JP2702862B2 - Heavy duty 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 heavy-duty tire capable of preventing the occurrence of cracks on the outer surface of a sidewall portion while suppressing the deterioration of appearance and achieving a longer life of the tire.

[0002]

2. Description of the Related Art In general, natural rubber (NR) and butadiene rubber (BR),
An unsaturated diene-based synthetic rubber such as styrene-butadiene rubber (SBR) is used. Since this product contains a double bond in the main chain, it is easily vulcanized with sulfur and exhibits excellent flexibility and cut resistance, but it degrades by reacting with oxygen and ozone in the air. There is a problem that it is easy.

[0003] In particular, the sidewall portion of a heavy-duty tire having a large burden load has a large amount of flexure when the tire is repeatedly deformed while the tire is in contact with the ground or not, and in combination with the above-mentioned deterioration, cracks are caused at an early stage. It was the main cause of shortening the overall tire life including rehabilitation.

[0004]

Accordingly, in order to prevent such deterioration, it has heretofore been practiced to partially incorporate an amine-based antioxidant into the sidewall rubber.

[0005] However, since this kind of anti-aging agent is compounded over the entire sidewall rubber, the inhibitor is deposited on the outer surface of the sidewall over a wide range from the early stage of use, and stains are formed by oxidation or the like. The tire appearance is impaired, such as the generation of brown discoloration, and the commercial value is reduced.

[0006] As described above, there is an incompatible relationship between the appearance and the crack resistance of the sidewall portion, and the appearance of a tire that can sufficiently satisfy both performances has been strongly desired.

The present invention is based on the fact that a sidewall rubber is divided into three regions, upper, middle and lower, and a weather resistant rubber composition containing an antioxidant is used in the upper and lower regions. It is an object of the present invention to provide a heavy-duty tire capable of effectively preventing the occurrence of crack damage in a part and suppressing a reduction in appearance.

[0008]

In order to achieve the above object, a heavy-duty tire according to the present invention is characterized in that a side portion forming an outer surface of a side wall portion extending from a flange height position of a regular rim on which a bead portion is seated to a tread end is provided. The wall rubber is applied to the tire at a section height H of about 0.18 to 0.25 from the tread end.
And a distance L2 that is approximately 0.27 to 0.33 times the tire cross-sectional height H from the flange height position to the region above the double distance L1 inward in the tire radial direction. While dividing into a lower region to a position separated upward and a middle region between the lower region and the upper region,
The upper and lower regions are 3 to 6 parts by weight Xa of the amine antioxidant, 35 to 50 parts by weight Za of carbon black, and 35 parts by weight Y of sulfur contained in 100 parts by weight of rubber.
a is 0.5 to 2, and the intermediate region is such that the weight part Zb of carbon black contained in 100 weight parts of rubber is larger than the weight part Za, and the weight of sulfur is 100 weight parts of rubber. A non-weather-resistant rubber composition in which the part Yb is larger than the above-mentioned part by weight Ya and the part by weight Xb of the amine antioxidant is smaller than the above-mentioned part by weight Xa.

[0009]

The sidewall rubber is provided in an upper region Y1 from the tread end Te to a position spaced apart from the tire sectional height H by a distance L of about 0.18 to 0.25 times inward in the tire radial direction,
Approximately 0.2 of the tire section height H from the flange top height position
A region Y2 below a distance L2 that is 7 to 0.33 times the distance L2 above in the tire radial direction, and these regions Y1, Y2
It is divided into an intermediate area Y3 between them. As a result of the study of the present inventor, of these three regions, the upper and lower regions Y1,
It has been found that Y2 is the portion that undergoes the greatest repeated deformation during rolling of the tire and is liable to cause crack damage such as cracks due to rubber deterioration.

That is, as shown in FIG. 2, tensile stress (+) is generated in the upper and lower regions Y1 and Y2 when the internal pressure is charged, and compressive strain (-) is generated under load (at the time of grounding). Is generated, and a large repeating stress acts due to the rolling of the tire. On the other hand, the middle area Y
In No. 3, almost no repetitive stress acts on the rolling of the tire, for example, the strain is almost constant.

Therefore, a weather-resistant rubber composition is used in the upper and lower regions. The weatherable rubber composition has a carbon black content of 50 parts by weight or less and a sulfur content of 2 parts by weight or less, and its viscosity is increased while reducing the rubber hardness as compared with the conventional side wall rubber. To relax. Moreover, since the anti-aging agent is added in an amount of 3 parts by weight or more, the occurrence of deterioration such as oxidation can be suppressed for a long period of time, and crack damage in the sidewall portion can be effectively prevented. Further, since the repeated stress hardly acts on the intermediate region Y3, the region Y3
Even when a non-weatherproof rubber composition similar to the conventional sidewall rubber is adopted, the effect of preventing crack damage can be maintained,
Moreover, an increase in tire cost can be reduced.

Regarding the appearance of the tire, since the outer surface of the sidewall is subdivided into three regions Y1, Y2, and Y3, even when the antioxidant is deposited on the upper and lower regions Y1 and Y2, the discoloration of the antiaging agent is prevented. Impression degree can be kept low.
Moreover, the discoloration can eliminate irregularities in the discoloration, such as the appearance of three band-like pattern patterns on the outer surface of the side wall, thereby reducing discomfort. Further, since the conspicuous intermediate region Y3 is formed of a black rubber composition without discoloration by protruding greatly to the side, the appearance can be maintained comprehensively and a decrease in commercial value can be suppressed.

[0013]

An embodiment of the present invention will be described below with reference to the drawings. In the drawing, the heavy duty tire has bead portions 3 on both sides through which the bead core 2 passes, a sidewall portion 4 extending upward in the tire radial direction from each bead portion 3, and a tread portion 5 connecting the upper ends thereof. Tire size is 1
A truck and bus tires of 0.00R20, each bead portion 3 is seated in a normal rim R. The heavy load tire 1 is provided with a carcass 6 extending between the bead portions 3 and a belt layer 7 disposed radially above the carcass 6 and inside the tread portion. In addition, regular
Rim means a rim specified in JIS in this specification
I do.

The carcass 6 is made of nylon, rayon,
Polyester, organic fiber such as aromatic polyamide, or at least one or more carcass cords composed of steel fibers arranged at an angle of 70 to 90 degrees with respect to the tire equator C, in this example, two carcass plies, The carcass ply has bead cores 2 at both ends of a main body 6A extending from the tread portion 5 to the bead core 2 through the sidewall portion 4.
A turn-back portion 6B is provided to turn the area around from inside to outside.
Further, a tapered bead apex rubber 9 extending upward in the tire radial direction from the bead core 2 beyond the upper end of the folded portion 6B is disposed between the main body 6A and the folded portion 6B of the carcass 6, and from the bead portion 3 Side wall part 4
And strengthen the tires.

The bead portion 3 is provided with a hard clinch apex rubber 10 which rises from the bottom of the bead and covers the outer surface of the folded portion 6B of the carcass, thereby preventing the bead from being damaged due to rim misalignment.

The first, second, third, and fourth belt plies 7a, 7b, 7b, 7c, and 7d are arranged in order from the carcass side to at least one in the present embodiment.
7c and 7d. Each belt ply 7a-7d
Has a belt cord made of steel arranged at an angle of 10 to 70 degrees with respect to the tire equator C, and the belt layer 7 has a maximum ply width BW of 0.
By setting the ratio to 7 to 0.95, the tread portion 5 is reinforced over the entire width thereof with a hammer effect.

The outer surface (tread surface) of the tread surface 5 is formed of an arc centered on the tire equatorial plane, and the belt layer 7 extends substantially parallel to the tread surface. Separate. The separated portion is filled with a soft cushion rubber 11 to reduce the shearing force concentrated on the belt end and suppress the separation.

In the present invention, the sidewall rubber 12 forming the outer surface of the sidewall portion 4 is divided into three regions, and a predetermined rubber composition is used in each region.

That is, the sidewall rubber 12 continues to the upper end of the clinch apex rubber 10 and extends upward in the tire radial direction in contact with the outer surface of the bead apex 9 and the outer surface of the carcass body 6A. 11 The taper ends at the tread end Te away from the outer surface.

The lower end of the sidewall rubber 12 is connected to the upper end of the clinch apex rubber 10 by a slope S inclined inward in the tire radial direction outward in the tire axial direction, and the lowest point of the slope S is The rim R is located at the flange height position K1.

That is, the sidewall rubber 12 extends from the flange height position K1 to the tread end Te, and the sidewall rubber 12 is about 0.18 to 0.25 times the tire sectional height H from the tread end Te. An area Y1 up to a position K2 that separates the distance L1 inward in the tire radial direction, and a distance L2 about 0.27 to 0.33 times the tire sectional height H from the flange height position K1 to the tire radius. Area Y2 below the position K3 separated upward in the direction, and these areas Y
1, and an intermediate area Y3 arranged between Y2.
Note that the above “about” is defined as a range of ± 10% or less of each of the distances L1 and L2.
1 and the intermediate area Y3, and the intermediate area Y3 and the lower area Y
2 and the overlapping portions V and W where they overlap each other in the tire axial direction.
Is allowed to form.

The upper and lower regions Y1 and Y2 are formed by the weather-resistant rubber composition M, and the intermediate region Y3 is formed by the non-weather-resistant rubber composition N.

The weather-resistant rubber composition M is a rubber base made of one or more selected from diene synthetic rubbers such as butadiene rubber (BR) and styrene-butadiene rubber (SBR) and natural rubber (NR). Antioxidant is 3 to 6 parts by weight Xa, carbon black is 35 to 50 parts by weight Za, and sulfur is 0.5 part by weight to 100 parts by weight of material.
To 2 parts by weight Ya, and other additives such as aromatic oil, zinc white and stearic acid vulcanization accelerator are added as required.

As described above, since the weatherable rubber composition M contains the antiaging agent in a high ratio of 3 parts by weight or more, the deterioration of the rubber is suppressed for a long time. Moreover, since carbon black and sulfur are reduced, the viscosity of the rubber can be increased and the hardness can be reduced, and the strain stress can be sufficiently reduced. When the amount of the antioxidant exceeds 6 parts by weight, the discoloration becomes excessive due to an increase in the amount of protrusion on the rubber surface, and the deterioration of appearance cannot be suppressed. When the carbon black and sulfur are less than 35 and 0.5 parts by weight, respectively, the necessary rubber elasticity is lost and the tire durability is reduced.

As the anti-aging agent, amine-based ones can be used. For example, N- (1,3-dimethylbutyl)-
N'-phenyl-P-phenylenediamine, N-isopropyl-N'-phenyl-P-phenylenediamine, diallyl-P-phenylenediamine, N- (1-methylheptyl) -N'-phenyl-P-phenylenediamine,
N- (1,3-dimethylbutyl) -N '-(4'-ethylphenyl) -P-phenylenediamine, N- (1,4
-Dimethylheptyl) -N'-phenyl-P-phenylenediamine, N- (1-methyldotesyl) -N'-phenyl-P-phenylenediamine, N- (1-methyloctadecyl) -N'-phenyl-P-phenylene Diamines and the like can be employed.

The non-weather-resistant rubber composition N is a standard rubber composition conventionally used for sidewall rubber of a tire, and is a carbon black part by weight based on 100 parts by weight of the rubber base material. Zb is the weight part Z
a, and the weight part Yb of sulfur is larger than the weight part Ya, and the weight part Xb of the antioxidant is smaller than the weight part Xa. Preferably the weight part Zb
Is 50 to 70, part by weight Xb is 0 to 3, part by weight Yb is 2 to
5, and the weight part Xb is more preferably 0. Since the intermediate region Y3 is a region where the repeated stress hardly acts as described above, the antiaging agent is removed and the progress to cracks and the like is suppressed even if the deterioration occurs. In addition, since it has a sufficient rubber hardness, it exhibits high cut resistance and can protect the tire from external damage. In addition, since it protrudes to the outside of the tire and presents black without discoloration in this most conspicuous area, it is useful for suppressing deterioration of appearance.

[0027]

As described above, since the heavy duty tire of the present invention is constituted, cracks on the outer surface of the sidewall portion due to rubber deterioration are prevented while suppressing deterioration in appearance, thereby extending the life of the tire. It can be.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation of the present invention.

[Explanation of symbols]

 Reference Signs List 3 bead portion 4 sidewall portion 12 sidewall rubber M weather-resistant rubber composition N non-weather-resistant rubber composition R area on regular rim Y1 area under Y2 area Y3 intermediate area

Claims (1)

(57) [Claims] 1. A sidewall rubber which forms an outer surface of a sidewall portion extending from a flange height position of a regular rim on which a bead portion is seated to a tread end is removed from the tread end by about 0.18-0 of a tire sectional height H. .25 times the distance L1 inward in the radial direction of the tire and about 0.27 of the tire sectional height H from the flange height position.
The distance L2 is divided into a lower region to a position separated upward by 0.33 times in the radial direction of the tire and an intermediate region between the lower region and the upper region. Are 3 to 6, parts by weight Xa of the amine antioxidant contained in 100 parts by weight of rubber, 35 to 50 parts by weight Za of carbon black, and 0.5 to 2 parts by weight Ya of sulfur. In the intermediate region, the weight part Zb of carbon black contained in 100 weight parts of rubber is larger than the weight part Za, and the weight part Yb of sulfur is more than the weight part Ya. A heavy duty tire formed of a large, non-weather-resistant rubber composition in which the weight part Xb of the amine antioxidant is smaller than the weight part Xa.