JPS6140561B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a motorcycle tire that is excellent in riding comfort, handling stability, durability, etc., and has reduced manufacturing costs. Motorcycle tires are required not only to meet general tire characteristics such as ride comfort, durability, and rolling resistance performance, but also to have handling stability particularly when cornering.
Therefore, the structure of motorcycle tires commonly used in the past has been exclusively cross-ply tires, that is, tires with a carcass made of cords forming a constant angle with respect to the circumferential direction.On the other hand, so-called radial tires have low lateral rigidity, so It is not often used in seeds. Recently, there has been a strong demand for reducing tire raw materials, that is, reducing manufacturing costs, from the viewpoint of resource conservation and economic efficiency. However, it is considered to be extremely difficult to reduce tire constituent elements, particularly carcass plies, as this has a significant effect on tire performance. The present invention provides a motorcycle tire with reduced manufacturing costs while maintaining the important characteristics of a tire, such as ride comfort, handling stability, and durability, at a level equal to or higher than that of conventional cross-ply tires. be. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of the motorcycle tire of the present invention, and FIG. 2 is a plan view showing the arrangement of the carcass and breaker. The tire of the present invention includes a toroidal carcass 1 made of one ply fixed to a pair of left and right bead wires 4 with both ends folded back and arranged from one bead part to the other bead part, and an outer crown of the carcass 1. at least one ply of breaker 2 arranged in the
and a tongue-shaped bead apex 3 disposed in a portion surrounded by the carcass 1 and its folded end 5.
It is equipped with Here, the angle α of the cord of the carcass 1 with respect to the tire circumferential direction is 20° to 80°, and the cord of the breaker 2 is arranged in a direction intersecting this. The folded end portion 5 of the carcass ply 1 extends outward in the tire radial direction and terminates near the tread shoulder portion S. Here, since the cords of the carcass ply 1 and its folded end portion 5 cross each other, lateral rigidity similar to that of a cross-ply tire is obtained from the bead portion where both overlap to the shoulder portion S. From this viewpoint, the angle α of the carcass ply cord with respect to the circumferential direction is preferably 28° to 45°. Furthermore, by terminating the folded end portion 5 of the carcass ply 1 near the shoulder portion S, it is possible to reinforce the sidewall region, which is particularly severely bent. Therefore, the folded end 5
The difference between the height H from the bead heel part and the height h of the shoulder part is within 4.0 cm, preferably both are substantially the same height. The bead apex 3
has a thickness that gradually decreases from the bead wire 4 in the tire radial direction, and its upper end extends near the shoulder portion. The rubber of Bead Apex 3 has a JIS hardness of 50.
The hardness is in the range of 60° to 90°, preferably JIS hardness of 60° to 80°. As long as the bead apex has a hardness within the above-mentioned range, it is possible to use a composite layer of two types in addition to a single layer. In this way, the tire of the present invention has tapered, relatively hard rubber arranged from the bead to the shoulder, which increases lateral rigidity and absorbs and alleviates bending deformation in the sidewall area, further improving ride comfort. do. Next, in the present invention, the width 1 of the breaker 3, that is, the arcuate length along the carcass line is the tread 6.
width L, that is, 80% to 10% of the arcuate length extending from one shoulder part S to the other shoulder part S.
range is used. If it is less than 10%, it cannot function as a breaker sufficiently. On the other hand, if it exceeds 80%, most of the tread portion is reinforced, which increases rigidity and impairs riding comfort. That is, in the present invention, since the region between the breaker end 2a and the folded upper end 5a of the carcass ply is reinforced with only a single layer of carcass ply, flexibility is maintained in this region and riding comfort is improved. From this point of view, the width l of the breaker is suitably in the range of 50% to 20% of the tread width L. The breaker may use a plurality of plies, but in this case it is preferred that the breaker be arranged with steps at both ends. The angle β of the breaker cord with respect to the circumferential direction is arbitrarily selected within the range of 0° to 50°. Conventionally, tires for motorcycles have been used that have a relatively wide tread area in order to improve the handling stability when rolling, which is a characteristic required for motorcycle tires, and the present invention can be suitably applied to such tires. That is,
This is applied to tires in which the height H of the shoulder portion S with respect to the height M from the bead heel portion of the tire is in the range of 30% to 80%. Example 1 As an example of the present invention, a 250-17 size tire with a 4-ply rating was manufactured with the structure shown in FIG. Here, the carcass ply angle α was 45°, the breaker angle β was 45°, and the folding height h of the carcass ply and the bead apex height T were the same as the shoulder height H. The JIS hardness of the bead apex rubber is 75°, and the ratio of breaker width l to tread width (l/L) is 30%.
And so. On the other hand, as a comparative example, a cross-ply tire with two carcass and a four-ply rating was manufactured using tires of the same size. Here, the angle of the carcass cord is 38° with respect to the tire equatorial plane, and the heights of the folded ends are 30 mm and 15 mm, respectively. Table 1 shows the results of measuring the performance of these tires.

【table】

[Table] As is clear from the table, although the number of carcass plies is one, the present invention achieves almost the same or better performance than the conventional cross ply.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the tire of the present invention, and FIG. 2 is a partial plan view showing the arrangement of the carcass and breaker.

Claims (1)

[Scope of Claims] 1. A toroidal carcass 1 consisting of one ply fixed to a pair of left and right bead wires 4 by folding back at both ends and arranged from one bead part to the other bead part, and the outside of the carcass. At least one ply breaker 2 arranged in the crown part
and a tongue-shaped bead apex 3 disposed in a portion surrounded by the carcass 1 and the folded end 5 of the carcass, and the cord of the carcass has an angle α of 20° to 80° with respect to the tire circumferential direction. . A motorcycle tire, wherein the cord of the breaker is arranged in a direction intersecting the cord of the carcass. 2. The tire according to claim 1, wherein the cord of the carcass has an angle α of 28° to 45° with respect to the circumferential direction of the tire. 3. The tire according to claims 1 and 2, wherein the height H of the folded end portion 5 of the carcass ply from the bead heel portion is approximately the same as the height h of the shoulder portion. 4. The tire according to claim 2, wherein the difference between the height H of the folded end portion 5 of the carcass ply and the height h of the shoulder portion is 4.0 mm or less. 5. The tire according to claims 1 to 3, wherein the bead vapors 3 extend to the vicinity of the shoulder portion. 6. The tire according to claims 1 to 4, wherein the bead apex 3 is rubber with a JIS hardness of 50° to 90°.