JPS59118507A - Radial tyre of heavy vehicle - Google Patents

Abstract

PURPOSE:To surely prevent separation of plies by disposing a covering ply which is made of organic fiber as wide as covering the uppermost ply, on a belt lamination of a plurality of the plies which are interposed between the tread part and the carcass of the tyre described in the heading. CONSTITUTION:In a tyre described in the heading which has a belt lamination 10 disposed between a tread part and a radial ply carcass at the crown part thereof, a belt lamination 10 is built up by the first to the third plies 11-13 each of which is made of steel cord. The cord angle of the first ply 11 is set within the range of approximately 50 deg.-70 deg. with respect to the circumferential direction of the tyre. The cord angle of the second ply 12 is determined within the range of approximatey 10 deg.-20 deg. with respect thereto and inclined in the same direction as that of said ply 11 and the width thereof is determined greater than that of each of the first and third plies 11 and 13 and approximately equivalent to that of the tread. A covering ply which is made of organic fiber of 10<5>kg f/cm<2> or more in initial modulus and is wider than the third ply 13 is disposed on the aforesaid belt lamination 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radial tire for a heavy vehicle, and more particularly to an improvement in a radial tire for a heavy vehicle in which a coated belt is disposed at the top of the belt layer to alleviate strain.

In general, the structure of a radial tire for heavy vehicles is as shown in Figure 1, where both ends are folded back around a bead core (1).
More than one toroidal carcass ply (2) is arranged with its cord in the radial or semi-radial direction, the bead part is reinforced with a bead filler (3), and a tread (4) is arranged in the crown part (B). On the underside of the tread (4), a belt layer (9) was formed by stacking four plies (5), (6), (7), and (8) made of steel cord in the circumferential direction. Things are commonly used. The structure of the belt layer (9) is as shown in Table 1.
types are used. Here, type A structure has a large cord angle of the first ply (5) with respect to the circumferential direction, increases the in-plane bending rigidity of the belt layer, and furthermore, the cord of the second ply (6) and the third ply (7 ) are made to intersect with each other in the circumferential direction to increase the circumferential rigidity of the belt layer, resulting in a so-called triangular structure. In addition, type B has a cord of each ply of 10 to 10 mm in the circumferential direction.
The structure is so-called a low-angle structure, which is arranged so as to be inclined in opposite directions alternately at a relatively shallow angle of 30 degrees. In this structure of the belt layer, the second ply (6) has the widest groove, and the second ply (6) and the third ply (7) intersect at a large angle.
Peeling between the plies is likely to occur due to stress concentration near both ends of the ply (7).

That is, in FIG. 2, when the tire runs, stress is transmitted from the ground contact surface to the inside of the tread in the direction of the arrow, but is blocked by the belt layer, particularly the second ply (6), which is the widest.

However, both ends of the third ply (7) and the fourth ply will be strained due to direct stress, especially the third ply (7).
Coupled with the large cord crossing angle with the second ply (6) at both ends of the cord, ply peeling is likely to occur due to stress strain. The present invention solves this problem and proposes a radial tire for heavy vehicles in which stress strain at both ends of the third ply is alleviated and ply peeling is effectively prevented.

The present invention has a tread part in the crown part of the radial ply carcass and a belt layer installed between the tread part and the carcass, and the belt layer has five steel cord plies laminated and a second layer located in the middle. The plies are configured to have the widest width, and the upper side of the belt layer is made up of plies with an initial modulus of 10^5 kgf/cm^2 or more and which intersect the cords of adjacent plies at an angle of 10 or less. This is a radial tire for heavy vehicles that is characterized by having a covering ply that is wider than the radial tire. Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 3 is a schematic plan view of the belt layer of the radial tire of the present invention. In the figure, the belt layer (10) is based on the above-mentioned type A belt layer structure, and the first
Ply (11), second ply (12) and third ply (
13) are all constructed of steel cord.

Here, the cord angle of the first ply (11) is arranged at an angle of 50 to 70 with respect to the tire circumferential direction. This is to reduce the cord angle between carcass plies that have cord angles close to this, reduce ply distortion between them, and increase the in-plane bending rigidity of the belt layer by forming a triangular groove structure with other plies. be.

Next, the cord angle of the second ply (12) is 10° to 30° with respect to the tire circumferential direction, and is inclined in the same direction as the first ply. The width of the groove is wider than the width of the first ply (11) and the third ply (13) that are vertically adjacent to each other, and the width is approximately the same as the tread width.

Next, the third ply (13) is usually the first ply (11) (
The cord angle is formed to be wider than W1) and intersects the cord of the second ply (12) with an inclination in the opposite direction, and the angle is −10° to −30° in the tire circumferential direction. A covering ply (14) is arranged on the upper side of said belt layer (10), where a negative angle means that it is inclined in the opposite direction to the cords of the second ply. Covered ply (14)
is configured to have a width wider than at least the width (W3) of the third ply (13), and by completely covering both ends of the third ply, stress strain at the ends can be alleviated.

Here, the cord of the covering ply (14) is composed of an organic fiber cord having an initial modulus of 10^5 kgf/cm^2 or more, such as an aromatic polyamide fiber cord. In addition, the cords of the covering ply must intersect with the cords of the adjacent third ply (13) at a shallow angle of less than 10 degrees to minimize the stress strain between both plies. An arrangement that intersects the circumferential direction at a shallow angle is more preferable.

In addition, the aromatic polyamide fiber cord has a twist coefficient (NT) of 0.20 to 0.55 for both top twist and bottom twist, as shown by the following formula.
The first twist is preferably in the range of 0.30 to 0.42, and the first twist is 120 to 180% of the first twist.

(Here, N is the number of twists per 10 cm of cord, D is 1/2 of the total denier of the cord, and ρ is the specific gravity of the fiber.

) When the twist coefficient exceeds 0.55, the strength and modulus decrease, and the ply becomes curled, impairing molding workability.

On the other hand, if it is less than 0.20, it is not preferable because it impairs the cohesiveness and fatigue resistance. Further, the embedded rubber of the covering ply (14) has a modulus of the same level or slightly smaller than that of the embedded rubber of the adjacent steel cord layer, for example, a 300% modulus elongation of 120 to 230 kg/cm^2, particularly 180 to 230 kg. /cm^2 range is desirable. On the other hand, by using rubber embedded in the belt layer with a 300% modulus in the range of 180 to 230 kg/cm^2, the sleeve strength effect can be enhanced. If the modulus is less than 120 kg/cm^2, the covering ply (1
The effect of arrangement 4) cannot be expected to be sufficient.

Note that the covering ply (14) covers at least the third ply (13).
), but it can also be configured wider than the second ply (12), which is the widest, and is usually set in a range of 90 to 120% of the width (W2) of the second ply. . In particular, if it exceeds 120%, new stress concentration points will occur at both ends of the covering ply.

As mentioned above, the present invention has been described with respect to a structure in which the belt layer structure is based on type A, that is, a triangular structure, but it goes without saying that a structure based on type B can also be applied.

As described above, in the present invention, a coating layer made of a high modulus cord is arranged in a specific configuration in place of the fourth ply of a belt layer of a steel radial tire, particularly a belt layer of a triangular structure or a low angle structure, so that the coating layer is arranged at both ends of the third ply. The stress strain in the region is alleviated, and ply peeling in the region can be effectively prevented.

Example Tire size: 10.00R20 14PR Steel radial carcass cord plain tires were manufactured as trial tires with various specifications shown in Table 1, and their performance was evaluated. The results are shown in the same table. The basic structure of the prototype tire is as shown in Figure 1, excluding the belt layer.

Crack damage at the end of the belt layer is on a drum diameter of 1593 mm, tire internal pressure 8.0 kgf/cm^3, and load 4000 kg.
f. The belt was run at a speed of 50 km/h, and the running distance until ply peeling occurred at the end of the belt layer was measured.

From the performance results shown in Table 1, it is recognized that all of the tires of the present invention have significantly improved ply peelability at one end of the belt.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the tire, FIG. 2 is a partial sectional view of the tire tread, and FIG. 3 is a schematic plan view of the belt layer of the tire of the present invention. 10...Belt layer 12...Second ply 11...
・First ply 13...Third ply 14...Coating layer

Claims (1)

[Claims] (1) The crown part of the radial ply carcass has a tread part and a belt layer installed between the tread part and the carcass. The ply is configured to have the widest width, and the upper side of the belt layer is made up of organic fiber cords with an initial modulus of 10^5 kgf/cm^2 or more, which intersect the cords of adjacent plies at an angle of less than 10. A radial tire for heavy vehicles, characterized in that a covered ply is arranged that is wider than the adjacent ply.