JPH011605A - Radial tire for heavy loads - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a belt structure for a heavy-duty pneumatic radial tire, and more specifically to problems caused by forming the first belt layer into a split structure. , for example, reduces or prevents stress concentration in the central region of the crown due to irregularities such as stones and protrusions on the road surface, damage to the tread, and cord breakage of the belt layer inside the tire, thereby improving the durability of the crown under rough road conditions. This is a pneumatic pump for heavy loads that maintains the above-mentioned splint structure in good condition, without the lack of belt durability under highway conditions due to lack of dimensional stability, and without the deterioration of maneuverability and stability under heavy load conditions. Regarding radial tires.

[Prior art]

Conventionally, in heavy-duty pneumatic radial tires for trunks, buses, small trunks, etc., the tread surface side of the carcass layer 3 is used, for example, as shown in the plan development views of the heald portion of the tire in FIGS. 3 and 4, respectively. A belt reinforcing layer 41 (first belt layer) having a cord angle of 40'' to 756 with respect to the tire circumferential direction, which is arranged adjacent to this carcass layer 3, and this belt reinforcing layer N4. The cord angle with respect to the tire circumferential direction is 10" to 30"
At least two belt tension-resistant layers 4□ whose respective cords intersect each other at °.

4, (belts N at the second and third openings) are stacked and arranged. The carcass N3 in this case is composed of IN or two or more layers, and the carcass cord is approximately 90 degrees in the tire circumferential direction.
° (substantially radial direction).

However, in the radial tire shown in Figure 3, the first belt layer, belt reinforcement rM 41, is placed over almost the entire crown area to provide reinforcement against the tire filling air pressure, thereby ensuring dimensional stability. and also
By increasing the cross-sectional bending rigidity in the tire's radial direction (tire width direction) over the entire tread contact area, this tire exhibits excellent uneven wear resistance. It is difficult for the tread surface to follow changes in the tire surface, and the tread in the central region of the crown is easily damaged due to stress concentration caused by these irregularities, and the cords of the belt layer inside the tire tend to break. .

Therefore, in order to improve these drawbacks, belt reinforcement F
541 from the crown center area and 2 on both shoulders.
By adopting a so-called split structure in which the crown is arranged separately, the radial cross-sectional bending rigidity of the central region of the crown, which is easily susceptible to stress concentration, is lowered to provide flexibility and relieve stress. It is mainly used for business purposes.

However, with tires of this structure, this is unlikely to be a problem when used on rough roads where the running life is short, but when the running life is long such as on ships or at high speeds, the belt reinforcing effect in the central region of the crown decreases, resulting in the shape of the crown. (particularly an increase in peripheral growth at the center of the crown), the strain between the belt tension resistance N4□, 41, which is the second and third belt layer, gradually increases, and finally There remains another problem in that it is likely to lead to separation failure at the end of the belt layer.

[Purpose of the invention]

The present invention was made in view of the above-mentioned circumstances, and by significantly improving the dimensional stability while ensuring the durability of the crown part on rough roads, the belt durability under high-speed road usage conditions is improved. The purpose of the present invention is to provide a pneumatic radial tire for heavy loads that ensures the following.

[Structure of the invention]

For this reason, the present invention provides a radial tire in which at least three layers of belts 11 made of metal cords are arranged between the carcass layer and the tread, and which meets the following requirements (1) and (2).
), (3) and (4) A pneumatic radial tire for heavy loads that satisfies (3) and (4).

(1) The first belt a counting from the carcass layer in the tread direction is spaced apart from each other in the crown center area and placed on both shoulder parts, and the cord angle of the first belt layer with respect to the tire circumferential direction is 40″～7
(2) The cords of the second belt layer and the third belt layer counting from the carcass layer in the tread direction are respectively 10° to 3° with respect to the tire circumferential direction.
(3) The cord angle between the carcass layer and the second belt layer in the central region of the crown with respect to the tire circumferential direction is O@~10''.
An organic fiber cord layer of IN or more is arranged, and the total strength of the cord of this organic fiber cord layer is 240 kg/unit width.
cm or more, and (4) the cords on both sides of the first belt layer are arranged symmetrically with respect to the tire center.

Hereinafter, the configuration of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a sectional view of a tire crown showing an example of the radial tire of the present invention, and FIG. 2 is a developed plan view of a belt portion thereof.

In FIGS. 1 and 2, in a tire 1, a belt layer 4 made of a metal cord is interposed between a carcass layer 3 and a tread 2.
is located.

This belt PJ4 is made of at least 3N, and in the figure, counting from the carcass layer 3 to the tread 2, includes a first belt layer 41, a second belt layer 4b, a third belt layer 4e% and a fourth belt layer. It is composed of the belt N4d.

Note that one or more carcass layers 3 may be arranged.

In the tire according to the present invention, the first belt layer 4 is separated from each other in the crown center region T, that is, it has a split structure, so that the crown can easily receive stress concentration due to irregularities such as stones and protrusions on the road surface. This lowers the tire radial cross-sectional bending rigidity in the center region T to ensure a stress relaxation effect.

At the same time, in order to prevent a decrease in the dimensional stability of the tread portion due to a decrease in the reinforcing function of the belt layer in the central region of the crown, which was a drawback of the conventional split structure, the first belt layer 41 is spaced apart from each other. An organic fiber cord N5 is interposed between the carcass N3 and the belt N4b in the crown central region T, which is a gap, to enhance the circumferential reinforcing effect.

However, the cord angle of the first belt layer provided on both shoulder parts of this splint structure is 40 to 75 degrees.
Must be within the range. In other words, although the cord angle of the first belt layer is related to other requirements, if the cord angle is less than 40', it will not have the effect of increasing the bending rigidity in the cross-sectional direction of the tire, and will reduce the shoulder drop wear of the tire shoulder. On the other hand, if it exceeds 75'', it has no effect on increasing the rigidity in the tire circumferential direction, and the bending rigidity in the cross-sectional direction of the tire becomes too high, reducing the belt edge separation resistance on rough roads, which is undesirable. .

In addition, the cord arrangement angle of the second belt t-i and the third belt layer, which intersect each other with respect to the tire circumferential direction, must be within the range of 10 to 30''. If the cord arrangement angle of the second and third belt layers is less than 100, it will not be effective as a so-called bias lamination and the steering stability will deteriorate, and if it exceeds 30'', it will not work as a tension-resistant layer of the belt. This is not desirable because it will not be able to fulfill its role.

In the present invention, it is preferable that the interval W separating the first belt layer 41 from each other in the crown center region T is in the range of 25 to 45x of the tread contact width. This is because 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 shoulder parts s, 'The first belt N4. This is because the reinforcing effect is reduced and uneven wear is likely to occur in the shoulder portion S.

The organic fiber cord layer 5 is preferably composed of IN in terms of molding and productivity.

Examples of this organic fiber include nylon, polyester fiber, polyarylate fiber, and aromatic polyamide fiber (aramid).

The cord angle of the organic fiber cord layer 5 with respect to the tire circumferential direction is preferably a low angle in order to ensure dimensional stability, and is preferably in the range of 0'' to 10'', preferably substantially 0' in terms of dimensional stability. (circumferential direction). Further, the total strength of the organic fiber cord JW5 is preferably 240 Kg/cm or more per unit width, preferably 300 Kg/cm or more from the viewpoint of dimensional stability. Here, the total strength 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 ri F: Total strength, ni: Number of cords inserted per unit width of organic fiber cord (1/cm), f: Breaking strength of organic fiber cord (Kg).

Fourth belt layer 4. is arranged as a protective layer when necessary, and is made of cords such as steel cords and aromatic polyamide fiber cords (trade name: Kevlar).The cord angle is 10° to 30° with respect to the tire circumferential direction.
It is.

One of the features of the present invention is the requirement (4), that is, the first
This is because the cords on both sides of the first belt layer are arranged symmetrically with respect to the tire center.

The technical effects and effects of this requirement (4) will be explained below.

Generally, when a vehicle goes around a curve, a centripetal force acts on the tires on the ground surface in opposition to centrifugal force, and this centripetal force is called cornering force. When a cornering force acts on this ground contact surface, in-plane bending rigidity acts on this ground contact surface, and at this time, the ground contact surface of one tire is divided into a tension side and a compression side.

Therefore, when a tensile force is applied to a two-layer laminate in a vehicle, the resistance force is greater when the two-layer laminate is stacked in a bias (cross) manner, so on the tension side, the first belt layer and the second
It is preferable to arrange the belt layers so that the cord orientations of the second belt layer cross each other.

In addition, on the compression side of the contact surface, the resistance force increases due to the incompressibility of rubber, so on the compression side, the cord orientation of the first bell +-i and the second bell 1- layer is It is better to have the same inclination (parallel). These different forces on the tension side and compression side cause the cord orientation of the first belt layer to be symmetrical between the splint layers on both sides.
That is, balance can be achieved by arranging both ends of the first belt layer symmetrically with respect to the tire center as defined in requirement (4) of the present invention.

An experimental example is shown below.

Experimental Example 1 The following three types of tires of the present invention, a control tire, and a comparison tire were each produced as prototypes, and the durability of the belt portion was evaluated. In addition,
The tire size is 10.00 R2014PR rib pattern.

Hon λ” and 1 person i The belt part structure shown in FIG.

Organic fiber cord layer: 1890D/2 nylon, number of implants: 9.2 pieces/cm, arrangement angle: O'' with respect to the circumferential direction, mutual separation W of the first belt layer 43: 60 mm
.

In addition, the cord structure of each heald layer, the number of implants (1/c
m), belt arrangement direction, width (mm), and angle (6) are shown in Table 1.
As shown.

Anti-stop cup Tires with different belt placement directions as shown below.

1st belt, downward to the left/2nd belt, downward to the left 3rd belt, downward to the left 4th belt, downward to the right A conventional tire that is downward to the right Same as the tire of the present invention except that the first belt is a full type. The direction of the first belt is downward to the left, and the width is 16
It is 0 mm.

Slalom test using two indoor rotating drum test machines.

Speed: 45 Km/hr, Rim: 7.50 VX 20 A, P 7.25
Kgf/cm”, slip angle: ±2° variation by sine wave, load: 5χ every 24 hours from 2700Kg
Step up step by step.

The running results are shown in Tables 2 and 3.

Maneuvering stability evaluation: Actual vehicle evaluation on test course (feeling test) Vehicle: 2-D two-axle large truck, Rim: 7.00TX20, Air pressure: 7.2 Kgf/cm”, Load: Front axle 5.2 ton /axis, rear axis 9.Oton/axis.

As shown in Tables 2 and 4, by adopting the tire structure of the present invention, linear cornering force can be obtained in response to load fluctuations, and the magnitude of yaw and convergence, which are problems for large vehicles especially when changing lanes, can be reduced. It was confirmed that there was an improvement.

Table 1 Table 2 Table 3 1B, 213.3B indicate the first, second and third belt layers, respectively.

Table 4 1) Comments from two panelists.

The evaluation score is out of 10.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to increase (improve) steering stability while maintaining good belt durability.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the tire crown showing one example of the radial tire of the present invention, Fig. 2 is a plan development view of the belt part thereof, and Figs. 3 and 4 are the belt parts of a conventional tire and a comparative tire, respectively. FIG. DESCRIPTION OF SYMBOLS 1... Tire, 2... Trend, 3... Carcass layer, 4... Belt layer, 48... First belt layer, 45... Second belt layer, 4c. ...3rd belt layer, 44...4th bell) FJ, 5...
・Non-extensible fiber cord layer, S, S''...shoulder part, T...crown central area. Agent: Patent attorney Shin Ogawa-

Claims (1)

[Claims] A radial tire in which at least three belt layers made of metal cords are arranged between a carcass layer and a tread, which satisfy the following requirements (1), (2), (3) and (4). A satisfying radial tire for heavy loads. (1) The first belt layer counting from the carcass layer in the tread direction is spaced apart from each other in the crown center area and arranged on both shoulder parts, and the cord angle of the first belt layer with respect to the tire circumferential direction is (2) The cords of the second belt layer and the third belt layer, counting from the carcass layer in the tread direction, are each 10° to 30° with respect to the tire circumferential direction. (3) between the carcass layer and the second belt layer in the central region of the crown, one or more layers of organic fibers having a cord angle of 0° to 10° with respect to the tire circumferential direction; (4) The cords on both sides of the first belt layer are arranged symmetrically with respect to the tire center. that it was placed in