JP2699098B2 - Pneumatic radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an air having a belt cover layer composed of a cord whose cord direction is substantially 0 ° with respect to the tire circumferential direction on the outermost layer of the belt layer. The present invention relates to an improvement in a radial tire containing the tire.

[Conventional technology]

Conventionally, a belt cover layer is disposed on a belt in order to obtain a radial tire having excellent high-speed performance.

The belt cover layer has a function of reinforcing the belt layer, preventing the belt from rising during high-speed running, and improving the rigidity in the tire circumferential direction in combination with the belt layer. As the cord of the belt cover layer, a textile cord made of a heat-shrinkable material such as a nylon cord or a polyester cord is generally used, and the cord is arranged at almost 0 ° with respect to the tire circumferential direction E, E '. ing.

By the way, in the tire provided with the belt cover layer, after the belt layer is arranged in the manufacturing process, FIG.
As shown in FIG. 5 (B), on the outermost layer of the belt layer 5, a belt cover layer 6 in which cords are arranged at substantially 0 ° with respect to the tire circumferential direction is disposed, and a terminal portion 6 is provided.
A splice portion 61 is formed by superimposing 2,63. In this case, the splice portion 61 of the belt cover layer 6
It represents the length in the tire circumferential direction at l ₁ (see FIG. 5 (A)).

Next, the tire constituent members such as the tread portion 3 are arranged,
Thereafter, the unvulcanized tire is vulcanized by heating under pressure in a vulcanization mold (not shown) to obtain a product tire.

Here, the outer circumference of the unvulcanized tire before vulcanization is formed smaller than the inner circumference of the vulcanization mold, and at the time of vulcanization, the unvulcanized tire is pressed from the inside of the tire in the vulcanization mold and the tire is vulcanized. And the outer periphery thereof is brought into close contact with the inner peripheral surface of the vulcanization mold. This is generally called lift. The value obtained by dividing the difference between the outer circumference of the unvulcanized tire before vulcanization and the outer circumference of the vulcanized tire after vulcanization by the outer circumference of the unvulcanized tire before vulcanization is referred to as a lift rate.

When the lift is applied in this manner, the carcass layer and the belt layer 5 can grow in outer peripheral length due to their structures. However, as described above, the cord of the belt cover layer 6 is substantially in the tire circumferential direction. Due to the arrangement at 0 °, it cannot grow. Therefore, the growth of the belt cover layer 6 is only attributable to the fact that the cords constituting the belt cover layer 6 are elongated and the end portions 62 and 63 of the splice portion 61 are shifted from each other.

However, since the adhesive strength of the splice portion 61 is smaller than the tensile strength of the cord forming the belt cover layer 6, most of the growth is due to the displacement of the splice portion 61. Thereby, the length l ₂ of the spliced portion 61 after vulcanization
(See FIG. 5 (B)) is shorter than the length l ₁ before vulcanization. As a result, most of the growth of the belt layer 5 and the tread portion 3 is also performed in the portion that is adhered to the splice portion 61 described above. In order to reduce this as much as possible, the modulus of the belt cover cord must be made as large as possible in consideration of the balance with the tire performance, so that it can be easily extended.

For this reason, a non-uniform portion is formed on the circumference of the tire, and the non-uniformity contributes to the vehicle vibration when the automobile runs at a high speed, and also deteriorates the high-speed durability of the tire.

This is because, when the tire is mounted on the vehicle and the high-speed durability test is performed, the vicinity of the splice portion is abnormally quickly worn, and when the indoor high-speed durability test is performed, the peeling failure almost occurs from the splice portion. Is also supported.

If the belt cover layer 6 is damaged by some kind of damage and reaches the belt layer, moisture or the like penetrates into the belt layer through the damage. Therefore, when the belt layer is made of a steel cord, rust is generated on the cord, or a peeling phenomenon (separation) occurs between the cord and the covering rubber, thereby lowering the durability of the belt portion.

[Problems to be solved by the invention]

An object of the present invention is to improve the uniformity of a tire on which a belt cover layer having a splice portion is disposed, improve the high-speed durability without deteriorating the uniformity (particularly, RFV or RRO) of the tire, and further improve the trauma. An object of the present invention is to provide a pneumatic radial tire in which a reduction in durability of a belt portion due to the above is prevented.

[Means for solving the problem]

The present invention relates to a radial tire having a belt cover layer made of a cord whose cord direction is substantially 0 ° with respect to the tire circumferential direction on the outer side of the belt layer. The cord is formed by helically winding on a belt layer, and this cord is a non-twisted polyamide fiber composed of a single monofilament.
The gist of the present invention is a pneumatic radial tire having a flatness of 1.5 or more, wherein the monofilaments are arranged in parallel with the major axis direction oriented in the tire width direction.

 Hereinafter, this means will be described in detail with reference to the drawings.

In the radial tire of the present invention, as shown in FIGS. 1 and 2, a carcass layer having a cord angle of substantially 90 ° with respect to the tire circumferential direction E, E ′ is provided between a pair of right and left bead portions 1, 1. 4 and the cord angle with respect to the tire circumferential direction E, E 'is 1 on the carcass layer 4 in the tread portion 3.
A plurality of belt layers 5 intersecting each other at 0 ° to 30 ° are arranged, and a belt cover layer 6 is arranged on the outermost layer 5u of the belt layers 5. In FIG. 2, 6a represents a cord constituting the belt cover layer 6, 5a represents a cord constituting the belt layer 5, and 5d represents an innermost layer of the belt layer 5.

As a material of the cord constituting the carcass layer 4, chemical fibers such as nylon, rayon, and polyester are generally used. As the cord of the belt layer 5, a steel cord is mainly used, but a high-strength chemical fiber cord such as an aromatic polyamide fiber cord can also be used.
When a chemical fiber cord is used as the cord of the belt layer 5, for example, when the belt layer has two layers, a steel cord and a chemical fiber cord are combined so that one layer is a steel cord and the other layer is a chemical fiber cord. May be used.

(1) In the present invention, the belt cover layer 6 is configured by spirally winding a rubber tape having a cord embedded on the belt layer 5.

By spirally winding the rubber tape on the belt layer 5 in this manner, the start point and the end point of the start and end of the winding of the rubber tape are only at the end, and the above-described splice portion over the entire width is not generated. No local deformation occurs at the splice portion as in the prior art, so that the unevenness on the tire circumference due to the arrangement of the belt cover layer is removed, and the uniformity is improved. Furthermore, since there is no local deformation (so-called zukoke) at the splice portion, local stress concentration is reduced, so that high-speed durability and load durability are also improved.

The rubber tape has one or a plurality of cords embedded in rubber. The rubber used in this case may be composed of a general rubber composition generally used for a belt cover layer.

(2) A non-twisted polyamide fiber composed of a single monofilament is used as a cord constituting the rubber tape.

In general, a conventional tire cord is formed by bundling a plurality of thin multifilaments, and a predetermined twist is applied to the cord to provide convergence and fatigue resistance. On the other hand, in the present invention, a non-twisted polyamide fiber composed of a single monofilament is used. This is because the cord is made of a single monofilament having a relatively high denier and is not twisted in order to obtain a high modulus. As the polyamide fiber, for example, nylon 66 having a fiber forming property
(Polyhexamethylene adipamide), nylon 6 (polycaprolactam), nylon 46 (polytetramethylene adipamide) and the like.

(3) The cross-sectional shape of the non-twisted monofilament is flattened, and the ratio α between the major axis a and the minor axis b is 1.5 or more (α = a / b ≧ 1.5).

The flatness is used to improve the durability (fatigue resistance) as described below. That is, FIGS. 3A and 3B
As shown in the figure, the circular cross section code m and the cross section flat code n having the same cross sectional area and different cross sectional shapes respectively
The bending strain generated in the cord when the same bending deformation is given is expressed by the following equation.

ε = ε ₀ + ZK, where ε ₀ : strain at the neutral axis t of bending Z: distance from the neutral axis t of the bending K: change in curvature Therefore, as Z increases, the bending strain generated increases. Larger than the maximum value Z _max of the maximum value Z _max is a flat code n Z of Z circular code m, consists of a single filament in the cord untwisted, twisted fatigue resistance of not over Reduce the cross-sectional shape with code n
By flattening as described above, bending strain generated in the cord can be reduced and prevented.

In the case of flattening in this way, in FIG. 4 showing the cord n in an enlarged manner, if the ratio α between the major axis a and the minor axis b is less than 1.5, a decrease in fatigue resistance cannot be sufficiently prevented. Therefore, in the present invention, α = a / b ≧ 1.5.

Further, when arranging the cords n, it is necessary to arrange the cords in parallel with the longer diameter side facing the tire width direction. As a result, the uneven plane of the cord n is oriented in the tire tread direction, so that the belt surface inner surface bending rigidity is improved and steering stability can be improved.

(4) In the present invention, in addition to the above, the physical properties of the cord n after the heat treatment for bonding, that is, the elongation under a load of 2.25 g / d is 6.5% or less and the heat shrinkage at 150 ° C. is 4.5% % Is preferable.

Here, the term “adhesive heat treatment” refers to heat treatment after RFL treatment of a cord by a conventional method in order to increase the adhesive strength with rubber. The heat shrinkage is the shrinkage after treatment at 150 ° C. for 30 minutes.

If the elongation of the cord under a load of 2.25 g / d exceeds 6.5%, the initial modulus will be low, and when used as a cord for the belt cover layer, improvement in high-speed durability cannot be obtained. Also,
If the heat shrinkage at 150 ° C. exceeds 4.5%, the cord shrinks excessively during vulcanization of the tire, the unevenness on the tire circumference becomes remarkable, and the uniformity deteriorates.

 Examples will be described below.

〔Example〕

Cords having a flatness ratio α = 1, 2, and 3 were produced from a 3,000-denier non-twisted monofilament of nylon 66.

This cord was treated with a resorcinol-formalin rubber latex (RFL) adhesive and heat-treated to produce an adhesive treated cord.

This treatment cord is embedded in unvulcanized rubber in the number of 33 pieces / 5 cm to be implanted, a belt cover layer is formed, vulcanized, and the tire shown in Table 1 having a tire size of 195 / 65VR15 (the tire of the present invention 1 To 3, Comparative tires 1 to 2).

Also, as a conventional tire, using nylon 66 multifilament tire cord 840D / 2, twist number 46s / 46z,
A tire was produced in the same manner as described above, with a driving number of 54 pieces / 5 cm. Uniformity (RFV) for these tires
In order to evaluate high-speed durability and high-speed durability, a uniformity measurement test and an indoor durability test (a drum diameter of a testing machine of 1707 mm) were performed under the following test conditions.

Uniformity measurement test: Uniformity was measured by a test method according to JASO conditions. The test results are as follows. The test results are shown in Table 1 by indexes. Smaller numbers are better.

Test conditions Lim: 6JJ × 15 Air pressure: 2.4 kg / cm ² Load: 450 kg Indoor durability test conditions: This is a certified extended destructive test of FMV # 109 high speed performance test. With a load of 545 kg and an air pressure of 2.4 kg / cm ^{2, the} vehicle initially runs at 81 km / hr for 2 hours, and then runs at a speed of 8 km / hr every 30 minutes from 121 km / hr until breaking. Table 1 shows the test results.
Is shown as an index. Larger numbers are better.

As is clear from Table 1, the tire of the present invention is excellent in both high-speed durability and uniformity.

〔The invention's effect〕

As described above, according to the present invention, a rubber tape having a cord embedded therein is spirally wound around a belt layer to form a belt cover layer, and the cord is formed into a non-twisted polyamide fiber composed of a single monofilament. The cross-sectional shape is flat, the ratio α of the major axis a to the minor axis b is 1.5 or more, and monofilaments are arranged in parallel with the major axis direction in the tire width direction, so that tire uniformity and high-speed durability are improved. Thus, it is possible to prevent a decrease in the durability of the belt portion due to an injury. Therefore, the present invention is particularly suitable as a pneumatic radial tire for a passenger car.

[Brief description of the drawings]

FIG. 1 is a half-sectional view in the meridian direction of one example of a pneumatic radial tire of the present invention, FIG. 2 is a plan view showing a belt cover layer of this tire, and FIGS. FIG. 4 is an enlarged explanatory view of the cord in FIG. 3 (B), and FIGS. 5 (A) and (B) are diagrams of a belt cover layer of an example of a conventional pneumatic radial tire. It is explanatory drawing which shows a splice part. 1 ... bead part, 3 ... tread part, 4 ... carcass part, 5 ...
Belt layer, 6 ... Belt cover layer.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-188205 (JP, A) JP-A-61-60303 (JP, A) JP-A-63-315305 (JP, A) JP-A 52-88 140105 (JP, A) JP-A-2-175945 (JP, A) JP-A-2-175910 (JP, A)

Claims (1)

(57) [Claims] 1. A radial tire having a belt cover layer made of a cord whose cord direction is substantially 0 ° with respect to the tire circumferential direction on the outside of the belt layer, wherein the belt cover layer is made of a rubber tape having a cord embedded therein. The cord is configured by being spirally wound on the belt layer, and this cord is a non-twisted polyamide fiber composed of a single monofilament, and the cross-sectional shape of the polyamide fiber is such that the ratio of the major axis a to the minor axis b is 1.5 or more. The pneumatic radial tire according to claim 1, wherein the monofilaments are arranged in parallel with a major axis direction in a tire width direction.