JPS6056604A - Tyre for motorcycle - Google Patents

Abstract

PURPOSE:To improve high speed durability and the generating limit speed of a standing wave and to reduce rolling resistance, by forming a carcass in radial structure and disposing a breaker. CONSTITUTION:A tyre 1 has a tread part 22, a side wall part 3 extending radially inwardly from both ends, and a bead part 4. A carcass 5 of the tyre is formed with 2 plies, and the cords of the carcass are aligned in parallel with each other in a radial direction and are inclined at an angle of 10 deg. or less. A breaker 7 in the tyre is disposed throughout an about entire width of the tread part. The cords of the breaker are disposed at an angle of 5-45 deg. with a peripheral direction, and at least one ply of two plies, with which the breaker is formed, is formed in a width which is substantially the same as a circular width WT of the tread. An annular boundary line A is disposed within the range of 6mm. or less in the direction of the center of the tread or the direction of the side wall along the profile of a tyre cross section centering around a tread end TE.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motorcycle tire, and particularly to a radial tire that easily and reliably suppresses cracks or separations that occur at the joint between a sidewall portion and a tread portion.

Recently, as roads have become more paved, vehicles have become faster, and tires for motorcycles are also required to have better performance during high-speed driving.

Generally, motorcycles have a cross-ply structure in the carcass, that is, the cord angle of the carcass ply is approximately 30° with respect to the circumferential direction.
An arrangement that is angled at an angle of ~60' and crosses each other between the plies is widely employed.

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. At this time, the tire is tilted significantly (gives a large camber angle) to the road surface, and 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, resulting in stable running. The property of maintaining the Therefore, motorcycle tires use a carcass with the above-mentioned cross-ply structure to increase lateral rigidity and maintain the camber thrust, and radial structures with poor lateral rigidity are rarely adopted from the above viewpoint. However, tires with a cross-ply structure have disadvantages in terms of wear resistance and the generation of lateral vibration of the vehicle body (WEAVE phenomenon) due to the tire's cornering power and lateral rigidity when driving at high speeds. Countermeasures have been taken to increase tire rigidity, such as lowering the angle relative to the circumferential direction and increasing the number of carcass plies, but as long as a cross-ply structure is adopted, the defects caused by that structure cannot be completely eliminated. .

Therefore, the inventor of the present invention has conducted various studies on the structure, arrangement, and materials of the carcass reinforcing layer and breaker for the radial structure, which has rarely been tried in the past for motorcycle tires. A new radial structure was proposed as it was found to be improved to the same degree as tires with ply structure, while also exhibiting the advantages of radial tires in terms of wear resistance, road holding performance, and high-speed running performance.

In other words, as shown in FIG. 1, the tire with the radial structure proposed by the inventor as a motorcycle tire has a tread portion (2) and sidewall portions (3) extending radially inward from both ends of the tread portion (2). and the side wall part (3
) and a bead part (4) located at the radially inner end of the sidewall part, the toroid is made of a cord extending approximately parallel to the radial direction of the tire, and both ends of which are folded back around the bead core. shaped carcass 5) and arranged on the radially outer side of this carcass,
A breaker (7) whose cord angle is arranged at a shallow angle with respect to the tire circumferential direction, and a hard rubber bead apex (9) extending from a position adjacent to the bead core toward the sidewall between the carcass and its folded part. This is a motorcycle tire.

The upper end (3a) of the sidewall part (3) is joined to the lower end of the tread part (2a).

Here, the sidewall part uses rubber with a JIS hardness of 45" to 55°, which has excellent bending resistance, and the tread part uses rubber with a JIS hardness of 55" to 85°, which has excellent abrasion resistance and grip properties.
rubber is used. Since the two rubbers are different materials, a structural fault is formed at the joint, and this, combined with repeated deformation strain during tire movement, creates an annular shape where the joint surface intersects with the outer surface of the tire. Boundary line (A
), cracks or jishons may often occur in tires with a radial structure.When the deformation strain of each part of a tire with a radial structure was measured during running, a large amount was found near the joint between the tread and sidewall. It was found that it had undergone deformation strain.

Table 1 The inventor prototyped a radial tire with a tire size of 120/90 R18 and the cross-sectional structure shown in Fig. 12 with the specifications shown in Table 1, and the internal pressure was 2.25 kg/cnf and the load was 435 k.
g/ The strain distribution on the tire surface was measured under the condition of one tire. In Figure 1, the surface position of the tire is 60 degrees from the tread edge.
They are identified by numbering them at mm intervals, and strain changes due to tire transfer are shown as a graph in Figure 2.

In FIG. 2, it can be seen that the strain is highest at the center of the tire's contact with the ground, and moreover, the strain is higher in the area marked ■ from the tread edge (TE). Therefore, the present invention removes the joint between the tread part and the sidewall part from this area.
By locating the area within 5mm from the tread edge (TE) in the tread center direction or the side wall direction along the tire cross-sectional contour, strain at the joint can be reduced and This effectively prevents cracks or separation.

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

FIG. 3 shows a partial sectional view of the motorcycle tire of the present invention. In the figure, the tire of the present invention (1) 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 width (W t ) of the tire is usually configured in a cross-sectional shape that exceeds the maximum width (Ws) of the sidewall 11, thereby maintaining canny 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) and either the bead part (4) or the sidewall part (3). ) terminates in 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,
It is desirable to completely cover the inner folded end to relieve stress concentration at the end. 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 base part (Hb) (Ha) are the bead pace part at the maximum width position of the sidewall part. It is desirable to set the height to a range of 50% to 70% and 70% to 130% 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; if a configuration that exceeds 10 degrees is adopted, the excellent high-speed running characteristics that are characteristic of radial tires will not be obtained. . In addition, the fibers used for the carcass cord are nylon,
Organic fibers such as polyester, rayon or aromatic polyamide fibers are used. 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 cord is carved in the circumferential direction of the tire at an angle of 5° to 45°, preferably 10° to 45°.
placed at an angle of 30°. If the cord angle is too small, the tread rigidity 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 impaired. The right 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 arc width (WT) of the tread. The fiber cord used for the breaker can be the same as the cord material used for the reinforcing layer, but is especially made of aromatic polyamide fiber cord with a strength of 10 g/d or more and an initial modulus of 250.
g/d or more, and the 300% modulus is 1
20~240kg/ca! It is preferable to embed it parallel to the rubber.

Next, in the present invention, the annular boundary line (A) formed by intersecting the upper end of the sidewall part and the outer surface of the tire at the joint part of the tread part is on the trend part surface and extends from the tread edge (TE) to the tread center. It is located in an area within 6 mm in the direction. In addition, if the annular boundary line (A) exceeds 6 mm and is located toward the center of the tread, the annular boundary line (A)
Distortion in the vicinity increases, cracks become more severe, and the disadvantages due to the fact that the rubber of the sidewall portion, which has poor wear resistance, is located on the ground contact surface side cannot be ignored. In addition, the annular boundary line (A) is also placed at the tread edge (T) to reduce distortion.
It is necessary that the position does not exceed mark 6 from E) in the direction of the sidewall section.

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 a portion surrounded by the carcass and its folded end, It is possible to strengthen the lateral rigidity in the direction of the wall.

This bead apex (9) preferably extends to a position where it overlaps both ends of the breaker, and its JIS hardness is 6.
The angle ranges from 5° to 95°.

Next, the present invention provides a reinforcing layer of fiber cords extending from one bead part to the other bead part on the outside of the carcass in the radial direction as shown in FIG. (8) may be arranged. 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, so the cord angle should be set at 45° to 85° with respect to the circumferential direction, preferably 60°.
It is necessary to align at ~80°.

Further, it is desirable that both ends of the reinforcing layer overlap the folded ends (5a) and (5b) of the carcass at the bead portion to alleviate stress concentration in these regions. As the fiber cord used for the reinforcing layer, organic fiber cords such as nylon, polyester, rayon, and aromatic polyamide, and steel cords can also be used.

Note that the reinforcing layer (8) is made of bead apex 9, which will be described later.
), place the bead apex (9) as shown in the figure.
) and the folded end portions (5a) (5b), but a structure in which the bead apex (9) is interposed between the inside and the carcass ply may be similarly adopted.

However, since the motorcycle tire of the present invention adopts a radial structure in the carcass and has a breaker arranged therein, the high-speed durability inherent to the radial structure, that is, the critical speed at which scunting waves occur is increased, and the rolling resistance is improved. becomes smaller. And above the sidewall section,
Since the annular boundary line (A>, which is formed by the intersection of the joint surface of the end and the tread portion with the outer surface of the tire) is placed at a specific position, cracks occurring at this portion can be effectively prevented.

Furthermore, the breaker, carcass folds and reinforcing layers are arranged in a specific structure, which strengthens the lateral rigidity, which is a drawback peculiar to radial structure tires, increases camber thrust, and enables stable cornering. The so-called waist-sagging phenomenon can also be effectively prevented.

[Brief explanation of drawings]

Figure 1 is the left half of a cross-sectional view of a radial tire for motorcycles, Figure 2 is a graph showing strain distribution in each part of the tire, Figure 3 is
FIG. 4 shows the left half of a sectional view of the radial tire for a motorcycle according to the present invention. 1 Tire 6 Beat core 2 Tread portion 7 -・- Breaker 3 Side wall a 8 Reinforcement layer 4 Beat portion 9 Beat knee 5 Carcass Spex 10 Band patent applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent attorney Yoshihira Nakamura, Figure 1, Figure 3 Figure 4

Claims (1)

[Scope of Claims] (1) having 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;
A toroidal carcass consisting of cords that extend almost parallel to the radial direction of the tire, with both ends folded around the bead core, and a cord that is placed outside the carcass in the radial direction and has a shallow angle with respect to the tire circumferential direction. and a hard rubber bead apex (9) extending in the sidewall direction from a position adjacent to the bead core between the carcass and its folded part, and a tread at the upper end of the sidewall part. The annular boundary line (A) formed by the intersection of the joint surface with the tire outer surface is the tread edge (TE
), the tire is located within a range of 5 mm or less in the tread center direction or sidewall direction along the tire cross-sectional contour. (2> The tire according to claim 1, in which the breaker is made of an aromatic polyamide fiber cord. (3) The breaker cord is 5 mm in the circumferential direction of the tire.
A tire according to claims 1 and 2 arranged at an angle of 6 to 45 degrees. (4) A tread portion, a sidewall portion extending radially inward from both ends of the tread portion, and a bead portion located at the radial side end portion of the sidewall portion, with respect to the radial direction of the tire. A toroidal carcass consisting of cords extending almost parallel to each other, both ends of which are folded back around the bead core, and a toroidal carcass that is placed radially outward of this carcass, extending from one bead to the other, and both ends of which are folded back around the bead core. The cord angle is 45° to the circumferential direction of the tire.
A fiber cord reinforcing layer arranged at an angle of 85 degrees, and at least two breakers arranged outside the reinforcing layer so that the cord angle is shallow with respect to the tire circumferential direction, Annular boundary line (A) formed by the intersection of the joint surface with the tread part and the outer surface of the tire
is located within a range of 6 mm or less in the tread center direction or sidewall direction along the cross-sectional contour of the tire around the tread portion (TE). (5) The cord angle of the reinforcing layer is 60' to 8' in the tire circumferential direction.
The tire according to claim 1, which is in the range of 0°.