JPS6050005A - Tire for motorcycle - Google Patents

Abstract

PURPOSE:To improve the durability under high speed operating conditions by forming the outer ply of the breaker wider than the inner ply. CONSTITUTION:The breaker 7 which is disposed across the entire tread section 2 comprises inner and outer plies 7a, 7b, and the width of the outer second ply 7b is so arranged that it is wider than the inner first ply 7a and the outer second ply 7b spans across the entire tread section 2. In this instance, the first ply 7a is made narrower than the second ply 7b so that the step S may be less than 20mm.. In this manner, the reinforcement effect for the tread section 2 is ensured, and the durability under high speed operating conditions can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motorcycle tire, and particularly to a radial motorcycle tire that has excellent durability during high-speed running.

Recently, as road networks and pavements have improved, vehicles have become faster and faster, and tires for motorcycles are also required to have better performance during high-speed driving.

In general, motorcycles have a cross-ply structure in the carcass, that is, the cord angle of the carcass plies is approximately 30 degrees with respect to the circumferential direction.
A mutually intersecting arrangement between the plies, inclined at an angle of between 60° and 60°, is widely used.

This is due to the fact that motorcycle tires are fundamentally different from tires for passenger cars and other four-wheeled vehicles in terms of their dynamic function, especially when turning. When the tires are made thick (inclined (gives a large camber angle)), a force (camber thrust) is generated in the tire horizontally to the road surface in the direction of the camber angle, counteracting the centrifugal force acting on the car body and stabilizing it. Motorcycle tires are therefore required to have the characteristics of maintaining a smooth running performance.Therefore, motorcycle tires use a carcass with the above-mentioned cross-ply structure to increase lateral rigidity and maintain the camber thrust. Radial structures are rarely adopted due to the above reasons. However, tires with cross-ply structures suffer from lateral vibrations (WEAVE phenomenon) of the vehicle body caused by the tire's cornering power and lateral rigidity when driving at high speeds, and wear resistance. However, measures have been taken to increase tire rigidity, such as lowering the cord angle of the carcass relative to the circumferential direction and increasing the number of carcass plies, but adopting a cross-ply structure However, the drawbacks due to its structure cannot be completely eliminated.

Therefore, the inventor conducted various studies on the structure, arrangement, and materials of the carcass reinforcing layer, bead apex, and breaker for the radial structure, which had rarely been tried in the past for motorcycle tires.As a result, the camber thrust The wear resistance has been improved to the same level as tires with cross-ply structure, and the wear resistance, which is an advantage of radial tires, has been improved.
It has been found that it can exhibit good road holding properties and high-speed running performance.

However, this type of radial structure tire inevitably requires a breaker to be placed in the tire crown, but in this case, the crown part of a motorcycle tire has a carcass profile with a large curvature in its cross section. As a result, the deformation strain at both ends of the breaker during running becomes dirty, resulting in separation from the carcass at both ends of the breaker or damage between the breaker plies. In particular, the breaker ply has a wide first ply adjacent to the carcass and a narrow second ply outside of the first ply. In this case, at both ends of the second ply, Damage occurs between the first plies and breaks in the cords of the first ply occur in the circumferential direction of the tire. An object of the present invention is to solve this problem and provide a motorcycle that has excellent durability during high-speed running.

The present invention includes a tread portion, a sidewall portion extending radially inward from both ends of the tread portion, the sidewall portion, a bead portion located at the radially inner end portion of the sidewall portion, and a sidewall portion extending in the radial direction of the tire. A toroidal carcass consisting of cords extending almost parallel to the tire, with both ends folded back around the bead core, and a plurality of cords arranged radially outward of the carcass and having a cord angle at a shallow angle with respect to the circumferential direction of the tire. A motorcycle tire is provided with a breaker made of plies, and the breaker is characterized in that the outer ply is wider than the inner ply.

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

FIG. 1 shows a partial sectional view of the motorcycle tire of the present invention. In the figure, the tire (1) of the present invention has a tread portion (2).
), a sidewall portion (3) extending radially inward from both ends thereof, and a bead portion (4) located at the radially inner end of the sidewall portion. Here, the tread portion (2) extends on the crown of the carcass approximately parallel to its contour from the center of the crown toward both ends,
The straight line width (Wt) is usually the maximum width of the sidewall part (W
s), thereby maintaining camber thrust when the tire is tilted.

Next, the carcass (5) of the tire of the present invention is composed of two plies, both ends of which are folded back from the inside to the outside around the bead core (6) to form the bead portion (4) or sidewall portion. (3) terminates. Here, the folded end (5a) located on the outside of the bead portion extends to a higher position than the folded end (5b) located on the inside of the bead portion, completely covers the inner folded end, and reduces the stress at the end. It is desirable to reduce concentration. Furthermore, in order to reinforce the sidewall part, the respective heights of the inner folded part (5b) and the outer folded part (5a) from the bead pace part (Hb) (Ha) are the heights of the bead base at the maximum width position of the sidewall part. It is desirable to set the height in the range of 55 to 65% and 70 to 100% of the height H).

The cords of the carcass are then arranged parallel or substantially parallel to the radial direction of the tire. Here, "almost parallel" means that the cords are inclined at an angle of 10 degrees or less in the radial direction, and if a configuration exceeding 10' is adopted, the excellent high-speed running characteristics that are characteristic of radial tires will be reduced. do not have. The fibers used for the carcass cord are organic fibers such as nylon, polyester, rayon, or aromatic polyamide fibers. In the present invention, one or more carcass plies are used, but the folding structure around the bead core (6) can be folded from the inside to the outside as shown in the figure, or folded from the outside to the inside, or a combination of both. However, the figure shows a structure folded from the inside to the outside as an optimal example.

Next, the breaker (7) in the tire of the present invention is arranged with a width that spans almost the entire width of the tread portion, thereby increasing the effectiveness of the tread portion. Here, the breaker (7) has a first briar (7a) arranged adjacent to the carcass and a second briar (7a) that is wider than the first briar (7a) on the outside of the first briar.
Ply (7b) is arranged. 2nd ply (7
b) is arranged with a width spanning almost the entire width of the tread portion, and the first
The braai (7a) has a step (S) width of 20 mm or less, preferably 3 to 10 mm+, than the second ply (7b).
It consists of a step width of

If the width of the step exceeds 20 mm, the width of the first braai will become too narrow and the reinforcing effect of the tread part will not be sufficient. On the other hand, if the width of the step is 0, there will be a large difference in rigidity at the end of the breaker.
Peeling of the ply between the carcass and the carcass is likely to occur.

In this way, the present invention reduces the width of the first braai, which is subject to severe fatigue due to running, and protects it entirely by covering it with a highly rigid second ply, thereby effectively reducing the possibility of cord breakage of the first braai. At the same time, separation of the carcass and ply at both ends of the breaker can be prevented.

The ply cord of the breaker should be at an angle of 10° to 45° with respect to the tire circumferential direction, preferably 20° to 35°.
placed at an angle of °. If the cord angle is too small, the trend stiffness will be increased and the impact will be large against stones scattered on the road surface or unevenness of the road surface, which will impede running stability and ride comfort.On the other hand, if the cord angle is too large, the steering stability during high speed driving will be affected. inhibit.

Note that the breaker (7) is usually composed of two plies, and the width of at least one ply is formed to be substantially the same as the tread width (Wt).

The m-fiber cord used for the breaker is rayon,
Materials such as polyesteropenylon and steel cord can be used, but in particular aromatic polyamide fiber cord with a strength of 7 g/d or more and an initial modulus of 200 g
, /d or more, and the twist coefficient (NT) shown by the following formula is 0.
A range of 36 to 0.60, preferably 0.44 to 0.55 is suitable.

NT=NX-kun〒Ding "Running Fu X + 0-3 NT: Twisting coefficient N: Number of twists / 10 cm D: 1/2 ρ of cord torque denier: Cord specific gravity Also, the above breaker cord has a 300% modulus. 1
It is preferable to embed them parallel to the rubber of 00 to 240 kg/cnf at a density of 30 to 65 pieces/5 cm.

Next, in the present invention, as shown in FIG. 2, on the outside of the carcass in the radial direction, there is a reinforcing layer of fiber cords extending from one bead part to the other bead part, and both ends of which are terminated without being folded back around the bead core. (8) can be placed. The reinforcing layer (8) intersects the carcass cord at a certain angle and has the function of reinforcing the sidewall section, but in order to improve cornering characteristics without impeding ride comfort, the longitudinal springs of the sidewall section are It is necessary to increase the lateral spring constant without increasing the constant, and therefore it is necessary to arrange the cord angle at 45° to 85°, preferably 60° to 80° with respect to the circumferential direction. Further, both ends of the reinforcing layer are connected to the folded end (5) of the carcass at the bead part.
a) It is desirable to have a structure that overlaps with (5b) to alleviate stress concentration in this region. The woven fiber cord used for the reinforcing layer is nylon, polyester perrayon,
In addition to cords made of organic fibers such as aromatic polyamide, steel cords can also be used.

Note that the reinforcing layer (8) is made of bead apex (9), which will be described later.
), as shown in Figure 8, the bead apex (9
) and the folded ends (5a) (5b), but it is also possible to adopt a structure in which the bead apex (9) is interposed between the inside of the bead apex (9) and the carcass ply. .

Furthermore, in the present invention, by arranging a bead apex (9) made of hard rubber that extends from the bead core (6) with a gradually decreasing thickness in the direction of the sidewall in the carcass and its folded end or in the part surrounded by the cord reinforcing layer. , it is possible to strengthen the lateral rigidity from the bead portion to the sidewall direction.

The bead apex (9) preferably has an upper end extending close to the maximum width of the sidewall, and has a JIS hardness of 6.
The angle ranges from 5° to 95°.

However, since the motorcycle tire of the present invention employs a radial structure for the carcass and the first and second plies of the breaker are arranged as described above, the tire has excellent high-speed durability, which is an inherent characteristic of the radial structure. The wave generation limit speed is increased and the rolling resistance is kept low, and the problems of cord breakage of the first ply and peeling of the ply at both ends of the breaker can be solved. In addition, because the bead apex and reinforcing layer are arranged in a specific configuration, the lateral rigidity, which is a drawback peculiar to radial structure tires, is strengthened, the camber thrust is increased, and stable cornering is possible. Furthermore, the so-called "bump" phenomenon is also effective. It can be prevented.

EXAMPLE As an example of the present invention, a rear wheel tire with a tire size of 120/90R18 was manufactured as a prototype with the structure shown in FIG. 1 but with a partially modified breaker ply structure. Detailed specifications of the prototype tire are shown in Table 1.

Each tire has an internal pressure of 2. ”25 kg/cm, speed 6
5kg/h.

After traveling 15,000 km on a drum with a load of 230 V3, the tire was disassembled and the strength distribution of the breaker ply cord was measured. An embodiment of the present invention is shown in Fig. 3 (4)-4.
FIG. 3(C) and comparative examples are shown in FIGS. 4(A) to 4(C). In FIG. 4 of the comparative example, the cord strength of the first ply at both end positions of the second ply is significantly reduced.
The first ply and the second ply from FIGS. 3(a) and 3(b) of the present invention
It is observed that the ply cord maintains approximately the same strength in the tread width direction.

Table 1

[Brief explanation of drawings]

Figures 1 and 2 are partial cross-sectional views of the motorcycle tire of the present invention, Figures 3 (A) to 3 (C), and Figures 4 (A) to
FIG. 4(c) is a graph showing the relationship between the strength of the cords of the second ply and the second ply and their tire positions, and 'JSL' is a diagram. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Representative Patent Attorney Yoshihira Nakamura Figure 1 Figure 3 Figure 4 (A)

Claims (3)

[Claims] (1) 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 and substantially parallel to the radial direction of the tire. A breaker consisting of a toroidal carcass consisting of an extending cord, both ends of which are folded back around a bead core, and a plurality of plies disposed radially outward of this carcass, the cord angle being at a shallow angle with respect to the tire circumferential direction. Equipped with
A motorcycle tire, wherein the breaker has an outer ply wider than an inner ply. (2) The tire according to claim 1, wherein the breaker is made of an aromatic polyamide fiber cord. (3) The breaker cord is arranged at an angle of 10° to 45° with respect to the circumferential direction of the tire.
The tire described in Items 1 and 2.