JP3168442B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of reducing the weight of a sidewall portion without deteriorating trauma resistance and crack resistance.

[0002]

2. Description of the Related Art As measures for preserving the earth's environment against global warming caused by carbon dioxide in recent years, further reduction in fuel consumption of automobiles is required, and as one of the measures, reduction in weight of pneumatic tires is strongly demanded. As a measure for reducing the weight of the pneumatic tire, there is a reduction in the amount of rubber by making the sidewall portion thinner. However, simply reducing the thickness of the side wall portion reduces the impact energy dispersion performance of the side wall portion, so if the vehicle collides with a curb when traveling or receives an impact on a rough road due to a stone or a sharp protrusion or the like. It is easily damaged. Further, when the tire undergoes bending deformation or shearing deformation due to ground contact rotation, deformation distortion of the sidewall portion increases, fatigue resistance deteriorates, and crack resistance also deteriorates.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic tire which can be reduced in weight without deteriorating trauma resistance and crack resistance, which are the essential characteristics of a sidewall portion. It is in.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to form a sidewall portion having two layers, an inner layer and an outer layer, and forming the outer layer of a rubber compounded with short fibers, and forming the inner layer of a polymer compound. This can be achieved by constituting the film with a main component. In this way, by forming the side wall portion into two layers and forming the outer layer thereof from a rubber compounded with short fibers, the side wall portion has improved scratch resistance and crack resistance. Further, by providing a polymer compound film as the inner layer, the tensile strength is improved as compared with the rubber layer of the blank, and the entire sidewall portion can be made thinner, so that the weight of the tire can be reduced.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment in the case of the pneumatic radial tire of the present invention. In the figure, 1 is a tread portion, 2 is a sidewall portion, and 5 is a bead portion. Carcass layer 3
Are folded back around the right and left bead cores 4 so as to wrap the bead filler 6 from the inside to the outside of the tire.
The belt layers 7 are arranged so as to cross each other at a cord angle of 15 to 35 ° with respect to the tire circumferential direction. The side wall portion 2 is composed of two layers, an outer layer 2a and an inner layer 2b. Of these, the outer layer 2a is composed of rubber mixed with short fibers, and the inner layer 2b is composed of a polymer compound film.

[0006] The pneumatic tire of the above construction has a high impact resistance when hitting a curb because the outer layer 2a of the sidewall portion 2 is made of short fiber-containing rubber, and has a high trauma resistance. . In addition, since it exhibits high fatigue resistance against bending strain during tire contact rotation, crack resistance is improved. In addition, since a film of a polymer compound is provided in the inner layer 2b, the sidewall portion 2 can be made thinner by its reinforcing effect. The bending of the sidewall portion 2 when the tire rotates on the ground, the vicinity of the carcass layer 3 is the central axis of the bending, and the strain increases toward the outside of the tire. Therefore, the short fiber-containing rubber is used as the outer layer 2a. The arrangement in which the film of the high molecular compound is used as the inner layer 2b makes it possible to reduce the weight most efficiently while obtaining the scratch resistance and the crack resistance. In addition, by providing a film having relatively small elongation as compared to rubber on the inner side, stress concentration on the bonding interface between the inner and outer layers can be reduced and separation can be suppressed.

In the present invention, the short fibers blended in the outer layer are oriented in the circumferential direction of the tire, whereby the rigidity in the circumferential direction of the tire is remarkably increased, and the scratch resistance can be further increased. The amount of the short fibers is preferably 0.5 to 10 parts by weight per 100 parts by weight of rubber. The reinforcing effect is remarkably improved by adding 0.5 parts by weight or more. However, if the compounding amount of the short fibers exceeds 10 parts by weight per 100 parts by weight of the rubber, the processability of the rubber composition decreases.

The short fiber used in the present invention preferably has an average diameter (d) of 15 μm or less. Here, the average diameter (d) of short fibers refers to a value obtained by randomly sampling 20 short fibers before blending with rubber and calculating the arithmetic average of the measured values. Further, the fiber length (L) of the short fibers is such that the ratio L / d to the average diameter (d) is 1
It is desirable to be 5 or more. By setting the fiber length (L) to 15 or more as L / d, the reinforcing effect on rubber can be further improved.

The types of short fibers used in the present invention include:
There is no particular limitation, but synthetic fibers such as vinylon, nylon, polyester, aromatic polyamide (aramid) and wholly aromatic polyester, and organic fibers such as chemical fibers such as rayon, carbon fibers, glass fibers, potassium titanate, and the like. Examples thereof include inorganic fibers such as whiskers obtained from silicon carbide, phosphate, and the like. Preferably the melting point is 1
Fibers of 60 ° C. or higher are preferred. When the melting point is 160 ° C. or more, the reinforcing effect can be maintained by preventing melting and thermal deterioration due to heat generated during tire running.

The type of film used in the present invention includes polyethylene, preferably ultrahigh molecular weight polyethylene having a molecular weight of 1,000,000 or more, 6 nylon, 66 nylon,
Examples thereof include those prepared from high molecular compounds such as aliphatic polyamides such as 12 nylon, aromatic polyamides, polyesters, and polyvinylidene chloride alone or a mixture of two or more thereof. These films may be obtained by laminating different kinds of films in two or more layers. For example, a laminated film of a polyvinylidene chloride-based unstretched film and a polypropylene film may be used.

In the present invention, the film preferably has a tensile modulus of 100 to 1500 kgf / mm ² and a thickness of 50 to 500 μm. By increasing the tensile modulus to 100 kgf / mm ² or more, the effect of increasing the rigidity in the circumferential direction of the sidewall portion is increased, and the side wall portion is improved in trauma resistance and crack resistance, and the weight is reduced by thinning. Can be done. Even if the tensile modulus is too large, the stress tends to concentrate on the bonding interface between the outer layer and the rubber, which causes separation, so that it is preferable to limit the tensile modulus to 1500 kgf / mm ² . The tensile modulus of such a film is
By forming slits or cuts in the film, the average tensile modulus may be adjusted to be in the above range.

On the other hand, by setting the thickness of the film to 50 μm or more, the effect of the sidewall portion in the tire circumferential direction is increased, and the weight can be reduced. When the film is too thick, separation with the outer layer is apt to occur.

[0013]

EXAMPLE The tire has a radial structure of 175 / 70SR13 in common, and has a radial structure in which the structure of the sidewall, the type of rubber composition, the type of film, the thickness, etc. are different as shown in Table 1. Invention Tires 1-4
In addition, conventional tires and comparative tires were manufactured.

The film of the tire 3 of the present invention has a width of 15 m in the width direction of the nylon film of the tire 1 of the present invention.
Three slits with a length of 4 mm intermittently provided at intervals of 6 mm along the longitudinal direction of three rows at m intervals were used, and the slit directions were aligned with the tire circumferential direction. With respect to these six types of pneumatic tires, the following methods were used to evaluate the scratch resistance, crack resistance and weight reduction. The results were as shown in Table 1.

[0015] Trauma resistance : Each test tire was rim 13 x 5
Assemble the rim of J, fill it with air pressure of 2.0 kg / cm ² and attach it to the vehicle. Height = 110 mm, width = 100
mm at a 30 ° approach angle to a vertically steep curb, first climbing at a speed of 10 km / hr, then increasing the speed by 2 km / hr, riding on the curb in the same way, and cutting into the side wall The speed V when the burst occurred was measured. The measurement results are average values of two test tires.

The evaluation value is represented by an index using the reciprocal of the average value of the conventional tire as a reference (100). The larger the index is, the lower the trauma resistance is. Crack resistance : For each test tire, an ozone spray drum test was performed, and the presence or absence of ozone cracks in the side wall was visually compared. Light weight property : The weight of each test tire was measured and indicated by an index based on the weight of a conventional tire (100). The greater the value, the greater the tire weight.

[0017]

Note: In Table 1 above, the specifications of the rubber compositions A, B, C and D are as shown in Table 2, respectively. Nylon indicates a film made of nylon 6. Aramid indicates a film composed of an aromatic polyamide. The tensile modulus is a value measured according to the method specified in JIS-6301. * 1 indicates an average tensile modulus.

[0019] Note: All numerical values in Table 2 above indicate parts by weight.

¹⁾ High cis polybutadiene “Nipol 1220” manufactured by Zeon Corporation ²⁾ N-phenyl-N′-isopropyl-p-phenylenediamine ³⁾ microcrystalline wax ⁴⁾ dibenzothiazyl sulfide ⁵⁾ average diameter 7 μm, average fiber Length 6 mm ⁶⁾ Average diameter 0.3 μm, average fiber length 30 μm ⁷⁾ Average diameter 12 μm, average fiber length 1500 μm (manufactured by Monsanto Japan Co., Ltd.) From Table 1, the tires 1, 2, 3, and 4 of the present invention are all conventional tires. Compared with the above, the scratch resistance and crack resistance are improved and the weight is reduced. On the other hand, the comparative tire has improved scratch resistance as compared with the conventional tire, but has no change in crack resistance and is not reduced in weight.

[0021]

According to the present invention, the sidewall portion is made up of two inner and outer layers, the outer layer is made of rubber containing short fibers, and the inner layer is made of a polymer compound film. The required characteristics such as cracking properties can be improved, and the weight of the tire can be reduced.

[Brief description of the drawings]

FIG. 1 is a half sectional view showing a pneumatic radial tire according to an embodiment of the present invention.

[Explanation of symbols]

2 Side wall 2a Outer layer (short fiber-containing rubber) 2b Inner layer (polymer compound film)

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masao Inoue 2-1 Oiwake, Hiratsuka-shi, Kanagawa Yokohama Rubber Co., Ltd. Hiratsuka Works (56) References JP-A-3-292205 (JP, A) JP-A-4 JP-A-4-159109 (JP, A) JP-A-4-274908 (JP, A) JP-A-57-104405 (JP, A) JP-A-4-260802 (JP, A) JP-A-4-260803 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 13/00 B60C 1/00

Claims (1)

(57) [Claims] 1. A pneumatic tire in which a sidewall portion is composed of two inner and outer layers, an outer layer of which is composed of rubber mixed with short fibers, and wherein the inner layer is composed of a film containing a polymer compound as a main component.