JPH04197805A - Pneumatic radial tire for two-wheeler - Google Patents

Abstract

PURPOSE:To improve lateral forces on a large camber so as to cause a pneumatic radial tire to exhibit its excellent effects as a high-performance tire by disposing a hard rubber layer of specified thickness in a predetermined portion of the tire. CONSTITUTION:A tread portion is formed in such a manner as being divided in its cross direction into three areas, i.e., a center area and both side areas. At least one of both side areas is formed by two layers of outer layer rubber 4 and inner layer rubber 3 and also the JIS hardness of the inner layer rubber 3 is higher than that of the outer layer rubber 4 by at least more than 5 deg.; i.e., the inner layer rubber 3 which is higher in JIS hardness(Hd) than the tread outer layer rubber 4 by more than 5 deg. is disposed between a belt 2 located on a carcass ply 1 and the tread outer layer rubber 4 throughout one fourth the width W of the tread. Lateral forces applied to a pneumatic radial tire on a large camber are thereby improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pneumatic radial tire for two-wheeled vehicles.

(Prior technology) Pneumatic radial tires for motorcycles, which have a belt structure in which a reinforcing coat is arranged almost in the circumferential direction of the tire, exhibit excellent performance in high-speed durability and straight-line stability, but the drawback is that lateral force at large camber One example is the shortage. That is, it has a problem of low lateral rigidity. This is because a normal bias structure has an intersecting layer of carcass plies, whereas a radial structure has an intersecting layer of carcass plies, and the side rigidity is low.

In this way, radial tires lack lateral force at large cambers, resulting in insufficient performance as motorcycle tires.Conventional techniques for improving this point include increasing the elastic modulus of the case rubber and increasing the case rigidity. Consideration has been given to whether this can be addressed by improving the Also, attempts have been made to arrange a hard rubber layer as a heath rubber, similar to the conventional canopoo heath structure.

(Problems to be Solved by the Invention) However, none of the conventional techniques for improving radial tires as tires for two-wheeled vehicles was satisfactory. That is, in the above-mentioned improved technique of increasing the elastic modulus of the case rubber to improve the case rigidity, there was a problem in that the side rigidity increased, resulting in poor ground contact and a decrease in grip performance.

In addition, in an attempt to adopt a camp-heath structure and arrange the hard rubber layer as heath rubber with a uniform thickness, the initial good ground contact was lost, and this also could not be put to practical use.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire for two-wheeled vehicles with an improved tread structure that can significantly improve lateral force during large camber.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventor has developed a pneumatic radial tire for two-wheeled vehicles by arranging a specific hard rubber layer at a predetermined location at the end of the belt. camber
The present inventors have discovered that the lateral force at the time of application can be significantly improved, and have completed the present invention.

That is, the present invention provides a pneumatic radial tire for two-wheeled vehicles having a heddle structure arranged approximately in the circumferential direction of the tire, in which the tread portion is formed in three areas in the width direction, a central area and both side areas, and the both side areas are the same as the tread width. Located from the 1/4 point to the tread edge, at least a part of the area is formed of two layers, an outer rubber layer and an inner rubber layer, and the inner rubber layer is JIS
The present invention relates to a pneumatic radial tire for two-wheeled vehicles, characterized in that the hardness is at least 5° greater than the JIS hardness of the outer layer rubber.

Note that the above-mentioned 1/4 point is not particularly strictly defined, and may be approximately 1/4.

To explain specifically based on the drawings, the pneumatic radial tire for two-wheeled vehicles as an example of the present invention shown in FIG. Layer 3) is disposed between the belt 2 on the carcass ply 1 and the tread outer layer rubber 4 over a quarter of the tread width W.

(Function) In the present invention, the hard rubber layer is arranged from the center of the tread to the 1/4 point of the tread width to the tread edge when the camber is large (4.0 to 45 degrees). This is because the ground contact point of the tire in ) is between the points.

In addition, the hard rubber layer has a Hd of 5° higher than the tread outer layer rubber.
The reason why it is set higher than this is because Hd must be 5 degrees or more to sufficiently improve the lateral force at the time of large camber.

According to the present invention, even if a part of the tire shoulder touches the ground at a large camber angle of 40 to 45 degrees, it is possible to prevent the belt from deforming due to the arrangement of the hard rubber layer, and also to reduce the shearing force caused by the hard rubber layer. This improvement can compensate for the weakness of the side parts of the radial structure.

The inner layer rubber is preferably arranged below the groove bottom of the tread portion. More preferably, the groove bottom of the tread portion is 0.5 m.
m or less.

When the total volume of the outer layer rubber and the inner layer rubber extending from the 1/4 point to the tread edge is taken as 100, the ratio of the inner layer rubber to the total volume is preferably 5 to 60%.

More preferably, it is 10 to 45%.

Preferably, the inner rubber layer has a substantially uniform width and thickness.

Hardness test method For hardness test, JIS K6301, vulcanized rubber physical test method hardness test (spring type hardness test type A)
It was carried out based on the following.

(Example) Next, the present invention will be specifically explained using examples.

The hardness, shape, and width of the hard rubber layer shown in FIG. 1 were changed as shown in Table 1 below, and the tire size was 170/
A 60 R17 pneumatic tire for two-wheeled vehicles was prototyped.

As a performance evaluation of the Cholera prototype tire, the value when the lateral force reaches the maximum value (CFmax) when the slip angle is applied at a large camber angle (45°) is calculated from the tire without a hard rubber layer (Comparative Example 1). is expressed as an index with 100. The higher the number, the better the result. The obtained results are also listed in Table 1.

(Effects of the Invention) As can be seen from the test results shown in Table 1, in the pneumatic radial tire for motorcycles of the present invention, by arranging a hard rubber layer with a specific hardness at a predetermined location, can significantly improve the lateral force of
In particular, it can be expected to exhibit excellent effects as a high-performance tire.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an example tire of the present invention.

Claims (1)

[Scope of Claims] 1. In a pneumatic radial tire for two-wheeled vehicles having a belt structure consisting of cords arranged approximately in the circumferential direction of the tire, the tread portion is formed in three areas in the width direction, a central area and both side areas, and The area is located from the 1/4 point of the tread width to the tread edge, and at least a part of the area is formed of two layers, an outer rubber layer and an inner rubber layer, and the JIS hardness of the inner rubber layer is at least higher than the JIS hardness of the outer rubber layer. A pneumatic radial tire for two-wheeled vehicles characterized by being larger than 5 degrees.