JPH09156315A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly restrain progress of a crack generated on an interface between a belt cord and covering rubber by setting an elastic modulus of wires of a revolving belt layer and a modulus of elasticity of volume of rubber to cover the arranged wires not less than a prescribed value, and forming the arranged wires in a waveform in an area less than a prescribed quantity of a belt width in a side end part of the revolving belt layer. SOLUTION: An elastic modulus of wires 10 of a revolving belt layer 7 is set not less than 2000kgf/m<3> , and a modulus of elasticity of volume of rubber to cover the arranged wires 10 is set to 200kgf/mm<2> , and the arranged wires 10 are formed in a waveform in an area SW less than 10% of a belt width in a side end part of the revolving belt layer 7. Then, a crack progressing along the wires by being generated on an interface between the wires and its covering rubber in the side end part of the revolving belt layer 7, is checked by tread rubber. When the wires 10 are formed in a waveform, the wires can be easily moved, and since there is the possibility of cutting the wires, a modulus of elasticity of volume of covering rubber is set to 200kgf/mm<2> , and a movement of the wires is restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to enhancing the durability of a belt structure in a pneumatic radial tire, and in particular, to the development of rubber cracks which tend to occur in the tire circumferential direction along the side edges of the belt during high speed running. The present invention relates to a pneumatic radial tire having excellent tread rubber layer peeling prevention property, particularly a pneumatic radial tire for passenger cars or light trucks.

[0002]

2. Description of the Related Art A belt for reinforcing a tread portion, which has been applied to pneumatic radial tires, especially pneumatic radial tires for passenger cars which are widely used, is usually 2
˜3 layers of cord crossing layers.

The cord intersecting layer is a plane including the central circumference of the tread portion, in other words, the tire equatorial plane, and the cords of the respective layers, which are often steel cords, are arranged so as to intersect with each other. Is common.

However, it is difficult to obtain desired performances such as lightness, abrasion resistance and durability with the belt composed of the cord crossing layer, so that the belt is not
It is proposed in the following documents (1) to (3) that a slanted belt layer made of rubber-coated cords of layers and a so-called cap layer made of rubber-coated parallel cords on the outer side of the belt are constituted by a laminated body of different cord layers. Has been done.

Here, the cap layer is a winding array of a plurality of cords whose cords are substantially parallel to the equatorial plane of the tire, and is often called a loop belt layer. Regarding the winding arrangement of the plurality of cords forming the orbiting belt layer, being substantially parallel as described above means that the winding belt is arranged on the inclined belt layer and the winding arrangement of the plurality of cords surrounding the outer circumference of the inclined belt layer. However, a spiral-wound structure, that is, a rubber-coated cord or a plurality of cords separated by a rubber coating, or an aligned bundle of a small number of cords stacked and separated by a rubber coating, is provided by a lead corresponding to the cord or the width of the bundle. In addition to the case of being wound, the rubber covered band of the side-by-side cord prepared with the width corresponding to the circulating belt layer,
It is divided into a case where the ends are abutted or overlapped and wound and joined. That is, in the case of a spiral helix structure,
This means that the spiral lead gives a slight inclination angle, and also in the latter case of end butt or winding joining, it means that a slight error inevitable in manufacturing is taken into consideration.

Reference (1) JP-A-61-61 for the purpose of improving separation resistance at the side end portions of the above-mentioned two different types of cord layers applied to a large-sized pneumatic radial tire for heavy loads used in electric trains, monorail vehicles, etc. No. 9314 discloses that a cord elastic modulus of a main belt layer made of cords arranged in a spiral shape with a very small lead angle which is extremely parallel to a tire equatorial plane is set to 3000 Kgf / mm ² or more, and Japanese Unexamined Patent Publication (Kokai) No. 62-152904 discloses that the cord of the same main belt layer is made of an organic fiber such as aromatic polyamide or the cord elastic modulus of 2000 Kgf / mm ² or more.

Reference (2) Japanese Patent Laid-Open No. 4-163212 discloses a tilted belt layer as one steel cord layer in order to improve high-speed durability, uniformity, and weight reduction of a pneumatic radial tire for passenger cars. It is disclosed that the outer cap layer has a helical or spiral helix structure of aromatic polyamide cord with one layer in the center and two layers on both sides.

Reference (3) Also, in US Pat. No. 3,973,612, one inclined cord layer is folded to make an inclination angle of 10 in order to improve both riding comfort and wear resistance of a pneumatic radial tire for a passenger car. It is disclosed that one cap layer is made of a textile cord having an inclination angle of 0 °, which is contained in the range of -30 °.

[0009]

None of the pneumatic radial tires having a belt configuration, which summarizes the characteristics of the documents (1) to (3), have been taken into consideration in the following points.

The pneumatic tires disclosed in Documents (1) to (3) have excellent high-speed durability as compared with a conventional tire using a belt composed of two cord intersecting layers. Because
Conventional tires have low rigidity in the circumferential direction at the belt end, and the protrusion due to centrifugal force generated during high-speed running becomes large, especially at the shoulder (belt end), resulting in an increase in ground contact pressure at the shoulder, resulting in high-speed durability. Is inferior to. On the other hand, in the tire disclosed in the literature, the orbiting belt layer having a high cord elasticity bears the centrifugal force evenly in the width direction, which causes deterioration of the high-speed durability. It is possible to suppress the protrusion in the end area in the direction.

On the other hand, when the cord elastic modulus of the belt is high, the rigidity difference between the end portion of the revolving belt layer and the tread rubber becomes very large, and the strain is concentrated on the interface between the end cord and the covering rubber. At the end portion on the belt layer side, cracks are easily induced at the interface between the cord and the coated rubber. Then, the crack generated at the interface between the belt cord and the coating rubber, as a result of progressing in the circumferential direction of the tread and being connected early on the circumference, the tread rubber comes into crack during high-speed running, so-called tread chunk occurs, Especially when driving at high speed, there was a concern that it could lead to a very dangerous situation.

Accordingly, an object of the present invention is to occur at the interface between the belt cord and the covering rubber, especially at the end portion of the revolving belt layer side, regarding the tread reinforcement of the laminated structure of the inclined belt layer and the revolving belt layer as described above. The present invention aims to provide a pneumatic radial tire which is improved so as to appropriately suppress the development of cracks and enhances the durability performance of the belt structure.

It is also an object of the present invention to enhance the durability performance of the belt structure which can prevent the cord breakage of the revolving belt layer appropriately.

[0014]

SUMMARY OF THE INVENTION According to the present invention, a large number of cords or filaments extending obliquely with respect to the tire equatorial plane are arranged on the outer periphery of the crown portion of a carcass having a toroidal shape extending over at least a pair of bead cores. One inclined belt layer and at least one orbiting belt layer positioned on the inclined belt layer and forming a winding arrangement of aligned wires substantially parallel to the tire equatorial plane are provided between the tread rubber layer and the tread rubber layer. The elastic modulus of the wire of the loop belt layer is 20
00 kgf / mm ² or more, the bulk modulus of the rubber covering the alignment wires of the orbiting belt layer is 200 kgf / mm ² or more, and within 10% of the belt width at the side end of the orbiting belt layer. The pneumatic radial tire is characterized in that the alignment wire is wavy in the region of.

Here, the aligning wire of the orbiting belt layer is made of steel, and in particular, the aligning wire is made of a steel cord having a twisted structure of <1 × N> or <1 + N> where N represents a positive integer. The alignment wire of the orbiting belt layer is made of organic fiber, the cord or filament of the inclined belt layer is made of steel wire, and the inclination angle of the cord or filament of the inclined belt layer with respect to the tire equatorial plane is 15 to 45 °. Ranges are also included.

[0016]

1 (a) and 1 (b) show a pneumatic radial tire according to the present invention applied to a passenger car and a light truck, respectively, along a meridian perpendicular to the equatorial plane of the tire. It is shown in a general cross section.

In the figure, 1 is the whole tire, 2 and 3 are bead cores illustrated as a pair in the illustrated example, and 4 is a toroidal carcass extending between the bead cores 2 and 3, and 5 Represents the equatorial plane of each tire.

In the carcass 4, it is preferable to arrange polyethylene terephthalate (PET) cords at an angle of 70 to 90 ° with respect to the equatorial plane of the tire in accordance with the customary practice, and the outer periphery of the crown portion thereof is shown by a solid line in the figure. To
One inclined belt layer 6 in which a large number of cords or filaments, which are usually made of steel, are arranged in parallel with each other at an inclination angle of 15 to 45 ° with respect to the tire equatorial plane 5.
Also, although it is simply shown by a broken line, a winding arrangement of alignment wires positioned on the inclined belt layer 6 and substantially parallel to the tire equatorial plane becomes one winding layer in FIG. 1A. In (b), the revolving belt layer 7 having two layers in terms of strength is provided between the tread rubber layer 8 and 9 is a groove portion provided in the tread rubber layer.

The orbiting belt layer 7 has an elastic modulus of 2000 Kgf.
Wires of not less than 1 mm2 / mm ² are used at the number of implants of 30 per 50 mm, and the various aspects already described can be appropriately utilized for the specific example of the winding arrangement.

Here, as the alignment wires for reinforcing the circling belt layer 7, monofilaments, cords made by twisting a plurality of filaments or filament bundles made by arranging a plurality of filaments, made of steel or organic fibers, are used. Can be used.

As described above, the problem that occurs in the case where the tread rubber is simply reinforced by winding the revolving belt layer 7 on one inclined belt layer 6 is, as described above, a wire in the side end region of the revolving belt layer 7. Since cracks generated at the interface between the rubber and the coating rubber easily propagate in the circumferential direction along the wire, it is important to suppress the growth of the cracks at the interface. Then, in order to prevent the crack from propagating at this interface, the following measures are effective. (A) The apparent length of the interface is increased to increase the crack propagation distance over the entire circumference of the tread. This is because the crack growth rate is a constant value determined by the physical properties of the rubber, and thus the life up to the tread chunk is finally extended. (B) Furthermore, in order to first prevent the cracks generated at the interface between the wire and the covering rubber from growing in the circumferential direction, a rubber different from the covering rubber in the crack propagation direction, specifically, a tread. Place the rubber. That is, cracks are prevented from propagating by alternately arranging the coating rubber and the tread rubber of the wire of the circulating belt layer 7 in the circumferential direction, which is the direction of crack propagation.

To realize the above (a) and (b),
10% of the belt width at the side edge of the loop belt layer
It is essential to make the alignment wire arranged in the inner region wavy. That is, the belt structure corresponding to each of the tires shown in FIGS.
As developed and shown in (b), the wire 10 arranged in a region SW within 10% of the belt width W from the side edge of the revolving belt layer 7 is formed in a wavy shape. Then, conventionally, a crack (see FIG. 3 (a)) generated at the interface between the wire and the covering rubber in the side end region of the circulating belt layer 7 and propagating along the wire is tread. It is blocked by the rubber (see FIG. 3 (b)).

Here, the reason why the area SW is set within 10% of the belt width W is that if the area SW is expanded to a range exceeding 10%, the circumferential rigidity of the shoulder portion of the tread is lowered, and the shoulder portion is particularly high speed running. This is because it becomes difficult to suppress the protrusion. The lower limit of the region SW does not have to be particularly set, but at least the wire arranged at the outermost side of the orbiting belt layer 7 needs to be wavy.

The waveform applied to the wire 10 is shown in FIG.
, The wave height d is 0.5 mm or more and the wavelength l is 5
A thickness of 0 mm or less is preferable for suppressing the development of cracks. Because, when the wave height d is less than 0.5 mm, the above-mentioned effect of "making the crack propagation distance longer" is hardly obtained, and when the wavelength l exceeds 50 mm, the axial direction of the cord becomes almost the same as the circumferential direction. However, the effect of “preventing crack growth” described above cannot be expected. On the other hand, the upper limit of the wave height d is set to 5 mm in order to secure the rigidity for effectively suppressing the protrusion, and the lower limit of the wavelength l is not necessary for the wire at the stage of tire manufacturing when l is small. 10 to prevent wire breakage due to residual stress
mm is preferable.

If the wire at the side end of the orbiting belt layer is wavy, it is easy to move the wire, which may cause wire breakage due to local buckling. It is necessary to suppress the movement of the wire by setting the bulk modulus of the resin to 200 Kgf / mm ² or more. On the other hand, it is necessary that the bulk modulus of the coated rubber is preferably 500 Kgf / mm ² or less, and if it is higher than this, the viscosity of the rubber becomes too high, which causes a problem in the extrusion step.

Regarding this buckling, FIG.
When the pneumatic radial tire 1 is loaded with a load, the tread rubber layer 8 is
The belt 11 and the belt 11 receive a compression force in the tire radial direction due to the tire internal pressure P1 and the ground contact pressure P2, and a compression force 14 in the width direction of the tire due to the collapse of the side portion 12 indicated by the arrow 13. If the bulk modulus of the rubber is not sufficient in the fully compressed state, which is also subject to the tangential compressive force of the tire, the filament movement becomes large, causing local buckling, which easily causes the steel filament to break. .

The bulk elastic modulus of the coated rubber is shown in FIG. 6 (a).
As shown in Fig. 6, a rubber test piece was filled into the cavity of a steel jig 15 having a cylindrical cavity having an inner diameter d of 14 mm and a height h of 28 mm, and the jig 15 was closed as shown in Fig. 6 (b). The load W is applied to the upper and lower surfaces of the rubber test piece at a speed of 0.6 mm / min after being set in the tensile / compression tester 16 and the displacement amount at this time is measured by the laser 17, and the load and the displacement are measured. It will be calculated from the relationship.

[0028]

EXAMPLES The present invention relates to a pneumatic radial tire of each size of 195/65 R14 {see FIG. 1 (a)} and 195/85 R16 12PR {see FIG. 1 (b)} for passenger cars and light trucks, respectively. Applied as.

In any case, the carcass 4 was formed by driving polyethylene terephthalate (PET) cord (1500d / 2) at 90 ° to the tire equatorial plane at 51.7 pieces / 50 mm, a passenger car tire had one ply, and a small truck. In that case, two plies were arranged.

The inclined belt layers 6 each have a cord structure of 1
3 × 5 × 0.23 mm, 1 + 6 × 0.28 m steel cords at an angle of 30 ° to the tire equatorial plane
7 / 50mm (1 × 5 structure), 24 / 50mm (1 + 6)
(Structure) was formed into one layer.

The orbiting belt layer 7 is formed by arranging a steel wire or an organic fiber wire in a spiral helix structure, in which the width of the orbiting belt layer 7 of a passenger car tire is 140 mm, and the orbiting belt layer 7 for a small truck tire, Width is 10
The narrower two layers of 0 mm and 30 mm were placed in the center of the tread. In any case, according to the place shown in FIG. 2, the wire at the side end of the orbiting belt layer is wavy,
The following high-speed durability test and durability test were performed.
The same test was performed on a tire in which the wire at the side end of the orbiting belt layer was linear.

(1) High-speed durability test US standard FMVSS No. Performed by the step speed method according to the test method of 109, that is, by increasing the speed every 30 minutes until a failure occurs, measuring the speed (km / h) when the failure occurs, and measuring the conventional tire. The value was displayed as an index with 100. The larger the number, the better.

The conventional tire 1 has a cord structure of 1 ×.
A plurality of 5 × 0.23 mm steel cords are laminated on the tire equatorial plane 5 at an angle of ± 22 ° so that the steel cords are laminated to each other, and the two inclined belt layers are arranged on the inclined belt layer. The tire structure for passenger cars formed by the cap layer described above and the conventional tire 2 have a cord structure of 1 + 6 ×
The first layer having a width of 125 mm in which a plurality of steel cords of 0.28 mm are arranged at an angle of + 30 ° with respect to the tire equatorial plane 5 and the steel cord having a cord structure of 1 + 6 × 0.28 mm are attached to the tire equatorial plane. 5, a second layer having a width of 100 mm arranged at an angle of −30 ° with respect to No. 5 is sequentially laminated, and is formed by a cap layer arranged on the inclined belt layer.

(2) Durability test A maximum load specified by JATMA was applied at a tire internal pressure of 1.0 Kgf / cm ² and the tire was run for 4 hours at a slip angle of 8 °, after which the tire was disassembled and the tire was rotated in the circumferential direction. Whether or not cord breakage occurred in the belt layer was investigated and durability was evaluated. The test results are summarized in the following table.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

According to the present invention, by making the wire at the side end portion of the revolving belt layer wavy, cracks generated at the interface between the wire and the covering rubber in the side end region of the revolving belt layer are generated. It is possible to effectively prevent circumferential progress along the wire. In addition, by setting the bulk elastic modulus of the covering rubber in the circumferential belt layer to 200 Kgf / mm ² or more, it is possible to prevent cord breakage in the circumferential belt layer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a typical pneumatic tire for passenger cars and a pneumatic tire for light trucks according to the present invention.

FIG. 2 is an explanatory diagram of a circulating belt layer.

FIG. 3 is an explanatory diagram of a wire at an end portion of a circulating belt layer side.

FIG. 4 is a diagram showing a shape of a wire.

FIG. 5 is an explanatory diagram of forces acting on a tread and a belt when a load is applied to a tire.

FIG. 6 is an explanatory diagram of a method for measuring the bulk modulus of rubber.

[Explanation of symbols]

 1 Pneumatic tire 2, 3 Bead core 4 Carcass 5 Tire equatorial plane 6 Inclined belt layer 7 Orbiting belt layer 8 Tread rubber layer 9 Groove part 10 Wire 11 Belt 12 Side part 13 Compressive force

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B60C 9/20 7504-3B B60C 9/20 D

Claims (6)

[Claims] 1. A single inclined belt layer in which a large number of cords or filaments extending obliquely with respect to the equatorial plane of a tire are arranged on the outer periphery of a toroidal carcass crown portion which extends between at least a pair of bead cores, and At least one orbiting belt layer, which is located on the inclined belt layer and is a winding arrangement of aligned wires substantially parallel to the equatorial plane of the tire, is provided between the tread rubber layer and the elastic band of the orbiting belt layer. Is 2000 kgf / mm ² or more, the bulk modulus of the rubber covering the aligned wires of the orbiting belt layer is 200 kgf / mm ² or more, and 10% of the belt width at the side end of the orbiting belt layer. A pneumatic radial tire characterized in that the alignment wires are wavy in the area within. 2. The pneumatic radial tire according to claim 1, wherein the alignment wire of the orbiting belt layer is made of steel. 3. The pneumatic radial according to claim 1 or 2, wherein the aligning wire of the orbiting belt layer comprises a steel cord having a twisted structure of <1 × N> or <1 + N>, where N represents a positive integer. tire. 4. The pneumatic radial tire according to claim 1, wherein the alignment wire of the orbiting belt layer is made of an organic fiber. 5. The pneumatic radial tire according to claim 1, wherein the cord or filament of the inclined belt layer is made of steel wire. 6. The pneumatic radial tire according to claim 1, wherein an inclination angle of the cord or filament of the inclined belt layer with respect to the tire equatorial plane is in the range of 15 to 45 °.