JPH03279432A - Radial tire for heavy load - Google Patents

Abstract

PURPOSE:To prevent the separation of plies from each other and the generation of the concussion of the tire by embedding belt cords in the tire in a layer- twisted structure of n+(3n-x)+(5n-y) type. CONSTITUTION:A belt layer 7 is wound in the peripheral direction of a carcass in the tread portion thereof in the outside and tire radius direction and the belt layer 7 is formed in a layered structure comprising belt plies 7A, 7B and 7C. The belt cords constituting each belt plies have layer-twisted structures, respectively, of a n+(3n-x)+(5n-y) type (n is an integer of 2-4; x is an integer of 1-y; y is a positive integer). The distance between belt cords in the belt plies 7A, 7B is 0.3-0.6 time the diameter of the belt cords, and the distance between the belt cords in the direction rectangular to the belt plies is 0.15-0.42 time the diameter of the belt cord.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heavy-duty radial tire in which belt durability can be improved by specifying belt cords and regulating the distance between the cords.

[Conventional technology]

For example, radial tires used for heavy-duty vehicles such as trucks and buses have multiple layers of steel cord arranged on the outside of the carcass, usually 3 to 4 layers of toughness, in order to increase tire rigidity and improve running performance. A belt layer is wrapped around the belt.

Also, this type of steel cord is generally shown in Figure 7 (a).
7x4 type (filament diameter: 0.22 m) composite twisted structure in which seven strands S, which are made by twisting four filaments fS, are further twisted together, as shown in (l ~ mountain), and n Around the core C, which is made by twisting book core filaments fc, 3n filaments f
Inner filament III consisting of i and 5n outer filaments fo
n+3n+5n+1 type, usually 3↓9+15+1 type (filament diameter = 0.22 m), in which an outer layer 0 consisting of
) is used.

[Problem to be solved by the invention]

However, in the composite twisted structure, the contact pressure between each strand S is high, which causes abrasion between adjacent filaments fs, and tends to cause so-called fretting in which the filaments fs break early.

In addition, in the case of the layered structure, although the fretting is reduced, the gaps between the inner filaments fi and between the outer filaments fo are too small, and the ply rubber cannot sufficiently penetrate into the cord. Corrosion resistance is poor, as cavities are formed within the cord through which moisture propagates.

On the other hand, all such cords have relatively large diameters, so in order to alleviate the shearing force acting between the cords and suppress separation between the cords and the ply rubber, it is necessary to reduce the cords within each ply. It is necessary to set both the distance between cords and the distance between cords between adjacent plies to be large.

However, an increase in the distance between the cords within a ply causes, for example, a frequent occurrence of so-called concussion, in which the impact force acting locally on the tread surface concentrates on a small number of belt cords, causing the cords to break. This increase leads to an increase in belt thickness, which increases tread heat generation and impairs high-speed durability.

Therefore, in conventional tires using such cords, the belt durability is greatly reduced due to both the durability of the cords themselves and the distance between the cords that increases when the cords are used, and the tire service life is shortened. The problem is that it damages the

Note that as shown in FIG. 7(C), the filament diameter is 0,
3+ in which an outer layer 0 consisting of six outer filaments fQ with a filament diameter of 0.38 m was formed around a core C consisting of three core filaments fc with a filament diameter of 2 wm.
Type 6 belts are also used in some cases, but although this cord has a smaller diameter, the cord strength is weaker and concussions occur frequently, resulting in belt damage.

An object of the present invention is to provide a mold-heavy radial tire that can effectively suppress belt damage caused by both the belt cords themselves and the distance between the cords, and can greatly improve the service life of the belt.

[Means to solve the problem]

In order to achieve the above object, the heavy-duty radial tire of the present invention has steel belt cords arranged in parallel to each other on the outside of the carcass in the tire radial direction and inside the tread part, and the belt cords are arranged parallel to each other on the outside of the carcass in the tire radial direction and inside the tread part. A belt layer including at least a first belt ply, a second belt ply, and a third belt ply sequentially arranged toward the carcass is provided, and each belt cord in the first and second belt plies is n A core made of book core filaments twisted together spirally, and a 3n-
It has an inner layer in which x inner filaments are twisted together in a spiral, and an outer layer in which 5n-y outer filaments are twisted in a spiral around the inner layer 1, and n is 2 or more and 4. The layered structure has the following integer and X is an integer of 1 or more and y or less, and the gap t between the belt cords in each of the first and second belt plies is set to 0 of the diameter of the belt cord. .3 times or more and 0.6 times or less, and the gap T in the direction perpendicular to the first belt ply between the belt cord of the first belt ply and the belt cord of the second belt ply is The distance is set to be 0.5 times or more and 0.7 times or less of the interval t.

[Effect]

The heavy-duty radial tire constructed in this way adopts a layered structure for each belt cord of the first belt ply located at the outermost position and the second belt ply located inside thereof, while the number of filaments is reduced from that of the conventional one. By reducing the number of filaments by X in the inner layer and by y in the outer layer, and increasing the gaps between the inner and outer filaments, it is possible to improve the permeability of the Bly rubber into the cord. As a result, the corrosion resistance can be improved, and in combination with the suppression of fretting due to the use of the layered structure, the durability of the cord itself can be improved while maintaining the necessary strength of the cord.

In addition, since the belt cord eliminates roughing, its diameter can be reduced compared to conventional belt cords, thereby suppressing the separation of the belt cord from the briquette rubber, and It is possible to reduce the gap between the belt cords in each belt ply and the gap T between the belt cords between the first and second belt plies to within a predetermined range. Therefore, reducing the gap t, that is, increasing the number of cords driven in, has the effect of dispersing, for example, a large impact force locally applied to the tread surface to a large number of belt cords, and can suppress breakage of the cords. . Further, a reduction in the gap T helps to reduce the belt thickness, thereby increasing the in-plane compatibility of the tread portion uniformly and improving running performance, while reducing tire heat generation and improving high-speed durability.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

In the figure, a heavy load radial tire 1 has a bead core 2
The tire includes a bead part 3 through which the tire passes, a sidewall part 4 extending outward in the tire radial direction from the bead part 3, and a tread part 5 connecting the outer ends of the sidewall part 4.

A toroidal carcass 6 extending from the tread portion 5 to the sidewall portion 4 is stretched between the bead portions 3 and 3, and a belt layer is placed on the outside of the carcass 6 in the tire radial direction and inside the tread portion 5. 7 is wound in the circumferential direction.

The carcass 6 is formed of one or more carcass plies, in this example, one carcass ply, in which carcass cords are arranged at an angle of 70° or more and 90'' with respect to the tire equator, and both ends of the carcass ply are arranged around the bead core 2 on the inside. It is folded outward from the

And between the main body part and the folded part of the carcass 6,
A bead apex 8 made of hard rubber is interposed and extends radially outward from the bead core 2 in a tapered shape, and the bead portion 3
From there, the side wall portion 4 is reinforced. As the carcass cord, organic fiber cords such as nylon, rayon, and polyester are suitable, and sometimes steel cords can also be used depending on the tire performance requirements.

Further, the belt layer 7 includes first,
This example has a three-layer structure including second and third belt plies 7A, 7B, and 7C, and the width W7B of the second belt ply 7B is larger than the width W7C of the third belt ply 7C. There is.

Further, the first belt ply 7A is connected to the third belt ply 7A.
As a result, the second belt ply 7B is at its maximum and both ends thereof are located below the tread end.

Further, the bells) 7A, 7B, and 7C are cord array bodies in which steel belt cords 10 are respectively arranged at an angle of 10' or more and 30 degrees or less with respect to the tire equator and are coated with Bly rubber. , 7B, and 7C are arranged in different directions so that the respective belt cords 10 cross each other between the plies. Therefore, the belt layer 7 constitutes a strong truss structure by the belt cords 10 that intersect with each other, improving tread flexibility and restraining the carcass 6 with a high hoop effect.

In the present invention, the first and second belt plies 7
The belt cords used for A and 7B are specified, and the distance between the cords is regulated.

That is, as shown in FIG. 2, the belt cord 10 of the first and second belt plies 7A and 7B includes a core 12 in which n core filaments 12f are twisted together spirally, and a core 12 formed around the core 12. 3n-X filamen) 13
n that does not include wrapping, comprising an inner layer 13 in which filaments f are twisted together in a spiral manner, and an outer layer 14 in which 5n-7 outer filaments) 14f are twisted in a spiral manner around the inner layer 13;
+ (3n-x) + (5n-y) type layered structure, where n,! , 7 are positive integers, n is set to 2 or more and 4 or less, and X is set to 1 or more and y or less.

In addition, in Figure 2, n = 3, x = l, ) f - 2 and 3 + 8
A +13 type is illustrated.

Such a belt cord 10 has a number of filaments of X in the inner layer 13 compared to a conventional layered structure.
Since y fibers are reduced in the outer layer 14, it is possible to increase the gap g1 between the inner filaments 13f and the gap g2 between the outer filaments 14f, increasing the permeability of the blue rubber into the cord and improving corrosion resistance. It can improve sex.

Further, each filament 12f, 13f, 14f is made of steel wire, respectively.
(7) Each diameter d1, d2, d3 should be 0.15 m or more and 0.40 mm or less, respectively, and in order to optimize the tensile strength and bending rigidity of the belt cord 10, each diameter d
1, d2, and d3 are set to d1≧d2≧d3.

Moreover, such a belt cord 10 has each filament 12f.
, 13f, and 14f are preferably twisted in the same direction, and in this case, the twisting pitch P2 of the inner filament 13f is set to be larger than the twisting pitch P1 of the core filament 12f and smaller than the twisting pitch P3 of the outer filament 14. .

The reason why the twist directions are the same here is that by making them the same, the crossing angle between adjacent filaments in the radial direction can be reduced, and the contact pressure between each filament can be further reduced. The corrosion resistance and the durability of the cord itself can be greatly improved.

FIG. 3 shows the air permeability of the belt cord 10 in comparison with a conventional cord.

Furthermore, since the belt cord 10 eliminates rough ping, its diameter can be reduced, and together with the effect of alleviating the cord amphiphilia due to the reduction in the number of filaments, the belt cord 10 and the ply rubber are The distance between the belt cords 10 can be reduced within a predetermined range while suppressing separation.

Table 1 shows the diameter of the belt cord 10 and its strength in comparison with conventional cords.

By using the belt cord 10, as shown in FIG.
The gap t between the belt cords 10 in A and 7B is in the range of 0.3 times or more and 0.6 times or less of the diameter of the belt cord 10, and the belt cord l of the first belt ply 7A is
The gap T in the direction perpendicular to the first belt ply 7A between the belt cord 10 of the second belt ply 7B and the belt cord 10 of the second belt ply 7B is
It can be set in a range of 0.5 times or more and 0.7 times or less of the gap t.

Note that these ranges have been derived from the results of various experiments conducted by the present inventor, and examples thereof are shown in FIG. 5.6.

Note that FIG. 5 shows the relationship between the ratio t/D of the diameter to the gap t and the incidence of tread concuffage.

In other words, when the gap t is reduced and the ratio t/D is 0.6 or less, in other words, when the number of cords is large, the large impact force locally applied to the trend surface is dispersed to a large number of belt cords. This makes it possible to eliminate the stress concentrated on each cord and to prevent the occurrence of concuffs.

If the ratio t/D exceeds 0.6, the dispersion effect will be poor and concavity will increase.

Conversely, if t/D is less than 0.3, the ply rubber cannot alleviate the shearing force acting between the cords, resulting in separation of the belt cords 10.

Further, FIG. 6 shows the relationship between the ratio T/l of the gap T and the gap t and the incidence of peeling between the plies at the end of the belt.

This is because, as described above, in the belt layer 7, the belt cords intersect between the plies, so that the belt plies 7A, 7B, and 7C extend in different directions when the tire deforms. As a result, shear stress acts between each ply, and inter-braid peeling tends to proceed sequentially from the ply end of the outermost belt ply 7A.Therefore, if the ratio T/l is 0.5 or more, intercalation occurs between the cords. The ply rubber can relieve the shearing stress and effectively suppress the gap between the briars Wi.

Note that when the ratio T/l exceeds 0.7, the belt layer thickness increases excessively, increasing the tire weight. Furthermore, the internal temperature of the tread increases, impairing high-speed performance, while reducing tread resistance and driving performance.

The specification of the belt cords 10 and the regulation of the distance between the cords are applied to the outermost first belt ply 7A where cord damage is most likely to occur and peeling between the plies, and the second belt ply inside the first belt ply 7A. 7B, it is preferable to restrict the third belt ply 7c located inside the third belt ply 7B in the same way. may be further provided.

〔Effect of the invention〕

The heavy-duty radial tire of the present invention has a belt cord with an n+ (3n-x) + (5n-y) type layered structure, which maintains the necessary strength of the cord while increasing the durability of the cord itself. can be improved.

Moreover, by using this belt cord, it is possible to reduce the distance between the cords within a predetermined range, thereby making it possible to press open the 11 m gap between plies and to prevent the occurrence of concuffs, thereby increasing the durability of the belt. In addition, the belt thickness can be reduced, thereby suppressing tire heat generation, improving high-speed durability, and uniformly improving tread in-plane measurement properties to improve running performance.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing one embodiment of the present invention, Fig. 2 is a sectional view showing one row of belt cords, Fig. 3 is a graph showing its air permeability, and Fig. 4 is a sectional view showing the belt layer. , FIG. 5 is a diagram showing the relationship between ratio t/D and trend concussion occurrence rate, FIG. 6 is a diagram showing the relationship between ratio T/l and inter-ply delamination, and FIG. (C) is a sectional view showing the prior art. - Tread part, 6 - Carcass, - Belt layer, 10 - Peltco-2... 1st
3-second belt ply; 4-third belt ply. Figure 2 Figure 3 Air release & stock index Figure 4

Claims (1)

[Claims] 1 A first belt ply consisting of steel belt cords arranged parallel to each other on the outside in the tire radial direction of the carcass and inside the tread part, and arranged sequentially from the outer surface side of the tread part toward the carcass; A belt layer including at least a third belt ply and a third belt ply is provided, and each belt cord in the first and second belt plies includes a core in which n core filaments are twisted together spirally, and a belt layer including a third belt ply. It has an inner layer in which 3n-x inner filaments are helically twisted around the core, and an outer layer in which 5n-y outer filaments are helically twisted around the inner layer, and the above-mentioned The belt has a layered structure in which n is an integer of 2 or more and 4 or less, and x is an integer of 1 or more and y or less, and the gap t between the belt cords in each of the first and second belt plies is The diameter D of the cord should be 0.3 times or more and 0.6 times or less, and the belt cord between the first belt ply and the second belt ply should be at right angles to the first belt ply. A radial tire for heavy loads in which a gap T in the direction is set to be 0.5 times or more and 0.7 times or less the distance t.