JP2009166617A - Radial tire for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radial tire for a vehicle increased in high-speed durability and riding comfort by reducing a ply steer and rolling resistance. <P>SOLUTION: In this radial tire 1 for a vehicle, two belt layers 6, 7 formed by tilting belt cords 6a, 7a in the reverse directions to the tire circumferential direction are formed on a tread part 5 on the outside of a carcass layer 4. The tilt angles θ<SB>1</SB>, θ<SB>2</SB>of the belt cords 6a, 7a of both belt layers 6, 7 to the tire circumferential direction are set to 45-65°, respectively. An organic fiber cord 8a is spirally wrapped around both belt layers 6, 7 in the tire circumferential direction to form a reinforcement layer 8. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle radial tire.

  Recent automobiles tend to be equipped with radial tires excellent in handling stability and durability at high speeds. In this radial tire, two belt layers in which belt cords are inclined in opposite directions with respect to the tire circumferential direction are laminated, and this is disposed outside the carcass layer of the tread portion (see Patent Document 1). . The laminated belt layer has rigidity in the circumferential direction and the width direction, and the carcass layer is tightened by the effect to maintain the tire shape.

  Since the radial tire rolls while being deformed in contact with the ground, a difference occurs in the tensile force acting in the width direction of the belt layer, and the tire twists due to lateral force (hereinafter referred to as price tear). For this reason, the rolling resistance increases and the handle flow easily occurs. By the way, it is known that when the inclination angle of the belt cord with respect to the tire circumferential direction is set to a singular angle (54.7 degrees), a difference in tensile force with respect to the width direction of the belt layer does not occur and the occurrence of price tear can be prevented. However, if the inclination angle of the belt cord is a singular angle, the rigidity of the belt layer in the circumferential direction is lost, and the belt cord does not function as a tire.

Therefore, a structure has been proposed in which an organic fiber belt in which the inclination angle of the belt cord is set to a singular angle is provided and another steel belt is wrapped with the organic fiber belt (see Patent Document 2). That is, the loss in the circumferential rigidity of the organic fiber belt is compensated by the steel belt.
Alternatively, a structure in which a reinforcing layer is formed by folding an organic fiber strip in a zigzag, and this reinforcing layer is covered with a steel belt layer in which the inclination angle of the belt cord is set to a singular angle has been proposed (Patent Document). 3).
JP 9-142104 A (paragraphs [0011 to 0012], FIG. 2) Japanese Patent Laid-Open No. 10-109502 (paragraphs [0012 to 0014], FIGS. 2 and 3) Japanese Patent Laid-Open No. 11-32225 (paragraphs [0012 to 0013], FIGS. 2 and 4)

However, according to the structure of Patent Document 2, since the steel belt is wrapped with an organic fiber belt to form a three-layer belt, the overall thickness is increased, and the tire is liable to be twisted. It does not help so much. Further, since the rigidity in the circumferential direction of the entire belt is secured by the steel belt, the rigidity becomes too high, and there is a problem in the riding comfort characteristics.
On the other hand, according to the structure of Patent Document 3, since the reinforcing layer is formed by folding the organic fiber band material in a zigzag manner, the number of processing steps increases and there is a problem in cost. In addition, since the number of steel belt layers in which the inclination angle of the belt cord is set to a singular angle is one, the rigidity of the entire tire becomes weaker than usual.
Furthermore, in the tires of Patent Documents 1 and 2, the belt layer spreads radially outward due to the centrifugal force during high-speed rotation, and a large distortion is generated. Therefore, the belt layer is easily peeled from both ends, and there is a problem in high-speed durability. Not only will the rolling resistance increase.

  In view of such circumstances, an object of the present invention is to provide a radial tire for a vehicle in which price tear and rolling resistance are reduced, and high-speed durability and riding comfort characteristics are improved.

  The present invention for solving the above-described problems provides a radial tire for a vehicle, in which two belt layers, each having a belt cord inclined in opposite directions with respect to the tire circumferential direction, are provided outside the carcass layer of the tread portion. An inclination angle of the belt cord in the belt layer with respect to the tire circumferential direction is set to 45 to 65 degrees, and an organic fiber cord is spirally wound in the tire circumferential direction around the belt layers to form a reinforcing layer. .

  If the inclination angle of the belt cord with respect to the tire circumferential direction is set to 45 to 65 degrees, the rigidity in the circumferential direction of the belt layer is greatly reduced, so there is almost no difference in tensile force with respect to the width direction of the belt layer. Tire twisting hardly occurs. Further, in order to greatly reduce the circumferential rigidity of the belt layer, an organic fiber cord is spirally wound around the belt layer in the tire circumferential direction to form a reinforcing layer. This is dealt with by compensating for the decrease in directional rigidity.

  The organic fiber cord is preferably made of an aromatic polyamide fiber, a polyarylate fiber, or a polyparaphenylene benzbisoxazole fiber.

  When this type of organic fiber cord is spirally wound around the belt layer in the tire circumferential direction, a lightweight and high-strength reinforcing layer is formed.

According to the present invention, the difference in tensile force with respect to the width direction of the belt layer hardly occurs, so that price tear due to tire twist hardly occurs, rolling resistance is reduced, and straight running performance is improved.
Further, since the reinforcing layer is formed by spirally winding the organic fiber cord in the tire circumferential direction on the belt layer, the belt layer can be prevented from spreading radially outward due to centrifugal force during high-speed rotation. No distortion occurs. For this reason, peeling of a belt layer becomes difficult to occur and high-speed durability is greatly improved.
In addition, since the decrease in the circumferential rigidity of the belt layer is compensated by the reinforcing layer made of organic fibers, the tire rigidity can be maintained at an appropriate level, and the riding comfort characteristics can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1 is a schematic diagram showing a cross-sectional structure of a radial tire for a vehicle according to the present invention, FIG. 2 is a development view of a belt layer and a reinforcing layer in the radial tire, FIG. 3 is a cross-sectional view taken along line AA in FIG. It is a graph which shows the relationship between the belt cord inclination-angle in a laminated belt, and Young's modulus.

  The vehicular radial tire 1 according to the present embodiment includes a tread portion 5 that is in contact with the ground, a bead portion 11 that is fitted to the rim R, and a sidewall portion 9 that connects the tread portion 5 and the bead portion 11. An air chamber 10 having a substantially crown-shaped cross section is formed inside the tire body. The bead core 11 and the bead filler 3 are built in the bead unit 11. The radial tire 1 includes a carcass layer 4 in which both ends are folded and connected by a pair of bead cores 2 and bead fillers 3, two belt layers 6 and 7 disposed outside the carcass layer 4 of the tread portion 5, and these belt layers. 6 and 7 are laminated with organic fiber reinforcing layers 8 disposed outside.

  The carcass layer 4 is a rubberized cord layer that forms a skeleton as a tire, and carcass cords 4a made of organic fibers such as nylon, polyester, and aromatic polyamide are arranged in a radial direction orthogonal to the tire circumferential direction (see FIG. 2).

  The belt layers 6 and 7 are rubberized cord layers having non-stretchable cords, and the carcass layer 4 is tightened by the effect to keep the tire shape. The belt layers 6 and 7 are formed in a belt shape by bias-cutting a rubberized cord to form a band material and connecting both ends thereof. For this reason, belt cords 6a and 7a inclined with respect to the width direction of the belt layers 6 and 7 are embedded in the rubber layers 6b and 7b at a predetermined pitch (see FIG. 3). For the belt cords 6a and 7a, for example, a stranded wire of steel or organic fiber (such as aromatic polyamide) is used.

As shown in FIG. 2, the belt layers 6 and 7 are laminated such that the belt cords 6a and 7a are inclined in opposite directions with respect to the tire circumferential direction. Further, the inclination angles θ ₁ and θ ₂ of the belt cords 6a and 7a with respect to the tire circumferential direction are made equal, and the values thereof are set to 45 to 65 degrees. The inclination angles θ ₁ and θ ₂ of the belt cords 6a and 7a with respect to the tire circumferential direction are preferably closer to a singular angle of 54.7 degrees. By the way, since the belt layers 6 and 7 are formed by bias-cutting rubberized cords at the same angle, the belt cords 6a and 7a are aligned with respect to the tire circumferential direction by laminating both ends in the width direction in parallel. _They are arranged symmetrically and the inclination angles θ ₁ and θ ₂ are equal. The inner belt layer 6 is formed wider than the outer belt layer 7.

  As shown in FIG. 3, the reinforcing layer 8 is formed by winding an organic fiber cord 8a around the belt layers 6 and 7 in a spiral shape in the tire circumferential direction. When winding the organic fiber cord 8a, it is preferable that the organic fiber cords 8a are densely arranged and wound in a single layer, but may be wound in multiple layers depending on the characteristics of the tire. The organic fiber cord 8a preferably uses a strand of organic fiber such as aromatic polyamide fiber, polyarylate fiber, polyparaphenylene benzbisoxazole fiber or the like. The reinforcing layer 8 is formed wider than the inner belt layer 6 so as to completely cover the belt layers 6 and 7 (see FIG. 1), so that the belt layers 6 and 7 are peeled from both ends during high-speed rotation. Is preventing.

By the way, as shown in FIG. 4, the Young's modulus Ex in the width direction of the laminated belt layers 6 and 7 is maximum when the inclination angle θ (θ ₁ = θ ₂ ) of the belt cords 6a and 7a is zero. As the inclination angle θ increases, it decreases rapidly and becomes zero at the singular angle θ ₀ (54.7 degrees). In other words, since the rigidity in the circumferential direction is lost at the singular angle θ ₀ , there is no difference in the tensile force in the width direction acting on the belt layers 6 and 7 due to the ground contact deformation of the tire, and the torsional deformation of the tire is suppressed, thereby reducing the price. Tare is greatly reduced. However, since the circumferential rigidity of the belt layers 6 and 7 is lost, the belt layers 6 and 7 cannot function as tires as they are. For this reason, in the past, the inclination angle θ of the belt cords 6a and 7a was set to 17 to 27 degrees (range A in FIG. 4) to ensure the rigidity in the circumferential direction. There was a problem with straight running and a straight running.

On the other hand, in the present embodiment, since the inclination angles θ ₁ and θ ₂ of the belt cords 6a and 7a are set to 45 to 65 degrees, the rigidity in the circumferential direction of the belt layers 6 and 7 is greatly reduced. For this reason, the difference of the tensile force with respect to the width direction of the belt layers 6 and 7 hardly arises, and the price tear by tire twist is reduced significantly. For this reason, the rolling resistance is reduced and the straight traveling performance is improved. However, since the circumferential rigidity of the belt layers 6 and 7 is significantly reduced and the tire does not function as it is, the reinforcing layer 8 is provided outside the belt layers 6 and 7 so that the circumferential rigidity of the belt layers 6 and 7 is increased. To compensate for the decline.

Further, since the reinforcing layer 8 is formed by spirally winding the organic fiber cords 8a around the belt layers 6 and 7 in the circumferential direction of the tire, outwardly in the radial direction of the belt layers 6 and 7 due to centrifugal force during high-speed rotation. The belt layers 6 and 7 are not distorted. For this reason, peeling of the belt layers 6 and 7 hardly occurs, and the high-speed durability is greatly improved.
In addition, since the organic fiber reinforcing layer 8 compensates for the decrease in the circumferential rigidity of the belt layers 6 and 7, the tire rigidity can be maintained at an appropriate level, and the riding comfort characteristics can be improved.

By the way, if the inclination angles θ ₁ and θ ₂ of the belt cords 6a and 7a are set to singular angles, the belt layers 6 and 7 are prevented from torsional deformation at the time of contact, the price tear is reduced, and the handle flow is suppressed. Although the running performance is the best, even if the inclination angles θ ₁ and θ ₂ are set to 45 degrees, which is about 10 degrees smaller than the singular angle, a dramatic improvement in the price tear was confirmed by experiments. The change in the price tear due to the inclination angles θ ₁ and θ ₂ of the belt cords 6a and 7a is considered to be symmetric with respect to the singular angle, so even if it is set to 65 degrees that is about 10 degrees larger than the singular angle, the price tear It should be possible to expect a dramatic reduction in

Next, the present invention will be specifically described with reference to examples and comparative examples.
(Example)
For the belt layers 6 and 7, two sets of steel cords were used as the belt cords 6a and 7a, and the inclination angles θ (θ ₁ = θ ₂ ) were set to 45 degrees and 55 degrees, respectively. Then, one tire was manufactured using these two sets of belt layers 6 and 7 respectively. In any of the tires, an aromatic polyamide fiber strand was used as the organic fiber cord 8a of the reinforcing layer 8. In Table 1, the belt cords 6a and 7a having the inclination angle θ of 45 degrees are shown as Example 1, and those having the inclination angle θ of 55 degrees are shown as Example 2. The tire 1 size is 195 / 65R15, the rim size is 15 × 6 J, and the air pressure is 220 kPa.

(Comparative example)
For the belt layers 6 and 7, two sets of steel cords were used as the belt cords 6a and 7a and the inclination angle θ (θ ₁ = θ ₂ ) was set to 27 degrees. As the organic fiber cord 8a of the reinforcing layer 8, a stranded wire of nylon and an aromatic polyamide fiber was used. And one tire each provided with the reinforcement layer 8 which consists of these organic fibers was manufactured. In Table 1, a case where the organic fiber cord 8a is nylon is shown as Comparative Example 1, and a case where the organic fiber cord 8a is an aromatic polyamide fiber is shown as Comparative Example 2. The tire size, rim size, and air pressure are the same as in the example.

(Test conditions)
High-speed test: The test was performed according to ISO-10191. Originally, the air pressure should be 280 kPa, but this time to confirm the durability of the belt layers 6 and 7, the test was conducted under low air pressure conditions (150 kPa) until the tire was damaged. The distance was measured. A result is shown by the index | index which makes the tire of the comparative example 1 100, and it shows that it is excellent in high speed, so that an index | exponent is large.
Durability test: The vehicle was run under conditions of a speed of 80 km / h, a load of 8 kN, and an air pressure of 150 kPa, and the distance to the place where the tire was damaged was measured. A result is shown by the index | index which sets the tire of the comparative example 1 to 100, and it shows that it is excellent in durability, so that an index | exponent is large.
Cornering force: A cornering force was measured using a tire testing machine under conditions of an air pressure of 210 kPa and a load of 450 kg. A result is shown by the index | index which makes the tire of the comparative example 1 100, and it shows that the cornering force is excellent, so that a numerical value is large.

Rolling resistance: Evaluation was carried out using an indoor drum type tire rolling tester. A result is shown by the index | index which makes the tire of the comparative example 1 100, and it shows that there are few rolling resistance, so that an index | exponent is low.
Price tear: Based on JASOC607, the price tear was measured on a uniformity measurement tester. A result is shown by the index | index which makes the tire of the comparative example 1 100, and it shows that a price tear is so low that an index | exponent is small.
Ride comfort characteristics: Test tires were mounted on 1.8 liter class cars, and the feelings by the test driver were quantified. It shows with the parameter | index which sets the tire of the comparative example 1 to 100, and shows that riding comfort characteristics are excellent, so that a numerical value is large.

As can be seen from Table 1, when aromatic polyamide fibers were used as the organic fiber cord 8a instead of nylon fibers (comparing Comparative Examples 1 and 2), good results were obtained except for ride comfort characteristics. In particular, the results of the durability test were dramatically improved. This is because the aromatic polyamide fiber has higher strength than the nylon fiber, and the deformation of the belt layers 6 and 7 is suppressed by improving the strength of the reinforcing layer 8. In addition, some reduction in price tear was observed. This is because the ground deformation (dent) of the tire is suppressed due to the improvement of the strength of the reinforcing layer 8, and the twist of the tire is reduced. In addition, since the reinforcing layer 8 increases the rigidity of the tire itself, the riding comfort characteristics are slightly deteriorated.
For the high speed test, durability test and cornering force, better results than Comparative Example 1 were obtained even when the inclination angle θ of the belt cords 6a and 7a was changed (see Examples 1 and 2).

It was confirmed that the price tear was reduced when the inclination angle θ (θ ₁ = θ ₂ ) of the belt cords 6a and 7a was set to 55 degrees near the singular angle (Example 1). The price tear increases as the inclination angle θ of the belt cords 6a and 7a decreases. However, even when the inclination angle θ of the belt cords 6a and 7a is 45 degrees (compared to the first comparative example), the price tear is dramatically increased. Therefore, as described above, the lower limit of the inclination angle θ is set to 45 degrees.
It can also be seen that the rolling resistance decreases as the inclination angle θ of the belt cords 6a and 7a approaches the singular angle (see Comparative Example 1 and Examples 1 and 2). This is because as the inclination angle θ of the belt cords 6a and 7a approaches the singular angle, the torsional deformation at the time of contact of the belt layers 6 and 7 becomes smaller and the torsion of the tire becomes smaller.
It can be seen that the riding comfort characteristics also improve as the inclination angle θ of the belt cords 6a and 7a approaches the singular angle (see Comparative Example 1 and Examples 1 and 2). This is because as the inclination angle θ of the belt cords 6a and 7a approaches the singular angle, the torsional deformation at the time of contact of the belt layers 6 and 7 decreases, and the tire rigidity can be maintained at an appropriate level.

It is a mimetic diagram showing the section structure of the radial tire for vehicles of the present invention. FIG. 3 is a development view of a belt layer and a reinforcing layer in the radial tire. It is the sectional view on the AA line of FIG. It is a graph which shows the relationship between the belt cord inclination-angle in a laminated belt, and Young's modulus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radial tire for vehicles 2 Bead core 3 Bead filler 4 Carcass layer 5 Tread part 6 Belt layer 6a Belt cord 7 Belt layer 7a Belt cord 8 Reinforcement layer 8a Organic fiber cord θ ₁ Inclination angle of belt cord 6a θ ₂ Inclination angle of belt cord 7a θ ₀ singular angle

Claims (2)

  In a radial tire for a vehicle having two belt layers inclined in opposite directions with respect to the tire circumferential direction on the outer side of the carcass layer of the tread portion, the inclination of the belt cords in the tire circumferential direction in both belt layers A radial tire for a vehicle, wherein an angle is set to 45 to 65 degrees and an organic fiber cord is spirally wound around the belt layer in the tire circumferential direction to form a reinforcing layer.   2. The vehicle radial tire according to claim 1, wherein the organic fiber cord is made of an aromatic polyamide fiber, a polyarylate fiber, or a polyparaphenylene benzbisoxazole fiber.

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