KR20070025484A - Structure of radial tire for truck and bus - Google Patents

Abstract

A radial tire structure for a truck and a bus is provided to use a cord with the high tensile quality of the material and having a warp filament removal structure and the reduced number of EPI(End Per Inch) as a steel cord to be applied to a belt layer of a tire, thereby enhancing the durability. A steel chafer for reinforcing a bead portion is applied to the radial tire structure. A steel cord is applied to a belt layer of the tire. The steel cord is a high tensile cord having the carbon content of 0.80 to 0.85% and constructed by a structure of 3+9 x d1(d1 is a diameter of a filament). The cord array per 1 inch is 9 to 11.0 EPI. The d1 is preferably 0.22mm. The steel cord is also constructed by a structure of 3+9 x d2(d2 is a diameter of a filament). The cord array per 1 inch is also 9 to 11.5 EPI. The d2 is preferably 0.20 or 0.22mm.

Description

Radial Tire Structure for Trucks and Buses {Structure of Radial Tire for Truck and Bus}

1 is a cross-sectional view of a radial tire for a truck and a bus in general.

2 is a cross-sectional view showing the structure of a conventional steel cord.

3 is a cross-sectional view showing the structure of a steel cord according to the present invention.

<Explanation of symbols for main parts in the drawing>

1: Tread

2: Carcass

3: belt layer

7: Bead

8: Steel Chafer

10, 20, 30: Steel Cord

11, 21, 31: 1st layer core

11a, 21a, 31a, 12a, 22a, 32a: filament

12, 22, 32: second layer core

13: wrap core

13a: wrap filament

The present invention relates to the structure of a radial tire for trucks and buses, and more particularly, to remove the wrap filament as a steel cord applied to the steel chaper and the belt layer of the tire. By using a cord with a high-strength material while reducing the number of end per inch (EPI), the truck not only improves the durability of the tire to withstand high loads, but also reduces the tire weight and improves fuel efficiency while driving. And a radial tire for a bus.

Radial tires for trucks and buses in general include, as shown in Figure 1, the tread (Tread) 1 which is a part in direct contact with the road surface; Carcass (2) forming a skeleton of a tire; A belt layer (Belt) 3 laminated between the tread 1 and the carcass 2; An inner liner 4 for preventing air leakage; Side wall (5) to protect the carcass (2) and to allow flexible flexing movement; A shoulder portion 6 positioned between the tread 1 and the sidewall 5; The bead portion 7 wraps around the end of the carcass 2 and mounts the tire on the rim.

Furthermore, the belt layer 3 is generally provided with four belts (hereinafter referred to as "carcass") to alleviate the impact received from the outside during driving and to prevent the tread 1 from cracking or trauma directly reaching the carcass 2. The first belt 3a, the second belt 3b, the third belt 3c, and the fourth belt 3d.

Since the radial tires for trucks and buses of this structure must transmit power while supporting the weight of the vehicle and the weight of the package, a lot of stress is concentrated in the bead portion 7 and the belt layer 3, and accordingly the beads The portion 7 and the belt layer 3 are in a weak state.

Therefore, in order to increase the durability of the tire, as shown in FIGS. 1 and 2, a steel chaper 8 for reinforcing the bead portion 7 is applied to the steel chaper 8. (Steel Cord, 10) is used, and the steel cord 10 is also used as the reinforcing material in the belt layer 3 as well.

The steel cord 10 is configured by twisting a plurality of filaments having a predetermined thickness in multiple layers and arranging them at predetermined intervals and angles.

Conventionally, as such a steel cord 10, as shown in Fig. 2, the first layer core (11, 11) and the first layer core, twisted three filaments (11a) in the S direction, as shown in FIG. The second layer core 12 twisted in the S direction to enclose the 11 filaments 12a, and the twisted filament 13a in the Z direction to prevent the cord from being unwound in the outermost layer. The cord of the so-called 3 + 9xd + w (d: diameter of filament, w: wrap) structure which consists of the wrap (Wrp) core 13 is used typically. Where d is approximately 0.22 mm.

The belt layer 3 or the chafer 8 described above is manufactured by rolling (topping) rubber to a predetermined thickness on both sides of the steel cord 10 having such a structure.

However, the steel cord 10 according to the related art includes a wrap core 13 which is a wrap filament 13a, resulting in a tire weight with a cost increase, and the diameter of the wrap core 13 is 0.15. Since it is thin about mm, it causes an accident that the cord is broken while excessive deformation is repeated by friction between the filament 12a of the second layer core 12 therein while driving, thereby greatly reducing the durability of the tire. There was this.

Moreover, when the wrap filament 13a is used, not only the workability is poor because the cord is very hard when the tire is molded, and the rubber penetration into the cord is not easy when the rubber is rolled on the tire. When used for a long time, the steel cord is corroded, thereby reducing the adhesive strength with the rubber has a problem of deteriorating the tire fatigue characteristics.

Particularly, since the conventional steel cord 10 uses NT (Normal Tensile) cord having a carbon content of about 0.67 to 0.73% as its material, the cord array density per inch is increased by 11 to 1 to increase the cord strength of the tire. 13 EPI (End Per Inch) was increased to about the number of the number of cord strands per inch, resulting in an increase in the weight of the tire, because of the increased rolling resistance characteristics of the tire while driving, there was a problem that fuel efficiency is poor.

Accordingly, the present invention has been made to solve the above-described problems, and has a high-strength material while eliminating the wrap filament and reducing the number of end per inch (EPI) as a steel cord applied to the steel chafer and the belt layer of the tire. The purpose of the cord is to improve the durability of the tire to withstand high loads, and to reduce the weight of the tire, thereby improving fuel efficiency.

In order to achieve the above object, the present invention, in the radial tire structure for trucks and buses applying a steel cord to the chafer or belt layer for reinforcing the bead portion,

In the radial tire structure for trucks and buses, in which a steel cord is applied to a chafer or belt layer for reinforcing a bead part

The steel cord is a high-strength cord having a carbon content of 0.80 to 0.85%, has a structure of 3 + 9 × d1 (d1: diameter of filament), and the cord arrangement per inch is 9 to 11.0 End Per Inch (EPI). It features.

In the present invention,

The d1 is characterized in that 0.22mm.

In addition, in the present invention, in the radial tire structure for trucks and buses to which a steel cord is applied to a chafer or belt layer for reinforcing a bead part,

The steel cord is a high tensile cord having a carbon content of 0.80 to 0.85%, and has a structure of 3 + 8 × d2 (d2: diameter of filament), and the cord arrangement per inch is 9 to 11.5 EPI (End Per). Inch).

In the present invention, the d2 is characterized in that 0.20mm or 0.22mm.

In the present invention, the steel cord is used for at least one of the outermost belt and the innermost belt of the belt layer.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

The radial tire for trucks and buses according to the present invention, as shown in FIG. 1, has a belt layer 3 consisting of a tread 1, a carcass 2 and four belts 3a, 3b, 3c and 3d. Since it is the same as the conventional tire structure including the bead portion 7 and the steel chafer 8 for reinforcing the bead portion 7, the detailed description thereof will be omitted.

According to the present invention, in a radial tire for a truck or a bus having such a structure, a steel cord having a specific structure is used for the steel chafer 8 and the belt layer 3 to improve the durability of the tire and reduce the overall weight. In addition, to improve fuel efficiency while driving.

Figure 3 (a) shows a cross-sectional view of a steel cord according to an example of the present invention.

The steel cord 20 according to the present invention is a high tensile (HT) cord having a carbon content of 0.80 to 0.85%, and has a 3 + 9 × d1 structure as shown in Fig. 3. This 3 + 9 The structure of xd1 has the 1st layer core 21 which twisted 3 filaments 21a in S direction inside, and 9 filaments 22a in Z direction so that the 1st layer core 21 may be wrapped. It consists of a twisted 2nd layer core 22. Here, d1 shows the diameter of the filament 22a of the 2nd layer core 22, and is about 0.22 mm.

As such, the present invention can prevent the unwinding of the cord by changing the twisting direction of the steel cord 20 from the conventional SSZ to the SZ direction, so that no wrap filament as in the prior art is required.

Further, according to the present invention, by using a high strength material having a high carbon content as described above, the number of EPIs representing the array density of cords per inch can be set smaller than before. It is preferable that the number of EPI in this invention is 9-11. If the number of EPI is less than 9, it is not suitable for preventing impact from high loads and external stimuli, and if it exceeds 11, there is a problem that the amount of rubber applied to each steel cord decreases.

On the other hand, Figure 3 (b) shows the structure of a steel cord according to another example of the present invention. The steel cord 30 shown in FIG.3 (b) is a filament 32a which comprises the 2nd layer core 32 which encloses the outer layer of the 1st layer core 3l which consists of three inner filaments 31a. ), And has a structure of 3 + 8 × d2 (d2: diameter of the filament of the second layer core), the operation of which is reduced to eight. The twisting direction of this steel cord is SZ direction as mentioned above. In this case, the number of EPIs can be set in about the same range as compared with the still code shown in Fig. 3A. That is, the number of EPI is 9 to 11.5. At this time, the d2 is 0.20mm or 0.22mm.

As described above, according to the present invention, the number of EPIs can be set smaller than before while maintaining the sufficient strength of the steel cords 20 and 30, thereby improving tire durability and achieving lightweight tires. Therefore, it is possible to reduce fuel consumption by reducing the rolling resistance characteristics of the tire when driving.

The present invention applies the steel cord 20 and 30 having such characteristics to the steel chafer 8, which is used for reinforcing the bead portion 7 of heavy and heavy load truck and bus tires, thereby reinforcing the bead portion 7. Will be increased.

Furthermore, the present invention provides the improved steel cord 20, 30 as described above to the farthest position away from the carcass 2 so as not to damage the main belt layers 2 and 3 belts 3b and 3c. It can be applied to the four belts (3d) as the outer belt so that the stress is injected when the external local shock from the tread (1) in contact with the road surface can be sprayed to play a role of shock mitigation. The steel cords 20 and 30 are not necessarily applied only to the four belts 3d but can also be applied to the one belt 3a which is the innermost belt closest to the carcass. That is, the steel cords 20 and 30 according to the present invention may be used for at least one of the four belts 3d and one belt 3a.

As described above, according to the present invention, tires are subjected to high loads by increasing the cord strength by using HT steel cords having a carbon content of 0.80% to 0.85% instead of conventional NT steel cords in steel chafers or belt layers for bead reinforcement. It is possible to improve the durability of the tire, and also to reduce the number of EPI by increasing the cord strength, thereby making it possible to reduce the weight of the tire, thereby reducing the fuel consumption as well as reducing the rolling resistance during driving.

Although the present invention has been described with respect to the preferred embodiment, the present invention is not limited thereto, and various modifications and applications will be possible to those skilled in the art without departing from the gist of the present invention.

Claims (5)

In the radial tire structure for trucks and buses, in which the steel cord 20 is applied to the steel chafer 8 or the belt layer 3 for reinforcing the bead part 7, The steel cord 20 is a high tensile cord having a carbon content of 0.80 to 0.85%, and has a structure of 3 + 9 × d1 (d1: diameter of filament), and the cord arrangement per inch is 9 to 11.0 EPI. Radial tire structure for trucks and buses, characterized in that (End Per Inch). The method of claim 1, Radial tire structure for trucks and buses, characterized in that d1 is 0.22mm. In the radial tire structure for trucks and buses, in which the steel cord 30 is applied to the steel chafer 8 or the belt layer 3 for reinforcing the bead part 7, The steel cord 30 is a high strength cord having a carbon content of 0.80 to 0.85%, and has a structure of 3 + 8 × d2 (d2: diameter of filament), and the cord arrangement per inch is 9 to 11.5 EPI (End Per Inch). Radial tire structure for trucks and buses, characterized in that). The method of claim 2, The radial tire structure for trucks and buses, characterized in that d2 is 0.20mm or 0.22mm. The method according to claim 1 or 3, The steel cord (20) (30), the radial tire structure for trucks and buses, characterized in that used for at least one of the outermost belt (3d) and the innermost belt (3a) of the belt layer (30).

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