JP2005125947A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire improving steering stability without decreasing durability of a bead part. <P>SOLUTION: The pneumatic tire 1 embeds a bead core 4 disposing a bead filler 5 at the outer periphery in a pair of right and left bead parts 2. The bead filler 5 is divided into two parts, an inner side member 5A and an outer side member 5B in the tire width direction, and at least one layer of a code reinforcing layer 6 is embedded so as to be packed between the both members 5A, 5B. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire with improved steering stability without reducing the durability of a bead portion.

  In general, a bead portion of a pneumatic tire is embedded with a high-hardness bead filler having a substantially triangular cross section on the outer peripheral side of the bead core, and the bead core and the bead filler are folded back so as to wrap at the end of the carcass layer. Thus, the side rigidity is ensured and the steering stability is obtained.

Conventionally, in a tire that emphasizes handling stability rather than riding comfort, such as a hyper performance tire, a cord reinforcing layer 6 such as a steel cord is added to the bead portion 2 as shown in FIGS. There is a proposal to improve the maneuverability by increasing the side rigidity (see Patent Document 1). However, since the cord reinforcing layer 6 is disposed, stress concentrates on the terminal to cause peeling, and there is a problem that durability is lowered. In particular, as shown in FIG. 6, when the inner end portion of the cord reinforcing layer 6 is buried in the bead core 4, the productivity is greatly reduced and an air pool is generated at the inner end portion of the reinforcing layer 6. In addition, there is a problem of further reducing durability.
Japanese Patent Laid-Open No. 2001-55023 (FIGS. 1, 4, and 5)

  An object of the present invention is to solve such problems, and to provide a pneumatic tire that improves steering stability without deteriorating the durability of the bead portion.

  In order to achieve the above object, the pneumatic tire of the present invention is a pneumatic tire in which a bead core having a bead filler disposed on the outer peripheral side is embedded in a pair of left and right bead portions, and the bead filler is disposed on the outer side in the tire width direction. The member is divided into two parts, and at least one cord reinforcing layer is embedded between the two members so as to wrap inside.

  In the pneumatic tire of the present invention, the bead filler is divided into the inner member and the outer member, and the cord reinforcing layer is embedded between the inner member and the outer member, so that the cord reinforcing layer is wrapped in the high-hardness rubber composition. As a result, stress concentration on the end of the cord reinforcing layer can be eliminated, and the durability of the bead portion can be improved. Furthermore, steering stability can be improved by inserting the cord reinforcing layer into the bead filler.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. In each figure, the same code | symbol is attached | subjected to a common component and the overlapping description is abbreviate | omitted.

  FIG. 1 is a half sectional view showing an example of the pneumatic tire of the present invention, and FIG. 2 is a sectional view for explaining the structure of the main part of FIG.

  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. As shown in FIG. 2, the bead filler 5 includes an inner member 5A and an outer member 5B which are divided into two in the tire width direction, and is embedded so as to wrap the cord reinforcing layer 6 in the boundary surface. An assembly of the bead filler 5 and the bead core 4 is such that the cord reinforcing layer 6 is in a state where the lower end is in contact with the outer peripheral surface of the bead core 4 and the upper end is wrapped so as not to protrude from the outer peripheral end of the bead filler 5. (Hereinafter referred to as bead assidy) 7 is formed.

  The cord reinforcing layer 6 is not limited to one layer, and a plurality of layers may be provided. FIG. 3A illustrates a case where the cord reinforcing layer embedded in the bead filler 5 is composed of two layers 6A and 6B. Thus, when embedding a plurality of reinforcing layers, it is preferable to arrange them so that the directions of the cords constituting the reinforcing layers intersect each other between adjacent layers. The bead assembly 7 in FIG. 3 (a) includes an inner member 5A and a cord in which a cord reinforcement layer 6A is bonded to the inner surface as illustrated in FIG. It can be manufactured by combining the outer member 5B having the reinforcing layer 6B bonded to the inner surface and joining the outer member 5B to the outer peripheral surface of the bead core 4.

  Thus, by burying the cord reinforcing layer 6 between the inner member 5A and the outer member 5B so as to completely wrap inside, the end of the cord reinforcing layer 6 becomes constrained by a hard rubber composition, Stress concentration on the terminal can be eliminated. Therefore, the separation at the cord reinforcement layer 6 terminal hardly occurs, and the steering stability is improved without deteriorating the durability of the bead portion 2.

  In the present invention, the inner member 5A and the outer member 5B described above can be composed of different rubber compositions. Thus, when using a different rubber composition for both members 5A and 5B, as JIS-A hardness of a rubber composition, inner member 5A shall be 70-98, and outer member 5B shall be 60-85. The hardness of the inner member 5A is preferably equal to or higher than that of the outer member 5B. Moreover, it is preferable that the 100% modulus of the rubber composition is 3 to 9 MPa for the inner member 5A, 6 to 13 MPa for the outer member 5B, and the modulus of the inner member 5A is equal to or less than that of the outer member 5B. More preferably, the JIS-A hardness of the outer member 5B is 60 to 90% of the JIS-A hardness of the inner member 5A, and the 100% modulus of the inner member 5A is 50 to 100% of the 100% modulus of the outer member 5B. 90% is recommended. By doing in this way, riding comfort can be improved, maintaining steering stability.

  Further, in order to adjust the balance between steering stability and riding comfort, the heights of the inner member 5A and the outer member 5B in the bead filler 5 in the tire radial direction are different from each other as illustrated in FIG. h1 and h2. In the figure, the case where the height h1 of the inner member 5A is higher than the height h2 of the outer member 5B is illustrated, but the relationship between the heights may be reversed. By doing in this way, even when 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 riding comfort-oriented tire.

  The material of the reinforcing layer 6 in the present invention is not particularly limited, but a steel cord or an organic fiber cord is preferably used, and a steel cord is particularly preferable.

Examples 1 and 2
Conventional tires (conventional examples 1 and 2) made of an assembly having the structure shown in FIG. 5 (c) and tires of the present invention made of an assembly having the structure shown in FIG. 3 (a) with the tire size 205 / 60R14 89H (Example 1) 2) was produced. Each of the reinforcing layers 6A and 6B is configured with a steel cord (structure: 2 + 2 × 0.25) driven in at a density of 40/50 mm, a cord angle with respect to the tire circumferential direction is 60 °, and the directions of the cords between the layers are mutually Arranged to intersect.

  Each of the above four tires was filled with an air pressure of 200 kPa, and the steering stability and durability were examined by the following test method. The results are shown in Table 1 along with the main specifications and the index display with the conventional example 1 as 100. Described. The larger the value, the better.

[Steering stability]
Various tires were mounted on a domestic 1800cc class passenger car, run on a test course, and evaluated by a sensory test with a skilled test driver.

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

  As a result, it can be seen that the tire according to the present invention has improved steering stability and durability in a well-balanced manner as compared with the conventional tire.

Examples 3 to 8 and Comparative Example In the same manner as above, the tire size is 205 / 60R14 89H, and the conventional tire (conventional example 3) made of the assembly having the structure of FIG. The tires of the present invention (Examples 3 to 8) made of the assembly having the assembly and the comparative tire (Comparative Example) made of the assembly having the structure of FIG. 6 were produced. In addition, each reinforcement layer 6 comprised the steel cord (structure: 2 + 2 * 0.25) as a driving density of 40 pieces / 50mm, and arrange | positioned so that the cord angle with respect to a tire circumferential direction might be 60 degrees.

  Each of the above 8 tires is filled with an air pressure of 200 kPa, and the handling stability, durability and riding comfort are examined by the following test methods. Are listed in Table 1. The larger the value, the better.

[Steering stability] and [Durability]
Same as above test method [Riding comfort]
Various tires were mounted on a domestic 1800cc class passenger car, run on a test course, and evaluated by a sensory test with a skilled test driver.

  As a result, it can be seen that the tire of the present invention is improved in handling stability, durability and riding comfort in a well-balanced manner as compared with the conventional tire and the comparative tire.

It is a half sectional view showing an example of the pneumatic tire of the present invention. It is sectional drawing for demonstrating the structure of the principal part of FIG. (A) is sectional drawing equivalent to FIG. 2 which shows other embodiment of this invention, (b) is explanatory drawing which illustrates the method of manufacturing this. It is sectional drawing equivalent to FIG. 2 which shows other embodiment of this invention. (A)-(c) is explanatory drawing for demonstrating the arrangement structure of the reinforcement layer in the conventional bead part. It is sectional drawing corresponded in FIG. 2 for demonstrating the improved structure of the bead assembly buried in the conventional bead part.

Explanation of symbols

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, 6A, 6B Cord reinforcement layer 7 Beaded assie

Claims (7)

In a pneumatic tire in which a bead core having a bead filler disposed on the outer peripheral side is embedded in a pair of left and right bead parts,
A pneumatic tire in which the bead filler is divided into an inner member and an outer member in the tire width direction, and at least one cord reinforcing layer is embedded between the two members inside.   The pneumatic tire according to claim 1, wherein the cord reinforcing layer includes a plurality of laminated bodies in which cords cross each other between layers.   The pneumatic tire according to claim 1 or 2, wherein the inner member and the outer member are made of different rubber compositions.   The JIS-A hardness of the rubber composition is 70 to 98 for the inner member, 60 to 85 for the outer member, and the inner member is equal to or greater than the outer member. Pneumatic tire.   5. The rubber composition according to claim 3, wherein a 100% modulus of the rubber composition is 3 to 9 MPa for the inner member, 6 to 13 MPa for the outer member, and the inner member is equal to or less than the outer member. Pneumatic tire.   The pneumatic tire according to any one of claims 1 to 5, wherein heights in the tire radial direction of the inner member and 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.

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