JP2003118324A - Run-flat tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a run-flat tire capable of satisfying both of run-flat running performance and riding comfortableness performance in ordinary running. SOLUTION: This run-flat tire has a reinforced rubber layer 8 on an inner side in the axial direction of the tire in a side wall part 3. The reinforced rubber layer 8 is constituted by laminating a first reinforcing layer 80 having durometer A hardness of 45 to 65 degrees and a second reinforcing layer having durometer A hardness of 65 to 85 degrees alternately along the radial direction of the tire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a run flat tire having a reinforcing rubber layer on the inner side of the sidewall portion in the tire axial direction.

[0002]

2. Description of the Related Art A run-flat tire is a tire that has a reduced air pressure due to a flat tire or the like.
A tire that can travel a certain distance. As one of the tire structures for enabling such run-flat traveling, there is known one in which the inner surface of the sidewall portion is reinforced by a reinforcing rubber layer (for example,
JP-A-8-34214, JP-A-9-11714, etc.).

FIG. 3 shows the structure (cross-sectional view) of such a side wall reinforced run flat tire. Since the tire 1 is symmetrical in the tire width direction, the right half of the tire equator line C is shown.

The tire 1 has a tread portion 100 that comes into contact with a road surface and a sidewall portion 101 that is located on a side surface.
And a rim strip portion 102. Further, it has a pair of bead portions 103 in the tire axial direction (width direction) and a carcass layer 104 so as to be bridged between the pair of bead portions 103.

The carcass layer 104 is provided so as to be folded back from the inside to the outside at the bead portion 103, and the bead apex rubber 105 is provided so as to be sandwiched between the folded portions of the carcass layer 104. Further, the reinforcing rubber layer 1 is provided inside the carcass layer 104.
06 is provided. The reinforced rubber layer 106 has a durometer A hardness (JIS A hardness) of about 70 to 80 and a cross-sectional shape of a substantially crescent shape. The sidewall portion 101 is reinforced by the reinforcing rubber layer 106.

When the inner pressure of the tire becomes zero due to the air deflation in the tire due to a flat tire or the like, the flexural deformation of the tire becomes large. In order to suppress this deformation, the side wall portion 101 is provided with the reinforcing rubber layer 106.
The flexural deformation of the sidewall portion 101 can be suppressed.

[0007]

DISCLOSURE OF THE INVENTION As described above,
The rubber used as the reinforcing rubber layer has a high hardness. Runflat performance can be ensured by using rubber having a high hardness.

However, when the rubber hardness of the side wall portion becomes large, the vibration characteristics and riding comfort during normal running deteriorate. High-performance tires require not only run-flat running performance but also riding comfort during normal running. The present invention has been made in view of the above circumstances, and an object thereof is to provide a runflat tire that can satisfy both the runflat running performance and the ride comfort performance during normal running.

Means for Solving the Problems To solve the above problems, a runflat tire according to the present invention is a runflat tire having a reinforcing rubber layer on the inner side in the tire axial direction of a sidewall portion, wherein the reinforcing rubber layer is A first reinforcing layer having at least a first hardness along the tire radial direction,
A plurality of reinforcing layers including a second reinforcing layer having a second hardness are alternately laminated and configured. According to this structure, the sidewall portion has the reinforcing rubber layer in which at least two reinforcing layers of the first reinforcing layer and the second reinforcing layer are alternately laminated along the tire radial direction.
Here, in the case of being composed of two layers, the first reinforcing layer is made of rubber having a relatively low hardness of the first hardness, and the second reinforcing layer is made of rubber having a relatively high hardness of the second hardness. It is formed.
By providing the second reinforcing layer, run-flat performance can be ensured, and by providing the first reinforcing layer, riding comfort can be ensured. Further, by alternately stacking the layers, the run-flat performance and the riding comfort can be taken into consideration over the entire sidewall portion.

As a preferred embodiment of the present invention, the first
The rubber of the reinforcing layer has a durometer A hardness of 45 to 65 degrees, and the rubber of the second reinforcing layer has a durometer A hardness of 65 to 65 degrees.
One that is 85 degrees.

If the rubber hardness of the first reinforcing layer is less than 45 degrees, the rigidity of this portion is locally reduced, which may be a base point of tire damage. If it exceeds 65 degrees, the vibration transmitted from the road surface is not effectively damped, and the durability is lowered. If the rubber hardness of the second reinforcing layer is less than 65 degrees, the longitudinal spring constant of the tire will not be improved, so that it will be difficult to suppress the flexure of the tire and the desired run-flat performance cannot be secured. On the other hand, if it exceeds 85 degrees, the rigidity of the tire becomes excessive and the riding comfort is significantly deteriorated.

[0011]

1 is a cross-sectional view of a run flat tire. Since the tire 1 is symmetrical in the tire width direction, the right half of the tire equator line C is shown.

The tire 1 has a tread portion 2 that comes into contact with a road surface, a sidewall portion 3 that is located on a side surface, and a rim strip portion 4. In addition, a pair of bead portions 5 are provided in the tire axial direction (left-right direction in FIG. 1 = tire width direction),
The carcass layer 6 is provided so as to be bridged between the pair of bead portions 5. The carcass layer 6 includes a first carcass ply and a second carcass ply, and each carcass ply is composed of a carcass cord wound around the tire equator line C at a predetermined angle. Organic fibers are mainly used as a material for carcass cords.

The carcass layer 6 is provided in the bead portion 5 so as to be folded back from the inside to the outside.
The bead apex rubber 10 is provided so as to be sandwiched between the folded portions. A reinforcing rubber layer 8 is provided inside the carcass layer 6. Reinforcement rubber layer 8
Has a substantially crescent-shaped cross section. Reinforcement rubber layer 8
Thereby, the sidewall portion 3 is reinforced.

When the air in the tire is deflated due to a flat tire or the like and the internal pressure becomes zero, the flexural deformation of the tire becomes large. In order to suppress this deformation, the reinforcing rubber layer 8 is provided on the sidewall portion 3, and thus, the bending deformation of the sidewall portion 3 can be suppressed.

As shown in FIG. 1, the reinforcing rubber layer 8 has a first rubber layer.
The reinforcing layer 80 and the second reinforcing layer 81 have a structure in which they are alternately laminated in the tire radial direction (arrow A direction). The first reinforcing layer 80 and the second reinforcing layer 81 have a durometer A
It is formed of rubber layers having different hardness. First reinforcing layer 80
The rubber has a durometer A hardness of 45 to 65 degrees (corresponding to the first hardness), and the rubber 81 of the second reinforcing layer has a durometer A hardness of 65 to 85 degrees (corresponding to the second hardness).
).

As described above, the soft rubber and the hard rubber are alternately laminated to satisfy both the run flat performance and the riding comfort.
By adopting a laminated structure, the rigid cross-section layer of the sidewall portion 3 disappears, and vibration resistance and riding comfort are improved. Furthermore, local stress concentration on the inner surface of the sidewall portion can be avoided. As described above, the entire reinforcing rubber layer 8 can be configured with good balance. Vibration transmitted from the road surface is mitigated by the softer first reinforcing layer 80 to enhance the damping effect, and cracks, heat generation and heat accumulation are less likely to occur on the inner surface of the sidewall of the tire while avoiding local stress concentration. .

A method for forming a laminated structure as the reinforcing rubber layer 8 is, for example, Japanese Patent Application Laid-Open No. 200 by the applicant.
No. 1-179848 and Japanese Patent Application No. 2000-38001
The method of winding a rubber strip, which is disclosed in No. 8, can be adopted. Although the thickness of each reinforcing layer is not limited to a specific numerical value, the thickness of the reinforcing layer having a softer hardness in the tire radial direction is preferably 2 to 10 mm. If it is less than 2 mm, the vibration cannot be effectively damped, and 10
This is because if the thickness is equal to or larger than mm, it tends to be difficult to suppress the deflection of the tire.

Further, in the tread portion 2, a belt layer 7 is provided just outside the carcass layer 6 in the tire radial direction, and the first belt ply 7a on the inner side in the radial direction and the first belt ply 7a. It has the 2nd belt ply 7b arranged on the outside so that it may be piled up. Each belt ply 7a,
7b is, for example, a steel cord arranged at an angle of 15 ° to 35 ° with respect to the tire equator line C. The arrangement of the cords on the first belt ply 7a and the arrangement of the cords on the second belt ply 7b are
They are designed to cross each other.

[0019]

EXAMPLES Next, a sensory test was conducted in order to confirm the effect of the run flat tire according to the present invention. The tire used is 215 / 45ZR17.

As the run-flat running conditions, the tire internal pressure was 0 kg / cm ² , the load acting on the tire was 470 kg, and the mounting conditions of the examples and the comparative examples were constant. These tires were subjected to a running test at a speed of 80 Km / h on a drum having a drum diameter of 1.7 m and a camber angle of 0 °, and the running distance until damage due to cracks or the like was generated in the upper region of the sidewall was measured. This was done by indexing. The conventional tire is set to 100, and the larger the index, the better. The test results are shown in Table 1.

[0021]

[Table 1] In this table, Comparative Example 1 is a run-flat tire having a reinforced rubber layer formed of one kind of rubber as shown in FIG. In Comparative Example 2, the reinforcing rubber layer is formed of two types of rubber, but the boundary between rubber and rubber is one, and the structure is not such that they are alternately laminated. The example is a run-flat tire having a configuration according to the present invention. Comparative Example 2 has slightly improved riding comfort as compared with Comparative Example 1, but is rather inferior in durability. On the other hand, in the case of the example, it can be seen that the durability and the riding comfort are improved as compared with the prior art. The effect of the runflat tire according to the present invention can be confirmed also from the result of this experiment. Other Embodiments Regarding the laminated structure of the reinforcing rubber layer 8, various modified examples are possible. In the example of FIG. 1, the boundary line between the rubbers of the reinforcing layer is nearly horizontal, but the boundary line may be inclined as shown in FIG. Further, the thickness of each reinforcing layer can be appropriately set.

In the present embodiment, the reinforcing rubber layer has a two-layer structure of the first reinforcing layer and the second reinforcing layer, but the hardness of the rubber may be three or more and may be a laminated structure of three or more layers. .

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a run flat tire.

FIG. 2 is a cross-sectional view showing the structure of a run flat tire according to another embodiment.

FIG. 3 is a cross-sectional view showing a structure of a run flat tire according to a conventional technique.

[Explanation of symbols]

1 run flat tire 2 tread section 3 Side wall part 8 Reinforced rubber layer 80 First reinforcement layer 81 Second reinforcing layer A tire radial direction

Claims (2)

[Claims] 1. A run-flat tire having a reinforcing rubber layer on the inner side of the sidewall portion in the tire axial direction, wherein the reinforcing rubber layer has at least a first hardness along the tire radial direction. A run-flat tire comprising a plurality of reinforcing layers, which include a layer and a second reinforcing layer having a second hardness, alternately stacked. 2. The rubber of the first reinforcing layer is a durometer A
The run flat tire according to claim 1, wherein the hardness of the second reinforcing layer is 45 to 65 degrees, and the rubber of the second reinforcing layer has a durometer A hardness of 65 to 85 degrees.