corner 2b, 2c of the bead core 2, in this case, the outer peripheral surface 2a and the surface adjacent to the outer peripheral surface 2a inward in the tire width direction. The two corners adjacent to each other. In addition, the bending part of the winding part 3a includes the case of illustration, or except the case of illustration,
It can be formed corresponding to other corners.

According to the tire configured as described above,
In particular, by selecting the maximum thickness t of the rubber 4, as described above, in addition to early breakage and peeling of the wound portion 3 c, peeling of the wound portion distal end 3 b and the like can be sufficiently prevented, and The durability of the bead portion 1 can be greatly improved.

FIG. 2 is a sectional view showing another embodiment.
This is obtained by changing the winding mode of the winding portion 3a of the carcass ply 3, particularly at the winding tip 3c facing the outer peripheral surface 2a of the bead core 2. FIG.
In the mode shown in FIG. 2A, the wound tip portion 3c is curved so that the intermediate portion is away from the bead core outer peripheral surface 2a. The mode shown in FIG. )
Is provided with a flat portion that is substantially parallel to the outer peripheral surface 2a. In addition, the mode shown in FIG.
As compared with the position shown in FIG. 1, only the portion near the winding portion tip 3b is equivalent to a portion inclined in a direction away from the outer peripheral surface 2a, and the mode shown in FIG. 1 corresponds to the one obtained by omitting the bent portion 3e on the tip side of the wound portion 3a from the position shown in FIG.

In any of these embodiments shown in FIG. 2, the maximum thickness t of the rubber 4 existing between the bead core outer peripheral surface 2a and the wound tip portion 3c is 0.5 to 8.0.
mm, more preferably in the range of 1.0 to 5.0 mm.
Therefore, the same effect as described above can be obtained by any of these winding modes.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire for a heavy load vehicle having a size of 315/60 R22.5, comprising a carcass ply 3
The maximum thickness t of the rubber 4 between the wound tip portion 3c and the bead core outer peripheral surface 2a was changed as shown in FIG.
Attach a 2.5 rim and charge air pressure to 900
In a drum running test in which a load equivalent to twice the maximum load capacity was applied when kPa was applied, the running distance until the running became impossible due to a bead failure (separation at carcass ply end or wire chafer end, etc.) Was measured and index evaluation was performed using a conventional tire as a control. As a result, the bead portion durability shown in Table 1 was obtained.

[0017]

[Table 1]

In the conventional tire, the side portion of the carcass ply is rolled up as shown in FIG. 4A, and the comparative tires 1 and 2 respectively have the side portion of the carcass ply shown in FIG. (B) and (c) as shown in FIG.
0.0 mm. Further, the index values in the table indicate that the larger the value, the better the durability.

According to Table 1, all of the tires of the example were
The tire exhibits extremely excellent durability as compared with the conventional tire, and it is understood that this is remarkable in the example tires 3 to 5, in other words, when the maximum thickness of the rubber is in the range of 1.5 to 4.5 mm. .

[0020]

As apparent from the above description, according to the present invention, early breakage of the carcass ply at the winding portion can be sufficiently prevented, and the durability of the bead portion can be greatly improved. .

[Brief description of the drawings]

FIG. 1 is a main part sectional view showing an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing another embodiment.

FIG. 3 is a schematic sectional view showing an example tire.

FIG. 4 is a schematic sectional view showing a conventional tire and a comparative tire.

FIG. 5 is a schematic sectional view showing a case where the maximum thickness of rubber is out of a numerical range.

[Explanation of symbols]

 Reference Signs List 1 tire bead portion 2 bead core 2a outer peripheral surface 2b, 2c corner portion 3 carcass ply 3a winding portion 3b tip 3c winding tip portion 3d, 3e bending portion 4 rubber t maximum thickness

Claims (5)

[Claims] 1. A side portion of a carcass ply is wound around a bead core having a polygonal cross-section and disposed at a tire bead portion, and a tip of the wound portion is positioned near the bead core. A pneumatic tire, wherein a maximum thickness of rubber interposed between an outer peripheral surface of a bead core and a winding portion of a carcass ply is in a range of 0.5 to 8.0 mm. 2. The pneumatic tire according to claim 1, wherein the maximum thickness is in a range of 1.0 to 5.0 mm. 3. A rubber having a 50% modulus of 1.0 to 1.0.
The pneumatic tire according to claim 1, wherein the pneumatic tire has a range of 8.5 MPa. 4. At least one portion of the winding portion,
The pneumatic tire according to any one of claims 1 to 3, wherein the winding portion is provided with a bent portion bent toward the bead core. 5. The pneumatic tire according to claim 4, wherein the bent portion is located corresponding to a corner of the bead core.