JPH0115403B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a radial tire, and more specifically, by using a specific nylon cord as a reinforcing cord of a layer made of fiber material laminated on the outermost layer of a belt layer, productivity is excellent and the uniformity of the tire is improved. It concerns a significantly improved radial tire. In recent years, the development of expressway networks has been remarkable, and the performance of vehicles has also improved significantly. Along with this, the performance requirements for tires are becoming increasingly strict, such as the requirement for HR performance tires to replace conventional SR performance tires. Therefore, in HR specification radial tires that require high-speed performance, in order to prevent the tire shoulder from rising due to centrifugal force during driving, the outermost layer of the belt layer has a reinforcing cord with a cord angle of 0. This is dealt with by laminating and arranging layers (hereinafter referred to as belt cover layers) made of fiber material with an angle of 10° to 10°. Nylon cords, which have excellent adhesion to rubber and fatigue resistance, have recently been widely used as reinforcing cords for the belt cover layer. However, as mentioned above, since the reinforcing cords of the belt cover layer are arranged at an angle of 0° to 10° with respect to the tire circumferential direction, the splices have no choice but to overlap at their ends, causing tire damage. Non-uniform portions are formed in the circumferential direction. Furthermore, when the belt cover layer, which is located closest to the dredged surface of the tire among the tire constituent materials, is composed of nylon cord, which has a large heat shrinkage at high temperatures among other reinforcing fiber cords, the tire After vulcanization, the amount of heat shrinkage at the splice portion of the belt cover layer (made of nylon cord) varies significantly. That is, the reinforcing cord of the belt cover layer contracts after vulcanization, and this heat shrinkage stress acts as a force in the direction of reducing the outer diameter of the tire. The amount (number) of reinforcing cords in the splice part is about twice that of other parts, and as a result, even though the heat shrinkage stress of each unit reinforcement cord is the same, the heat shrinkage stress of the splice part is higher than that of other parts. As a result, the outer diameter of the tire becomes smaller at the splice than at other locations, deteriorating the uniformity of the tire. In order to solve the above-mentioned problem, conventionally, in the tire molding process, after the tire is removed from the vulcanizing can, internal pressure is applied to the tire to prevent heat shrinkage of the nylon cord that constitutes the belt cover layer. Although so-called post-cure inflation (hereinafter referred to as PCI), which cools tires to room temperature, is being implemented, its effectiveness is still insufficient, and maintaining internal pressure only for the purpose of cooling tires significantly impedes productivity. In addition, there are currently problems such as complicating the mechanism of the vulcanizer. The present invention was developed as a result of studies aimed at solving the above-mentioned problems. Therefore, an object of the present invention is to eliminate the need for PCI, improve productivity, and improve tire uniformity by specifying the characteristics of the nylon cord used as a reinforcing cord for the belt cover layer, that is, the layer made of fiber material. The objective is to provide a radial tire that can significantly improve the That is, the present invention comprises a pair of left and right bead portions, a pair of left and right sidewall portions connected to the bead portions, and a tread portion located between the sidewall portions, and a tire is provided between the pair of left and right bead portions. A carcass layer with a cord angle of 70° to 90° with respect to the circumferential direction is mounted, and a cord angle with respect to the tire circumferential direction is mounted on the carcass layer in the tread portion.
A plurality of belt layers intersecting each other at an angle of 10° to 30° are arranged, and on the outermost layer of the belt layer, at least one layer of fiber material with a reinforcing cord having a cord angle of 10° or less with respect to the tire circumferential direction is formed. In a radial tire with laminated layers, the reinforcing cord of the layer made of the fiber material has an elongation rate E (%) of 7.0≦ when subjected to a load of 2.7 g/denier.
6 nylon cord which is in the range of E≦14.0 and whose dimensional stability index D expressed as the product of elongation rate E (%) and heat shrinkage stress S (g/denier) is in the range of 1.4≦D≦1.8. Or, its gist is a radial tire characterized by the use of 66 nylon cord. The present invention will be specifically described below with reference to the drawings. FIG. 1 is an explanatory half-sectional view of a radial tire according to an embodiment of the present invention, and FIG. 2 is an explanatory plan view showing a carcass layer, a belt layer, and a layer made of fiber material. In the figure, 1 is a tread part, 2 is a sidewall part provided so as to extend on both sides of this tread part 1, 3 is a bead part provided along the circumferential direction at the lower end of this sidewall part,
31 is a bead wire buried in this bead portion 3. The reinforcing cord 4a is wrapped around the bead wire 31 and the bead filler 6 at both ends and along the inner surfaces of the sidewall portion 2 and the tread portion 1 in the tire circumferential direction.
A carcass layer 4 having a cord angle of 70° to 90° with respect to EE′ is provided, and a plurality of belt layers 5 are interposed between the carcass layer 4 and the tread portion 1. A layer 7 (hereinafter referred to as belt cover layer 7) made of a fiber material is laminated on the outermost layer 5u of the belt layer 5. In this embodiment, the carcass layer 4 has a two-layer laminated structure including an outer carcass layer 4u and an inner carcass layer 4d, and the belt layer 5 also has a two-layer structure including an outer belt layer 4u and an inner belt layer 4d. It has a laminated structure. The tire circumferential direction of the reinforcing cord 5a in each belt layer constituting this belt layer 5
The angle with respect to EE' is 10° to 30°, and the reinforcing cords 5a of the outer and inner belt layers 5u and 5d are arranged so as to cross each other. Further, a belt cover layer 7 laminated on the outer belt layer 5u of the belt layer 5 described above, that is, the outermost layer 5u.
is composed of one layer in this example,
The reinforcing cords 7a of the belt cover layer 7 are arranged at an angle of 0° to 10° with respect to the tire circumferential direction. Note that in FIGS. 1 and 2, the belt cover layer 7 looks as if it is a two-layer stack, but this is because the splice portion of the belt cover layer 7 is shown; Thus, the belt cover layer 7 is one layer. Therefore, 7u in the figure indicates the end of the outer belt cover layer at the splice portion. In the present invention, the elongation rate E (%) of the reinforcing cord 7a of the belt cover layer 7 when subjected to a load of 2.7 g/denier is 7.0≦E≦14.0.
6 nylon cord or 66 nylon cord whose dimensional stability index D expressed as the product of elongation rate E (%) and heat shrinkage stress (g/denier) is within the range of 1.4≦D≦1.8. is used. FIG. 3 is a graph showing the relationship between heat shrinkage stress S and elongation E (%) at a load of 2.7 g/denier (hereinafter referred to as intermediate elongation). Here, the heat shrinkage stress S is the shrinkage force during dry heat according to JIS L-1017, and the measurement conditions are in an atmosphere of 170°C. Further, the intermediate elongation E is the elongation rate under a load of 2.7 g/denier in a constant speed elongation type tensile test according to JIS L-1017. Furthermore, curve A in Figure 3 indicates dimensional stability index D=
1.5 low shrinkage nylon cord, curve B is a conventional nylon cord with dimensional stability index D=2.0. As is clear from the figure, the heat shrinkage stress S and the intermediate elongation E
is inversely proportional, but in the present invention D=1.5
It can be seen that under any E, the low heat shrinkage nylon cord has a significantly smaller S than the conventional nylon cord with D=2.0. Here, regions where E is less than 7.0 cannot be expressed in nylon cord. Further, in a region where E exceeds 14.0, the belt cover layer elongates significantly during running, and the shoulder portion rises significantly, making it impossible to maintain high-speed durability. Dimensional stability index D (g/
d) is defined by the following equation. D=S×E That is, a small value of D means that this belt cover layer is difficult to stretch and has a small heat shrinkage stress at high temperatures. In other words, this belt cover layer is exposed to high temperatures during vulcanization, and when the internal pressure drops to atmospheric pressure after vulcanization, the belt cover layer contracts due to heat shrinkage stress. Nylon cord has a significantly smaller amount of heat shrinkage, so
Even if the PCI process is omitted, the amount of heat shrinkage of the reinforcing cord is small, and the uniformity of the tire can be significantly improved.
It has become clear that the tire exhibits performance that is as good as, if not better than, the uniformity of tires that have gone through the process. In order to further improve this effect, it is desirable that the value of D be 1.4≦D≦1.7. The effects of the present invention will be specifically explained below with reference to Examples. Example 1 As shown in Figures 1 and 2, 195/70HR14 has a belt cover layer laminated on the outermost layer of the belt layer.
We created tires using the materials shown in Table 1 below for the reinforcing cord of the belt cover layer of radial tires for passenger cars, with and without PCI processing. As a result of the measurement, the measurement results shown in Table 2 were obtained. Uniformity was measured using the JASO C607 measurement method.

【table】

[Table] As is clear from the table, tires that use normal nylon cord as the reinforcing cord for the belt cover layer have a large RFV value, and tires that use normal nylon cord without PCI processing have a particularly high RFV value.
The value of is significantly large. In contrast, the tire of the present invention has an RFV value smaller than that of a tire using conventional nylon cord even without PCI processing, and even without PCI processing, the RFV value of the tire using conventional nylon cord It can be seen that the effect is as good as that of a tire with PCI applied to the cord. As described above, the present invention provides a reinforcing cord of 2.7 mm as a reinforcing cord for a belt cover layer, that is, a layer made of fiber material.
Elongation rate E (%) when subjected to a load of g/denier
is in the range of 7.0≦E≦14.0, and the growth rate E
The dimensional stability index D expressed as the product of (%) and heat shrinkage stress (g/denier) is 1.4≦D≦1.8
By using 6 nylon cord or 66 nylon cord, which is in the range of can do.

[Brief explanation of drawings]

FIG. 1 is a half-sectional explanatory diagram of a radial tire according to an embodiment of the present invention, FIG. 2 is a plan view explanatory diagram showing the carcass layer, belt layer, and layers made of fiber material, and FIG. 3 is a heat shrinkage stress S It is a graph showing the relationship between elongation rate E (%) at a load of 2.7 g/denier. 1...Tread section, 2...Side wall section,
3... Bead portion, 4... Carcass layer, 5... Belt layer, 6... Bead filler, 7... Layer made of fiber material, 7a... Reinforcement cord of layer made of fiber material.

Claims (1)

[Claims] 1 Consists of a pair of left and right bead parts, a pair of left and right sidewall parts connected to the bead parts, and a tread part located between the sidewall parts, and between the pair of left and right bead parts, there is a cord in the tire circumferential direction. A carcass layer with an angle of 70° to 90° is mounted,
Furthermore, on the carcass layer in the tread part, multiple belt layers are arranged which intersect with each other at cord angles of 10° to 30° with respect to the tire circumferential direction. At least 1 with a cord angle of 10° or less
In a radial tire in which layers made of fiber material are laminated, the reinforcing cord of the layer made of fiber material has an elongation rate E (%) of 7.0≦E≦14.0 when subjected to a load of 2.7 g/denier. The dimensional stability index D is within the range of and is expressed as the product of elongation E (%) and heat shrinkage stress S (g/denier)
A radial tire characterized by using a nylon 6 cord or a nylon 66 cord in the range of 1.4≦D≦1.8.