JP3391695B2 - Motorcycle tires - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motorcycle tire having improved straight running stability and turning maneuverability at high speed running. 2. Description of the Related Art With the recent improvement of the expressway network and the performance of vehicles, a radial structure which is excellent in high-speed running performance even for motorcycle tires has been developed. Is being transitioned. A tire having such a radial structure has a breaker called a belt layer on the outside of a carcass, so that it has high tread bending rigidity and excellent cornering power. On the other hand, it is inferior in flexibility and impairs ride comfort, and the lateral rigidity of the tire is too small with respect to the cornering power, so vibrations called so-called weaves occur in the vehicle body when traveling straight at high speed, and high-speed stability Tends to decrease. For this reason, in recent years, a breaker cord having low elasticity has been used in the breaker, the number of breaker plies has been reduced, or a so-called parallel structure has been adopted in which the breaker cord is spirally wound substantially parallel to the tire equator. It has been proposed to reduce the breaker stiffness itself. [0005] However, the reduction of the breaker stiffness itself improves the straight running stability at high speed running. However, when the vehicle is accelerated while tilting the tire at a deep bank angle like a circuit running, camber thrust and cornering force are reduced. However, there is a problem in that both of them are too small to impair grip performance, and particularly in a large-sized vehicle, a so-called waist phenomenon is caused, thereby impairing turning maneuverability. Accordingly, the present invention provides a method for controlling a predetermined ratio between the thickness of the tread rubber and the rigidity of the tread pattern in the central region where the tire touches the ground in straight running, and the thickness and the rigidity of the tread pattern in the shoulder region where the tire touches the ground when turning. It is an object of the present invention to provide a motorcycle tire capable of improving both high-speed straight-running stability and turning maneuverability, which are contradictory relations. In order to achieve the above object, the present invention provides a carcass extending from a tread portion provided with a tread groove to a bead core of a bead portion through a sidewall portion, and a tread portion. A motorcycle tire having a breaker disposed inside and outside the carcass,
The center which is the ratio of the groove area of the tread groove arranged in the central area C to the area area of the central area C centered on the tire equator having a tread width TW of 20% of the tread width TW between the tread edges. The ratio Sc / of the sea area ratio Sc to the shoulder sea area ratio Ss, which is the ratio of the groove area of the tread groove provided in the shoulder area S to the area of the shoulder area of 20% of the tread width TW from the tread edge. Ss is 1.2 to 2.0, and furthermore, a center rubber thickness Tc from the breaker to the tread surface at the tire equator and a shoulder point separated from the tread edge along the tread surface by a distance of 10% of the tread width TW. Ratio Tc / Ts to the shoulder rubber thickness Ts from the breaker to the tread surface at
Is 1.2 to 2.0. Further, the invention according to claim 1 is characterized in that the maximum groove depth Dc of the tread grooves arranged in the central area C is:
The ratio Dc / Ds between the maximum groove depth Ds of the tread grooves disposed in the shoulder region S and 1.2 to 2.0, before
The straight running stability and turning maneuverability are improved . An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a motorcycle tire 1 (hereinafter referred to as a tire 1) includes a tread portion 2 having a tread surface 2S smoothly curved in an arc shape, and a sidewall portion 3 extending inward in the tire radial direction from both ends thereof.
And a bead portion 4 located at the radially inner end of each sidewall portion 3 in the tire radial direction. The width between the tread edges E1 and E1 is the maximum width of the tire. The tire 1 is a radial tire in this embodiment, and has a carcass 6 bridged between bead portions 4.
And a high-rigidity breaker 7 arranged radially outside of the carcass 6 and inside the tread portion 2. The carcass 6 is provided on both sides of a ply body extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3, and a winding portion for winding the bead core 5 from the inside to the outside in the tire axial direction. The space between the ply body and the winding portion is filled with a bead apex rubber 8 having a triangular cross section and extending outward from the bead core 5 in the tire radial direction. In the present embodiment, the carcass 6 comprises one or more carcass plies 6A in which carcass cords are radially arranged at an angle of 70 to 90 degrees with respect to the tire equator C0, and in this embodiment, one carcass ply 6A. By forming a high turn-up configuration in which the winding portion is raised up to the vicinity of the tread end E1, the tire lateral rigidity is increased together with the bead apex rubber 8. As a carcass cord,
Organic fiber cords such as nylon, rayon, and polyester are preferably used. In the present embodiment, the breaker 7 has at least two breaker cords arranged at an angle of 10 to 30 degrees with respect to the tire equator C0, and in this embodiment, two breaker plies 7A,
7B, and the breaker codes are arranged with different inclinations so as to cross each other between plies. The breaker plies 7A and 7B are formed over substantially the entire area of the tread portion 2 to protect the carcass 6 and reinforce the tread portion 2 with a tag effect. Organic fiber cords such as nylon, rayon, polyester and aromatic polyamide, particularly high modulus aromatic polyamide fiber cords, are suitably used as the breaker cord. As shown in FIG. 2, a tread pattern for providing wet grip is formed in the tread portion 2 by a tread groove 10. In this example, the case where the tread groove 10 is constituted by a vertical groove 11 extending in the tire circumferential direction and a horizontal groove 12 inclined and extending in the tire axial direction is exemplified. Accordingly, various patterns with various tread grooves 10 can be adopted. In this embodiment, the vertical groove 11 has a linear shape or a zigzag shape extending along the tire equator C0. In addition, it is preferable that the horizontal groove 12 is a curve approximating a streamline at the time of drainage. In this example, the angle α is, for example, 40 degrees or less from the inner end point P1 separated from the vertical groove 11 with respect to the circumferential direction. It has a sharply inclined groove portion 12A that is inclined, and a bluntly inclined groove portion 12B that is arranged outside the tire axial direction with an angle β larger than the angle α, for example, 60 to 90. Although the acutely inclined groove portion 12A and the bluntly inclined groove portion 12B are formed in a V-shape with different inclination directions, the inclination direction may be the same direction. The blunt inclined groove 12B may be formed as independent lateral grooves. According to the present invention, in such a tread pattern, in order to reduce the pattern rigidity in the central region C in comparison with the pattern rigidity in the shoulder region S, at least the central sea area ratio Sc in the central region C, The ratio Sc / to the shoulder sea area ratio Ss in the shoulder region S
Ss is regulated in the range of 1.2 to 2.0. In order to further provide a difference in pattern rigidity, the maximum groove depth Dc of the tread grooves 10 arranged in the central region C and the maximum groove depth Dt of the tread grooves 10 arranged in the shoulder region S The ratio Dc / Ds to Ds is regulated in the range of 1.2 to 2.0. Here, the central area C is located on the tread surface 2S.
Of the tread width TW centered on the tire equator C0 and defined as a width area of 20% of the tread width TW. The shoulder region S is a portion of the tread surface 2S that comes into contact with the ground when turning, and is defined as a width region of 20% of the tread width TW from the tread edge E1. The tread width TW is the tread edge E
1, E1 means the length along the tread surface 2S. The central sea area ratio Sc is a ratio Y10c / Yc of a groove area Y10c of the tread groove 10 disposed in the central area C to a region area Yc of the central area C, and is equal to the shoulder sea area ratio Ss. Is the ratio Y10s / Ys of the groove area Y10s of the tread groove 10 arranged in the shoulder region S to the region area Ys of the shoulder region S. As described above, in the central region C, the pattern groove 10 occupies a high proportion and the groove depth D is large, so that the pattern rigidity is reduced such that the pattern groove 10 can be flexibly deformed by an external force from the road surface, and the cornering power is reduced. Is maintained low, so that high-speed straight-line stability is improved. Conversely, in the shoulder region S, the pattern rigidity is kept high, so that there is no shortage of camber thrust and cornering force, and excellent turning maneuverability can be exhibited. The maximum groove depth Dc, D
The reason for employing s is that, in motorcycle tires, a tread pattern is often formed by mixing a plurality of types of pattern grooves 10 having different groove depths, and the groove depth varies even within one groove. This is because it is often done. Therefore, the maximum groove depths Dc and Ds, which have the greatest influence on the pattern rigidity, are regarded as representatives of the groove depth D, and the pattern rigidity is regulated. In this example, the vertical groove 11 has a substantially constant groove depth and is continuous in the circumferential direction.
The groove depth of 1 forms the maximum groove depth Dc in the central region C. In the lateral groove 12, the groove depth decreases stepwise or continuously from the inner end point P1 toward the tire axial direction. For example, a maximum groove depth Ds is formed at a position near the boundary of the shoulder region S. I have. In order to improve the high-speed straight-running stability and the turning maneuverability more effectively and in a well-balanced manner, the tire 1 of the present invention has a rubber thickness of the tread rubber 9 disposed outside the breaker 7. T is different between the central region C and the shoulder region S. More specifically, the center rubber thickness Tc at the tire equator C0 from the breaker 7 to the tread surface 2S
And a ratio Tc / Ts of a shoulder rubber thickness Ts from the breaker 7 to the tread surface 2S at a shoulder point P3 separated from the tread edge E1 by a distance 0.1 TW of 10% of the tread width TW along the tread surface 2S. From 1.2 to
It is regulated to 2.0. In other words, the center rubber thickness Tc on the tire equator C0, which is the center position of the center area C, is
The thickness is increased to 1.2 to 2.0 times the shoulder rubber thickness Ts at the shoulder point P3 which is the center position of the shoulder region S. As a result, elasticity in the central region C is further increased, and high-speed straight-running stability and turning maneuverability can be further improved by synergistic action with the pattern rigidity. It is most preferable that the rubber thickness T of the tread portion 2 is gradually reduced from the tire equator C0 to the shoulder point P3. However, the rubber thickness T is constant throughout the central region C (T = Tc ) And the rubber thickness T is constant (T = Ts) in the entire region of the shoulder region S. In the intermediate region between the central region C and the shoulder region S, the rubber thickness is smoothly reduced from Tc to Ts. You may. Here, the sea area ratio Sc / Ss is 1.2
And when the rubber thickness ratio Tc / Ts is less than 1.2,
In each case, the improvement effect of the present application is not sufficiently achieved. Conversely, when the sea area ratio Sc / Ss is greater than 2.0 and the rubber thickness ratio Tc / Ts is greater than 2.0, high-speed durability, turning property,
And the balance of the abrasion of the shoulder drop is deteriorated. Therefore, it is preferable that the sea area ratio Sc / Ss and the rubber thickness ratio Tc / Ts are each in the range of 1.3 to 1.6. Further, in order to further enhance the improvement effect,
Preferably, the groove depth ratio Dc / Ds is in the range of 1.2 to 2.0. When the groove depth ratio is less than 1.2, the improvement effect is reduced. Decreases the balance between turning and abrasion. Therefore, the groove depth ratio D
c / Ds is also preferably in the range of 1.3 to 1.6. The structure of the tread portion 2 in the present application is as follows.
Similar excellent effects can be exerted on a tire having a bias structure in addition to a tire having a radial structure as in this example. In the case of a tire having such a bias structure, the carcass 6 is connected with the carcass cord by 2
At least two carcass plies arranged at an angle of 5 to 60 degrees, for example, two carcass plies, and as a breaker 7,
The breaker cords are formed by two or more, for example, two breaker plies arranged at the same angle of 20 to 60 degrees as the carcass 6. EXAMPLE The tire size satisfying the specifications shown in Table 1 is 120.
/ 70R17 (for front wheels), 170 / 60R17 (for rear wheels) radial tire, and tire size of 110 /
70-17 (for front wheels), 140 / 70-17 (for rear wheels)
The bias tires were manufactured as prototypes, and the high-speed straight running stability and turning maneuverability of each test tire were tested. The results are shown in Table 1. In the test, the test tire was mounted on the front wheel and the rear wheel of the motorcycle under the conditions of the rim and the internal pressure shown in Table 2, the vehicle was driven on a dry circuit course at a substantially limit speed, and the sensory evaluation was performed by a driver. , Straight running stability and maneuverability during acceleration turning were determined by a five-point method. The higher the number, the better. [Table 1] [Table 2] As shown in Table 1, Examples A1, A2 and B
It was confirmed that the tires Nos. 1 and B2 both improved high-speed straight-running stability and turning maneuverability. As described above, according to the present invention, the tread rubber thickness and the tread pattern rigidity in the central region where the vehicle touches the ground in straight running, and the tread rubber thickness and tread pattern in the shoulder region where the vehicle touches the ground during turning. Since a difference is provided between the rigidity and the rigidity at a predetermined ratio, it is possible to improve both high-speed straight-running stability and turning maneuverability, which are in opposite relations.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a tire showing one embodiment of the present invention. FIG. 2 is a developed view showing the tread pattern. FIGS. 3A and 3B are cross-sectional views showing the depth of a tread groove. [Description of Signs] 2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 7 Breaker 10 Tread groove E1 Tread edge 2S Tread surface C0 Tire equator

Claims (1)

(1) A carcass extending from a tread portion provided with a tread groove to a bead core of a bead portion through a sidewall portion, and a carcass disposed inside the tread portion and outside the carcass. A motorcycle tire having a breaker and a center area C centered on a tire equator having a tread width TW of 20% of a length along a tread surface between tread edges. The ratio of the center sea area ratio Sc, which is the ratio of the groove area of the tread groove provided, to the groove area of the tread groove provided in the shoulder region S with respect to the region area of the shoulder region having a tread width TW of 20% from the tread edge. The ratio Sc / Ss to the shoulder sea area ratio Ss, which is the ratio, is 1.2 to 2.0, and the center rubber thickness Tc from the breaker to the tread surface at the tire equator, Tread width TW 10
% Of the shoulder rubber thickness Ts from the breaker to the tread surface at a shoulder point separated from the tread edge along the tread surface by a distance of 1.2% to 2.0%.
And the maximum groove depth of the tread grooves arranged in the central area C.
Dc and the tread groove arranged in the shoulder region S.
The ratio Dc / Ds to the maximum groove depth Ds is 1.2 to
2.0 for a motorcycle tire.