JP3338486B2 - Pneumatic 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 pneumatic tire having a reinforcing layer between a tire carcass layer and a belt layer disposed radially outward of the tire carcass layer, and to improve the durability of the pneumatic tire. .

[0002]

2. Description of the Related Art A belt layer of a pneumatic tire is formed by laminating two or more layers of belt plies in which a large number of reinforcing cords obliquely arranged with respect to the equatorial plane of the tire are embedded and the reinforcing cords cross each other. It is customary. When such a pneumatic tire is filled with the prescribed internal pressure, tension is generated in the belt layer in the circumferential direction, and the belt ply undergoes shear deformation in its plane, and a large shear strain acts on rubber at both ends of the belt ply. . The shear strain at the end of the belt ply is further increased when the tire is grounded and deformed, so that the belt end may be separated due to long-term running.

In order to prevent this separation, for example, Japanese Patent Publication No. 3-23361 discloses a reinforcing cord between a carcass layer and a belt layer, the width of which is smaller than that of the belt layer and whose inclination angle with respect to the tire equatorial plane is small. Is buried 2
The provision of a limiter block consisting of plies of layers is described. That is, when the tire is filled with the internal pressure, the circumferential tension generated at the time of the ground deformation is shared by the limiter block having high circumferential rigidity, and the circumferential tension shared by the belt layer is reduced, whereby the shear strain at the belt end is reduced. And the separation at the belt end is suppressed.

[0004]

However, the pneumatic tire described above can reduce the shear strain at the belt end to a certain extent, but the effect is not sufficient, and especially when the vehicle is running on a rough road, the pneumatic tire cannot reduce the shear strain. When a large input acting on the tire is applied to the tire when, for example, stepping over a protrusion, the separation may occur. By the way, to prevent the belt layer from being cut and then penetrated by bumps etc. when traveling on rough roads, that is, if the reinforcement cord of the belt layer is increased in diameter in order to increase cut resistance, the separation resistance at the belt end is further deteriorated. It is known to end up.

[0005] In addition, in order to reduce the shear strain at the belt end caused by the ground contact deformation in the state of the internal pressure filling, it is generally known to increase the inclination angle of the reinforcing cord of the belt layer with respect to the tire equatorial plane. This method has a problem in that the circumferential rigidity of the belt layer is reduced, so that the diameter growth at the time of filling with the internal pressure increases, and the wear resistance and cut resistance of the tread deteriorate.

An object of the present invention is to provide a pneumatic tire capable of reliably suppressing the separation at the belt end without increasing the diameter growth during internal pressure filling even if the cord of the belt layer is thickened. What you want to do.

[0007]

According to the present invention, a carcass straddling in a toroidal manner between a pair of bead cores and a plurality of reinforcing elements arranged in parallel with each other are arranged obliquely with respect to the equatorial plane of the tire. Consists of a layer of belt ply,
Between the reinforcing element of at least two layers of the belt ply and the belt layer laminated in an arrangement intersecting with each other, with a width smaller than the maximum width of the reinforcing element intersection region in the belt ply,
Two layers of reinforcing plies in which reinforcing elements in parallel with each other are arranged at an inclination angle smaller than the inclination angle of the reinforcing elements of the belt ply with respect to the equatorial plane of the tire are laminated in an arrangement where the reinforcing elements of each layer cross each other. A pneumatic tire comprising a reinforcing layer, wherein the rubber covering the reinforcing layer has a higher elastic modulus than the rubber covering the belt layer.

Here, cords made of steel or organic fibers, monofilaments and multifilaments are suitable for the reinforcing element.

FIG. 1 illustrates a specific example of a pneumatic tire according to the present invention. Pneumatic tire 1 shown in FIG.
Has a pair of bead cores 2 and a carcass layer 4 composed of at least one carcass ply 3, which extends in a toroidal shape between the bead cores 2, and is wound back from the inside of the tire to the outside at each bead core 2. As shown in FIG. 2, the ply 3 of the carcass layer 4 embeds a large number of reinforcing elements 5 extending in a direction perpendicular to the equatorial plane O of the tire. A belt layer 7 formed by laminating two or more, in this example, three layers of belt plies 6 is disposed outside the carcass layer 4 in the tire radial direction. Each belt ply 6 of this belt layer 7
The inclination angle A with respect to the tire equatorial plane O, preferably 10 to 40
A large number of reinforcing elements 8 arranged in the range of
It is buried inside. Further, in the belt layer 7, at least two belt plies out of two or more belt plies, in this example, a first belt ply 6a and a second belt ply 6b
Are arranged so as to intersect with each other.

Incidentally, in this example, the inclination angle Aa of the reinforcing element 8a of the innermost first belt ply 6a with respect to the tire equatorial plane is 18 ° to the upper right in the arrangement shown in the figure, and similarly, the second belt ply 6b Angle of the reinforcement element 8b of the
The inclination angle Ac of the reinforcing element 8c of the third belt ply 6c is 18 ° to the left.

Further, the tread layer 10 is arranged on the outer side of the belt layer 7 in the tire radial direction, and two reinforcing plies 11 and 12 which intersect each other are overlapped between the belt layer 7 and the carcass layer 4. The reinforcing layer 13 is arranged. This reinforcement layer
13 is an area centered on the tire equatorial plane O whose width is smaller than the maximum width of the reinforcing element intersection area in the belt layer 7, in this case, the width of the belt ply 6b, in order to maintain the characteristics of the belt layer 7. To place. And each reinforcement ply 10, 11
Is formed by embedding reinforcing elements 14 and 15 in a covering rubber 16. These reinforcing elements 14, 15 are arranged in parallel with each other,
The inclination angles Ca and Cb respectively with respect to the tire equatorial plane O are
The reinforcing element 8 of the belt ply 6 is disposed at an angle smaller than the inclination angle A with respect to the tire equatorial plane O. In this example, the inclination angles Ca and Cb are 5 °. It is important that the elastic modulus of the coating rubber 16 of the reinforcing layer 13 is larger than the elastic modulus of the coating rubber 9 of the belt layer 7, and it is preferably 1.2 to 2.5 times. In this example, it is 1.4 times.

[0012]

When the pneumatic tire according to the present invention is filled with a specified internal pressure, the pneumatic tire is inflated, and each belt ply is stretched in the circumferential direction to generate circumferential tension. Due to this tension, each belt ply undergoes shear deformation in the ground contact surface, and as a result, shear strain is generated in the rubber at both ends in the width direction of the belt ply. The shear strain at the end of the belt ply is further increased by the deformation of the pneumatic tire upon contact with the ground.

Therefore, in the present invention, the tire has a high circumferential rigidity and a narrow width composed of two layers of reinforcing plies in which the reinforcing elements are buried, wherein the tilt angle with respect to the tire equatorial plane is smaller than the reinforcing element of the belt layer. A reinforcing layer is provided between the carcass layer and the belt layer, and the reinforcing layer shares a substantial portion of the circumferential tension, reduces the circumferential tension shared by the belt layer, and reduces the shear strain at the belt end. .

Further, in the present invention, the elastic modulus of the rubber covering the reinforcing layer is made larger than that of the belt layer, and the circumferential rigidity of the reinforcing layer is further increased, so that the share of the circumferential tension by the reinforcing layer is increased. Thus, the rate of distribution of the circumferential tension by the belt layer is further reduced. Therefore, without increasing the diameter growth of the tire, when the reinforcing element of the belt layer is thickened to improve cut resistance, in order to reduce the shear strain acting on the end of the belt ply, the reinforcing element of the belt layer. The inclination angle with respect to the tire equatorial plane can be increased. In addition, even when a large input is applied, such as an input when the tire is riding on a protrusion, since the elastic modulus of the rubber covering the reinforcing cord of the belt layer is relatively small, the rubber can follow the deformation of the cord, Separation at the belt end is reliably suppressed.

Here, the elastic modulus of the rubber covering the reinforcing layer is preferably 1.2 to 2.5 times the elastic modulus of the belt layer.
That is, if the ratio is less than 1.2 times, a sufficient effect of increasing the circumferential tension share of the reinforcing layer by increasing the circumferential rigidity of the reinforcing layer cannot be obtained. On the other hand, if it exceeds 2.5 times, the difference in elastic modulus between the belt layer and the covering rubber becomes too large, and when a large input such as stepping on a protrusion at the tire center, the covering rubber of the reinforcing layer and the covering of the belt layer are applied. Peeling may occur at the interface with the rubber.

Further, the inclination angle of the reinforcing element of the belt layer is:
It is preferable that the angle be 10 to 40 ° in order to effectively reduce the shear strain at the belt end and ensure the rigidity in the circumferential direction. In addition, the inclination angle of the reinforcing element of the reinforcing layer, which is smaller than the belt layer, is set to be less than 10 ° other than 0 °, by increasing the circumferential rigidity of the reinforcing layer, and thereby the distribution ratio of the circumferential tension of the reinforcing layer. This is advantageous in that

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The elastic modulus of the coating rubber 16 of the reinforcing layer 13 and the elastic modulus of the coating rubber 9 of the belt layer 7 of the test tire (1) shown in FIGS. The test tire (2) changed to 1.7 times and the test tire (1) in which the reinforcing elements of the first and second belt plies were increased in diameter and the inclination angle to the tire equatorial plane was increased by 4 ° ( 3) and a comparative tire in which the elastic modulus of the coating rubber 16 of the reinforcing layer 13 of the test tire (1) was the same as the elastic modulus of the coating rubber 9 of the belt layer 7 were prepared. Here, the size of each tire is 11.00
R 20.

Next, after filling such a tire with an internal pressure of 7.25 kgf / cm ² , the tire is driven on a drum at 60 km / h at a load of 150% in accordance with the JATMA standard until the failure occurs. The mileage was measured. Table 1 shows the results and the diameter growth of each tire at the time of filling the internal pressure in the form of an index when the result of the comparative tire was set to 100, together with the elastic modulus of the rubber covering the belt layer 7 and the reinforcing layer 12. Show. Here, the elastic modulus of rubber is represented by Mod ₁₀₀ (kgf / cm ² ), and the index of diameter growth at the time of internal pressure filling is 10
0 is actually 1.40 mm, an index of 100 on the drum test results.
Was actually 3450 km.

[0019]

[Table 1]

[0020]

As described above, according to the present invention, it is possible to reduce the shear strain at the belt end without increasing the diameter growth at the time of filling the internal pressure, thereby deteriorating the wear resistance and cut resistance. Without separation, the separation at the belt end can be reliably suppressed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in the tread width direction of a tire according to the present invention.

FIG. 2 is a schematic diagram showing a laminated structure of a carcass layer, a reinforcing layer, and a belt layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead core 3 Carcass ply 4 Carcass layer 5, 8, 8a, 8b, 14, 15 Reinforcing element 6, 6a, 6b Belt ply 7 Belt layer 9, 16 Coated rubber 10 Tread layer 11, 12 Reinforcement ply 13 Reinforcement layer

Claims (1)

(57) [Claims] 1. A carcass straddling in a toroidal manner between a pair of bead cores, and a plurality of belt plies in which reinforcing elements arranged in parallel with each other are arranged at an angle with respect to the equatorial plane of the tire. A reinforcing element that is parallel to each other and has a width smaller than the maximum width of the reinforcing element intersecting region in the belt ply is provided between the reinforcing element of the two-layer belt ply and a belt layer that is stacked so as to cross each other. A reinforcing layer in which two layers of reinforcing plies are arranged at an inclination angle smaller than the inclination angle of the reinforcing elements of the belt ply with respect to the equatorial plane, and the reinforcing elements of the respective layers are stacked so as to intersect each other. The pneumatic tire, wherein the coated rubber has a larger elastic modulus than the coated rubber of the belt layer.