JP2007145125A - Radial tire for motorcycle, and band cord used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly demonstrate a rigid feeling and a light feeling in the steering stability while easily controlling elongation characteristics, and suppressing an increase in weight to be low. <P>SOLUTION: A radial tire comprises a core consisting of an aramid fiber cord part with aramid fibers twisted with each other and an outer layer consisting of one steel cord part with a plurality of steel strand twisted with each other and wounded around the core. The degree of elongation at 50 N load is set to be 0.5-0.7%, the degree of elongation at 100 N load is set to be 1.25-1.6%, and the degree of elongation at 300N load is set to be 2.0-2.6%, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radial tire for a motorcycle that is particularly suitable for a large vehicle and can be reduced in weight while ensuring excellent steering stability, and a band cord used therefor.

  A radial tire for a motorcycle has a structure in which a band layer is formed by spirally winding a band cord at an angle of 5 ° or less with respect to the tire circumferential direction on the radially outer side of the carcass forming the skeleton of the tire. Widely adopted.

  In recent years, it has been proposed to use a steel cord in which a plurality of steel strands are twisted instead of a conventionally used high modulus aramid fiber cord (see, for example, Patent Documents 1 and 2). ). This is because the aramid fiber cord has a high tensile elastic modulus and a strong restraining force on the tire, so it has excellent high-speed durability and high-speed straightness, but its compression rigidity is low, resulting in insufficient tread rigidity. This causes a problem that the vehicle has insufficient rigidity and poor steering stability. On the other hand, steel cord has high compression rigidity and bending rigidity, so when used in a band cord, tread rigidity can be secured sufficiently, and the steering stability can be improved, such as enhancing rigidity and traction at the time of banking. There is an advantage that it can.

Japanese Patent Laid-Open No. 04-362402 JP 2001-130218 A

  However, in the band cord, in order to cope with the vulcanization stretch of the tire in the vulcanization mold, it is necessary to increase the elongation at low load, for example, the elongation at 50N load is 0.5% or more. . Therefore, in the case of using a steel cord, it is necessary to provide means such as forming a wavy mold on the steel wire or making an open twist structure. However, it is difficult to control the elongation characteristics with any of the means, and what is to be molded has a problem that fretting wear tends to occur because the contact pressure between the strands locally increases at the molding part, and the fatigue resistance is impaired. There is also. In addition, the steel cord increases the tire weight, so that there is a problem that the lightness is lost in the handling stability.

  Therefore, the present invention is based on the use of a special composite cord in which aramid fibers and steel strands are combined as a band cord, and can enhance rigidity and traction at the time of banking and facilitate control of elongation characteristics. Another object of the present invention is to provide a radial tire for a motorcycle capable of maintaining a light feeling in driving stability while suppressing a weight increase, and a band cord used therefor.

The invention according to claim 1 of the present invention is a band cord of a radial tire for a motorcycle, wherein a core composed of an aramid fiber cord portion obtained by twisting aramid fibers and a plurality of steel strands are twisted together. It consists of a steel cord part and an outer layer wound around the core,
Moreover, the elongation at 50N load is 0.5 to 0.7%, the elongation at 100N load is 1.2 to 1.6%, and the elongation at 300N load is 2.0 to 2.6%. It is characterized by that.

In the invention of claim 2, the amide fiber cord portion has a bundle twist structure of 1100 to 1670 dtex, and the steel cord portion has a bundle twist structure of 2 to 9 steel strands.
According to a third aspect of the present invention, the steel cord portion has an elongation at a load of 50 N of 0.3% or less.
According to a fourth aspect of the present invention, there is provided a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, the carcass being disposed radially outward and inward of the tread portion, and the band cord extending in the tire circumferential direction A radial tire for a motorcycle having a band layer spirally wound at an angle of 5 ° or less, wherein the band cord includes a core composed of an aramid fiber cord portion obtained by twisting aramid fibers, It consists of one steel cord part twisted with steel strands and an outer layer wound around the core, and the elongation at 50N load is 0.5-0.7%, at 100N load The elongation is 1.2 to 1.6%, and the elongation at 300N load is 2.0 to 2.6%.

  As described above, in the present invention, the band cord is composed of a core made of an aramid fiber cord portion obtained by twisting aramid fibers and a single steel cord portion obtained by twisting a plurality of steel strands, and around the core. It is formed with a wound outer layer. Therefore, at the initial stage of the load, the steel cord portion that was wound around the aramid fiber cord portion was gradually stretched as the load increased, and the steel cord portion was wound around the steel cord portion. The aramid fiber cord part changes to the reverse form wound. And in this reverse form, it becomes difficult to stretch rapidly, and the elongation characteristics required for the band cord can be obtained easily and with high accuracy.

  In addition, since the weight increase can be kept low compared to steel cords, the lightness in handling stability can be maintained, and since the compression rigidity and bending rigidity are higher than aramid fiber cords, sufficient tread rigidity is ensured. It is possible to improve the steering stability by increasing the rigidity and traction at the bank.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a motorcycle radial tire according to the present invention.
In FIG. 1, a motorcycle radial tire 1 (hereinafter referred to as a tire 1) has a tread portion 2 in which a tread surface 2 </ b> S extends in a convex arc shape from a tire equator C to a tread end Te, and the tread end Te Since the tire axial distance between Te forms the maximum width of the tire, the vehicle can turn at a large bank angle. Further, the tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a band layer 7 disposed inside the tread portion 2 and radially outward of the carcass 6. And are arranged.

  The carcass 6 is formed by one or more, in this example, one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction. As the carcass cord, an organic fiber cord such as nylon, polyester, or rayon is preferably used. The carcass ply 6 </ b> A includes a series of ply folding portions 6 b that are folded from the inner side to the outer side in the tire axial direction around the bead core 5 at both ends of the ply main body portion 6 a that extends between the bead cores 5 and 5. Further, an apex rubber 8 for bead reinforcement extending in a radially outward direction from the bead core 5 is disposed between the ply main body portion 6a and the ply folded portion 6b. The radial height h1 of the apex rubber 8 from the bead base line BL is smaller than the radial height he of the tread end Te. Preferably, the lower limit is 35% or more of the height he. Is 40% or more, and the upper limit is 70% or less, further 60% or less.

  In this example, the case where the ply turn-up portion 6b has a high turn-up structure that terminates by being sandwiched between the ply main body portion 6a and the band layer 7 after passing through the sidewall portion 3 is illustrated. However, a structure in which the band layer 7 is terminated radially inward from the outer end of the band layer 7 may be used.

  The band layer 7 is formed of one or more band plies 7A, in this example, one band ply, in which a band cord is spirally wound at an angle of 5 ° or less with respect to the tire circumferential direction. This band ply 7A uses a narrow and long band-shaped ply in which a plurality of band cords arranged in parallel with each other are covered with a topping rubber as in the prior art, and the band ply is 5 ° or less with respect to the tire circumferential direction. It can be formed by winding spirally at an angle of.

  In the present invention, as the band cord 9, in the state before the band layer 7 is formed, that is, in the state before being spirally wound, as shown in FIGS. 2 (A) and 2 (B), aramid fibers A core 10 made of one aramid fiber cord portion 10A twisted together, and an outer layer 11 made of one steel cord portion 11A twisted of a plurality of steel strands 11f and wound around the core 10; A layer twist structure consisting of

  Here, as the aramid fiber cord portion 10A, one having a bundle twist structure in which a bundle of aramid fibers having a thickness of 1100 to 1670 dtex is twisted is used. As the steel cord portion 11A, one having a bundle twist structure in which a bundle of 2 to 9 steel strands 11f is twisted is used. As the steel strand 11f, one having a strand diameter in the range of 0.15 to 0.25 mm can be used.

  As shown in FIG. 3A, the cord having such a structure has a call-like form in which the steel cord part 11A is wound around the aramid fiber cord part 10A at the beginning of the load (referred to as an initial form Y1 for convenience). ing. As the load increases, the aramid fiber cord portion 10A gradually expands, and the steel cord portion 11A is gradually wound from a call shape to a straight shape. Then, after the steel cord portion 11A becomes straight, as shown in FIG. 3 (B), the reverse form in which the aramid fiber cord portion 10A is wound around the steel cord portion 11A in a call shape (the latter form for convenience) Y2). In the latter form Y2, since the steel cord portion 11A is dominant, the band cord 9 is not easily stretched rapidly. As a result, as illustrated in a “load-elongation curve” in FIG. 4, it is possible to obtain elongation characteristics necessary for a band cord having low elasticity in the initial form Y1 and high elasticity in the late form Y2. Moreover, since the start timing of the late form Y2 at which the high elasticity region starts is determined by the winding pitch P of the steel cord portion 11A, the winding diameter D (that is, the diameter of the aramid fiber cord portion 10A), etc., the elongation characteristics can be easily and accurately measured. You can control well.

  Furthermore, since the band cord 9 includes an aramid fiber, an increase in weight can be suppressed as compared with a steel cord. That is, it is possible to reduce the weight of the tire and maintain a light feeling in handling stability. Further, since the band cord 9 includes the steel strand 11f, the band cord 9 exhibits higher compression rigidity and bending rigidity than the aramid fiber cord. Accordingly, the tread rigidity can be sufficiently secured, and the steering stability can be improved in combination with the maintenance of the light feeling such as the rigidity at the bank and the traction can be improved.

  Here, in the band cord 9, the elongation L50 at a load of 50N is 0.5 to 0.7%, the elongation L100 at a load of 100N is 1.2 to 1.6%, and the elongation L300 at a load of 300N. It is important that is 2.0 to 2.6%. If the elongation L50 is less than 0.5%, the vulcanization stretch cannot be sufficiently handled, and the tire may be deformed during vulcanization molding. On the other hand, when the elongation L50 exceeds 0.7%, the restraining force of the band layer 7 is insufficient, and there arises a problem that high-speed durability and high-speed straightness deteriorate.

  Also, if the elongation L100 is less than 1.2% and the elongation L300 is less than 2.0%, the restraint force of the band layer becomes excessive, and the tire can be deformed properly when filling with internal pressure or acting on external force. It adversely affects riding comfort, handling stability and durability. On the contrary, when the elongation L100 exceeds 1.6% and the elongation L300 exceeds 2.6%, the restraining force of the band layer becomes too small, and the improvement effect of the steering stability of the present invention cannot be expected. At the same time, the high-speed steering stability and high-speed durability are deteriorated, such as an increase in outer diameter at high speed.

  Each of the elongations L50, L100, and L300 can be set easily, accurately, and accurately by adopting the cord structure.

  If the aramid fiber cord portion 10A is out of the range of 1100 to 1670 dtex, it becomes difficult to set the elongations L50, L100 and L300 within the range.

  In addition, the number of the steel strands 11f is out of the range of 2 to 9, and the balance between the elongation (or tensile elastic modulus) and the cord rigidity is deteriorated, and the tread rigidity is excessively or excessively decreased. It tends to be impossible to exhibit the effect of improving the sex.

  In the steel cord portion 11A, the elongation LA50 at a load of 50 N is set to 0.3% or less in a state before being wound around the aramid fiber cord portion 10A, that is, in a state in which the steel wire 11f is only twisted. It is preferable to do this. If the elongation LA50 exceeds 0.3%, the elastic modulus in the latter form Y2 becomes insufficient, and it becomes difficult to set the elongations L100 and L300 within the above range.

  In the band cord 9, the winding pitch P of the steel cord portion 11A at a load of 50 N is preferably in the range of 6.0 to 12.0 mm, and the steel wire stranding pitch Pa in the steel cord portion 11A is 3.0 to 6. The range of 0 mm is preferable, and the twist pitch Pb of the aramid fibers in the aramid fiber cord portion 10A is preferably in the range of 3.0 to 6.0 mm.

  When the band cord 9 is used under high-temperature and high-humidity conditions, the moisture contained in the aramid fiber may cause rust in the portion of the steel wire 11f that comes into contact with the aramid fiber. Therefore, it is preferable to subject the surface of the steel wire 11f to a plating treatment such as galvanization to prevent rust.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  In order to confirm the effects of the present invention, various band cords were prototyped according to the specifications shown in Table 1, and the characteristics of the sample cords and the performance of the radial tire for motorcycles when the sample cords were used in the band layer were evaluated. went. In the cord of Comparative Example 1, six of nine steel strands are corrugated to increase the elongation at low load. The cord of Comparative Example 3 is not corrugated on the steel strand.

  A radial tire for a motorcycle has the basic configuration shown in FIG. 1 and is different from the band cord only. The common specification is size 180 / 55ZR17, and the carcass was formed of a single carcass ply in which a nylon 66 carcass cord (1400 dtex / 2) was inclined at 90 ° with respect to the tire equator. The number of carcass cords to be driven is 38 (lines / 5 cm). In the band layer, the number of band cords to be driven was 24 (lines / 5 cm).

<Lightweight>
The weight per unit length of each sample cord is shown as an index with Comparative Example 1 as 100. The smaller the index, the lighter.

<Tire vulcanization moldability>
In vulcanization molding of tires, tire deformation due to insufficient stretch was evaluated as --- x, and vulcanization molding was evaluated as good ---.

<Steering stability>
The test tire is mounted on the rear wheel of a motorcycle with a displacement of 750 cc, and is run on a dry asphalt road test course. evaluated.
The “lightness” includes performance items such as responsiveness, cornering, and slalom. The “rigidity” includes performance items such as shock absorption, kickback, and feeling of grounding.

  As shown in the table, it can be confirmed that the Examples can exhibit high rigidity and lightness in actual vehicle running without affecting the vulcanization moldability of the tire and can improve the steering stability.

1 is a cross-sectional view showing an embodiment of a radial tire for a motorcycle according to the present invention. (A), (B) is sectional drawing and the side view which show the band cord used for it. (A), (B) is a side view which shows the change of the twist structure of the band cord by a load load. It is a graph which shows the "load-elongation curve" of a band cord.

Explanation of symbols

2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Band layer 9 Band cord 10 Core 10A Aramid fiber cord part 11 Outer layer 11f Steel strand 11A Steel cord part

Claims (4)

A core composed of an aramid fiber cord portion obtained by twisting aramid fibers, and an outer layer composed of a single steel cord portion obtained by twisting a plurality of steel strands and wound around the core;
Moreover, the elongation at 50N load is 0.5 to 0.7%, the elongation at 100N load is 1.2 to 1.6%, and the elongation at 300N load is 2.0 to 2.6%. A radial tire band cord for motorcycles.   The radial for a motorcycle according to claim 1, wherein the amide fiber cord portion has a bundle twist structure of 1100 to 1670 dtex, and the steel cord portion has a bundle twist structure of 2 to 9 steel strands. Tire band cord.   The band cord of a radial tire for a motorcycle according to claim 1 or 2, wherein the steel cord portion has an elongation at a load of 50 N of 0.3% or less. A carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and arranged radially outside the carcass and inside the tread portion, and the band cord is spiraled at an angle of 5 ° or less with respect to the tire circumferential direction. With a band layer wound in a shape,
The band cord is composed of a core composed of an aramid fiber cord portion obtained by twisting aramid fibers, and an outer layer wound around the core, comprising a single steel cord portion obtained by twisting a plurality of steel strands. Moreover, the elongation at a load of 50 N is 0.5 to 0.7%, the elongation at a load of 100 N is 1.2 to 1.6%, and the elongation at a load of 300 N is 2.0 to 2.6%. A radial tire for motorcycles characterized by

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