JP2008100552A - Tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance steering stability while ensuring good durability. <P>SOLUTION: In a belt layer 7 of a cross ply structure, a steel cord 10 in which a plurality of ultra-fine filaments f having a wire diameter d of 0.06-0.10 mm are twisted is used as a belt cord. Ply strength K, i.e., a product T×n of tensile strength T (unit: N) per one steel cord 10 and the hitting number (unit: number/5 cm) of the belt cord per 5 cm width of the belt plies 7A, 7B is made to 6,125-10,192 (unit: N*number/5 cm). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motorcycle tire that can improve steering stability while ensuring excellent durability by using a steel cord in which ultrafine filaments are twisted on a belt cord.

  As a belt layer of a radial tire, two belt plies in which steel cords (belt cords) are inclined at an angle of 10 to 45 ° with respect to the tire circumferential direction are arranged so that the steel cords cross each other. A cross-ply structure in which the direction of inclination is placed on top of each other is widely used for four-wheeled vehicle tires in terms of handling stability, durability, cost, and the like.

  However, in a motorcycle tire, the tread surface is formed with a convex arc-shaped profile having a very small radius of curvature compared to a four-wheel vehicle tire due to the characteristic that the vehicle body turns with a large inclination. For this reason, a cross-ply structure using an organic fiber cord such as nylon, polyester, or aramid is generally employed for the belt layer of a motorcycle tire instead of a steel cord (see, for example, Patent Document 1).

  The reason is as follows. That is, in a motorcycle tire, since the radius of curvature of the tread surface is small, the belt cord is greatly distorted during traveling. Therefore, when steel cords commonly used for belt cords for passenger car tires are used for belt cords for motorcycle tires, steering stability is better than that of cross-ply belt layers using organic fiber cords. This is because the strength drop due to compression fatigue of the cord due to running increases, but durability sufficient for practical use cannot be secured.

  It should be noted that when a steel cord is produced, the strength per cross-sectional area increases as the wire diameter (diameter) of the wire is reduced in the wire drawing process, but it gradually becomes brittle and tends to break. Therefore, steel filaments having a wire diameter of 1.6 mm or more are conventionally used for tire belt cords.

Japanese Patent Laid-Open No. 04-365602

  Therefore, the present invention uses a very thin filament with a wire diameter d of 0.10 mm or less for the belt cord, and specifies the ply strength of the belt ply, while ensuring excellent durability and driving stability. The object is to provide a motorcycle tire that can be improved.

In order to achieve the above object, the present invention of claim 1 is directed to a tread in which a tread surface of a tread portion is curved in a convex arc shape from a tire equator to a tread edge and is a tire axial distance between the tread edges. The width is the maximum width of the tire, and the carcass extends from the tread part to the bead core of the bead part through the sidewall part, and a belt layer arranged radially outside the carcass and inward of the tread part. A tire for a motorcycle,
The belt layer comprises a belt ply in which belt cords are arranged at an angle of 10 to 45 ° with respect to the tire circumferential direction,
In addition, a steel cord obtained by twisting a plurality of ultrafine filaments having a wire diameter d of 0.06 to 0.10 mm is used for the belt cord, and a tensile strength T (unit: N) per one of the steel cords The ply strength K, which is the product T × n of the number n of belt cords driven per 5 cm width of the belt ply (unit: 5/5 cm), is 6125 to 10192 (unit: N · line / 5 cm). Features and

In the invention of claim 2, the steel cord is characterized in that the number of ultrafine filaments is in the range of 6-12.
According to a third aspect of the present invention, the steel cord has a bending rigidity M per cord of 1.2 (unit: g · cm) or less.

  As described above, since the steel cord is used for the belt cord in the present invention, the steering stability can be improved as compared with the case where the organic fiber cord is used. In addition, since the filament diameter used for steel cords is as fine as 0.10 mm or less, strength reduction against repeated compression fatigue can be suppressed, and durability can be increased to the same level or higher than when organic fiber cords are used. It becomes possible.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a motorcycle tire 1 of the present embodiment includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, a radially outer side of the carcass 6, and a tread. A belt layer 7 disposed inside the portion 2.

  The tread surface 2S which is the surface of the tread portion 2 is smoothly curved in a convex arc shape from the tire equator C to the tread edge Te, and a tread width which is a tire axial distance between the tread edges Te and Te. TW makes the maximum tire width. Thereby, the tread surface 2S is formed over a wide range, and the vehicle body can be turned with a large inclination.

  The carcass 6 is formed by one or more, in this example, two carcass plies 6A and 6B in which carcass cords are arranged at an angle of 75 to 90 ° with respect to the tire circumferential direction. As the carcass cord, an organic fiber fiber cord, in particular, a highly elastic cord such as nylon, rayon, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), or aramid is employed. Each of the carcass plies 6A and 6B has a ply folded portion 6b that is locked by folding the bead core 5 from the inner side to the outer side in the tire axial direction at both ends of the ply body portion 6a straddling the bead cores 5 and 5 in a toroidal shape. In a series. A bead apex rubber 8 is provided between the ply body portion 6a and the ply turn-up portion 6b. The bead apex rubber 8 extends from the bead core 5 outward in the tire radial direction. Accordingly, the bead portion 4 reaches the sidewall portion 3 and is reinforced.

  The belt layer 7 includes at least one belt ply 7A and 7B in which the belt cord 7c is arranged at an angle of, for example, 10 to 45 ° with respect to the tire circumferential direction, and in this example, the tread surface 2S and the tread surface 2S. Extending on the carcass 6 with substantially the same profile. The belt plies 7A and 7B are overlapped with each other so that the belt cords 7c intersect with each other so that the belt cords 7c intersect each other, and the tread portion 2 is strongly reinforced with a tagging effect. The belt ply 7A on the inner side in the tire radial direction is wider than the belt ply 7B on the outer side, and the positional deviation L at the outer end is set to 5 to 20 mm, thereby ensuring the belt rigidity to the end. In addition, the stress concentration at the end portion is relaxed to suppress peeling damage. In the belt layer 7, the angle of the belt cord is preferably in the range of 15 to 26 ° in order to ensure proper tire profile, dimension growth resistance, and high-speed durability.

  In the present invention, as the belt ply, as shown in FIG. 2, an ultrafine steel cord 10 in which a plurality of ultrafine filaments f having a wire diameter d of 0.06 to 0.10 mm are twisted together is used. . In the figure, a 3 × 3 twisted structure in which three strands S obtained by twisting three ultrafine filaments f are further twisted is illustrated, but this strand structure is regulated. For example, various twist structures such as 1 × 3 and 2 × 3 can be appropriately employed.

  What is important in the steel cord 10 is that an ultrafine filament f having a wire diameter d of 0.06 to 0.10 mm is used as the filament, and the tensile strength T (unit: N) per piece of the steel cord 10 is used. ) And a ply strength K that is a product T × n of the number n (unit: book / 5 cm) of the belt cord 7c driven per 5 cm width of the belt ply in a range of 6125 to 10192 (unit: N · piece / 5 cm). It is to regulate.

  The steel cord 10 using such an ultrafine filament f exhibits a high tensile elastic modulus while maintaining a flexibility close to that of an organic fiber cord. Therefore, the tread portion 2 of the motorcycle tire can be suitably reinforced, and the steering stability in straight travel and turning can be improved without impairing riding comfort. In addition, since the filament wire diameter d is as small as 0.1 mm or less, the stress generated in bending deformation can be reduced and the compression fatigue resistance can be enhanced, and the durability is equivalent to the case of using an organic fiber cord or It becomes possible to raise more than that.

  Here, when the steel cord is produced, the strength per cross-sectional area increases as the wire diameter (diameter) of the wire is reduced in the wire drawing process. However, on the other hand, the wire gradually becomes brittle and tends to break. Therefore, in the ultrafine filament f used in the present application, the deterioration of the bankruptcy resistance is suppressed by sufficiently slowing the wire drawing speed in the wire drawing process.

  If the wire diameter d is less than 0.06 mm, it becomes difficult to sufficiently suppress the bankruptcy resistance, and the wire drawing efficiency is excessively deteriorated. On the other hand, if the wire diameter d exceeds 0.10 mm, the compression fatigue resistance becomes insufficient, leading to a result that the durability is impaired as compared with the case where an organic fiber cord is used. Even if the ply strength K is less than 6125 (unit: N · lines / 5 cm), the ply strength is insufficient and the durability of the cord cannot be ensured. On the other hand, if the ply strength K exceeds 10192 (unit: N / pieces / 5cm), the belt stiffness becomes excessive, the cornering power increases too much, and the high-speed stability tends to deteriorate, such as causing vibration and vibration to the vehicle body. Invite. From such a viewpoint, in the wire diameter d, it is more preferable that the lower limit value is 0.07 mm or more and the upper limit value is 0.09 mm or less. In the ply strength K, the lower limit value is more preferably 6475 (unit: N · line / 5 cm) or more and the upper limit value is 9065 (unit: N · line / 5 cm) or less.

At this time, the number of the ultrafine filaments f per one steel cord 10 is preferably in the range of 6 to 12. If the number is less than 6, it becomes difficult to optimize the ply strength K. Conversely, if the number exceeds 12, the tire performance cannot be improved enough to meet the cost increase, and an unnecessary weight increase is caused. The disadvantage arises.

  In addition, the bending rigidity M per one of the steel cords 10 is 1.2 (unit: g · m) from the viewpoints of suppressing high speed stability by suppressing the occurrence of vibration, vibration, and the like during driving, and improving ride comfort. It is also preferable to regulate to below cm).

  The “bending rigidity M” of the steel cord is obtained by fusing a steel cord with a length of 70 mm so as to prevent untwisting of the steel cord to obtain a test piece. For example, a stiffness tester (Model 150- D) etc. are measured. Specifically, as schematically shown in FIG. 3, while fixing one end of the test piece A, a force F is applied to the other end A1 of the test piece A extending 50 mm from the fixed end, It is obtained by measuring the drag (bending hardness) when the opening angle at the other end A1 of the test piece A is 15 °.

  The tensile strength T of the steel cord was measured at a tensile speed of 5 cm / min in accordance with the tensile test of the cutting load and the total elongation at the time of cutting (section 6.4) according to “steel tire cord test method” of JIS G3510. This is the maximum load required for the specimen to cut.

In this example, on the outside of the belt layer 7 in the radial direction, for the purpose of enhancing high-speed durability,
A band layer 9 in which a band cord is spirally wound at an angle of 5 degrees or less with respect to the circumferential direction is disposed. As the band layer 9, a pair of left and right edge band plies that covers only the outer end portion in the tire axial direction of the belt layer 7 and a full band ply that covers substantially the entire width of the belt layer 7 can be used as appropriate. An example of one full band ply is shown. As the band cord, in order to further improve the handling stability,
High elastic cords such as aramid fiber cords and steel cords can be suitably used. In particular, when the steel cord is used, the above-described steel cord 10 can be suitably used.

  Further, in order to further improve the handling stability, a rubber having a glass transition temperature (Tg) of −20 ° C. to 0 ° C., which is higher than the conventional rubber, is preferably used as the tread rubber 2G disposed on the tread portion 2 and forming the tread surface 2S. it can.

  Although the particularly preferred embodiment of the present invention has been described in detail above, the motorcycle tire of the present invention has the belt layer 7 formed of two belt plies 7A and 7B and the band layer 9 disposed as in this example. In addition to the embodiment described above, the belt layer 7 is formed of two belt plies 7A and 7B and the band layer 9 is omitted, or the belt layer 7 is formed of one belt ply 7A and the band layer 9 is disposed. The present invention can be carried out by being modified into various aspects, such as adopting an aspect.

  A motorcycle tire (195 / 50ZR17) having the tire structure shown in FIG. 1 and having a belt cord having the specifications shown in Table 1 was prototyped, and the durability and handling stability of each sample tire were tested and compared. Specifications other than those in Table 1 are the same.

(1) Durability;
Using a drum tester, the test tire is a rim (MT 6.0), internal pressure (290 kPa), load (1.77 kN), room temperature 25 ± 5 ° C., camber angle 0 °, speed 115 km. A high-speed durability test was conducted by a step-up speed method in which the speed was increased by 10 km / h every 10 minutes. A tire having a damage speed of 350 km / h or more when the tread portion was damaged was evaluated as “◯”, and a tire having a damage speed of less than 350 km / h was evaluated as “x”.

(2) Steering stability;
A sample tire was mounted on the rear wheel of a large motorcycle (1000 cc) under conditions of a rim (MT 6.0) and an internal pressure (290 kPa), and ran on a tire test course on a dry asphalt road surface. At that time, steering stability with respect to steering wheel response, rigidity, grip, and the like was evaluated by a five-point method using Comparative Example 1 as three points by sensory evaluation of the driver. The higher the score, the better.

  As shown in Table 1, it can be confirmed that the tires of the examples can improve steering stability while ensuring excellent durability.

1 is a cross-sectional view showing an example of a motorcycle tire according to the present invention. It is sectional drawing which shows one Example of a steel cord. It is drawing explaining the measuring method of the bending rigidity of a steel cord.

Explanation of symbols

2 Tread portion 2S Tread surface 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 7 Belt layer 7A, 7B Belt ply 10 Steel cord f Extra fine filament C Tire equator Te Tread edge

Claims (3)

The tread surface of the tread portion is curved in a convex arc shape from the tire equator to the tread edge, and the tread width which is the tire axial distance between the tread edges forms the maximum tire width, and the tread portion extends from the sidewall portion. A tire for a motorcycle comprising a carcass leading to a bead core of the bead portion and a belt layer disposed radially outward of the carcass and inward of the tread portion,
The belt layer comprises a belt ply in which belt cords are arranged at an angle of 10 to 45 ° with respect to the tire circumferential direction,
In addition, a steel cord obtained by twisting a plurality of ultrafine filaments having a wire diameter d of 0.06 to 0.10 mm is used for the belt cord, and a tensile strength T (unit: N) per one of the steel cords The ply strength K, which is the product T × n of the number n of belt cords driven per 5 cm width of the belt ply (unit: 5/5 cm), is 6125 to 10192 (unit: N · line / 5 cm). A tire for motorcycles.   The motorcycle tire according to claim 1, wherein the steel cord has a number of ultrafine filaments in a range of 6 to 12.   The motorcycle tire according to claim 1 or 2, wherein the steel cord has a bending rigidity M per cord of 1.2 (unit: g · cm) or less.

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