JPH04103405A - Radial tier for bad conditioned road - Google Patents

Abstract

PURPOSE:To improve envelope characteristics and prevent decrease in the radius of curvature of tread after a tire is used by making cross each other adjacent belt layer cords in different directions with respect to the equatorial plane of a tire, and providing slight angle difference to the belt cords in the same direction. CONSTITUTION:A radial tire for bad conditioned roads is provided with a carcass 7 composed of at least one layer of ply cord substantially radially arranged at an angle of 70-90 degrees with respect to the tire equatorial plane CO, and a belt layer composed of at least four (4) layers 11-14 of metal ply cord at an angle of 10-30 degrees with respect to the tire equatorial plane CO. In the belt layers 11-14, the first belt ply b1 cord from the carcass 7 side and the second belt ply b2 are set with the angle difference of 5-15 degrees in the same direction. The third belt ply b3 and fourth belt ply b4 cords are set similarly while they are arranged in the different direction to the first and second belt ply cords.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention improves the envelope characteristics related to cut resistance and cut penetration resistance, and the uneven wear resistance, and further improves the peel resistance of the steel belt end (BEL resistance). The present invention relates to a radial tire for use on rough roads that can reduce heat generation while maintaining the same properties as the above.

[Conventional technology]

Normally, in radial tires for rough roads, all steel belt cords are made small (usually 1
0 to 30°), and the cord directions of adjacent belt layers intersect in different directions with respect to the tire equatorial plane, so-called all low-angle belt structures that emphasize envelope characteristics are common. However, in such a belt structure, the hoop effect of the belt is insufficient, and the dimensional growth of the tire after running is large, resulting in a decrease in the cross-sectional tread radius of curvature TR in the meridian direction, which often causes uneven wear. Increase. Furthermore, since the cords of adjacent belts intersect at a relatively large angle, separation between the belts is likely to occur. Therefore, in order to prevent such peeling, it is common practice to thicken the rubber gauge between the cords at the end of the belt, but this increases the total thickness of the tire, resulting in increased heat generation in the tire, which reduces the total lifespan of the tire. ,
At the same time, the weight of the tires will increase.

[Problems to be Solved by the Invention] Therefore, the purpose of the present invention is to improve envelope characteristics and uneven wear resistance related to cut resistance and cut penetration resistance on rough roads, and to improve peel resistance (BE resistance) of steel belt ends.
The purpose of this project is to identify a belt structure for a radial tire for rough roads that can suppress tire heat generation, extend the tire's total life, and reduce the tire weight while maintaining the L performance.

[Means for Solving the Problems] The radial tire for rough roads of the present invention to achieve the above-mentioned object has at least one layer of ply cords forming a radial arrangement of 70' to 90 degrees with respect to the tire equatorial plane. In a radial tire for rough roads, the belt layer is mainly reinforced by a carcass having a carcass and a belt layer consisting of at least four layers of metal ply cords forming an angle of 10° to 30° with respect to the tire equatorial plane. The cord of the first belt ply b1 counting from and the cord of the second belt ply b
2 codes are in the same direction and the angle difference θ1 is 5° or more and 1
5" or less, the cord of the third belt ply b3 and the cord of the fourth belt ply b4 counting from the carcass side are in the same direction, and the angular difference θ2 is 5 layers or more and 15 degrees or less, and A radial tire for rough roads, which is arranged in a direction different from the first and second belt ply cords, and more preferably, the distance a2 between the cords in the radial direction of the belt end between the layers b2 and b3 is 2.5 mm. or more and 4.5 mm or less, and furthermore, a2, bl and b
Distance a1 between radial cords at belt end between 20 layers
l(a2/al) is 1.0 or more and 4.5 or less, and the ratio of a2 to the radial cord distance a3 at the end of the belt between layers b3 and b4 is 2(a2/al). a3
) is 10 or more and 4.5 or less.

First, the present inventor paid attention to the direction of the belt cord and discovered that performance changes significantly depending on its configuration. In other words, normally, the cords of adjacent belt layers intersect each other in different directions with respect to the tire's equatorial plane, and the belt layers are counted in order from the carcass side, and the belt cord direction is, for example, vertical with the tire's equatorial plane. , up to the right, up to the left, up to the right,
They have discovered that the envelope characteristics can be improved by changing the configuration of upward-leftward to upward-rightward, upward-rightward, upward-leftward, upward-leftward, or upward-leftward, upward-leftward, upward-rightward, upward-rightward configuration. However, as shown in Table 1, with the above belt configuration, the restraining force of the belt is weak, the tire size increases due to tire running, and the decrease in the tread curvature radius TR after running is even greater than that of a normal all-low angle tire. Therefore, wear resistance and uneven wear resistance are reduced. Therefore, the present inventor focused on creating a slight angle difference between the belt cords in the same direction as a method for preventing a decrease in the tread curvature radius TR after running while maintaining the improvement in envelope characteristics in the acid-held configuration. .

That is, by providing the angle difference θ as shown in Table 1, it is possible to prevent the tread radius of curvature TR from decreasing after the tire is running.

[For production]

The radial tire of the present invention prevents a decrease in the tread curvature radius TR after the tire runs by setting the bl and b2 belt cord angle difference θ1 and the b3 and b4 belt cord angle difference θ2 to 5 layers or more and 15 degrees or less. At the same time, the envelope characteristics can be improved. The above performance can be achieved when θ is 5° or more and 15° or less, but more preferably θ is 7″ or more and 13° or less. In other words, if θ is less than 5°, the It is not possible to prevent a decrease in the tread radius of curvature TR, and if θ exceeds 15°, no improvement in envelope characteristics can be expected.
With the above belt structure, BEL resistance performance can be improved compared to a normal all-low angle belt structure.

That is, since the cord angle difference θ between adjacent belt layers is relatively small, the BE resistance between bl and b2 and between b3 and 54 is
L performance is greatly improved. Therefore, the gauge between the belt cords at the belt end between the belt layers can be thinned, and as a result, the total thickness of the tire can be reduced, making it possible to reduce the heat generation and weight of the tire. In other words, r
Both l and r2 are 1. The above performance can be achieved when the ratio is 0 or more and 4.5 or less, but it is more preferably 1.3 or more and 4.2 or less. That is, if it is less than 1.0, the tire heat generation will be high, and if it exceeds 4.5, the temperature will increase between bl and b2 and b3.
The BEL resistance performance between and 54 deteriorates. Note that a2 is usually
2.5 mm or more and 4 in consideration of BEL resistance performance and heat generation.
．． A range of 5 mm or less is adopted.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings. In the figure, a radial tire 1 for rough roads has a bead portion 3 through which a bead core 2 passes, a sidewall 4 that is continuous with the bead portion 3 and extends outward in the tire radial direction, and a tread that connects the outer ends of the sidewall portion 4. It has part 5. Also, between the bead parts 3, 3, a carcass 7, which is made by folding the bead core 2 from the inside to the outside, is passed from the tread part 5 to the sidewall part 4 to the bead part 3 at both ends of the main body part 7A. At the same time, a belt layer 9 is wound on the radially outer side of the carcass 7 and the inner side of the tread portion 5 in the tire circumferential direction. The carcass 7 has a substantially radial structure consisting of one or more carcass plies in which carcass cords are arranged at an angle α of 70 to 90 degrees with respect to the tire equatorial plane. Incidentally, as the carcass cord, an organic or inorganic fiber cord is used, and in this example, a steel cord is used. Also, between the main body part 7A of the carcass 7 and the folded parts 7B at both ends thereof, there is a bead apex 10 made of hard rubber and having a triangular cross-section and extending outward in the radial direction from the bead core 2 with its thickness gradually decreasing. is provided to reinforce the sidewall portion 4 and increase the lateral rigidity of the tire. Further, in this example, the belt layer 9 includes a first belt layer 1 disposed from the carcass 7 toward the tread surface.
1. Second belt brace 12, Third belt brace 13
, has a four-layer steel belt structure consisting of a fourth belt blazer 14, the width BW of the second belt blazer 12 is made maximum, the width of the third belt blazer 130 is wider than the first belt ply 11, and the fourth belt Bly 140 width 3rd
By making the maximum width BW of the belt layer 9 0.83 times or more and 0.99 times or less of the tread portion TW, the belt layer 9 covers the tread portion 5 almost as wide as the tread portion TW. The entire width is reinforced with a hoop effect. In addition, the first to fourth belt brakes 11.12.13.1
4 is the belt cord 10 to the tire equatorial plane CO
They are arranged at an angle β of ~30°. Note that it is preferable that the second belt ply cord and the third belt ply cord intersect in different directions with respect to the tire equatorial plane.

〔Concrete example〕

It has the structure shown in Figure 1, and the tire size is 100OR.
2014P, R tires were prototyped based on the specifications in Table 1, and changes in heat generation characteristics, BEL resistance characteristics, and tread curvature radius due to driving were conducted through drum running tests and laboratory tests.

and envelope characteristics were compared with conventional tires.

In addition, the heat generation characteristics are normal internal pressure, normal rim, and normal load.
The tire maximum temperature was evaluated at 20% load and a speed of 80 km/h. The larger the index, the higher the heat generation. In addition, the BEL resistance characteristics were evaluated by increasing the load by 10% from 150% of the normal load at normal internal pressure, normal rim, and speed of 50 km/h based on the load level and time required to reach failure. The larger the index, the higher the BEL resistance characteristics. The envelope characteristics were evaluated by flatly measuring the area of the concave portion when a protrusion with a diameter of 32 mm was applied perpendicularly to the equator of the tire tread under a regular internal pressure, a regular rim, and a regular load. The smaller the area, the better the envelope characteristics are, but in this example, the larger the index is, the better the envelope characteristics are. Furthermore, the tread curvature radius TR was measured before and after running under normal internal pressure, normal rims, and no load. The tread curvature radius TR after running is 1100 at a speed of 50 km/h.
This value was measured after the tire temperature had dropped to room temperature after running 0k. The larger the index, the larger the tread radius of curvature.

〔effect〕

The radial tire for rough roads with this configuration improves the envelope characteristics and uneven wear resistance related to cut resistance and cut penetration resistance on rough roads, and also maintains the peeling resistance (BEL resistance) of the steel belt end. In addition, it is possible to suppress tire heat generation, extend the total tire life, and reduce the weight of the tire.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged sectional view of a belt layer, FIG. 3 is a perspective view thereof, and FIG.
The figure is a perspective view showing a belt layer of the prior art. 2--Bead core, 3--Bead part, 4
・−・−・Side outtle part, 5−・・・−・−Tread part, 7−−−−−・Carcass, 9−・−・・−
Belt layer, 10...Apex, 11--First belt braai, 12--Second belt braai, 13--Third belt braai, 1.1- ----Fourth belt braai, c o---
----- One tire equator. Patent applicant Sumitomo Rubber Industries Co., Ltd. Agent
Patent Attorney Yoshihira NakamuraFigure 2Figure 4

Claims (1)

[Scope of Claims] 1. A carcass consisting of at least one layer of ply cords forming a substantially radial arrangement at an angle of 70° to 90° with respect to the tire equatorial plane, and a metal ply forming an angle of 10° to 30° with respect to the tire equatorial plane. In a radial tire for rough roads, which is provided with a belt layer consisting of at least four layers of cords as main reinforcement, the belt layer includes the cords of the first belt ply b1 and the cords of the second belt ply counted from the carcass side. b2
the cords are in the same direction and the angle difference θ1 is 5° or more and 15
° or less, and the cord of the third belt ply b3 counting from the carcass side and the cord of the fourth belt ply b
4 codes are in the same direction and the angle difference θ2 is 5° or more and 1
A radial tire for rough roads, which has an angle of 5° or less and is arranged in a direction different from the first and second belt ply cords. 2. The distance a2 between the radial cords at the belt end between the layers b2 and b3 is 2.5 mm or more and 4.5 mm or less, and further, a2 and the distance a1 between the radial cords at the belt end between the layers b1 and b2. The ratio r1(a2/a1
) is 1.0 or more and 4.5 or less, and a2 and b
The ratio of the distance a3 between the cords in the radial direction at the end of the belt between layers 3 and b4 is 2 (a2/a3) of 1.0 or more, and 4.
The radial tire for rough roads according to claim 1, characterized in that the tire number is 5 or less.