JP4615654B2 - Pneumatic tire - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention prevents a pneumatic tire, in particular, a pull-out of a ply cord and a separation at an edge position of a rewinding portion of a carcass ply, and a rim flange under a high load load action as a fulcrum. An object of the present invention is to provide a pneumatic tire that effectively suppresses bead portion failure due to bending deformation of the bead portion and improves bead portion durability. The present invention is preferably applied to a so-called heavy-duty pneumatic radial tire that is used under high load and high internal pressure conditions such as trucks and buses.
[0002]
[Prior art]
The pneumatic tire, in order to prevent pullout of the ply cords during tire rotation under load, usually, as shown in FIG. 7 (a), the carcass plies 100, around the bead core 102 of the bead portion 101, The wrapping portion 103 is embedded and fixed in a rubber material by largely rewinding from the inner side to the outer side in the tire width direction.
[0003]
[Problems to be solved by the invention]
However, the conventional tire having such a bead portion structure, when the load rolling of the tire, as the side wall portion 104 is a large bending deformation, especially at high applied load acts, the carcass ply 100 of FIG. 7 (a) A pulling force F acts in the direction of the arrow, and at the end edge position 105 of the rewinding portion 103 of the carcass ply 100, there is a rigid step on the inner and outer sides in the tire radial direction with this as a boundary. Due to the repeated stress concentration in the vicinity, separation of the ply cord from the rubbery material is likely to occur, and this separation causes a bead crack Cr as shown in FIG. 7 (b).
[0004]
Wound as a means for improving the bead portion durability by preventing such separation, as shown in FIG. 8 (a), the rewinding section 107 of the carcass ply 106, which wraps around it along the peripheral surface of the bead core 108 The present applicant has proposed in the specification of Japanese Patent Application No. 11-19847 that has already been filed that it is useful to provide the embedding portion 109.
[0005]
However, when the bead portion is not provided with reinforcing layer such as a wire chafer, when high load load acts on the tire, the fulcrum rim flange 110, as indicated by the two-dot chain line shown in FIG. 8 (b) As a result, a large bending deformation occurs in the direction of the arrow A. By repeating this bending deformation, cracks are likely to occur in the bead portion of the tire that comes into contact with the rim flange. There is a risk of failure.
[0006]
Further, as means for improving the bead portion durability of the tire having the bead portion structure, as shown in FIG. 9 (a), the tire is placed around the bead core 111 at the bead portion and at the outer position of the carcass ply 110. It is useful to suppress the bending deformation of the bead portion under the action of a high load load on the tire by disposing at least one reinforcing layer 112 wound back from the inner side to the outer side in the width direction.
[0007]
However, as shown in FIG. 9 (b), depending on the edge position of the reinforcing layer 112, stress concentrates on the edge position 113, and a failure such as a bead crack Cr may occur at the position 113. As a result, the bead durability could not be effectively increased.
[0008]
Accordingly, an object of the present invention is to prevent the pull-out of the ply cord and the occurrence of separation at the edge position of the turn-up portion of the carcass ply, and the bead portion having a rim flange as a fulcrum particularly under the action of a high load load An object of the present invention is to provide a pneumatic tire that effectively suppresses bead portion failure due to bending deformation of the bead and improves bead portion durability.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a pneumatic tire according to the present invention comprises a main body portion formed by extending at least one carcass ply made of a steel cord from a tread portion to a bead portion through a sidewall portion, and a bead. A pneumatic tire formed of a rewinding portion wound around a bead core embedded in the portion, and a winding portion wound around the bead core is provided on the rewinding portion of the carcass ply. The bead portion is provided with at least one reinforcing layer wound from the inner side to the outer side in the tire width direction around the bead core along the surface of at least a part of the turned-up portion from the main body portion of the carcass ply. And the wrapping edge position of the reinforcing layer is set in the tire radial direction from the outermost position in the tire radial direction where the bead portion of the tire is in contact with the rim flange. Placed inside, at least one layer of the reinforcing layer is obtained by arranged and along the rewinding unit to winding portion of the carcass ply.
[0010]
In addition, the “carcass ply rewinding portion” referred to here is formed by rewinding from the inner side to the outer side in the tire width direction, and is also wound from the outer side to the inner side in the tire width direction. The case where it is formed by is also included.
[0011]
In addition, the carcass ply here is not only a substantially radial arrangement of a number of steel cords cut at both ends, but a single steel cord is folded back at the rewinding portion of the carcass ply, and the tire circumferential direction It also includes those that are extended while making a detour.
[0012]
Further, the reinforcing layer is preferably a wire chafer composed of a rubberized layer of steel cord or an organic fiber chafer composed of a rubberized layer of organic fiber cord, and further, these chafers. The reinforcing layer can also be configured by combining the above.
[0013]
Here, the term "predetermined condition" means applying the maximum air pressure and the maximum load capacity for the tire assembled to a standard rim defined in JATMA, it is similarly defined.
[0014]
Furthermore, when it is necessary to reliably maintain the reinforcing layer around the bead core in the desired shape, the reinforcing layer is preliminarily plastically deformed so that it follows the winding portion of the carcass ply. It is preferable to use a simple shape.
[0015]
In addition, when there is a possibility that the bead core and the cord of the carcass ply opposed to the bead core come into contact, the entire surface of the bead core is covered with a hard rubber layer, and the carcass ply is wound along the outer surface of the hard rubber layer. It is preferable. More preferably, the hard rubber layer has a modulus at 55% elongation of 5.5 to 9.0 MPa. The modulus at 50% elongation is measured according to JIS 6251.
[0016]
More preferably, the tire is a heavy duty tire.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on the drawings. FIG. 1 shows an example of a cross section of a bead part of a general pneumatic tire. In the figure, 1 is a bead part, 2 is a carcass ply, 3 is a side wall part, 4 is a bead core, and 5 is a reinforcing layer. is there.
[0018]
The tire having the bead portion 1 shown in FIG. 1 preferably has at least rubberized steel cords arranged substantially in a radial direction (specifically, a direction of 70 to 90 ° with respect to the tire equatorial plane). A single carcass ply 2 is wound around a body portion 2a extending in a toroidal manner from a tread portion (not shown) through a sidewall portion 3 to a bead portion 1 and a bead core 4 embedded in the bead portion 1. A belt (not shown) composed of one or more cord rubberized layers is arranged on the crown portion (not shown) of the carcass ply 2 to reinforce the tread portion. To do.
[0019]
The main structural features of the present invention employ a bead structure in which the carcass ply 2 is wound around the bead core 4 and further suppresses bending deformation of the bead portion when a high load load acts on the tire. More specifically, the reinforcing layer 5 is provided, and more specifically, the winding portion 2b of the carcass ply 2 is provided with a winding portion 6 that wraps around the circumferential surface of the bead core. At least one reinforcing layer 5 is disposed around the bead core 4 from the inner side to the outer side in the tire width direction 7 along the surface of at least one part of the carcass ply 2 from the main body 2a. By adopting this configuration, the bead portion durability can be significantly improved.
[0020]
That is, by winding the carcass ply 2 around the bead core 4, it is possible to prevent the carcass ply 2 from being pulled out and the separation at the winding edge position 8 of the carcass ply 2 can be prevented. Compared to the conventional tire (FIG. 10 ), the bead portion is significantly reinforced.
[0021]
However, with this configuration alone, when a high load load is applied to the tire, it is not possible to effectively suppress a large bending deformation with the rim flange as a fulcrum. The bead part is easily cracked.
[0022]
For this reason, in the present invention, in addition to the above-described configuration, the bead portion 1 is further provided in the tire width direction 7 around the bead core 4 along the surface of at least one part of the winding portion 2b from the main body portion 2a of the carcass ply 2. In this configuration, at least one reinforcing layer 5 wound back from the inside to the outside is provided, and this configuration can effectively suppress the bending deformation, and as a result, the bead portion durability is remarkably improved. Can be improved.
[0023]
The reinforcing layer 5 is preferably a wire chafer 9 made of a rubberized layer of steel cord as shown in FIG. 1 when the bead portion 1 is effectively reinforced.
[0024]
However, when the wire chafer is arranged as shown in Fig. 9 (a), the steel cord has high rigidity, so stress concentrates on the rewind edge position 103 and a bead such as a separation at this position. There is a risk of partial failure.
[0025]
For this reason, when the inventor made various studies, the winding end edge position 10 of the wire chafer 9 is outside the predetermined position 12 of the tire bead portion 1 in contact with the rim flange 11 in the tire radial direction. In some cases, it has been found that bead failure is likely to occur.
[0026]
Therefore, the reinforcing layer 5 is a wire chafer 9, and the rewind edge position 10 is located on the inner side in the tire radial direction from the outermost position 12 in the tire radial direction where the bead portion 1 of the tire contacts with the rim flange. It is preferable to arrange. Here, “the winding end edge position 10 is in the tire radial direction inner side than the tire radial direction outermost position 12”, specifically, as shown in FIG. When the straight line m is drawn from the position 12 in a direction perpendicular to the outer surface of the bead portion, the winding end edge position 10 is located on the inner side in the tire radial direction from the straight line m. In addition, as shown in FIG. 6 , when the winding end edge position 10 is considerably inside the tire radial direction than the outermost position 12 in the tire radial direction, the outer surface of the bead portion that contacts the rim flange is cracked. Therefore, it is more preferable that the rewind edge position 10 has a distance measured in the tire radial direction from the straight line m shorter than 25 mm.
[0027]
Further, when the reinforcing layer 5 is made of a rubberized layer of an organic fiber cord such as a nylon chafer 13 as shown in FIG. 4 , the winding edge position 10 of the reinforcing layer 5 is not particularly limited. It is more preferable that the rewind edge position 10 is located on the inner side in the tire radial direction 14 than the outermost position 12 in the tire radial direction where the bead portion 1 of the tire under predetermined conditions comes into contact with the rim flange 11. .
[0028]
In order to dispose the rewind edge position 10 of the reinforcing layer 5 on the inner side in the tire radial direction 14 than the outermost position 12 in the tire radial direction, at least one layer of the reinforcing layer 5 is as shown in FIG. Further, the winding portion 5b is disposed along the winding portion 6 of the carcass ply 2. With this configuration, it is possible to prevent the occurrence of separation at the winding end edge positions 8 and 10 of the reinforcing layer 5 and the carcass ply 2.
[0029]
Further, when the winding portion 5b of the reinforcing layer 5 is securely disposed along the winding portion 6 of the carcass ply 2, the reinforcing layer 5 is preliminarily plastically deformed and attached to the carcass ply 2. It is preferable that the shape be adapted to fit along the surface of the substrate.
[0030]
Further, in the case of a bead structure in which the carcass ply 2 is wound around the bead core 4, the rewinding portion 2 b of the carcass ply 2 wound around the bead core 4 by the pulling force acting on the ply 2 at the time of tire load rolling is As a result, the cord of the carcass ply 2 may come into direct contact with the bead core 4 and the cord may be damaged. In this case, the ply cord was broken, which was fatal particularly in the case of a corrected tire.
[0031]
Therefore, in such a case, it is preferable that the entire surface of the bead core 4 is covered with the hard rubber layer 15 and the carcass ply 2 is wound along the outer surface of the hard rubber layer 15.
[0032]
The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.
[0033]
【Example】
Next, since the pneumatic tire according to this invention was manufactured and the bead portion durability was evaluated, it will be described below.
[0034]
The tires of Examples 1 to 4 have a tire size of TBR 315 / 60R22.5. Table 1 shows the bead structure, the type of the reinforcing layer, and the rewind edge position.
[0035]
For comparison, has a bead portion winding structure, compared tire shown in FIG. 8 (a) except that without the wire chafer having a structure similar to that of the tires of Examples 1 (Comparative Example 1) When, the prototype also conventional tire shown in FIG. 10 to the bead portion and the normal rewind structure (conventional example).
[0036]
(Test Method) Each test tire was mounted on a 9.0 × 22.5 rim, and the bead durability was evaluated. The durability of the bead part is measured by measuring the distance traveled when a failure occurs in a tire when the tire is run on a rotating drum at a speed of 60 km / h under conditions of tire internal pressure: 900 kPa and tire load load: 70 kN. From this measured value, it evaluated. Table 1 shows the evaluation results. In addition, the numerical value of the bead portion durability in Table 1 is shown as an index ratio with the conventional example being 100, and the larger the value, the better. In addition, since the tire subjected to the durability test was subsequently removed from the rim and disassembled to examine which part of the tire had the failure, these are also shown in Table 1.
[0037]
[Table 1]
[0038]
From the evaluation result shown in Table 1, Examples 1-4 are excellent in bead part durability compared with the prior art example. On the other hand, both Comparative Examples 1 and 2 have a slightly improved bead durability compared to the conventional example. However, in Comparative Example 1, a failure due to the occurrence of external cracks was observed. In Comparative Example 2, a wire chafer was used. A failure from separation at the edge was observed.
[0039]
【The invention's effect】
According to the present invention, it is possible to provide a pneumatic tire excellent in bead portion durability. The present invention is preferably applied to a so-called heavy-duty pneumatic radial tire that is used under high load and high internal pressure conditions such as trucks and buses.
[Brief description of the drawings]
1 is a cross-sectional view of the bead portion of a typical pneumatic tire.
2 is a cross-sectional view of a bead portion of the tire of Example 1. FIG.
3 is a cross-sectional view of a bead portion of a tire of Example 2. FIG.
4 is a cross-sectional view of a bead portion of a tire of Example 3. FIG.
FIG. 5 is a cross-sectional view of a bead portion of a tire according to a fourth embodiment.
FIG. 6 is a diagram for explaining a problem when the winding edge position of the wire chafer is too far inside the tire radial direction.
FIG. 7 is a view for explaining problems of a tire having a conventional bead structure.
8 is a cross-sectional view of a bead portion of a tire of Comparative Example 1. FIG.
9A is a cross-sectional view of the bead portion of the tire of Comparative Example 2, and FIG. 9B is a view when cracks Cr are generated in the bead portion of the tire shown in FIG. 9A.
FIG. 10 is a cross-sectional view of a bead portion of a conventional tire.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bead part 2 Carcass ply 3 Side wall part 4 Bead core 5 Reinforcement layer 6 Winding part 7 Tire width direction 8 Carcass ply rewinding edge position 9 Wire chafer
10 Rewind edge position of wire chafer
11 Rim flange
12 The outermost position in the tire radial direction where the tire bead portion 1 contacts the rim flange 11 under predetermined conditions.
13 Nylon chafer
14 Tire radial direction
15 Hard rubber layer

Claims (6)

Consists of at least one carcass ply made of steel cord, with a main body part that extends toroidal from the tread part through the sidewall part to the bead part, and a rewinding part that is rolled back around the bead core embedded in the bead part In the pneumatic tire that is
In the winding part of the carcass ply, a winding part is provided that winds along the circumferential surface of the bead core,
The bead portion is provided with at least one reinforcing layer wound around the bead core from the inner side to the outer side in the tire width direction along the surface of at least one part of the turned-up portion from the main body portion of the carcass ply. ,
The winding end edge position of the reinforcing layer is disposed on the inner side in the tire radial direction from the outermost position in the tire radial direction where the bead portion of the tire under predetermined conditions comes into contact with the rim flange ,
The pneumatic tire according to claim 1, wherein at least one of the reinforcing layers is disposed so that a turn-up portion is provided along a turn-up portion of the carcass ply .   The pneumatic tire according to claim 1, wherein the reinforcing layer is a wire chafer made of a rubberized layer of a steel cord.   The pneumatic tire according to claim 1, wherein the reinforcing layer is an organic fiber chafer made of a rubberized layer of an organic fiber cord.   The pneumatic tire according to claim 1, wherein the reinforcing layer is a wire chafer made of a rubberized layer of steel cord and an organic fiber chafer made of a rubberized layer of organic fiber cord. The pneumatic tire according to any one of claims 1 to 4, wherein the reinforcing layer is preliminarily plastically deformed and formed into a shape suitable for being along the winding portion of the carcass ply. The pneumatic tire according to any one of claims 1 to 5 , wherein the tire is a heavy duty tire.