JPS62113605A - Radial tire for motorcycle - Google Patents

Abstract

PURPOSE:To enhance the control stability of a low aspect ratio radial tire having a spiral belt layer, by specifying the twisting strength and porosity of a belt layer for a front and rear wheel, and the relationship between these values. CONSTITUTION:In a tire in which a spiral belt layer 6 having a cord angle of 0 deg. is laid outside of a carcass layer 4 and which has a low aspect ratio such that the ratio H/TW between the tire tread width TW and the tire cross- sectioned height H is less than 0.75, the strength A per twisted cord in the belt layer 6 is set to be more than 30kg but less than 60kg for a front wheel (AF), while more than 40kg but less than 90kg for a rear wheel (AR). Further, the porosities BF, BR thereof are set to the more than 20% and 50%, respectively. Further, combination is made so that predetermined relationships among the above-mentioned values AF, AR, BF, BR may be established. With this arrangement, it is possible to enhance the control stability of the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a radial tire for two-wheeled vehicles, particularly to a combination of belt structures for front tires and rear tires.

(Prior Art) Conventionally, as a belt layer provided on the radially outer side of the carcass layer of the tire tread portion of a radial tire for two-wheeled vehicles,
A structure consisting of at least two layers of belts was adopted, but in order to respond to the increasing speed and weight reduction of recent motorcycles, especially for tires with a very small aspect ratio, the carcass layer of the tire tread was A radial tire has been developed that includes a so-called spiral belt, which is a single-layer belt around which a single twisted cord is continuously wound at a cord angle of substantially 0° with respect to the circumferential direction of the tire.

(Problems to be Solved by the Invention) However, in a radial tire having one belt layer composed of such a spiral belt, it is difficult to ensure the handling stability of a two-wheeled vehicle compared to the conventional at least two belt layers. It has been found that this is more difficult than radial tires with

Maneuverability of a two-wheeled vehicle refers to the vehicle's responsiveness and responsiveness during cornering and slalom, and stability refers to how difficult it is to generate rapid vibrations in the front and rear wheels when going straight and turning. These characteristics are evaluated based on the rider's feeling in the actual vehicle.

Therefore, an object of the present invention is to improve the steering stability of a pneumatic radial tire for two-wheeled vehicles having a single-layer belt structure composed of the above-mentioned spiral belt and having a low aspect ratio.

(Means for Solving the Problems) As a result of various tests to improve the handling stability of a radial tire having a single-layer belt structure, the inventor found that the strength of the belt layer of the front tire It was discovered that good steering stability can be obtained by appropriately selecting a combination of the strength of the belt layers of the rear tire.

Therefore, according to the present invention, as shown in the drawings, the tread portion l, the pair of sidewall portions 2, and the bead portions 3
and the carcass cord is 70' in the tire circumferential direction.
at least one carcass layer 4 arranged at a cord angle of ~90' and extending from one bead section to the other; and at least one carcass layer 4 radially outwardly of this carcass layer.
The real twisted cord 5 is substantially 0° with respect to the tire circumferential direction.
It has one belt layer 6 that is continuously wound at a cord angle of , and has a tire tread width Tw and a tire cross-sectional height H.
In a radial tire for two-wheeled vehicles with a low aspect ratio H/Tw of 0.75 or less, the strength A of each twisted cord 5 of the belt layer 6 is the front tire (AP).
Then, 30≦AP≦60kg, rear tire (A11)
In this case, 40≦AR≦90 kg, and the void ratio B of the belt layer 6 is the same as that of the front wheel and rear wheel tires (BP, B
R) 20%≦8. =BR≦50%,
The following relationship 1500 between Ap, At, Bp and BR
kg%ku＾F X (100-OF) <At X (
100-BJ <7200kg%1.

In the radial tire for two-wheeled vehicles according to the present invention, twisted organic fiber cords or steel cords can be used as belt cords forming the belt layer.

(Function) The front tire belt cord strength A exceeds 60 kg, and the front tire belt void ratio B.

If it is less than 20%, the turning performance and straight-line performance (stability) will deteriorate, and you will not be able to get a feeling of ground contact.If the strength A is less than 30 kg and the air ratio BF is more than 50%, a feeling of rigidity will be obtained. , responsiveness, and response linearity are lost.

The strength A of the belt cord of the rear tire exceeds 90 kg, and the belt void ratio B of the rear tire.

If it is less than 20%, the turning performance and straight-line performance (stability) deteriorate, and rapid vibration occurs in the front and rear wheels. This results in a loss of responsiveness and response linearity.

Furthermore, APX(100-BP)>ARX(100-B
In case R), the motorcycle collapses from the rear side when turning, and the stability of the two-wheeled vehicle when turning is lost.

(Example) Table 1 shows Examples (B, C) according to the present invention and Comparative Example (A
, D, E! , F, G, H, I, J). The tire sizes in these Examples and Comparative Examples were 120/60 VR18 for the front tire and 150/60 VR1g for the rear tire.

(Effects of the Invention) In order to confirm the effects of the present invention, actual vehicle tests were conducted on the Examples and Comparative Examples, and the results are shown in Table 1.

In this test, a 1000 cc motorcycle was equipped with the combinations of tires shown in Table 1, and was run on a circuit with a circumference of 5.5 km at a maximum speed of 230 km, and the rider's feeling was evaluated. The vehicle evaluation was based on a 10-point scale, with scores of 60 or higher being considered good.

[Brief explanation of drawings]

The drawing is a partial longitudinal sectional view of a tire according to the invention.

Claims (1)

[Claims] 1. It has a tread part, a pair of sidewall parts, and a beat part, and the carcass cord is 70° in the circumferential direction of the tire.
at least one carcass layer arranged at a cord angle of between 90° and 90° and extending from one bead to the other; and at least one carcass layer radially outwardly of this carcass layer.
In a radial tire for a two-wheeled vehicle with a low aspect ratio, the belt layer has one belt layer in which a single twisted cord is continuously wound at a cord angle of substantially 0° with respect to the circumferential direction of the tire. The strength A of one cord is 30≦A_F≦60k for front tire (A_F)
g, 40≦A_R≦90 for rear tire (A_R)
kg, and the void ratio B of the belt layer is 20% for both front and rear tires (B_F, B_R).
≦B_F, B_R≦50%, and A_F, A_R, B
The following relationship between _F and B_R is 1500kg%<A_F×(100-B_F)<A_R
A radial tire for a two-wheeled vehicle, characterized in that it is combined so that x(100-B_R)<7200kg% is satisfied. 2. The tire according to claim 1, wherein the belt cord forming the belt layer is made of organic fiber. 3. The tire according to claim 1, wherein the belt cord forming the belt layer is a steel cord.