JPS5989203A - Radial tire for passenger car - Google Patents

Abstract

PURPOSE:To improve the productivity of a tire and its appearance ever so better as well as to aim at a distinct improvement in its durability, by using such a nylon cord as having an elongation percentage in the specified range and a size stability index, as a reinforcing cord for a carcass layer. CONSTITUTION:A reinforcing cord 4a for a carcass layer 4 of a radial tire available for passenger cars has an elongation percentage E% in a range of 7.0<=E<= 14.0 in time of receiving a load of 2.7/denier and uses a 6 or 66 nylon cord in a range of 1.4<=D<=1.8 in terms of a size stability index D being expressed as the product of the elongation percentage E% and heat shrinkage stress g/denier. Since this low heat shrinkable nylon is able to offer stability in a product size and eliminate a fear of any damage to the appearance of a tire stemming from the unevenness produced on tire side parts. Therefore, both productivity and durability are improved in a package manner.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radial tire for a passenger car, and more particularly, the present invention relates to a radial tire for a passenger car, and more particularly, the present invention relates to a radial tire for a passenger car. This invention relates to a radial tire for passenger cars that has been improved and has excellent durability.

Nylon cord has recently come to be used as a reinforcing cord for the carcass layer, which is a component of radial tires for passenger cars, because it has excellent fatigue resistance, low heat generation, and adhesion to rubber.

However, since nylon cord has high heat shrinkage,
If the tire is exposed to high temperatures during vulcanization, it will shrink after the can is opened, and this shrinkage will disrupt the dimensions of the tire.Furthermore, the splice part of the carcass layer, which is essential for tire molding, is Relationship 1: Even if the heat shrinkage stress of each unit reinforcement cord is the same, the heat shrinkage stress increases as the number of cords increases, and as a result, the side In some cases, four parts appeared on the parts, which affected the appearance.

Therefore, in order to solve the above-mentioned problems, 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 makes up the cursive layer while keeping the tire at room temperature. Although so-called post-cure inflation (hereinafter referred to as PCI) has been implemented, the effect is still insufficient, and maintaining internal pressure solely for the purpose of cooling the tire has problems such as significantly hindering productivity. That is the current situation.

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 specify the characteristics of a nylon cord used as a reinforcing cord for a carcass layer.
To provide a radial tire for a passenger car that does not require PCI, improves productivity, improves the appearance of the tire, and has excellent durability.

That is, the present invention uses two reinforcing cords for the carcass layer.
．． Elongation rate E (%) when subjected to a load of 7t/denier
is in the range of 7.0≦E≦14.0, and the elongation rate E
6 nylon cord or halo 6 nylon cord whose dimensional stability index, expressed as the product of (%) and heat shrinkage stress (denier), is in the range of 1.4≦D≦1.8. Radial tires for passenger cars that are characterized by
This is the summary.

The present invention will be specifically described below with reference to the drawings.

FIG. 1 is a half-sectional explanatory diagram of a radial tire for a passenger car according to an embodiment of the present invention.

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, 6 is a bead part provided along the circumferential direction at the lower end of this sidewall part, 61 is a bead wire buried in this bead portion 6. Wrap the bead wire 61 and bead filler 6 at both ends,
A carcass layer 4 is provided along the inner surfaces of the sidewall portion 2 and the tread portion 1, and the reinforcing cord 4a has a cord angle of 70° to 90° with respect to the tire circumferential direction EE'. A plurality of belt reinforcement layers 5 are interposed between the layer 4 and the tread portion 1. The carcass layer 4 is composed of only one layer, whereas the belt reinforcing layer 5 is composed of two layers: an upper belt reinforcing layer 5u and a lower belt reinforcing layer 5d in this embodiment.
It has a layered structure.

The angle of the reinforcing cord 5a in each belt reinforcing layer constituting the belt reinforcing layer 5 with respect to the tire circumferential direction EE'K is 15
° ~ 30 °, and the upper and lower belt reinforcement layers 5
The reinforcing cords 5a of u and 5d are arranged so as to intersect with each other.

In the present invention, the reinforcing cord 4a of the carcass layer 4 has an elongation rate E (%) in the range of 7.0≦E≦14.0 when subjected to a load of 2.7 f/denier,
And the dimensional stability index expressed as the product of elongation rate, E (%) and heat shrinkage stress (2/denier) is 1.4≦D.
6 nylon cord or 66 nylon cord in the range of ≦1.8 is used.

FIG. 2 is a graph showing the relationship between heat shrinkage stress S and elongation rate E (%) at a load of 2.7 f/denier (hereinafter referred to as intermediate elongation).

Here, the heat shrinkage stress S is the shrinkage force during dry heat according to JISL-1017, and the measurement conditions are under a 170'C atmosphere.

Moreover, the intermediate elongation E is the elongation rate under a load of 2.7 f/denier in a constant speed elongation type tensile test according to JISL-1017.

Further, in Fig. 2, curve A is a low-shrinkage nylon cord with a dimensional stability index of 1.5, and curve B is a dimensional stability index of D =
2.0 conventional nylon cord.

As is clear from the figure, the heat shrinkage stress S and the intermediate elongation E are inversely proportional, but the low heat shrinkage nylon with D = 1.5 in the present invention is better than the conventional nylon with D = 2.0 under any E. It can be seen that S is significantly smaller than the code.

Here, regions where E is less than 7.0 cannot be expressed in nylon cord.

Also, E is 14. In the region exceeding Ot-, the tire cord elongates rapidly during running, causing the tire to grow, making it impossible to maintain durability.

Dimensional stability index D (2) of reinforcing cord in carcass layer
/denier) is defined by the following formula: 0D=SXE In other words, a small value of D means that the reinforcing cord will elongate <<
, and indicates that the thermal shrinkage stress at high temperatures is small.

In other words, the reinforcing cords in the carcass layer are exposed to high temperatures during vulcanization, and when the internal pressure drops to atmospheric pressure after vulcanization, the reinforcing cords in the carcass layer shrink due to thermal shrinkage stress. The low heat shrinkage nylon resin according to the invention is D
Within the above range, even if the PCI process is omitted, the product dimensions will be stable, and there will be no risk of causing unevenness on the side of the tire and damaging the appearance.

To further improve this effect, D 1.4≦D≦1.7 It is desirable that

Hereinafter, the effects of the present invention will be explained in detail with reference to this example.

Example 1 1 with 2-brie nylon cord as carcass layer
A 95/70HR13 size radial tire for a passenger car was created using a low heat shrinkage nylon cord shown in Table 1 and a conventional nylon cord in the carcass layer, and the tire side part with and without PCI was prepared. The unevenness was compared. As a result, as shown in Table 2, the unevenness on the side of the tire using the nylon cord according to the present invention as a reinforcing cord for the carcass layer is smaller than that of tires subjected to conventional PCI processing, despite not being subjected to PCI processing. It showed excellent results.

Here, the unevenness on the tire side section refers to the maximum unevenness in the tire circumferential direction at the tire side section. The smaller the value, the better the condition.

As described above, the present invention uses 2.7? /Elongation rate E when subjected to a denier load (
%) is in the range of 7.0≦E≦14.0, and the dimensional stability index expressed as the product of elongation rate E (%) and heat shrinkage stress (f/denier) is ■, 4≦ D≦1.8
By using nylon 6 cord or nylon 66 cord, which falls within the range of It is possible to improve the quality and also improve the durability.

[Brief explanation of drawings]

Fig. 1 is a half-sectional explanatory diagram of a radial tire for a passenger car according to an embodiment of the present invention, and Fig. 2 is a graph showing the relationship between heat shrinkage stress S and elongation rate E (%) under a load of 272/denier. It is. 1...Tread part, 2...Side wall part, 6...
- Bead portion, 61... Bead wire, 4... Carcass layer, 4a... Carcass layer reinforcement cord, 5... Belt reinforcing layer, 6... Bead filler. Agent Patent Attorney Shin Ogawa - Patent Attorney Ken Noguchi Patent Attorney Kazuhiko Saishita Figure 1 El Figure 2 E ('n)

Claims (1)

[Scope of Claims] A radial tire for a passenger car, characterized in that a 6-nylon cord or a 66-nylon cord having the following characteristics is used as a reinforcing cord of the carcass layer. 7.0≦E≦14.0 1.4≦D≦1.8 However, E is the elongation rate (chi) when subjected to a load of 2.7 g/denier, and D is the elongation rate E ( %) and heat shrinkage force S (2/denier).