JP5142933B2 - Pneumatic tires for motorcycles - Google Patents

Description

  The present invention relates to a pneumatic tire for a motorcycle (hereinafter, also simply referred to as “tire”), and more specifically, without touching the tire performance such as straight running performance, high speed performance, and ride comfort, and the stability of ground contact and turning control. The present invention relates to a pneumatic tire for a motorcycle with improved performance.

  A so-called spiral in which a belt-like body in which one or a plurality of parallel cords are embedded in a covering rubber is wound around a pneumatic tire for a motorcycle spirally at an angle toward the tire circumferential direction. It is known that application of a belt layer can improve high-speed durability, straight-line stability, uniformity performance, acceleration performance, and the like of the tire.

As a technique related to the improvement of a steel cord as a reinforcing material in such a spiral belt layer, for example, Patent Document 1 discloses that a tensile elongation of a belt cord made of a spirally wound steel cord is defined in a predetermined manner, so There is disclosed a radial tire for a motorcycle that does not significantly reduce the straightness and turning performance in the vehicle and that maintains the handling property and improves the wear resistance. Patent Document 2 discloses a motorcycle radial tire defined by a load-elongation curve of a band cord constituting a spirally wound belt-like ply.
JP-A-4-362402 (Claims etc.) JP 2001-130218 A (Claims etc.)

  However, today, there is a strong demand for performance characteristics that give the two-wheeled driver a sense of security with the feeling of ground contact between the tire and the road surface that is felt when changing direction or turning.

  Accordingly, an object of the present invention is to provide a pneumatic tire for a motorcycle that has improved ground contact stability and turning maneuverability without impairing various tire performances such as straight running performance, high speed performance, and riding comfort. .

  As a result of diligent studies to solve the above problems, the present inventor has found that the rigidity in the circumferential direction is important when the tire contacts the ground, and by making this suitable, the road surface and It became clear that the familiarity was improved and the feeling of grounding could be improved. That is, since the tread radius of the two-wheeled vehicle is small, when the tire is pressed against the road surface by a load, tensile tension is applied in the tire circumferential direction at the edge in the tire width direction. It was found that by lowering the tensile rigidity in the circumferential direction, it fits well to the road surface to the edge, transmits braking / driving force and lateral force to the road surface, improves the limit performance, and gives the driver a sense of security. . On the other hand, if the rigidity is too low, the tire is easily deformed and the generated force is reduced. Previously, it was difficult to improve both at the same time, so emphasis was placed on the force by placing a circumferential reinforcing material and changing the type (steel or organic fiber) to suit the user's preference, It was used properly with emphasis on.

  The inventor obtained the knowledge that this circumferential rigidity can be achieved by having different characteristics at low internal pressure and high internal pressure, and based on the knowledge, as a result of further earnest studies, The inventors have found that the above problems can be solved, and have completed the present invention.

That is, the pneumatic tire for a motorcycle according to the present invention includes a tread portion, a pair of sidewall portions disposed radially inward from both edges of the tread portion, and a radially inner side of the sidewall portion. At least one layer of carcass ply in which each part is reinforced between bead cores embedded in the bead part, and a cord forming 60 to 90 degrees with respect to the tire equatorial plane is covered with rubber. A pneumatic tire for a motorcycle comprising: a carcass layer comprising: and at least one spiral belt formed on the outer side in the tire radial direction of the carcass layer in a spiral manner substantially parallel to the tire equatorial plane.
The following formula,
Low internal pressure growth rate A = ((periphery of center part at 130 kPa / outer part of center part at 30 kPa) -1) × 100 [%]
High internal pressure growth rate B = ((periphery of center part at 400 kPa / outer part of center part at 300 kPa) -1) × 100 [%]
The low internal pressure growth rate A and the high internal pressure growth rate B represented by
B ≦ 0.2,
0.1 ≦ A ≦ 0.4
A pneumatic tire for a motorcycle that satisfies the relationship expressed by:

In the pneumatic tire for a motorcycle of the present invention, the low internal pressure growth rate A and the high internal pressure growth rate B are expressed by the following equations:
A / B ≧ 1.2
And the high internal pressure growth rate B is preferably represented by the following formula:
0.1 ≦ B
It is preferable that the relationship represented by the following is satisfied, and the low internal pressure growth rate A is
0.14 ≦ A ≦ 0.3
The spiral belt is preferably reinforced with a steel wire body. Moreover, it is preferable that the steel wire is a typed steel strand, further, the steel wire is preferably a typed still cord, and the spiral belt has different tensile properties. It is preferable that it is reinforced with two or more types of linear reinforcing materials having

  According to the present invention, by setting the pneumatic tire for a motorcycle to the above-described configuration, the grounding stability and the turning maneuvering performance are improved without impairing the tire performances such as the straight traveling performance, the high speed performance, and the riding comfort. A pneumatic tire for a motorcycle can be provided.

Hereinafter, preferred embodiments of the present invention will be described in detail.
FIG. 1 shows a schematic cross-sectional view of an example of a pneumatic tire for a motorcycle according to the present invention. As shown in the figure, the tire of the present invention includes a tread portion 11, a pair of sidewall portions 12 disposed on the inner side in the tire radial direction from both edge portions thereof, and a bead portion 13 connected to the inner side in the tire radial direction. The carcass is composed of at least one layer of carcass ply in which these parts are reinforced between the bead cores 21 embedded in the bead part 13 and the cords forming 60 to 90 ° with respect to the tire equatorial plane are covered with rubber. The layer 22 and at least one spiral belt layer 23 spirally formed substantially parallel to the tire equatorial plane are provided on the outer side in the tire radial direction.

In the tire of the present invention, ((the outer periphery of the center portion at 130 kPa / the outer periphery of the center portion at 30 kPa) -1) × 100 [%] is the low internal pressure growth rate A, ((the outer periphery of the center portion at 400 kPa / 300 kPa). Center part outer periphery) -1) × 100 [%] when high internal pressure growth rate B, respectively,
B ≦ 0.2,
0.1 ≦ A ≦ 0.4
It is important to satisfy this relationship. By setting B ≦ 0.2, rigidity when exerting force is ensured, and rigidity at the time of braking / driving and turning can be enhanced. On the other hand, if B> 0.2, sufficient rigidity cannot be obtained, and the turning feeling is deteriorated.

  Further, by setting A ≧ 0.1, when the tire contacts the road surface, the widthwise contact edge extends well, fits well on the road surface, and the feeling of contact is improved. Moreover, the limit which starts to slide improves and turning performance also improves. On the other hand, when A <0.1, the rigidity becomes high, and the effect of the invention of improving fit cannot be obtained. On the other hand, when A> 0.4, the rigidity becomes too low, affecting the shape of the tire, making it difficult for force to be generated, and worsening the turning feeling.

  Since it becomes less sensitive to road surface irregularities and the riding comfort is improved, preferably B ≦ 0.1, and in order to achieve both high fit and rigidity, preferably 0.14 ≦ A. ≦ 0.3.

  Here, the calculation of the low internal pressure growth rate A used the outer periphery of the center portion at 30 kPa and 130 kPa. The reason for selecting 30 kPa is that at 0 kPa (without air filling), the tires and wheels run idle and the outer circumference cannot be measured, and assuming a low internal pressure, 130 kPa is set as a high value from 30 kPa to 100 kPa. Adopted.

  On the other hand, the high internal pressure growth rate B was calculated using the outer periphery of the center portion at 300 kPa and 400 kPa. In the two-wheeled tire, the specified internal pressure is 280 kPa, and the input applied to the tread at the time of initial cornering (low lateral force) is assumed to be 300 kPa, assuming only the internal pressure filling pressure, and 400 kPa is set as a value 100 kPa higher than 300 kPa. Selected. This value is equivalent to an imaginary value obtained only by the internal pressure filling pressure when a large lateral force enters the tread due to high-speed cornering.

  In the present invention, the ratio of the low internal pressure growth rate A and the high internal pressure growth rate B is preferably A / B ≧ 1.2. By setting A / B ≧ 1.2, it is possible to clearly feel the sharpness when the vehicle goes straight at low speed and when the direction is changed or when the vehicle is accelerated, and the turning feeling is further improved.

  Means for imparting the above characteristics to the tire include applying a reinforcing material having a non-linear tensile property to the spiral belt layer, or combining reinforcing materials having different tensile properties. Such a reinforcing material is preferably a steel wire body such as a shaped steel cord or a steel strand. For example, the circumferential rigidity of the tire can be made within the scope of the present invention by embedding by appropriately driving, without twisting appropriately shaped steel strands.

Hereinafter, the present invention will be described in detail with reference to examples.
(Examples 1-10, Comparative Examples 2-4)
A tire of the type shown in FIG. 1 having a low internal pressure growth rate A and a high internal pressure growth rate B described in Tables 1 to 3 is used as a spiral reinforcing wire having the structure shown in Tables 1 to 3 below. Produced. The tire size was 190 / 50ZR17 016RAZ. The obtained test tire was evaluated for the feeling of ground contact, turning performance and vibration absorption as follows.

(Comparative Example 1)
Except for using Kevlar as the spiral reinforcing wire, tires similar to those in Examples 1 to 10 and Comparative Examples 2 to 4 were produced and evaluated in the same manner.

(Grounding feeling, turning performance, vibration absorption)
The test tire is mounted on a 100cc sports type motorcycle with a rim size of MT 6.00x17 at an air pressure of 250 kPa and is run on a test track. It feels grounding, turning performance, and vibration absorption during high-speed cornering. The properties were evaluated by a 10-point method based on the feeling of a test driver.

  As can be seen from the above Tables 1 to 3, it can be seen that the tires of the examples are all superior in touch feeling, turning performance, and vibration absorption compared to the tires of the comparative examples.

  FIG. 2 is a graph showing the relationship between internal pressure (kPa) and internal pressure growth (%) in tires of Examples 1 to 10 and Comparative Examples 1 to 4. Examples 1 to 10 draw a gently downward convex curve. On the other hand, the comparative example 1 extends substantially linearly, the high internal pressure growth rate B is 0.23, and sufficient rigidity is not obtained. In Comparative Example 2, since there is no escape space for rubber surrounded by the spiral belt reinforcing wire (see the structure in Table 1), a non-linear structure cannot be taken and the rigidity is high from the beginning. Further, in Comparative Examples 3 and 4, since the die circumscribed circle diameter D is large (see the structure in Table 1), the high internal pressure growth rate is large, and the desired effect of the present invention cannot be obtained.

1 is a schematic cross-sectional view showing a pneumatic tire for a motorcycle according to the present invention. It is a graph showing the relation between internal pressure (kPa) and internal pressure growth (%) in tires of Examples 1 to 10 and Comparative Examples 1 to 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Tread part 12 Side wall part 13 Bead part 21 Bead core 22 Carcass layer 23 Spiral belt layer

Claims (8)

A tread portion, a pair of sidewall portions disposed on the inner side in the tire radial direction from both edges of the tread portion, and a bead portion continuous on the inner side in the tire radial direction of the sidewall portion. A carcass layer comprising at least one carcass ply that is reinforced between bead cores embedded in each other and that is coated with rubber at 60 to 90 degrees with respect to the tire equatorial plane, and the tire radial direction of the carcass layer In a pneumatic tire for a motorcycle, including at least one layer of spiral belt formed on the outside and spirally wound substantially parallel to the tire equator plane,
The following formula,
Low internal pressure growth rate A = ((periphery of center part at 130 kPa / outer part of center part at 30 kPa) -1) × 100 [%]
High internal pressure growth rate B = ((periphery of the center part at 400 kPa / outer part of the center part at 300 kPa) -1) × 100 [%],
The low internal pressure growth rate A and the high internal pressure growth rate B represented by
B ≦ 0.2,
0.1 ≦ A ≦ 0.4
A pneumatic tire for a motorcycle, characterized by satisfying the relationship expressed by: The low internal pressure growth rate A and the high internal pressure growth rate B are expressed by the following equations:
A / B ≧ 1.2
The pneumatic tire for a motorcycle according to claim 1, satisfying a relationship represented by: The high internal pressure growth rate B is the following formula:
0.1 ≦ B
The pneumatic tire for a motorcycle according to claim 1 or 2, satisfying a relationship represented by: The low internal pressure growth rate A is the following formula:
0.14 ≦ A ≦ 0.3
The pneumatic tire for a motorcycle according to any one of claims 1 to 3, satisfying a relationship represented by:   The pneumatic tire for a motorcycle according to any one of claims 1 to 4, wherein the spiral belt is reinforced with a steel wire.   The pneumatic tire for a motorcycle according to claim 5, wherein the steel wire body is a shaped steel wire.   The pneumatic tire for a motorcycle according to claim 5, wherein the steel wire strip is a molded still cord.   The pneumatic tire for a motorcycle according to any one of claims 1 to 4, wherein the spiral belt is reinforced with two or more types of linear reinforcing materials having different tensile characteristics.

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