JPH0523201B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a belt structure for a heavy-duty pneumatic radial tire. Specifically, the No. 1 belt has a split structure, which improves the durability of the crown part on rough roads, while improving the durability of the crown on rough roads. This invention relates to a heavy-duty pneumatic radial tire with improved belt durability under high-speed driving conditions. [Prior Art] Conventionally, heavy-duty pneumatic radial tires for trucks, buses, small trucks, etc. have a carcass layer between the tread 2 of the tire 1 and the carcass layer 3, as shown in FIG. As the first belt layer adjacent to 3, a belt reinforcing layer ₄₁ having a cord angle of 40° to 75° with respect to the tire circumferential direction is arranged mainly for the purpose of ensuring cross-sectional bending rigidity in the tire width direction. As the second and third belt layers laminated on the upper surface of reinforcement layer 4 ₁ , the cord angle with respect to the tire circumferential direction is 10, mainly for the purpose of ensuring dimensional stability in the tire circumferential direction against tire filling air pressure. Two layers of belt tension-resistant layers 4 ₂ , 4 ₃ with cords intersecting each other between layers at ° ~ 30 °
The belt layer 4 is constructed by arranging them in a laminated manner, and further arranging a fourth belt tension-resistant layer ₄₄ as necessary. The carcass layer 3 is made up of one or more layers, and the carcass cord is arranged at approximately 90° (substantially in the radial direction) with respect to the tire circumferential direction. This type of heavy-duty radial tire has one belt reinforcement layer 4 ₁ and two belt tension-resistant layers 4 ₂ , 4 .
₃ , and the belt layer 4 is composed of at least three layers in total. The more belt layers 4 there are, the better the durability will be. However, if there are too many belt layers, it will become excessive equipment, which will be detrimental to economic efficiency, and will also increase the tire weight. It is becoming a choice. However, in the conventional heavy-duty radial tire shown in FIG. 5, the first belt reinforcing layer ₄₁ is arranged over almost the entire crown area, so that the cross section in the tire radial direction (tire width direction) is This tire has increased bending rigidity and is highly effective in uneven wear resistance, but on the other hand, when driving on rough roads, it is difficult for the tread surface to follow changes in irregularities such as stones and protrusions. There were disadvantages such as damage to the tread in the central region of the crown due to stress concentration caused by this, and the tendency for cords to break in the belt layer. Therefore, in order to improve these drawbacks, a so-called split structure is adopted in which the belt reinforcing layer ₄₁ is separated from the crown center region in the range of 25 to 45% of the tread ground contact width and is divided into two parts on both shoulder parts. A tire having the structure shown in FIG. 6, which reduces the radial cross-sectional bending rigidity of the central region of the crown, which is susceptible to stress concentration, to provide flexibility and relieve stress, is mainly used for use on rough roads. However, when tires with this structure are driven at high speeds on paved roads, the belt reinforcement effect in the central region of the crown decreases, causing instability in the shape of the crown (particularly an increase in the outer circumference growth in the central region of the crown). Another problem is that the strain between the belt tension-resistant layers 4 ₂ and 4 ₃ , which are the second and third belt layers, gradually increases, which can eventually lead to separation failure at the end of the belt layer. was left behind. [Object of the Invention] The object of the present invention is to provide the first belt reinforcing layer on the carcass layer side with a split structure to ensure the durability of the crown portion on rough roads, and to improve the durability of the belt when running at high speed on paved roads. To provide a heavy-duty pneumatic radial tire with greatly improved performance. [Structure of the Invention] To achieve the above object, the heavy-duty pneumatic radial tire of the present invention includes, on the outside of the carcass layer,
Counting from the carcass layer in the tread direction, a belt layer consisting of a metal cord having a cord angle of 40° to 75° with respect to the tire circumferential direction is placed in a range of 25 to 45% of the tread contact width in the central region of the crown. The second and third belt layers are made of metal cords, which are separated from each other and arranged separately on both shoulder parts, and the second and third belt layers are made of metal cords each having a cord angle of 10° to 30° with respect to the tire circumferential direction. In a heavy-duty pneumatic radial tire including a belt structure arranged in such a manner that the belt structure is arranged so as to or more organic fiber cord layers are arranged with substantially the same thickness as the first belt layer, and the total strength of the cords included per 1 cm width of the organic fiber cord layer is 240 kg or more. That is. By creating a split structure in which the first belt layer made of metal cords is spaced apart from each other in the central region of the crown, the radial cross-sectional bending rigidity of the central region of the crown, which is susceptible to stress concentration due to protrusions, is lowered. While ensuring the durability of the crown part on rough roads, organic fiber cord layers with a total cord strength of 240 kg or more per 1 cm width are installed between the first split belt layer at a cord angle. Because they are arranged at an angle of 0° to 10°, the growth of the outer periphery at the center of the crown is suppressed, greatly improving dimensional stability during high-speed driving on paved roads, and preventing separation failure at the end of the second and subsequent belt layers. can be prevented and belt durability can be improved. Hereinafter, the configuration of the present invention will be explained in detail with reference to the drawings. FIG. 1 is an explanatory half-sectional view in the calf line direction showing an example of the essential parts of the radial tire of the present invention. Also,
FIG. 2 is an enlarged cross-sectional explanatory view of the main part. 1 and 2, in a tire 1, a belt layer 4 made of metal cords is arranged between a carcass layer 3 and a tread 2. As shown in FIGS. This belt layer 4 consists of at least three layers, counting from the carcass layer 3 toward the tread 2: a first belt layer 4a, a second belt layer 4b, a third belt layer 4c, and 4th belt layer 4d
Consisting of Note that one or more carcass layers 3 may be arranged. The second belt layer 4b and the third belt layer 4c each have cords in the tire circumferential direction.
The layers intersect each other at an angle of 10° to 30°.
These belt layers 4b and 4c bear tension in the tire circumferential direction against high air pressure. Further, the first belt layer 4a is spaced apart from each other in the crown center region T, and is disposed in both shoulder portions S, S, respectively. This first belt layer 4a has a cord angle of 40° to 75° with respect to the tire circumferential direction, and serves to improve the bending rigidity in the tire width direction, and is particularly designed to strengthen the shoulder portion. . The distance W that separates the first belt layer 4a from each other in the crown center region T is 25 of the tread ground contact width.
~45% range. If it is less than 25%, it is not possible to lower the radial cross-sectional bending rigidity of the crown central region T, which is susceptible to stress concentration, to provide flexibility, and to alleviate stress.On the other hand, if it exceeds 45%, the This is because the reinforcing effect of the first belt layer 4a is reduced and uneven wear is likely to occur in the shoulder portion S. Between the first belt layer 4a split left and right, the cord angle with respect to the tire circumferential direction is between 0° and 4a.
One or more organic fiber cord layers 5 with a thickness of 10° are arranged to have substantially the same thickness as the first belt layer 4a, and the total strength of the cords included per 1 cm width of the organic fiber cord layer 5 is 240 kg. That's all. The number of organic fiber cord layers 5 is not particularly limited, and is determined by the relationship between the thickness of the organic fiber cord layer 5 itself and the thickness of the first belt layer 4a. As described above, by separating the first belt layers 4a from each other in the crown central region T, that is, by adopting a split structure, the crown central region T, which is particularly susceptible to stress concentration due to irregularities such as stones and protrusions on the road surface, is improved. The bending stiffness in the radial direction of the tire is lowered to ensure a stress relaxation effect, and at the same time, the organic fiber cord layer 5 is interposed in the empty central region T of the crown to enhance the reinforcing effect in the tire circumferential direction, which is different from the conventional split structure. This prevents the dimensional stability of the tread portion from decreasing due to a decrease in the reinforcing function of the belt layer in the central region of the crown, which was a drawback in the prior art. For example, nylon cords, polyester cords, aromatic polyamide fiber cords, etc. are used as reinforcing cords for the organic fiber cord layer 5 to obtain such effects, and the lower the cord angle with respect to the tire circumferential direction, the better. It is preferably less than 5°, preferably less than 5°. Further, the total strength F of the cords included per 1 cm width of the organic fiber cord layer 5 is 240 kg or more, preferably 300 kg or more. Here, the total strength F refers to the product of the number of cords inserted per unit width and the cord strength, and is expressed by the following formula. F=Σni fi F: Total strength, ni: Number of cords inserted per 1 cm width of organic fiber cord layer (1/cm), fi: Breaking strength of organic fiber cord (Kg). Fourth belt layer 4d arranged as the outermost layer
is a protective layer that protects the third belt layer 4c from external damage, etc., and is arranged with a width that corresponds to the tread ground contact width as necessary. Steel cord, aromatic polyamide fiber cord (trade name) Kepler) and other codes. The cord angle is 10° to 30° with respect to the tire circumferential direction. An experimental example is shown below. Experimental Example 1 The following prototype tire was produced and the durability of the belt portion was evaluated. Prototype tire Tire size 10.00R20. The belt part structure shown in FIG. Organic fiber cord layer; 1260 D/2, 8.4
Book/cm x 2 plies (both plies arranged in the direction crossing the second belt layer 4b), F=336Kg/
cm, various angles changed. Toledo ground contact width 185mm. 1st
The mutual spacing of the second belt layer 4a is 60 mm. The specifications of the belt layer are as shown in Table 1 below.

〔Effect of the invention〕

As explained above, according to the present invention, by forming the first belt layer made of metal cords into a split structure in which they are spaced apart from each other in the central region of the crown, durability of the crown portion on rough roads is ensured, and By arranging an organic fiber cord layer with a total cord strength of 240 kg or more per 1 cm width between the first left and right belt layers at a cord angle of 0° to 10°, the vehicle can run at high speed on paved roads. The belt durability can be greatly improved by improving the dimensional stability of the belt.

[Brief explanation of the drawing]

FIG. 1 is an explanatory half-sectional view in the meridian direction showing an example of the main part of the radial tire of the present invention, and FIG. 2 is an enlarged explanatory view of the main part. FIG. 3 is a diagram showing the relationship between the cord arrangement angle of the organic fiber cord layer and the growth of the tire outer circumference, and FIG. 4 is a diagram showing the relationship between the total strength in the cord direction of the organic fiber cord layer and the tire outer circumference growth. FIG. 5 and FIG. 6 are explanatory half-sectional views in the meridian direction, respectively, showing an example of a main part of a conventional radial tire. 1...Tire, 2...Tread, 3...Carcass layer, 4...Belt layer, 4 ₁ ...Belt reinforcement layer,
4 ₂ , 4 ₃ , 4 ₄ ... Belt tension-resistant layer, 4a ... First belt layer, 4b ... Second belt layer, 4c ... Third belt layer, 4d ... Fourth
th belt layer, 5... organic fiber cord layer, S...
...Shoulder part, T...Crown center area.

Claims (1)

[Scope of Claims] 1. On the outside of the carcass layer, a belt layer consisting of a metal cord having a cord angle of 40° to 75° with respect to the tire circumferential direction is placed at the first belt layer counting from the carcass layer in the tread direction, at the center of the crown. In the area, the cords are separated from left and right in the range of 25% to 45% of the tread contact width, and are placed separately on both shoulder sections, and the second and third cords are placed at an angle of 10° to 30° with respect to the tire circumferential direction. In a heavy-duty pneumatic radial tire including a belt structure in which belt layers made of metal cords are arranged so as to intersect with each other between the layers, the tire One or more organic fiber cord layers having a cord angle of 0° to 10° with respect to the circumferential direction are arranged to have substantially the same thickness as the first belt layer, and are included per 1 cm width of the organic fiber cord layer. A pneumatic radial tire for heavy loads, characterized by a total cord strength of 240Kg or more.