JPH01109106A - Pneumatic radial tire for motorcycle - Google Patents

Abstract

PURPOSE:To improve a high speed durability, a turning stability and a road surface gripping force by constituting a belt ply arranged on the outside of a carcass ply at a tire crown portion, with a cross belt ply and a spiral belt ply. CONSTITUTION:A motorcycle tire has a tread portion 1, a sidewall portion 2 extending toward the inner part of a radial direction from its both ends and bead portions 3. The tire is equipped with an at least more than 1 ply carcass 5 with both ends turned up around bead cores 4 and whose cord angle is arranged in the range of 75-90 degrees against the circumferential direction of the tire, and a belt ply 6 arranged in its outer part. In this instance, the belt ply 6 is constituted with more than 2 cross belt plies 7 whose cord angle against the tire circumferential direction is 30-10 degrees, and a more than 1 spiral ply 8 whose cord angle is virtually 0 degree, and the spiral ply 8 is to be arranged between respective plies 5, 7.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a belt structure for a pneumatic radial tire for motorcycles, and in particular, to a belt structure for improving high-speed durability, turning stability, and road gripping force. This invention relates to a belt structure that combines a cross belt and a spiral belt.

(Prior Art) Conventionally, as a combination belt structure of this type of cross belt and spiral belt, for example, Japanese Patent Application Laid-Open No. 60-3821
As disclosed in Publication No. 0, ``A spiral cord in which the cord extends approximately parallel to the tire circumferential direction at the center part of the outside in the radial direction of the cross belt in which the cord extends approximately parallel to the radial direction in the tire crown portion. Types with arrayed belts and Japanese Patent Application Laid-Open No. 60-53404
As disclosed in Japanese Patent Application Publication No. 2003-11000, a type of spiral belt is known in which a spiral belt is disposed on the radial outer side of a cross belt with a width covering almost the entire tread width.

(Problems to be Solved by the Invention) The motorcycle tires disclosed in the above-mentioned publications all have excellent high-speed durability, but have the following drawbacks.

In either case, if higher lateral force generation is required, it is necessary to increase the number of spiral belts or change to a high tension yarn. As described above, in both structures in which the spiral belt is disposed outside the cross belt, the spiral belt does not significantly contribute to the generation of lateral force, so the cornering force during turning becomes low. In the former case, it affects when driving with a small camber angle, and in the latter case, the cornering force decreases in general when driving with a camber angle from a small angle to a large angle, and the road grip force is not obtained. In particular, in the former case, if an attempt is made to increase the number of spiral belt layers by laminating multiple layers, the difference in rigidity will increase between the end area of the spiral belt and the boundary area of the cross belt, which will affect the cornering characteristics, especially when traveling straight. There is a problem in that the stability at the time of transition between turning and cornering is deteriorated. Moreover, in the latter case, there is a problem that it takes time to wind the cord spirally around the cross belt, resulting in a large loss of time for forming operations.

An object of the present invention is to advantageously improve the above-mentioned drawbacks and provide a pneumatic radial tire for two-wheeled vehicles that not only has excellent high-speed durability but also excellent cornering characteristics and excellent productivity. be.

(Means for Solving the Problems) According to the present invention, as shown in FIG. A carcass of at least one layer, which has a bead portion 3 located at the inner end of the tire, is arranged at a cord angle in the range of 75 to 90 degrees with respect to the circumferential direction of the tire, and has both ends folded back around a bead core 4. A belt ply 2 comprising a ply 5 and a belt ply 6 disposed on the outside of the carcass ply 5 in the radial direction.
In the pneumatic radial tire for wheeled vehicles, the belt ply 6 has a cord angle of 30 to 10 with respect to the tire circumferential direction.
2 or more layers of cross belt ply 7 with a cord angle of substantially 0° and one or more layers of spiral belt ply 8 with a cord angle of substantially 0°, and spiral belt ply 8 is arranged between carcass ply 5 and cross belt ply 7. It is characterized by

In carrying out the present invention, the cross belt verifiy width B8 is 65 to 1 of the tread peripheral width Tw.
05%, and the verimeter width Sw of the spiral belt is preferably 25 to 55% of the tread peripheral width T-.

(Function) When comparing pneumatic radial tires for motorcycles with a cross belt structure and pneumatic radial tires for motorcycles with a cross + spiral structure, the relationship between belt bending rigidity, turning stability, and road grip (grip) is as follows. In a tire with a cross belt structure, as shown in Fig. 2, the turning stability C and road grip force G are in a contradictory relationship with the belt rigidity, but by adopting a cross + spiral belt structure, as shown in Fig. 3, It turns out that the reciprocal relationship can be resolved.

As a result of further investigation into the characteristics of the cross + spiral belt structure, we found that by having the spiral belt bear a large amount of the tension at the center of the tire crown, the ply tension of the cross belt is relatively reduced, and in this way the cord of the cross belt takes on the burden. The lower the tension is, the shorter the vibration damping time when the cross belt cord is vibrated due to disturbance while running, which means the damping effect increases, and the turning stability improves. There was found. .

Therefore, according to the present invention, by inserting the spiral belt between the carcass and the cross belt in the crown central region, the elongation of the belt ply as a whole is suppressed, and the spiral belt in the crown central region reduces tension. By reducing the tension burden on the cross belt, the damping effect is improved, and the rigidity difference in the boundary area between the spiral belt and the cross belt is reduced (and by placing the cross belt in front of the road surface). It is possible to greatly contribute to the radial shearing force of the cross belt, thereby improving turning stability and road gripping force.

(Example) An example of the present invention is shown in FIG. The tire size is 150/70VR18CYO4"?', and the carcass ply 5 is made of two layers of nylon cords, which are arranged in directions that intersect with each other at a cord angle of 80@ with respect to the tire circumferential direction. A belt braai 6 is configured. spiral belt 8
consists of two layers and is arranged radially outward at the crown center of the carcass ply 5 with a cord angle O0, and two layers of cross belts 7 are arranged radially outward of the spiral belt 8 with a cord angle 15''.

As mentioned above, the spiral belt 8 is connected to the cross belt 7.
When disposing the spiral belt 8 on the inside of the carcass ply 1 and on the outside of the carcass ply 1, the spiral belt 8 is prepared in a cylindrical shape in the previous step, and this cylindrical spiral belt is fitted to a forming drum in the belt forming step to form the carcass ply 1. ° It can be pasted on the lie, thus greatly improving molding efficiency.

Periphery width B of cross belt 7. is 87% of the tread peripheral width T8, which is the peripheral width S of the spiral belt 8. is also 45%.

In addition, the number of strokes for each is 28 for spiral belt 8.
16 pieces/25 m+ for cross belt 7
It is a.

In order to confirm the effects of the present invention, a pneumatic radial tire for a two-wheeled vehicle according to the embodiment of the present invention described above was prepared under the same conditions as the embodiment of the present invention except that the spiral belt was disposed outside the cross belt. A pneumatic tire for a two-wheeled vehicle according to a comparative example was tested on an actual vehicle to evaluate its actual vehicle dynamic performance and high-speed durability.

The interlocking performance with the actual vehicle was evaluated based on the feeling in the normally conducted actual vehicle test for motorcycle tires, and the high-speed durability was evaluated when the tire crown was destroyed when driving on a drum and increasing the speed from 170 h/h every 20 minutes. The vehicle was evaluated based on speed and travel time.

The results of the actual vehicle feeling test are shown in Fig. 4 as the above-mentioned evaluation results.The high-speed durability test results show that the comparative example broke at 270h/h, but the tire according to the present invention broke at 280h/h.
Destruction occurred at 0IC11/h.

In addition, the time required for molding was measured L7 and the molding efficiency was also evaluated.The tire according to the present invention is similar to the comparative tire by preparing the spiral belt on the carcass ply into a cylindrical shape in the previous process and molding it as a belt package. The molding time was significantly reduced.

As is clear from the above, according to the present invention, a pneumatic radial tire for motorcycles is superior not only in grip feeling and turning stability, but also in high-speed durability and productivity compared to conventional tires. can be provided.

(Effects of the Invention) The pneumatic radial tire for two-wheeled vehicles of the present invention can improve high-speed durability, turning stability, and road gripping force.

[Brief explanation of the drawing]

FIG. 1 is a schematic radial cross-sectional view of a pneumatic radial tire for a motorcycle according to the present invention, and FIG. 2 is a diagram showing the relationship between belt bending rigidity, road gripping force, and turning stability of a pneumatic radial tire for a motorcycle having a cross-belt structure. graphs showing relationships,
Figure 3 is a graph showing the relationship between belt bending rigidity, road gripping force, and turning stability of a pneumatic radial tire for two-wheeled vehicles with a cross + spiral belt structure. Figure 4 is a graph showing the turning stability of tires according to the present invention and a comparative example. and a graph showing the feeling evaluation results of road grip force. 1... Tread part 2... Sidewall part 3... Bead part 4... Bead core 5...
・Carcass ply 6...Belt ply 7...Cross belt 8...Spiral belt Figure 1 Figure 2 Root gap (・1

Claims (1)

[Scope of Claims] 1. It has a tread portion, a sidewall portion extending radially inward from both ends of the tread portion, and a bead portion located at the radially inner end of the sidewall portion; at least one layer of carcass ply arranged with a cord angle in the range of 75 to 90 degrees and both ends folded around the bead core; and a belt ply arranged radially outward of the carcass ply at the tire crown. In a pneumatic radial tire for two-wheeled vehicles, the belt ply includes two or more cross belt plies with a cord angle of 30 to 10 degrees with respect to the tire circumferential direction, and one or more spiral belt plies with a cord angle of substantially 0 degrees to the tire circumferential direction. A pneumatic radial tire for a motorcycle, characterized in that a spiral belt ply is arranged between a carcass ply and a cross belt ply.