JP4438452B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire in which the durability of a bead portion is improved by suppressing the occurrence of a shift in a joint surface between a bead core embedded in a bead portion and a bead filler.

  Generally, in a bead portion of a pneumatic tire, an assembly in which a bead filler made of high-hardness rubber having a substantially triangular cross-section is bonded to the outer peripheral side of the bead core (hereinafter referred to as bead assisy in the present invention) By making it the structure which wraps the circumference | surroundings of this bead assembly so that it may wrap with a carcass layer, side rigidity is ensured and steering stability is obtained (for example, refer patent document 1).

The bead assembly 53 is formed by integrally bonding a bead filler 52 to the outer peripheral surface of a bead core 51 having a rectangular cross section as illustrated in FIG. However, even if the bead filler 52 is bonded to the outer periphery of the bead core 51 at a regular position as shown by the solid line in FIG. 5, the end of the carcass layer is folded back or the bead is blown by inflation in the green tire molding process. By receiving a lateral force in the process of raising the part, the bead filler 52 may be displaced with respect to the bead core 51 as indicated by a chain line in FIG. Air remains in the stepped portion 55 caused by this positional shift, which causes stress concentration in the tire after vulcanization and causes damage to the bead portion.
Japanese Patent Laid-Open No. 11-129711

  An object of the present invention is to eliminate such problems, and to provide a pneumatic tire that improves the durability of the bead portion by suppressing the occurrence of deviation in the joint surface between the bead core and the bead filler. It is in.

In order to achieve the above object, the pneumatic tire of the present invention is a pneumatic tire having a bead portion in which a bead filler is joined to each of the outer peripheral sides of a pair of left and right bead cores. An inner member that forms a joint surface with a surface in a step shape in a tire cross-section, fits the joint surfaces to each other, and bisects the bead filler in a tire width direction at a position corresponding to the stepped step. It is composed of an outer member, and at least two layers of cord reinforcing layers in which the cord directions cross each other are interposed between the inner member and the outer member, and both ends of each layer between adjacent layers are shifted from each other. The arrangement is as follows.

The pneumatic tire of the present invention forms a joint surface between the outer peripheral surface and the bead inner peripheral surface of the filler of the bead core in a stepwise manner, corresponding Rutotomoni fitted together the bonding surfaces, a bead filler in a staircase-like steps An inner member and an outer member that are bisected in the tire width direction at a position where at least two layers of cord reinforcing layers in which the cord directions cross each other are interposed between the inner member and the outer member; and Since both ends of each layer between adjacent layers are arranged so as to be displaced from each other, misalignment occurs even if a lateral external force is applied through the folding process of the end of the carcass layer after the bonding process of the bead core and the bead filler. This prevents the occurrence of air accumulation and improves the durability of the bead portion.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

1 is a half sectional view showing an outline of the pneumatic tire of the present invention, FIGS. 2 and 3 are sectional views showing a reference example of a bead assembly in the tire of FIG. 1, and FIG. 4 is a bead in the pneumatic tire of the present invention. It is sectional drawing which shows embodiment of an assembly .

The pneumatic tire 1 has a carcass layer 3 mounted between a pair of left and right bead portions 2 and 2, and both end portions 3 a are hard from the tire inner side to the tire outer side around a bead core 4 embedded in the bead portion 2. It is folded so as to wrap the bead filler 5 made of the rubber composition. The outer peripheral surface of the bead core 4 and the inner peripheral surface of the bead filler 5 are respectively formed in a step shape in the tire cross section, and by fitting these joint surfaces together, a bead assembly 6 is formed as shown in the reference example of FIG. Forming.

  Thereby, even if the bead assembly 6 receives an external force in the tire molding process, no positional deviation occurs between the bead core 4 and the bead filler 5, and no air accumulation due to the positional deviation occurs. The durability of the bead portion in the tire after vulcanization can be improved.

In the present invention, the basic form of the reference example of FIG. 2 described above, in order to improve the driving performance by increasing the side rigidity of the tire, as illustrated in reference example of FIG. 3, the bead filler 5 stairs The inner member 5A and the outer member 5B are divided into two in the tire width direction at the position of the step, and the cord reinforcing layer 7 is interposed so as to wrap around the boundary surface . Further, as shown in the figure, the cord reinforcing layer 7 is arranged along the stepped step of the bead core 4 . As a result, the cord reinforcing layer 7 further suppresses the occurrence of misalignment of the bead assembly 6 in the tire molding process.

Furthermore, in the present invention, as illustrated in FIG. 4, the cord reinforcing layer 7 is composed of a plurality of layers (two layers in the drawing), and both ends of the cord reinforcing layers 7a and 7b are arranged so as to be separated from each other by steps. the cord reinforcing layer between layers so that cross the direction of the code with each other. As a material for the reinforcing layer cord layer 7, a steel cord or an organic fiber cord may be used. Most preferably, a steel cord is used.

In the pneumatic tire 1 of the present invention , the inner member 5A and the outer member 5B can be composed of different rubber compositions in order to impart desired exercise performance to the tire according to the user's request.

  Thus, when using a different rubber composition for both members 5A and 5B, for example, as the JIS-A hardness of the rubber composition, the inner member 5A located inside the tire is set to 70 to 98, and the outer side of the tire is It is preferable that the outer member 5B positioned at 60 is 85 to 85, and the hardness of the inner member 5A is larger than the hardness of the outer member 5B. Also, as the modulus at 100% elongation of the rubber composition, the inner member 5A may be 3 to 9 MPa, the outer member 5B may be 6 to 13 MPa, and the modulus of the inner member 5A may be smaller than the modulus of the outer member 5B. More preferably, the hardness of the outer member 5B is 60 to 90% of the hardness of the inner member 5A, and the modulus of the inner member 5A is 50 to 90% of the modulus of the outer member 5B. By setting in this way, riding comfort can be improved while maintaining steering stability of the tire.

  Furthermore, in order to adjust the balance between steering stability and riding comfort, the positions of the outer ends in the tire radial direction of the inner member 5A and the outer member 5B in the bead assembly 6 can be changed. By doing in this way, even if the physical properties of the inner and outer members 5A and 5B are made equal, it is possible to arbitrarily obtain a steering stability-oriented or ride-oriented tire.

As described above, the pneumatic tire of the present invention forms a joint surface between the outer peripheral surface of the bead core 4 and the inner peripheral surface of the bead filler 5 constituting the bead assembly 6 embedded in the bead portion 2 in a stepped manner. The joint surfaces are fitted to each other , and the bead filler is composed of an inner member and an outer member that bisect in the tire width direction at a position corresponding to the stepped step, and the interlayer is interposed between the inner member and the outer member. By disposing at least two cord reinforcing layers intersecting the cord direction and shifting both ends of each layer between adjacent layers , air is generated between the bead assembly 6 and the carcass layer 3. It prevents the residue and improves the durability of the bead portion 2 .
In addition, below, the reference example which shares a part of structural requirements with the pneumatic tire of this invention is described.

Reference example

Reference example 1
The tire size is 205 / 60R1489H, and all the specifications except for the bead assembly structure are used in common. The conventional tire (conventional example 1) comprising the assembly 6 having the structure shown in FIG. 6A and the assembly having the structure shown in FIG. 6 reference tires (Reference Example 1) were produced.

  Each of the two types of tires was filled with an air pressure of 200 kPa, and the durability of the bead portion was examined by the following test method. The results are shown in Table 1 by index display with the conventional example 1 as 100. The larger the value, the better.

[durability]
Each tire was run using a drum testing machine in accordance with the durability test method specified in JIS D4230, and the running distance until the tire failed was measured.

As shown in Table 1, it can be seen that the durability of the bead portion of the reference tire is improved as compared with the conventional tire. Further, when the bead portion of the failed tire was disassembled and examined, it was confirmed that the cause of the failure was a separation caused by an air pool remaining between the bead filler 5 and the bead core 4.

Reference example 2
Similarly to the above, the tire size is 205 / 60R1489H, all the specifications except for the structure of the assembly are used in common, and the conventional tire (conventional example 2) made of the assembly 6 having the structure of FIG. A reference tire (Reference Example 2) comprising the assembly 6 having a structure was manufactured. Each reinforcing layer 7 was formed by placing steel cords (structure: 2 + 2 × 0.25) at a driving density of 40 pieces / 50 mm, and the cord angle with respect to the tire circumferential direction was 60 °.

  Each of the two tires was filled with an air pressure of 200 kPa, and the durability of the bead portion was examined by the same test method as described above. The larger the value, the better.

As shown in Table 2, it can be seen that the durability of the bead portion of the reference tire is improved as compared with the conventional tire. In addition, when the bead part of the failed tire was disassembled and examined, it was confirmed that the cause of the failure was a separation caused by air remaining in the bead filler 5 and the bead core 4.

It is a half sectional view showing the outline of the pneumatic tire of the present invention. It is sectional drawing which shows the reference example of the bead assembly in the tire of FIG. It is sectional drawing which shows the other reference example of the bead assembly in the tire of FIG. It is a cross-sectional view showing the implementation form of the bead assembly in a pneumatic tire of the present invention. It is sectional drawing for demonstrating generating of the shift | offset | difference in the conventional bead assembly. (A) And (b) is sectional drawing which shows the form of the bead assembly of the prior art examples 1 and 2 employ | adopted in [reference example] , respectively .

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 3 Carcass layer 4 Bead core 5 Bead filler 5A Inner member 5B Outer member 6 Beaded assy 7, 7a, 7b Reinforcement cord layer

Claims (6)

In a pneumatic tire having a bead portion in which a bead filler is joined to each of the outer peripheral sides of a pair of left and right bead cores,
A joint surface between the outer peripheral surface of the bead core and the inner peripheral surface of the bead filler is formed in a step shape in a tire cross section, and the joint surfaces are fitted to each other , and the bead filler corresponds to the stepped step. An inner member and an outer member that are bisected in the tire width direction at a position where at least two layers of cord reinforcing layers in which the cord directions cross each other are interposed between the inner member and the outer member; and A pneumatic tire arranged such that both ends of each layer between adjacent layers are shifted from each other . The pneumatic tire according to claim 1, wherein the inner member and the outer member are made of different rubber compositions. In JIS-A hardness of 70 to 98 of the inner member, the JIS-A hardness of the outer member is 60 to 85, and claim 2, the hardness of the inner member is greater than the hardness of the outer member Pneumatic tires. Wherein in at 100% elongation modulus of the inner member 3～9MPa, the outer at 100% elongation modulus of the member is 6～13MPa, and claim 2 in which the modulus of the inner member is smaller than the modulus of the outer member Or the pneumatic tire of 3 . The pneumatic tire according to any one of claims 1 to 4, wherein a radially outer end of the inner member and a radially outer end of the outer member are different from each other. The pneumatic tire according to claim 1, wherein the cord reinforcing layer is made of a steel cord or an organic fiber cord.

Images