JPH08484B2 - Spare tire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spare tire which can be reduced in weight without impairing the internal pressure retaining property.

[0002]

[Prior art]

With the increase in speed and performance of vehicles, even spare tires that are temporarily used during flat tires are required to have tire performance comparable to general tires. It is indispensable to maintain the internal pressure for a long period of time, and there is a demand for weight reduction of spare tires that are always loaded to improve fuel efficiency.

On the other hand, as a spare tire, there are a tire type tire having a carcass of a cross-ply structure in which carcass cords are crossed, and a radial tire type having a carcass of a radial arrangement and having a belt layer to enhance a hoop effect. However, in any type of spare tire, conventionally, a multifilament cord formed by twisting organic fiber filaments such as nylon is used as a carcass cord.

[0005]

[Problems to be Solved by the Invention]

[0006] However, Maruchifi ^La instrument code, for example 4.2 compared spare tire is a normal tire
Due to the high internal pressure of kgf / cm2, air permeates into the carcass over time, which tends to lower the tire internal pressure, and the permeation of air causes internal damage such as ply separation. It was also found that the tire durability was also reduced. Incidentally, conventionally, the inner liner on the inner surface of the tire has a relatively large thickness of 1 to 2 mm.

In the present invention, the carcass cord is made of nylon monofilament, and the inner liner has a wall thickness of 0.
The purpose of the present invention is to provide a spare tire that can be reduced in weight without sacrificing various tire performances based on 5 to 0.2 mm.

[0008]

According to the present invention, the carcass cord is folded back from the tread portion to the sidewall portion at the bead core of the bead portion and the carcass cord is 28 to 38 with respect to the tire equator.
From a carcass having a cross-ply structure having at least two carcass plies that are opposite to each other at an angle of °, and a belt ply using a belt cord made of an organic fiber, which is arranged outside the carcass in the tire radial direction and inside the tread portion. And a belt layer, the carcass cord is made of nylon monofilament, and an inner liner having a wall thickness of 0.5 to 0.2 mm is attached to the inner side of the carcass facing the tire cavity. .

[0009]

In the thus constructed spare tire, the carcass cord is made of a nylon monofilament cord having a low gas permeability, so that the inner liner attached to the inside of the tire has a wall thickness of 0.5 mm to 0 mm. ．
Even when formed as thin as 2 mm, the internal pressure does not drop and the tire weight can be reduced. In addition, nylon cords have better adhesion to rubber than aromatic polyamides and steel cords, reducing peeling during traveling.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In the figure, a spare tire 1 is provided with a bead portion 3 through which a bead core 2 passes, a sidewall portion 4 extending outward from the bead portion 3 in the tire radial direction, and a tread portion 5 connecting between upper ends thereof. A toroidal carcass 6 is bridged between the bead portions 3 and 3, and a belt layer 7 is arranged outside the tire radial direction and inside the tread portion 5.

The carcass 6 is formed by at least two carcass plies 6A and 6B in which carcass cords are arranged at an angle of 28 to 38 ° with respect to the tire equator, and in this example, two carcass plies 6A and 6B. , 6B carcass cords intersect each other. In the carcass 6, the body portion 6a extending from the tread 5 through the sidewall portion 4 to the bead portion 3 is provided with a turnback portion 6b for turning around the bead core 2 from the inside to the outside, and between the bead core 2 and
By arranging a bead apex 8 that extends radially outward from the bead portion 3, the range from the bead portion 3 to the sidewall portion 4 is reinforced.

As the carcass cord, a nylon monofilament cord is adopted. This is because it was found that the nylon monofilament cord had low gas permeability. It is known that this cord has excellent dimensional stability, good adhesion to rubber, and high fatigue resistance.

As the nylon monofilament cord, 1500d to 3500d cords are used, and the number of hammering is 35 to 50/5 cm.

An inner liner 9 made of halogenated butyl rubber is provided on the inner surface of the carcass 6 facing the inner cavity of the tire. This inner liner 9 has a thickness t of 0.5.
It is about 0.2 mm, which is half that of conventional tires.

The thickness t of the inner liner 9 means the length in the direction perpendicular to the carcass ply 6B in contact with the inner liner 9.

As a result, the weight can be reduced. In this way, even when the thickness is halved, the gas permeability of the monofilament cord forming the carcass cord is small, so that the internal pressure drop is reduced over a long period of time, enabling unexpected use, and from the carcass of air. It was found that the durability of the carcass can be maintained by preventing the permeation of the carcass.

The belt layer 7 is composed of one or two, in this example, two belt plies 7A ^and 7B that are adjacent to each other inside and outside. Further, each belt ply 7A, 7B has an elastic modulus of 20.
It consists of a cord array in which rubberized nylon belt cords of 0 kgf / mm 2 or more are arranged at an angle of 10 ° or more and 40 ° or less with respect to the tire equator.

The belt plies 7A and 7B are arranged such that the belt cords cross each other in different directions, so that a strong truss structure that intersects each other reduces the weight of the tire and the tread rigidity. To provide the required steering stability and driving performance.

The belt layer 7 has its ends lifted up from the carcass 6 as the carcass 6 is curved in the shoulder portion, and rises from the clinch apex 15 for reinforcing the bead portion 3 at the raised parts. Reinforcing layer 16 made of hard rubber forming part 4
Intervenes.

When an aromatic polyamide cord is used for the belt cord, as shown in FIG.
The distance A between the belt cords 7a and 7b of A and 7B is set to 0.
5 mm or more and 1 mm or less. As a result, the shear stress acting between the belt plies 7A and 7B and the shear stress concentrated at the ply ends can be effectively alleviated, and the aromatic polyamide fiber having poor rubber adhesiveness can be adopted.

When the distance A is less than 0.5 mm, the stress relaxation effect is inferior, and when it exceeds 1 mm, the movement between the belt plies 7A and 7B becomes excessive and the steering stability is lowered and the weight is increased.

When a nylon cord is used for the belt, the distance A may be 0.3 mm to 0.6 mm, and therefore, it is preferable to use the nylon cord for weight reduction.

Further, such a distance A can also be formed by interposing an independent intermediate rubber layer 12 between the belt plies 7A and 7B as shown by the one-dot chain line in FIG. A rubber material having a JIS A hardness of 75 ° or more and 85 ° or less is used for the stress relaxation.

Further, as shown by a chain line in FIG. 1, one or a plurality of band cords made of nylon fiber are formed on the belt layer 7 at 10 ° or less, preferably 5 ° or less with respect to the tire equator. It is also possible to cover the entire surface with the band layer 10 that is spirally wound continuously in the tire circumferential direction at an angle. As a result, lifting due to centrifugal force or the like associated with high-speed rotation can be suppressed, and peeling between plies can be reduced.

[0026]

[Specific example] Tire size 135/7 based on the specifications in Table 1
A 0R15 tire was prototyped based on the present invention, and the tire weight, steering stability, and durability of the prototype tire were compared with those of the comparative examples. The results are shown in Table 1 as an index with Comparative Example 1 being 100.

In Table 1, the smaller the index of tire weight, the lighter the weight, and the greater the index, the better the steering stability and durability.

[0028]

[Table 1]

[0029]

【The invention's effect】

As described above, the spare tire of the present invention is capable of reducing tire weight while maintaining various tire performances based on forming a carcass from nylon monofilament cords.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a tread portion.

[Explanation of symbols] 2 bead core 3 bead part 4 sidewall part 5 tread part 6 carcass 7 belt layer 7A, 7B belt ply 9 inner liner 10 band layer

Claims (1)

[Claims] 1. A cross ply having at least two carcass plies which are folded back from a tread portion to a sidewall portion at a bead core of a bead portion and in which carcass cords are inclined to each other at an angle of 28 to 38 ° with respect to a tire equator. A carcass having a structure, and a belt layer formed of a belt ply using a belt cord of an organic fiber and arranged on the tire radial direction outside of the carcass and inside the tread portion,
A spare tire in which the carcass cord is made of nylon monofilament, and an inner liner having a thickness of 0.5 to 0.2 mm is attached to the inner surface of the carcass facing the tire inner cavity.