JPS6056602A - Tyre for motorcycle - Google Patents

Abstract

PURPOSE:To increase the generating limit of a standing wave and to reduce rolling resistance, by installing 3 triangular truss-structured brakers, which are disposed at the outer side in a radial direction of a toroidal carcass. CONSTITUTION:A tyre 1 has a tread part 2, a side wall part 3, extending radially internally from both ends thereof, and a bead part 4. The carcass 5 of the tyre is formed by 2 plies, and each of the opposite ends thereof are folded outwardly from the interior around a bead core 6 and ends in the bead part 4 or a side wall part 3. The breaker 7 in the tyre is disposed throughout the almost entire width of the tread part to increase the hoop effect of the tread part. The first ply, the second ply, and the third ply of the breaker 7 mutually form a triangle, and form a triangular truss structure, resulting in further reinforcement of a breaker and in improvement of driving stability.

Description

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

In recent years, as roads have become more paved, vehicles have become faster, and tires for automobiles and wheeled vehicles are also required to have high-speed performance characteristics.

Generally, motorcycles have a cross-ply structure in the carcass, that is, the cord angle of the carcass plies is approximately 306 mm with respect to the circumferential direction.
A slanted angle of .about.606 and mutually intersecting arrangements between the plies are 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 drawbacks 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 conducted various studies on the structure, arrangement, and materials of the carcass reinforcing layer and breaker for the radial structure, which had rarely been tried in the past for motorcycle tires.As a result, the inventor decided to cross-ply the camber thrust. It was discovered that the structure of the tire was improved to the same extent as that of a radial tire, and that it could also exhibit the advantages of a radial tire, such as wear resistance, road surface holding ability, and high-speed running performance, and thus the present invention was achieved.

The present invention has a trend part, a sidewall part extending radially inward from both ends of the trend part, the sidewall part, and a bead part located at the radially inner end of the sidewall part. A toroidal carcass made of a nylon fiber cord extending approximately parallel to the radial direction, both ends of which are folded back around a bead core, and a breaker made of three plies arranged on the outside of this carcass in the radial direction, This motorcycle tire is characterized in that the three ply cords are all nylon fiber cords and mutually form a triangular trust structure.

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 (W t ) is usually configured in a cross-sectional shape exceeding the maximum width (Ws) of the sidewall portion, 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 part (6) to form the bead part (4) or the sidewall part. (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 covering the inside folded end and reducing stress concentration at the end. Relaxation is desirable. Furthermore, in order to reinforce the sidewall part, the respective heights H from the bead base part of the inner folded part (5b) and the outer folded part (5a) are increased.
b) (Ha) is 55 to 65% and 70 to 10 of the height H) from the bead base at the maximum width position of the sidewall part.
It is desirable to set it in the range of 0%. 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. . The carcass is made of nylon fiber cords with a density of 35 to 60 in the range of 1000 to 2000 denier, and 30 at a burial density of /5 am.
Plies embedded parallel to rubber with a 0% modulus of 80 to 230 kg/cI11 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 first bridle cord of the breaker is at an angle of 55° to 75° with respect to the tire circumferential direction, the second bridle cord is at an angle of 10° to 30", and the third ply cord is at an angle opposite to the second ply cord. The first ply, the second ply, and the third ply mutually form a triangle to form a triangular trust structure. Making the breaker into such a structure This further strengthens the breaker and improves handling stability.Also, since nylon is used for the braai cord, its rigidity is similar to that of a carcass cord made of nylon, so stress concentration at one end of the breaker can be alleviated. .

In addition, the second and third plies are at an angle of 10° in the tire circumferential direction.
The cords are arranged at an angle of ~30°, but if the cord angle is too small, the tread rigidity increases and the impact against stones scattered on the road surface or unevenness of the road is large, impeding running stability and ride comfort. If it is too large, it will impede steering stability during high-speed driving.

The breaker (7) is composed of three plies, and the width of at least one ply is substantially the same as the arc width of the tread (WT). Nylon 1a fiber cord is used as the same as the fiber cord.For example, the number of ends is 35 to 55 in the range of 1000 denier to 2000 denier, and the 300% modulus is 1oo to 2 at a buried density of 15 cm.
It is preferable to bury it parallel to 40 kg/crl rubber.

Furthermore, in the present invention, a hard rubber apex (9) extending from the bead core (6) with a gradually decreasing thickness in the direction of the sidewall is disposed in a portion surrounded by the carcass and its folded end, thereby making the bead part It is possible to strengthen the lateral rigidity from the sidewall to the sidewall direction. This bead apex (9) preferably extends to a position where it overlaps both ends of the breaker, and its JIS hardness is in the range of 65° to 95°.

Next, in the present invention, as shown in FIG. 2, on the outside of the carcass in the radial direction, fiber cords are reinforced, which extend from one bead portion to the other bead portion, and whose both ends are terminated without being folded back around the bead core. A layer (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, 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 ends (
It is desirable to have a configuration that overlaps 5a) and 5b to alleviate stress concentration in these regions. The fiber cords used for the reinforcing layer are nylon, polyester, rayon,
Cords made of organic fibers such as aromatic polyamide or 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 ends (5a>(5b)), but a structure in which the bead apex (9) is interposed between the inside of the bead apex (9) and the carcass ply can be similarly adopted.

However, since the motorcycle tire of the present invention employs a radial structure in the carcass and has a breaker with a triangular trust structure, the high-speed durability, which is an inherent characteristic of the radial structure, that is, the critical speed at which standing waves can occur, is further increased. At the same time, the transfer resistance is reduced, and since the fiber cords of the breaker and carcass are made of nylon, peeling of the ply at one end of the breaker can be prevented. In addition, the breaker, carcass folds, and reinforcing layers are arranged in a specific structure, which strengthens lateral rigidity, which is a drawback peculiar to radial-structure tires, and increases camber thrust, making stable cornering possible. This phenomenon can also be effectively prevented.

Example As an example of the present invention, a tire size of 140 was used for a structure shown in FIG. 1 and a partially modified structure.
/8 (I made a trial tire for the rear wheel of 1-18.

Further, as a comparative example, a cross-ply structure and a conventional radial structure were used. These detailed specifications are shown in Table 1. In Table 1, the camber thrust for the cross-ply structure tire (Comparative Example 3) is shown as a relative value as OO. The higher the number, the better. Also, the speed at which standing waves occur is from 170km/h to 10km/h,
The speed was increased at intervals of 30 minutes, and the speed at which standing waves were generated was visually observed.

To determine the speed at which vibrations naturally occur at high speeds, the speed was increased on a high-speed road surface, and the speed at which vibrations occurred was evaluated by feeling.

High-speed durability was determined based on the tire high-speed performance B method of the JATMA automobile tire safety standards (quality standards for motorcycle tires). In other words, from a speed of 170km, increase the speed by IOkm steps every 10 minutes, and after 20 minutes at 200km/h, increase the speed by 1Qkm steps every 20 minutes, causing tread damage (separation of carcass and tread rubber, etc.) The speed at which this occurs was measured. The following performance evaluations were conducted using a Honda MJ4 vehicle, with 120/80V16 cross-ply tires mounted on the front wheels and tires listed in Table 1 on the rear wheels.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are partial cross-sectional views of the motorcycle tire of the present invention. 1 Tire 6 Beat core 2 Tread part 7 Breaker 3 Side wall part 8 Reinforcement layer 4 Bead part 9 Beat knee 5 Carcass Spex 10 Band 1 Figure 1 Figure 2

Claims (2)

[Claims] (1) A tire 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, with respect to the radial direction of the tire. A toroidal carcass made of nylon fiber cords extending almost parallel to each other, both ends of which are folded back around the bead core, and a breaker made of three plies arranged on the outside of this carcass in the radial direction. A motorcycle tire characterized in that the cords are all nylon fiber cords forming a triangular trust structure with each other. (2) The tire according to claim 1, wherein the cord angle of the first braai of the breaker is arranged at an angle of 55° to 75° with respect to the tire circumferential direction.