JPS61247502A - Tire for motorcycle - Google Patents

Abstract

PURPOSE:To ensure running stability at cornering, high-speed stability and reduction in weight, by arranging a bead apex having a high JIS hardness in the vicinity of both ends of a tread in a tire having a cross ply structure. CONSTITUTION:A tire 1 includes a carcasses 2 and 3 folded around a bead core 7, a bead apex 6 arranged between the carcasses 2 and 3 and their folded portions 2a and 3a, and a single belt layer B constituted of plies 4 and 5 arranged outside a crown portion of the carcasses 2 and 3. The carcasses 2 and 3 are arranged at angles of 15 deg.-35 deg. with respect to a circumference of the tire. A JIS hardness of the bead apex 6 is set to 65 deg.-95 deg., and a height H1 thereof is set to 65%-110% of a height H up to a tread end. With this arrangement, lateral rigidity of a tire side portion may be improved, and high-speed durability and reduction in weight may be ensured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides stable running performance during cornering, high-speed durability,
This invention relates to motorcycle tires with improved high-speed stability and weight reduction.

[Conventional technology]

Motorcycle tires have a structure with high lateral rigidity, that is, tires with a cross-ply structure are widely used because of the need to maintain running stability during cornering, since the vehicle body tilts significantly when cornering. ing. On the other hand, recently there has been a demand for vehicles with even higher levels of high-speed running characteristics.

Conventionally, in order to maintain stable running during cornering, it has been necessary to increase the rigidity of the side parts, and for this reason, methods have been taken to increase the number of carcass plies or the denier of the carcass ply cord. However, this method inevitably increases the rigidity of the crown part and increases the thickness of the tire, resulting in a decrease in high-speed durability and stable straight running performance, and an increase in tire weight.

[Problem to be solved]

The object of this invention is to propose a motorcycle tire that improves the lateral rigidity of the tire side part, improves high-speed durability performance, and straight-line running performance, and reduces weight, which are contradictory.

[Technical means]

This invention consists of at least two plies in which the organic fiber cord is arranged at an angle of 15° to 35° with respect to the center plane in the circumferential direction of the tire. A JI extending between the carcass and the folded part in a range of 65% to 110% of the height from the bead bottom to the tread edge.
This is a motorcycle tire characterized by having a bead apex with an S hardness of 65° to 95°.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the right half of the cross-sectional view of the tire of the present invention. In FIG. The belt layer B is provided with a bead apex 6 arranged and one ply 4.5 arranged outside the crown part of the carcass. Here, carcass 2.3 is 15° to the tire circumferential direction.
They are arranged at an angle of ~35°. In conventional bias tires, the carcass cords are usually arranged at a high angle in the range of 30° to 40° to the tire circumferential direction, and in the comparative example, the cords are arranged at a shallow angle in the tire circumferential direction. By doing so, the lateral rigidity of the tire side portion is further improved. The carcass has at least two layers, and the cord material is an organic fiber cord such as nylon, polyester, rayon, or aramid. The height HT of the higher one of the folded parts 2a and 3a of the carcass is in the range of 65% to 120% of the height H from the bead bottom to the tread end TE, which has the effect of reinforcing the side part.

Next, between the carcass 2.3 and its folded portion 2a3a, there is a J extending from the upper side of the bead core 7 toward the sidewall.
A bead apex 6 having an IS hardness of 65° to 95° is arranged. This bead apex, together with the folded parts 2a and 3a of the carcass, reinforces the tire side part, and its upper end height Hl is 65% of the tread end height H.
% to 110% and the upper end height H1 of the folded part
Overlay, bead apex height H1 overlay is 0, 0
It is desirable to keep a distance of 5 H to avoid overlapping stress concentration points. In this case, H1>HT or HT>H
It is possible to select any one of the following.

Next, in the present invention, a belt layer can be disposed between the carcass and the trend section. The cords of this belt layer B are arranged at a relatively shallow angle with respect to the tire circumferential center plane, for example, 15
Arranged in the range of 30° to 30°. This configuration of the belt layer suppresses lifting of the tire crown due to centrifugal force during high-speed running, further improving straight-line running stability.

Here, as the cord material for the belt layer, organic fiber cords such as nylon, polyester, rayon, aramid, etc. can be used, but when aramid having a high elastic modulus is used, expandability in the circumferential direction of the tire becomes more effective.

Further, the width of the belt layer is set within a range of 60% to 120% of the tread width (straight line distance between tread edges).

〔Example〕

The lateral rigidity of the rear tire of tire size 130/80V1B was prototyped with the cross-sectional structure shown in Fig. 1 and various specifications shown in Table 1.
High-speed vibration characteristics were measured. Also tire size 120/8
A motorcycle (GPZ900R) equipped with a 0V16 front A tire on the front wheel and an A-D tire on the rear wheel was subjected to actual vehicle running tests on JARI's high-speed circuit, and the results are shown in Table 1. Lying down, high speed durability is internal pressure 2
The measurement was carried out under the conditions of 90 kg/cm and a load of 270 kg.

〔Effect of the invention〕

As mentioned above, the present invention improves the tire's lateral rigidity and circularity by arranging the bead apex with high JIS hardness to the vicinity of both ends of the trend in a tire with a cross-ply structure in which the cord angle is relatively shallow with respect to the tire circumferential center plane. The increased circumferential rigidity improves running stability during cornering, while the thickness of the crown part is less compared to the conventional case of increasing the number of carcass plies, which reduces weight and improves high-speed durability and high speed. Stability is maintained.

[Brief explanation of drawings]

FIG. 1 shows the right half of a sectional view of the tire of the invention. 1--Tire, 2.3--Carcass, 4.5-Belt ply, 6--Bead Apex 7--Bead Core. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Representative Patent Attorney Tadashi Naemura Figure 1

Claims (1)

[Claims] (1) The organic fiber cord is composed of at least two layers of plies arranged at an angle of 15° to 35° with respect to the circumferential center of the tire, and the plies intersect with each other, and both ends are connected to a pair of bead cores. A carcass that has been folded back at
A motorcycle tire characterized by having a bead apex with a hardness of 65° to 95°.