JPH11222010A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity and also enhance high speed durability without increasing weight. SOLUTION: A belt layer 7 arranged on the peripheral side of a carcass layer 4 in a tread part 1 is constituted of a center belt layer 8 in a tire center region X and a side belt layer 9 in both side regions Y. The center belt layer 8 is so formed that one or a plurality of reinforcing cords f drawn in order, while folded back between both end parts, is continuously wound in a tire peripheral direction and also crossed with each other between layers. A double side belt layer 9 is formed in such a constitution that one or a plurality of reinforcing cords drawn in order is continuously helically wound at 5 deg. or less stilt relating to the tire peripheral direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, and more particularly, to a pneumatic radial tire while improving productivity.
The present invention relates to a pneumatic radial tire with improved high-speed durability without increasing weight.

[0002]

2. Description of the Related Art In general, a belt layer of a pneumatic radial tire is formed by bias-cutting a belt-shaped body calendered so that a plurality of aligned steel cords are impregnated with unvulcanized rubber. The strip is joined and wound up as a long belt material, which is unwound at the time of use, cut to the length of the belt layer, and spliced around the base tire so that the ends partially overlap each other and wound. In addition, at least two layers are stacked such that steel cords intersect each other between the layers. However, in the belt layer configured as described above, since cut ends of the reinforcing cord are formed at both ends of the belt layer, there are portions where the cord and the rubber are not bonded, and the interlayer shear strain is large. In addition, when running at high speed, a phenomenon in which the belt layer rises outward due to centrifugal force occurs at both ends, so that separation occurs easily at the edge of the belt layer, and high speed durability is poor.

Conventionally, as a countermeasure, an organic fiber cord such as a nylon cord is continuously wound around at least both ends of the belt layer at an angle of about 0 ° in the circumferential direction of the tire to prevent the end of the belt layer from rising. There is a proposal of a technique that suppresses this and improves high-speed durability. However, providing a belt cover layer such as a nylon cord has a problem in that the weight is greatly increased. In addition, the belt structure for joining the bias-cut steel cord strips has a problem in that it takes a lot of time to manufacture and many steps relying on manual work, so that productivity cannot be easily increased.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire capable of improving high-speed durability without increasing weight while improving productivity.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a pneumatic radial tire having a belt layer on which reinforcing cords are arranged on an outer peripheral side of a carcass layer of a tread portion. The center belt layer and the side belt layers adjacent to each other on both sides of the center belt layer are separately formed, and one or more aligned reinforcing cords of the center belt layer are folded between both ends of the center belt layer. While being wound continuously in the circumferential direction of the tire, the reinforcing cords are formed in even layers so that the reinforcing cords intersect each other between the layers. It is characterized in that it is configured to be wound continuously spirally at an inclination angle of 5 ° or less with respect to the direction.

[0006] As described above, the belt layer is divided into the center belt layer in the tire center area and the side belt layers in both side areas, and the reinforcing cord is folded back at both ends and continuously wound in the tire circumferential direction. The both side belt layers are configured such that the reinforcing cords are continuously spirally wound at 5 ° or less with respect to the tire circumferential direction, thereby increasing the tire circumferential hoop effect and cutting the cut ends of the reinforcing cords with the belt. Since it is not located at the end of the layer, it is possible to reduce the rising phenomenon of the end of the belt layer at the time of high-speed traveling and the interlayer shear distortion at the end of the belt layer, and to greatly improve the edge separation resistance of the belt layer. it can.

In addition, since it is only necessary to improve the belt structure without providing any reinforcing layer such as a belt cover layer,
Since the reinforcement layer is continuously wound to form the belt layer without increasing the weight, the productivity can be significantly improved as compared with the case of attaching the bias cut pieces. In addition, since the steering stability can be improved by increasing the tire circumferential rigidity of the side belt portion, and the tire vibration frequency is moved to a high frequency side,
High frequency road noise can be improved. Further, since there is no splice in the belt layer, the riding comfort can be improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows an example of a pneumatic radial tire according to the present invention, with only one half section from the tire center line CL. 1 is a tread portion, 2 is a bead portion, and 3 is a sidewall portion. One carcass layer 4 in which reinforcing cords are arranged in the tire radial direction is arranged inside the tire. Carcass layer 4 has both ends 4a
Are folded from the tire inner side to the outer side so as to sandwich the bead filler 6 around a bead core 5 embedded in the left and right bead portions 2. Two belt layers 7 are embedded on the outer peripheral side of the carcass layer of the tread portion 1.

In the pneumatic tire configured as described above, the belt layer 7 is formed so that the center belt layer 8 disposed in the tire center area X and the two side belt layers 9 disposed in the side areas Y on both sides thereof are separated from each other. Is configured. As shown in FIG. 3, when the green tire is formed, one or more reinforcing cords (not shown) are aligned in parallel and the strip material S bundled with the unvulcanized rubber is uncured. On the carcass layer 4 of sulfur, it is formed by continuously winding in the tire circumferential direction at both ends of the belt width within the width of the tire center region X via wave-shaped bending. The winding method of the strip material S may be a plurality of times while being shifted by a strip width of the strip material S while being meandering in a wave shape in the tire circumferential direction,
Alternatively, it may be wound up so that the strips S are finally adjacent to each other while being wound so as to be shifted at a pitch several times the strip width. The center belt layer 8 having the structure in which the reinforcing cord is folded between both ends in this manner does not have the cut ends of the reinforcing cord at both ends, and the center belt layer 8A, in which the reinforcing cord intersects between the upper and lower two layers, 8B can be formed.

The center belt layer 8 is formed, for example, by forming a tubular body in which a strip material S 'is wound up on a rotary drum in a helical manner so as to be continuously in close contact therewith. And flattened cylindrical belt material A obtained by crushing along the longitudinal direction as shown in FIG. 4 may be assembled and formed at the time of green tire molding before vulcanization. The center belt layer 8 is folded between both ends of the center belt layer by winding the reinforcing cord f in a flat spiral shape.

Further, as shown in FIG. 5, the center belt layer 8 is formed by zipping the strip material S 'on the unvulcanized carcass layer in the tire circumferential direction with folding back at the belt width end. The belt material A 'obtained by continuously winding the belt material A' may be used. In this center belt layer 8,
When the reinforcing cord f is wound in a zigzag shape, it is folded back between both ends of the center belt layer so that the cut ends are not located at both ends. In addition, it is more preferable that the winding start end and the winding end of the strip material S ′ are located at the center of the center belt layer 8 from the viewpoint of durability.

On the other hand, the side belt layer 9 is formed of a reinforcing cord g.
Is continuously spirally wound so that the angle of inclination is substantially 0 ° with respect to the tire circumferential direction, specifically, the inclination angle is within 5 ° with respect to the tire circumferential direction. . The side belt layer 9 is formed, for example, by forming a strip material Q in which one or a plurality of reinforcing cords g aligned in parallel are buried in unvulcanized rubber at the time of molding a green tire. It can be obtained by continuously winding the side region Y a plurality of times without any gap.

Although the center belt layer 8 and the side belt layer 9 are formed by independent strip members Q, S, S ', they may be formed by one continuous strip member. Also, the center belt layer 8
The number of strip materials S, S ′ for forming the sheet is not limited to one, and the winding time may be shortened by starting to wind simultaneously from a plurality of places by a plurality of strip materials.

As described above, according to the present invention, the belt layer 7 and the center belt layer 8 in the tire center area X and both side areas Y
And the center belt layer 8 is wound around the center belt layer 8 in the tire circumferential direction while the reinforcing cord f is folded between both ends. In this case, the center belt layer 8 and the side belt layer 9 have no cut ends of the reinforcing cords at both ends thereof, and the center belt layer 8 and the side belt layer 9 do not have the cut ends at the time of high-speed running. Since the rising behavior is suppressed, the edge separation of the belt layer can be largely suppressed.

Further, since the reinforcing cord g is wound substantially at 0 ° in the tire circumferential direction of the side belt layer 9, the rigidity in the tire circumferential direction is greatly improved.
Along with improved steering stability, high-frequency road noise can be improved. In addition, since the belt layer 7 has the above-described structure, a structure having no splice portion is provided, so that riding comfort can be improved.

Further, since the reinforcing cords f and g are continuously wound to form the belt layer, the productivity can be remarkably improved as compared with the conventional case of attaching the bias cut pieces. In the present invention, as the width Y of the side belt layer 9, the total width thereof is 15 to
35%, preferably in the case of a symmetrical structure,
The width Y per one side is 7.5 to 17.5% of the total belt width Z.
It is better to The width X of the center belt layer 8 is preferably 65 to 85% of the total belt width Z.

In the embodiment shown in FIG. 1, the boundary between the center belt layer 8 and the side belt layer 9 is provided so as to abut each other without overlapping the ends, but this boundary is slightly overlapped. Or may be separated by some distance. However, the overlap amount at the time of overlapping is preferably up to 5% of the total belt width Z. From the viewpoint of tire production, it is preferable that the center belt layer and the side belt layer slightly overlap each other in the state of an unvulcanized tire, and that the above-mentioned overlap amount is corrected to zero during lift in vulcanization molding.

Center belt layer 8 and side belt layer 9
Any known high-strength, high-modulus cords used in conventional belt layers can be used as the reinforcing cords. For example, it is preferable to use an organic fiber cord having a tensile modulus of 1500 kgf / mm ² or more such as aramid fiber, polyparaphenylene benzobisoxazole (PBO) fiber, polyethylene naphthalate (PEN) fiber, etc., in addition to steel cord and steel filament. Can be.

In the present invention, the strip materials Q, S, and C used for forming the center belt layer 8 and the side belt layer 9 are formed.
It is preferable to use S 'having a width of 5 mm or more from the viewpoint of securing good productivity. The upper limit of the width is preferably 15 mm or less in the case of the strip material S of the center belt layer 8 accompanied by a wave-like bending, and the bending becomes difficult if it is more than 15 mm. In the case of a strip material S 'which is folded back in a zigzag shape or wound in a flat spiral shape, the thickness is preferably 60 mm or less. Above this, the area of the exposed end of the reinforcing cord is increased, and the durability is reduced. In the case of the strip material Q, there is no particular limitation as long as the productivity is not hindered.
For example, it can be 10 mm.

In particular, as the reinforcing cord used for the side belt layer, it is desirable to use a reinforcing cord which follows the green tire when it is lifted during vulcanization, because the tire expands in diameter. For example, as shown in FIGS. 6 and 7, a single-stranded steel cord M in which a plurality of (five in the figures) strands e spirally formed into a 1 × n structure can be preferably used.

This single twisted steel cord M has a molding rate of 1
It is set to a large range of 40 to 210%, and the rubber permeability into the cord is extremely high. However, single twist 1 ×
The mold ratio of the n-structure is as follows: when the outer diameter of the cord is 100 when the n strands are twisted concentrically without any gap, the spiral outside of the strand when the individual strand alone is taken out. Defined as diameter.

The above single-strand steel core after tire inflation
In the mode M, a plurality of strands e are formed in a cross section in the tire radial direction.
As shown in FIG. 6, the virtual circle indicated by the dotted line exceeds 180 °.
Instead, they are arranged in a substantially C-shape arranged in an arc shape. The number of strands
n, wire diameter d, embedded in tread 1 after tire inflation
Distance k between the centers of adjacent strands e in the separated state _1,
k_2,k_3,k_Four・ ・ K_n-1And the spiral wire arrangement
The outer diameter D of the single twisted steel cords M forming a row is represented by the following formula: k <1.16d (n−1) (1) 1.6 <dn / (D−d) <3.0 (2) Should be satisfied. In FIG. 7, R is
Rubber filled in the single twisted steel cord M.

Such a single-twisted steel cord M does not hinder uniform deformation of the inner carcass layer since the stress generated in the initial strain region is relatively small, and can follow the tire inflation diameter during vulcanization. While the single-twisted steel cord M can be elongated, the elongation is suppressed after the swelling, so that the belt layer can exhibit a slack effect. When Δk is apart from 1.16d (n−1) or more, the deformation of the side belt layer to the outside is large, and it becomes insufficient to increase the tire circumferential rigidity. The lower limit of Σk is
A state in which the individual wires e are in contact without being entangled, that is, d
(N-1) or more may be used.

Even when the value of dn / (D−d) is less than 1.6, the rigidity in the circumferential direction of the tire becomes insufficient. On the other hand, when the value of dn / (D−d) becomes 3.0 or more, the steel cord M bites into the carcass layer at the time of expansion. And the durability is significantly reduced. The number of strands of the single twisted steel cord M is preferably 3 to 8. 3
If the number is less than eight, processing is difficult. Conversely, if the number is more than eight, the wires are difficult to be arranged in an arc shape, and uneven stress is applied to the wires, which is not preferable. Each strand e may have the same diameter or different diameters. When the wire diameters are different, the wire diameter d in the above equation is the average of them.

The side belt layer 9 may use a so-called high-elongation cord having a short-pitch multi-twist structure in place of the above-described single-twisted steel cord. Alternatively, it may be processed in a wavy shape and embedded in the unvulcanized strip material Q. The angle of the reinforcing cord f of the center belt layer 8 with respect to the tire circumferential direction is preferably in the range of 15 to 45 °.

In the above-described embodiment, an example in which the number of the belt layers 7 is two has been described, but the present invention is not limited to this. Although the center belt layer is necessarily an even number, the side belt layer may be a single layer or a plurality of layers, and may be an odd number or an even number.

[0027]

Example 1 A tire having a common tire size of 195 / 70R14 and provided with a center belt layer and a side belt layer shown in FIG. The present invention tire 2 having the belt structure shown in FIG. 5, the invention tire 3 having the belt structure shown in FIG. 5, the comparative tire 1 in which the belt layer is constituted by the belt layer shown in FIG. 5 over the entire width of the belt, and the center belt layer of the invention tire 1 Comparative tire 2 having a cut end of a reinforcing cord at a belt edge portion as a comparative tire 2, a conventional tire 1 having a belt layer constituted of two belt layers having a cut end of a reinforcing cord at a belt edge portion, And the conventional tire 1
, A conventional tire 2 in which two belt cover layers were arranged on the outer periphery of the belt layer was manufactured.

In each of the test tires, a steel cord was used as the reinforcing cord of the belt layer, and the amount of the cord used was the same. The cord structure and the number of ends are as shown in Table 1. The inclination angles of the reinforcing cords inclined with respect to the tire circumferential direction are each 24 °. The width of the center belt layer in the tire of the present invention is 85% of the total belt width.
%, The width of the side belt layer is 7.5 of the total belt width.
%, Which is symmetric. For the belt cover layer of the conventional tire 2, a nylon cord having an 840d / 2 structure was used.

The test tires were evaluated for high-speed durability, weight, steering stability, ride comfort, high-frequency road noise, and productivity under the following measurement conditions. The results shown in Table 1 were obtained. Obtained. High-speed durability Each test tire was mounted on a rim with a rim size of 14 × 5 1/2 JJ, the air pressure was set to 220 kPa, and the drum tester was mounted on a rotating drum having a diameter of 1707 mm, and the load load was 4.4 kN.
After running under the conditions of (450 kg) in accordance with the JATMA high-speed durability test, the speed was increased by 8 km / hr every 30 minutes, and the distance until a tire failure occurred was measured. Was evaluated with an index value of 100. The higher the value, the better the high-speed durability. Weight The weight of each test tire was measured.
Was evaluated with an index value of 100. The higher this value, the more
Indicates light weight. Driving stability and ride comfort Each test tire was mounted on a rim with a rim size of 14 × 5 1/2 JJ, the air pressure was adjusted to 180 kPa, and the test tire was mounted on a 2500 cc vehicle. The evaluation was made using an index value with the conventional tire 1 being 100. The higher the value, the better the performance. High-frequency road noise Each test tire was mounted on a vehicle under the same conditions as above, and the sound pressure level of high-frequency road noise was measured when the vehicle traveled straight on a pavement at a speed of 50 km / h.
The evaluation was performed using an index value of 00. The higher this value is, the lower the high frequency road noise is. Productivity In each of the test tires, the conventional tire 1 was evaluated based on the number of tires produced per unit time with an index value of 100. The higher the value, the higher the productivity.

[0030]

[Table 1]

As is clear from Table 1, the tire 1 of the present invention
Nos. 3 to 3 indicate that the high-speed durability can be increased to the same level as that of the conventional tire 2 provided with the belt cover layer. Moreover, the weight does not increase unlike the conventional tire 2. In addition, it can be seen that driving stability, ride comfort, high-frequency road noise, and productivity are also excellent. Example 2 Test tires 1 to 5 were prepared by changing the tire size to the same as above and changing the ratio of the width of the center belt layer and the side belt layer to the total belt width in the above-described tire 1 of the present invention as shown in Table 2. did.

Each of the test tires was subjected to high-speed durability, weight, steering stability, ride comfort, high-frequency road noise, and productivity evaluation tests under the measurement conditions described above. The results shown in Table 2 were obtained. Was.

[0033]

[Table 2]

From Table 2, it can be seen that the width of the center belt layer is 65 to 85% of the total belt width, and the width of the side belt layers is 7.5 to 17.5% of the total belt width (15 to 3 in total left and right width).
5%).

[0035]

As described above, in the pneumatic radial tire of the present invention, the belt layer is divided into three parts: a center belt layer in the tire center area and side belt layers in both side areas. A structure in which both side belt layers are continuously spirally wound at an angle of substantially 0 ° with respect to the tire circumferential direction with a configuration in which the reinforcing cord is continuously wound in the tire circumferential direction while being folded between the end portions. Accordingly, it is possible to avoid the concentration of the interlayer shear strain at the end of the belt layer, to suppress the rising phenomenon at the time of high-speed running, to greatly improve the edge separation resistance, and to improve the high-speed durability. In addition, since the productivity is improved by forming the belt layer by continuous winding of the reinforcing cord, it is only necessary to change the structure of the belt layer without providing a reinforcing layer such as a belt cover layer.
An increase in weight can be avoided.

[Brief description of the drawings]

FIG. 1 is a tire meridian half sectional view showing an example of a pneumatic radial tire of the present invention.

FIG. 2 is a schematic explanatory view of a belt layer of FIG.

FIG. 3 is a perspective view showing an example of a method of forming a center belt layer.

FIG. 4 is a main part perspective view showing another example of a method of forming a center belt layer.

5A is a plan view of a main part showing another example of a belt material used for a center belt layer, and FIG. 5B is a JJ of FIG.
It is arrow sectional drawing.

FIG. 6 is an enlarged cross-sectional view showing one row of a single twisted steel cord after tire inflation used for a reinforcing cord of a side belt layer.

FIG. 7 is a front view of a main part of FIG. 6;

[Explanation of symbols]

Reference Signs List 1 tread portion 2 bead portion 3 sidewall portion 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 center belt layer 9 side belt layer A, A 'belt material CL tire center line M single-stranded steel cord Q, S, S' Strip material X Tire center area Y Side area Z Total belt width f, g Reinforcement cord

Claims (4)

[Claims] 1. A pneumatic radial tire having a belt layer in which reinforcing cords are arranged on an outer peripheral side of a carcass layer in a tread portion, wherein a center belt layer in which the belt layer is arranged in a tire center region and a center belt layer adjacent to both sides thereof are respectively provided. Each of the center belt layers is divided from both side belt layers, and one or more aligned reinforcing cords are continuously wound in the tire circumferential direction while being folded between both ends of the center belt layer, The reinforcing cords are formed in even layers so that the reinforcing cords cross each other between the layers, and one or more aligned reinforcing cords of the two side belt layers are continuously formed at an inclination angle of 5 ° or less with respect to the tire circumferential direction. A pneumatic radial tire that is configured to spirally wind around a tire. 2. The pneumatic radial tire according to claim 1, wherein the reinforcing cord is folded between both ends of the center belt layer by being wound in a wave shape, a zigzag shape, or a flat spiral shape. 3. The pneumatic radial tire according to claim 1, wherein a total width of the side belt layers is 15 to 35% of a total belt width. 4. The reinforcing cord of the belt layer is made of a steel filament, a steel cord, and a tensile modulus of 1500 kg.
The pneumatic radial tire according to claim 1, 2, or 3, which is an organic fiber cord having an f / mm ² or more.