KR100369616B1 - Steel cord of truck and bus tire for heavy duty - Google Patents

Abstract

The present invention relates to steel cords for heavy duty truck and bus tires, and more particularly, to eliminate wraps in conventional 3d + 9d + 15d + w (d: filament diameter, w: wrap filament) cords. Steel cords for heavy duty truck and bus tires with improved twisting direction to improve loosening of the cutting edge and filament deflection.

The present invention uses a 3d + 8d + 13d cord having a twist direction of SZS and a twist length of 4 to 6 mm / 10 to 15 mm / 18 to 24 mm to improve rubber permeability to improve fracture characteristics, and to eliminate wraps. The purpose of the present invention is to provide a 3d + 8d + 13d cord that can contribute to increasing tire durability by solving the pull and unscrewing of the filament in the cord layer.

Description

Steel cord of truck and bus tire for heavy duty}

The present invention relates to steel cords for heavy-duty truck and bus tires, and more particularly to conventional 3d + 9d + 15d + w or 3d + 8d + 13d + w (d: 0.15-0.35 mm in filament diameter, w: wrap). (Wrap) It is a steel cord for heavy duty truck and bus tires that eliminates wrap and adjusts the twisting direction in the cord of the filament structure to improve the loosening problem of the cutting surface and the filament tipping problem.

Heavy-duty truck and bus tires typically use four-layer belts, with belts numbered from the inside, one of which attaches to the boundary of the carcass, forcing two and three belts to act as actual forces. 2 belts are located on the top of one belt, and the three belts on the top two belts to cushion the forces and external shocks on the tire, and the four belts on the outermost side are sharp objects from the outside. It protects the 2 and 3 belts in case of entering.

Belt sections such as 2 and 3 belts for heavy duty truck and bus tires are made of multilayer steel cords designed to provide sufficient cushioning against external impacts.The structure of these steel cords is typically 3d + 9d + 15d + w. Sometimes 1 × 27d or 3d + 8d + 13d + w is used.

Steel cord is composed of several layers of filaments of a certain thickness, twisted in multiple layers, and the steel cords are arranged side by side to form a cord layer, and the upper and lower layers of the two layers are wrapped in rubber to make tires.

Steel cords of 3d + 9d + 15d + w structure, which are generally used for 2 and 3 belts, are three-layered cords with close intervals between cords. Rubbers do not penetrate the inner cords and are vulnerable to repetitive stress. It acts as a factor of lowering durability.

Conventional 3d + 9d + 15d + w steel cord expresses the twisting direction of SSZS (twisting direction S means the slope of twist falls from left to right like S letter, and Z is the slope of twist falls from right to left). Direction, and the twist length is 6.3mm / 12.5mm / 18mm / 3.5mm, but if you delete the wrap, the twist of the inner SS will loosen, so the twist in the Z direction is not enough, so the filament is pulled out. This will occur. On the other hand, the wrap wraps around the outer shell of the cord, and if repeated bending stress continues, the cord surface and abrasion occur, causing the cord to corrode and causing a drop in strength, thereby directly affecting the tire accident.

In order to improve the rubber penetration of the 3d + 9d + 15d + w cord, a 3d + 8d + 13d + w cord which reduces the number of filaments in the middle layer and reduces the number of filaments in the outer layer by 2 is used, but the twist direction is SSZ, Because of the use of the wrap there is a problem that is difficult to compensate for the disadvantages caused by the above-mentioned wrap. Although 3d + 8d + 13d + w cords may not use wraps, if the wraps are not used, other problems such as uneven rolling of the cord and cutting of the filaments may occur when rolling the outer filaments.

The present invention provides a cord having a 3d + 8d + 13d structure in which the twist direction is SZS and the twist length is 4 to 6 mm / 10 to 15 mm / 18 to 24 mm to solve the above-mentioned problems. In other words, the present invention reduces the number of filaments in the middle and the outer, improves the rubber penetrability by eliminating the wrap to improve the fracture characteristics, the deflection of the filament in the code layer and the unwinding of the filament caused by the deletion of the wrap, It is an object of the present invention to provide a 3d + 8d + 13d code that can contribute to the increase in tire durability by adjusting to SZS in the conventional SSZ and to manufacture a tire with increased durability.

The present invention makes the structure of the steel cord used for the belt portion of the heavy duty truck and bus tires 3d + 8d + 13d (d is a filament having a diameter of 0.15 to 0.35 mm) and the twist direction is SZS, and the cord is constructed. When the filaments are twisted, the twist lengths representing the pitches in the twisting directions are respectively 4 to 6 mm / 10 to 15 mm / 18 to 24 mm. In other words, compared to the steel cord of the existing 3d + 9d + 15d + w structure, the number of middle and outer filaments is reduced, and the wrap is eliminated to improve the rubber penetrability, thereby improving the fracture characteristics, and to remove the wraps. Tension and unwinding of the surface are intended to contribute to increasing tire durability by adjusting the twisting direction of the filament from the conventional SSZ to SZS. In the above, the twisting direction S of the filament is expressed as the inclination of the twist descends from left to right, that is, the twisting of the filament in the left direction, as in the letter S, and Z is the inclination of the twisting descending from the right to the left, that is, the right direction. It is a representation of twisting filament.

Hereinafter, the present invention will be described by the following examples. However, these do not limit the technical scope of the present invention.

<Example 1>

Twisting direction is SSZS with existing cord, 3d + 9d + 15d + w cord with twist length of 6.3mm / 12.5mm / 18mm / 3.5mm, twisting direction with SSZ with twisting cord is 6.5mm / 12mm / 19mm 3d + 8d + 13d + w cord of 4mm, rubber penetration for 3d + 8d + 13d cord with twisting direction of SZS and twist length of 6mm / 12mm / 20mm with cord of the present invention, cord unwinding, filament bowing, The items for the fatigue test were measured and the results are shown in Table 1 below.

Table 1. Code test results

Item Existing code (SSZS) (3d + 9d + 15d + w) Improvement Code (SSZ) (3d + 8d + 13d + w) Invention Code (SZS) (3d + 8d + 13d) Rubber penetration E A A Code unwinding B D A Filament Tension none Severe none Fatigue Test (RBT) * 3500 6000 times 6300 times

A: Very good, B: Excellent, C: Normal, D: Thirteen, E: Very thirteen

* RBT: Rotating beam tester

In the results of Table 1, the code of the existing code 3d + 9d + 15d + w (SSZS) structure showed a bad result in the measurement of rubber penetration and fatigue test items, the improved code 3d + 8d + 13d The code of + w (SSZ) structure showed poor results in the code unwinding and filament pulled items, and the code of the present invention code of 3d + 8d + 13d (SZS) showed overall excellent results. .

<Example 2>

The existing cord, the improved cord, and the cord of the present invention were applied to the tire of the 1200R24 standard to test the speed endurance and the load endurance, and the results are shown in Table 2 below.

Table 2. Evaluation of durability when applying tire of 1200R24 size

Item Existing code (SSZS) (3d + 9d + 15d + w) Improvement Code (SSZ) (3d + 8d + 13d + w) Invention Code (SZS) (3d + 8d + 13d) Speed Durability * 64:54 65:12 67:52 Load durability ** 74:32 71:48 80:22

* Speed endurance test is performed using ECER-54 method of European standard.

** Load endurance measurement test is done using DOT119 method of North American regulations.

As can be seen in Table 2 above, the code of the present invention was able to obtain better results in speed endurance and load endurance compared to the existing code and the improved code.

The 3d + 8d + 13d cord of the present invention having the twist direction SZS as in the result of Example 1 and Example 2 can prevent the accident due to the wear between the filaments by removing the wrap, the problem of loosening the cord and filament Not only that, but the durability of the tire can be expected.

Claims (3)

In steel cords for heavy duty truck and bus tires, Steel cord of heavy duty truck and bus tires with SZS twisting direction and 3d + 8d + 13d (d is filament with diameter of 0.15 ~ 0.35mm) 2. The steel cord of a heavy duty truck and bus tire according to claim 1, wherein the twist direction S is the slope of the twist from left to right, and Z is the slope of the twist from the right to left. The steel cord of a heavy duty truck and bus tire according to claim 1, wherein the twist length of the 3d + 8d + 13d cord is 4 to 6 mm / 10 to 15 mm / 18 to 24 mm.