JP2011031843A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new pneumatic tire allowing reduction of weight without impairing breaking strength of the tire. <P>SOLUTION: In this pneumatic tire, a carcass layer 5 consists of at least one sheet of carcass ply 5a buried with a cord 5a<SB>1</SB>substantially orthogonal to the equator S of the tire. A belt layer 6 consists of a first belt 7 arranged with a first cord 7a inclined at an angle with the equator S of the tire within the range of 15 to 75° and a second belt 8 arranged outside the first belt 7 and buried with a second cord 8a extending in substantially parallel with the equator S of the tire. The first belt 7 has smaller tension strength than that of the second belt 8. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lightweight and durable pneumatic tire suitable for mounting on a general vehicle such as a passenger car.

  In recent years, efforts to address environmental issues such as global warming have been emphasized. Under such movement, tires are actively developing products with less environmental impact. One means for addressing this environmental problem is to reduce the weight of the tire by reducing the amount of material used for the tire as much as possible. As a means for that, it is effective to reduce the number of belts having a material with high density such as steel, and the prior art in this regard is to arrange a cord extending at a certain angle with respect to the equator of the tire. A pneumatic tire provided with a constructed first belt and a second belt constructed with a spiral cord disposed has been considered particularly useful. (For example, Patent Document 1).

JP-A-4-78602

  By the way, in order to further reduce the weight of pneumatic tires, for example, it is necessary to change the cord arranged on the belt to a lighter one or reduce the number of cords to be driven. Generally, the tensile strength of the belt Therefore, it is difficult to ensure the breaking strength of the tire, and there is no pneumatic tire that meets such a demand yet.

  An object of the present invention is to provide a novel pneumatic tire that can be reduced in weight without impairing the breaking strength of the tire.

The present invention extends to the toroidal shape from the tread portion to the bead portion through the sidewall portion, and a carcass layer having its end turned around from the bead core disposed in the bead portion to the outside, and the carcass layer In a pneumatic tire having a belt layer disposed on the outside,
The carcass layer is composed of at least one carcass ply in which a cord that is substantially orthogonal to the tire equator is disposed, and the belt layer is a first inclining an angle with respect to the tire equator in a range of 15 ° to 75 °. And a second belt disposed outside the first belt and extending a second cord extending substantially parallel to the equator of the tire, the first belt comprising: It has a tensile strength smaller than that of the second belt.

  In the tire configured as described above, it is preferable that the tensile strength of the second belt is 1.5 to 4 times the tensile strength of the first belt.

  The breaking strength of the tire is greatly influenced by the tension acting in parallel with the equator of the tire. Therefore, the breaking strength of the tire is maintained by the second belt having the second cord extending in parallel with the equator of the tire. By simplifying the first belt that hardly contributes (decreasing the cord strength of the first belt and reducing the number of cords driven), the weight of the tire can be reduced without impairing the breaking strength of the tire. .

  By making the tensile strength of the second belt 1.5 to 4 times that of the first belt, it is possible to satisfy the cornering power and dry performance of the tire and to reduce the weight sufficiently. It becomes possible to secure the breaking strength of the tire.

It is the figure which showed the tire meridian cross section about the half part of a tire about embodiment of the pneumatic tire according to this invention. FIG. 2 is a view taken along the line XX in FIG. 1, showing a structure inside the tire by partially breaking the tire. FIG. 2 is a graph showing the cornering power, tire mass, and dry performance shown in Table 1.

  Hereinafter, the present invention will be described more specifically with reference to the drawings.

  FIG. 1 is a diagram showing a tire meridian cross section of a tire half according to an embodiment of a pneumatic tire according to the present invention, and FIG. 2 is a view taken along the line XX of FIG. It is the figure which made it fracture and showed the structure inside a tire.

  In FIG. 1, 1 is a pair of bead portions connected in the circumferential direction of the tire, 2 is a pair of sidewall portions extending from the bead portions 1 toward the outer side in the radial direction of the tire, and 3 is these It is a tread portion that is connected across the extending end of the sidewall portion 2 and forms a toroidal shape.

  Reference numeral 4 denotes a pair of bead cores disposed in the bead portion 1, and the bead cores 4 extend in the circumferential direction of the tire to form a ring shape.

Reference numeral 5 denotes a carcass layer connected across the pair of bead cores 4, and the carcass layer 5 is wound around its respective bead cores 4 from the inner side toward the outer side. The carcass layer 5 is composed of at least one carcass ply, and is displayed as being composed of two carcass plies 5a and 5b in the illustration of FIG. In the carcass plies 5a and 5b, cords 5a ₁ and 5b ₁ are arranged substantially orthogonal to the equator S of the tire. Here, “substantially orthogonal” specifically means that the angle of the tire with respect to the equator S is in the range of 85 ° to 95 °, and takes into account manufacturing errors. Further, the cords 5a ₁ and 5b ₁ can be variously selected, and are employed from organic fibers such as aramid, polyethylene and nylon, glass fibers and steel, for example.

Reference numeral 6 denotes a belt layer disposed on the outer side in the radial direction of the tire with respect to the carcass layer 5.
The belt layer 6 includes a first belt 7 and a second belt 8 disposed on the outer side in the tire radial direction with respect to the first belt 7.

As shown in FIG. 2, the first belt 7 is provided with a first cord 7a that is inclined with respect to the equator S of the tire by an angle y. Here, in the present invention, the range of the angle y of the cord 7a is set to 15 ° to 75 ° because the first cord 7a and a second cord 8a described later are used when the angle of the tire with respect to the equator S is less than 15 °. This is because the pantograph effect necessary for securing the flexibility in the tire radial direction becomes difficult to obtain, and when the angle of the tire with respect to the equator S exceeds 75 °, the cord 7a and the cord This is because 5a ₁ and 5b ₁ approach parallel and it is difficult to obtain the pantograph effect.

  The first cord 7a can be selected from various materials such as organic fibers such as aramid, polyethylene, and nylon, glass fibers, and steel.

Tensile strength _{C 1} of the first belt 7, the code has a first cord 7a potent _{A 1} (unit: N) and, end counts _B 1 of the first code 7a implanted into the first belt 7 ( (Unit: book / mm).

C ₁ = A ₁ × B ₁ ... Formula 1

  The second belt 8 is provided with a second cord 8a that extends substantially parallel to the equator S of the tire. Here, “substantially parallel” specifically means that the angle is in the range of 0 ° to 5 ° with respect to the equator S of the tire, and takes into account manufacturing errors.

  The second cord 8a can be selected from various materials such as organic fibers such as aramid, polyethylene, and nylon, glass fibers, and steel. The second belt 8 may be configured by arranging a plurality of the second cords 8a in parallel with the equator plane S of the tire, or may be configured as a spiral cord wound in a spiral.

Strength _{C 2} pull of the second belt 8, the code has a second cord 8a potent _{A 2} (Unit: N) and, end counts _B 2 of the second code 8a implanted into the second belt 8 ( (Unit: book / mm).

C ₂ = A ₂ × B ₂ Formula 2

The present invention is intended to reduce the weight while securing the breaking strength of the tire. The second belt 8 secures the strength that can withstand the breaking strength of the tire, and is driven into the cord strength A ₁ of the first belt 7. In order to reduce the number B ₁ and reduce the weight, the tensile strength C ₁ of the first belt is made smaller than the tensile strength C ₂ of the second belt 8, but the first belt 7 is reduced in weight. And the rigidity with respect to the bending which the 1st belt 7 receives at the time of cornering also falls. In order to ensure the tire performance that is practically acceptable while obtaining the advantages of weight reduction, the tensile strength C ₂ of the second belt 8 is 1.5 to 4 times the tensile strength C ₁ of the first belt 7. It is preferable that

  The belt width of the first belt 7 is preferably about 5% wider than the belt width of the second belt 8 as shown in FIG.

  A tire of size 225 / 45R17 having the first belt and the second belt shown in Table 1 and having the structure as shown in FIG. 1 (the carcass layer uses two carcass plies, and the carcass ply cord is Both use polyethylene strands, the first belt uses steel cords with an angle y to the tire equator of 30 degrees, and the second belt is a steel spiral that extends approximately parallel to the tire equator. A cord was used.) And the tire mass, breaking strength, cornering power, and dry performance were investigated for each tire. The results are also shown in Table 1.

  The cord strengths of the first belt and the second belt in Table 1 were measured by a tensile test in a standard test chamber defined in JIS-L-0105 in accordance with JIS-L-1017.

  In addition, the number of cords driven in the first belt and the second belt was measured by cutting the tire perpendicularly to the direction in which the cords arranged on the respective belts extend, and measuring the number of cords per 50 mm. The number of cords was divided by 50 and converted to the number of cords per 1 mm.

  The tensile strength of the first belt and the second belt was converted into the tensile strength by multiplying the cord strength and the number of driving (Equation 1 and Equation 2). The tensile strength ratio is the ratio of the tensile strength of the second belt based on the tensile strength of the first belt.

  The mass of the tire is shown in Table 1 as an index in Table 1 with the conventionally used tire as the reference tire, and the mass of each tire is defined as 100. The smaller the number, the lighter.

  The breaking strength of a tire is determined by assembling each tire into a rim of 7.5 J × 17 stipulated by JATMA (THE Japan Automobile Tire Manufacturers Association, Inc.) and injecting water into the tire to apply pressure to the water. The pressure was increased until the tire was destroyed, and the comparison was made according to the pressure when the tire was destroyed. The reference tire is a tire satisfying the breaking strength, and the breaking strength of each tire is shown as an index in Table 1 with the breaking strength of the reference tire being 100. The larger the number, the higher the safety factor.

  The cornering stiffness is determined by assembling the tires on the rim, applying an internal pressure of 230 kPa, setting the speed to 80 km / h using a flat belt tester, and determining the difference in lateral force between the slip angle of 1 degree and 0 degrees. The cornering power was compared. Each cornering power is shown as an index in Table 1 with reference tire as 100. The larger the number, the higher the cornering power and the better the cornering rigidity, but it is desirable that it be 90 or more.

  Dry performance is achieved by assembling the tires on the rim, applying the internal pressure, mounting it on a Japanese FR car with a displacement of 2500cc, and driving a skilled test driver on the test course, changing the lane at a speed of 150km / h. The test results were evaluated using a limit running at 80 km / h and running including acceleration from 50 km / h, with a full score of 10 points. The larger the number, the higher the dry performance, but 6 or more are desirable.

  As a result, the tire (comparative tire 1) in which the tensile strengths of the first belt and the second belt are both smaller than the reference tire is smaller than the reference tire and does not satisfy the performance. The tire (comparative tire 2) in which the tensile strengths of the two belts are both increased with respect to the tire increases in mass compared to the reference tire and cannot satisfy the requirement for weight reduction. On the other hand, tires (compatible tires 1 to 6) in which the tensile strength of the second belt is equal to the tensile strength of the reference tire and the tensile strength of the first belt is smaller than the tensile strength of the second belt are those of the tire. It was confirmed that the fracture strength was satisfied and the weight could be reduced.

  As for the cornering power and the dry performance, as shown in Table 1 and FIG. 3, the value of the tire having a tensile strength ratio of 4.5 (conforming tire 5) is slightly lower, and the tire having a tensile strength ratio of 1.2 ( Although the weight reduction of the conforming tire 6) tends to be slightly smaller, if the tensile strength of the second belt is 1.5 to 4 times the tensile strength of the first belt, the cornering power and dry performance of the tire will be reduced. While improving, it became possible to aim at sufficient weight reduction and ensuring of the destruction strength of a tire, and it was confirmed that it is more preferable (conformity tires 1-4).

  According to the present invention, it is possible to stably supply a pneumatic tire that can be reduced in weight without impairing durability.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Bead core 5 Carcass layer 6 Belt layer 7 1st belt 7a 1st cord 8 2nd belt 8a 2nd cord S Tire equator

Claims (2)

A carcass layer that extends in a toroidal shape from the tread portion through the sidewall portion to the bead portion, and the end portion of the bead core that is disposed in the bead portion is rolled back from the inside to the outside, and is disposed outside the carcass layer. In a pneumatic tire with a belt layer,
The carcass layer is composed of at least one carcass ply in which a cord that is substantially orthogonal to the tire equator is disposed, and the belt layer is a first inclining an angle with respect to the tire equator in a range of 15 ° to 75 °. And a second belt disposed outside the first belt and extending a second cord extending substantially parallel to the equator of the tire, the first belt comprising: A pneumatic tire having a tensile strength smaller than that of the second belt.   The pneumatic tire according to claim 1, wherein the tensile strength of the second belt is 1.5 to 4 times the tensile strength of the first belt.

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