JP2009119994A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire in which an outer blemish-proof property at a tire side part is improved without sacrificing rotating resistance of the tire. <P>SOLUTION: The pneumatic tire has sidewalls having a double-layer structure composed of an outer layer and an inner layer of different rubber quality, has a durometer hardness (HD) at the outer layer of the sidewalls higher than that of the inner layer by 15 or more, and a loss elastic modulus (E") higher by three times or more. Preferably, the outer layer of the sidewall has a thickness of not smaller than 0.3 mm and not larger than 20% of the total thickness. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more specifically, the sidewall portion that covers and protects the side surface of the carcass has a two-layer structure in which the outer layer and the inner layer have different rubber properties without sacrificing the rolling resistance of the tire. The present invention relates to a pneumatic tire having improved resistance to trauma in a tire side portion.

  In recent years, as the speed of vehicles has increased, the demand for higher performance of pneumatic tires has also increased. The durability against accidental injuries during use of tires (trauma resistance) is important for safe use of tires. This is an important performance. Further, the reduction of tire rolling resistance (RR) can contribute to the reduction of fuel consumption of a vehicle equipped with a tire, leading to saving of earth resources.

In order to improve the damage resistance of tires, it is necessary to apply hard and highly exothermic rubber to repel impact and diffuse with heat, but when applied to side rubber, rolling resistance will be high There is a problem in the point.
On the other hand, the application of rubber with low heat generation is effective for reducing the rolling resistance of tires, but the low heat generation prevents thermal diffusion of the impact, resulting in a decrease in durability against the impact on the side rubber part. Become.
This balance between rolling resistance and resistance to trauma is a trade-off, making it difficult to achieve with a single layer of side rubber.

  Conventionally, many structures have been known for pneumatic tires in which the sidewall portion has different rubber properties between the outer layer and the inner layer. For example, 1) physical properties are different in each rubber composition of the inner layer and the outer layer. Pneumatic tires with improved side appearance in which anti-aging agents are blended to prevent discoloration (see, for example, Patent Document 1), 2) Inner layer and outer layer (two layers), or each of three layers of sidewall portions A pneumatic tire in which petroleum paraffin wax having different physical properties is blended in the rubber composition and the static ozone resistance is improved over a long period of time without impairing the aesthetics of the sidewall portion (for example, Patent Documents 2 and 3) 3) A pneumatic tire excellent in handling stability, in which the flatness is 55% or less and the elastic modulus of the rubber of the inner side wall portion is larger than that of the rubber of the outer side wall portion. For example, see Patent Document 4), 4) The outer layer rubber is compounded with syndiotactic-1,2-polybutadiene having a specific amount of melting point, and the outer layer rubber hardness (HA) and the inner layer rubber. A pneumatic tire (see, for example, Patent Document 5) characterized in that the ratio (HA / HB) to hardness (HB) satisfies the relationship represented by 1 <HA / HB <1.25. Yes.

  5) Run-flat durability in which each side wall has a rubber layer in which two layers of hard and soft layers are formed on the outer side and the inner side of the tire, and the outer rubber layer is made of the same rubber as the tread rubber. Excellent pneumatic tire (see, for example, Patent Document 6), 6) In the side rubber disposed in the sidewall portion, the ratio (η) of the circumferential modulus to the radial modulus of the rubber layer in the side was seen in the tire radial direction. A pneumatic tire characterized in that it is sometimes larger in the vicinity of the tire maximum value than at least one of the bead core side and the tread rubber side (see, for example, Patent Document 7), 7) Of the side rubbers arranged in the sidewall portion, The outer side in the radial direction from the vicinity of the maximum width of the tire is made of rubber that is the same quality as the tread rubber. Pneumatic radial tires for urban running buses, characterized in that at least the region reaching the vicinity of the maximum tire width is covered with rubber having specific physical properties (see, for example, Patent Document 8), 8) Each of the outer layer and the outer layer Using rubber compositions containing low and high unsaturation rubbers with different blending amounts as rubber compositions, both the appearance of the side part and ozone crack resistance are kept in good condition. A sagging pneumatic tire (see, for example, Patent Document 9) is known.

However, a pneumatic tire having a multilayer structure with two or more sidewall portions described in these documents is intended for appearance of the side portion, ozone crack resistance, durability, etc. There is no description or suggestion of a pneumatic tire technology for the purpose of improving both the resistance to trauma.
JP 63-112636 A (Claims, Examples, etc.) Japanese Patent Laid-Open No. 04-108007 (Claims, Examples, etc.) JP 04-108008 (Claims, Examples, etc.) Japanese Patent Laid-Open No. 06-227214 (Claims, Examples, etc.) Japanese Patent Laid-Open No. 06-328912 (Claims, Examples, etc.) Japanese Patent Laid-Open No. 06-344729 (Claims, Examples, etc.) JP-A-08-188018 (Claims, Examples, etc.) JP 09-86107 A (Claims, Examples, etc.) JP-A-10-35212 (Claims, Examples, etc.)

  The present invention has been made in order to solve the above-described problems and the current state of the prior art, and has been made to solve this problem.Pneumatic having improved trauma resistance of the tire side portion without sacrificing rolling resistance of the tire. The object is to provide a tire.

  As a result of intensive studies in order to solve the above-described conventional problems, the inventor of the present invention has a trauma resistance in a pneumatic tire having a two-layer structure in which the side wall portion is different in the outer layer and the inner layer. In order to improve, it is effective to repel impacts and diffuse with heat, and to find that heat generation is effective to reduce rolling resistance. By placing rubber with high trauma resistance on the outer layer of the part and placing rubber with high rolling resistance reduction effect on the inner layer of the side wall part, the above-mentioned pneumatic tire was successfully obtained, and the present invention was achieved. It has been completed.

That is, the present invention resides in the following (1) to (4).
(1) A pneumatic tire having a two-layer structure in which the sidewall portion has different rubber properties between the outer layer and the inner layer, wherein the outer layer of the sidewall portion has a durometer hardness (HD) of 15 or more higher than that of the inner layer, and A pneumatic tire characterized by having a loss elastic modulus (E ″) three times higher.
(2) The pneumatic according to (1), wherein the outer layer of the sidewall portion has a thickness of 0.3 mm or more in the width direction or the thickness direction and is 20% or less of the total thickness of the sidewall portion. tire.
(3) The pneumatic tire according to (1) or (2), wherein the outer layer of the sidewall portion includes 65 parts by mass or more and 85 parts by mass or less of carbon black with respect to 100 parts by mass of the rubber component.
(4) The pneumatic according to any one of (1) to (3), wherein the inner layer of the sidewall portion includes 30 parts by mass or more and 60 parts by mass or less of carbon black with respect to 100 parts by mass of the rubber component. tire.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire excellent in reduction of trauma resistance and rolling resistance (low heat generation) is provided.

Hereinafter, embodiments of the present invention will be described in detail.
The pneumatic tire according to the present invention is a pneumatic tire having a two-layer structure in which the sidewall portion has different rubber properties between the outer layer and the inner layer, and the outer layer of the sidewall portion has a durometer hardness (HD) with respect to the inner layer. It is characterized by being 15 or more and having a loss modulus (E ″) three or more times higher.
The pneumatic tire of the present invention is not particularly limited as long as the sidewall portion has a two-layer structure in which the outer layer and the inner layer have different rubber properties. For example, a pair of left and right bead rings , At least one carcass layer connected from one of the bead portions to the other, a reinforcing belt and a tread portion disposed on the outer side in the tire radial direction of the carcass layer, and a pair disposed on the left and right of the tread portion And a pneumatic tire provided with an inner liner layer located inside the carcass layer.

In the present invention, the rubber layer of the sidewall portion is composed of a rubber layer having a two-layer structure in which the outer layer and the inner layer are different in rubber quality, and a rubber having a high trauma resistance is disposed on the outer layer and rolled to the inner layer. A rubber having a high resistance reducing effect is arranged.
Specifically, it is necessary that the outer layer rubber of the sidewall portion is set to have a durometer hardness (HD) of 15 or more higher than that of the inner layer rubber and a loss elastic modulus (E ″) of three or more times higher. Preferably, the outer layer rubber has a durometer hardness (HD) of 20 or more, more preferably 20 to 25, and the loss elastic modulus (E ″) is 10 times or more, more preferably, the inner layer rubber. It is desirable to set to 10-15.

  In the outer layer where the durometer hardness (HD) is less than 15, the damage resistance becomes insufficient, and when the outer layer whose loss elastic modulus (E ″) is less than 3 times is used, the damage resistance becomes insufficient. It is not preferable.

In the present invention, the thickness of the outer layer in the tire width direction (thickness direction) is preferably 0.3 mm or more, more preferably 0.4 to 1.0 mm, The thickness of the tire sidewall portion is preferably 20% or less compared to the thickness in the tire width direction, more preferably 15 to 20%.
When the thickness of the outer layer in the tire width direction is less than 0.3 mm, it may be difficult to ensure the stability of the member in the manufacturing process, and when the thickness of the tire sidewall portion exceeds 20% compared to the thickness in the tire width direction. As a result, the rolling resistance is increased.

In order to set the outer layer of the sidewall portion to have a durometer hardness (HD) of 15 or more higher than that of the inner layer and a loss elastic modulus (E ″) of 3 times or more higher, a rubber composition having a different composition is used. It can be implemented by laminating.
As a blend, the rubber composition constituting the outer layer of the sidewall portion is preferably 65 parts by weight or more and 85 parts by weight or less, and more preferably, with respect to 100 parts by weight of the rubber component. The carbon black is desirably 70 parts by mass or more. By adding carbon black within this range, the loss elastic modulus (E ″) increases, and the resistance to external damage can be improved.
The rubber composition constituting the inner layer of the sidewall part is preferably 30 parts by mass or more and 60 parts by mass or less, more preferably 20 parts by mass of carbon black (CB) with respect to 100 parts by mass of the rubber component. It is desirable to set it to -40 mass parts. By blending carbon black within this range, the loss elastic modulus (E ″) is reduced, and the rolling resistance can be reduced.

  In the present invention, as the rubber component constituting the sidewall portion, it is possible to use a simple substance such as natural rubber, synthetic polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber or other diene rubber, or a mixture thereof. In addition, inorganic fillers such as silica, softeners such as aroma oil and spindle oil, anti-aging agents, vulcanizing agents, vulcanization accelerators, vulcanization acceleration aids, and usually blended as necessary. An appropriate amount of a rubber compounding agent or the like can be appropriately blended.

In the pneumatic tire of the present invention configured as described above, the outer layer of the sidewall portion has a hardness (HD) 15 or more higher than that of the inner layer, and the loss elastic modulus (E ″) is three times or more. The input is repelled by its high hardness against the input that causes trauma, and the input is diffused as heat by the loss elastic modulus (E ″), which improves the trauma resistance and the loss elastic modulus (E ″). The tire rolling resistance of the tire sidewall is not sacrificed by using the low-risk tire sidewall portion as the inner layer portion of the city oil male.
Therefore, in the pneumatic tire of the present invention, a pneumatic tire excellent in damage resistance and rolling resistance reduction (low heat generation) can be obtained.

In particular, the outer layer of the sidewall portion has a thickness of 0.3 mm or more in the width direction or thickness direction, and is 20% or less of the total thickness of the sidewall portion. It can be a pneumatic tire that is highly compatible with reduction of resistance (low heat generation).
In addition, the pneumatic tire of this invention is not limited to the said embodiment, In the range which does not change the summary of this invention, it can change variously.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to the following Example.

[Examples 1-2 and Comparative Examples 1-3]
Table 1 below shows each compounding composition (compounding AD) of the rubber composition used for the sidewall portion (outer layer, inner layer).
Table 2 below shows each rubber composition (compounding A to D) used for the sidewall portion (outer layer, inner layer), each thickness, thickness ratio, durometer hardness (HD) difference, carbon black (CB). Indicates the amount.

Sidewall (outer layer, inner layer) rubber was produced using these rubber compositions, and each tire (205 / 65R159H) was made as a prototype. The total thickness of the side rubber was 2.5 mm, and the outer layer of the sidewall part was a tire having a desired thickness extruded and affixed to the inner layer.
The durometer hardness (HD) and the loss modulus (E ″) were measured by the following measurement method using a sample cut from a tire. For the sample carried out with a thickness of 2 mm or less, the rubber Was cut out from a tire using a thickness of 2 cm, and the results are shown in Table 1 below.
Moreover, the rolling resistance (RR) and the trauma resistance of each prototype pneumatic tire were evaluated by the following evaluation methods. These results are shown in Table 2 below.

[Durometer hardness (HD) measurement method]
It was measured by Durometer Hardness TYPE A (ASTM D 2240 JIS K 7215, JIS K 6253) manufactured by Kobunshi Keiki Co., Ltd., and the hardness difference between the outer layer and the inner layer was calculated.
[Measurement method of loss elastic modulus (E ")]
Using a VR-7100 manufactured by Ueshima Seisakusho Co., Ltd., the initial strain was 600 micrometers, the frequency was 52 Hz, 24 ° C., and the measurement strain was 1%, and the difference in loss elastic modulus (E ″) between the outer layer and the inner layer was calculated.

[Evaluation method of rolling resistance]
Measurement was performed at an air pressure of 200 kPa, a speed of 80 km / h, and a load of 4.8 kN.
[Method for evaluating trauma resistance]
The number of traumas (2 mm or more) on the tire side after 50,000 Km of actual running was counted, and the tire of Comparative Example 1 was displayed as an index with 100 as the index. In addition, the larger the index, the better the trauma resistance and the smaller the number of traumas.

  As is clear from the results of Tables 1 and 2, the pneumatic tires of Examples 1 and 2 that are within the scope of the present invention are reduced in rolling resistance as compared with Comparative Examples 1 to 3 that are outside the scope of the present invention. It was found that the damage resistance can be greatly improved.

  Since the pneumatic tire of the present invention reinforces the sidewall portion of the tire, and has excellent fuel efficiency and damage resistance, both of which have high industrial utility value.

Claims (4)

  A pneumatic tire having a two-layer structure in which the sidewall portion has different rubber properties between the outer layer and the inner layer, and the outer layer of the sidewall portion has a durometer hardness (HD) of 15 or more higher than the inner layer, and loss elasticity A pneumatic tire characterized in that the rate (E ") is three times higher.   The pneumatic tire according to claim 1, wherein the outer layer of the sidewall portion has a thickness of 0.3 mm or more in the width direction or the thickness direction and is 20% or less of the total thickness of the sidewall portion.   The pneumatic tire according to claim 1 or 2, wherein the outer layer of the sidewall portion contains 65 parts by mass or more and 85 parts by mass or less of carbon black with respect to 100 parts by mass of the rubber component.   The pneumatic tire according to any one of claims 1 to 3, wherein the inner layer of the sidewall portion includes 30 to 60 parts by mass of carbon black with respect to 100 parts by mass of the rubber component.