JP2675324B2 - Pneumatic radial tire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic radial tire in which a metal single wire cord coated with an elastomer is applied to a cord layer of a belt, and particularly, cord breakage of the belt cord layer is avoided. Thus, the present invention relates to a pneumatic radial tire with improved belt durability without sacrificing rolling resistance and motion characteristics.

(Prior Art) The cord layer of a belt in a radial tire is a twisted cord represented by 1 × 4 or 1 × 5, which is formed by twisting four or five filaments having a diameter of about 0.20 mm to 0.30 mm. , Or 7 outside the two filaments
A twisted wire cord represented by 2 + 7, which is formed by twisting filaments of a book, is used, and the tire using such a cord has almost satisfactory motion performance, durability performance and rolling resistance.

However, recently, as the performance of passenger cars and the like has advanced, it is demanded that the tires to be mounted also have better performance, that is, the exercise characteristics be improved and the rolling resistance that contributes to low fuel consumption be reduced. .

Japanese Unexamined Patent Publication No. 57-198101 discloses a belt in which the center distance between the cords in the radial direction of the tire does not exceed 1.0 mm between the two cord layers made of twisted cords or single-strand steel wire cords (hereinafter referred to as single-cord cords). , Further 10c
There is a description about tires with 60 or more drivings per m. This tire reduces the volume of rubber that coats the cord by keeping the distance between the cord centers of the belt cord layer to 1.0 mm or less, and reduces the energy loss due to the rubber by the amount of the reduction of the rubber, thus providing good rolling resistance. It aims to secure.

(Problems to be Solved by the Invention) This document describes an example in which the number of twists of a metal cord is reduced to 5, 4, and 3 and an example in which the cord is a single wire. According to this, as the number of twists is reduced, both the energy loss due to the rubber that has penetrated inside the cord and the energy loss between cords are reduced, and extremely good rolling resistance is obtained. Compared to the stranded cord, the energy loss due to the rubber that penetrates inside the cord and the energy loss between cords can be made extremely small, and better rolling resistance can be obtained, so a belt structure suitable for high performance tires Has been found to be.

However, a tire provided with a belt of a single-wire cord layer having good rolling resistance, the cord is easily fatigued,
For example, if a cord fatigue test is carried out due to sudden cornering of a vehicle, which is called a so-called figure-eight turn test, a problem remains where the cord is frequently broken.

As for the cord breakage state by this test, as the number of twisted wires of the twisted wire cord decreases, and the single wire cord breaks more easily than the twisted wire cord, the desired movement performance and rolling resistance and this cord It has a property that is contrary to the durability against fatigue fracture (hereinafter referred to as fatigue resistance). As a method to improve the fatigue resistance of this cord, increasing the rubber gauge between cords and the number of driven cords can be considered.First, increasing the rubber gauge between cords suppresses the breaking of cords considerably, but rolling It becomes a cause of worsening the resistance. Next, increasing the number of driving can reduce the input applied to the cord and suppress the breaking of the cord, but the increased amount of driving increases the weight and impairs the rolling resistance.

Therefore, an object of the present invention is to propose a tire structure capable of improving both performance such as kinetic characteristics and rolling resistance and fatigue resistance of a belt cord.

(Means for Solving the Problem) The cord breaking phenomenon in the figure 8 turning test is caused by buckling deformation (flexural deformation) of the tread portion composed of the carcass, the belt, the tread rubber, etc., which occurs when the tire rolls under load. It is known that this occurs due to the fact that buckling deformation begins to occur and the critical compressive force of the belt Ncritica
l can be expressed by the following equation, where k is the compression spring constant of the tread rubber and D is the belt bending rigidity.

From the above equation, it can be seen that it is necessary to increase the tread rubber compression spring constant k or the belt bending rigidity D in order to increase the buckling occurrence critical compression force to suppress cord rupture. If the physical properties of the tread rubber are changed in the increasing direction, the tire dynamic characteristics such as the steering performance on wet and dry road surfaces, the vibration riding comfort performance, etc., which are the original required characteristics of the tread rubber, deteriorate.

On the other hand, in order to increase the belt bending rigidity D, the flexibility of change is limited in the case of a single wire cord without twisting, and it can be achieved only by increasing the diameter of the cord. However, when the filament diameter of the single wire cord is increased in the radial tire for passenger cars, It is not a good idea because it significantly reduces the ride comfort.

Therefore, a method of avoiding the cord break under large input and the belt end separation on a general road by adding a third component in addition to the tread rubber and the single wire cord was examined.

That is, various experiments were carried out on tires in which a belt bending rigidity D was increased by disposing a reinforcing layer on the outer side in the tire radial direction of the belt where buckling deformation occurs and cord breakage, at the end portion in the tread width direction over the entire circumference of the tire. As a result, it was found that the fatigue resistance of the cord was improved, the belt end separation did not occur due to general running, and the motion characteristics and rolling resistance were also good, and the present invention was completed.

The present invention relates to a radial carcass that reinforces a pair of sidewall portions and a tread portion between bead cores embedded in a pair of bead portions, and a belt of a two-layer metal single wire cord layer that reinforces the tread portion on the outer periphery of the carcass. And the single-wire cords in each layer of the belt are arranged in parallel with each other in the layer and are 15 to 30 with respect to the tire equatorial plane.
In a pneumatic radial tire that is inclinedly arranged at an angle of ゜, each layer of the belt has a single wire cord having a diameter within a range of 0.28 to 0.70 mm arranged at a driving number within a range of 30 to 120 per 50 mm. The inner cord layer near the carcass has the maximum width of the belt, and along the outer circumference of the belt, the innermost cord layer extends from at least the center of the ground contact width of the tread portion to the ground end toward the ground end. An organic fiber cord reinforcing layer extending to a position that greatly exceeds the edge of the cord layer is arranged, and the reinforcing layer is formed by spirally winding around the belt with the number of driven cords being 40 to 70 per 50 mm, and having the maximum width cord. The distance (t) between the surface that smoothly contacts each cord of the reinforcing layer in the region that exceeds the edge of the layer and the surface that smoothly contacts each cord of the maximum width cord layer in the region outside is the outer cord. Near the edge of the layer Pneumatic radial tire characterized by having a distance (g) longer than the distance (g) between the surface of each of the width code layers that makes smooth contact with the outside of the cord and the surface of each of the outer code layers that makes smooth contact with the inside of the cord. And a radial carcass that reinforces the pair of sidewall portions and the tread portion between the bead cores embedded in the pair of bead portions, and at least two layers of metal that strengthen the tread portion between the outer periphery of the carcass and the tread rubber. A single-wire cord layer belt, and the single-wire cords of the layer are arranged in parallel with each other in the layer and are arranged inclining at a cord angle of 15 to 30 ° with respect to the tire equatorial plane. In the tire, each layer of the belt is formed by arranging single wire cords having a diameter within the range of 0.28 to 0.70 mm at a driving number within the range of 30 to 120 per 50 mm. The inner cord layer closer to the dust has the maximum width of the belt, and along the outer circumference of the belt, the belt width maximum cord layer end extends from the middle position between the center and the ground end of at least the tread portion toward the ground end. The rubber of the reinforcing rubber layer has a thickness in the range of 2 to 5 mm and a 25% modulus of 20 to 70 k.
It is a pneumatic radial tire characterized by being in the range of g / cm ² .

Now, FIG. 1 illustrates a structure of a pneumatic radial tire according to the present invention in a sectional view.

In the figure, 1 is a radial carcass, 2 is a belt, 3 is a reinforcing layer, 4 is a tread rubber, and 5 is a bead core.

The radial carcass 1 reinforces the pair of sidewall portions and the tread portion across the bead cores 5 embedded in the pair of bead portions.

Belt 2, which strengthens the tread, has a diameter of 0.28 to 0.70 mm.
It consists of two cord layers 2a and 2b arranged at the outer periphery of the carcass 1 at a tilt angle of 15 to 30 ° with respect to the equatorial plane of the tire and at a driving number of 30 to 120 per 50 mm. The inner cord layer 2a near the carcass 1 has the maximum width of the belt 2. The number of cords to be driven is a value measured in a direction orthogonal to the axis of the cord, and the same applies hereinafter.

First, the reinforcing layer 3 of the present invention comprises a cord layer in which an organic fiber cord is spirally wound around the belt 2 at a driving number of 40 to 70 per 50 mm, and the spiral winding cord layer is the outer periphery of the belt 2. A cord layer extending along at least from the middle position P between the center of the ground contact width L of the tread portion and the ground contact end toward the ground contact ends on both sides and beyond the maximum width cord layer 2a end of the belt 2. The reinforcing layer 3 is an example of a pair of cord layers extending from the substantially intermediate position P toward the grounding ends on both sides. Such a pair of hollowed cord layers is generally called a layer, while the spirally wound cord layer covering the entire width of the tread is called a cap, and both are included in the present invention.

Here, in a region where the reinforcing layer 3 exceeds the end of the inner cord layer 2a having the maximum width of the belt 2, a surface S that is in contact with each cord of the reinforcing layer 3 inside smoothly, and the maximum width cord layer 2a in this region. A distance t (hereinafter, simply referred to as an inter-cord distance t) between each cord and the surface R that is in smooth contact with the outer side is close to the surface R in the maximum width cord layer 2a near the end of the outer cord layer 2b of the belt 2. , It is necessary to make the distance g between each cord of the outer cord layer 2b and the surface (reference numeral omitted) which is in contact with the cord smoothly inside. As described above, it is important to set the distance t to a sufficient length under the relationship of the distance t> the distance g. By providing the distance t, the cord layers 2a, 2b of the belt 2 are provided.
It is possible to prevent the separation at the end portion and the separation of the reinforcing layer 3 from advancing and proliferating with each other and developing into a large interlayer separation.

The reinforcing layer 3 is not limited to the arrangement shown in FIG. 1, but has a two-layer structure (see FIG. 2) in which the spirally wound cord layers of organic fibers are two layers in each side area of the tread, and one layer cord. One cap structure (see FIG. 3) in which the layers are provided over the entire width of the tread portion, and a composite structure in which, of the two cord layers, the cord layer on the outer side in the tire radial direction is the layer, and the inner cord layer is also the cap. (See FIG. 4) and the like can be modified individually or in various combinations.

Next, as the reinforcing layer 3 of the present invention, a reinforcing rubber layer is applied instead of the spirally wound layer of the organic fiber cord described above, as shown in FIG. It is necessary that the rubber of this reinforcing rubber layer has a thickness within a range of 2 to 5 mm and a 25% modulus within a range of ²⁰ to 70 kg / cm ² . The reinforcing layer 3 is, like the spirally wound layer of the above cord, along the outer circumference of the belt 2 from at least the middle position P between the center of the ground contact width L of the tread portion and the ground contact end to both ground contact ends. Opposite belt 2 is a reinforcing rubber layer extending to a position beyond the end of maximum width cord layer 2a, and reinforcing layer 3 shown in the figure is an example of a pair of reinforcing rubber layers extending from substantially intermediate position P toward the grounding ends on both sides. .
Also in the case of this reinforcing rubber layer, the same arrangement as that of the modified example (FIGS. 2 to 4) of the spirally wound layer of the above cord and the modified combination thereof is possible.

(Working) The cord of the conventional belt is more likely to be broken as the number of twists is smaller, and as described above, the single wire cord is most likely to be broken.
Even in the tire applied to the cord layer of No. 2, along the outer periphery of the belt 2, from at least the middle position between the center of the ground contact width of the tread portion and the ground contact end to the position beyond the maximum width cord layer 2a of the belt 2 toward the ground contact end. By arranging the extending reinforcing layer 3, the fatigue resistance of the cord can be improved. The reason is as follows.

When the vehicle makes an 8-figure turn, or more precisely on a lemniskate curve, the tires have a very large slip angle and therefore the tread contact surface is subject to a large flexural deformation (back) on the circumference of the tread. Ring deformation). A tensile force and a compressive force act on both ends of the flexural deformation in the width direction of the tread portion, and the compressive force is naturally applied to the belt 2
The conventional single-wire cord was forced to break because of the effect on the. On the other hand, the spirally wound layer or the reinforcing rubber layer of the organic fiber cord of the reinforcing layer 3 that covers at least the end portion of the belt 2 bears most of the tensile force derived from the bending deformation of the tread portion, and the reinforcing rubber layer is As a result of bearing a large amount of compressive force,
Flexural rigidity against flexural deformation is enhanced, at least flexural deformation of the belt 2 is suppressed, and the compressive force acting on the single-cord cord layer is reduced. Therefore, even a single-cord cord is hardly broken.

In particular, in the case of a thin single wire cord with a diameter of 0.35 mm or less, the bending rigidity of the belt 2 cannot be made higher than that of a normal twisted wire cord, so that the durability against cord breakage and belt end separation is inferior to the conventional twisted wire cord. However, this drawback can be overcome by applying the reinforcing layer 3, and it becomes possible to secure a bending rigidity level higher than the conventional level up to a filament diameter of 0.28 mm. Therefore, the tire having the reinforcing layer 3 and using the single-wire cord exhibits good kinetic characteristics and low rolling resistance.

In addition, the diameter of the single wire cord is set in the range of 0.28 to 0.70 mm, when the length is less than 0.28 mm, the cord breaking resistance and the belt end separation resistance are poor, and the workability is deteriorated because the number of driving is too large. On the other hand, if it exceeds 0.70 mm, the riding comfort of vibration is significantly deteriorated, and more preferably 0.30 to 0.
The range of 40mm is suitable.

The reason for setting the number of single wire cords to be driven per 50 mm within the range of 30 to 120 is that if it is less than 30, sufficient belt rigidity cannot be ensured and shear strain between the cord layers 2a and 2b of the belt 2 becomes large. This is because the cord breaks or the belt end separation occurs, and when the number exceeds 120, the number of drives becomes too large and the actual manufacturing becomes difficult, and more preferably 35 to 80.
The range of the book is suitable.

The material of the single wire cord is advantageously a high carbon steel having a C content of 0.80 to 0.90 wt%.

Further, the cord spacing between the adjacent two layers 2a and 2b of the belt 2, that is, the outer peripheral surface contacting each cord of the innermost maximum width cord layer 2a on the outer side and the inner peripheral surface contacting each cord of the outer cord layer 2b on the inner side. The shortest distance g (the total gauge of the coating rubber between the single-wire cords) between and is 0.8 mm or more, more preferably 1.0 mm or more. The belt end separation resistance and the layers 2a and 2b of the belt 2 are Recommended for increasing the fatigue resistance of single wire cords.

Next, the number of organic fiber cords applied per 50 mm to be applied to the reinforcing layer 3 was set to 40 to 70 because the belt bending rigidity was not sufficient when the number was less than 40 and the weight increased when the number exceeded 70. This is because the rolling resistance increases and the handling stability deteriorates.

Moreover, the thickness of the rubber of the reinforcing rubber layer applied to the reinforcing layer 3 is 2 m.
If the length is less than 2 mm, the effect of improving the fatigue resistance of the single-wire cord is not recognized, and if it exceeds 5 mm, the heat generation property and high-speed durability of the tire are deteriorated, which is not possible.

Even more 25% modulus of the rubber of the reinforcing rubber layer to be applied was 20~70kg / cm ² in the reinforcing layer 3 is sufficient belt rigidity can not be obtained within the thickness of 2~5mm is less than 20 kg / cm ² No
This is because the fatigue resistance is no longer effective.

On the other hand, if it exceeds 70 kg / cm ² , the rubber composition in the unvulcanized state becomes extremely hard, and the workability is greatly reduced, resulting in a marked decrease in productivity, which is not possible.

(Examples) Radial tires for passenger cars of tire size 165 / SR13 were prototyped according to the specifications shown in Table 1, and fatigue resistance, belt end separation resistance, indoor maneuverability, and rolling resistance of each cord were evaluated. did. The results are also shown in Table 1. In the table, tire Nos. 1-12
Is an example according to the present invention, No. 13 to 23 are comparative examples, N
The composition of the rubber layer applied to the reinforcing layer 3 of the tires of Nos. 10 to 12 and No. 23 was as shown in Table 2. The cord angles in Table 1 are shown as inclination angles with respect to a plane orthogonal to the tire equatorial plane.

It can be seen from Table 1 that the tires Nos. 1 to 12 according to the present invention, in which the single-wire cord layer is applied to the belt 2 and the reinforcing layer 3 is arranged, showed good results in all items.

On the other hand, even in the case of a tie in which twisted cords such as 1 × 2 and 1 × 3 are applied to the belt cord layer, a cord fatigue resistance and belt resistance can be obtained by adding a reinforcing layer (tire Nos. 17 and 18). Although endurance performance such as end separation can be improved, rolling resistance has not been improved.

Also, if you make the cord spacing thin like Tire No. 22,
Since the belt end strain increases, the belt end separation resistance is inferior, and the cord fatigue resistance also decreases, it is difficult to achieve both durability and motion characteristics.

(Effects of the Invention) The pneumatic radial tire according to the present invention can achieve both high kinetic characteristics and belt durability at a high level. Further, since the single wire cord can be applied to the belt cord layer, the cord twisted wire manufacturing process is not required, and the cord can be provided at a lower cost than conventional tires.

[Brief description of the drawings]

FIG. 1 is a sectional view of a pneumatic radial tire according to the present invention, and FIGS. 2 to 5 are sectional views showing other structures. 1 ... Carcass, 2 ... Belt 2a ... Inner cord layer, 2b ... Outer cord layer 3 ... Reinforcing layer, 4 ... Tread rubber 5 ... Bead core

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-57-26002 (JP, A) JP-A-62-289404 (JP, A) JP-A-61-157404 (JP, A) JP-A-58- 73406 (JP, A) JP 60-60003 (JP, A) JP 61-135803 (JP, A) JP 55-160605 (JP, A) JP 53-119502 (JP, A) JP-A-55-91406 (JP, A) JP-A-58-76308 (JP, A) JP-A-59-8503 (JP, A) JP-B-62-14402 (JP, B2) JP-B-55-45402 (JP, B2) JP-B-58-45366 (JP, B2)

Claims (2)

(57) [Claims] 1. A radial carcass that reinforces a pair of sidewall portions and a tread portion across bead cores embedded in a pair of bead portions, and a two-layer metal single wire cord layer that reinforces the tread portion at the outer periphery of the carcass. A pneumatic radial tire having a belt, wherein the single-cord cords in each layer of the belt are arranged in parallel to each other in the layer and are arranged in an inclined arrangement at an angle of 15 to 30 ° with respect to the tire equatorial plane. Consists of single-wire cords with a diameter within the range of 0.28 to 0.70 mm arranged in the range of 30 to 120 per 50 mm, and the inner cord layer near the carcass has the maximum width of the belt. Along the outer periphery of this belt, an organic fiber cord extending at least from the middle position between the center of the ground contact width of the tread portion and the ground contact end toward the ground contact end and beyond the maximum width cord layer end of the belt. A reinforcing layer is arranged, and the reinforcing layer is formed by spirally winding around the belt with the number of driven cords of 40 to 70 per 50 mm, and each of the reinforcing layers in the region exceeding the maximum width cord layer end. The distance (t) between the surface smoothly contacting the cord on the inner side and the surface smoothly contacting the cord on the outer side in the maximum width code layer in the region is determined by the distance (t) of the maximum width code layer near the end of the outer code layer. A pneumatic radial tire having a distance (g) longer than a distance (g) between a surface that smoothly contacts each cord on the outside and a surface that smoothly contacts each cord on the inside of the outer cord layer. 2. A radial carcass that reinforces the pair of sidewall portions and the tread portion across the bead cores embedded in the pair of bead portions, and at least 2 that reinforces the tread portion between the outer periphery of the carcass and the tread rubber. And a belt of a metal single-wire cord layer, the single-wire cords of the layers being arranged in parallel with each other in the layer and arranged in a tilted manner at a cord angle of 15 to 30 ° with respect to the tire equatorial plane. In the pneumatic radial tire, each layer of the belt is formed by arranging single wire cords having a diameter within a range of 0.28 to 0.70 mm with a driving number within a range of 30 to 120 per 50 mm, and an inner side of the carcass. The cord layer has the maximum width of the belt, and the maximum width of the belt cord layer along the outer circumference of the belt from at least the center between the center of the ground width of the tread and the ground end toward the ground end. A reinforcing rubber layer extending to a position beyond the end is arranged, and the rubber of the reinforcing rubber layer has a thickness of 2
Within the range of ~ 5mm and 25% modulus is 20 ~ 70kg /
Pneumatic radial tires characterized by being in the cm ² range.