JPH0596908A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To increase cord density of a belt layer to increase tread stiffness effectively. CONSTITUTION:A tire is provided with at least one sheet of carcass ply 3a comprising cords extending at angles of 25 to 90 deg. relative to circumferential direction of the tire and at least one layer of belt layer 4a comprising cords 4b and 4c extending substantially in circumferential direction of the tire. At least one layer of belt layer 4a with the same width as the width of a tread 5 is formed with two kinds of cords 4b and 4c, and a thermal shrinkage coefficient of the cord 4b at approx. 140 deg.C is set more than twice as large as that of the other cord 4c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reinforcing structure for a pneumatic tire, especially for a pneumatic tire for a motorcycle, and provides an effective increase in tread rigidity.

[0002]

2. Description of the Related Art As a conventional reinforcing structure for a pneumatic tire for a motorcycle, one kind of cord is provided on the outer peripheral side of a crown portion of a carcass composed of at least one carcass ply,
There is one in which at least one belt layer, which is formed by spirally winding in the tire circumferential direction, is arranged with one or a plurality of units as a unit, and such a pneumatic tire has a belt layer cord that is substantially a tire. Since it extends in the circumferential direction, the bending rigidity in the cross section in the width direction is low, and therefore,
It has a feature that the ground contact property of the tire tread is good.

[0003]

However, according to this prior art, there is a disadvantage that the road surface grip strength cannot be sufficiently increased due to insufficient rigidity of the tread surface when turning a heavy vehicle. .. Therefore, in order to increase the tread rigidity, it has been proposed to increase the arrangement density of the belt layer cords substantially extending in the tire circumferential direction as much as possible. Due to its own limitations, this still did not allow the tread stiffness to be increased satisfactorily.

The present invention has been made with the object of solving the problems of the prior art while still maintaining the advantages of the prior art. The object of the present invention is to increase the tread rigidity appropriately. By doing so, it is an object of the present invention to provide a pneumatic tire capable of effectively increasing the road surface grip force during turning travel without impairing the straight running stability of the vehicle.

[0005]

The pneumatic tire of the present invention comprises at least one carcass ply consisting of cords extending at an angle in the range of 25 ° to 90 ° with respect to the tire circumferential direction and substantially the tire circumferential direction. And at least one belt layer composed of cords extending in a direction, and in particular, at least one belt layer having a width substantially equal to the tread width is formed by two types of cords, and one of the cords is formed. The heat shrinkage rate at about 140 ° C is more than twice that of the other cord.

[0006]

The present invention has been made by paying attention to the fact that the tire is cooled through a heating process called vulcanization in its manufacture. In the tire of the present invention, the heat shrinkage force of the cord is utilized. , A cord with a high heat shrinkage disposed on the outer peripheral side of a cord with a low heat shrinkage is inserted between the cords with a low heat shrinkage, so that a high cord that cannot be realized by mechanical winding. By providing the density, it is possible to bring about an appropriate and sufficient increase in the tread rigidity, and in particular, it is possible to effectively increase the road surface grip force when the vehicle is turning.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view in the tire width direction showing an embodiment of the present invention, in which 1 is a pair of bead cores and 2 is a bead filler arranged on the outer peripheral side of each bead core. Reference numeral 3 denotes a carcass that extends between the pair of bead cores and winds each side end portion from the inside of the tire toward the outside, and 4 denotes a belt arranged on the outer peripheral side of the crown portion of the carcass 3. Indicates.

In the tire of this example, the carcass 3 is composed of one carcass ply 3a.
Are formed by ply cords that extend in pairs in the tire circumferential direction and extend at an angle within the range of 25 ° to 90 °. Also here
The belt 4 is formed of a single belt layer 4a having a width substantially equal to the width of the tread 5, and the belt layer 4a is formed of two types of cords 4b and 4c extending substantially in the tire circumferential direction. Here, the heat shrinkage of one type of cord 4b at about 140 ° C is 2% higher than that of the other type of cord 4c.
With a value more than double, the cords 4b, 4c have a very high arrangement density as a whole belt layer. By the way, such a belt layer 4a, for example, as a first layer, one or a plurality of cords 4c having a small thermal contraction rate is spirally wound in the tire circumferential direction, and then as a second layer, a large thermal contraction rate. By spirally winding one or more cords 4b in the same manner, and then by vulcanization molding after forming the tread 5, the second layer cord 4b having a large heat shrinkage rate can be further reduced by its heat shrinking force. It can be brought by getting in between the eye code 4c.

Therefore, the belt layer thus constructed
In 4a, not only when the cords 4b and 4c are neatly aligned with each other as shown in FIG. 2 (a), but also between the cords 4b and 4c as shown in FIG. 2 (b). There may be a mixture of a part that completely penetrates into and a part that does not. Also, as shown in FIG. 2 (c), the two types of cords may not necessarily be neatly interleaved.

According to the pneumatic tire as described above, the arrangement density of the belt layer cords 4b and 4c can be effectively increased, and the tread rigidity can be sufficiently and appropriately increased. It is possible to effectively increase the road surface grip force during turning travel without impairing the ground contact property when traveling straight ahead.

[0011]

[Comparative Example] A comparative test on straight running stability, road gripping force during turning, and tread rigidity between the inventive tire and the comparative tire will be described below.・ Invention tire size is 160/60 R 17, and the carcass is composed of one piece of carcass ply made of nylon cord (1260 d / 2) extending at 90 ° to the tire circumferential direction.
Aromatic polyamide cord with low heat shrinkage
(1500d / 3) and nylon cord with high heat shrinkage (1890d / 3
/ 2) consisting of a single belt layer ・ Comparative tire Same as the invention tire except that the nylon cord with high heat shrinkage is omitted from the invention tire ・ Test method Each of the above tires is a 400 cc sports tire Various performances were evaluated when the vehicle was mounted on the rear wheel of a car and run on a test course. ・ Test results Table 1 shows the test results.

[Table 1] As shown in Table 1, it is understood that, in the invention tire, the lateral force is increased due to the increase in the tread surface rigidity, especially when the vehicle is turning, and as a result, the road surface grip force is also improved.

[0012]

As is apparent from the above comparative examples, according to the present invention, in particular, the cord density of at least one belt layer is increased to bring about an appropriate increase in the tread rigidity, so that the tire is grounded. Sex is kept high enough,
It is possible to effectively increase the road grip force when the vehicle is turning.

[Brief description of drawings]

FIG. 1 is a sectional view in the tire width direction showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of how belt layer cords are arranged.

[Invention of code] 1 bead core 3 carcass 3a carcass ply 4 belt 4a belt layer 4b cord with high heat shrinkage ratio 4c cord with low heat shrinkage ratio 5 tread

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location D02G 3/48 7199-3B

Claims (1)

[Claims] 1. At least one carcass ply consisting of cords extending at an angle of 25 ° to 90 ° with respect to the tire circumferential direction, and at least one belt layer consisting of cords extending substantially in the tire circumferential direction. A tire comprising a cord, wherein at least one belt layer having a width substantially equal to the tread width is formed by two kinds of cords, and the heat shrinkage rate of one cord at about 140 ° C. A pneumatic tire that is more than doubled.