JPH079814A - Radial tire - Google Patents

Abstract

PURPOSE:To raise the rigidity in circumferential direction and improve the durability at high speed of a uniformity by dissolving the step at a bend so as to flatten it, and laying belt plies on top of each other, when bending both ends of the inner belt ply outward. CONSTITUTION:An inner belt ply 2, where many aramide cords are arranged at 10-30 deg. to the direction of a tire, is provided inside in tire's radial direction of a belt between a curcus, where many cords are arranged at right angles in the circumferential direction of a tire, and a tread, which covers the crown. An outer belt ply 3, where many cords are arranged, is stacked, at 10-30 deg. in cord direction outside of it, in opposite direction to the direction of the inclination of the inner cord, and both ends of the inner belt ply 2 are bent outward in such a way as to wrap the end of the outer belt ply 3 so as to form a bend. Inside it, a edge ply, where thermoshrinking organic fiber cords are arranged parallel in circumferential direction, is arranged on the external faces in both end regions of the outer belt ply 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt end reinforcement structure for a pneumatic tire. More specifically, a carcass in which cords are arranged substantially on a radial surface and a plurality of belt plies between the carcass ply layer and the tire tread are arranged. The improvement of tire uniformity and durability by reinforcing with.

[0002]

2. Description of the Related Art Conventionally, in this type of radial tire, two belt plies in which a large number of steel cords are arranged as a belt structure with respect to the tire circumferential direction, that is, a so-called cord angle of 10 ° to 30 ° are arranged in the inclination direction of the cord. Belts laminated so as to face each other at an angle were arranged outside the crown portion of the carcass.

By the way, in the tire of this structure, the bending rigidity of the steel cord is large, so that the riding comfort is poor, and when the tire rotates at a high speed, the end portion of the belt, that is, the shoulder portion, is raised by the centrifugal force, and the belt is lifted. The phenomenon that the ply cord peeled off from the rubber layer was often seen.

Further, since the belt ply is made of a steel cord, there is a problem that the steel cord is rusted by water entering from the wound of the tread formed by stepping on a nail or the like, and the strength is immediately lowered. In order to prevent this, the belt ply located outside is formed of aramid cord of organic fiber, and by changing the aramid cord to have a bending rigidity smaller than that of steel cord, the decrease in tensile rigidity in the circumferential direction of the belt end portion is reduced by the belt. A structure has been proposed in which the end portion of the ply is bent inward and overlapped to complement this (JP-A-56-108303).
On the other hand, a method has been proposed in which the inner belt ply is formed of an aramid cord and a ply in which cords are arranged in parallel to the tire circumferential direction is arranged on the outer surface of the end portion of the belt to reinforce (special feature. (Kaisho 54-102702).

[0005]

However, in the former two proposals, the tensile elastic modulus of the steel cord conventionally used is 13,000 to 20,000 kg / mm ² , whereas the tensile strength of the aramid cord is Elastic modulus is 3,000-
Since it is as low as 6,000 kg / mm ² , the effect of preventing the end portion of the belt ply from rising is insufficient. Moreover, FIG.
As shown in, the tire shoulder portion 1 of the belt ply 10
In the belt ply end 12 located at 1, the inner belt ply 13 and the outer belt ply 14 are
Since the belt ply is double-folded and overlapped at 2, the belt ply forms at least three belt plies at the end portion 12, and a step D is formed at the bent portion. In the winding and forming work of the belt ply 10 in
There is a danger that air will enter this step D. During high-speed running, the belt ply 10 becomes insufficient in restraining force of the belt ply end 12 as the tire shoulder 11 rises, and the durability at high speed becomes insufficient. Further, since the inner belt ply 13 is arranged at an angle, the bent end portion becomes wavy when bent in the molding process, which is not preferable in maintaining uniformity of uniformity.

In view of the above situation, the inventor of the present invention considers the elastic modulus of the cord in the tire belt ply structure, the inclination angle of the cord, and the displacement of the inclination angle of the bending cord due to the bending of the end of the cord and the composite elasticity. A thorough study was conducted to investigate the effect on the rate. As a result, the composite elastic modulus is more affected by the cord crossing angle than the cord elastic modulus. On the other hand, if you bend one cord,
Since tensile stress acts on the outside inside the cord and compressive stress acts on the inside (center side) on the contrary, there is no room to enter the angle as a parameter in this case, and the bending rigidity of the cord depends on the elastic modulus of the cord itself. Since the effect is greater, it was found that the flexural rigidity can be reduced and a large composite elastic modulus in the tensile direction can be obtained by selecting the inclination angle of a cord having a small elastic modulus.

However, the present invention has been made on the basis of the above findings. When the inner belt ply is bent, the edge ply having a cord angle of substantially 0 ° is simultaneously expanded and sandwiched in between, and the step of the bent portion is stepped. The purpose is to improve the rigidity in the circumferential direction by overlapping the belt plies and improve the uniformity and high-speed durability.

[0008]

The radial tire of the present invention, which meets the above-mentioned object, is characterized by covering a carcass in which a large number of cords are arranged at right angles to the tire circumferential direction and a crown portion of the carcass. During the tread,
A radial tire having a radial structure in which two belt plies in which a large number of cords are arranged at cord angles of 10 ° to 30 ° with respect to the tire circumferential direction are laminated so that the inclination directions of the cords are opposite to each other. An inner belt ply in which a large number of aramid cords are arranged at a cord angle of 10 ° to 30 ° on the inner side in the tire radial direction is provided outside the inner belt ply at a cord angle of 10 ° to 30 °, which is opposite to the cord inclination direction of the inner belt ply. An outer belt ply in which a large number of cords are arranged in a direction is laminated, and both ends of the inner belt ply are bent outward so as to wrap the ends of the outer belt ply to form a bent portion, and the outer belt is inside the bent portion. A structure in which an edge ply in which heat-shrinkable organic fiber cords are arranged in parallel in the circumferential direction is arranged on the outer surface of both end regions of the ply. A.

Here, the cord of the outer belt ply is preferably an aramid cord or a steel cord, and the edge ply is formed by joining two strip-shaped bands in which nylon cords are arranged in parallel to each other at their longitudinal ends. Is suitable. Further, it is preferable to dispose the edge ply so that the end on the outer side in the tire rotation axis direction protrudes from the end of the outer belt ply.

[0010]

In general, when two belt plies, both ends of which are cut ends, are arranged and laminated with the cords having the inclination angles opposite to each other, the ends of the cords are not restrained. There is a degree of freedom and it is easy to move. Therefore, a phenomenon in which the belt ply extends in the circumferential direction by changing the arrangement angle of the cords according to the stress in the circumferential direction due to the centrifugal force or the like accompanying the rotation of the tire and the stress in the circumferential direction, that is, the so-called belt. Rigid shoulder drop phenomenon is observed. That is, as shown in FIG. 4, in the film force distribution graph, the spring constant decreases in the range of 0 to 25 mm at the end portion of the belt ply. Therefore, in the present invention, the cords have different inclination angles, that is, the inner belt ply ends are bent and overlapped with the end regions of the outer belt plies where the cord angles intersect, and the cord angles with respect to the circumferential direction. Since the edge plies of substantially 0 ° are sandwiched so that their end regions overlap the outer belt end portions, the angles of the four plies are arranged differently as shown in FIG. The tensile rigidity in the direction becomes high.

Now, the calculation formula (35) described on pages 156 to 157 of the reference, "Structural Mechanics of Radial Tires" [The Rubber Society of Japan, Vol. 51, pages 152 to 168 (March 1978 issue)] is used. Using the two fibers (A: steel cord, B: aramid cord) shown in Table 1 and changing the crossing angle of the tire cords to calculate the composite elastic modulus with the two cords, as shown in FIG. There is approximately an inverse linear relationship between the logarithm and the crossing angle of the cord, and in the practical range of the crossing angle of 15 ° to 25 °, the composite elastic modulus is greatly reduced even if the angle is slightly increased. The result has been obtained.

[0012]

[Table 1]

That is, unlike the conventional tire described above, in which the belt ply is simply folded and the folded portion is overlapped on the belt ply, the tire of the present invention has a folded portion in the end folded region of the belt ply. Since the cords sandwiched the inner edge ply of substantially 0 ° with respect to the circumferential direction, the cord angle between each ply is set to about 1/2 of the cord angle of the belt to increase the composite elastic modulus, and both ends of the bent portion. In the area, a powerful panda graph effect is exerted, so it functions more effectively against the rising of the shoulder part. Also, since the edge ply is expanded and sandwiched in the bent part, the size of the step is eased, and the inner belt ply can be bent along the edge of the edge ply in the tire manufacturing process, so that the conventional bent part is restrained. The meandering of the end of the bent part that was seen when bending without doing
Moreover, since the cap ply is made by lap splicing two bands, the length of each band is shorter than that when it is one, and the shrinkage amount during vulcanization is small, so the splicing margin may be small. This has the effect of locally increasing the cord density and suppressing the increase in rigidity, and well controlling the deterioration of tire uniformity.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the accompanying drawings, but the present invention is not limited thereto.

FIG. 1 is a cross-sectional side view showing a main part of a belt ply in a pneumatic tire showing one example of the present invention,
FIG. 2 is an explanatory view showing a bent state of the inner belt ply in the belt ply, and FIG. 3 is a one side development plan view showing a laminated state of the belt ply and the edge ply.

In the drawing, 1 indicates a belt ply, and 2
Is a belt ply 1, which is an inner belt ply located on the inner side in the tire radial direction, and 3 is an outer belt ply located on the outer surface thereof. Reference numeral 4 denotes an edge ply for reinforcing the end portion of the belt ply 1 to eliminate a step. The belt ply 1 is arranged between the tire tread T and the carcass C. One of the most important points in the present invention is that the width of the end portion of the inner belt ply 2 constituting the belt ply 1 is widened in advance, and the edge ply 4 is partially overlapped with the end portion of the outer belt ply 3. The other end which is not overlapped or overlapped is bent in the tread T direction with this as a reference to form a bent portion 5, which sandwiches the end portion of the outer belt ply 3 and the edge ply 4 and both ends of the inner belt ply 2 thereof. The folded ends are to terminate in the central region of the tread T, spaced apart from each other. In this case, the outer belt ply 3 may be one or more and may be plural. Further, in this example, the outer belt ply 3 of the belt ply 1 is made of steel or aramid fiber, and the inner belt ply 2 is unsuitable for steel because it needs to be bent, and aramid fiber is used. The edge ply is preferably a nylon cord which has good adhesiveness with rubber and shrinks strongly during vulcanization. Further, one of the purposes of using the edge ply 4 is to eliminate the formation of a step in the bent portion 5 of the inner belt ply 2. Therefore, the edge ply to be used preferably has a small thickness, and a plurality of edge plies may be used depending on the thickness. The angle of the cord is substantially 0 ° with respect to the circumferential direction.
In the setting of the edge ply, the protruding portion 6 that does not overlap the outer belt ply 3 is necessary at one end, and when the inner belt ply 2 is bent, it is folded along the end 7 of this portion.
Therefore, it is not necessary to set the reference line for bending in advance. Further, the length L of the edge ply 4 (FIG. 2- (b)) is
Depending on the size of the tire, it will be about 20-4
0 mm is suitable. This can be understood also from the film force distribution graph of FIG. The length L of the protruding portion 6 where the edge ply 4 is not overlapped with the outer belt ply 3 is L.
₁ is preferably about 2 to 5 mm. Therefore, the bent ends of the inner belt ply 2 are separated from each other in the central region of the tread T, and the rigidity of this portion of the tire is controlled, so that the tire closely contacts the road surface and secures the steering stability. It is effective. The edge ply 4 is formed by arranging a large number of cords in parallel and gluing two rubber-coated bands on each other so that both ends overlap each other. The two joints join the both ends of the belt band endlessly. It is necessary to shift the phase by 90 ° with respect to the joint portion of the belt ply formed at that time, and to disperse the joint portion where the cord density is increased and the rigidity is locally large to average the rigidity.

Comparison with Comparative Example 1) Test tire tire size; 195 / 60R14 belt ply structure-outer belt ply; steel 2 + 7 × 0.175 20
Book / inch, angle 24 ° ・ Inner belt ply; Aramid 1500 D / 2 23
Book / inch, angle 20 ° ・ Edge ply; Nylon 840 D / 2 37 book /
Inch, angle 0 °

2) Test conditions High-speed durability test ECER30 (European Economic Commission Regulations Article 30, Appendix 7)
According to the high-speed durability test method of No. 1, after continuing to meet the specified conditions, the tire was further continued until it was destroyed. The result is Comparative Example 1
The index was evaluated as 00. The larger the number, the better. Tire uniformity test The tire uniformity test was performed according to the test method of JASO C 607 (Japanese automobile standard). The result was indexed with the comparative example being 100. The larger the number, the better.

The test results are shown in Table 2. The comparative example is an example in which the edge ply is not used.

As can be seen from Table 2 below, in the examples, the high speed durability is improved without lowering the uniformity.

[0021]

[Table 2]

[0022]

According to the present invention, since the end portion of the folded belt ply is reinforced by the edge ply, the restraining force at the end portion of the belt ply becomes stronger and the shoulder portion is prevented from rising so that the high speed durability performance is improved. In addition to improving the workability, the end of the inner belt ply at the time of tire forming serves as a folding reference line during folding, so that work efficiency is improved, and the step of the edge ply is greatly eased, resulting in the edge ply. The effect of well controlling the decrease in uniformity due to joining and improving the durability of the tire is achieved.

[Brief description of drawings]

FIG. 1 is a side cross-sectional view showing a main part of a belt ply of a pneumatic tire showing an example of the present invention.

2 (a), (b) and (c) are explanatory views showing a bent state of the inner belt ply in FIG.

FIG. 3 is a one side development plan view showing a laminated state of a belt ply and an edge ply of the tire of the present invention.

FIG. 4 is a film force distribution graph showing the correlation between the spring constant of the radial tire belt and the position of the belt full width.

FIG. 5 is a graph showing a correlation between a crossing angle of belt cords of a radial tire and a composite elastic modulus.

FIG. 6 is a one-sided transverse sectional view showing an essential part of a belt ply, which is an example of a conventional tire.

[Explanation of symbols]

 1 Belt Ply 2 Inner Belt Ply 3 Outer Belt Ply 4 Edge Ply 5 Bent Part 6 Overhanging Part 7 End of Overhanging Part C Carcass Ply CR Crown Part T Tread

Claims (5)

[Claims] 1. A large number of cords are arranged at a cord angle of 10 ° to 30 ° with respect to the tire circumferential direction between a carcass in which a large number of cords are arranged at right angles to the tire circumferential direction and a tread covering a crown portion of the carcass. In a tire having a radial structure in which two cord plies are laminated so that the inclination directions of the cords are opposite to each other, a large number of aramid cords are arranged inside the belt in the tire radial direction at a cord angle of 10 ° to 30 °. The inner belt ply is laminated with an outer belt ply having a large number of cords arranged on the outer side of the inner belt ply at a cord angle of 10 ° to 30 ° in the direction opposite to the cord inclination direction of the inner belt ply. The both ends of the outer belt ply are folded so as to wrap the end of the outer belt ply to form a bent portion, and the outer belt ply is located inside the bent portion. A radial tire comprising a belt having edge plies in which heat-shrinkable organic fiber cords are arranged in parallel in a circumferential direction on both outer surfaces of the end regions. 2. The radial tire according to claim 1, wherein the cord of the outer belt ply is an aramid cord. 3. The radial tie according to claim 1, wherein the cord of the outer belt ply is a steel cord. 4. The radial tire according to claim 1, wherein the edge ply is formed by joining two bands of nylon cords arranged in parallel to each other at both ends in the longitudinal direction. 5. The radial tire according to claim 1, 2, 3 or 4, wherein an end of the edge ply on the outer side in the tire rotation axis protrudes from an end of the outer belt ply.