JPH10181310A - Radial tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the rigidity of a tread-shoulder part minimizing the increase in cornering power, to restrict an occurrence of the amount of a motorcycle preventing a breaking down phenomenon in turning, and to reconcile turning performance and turning stability. SOLUTION: A radial tire is provided with a carcass 6, whose cord angle is 70 to 90 degrees, a band layer 7, which winds the cord spirally and in the circumferential direction of the tire, and a tread reinforcing layer 9, which is arranged either in the space between the band layer 7 and the carcass 7 and at least in the tread-shoulder part Y1 or in the outside in the radial direction of the band layer 7 and at least in the tread-shoulder part Y1. The tread rein-forcing layer 9 consists of a reinforcing ply 9A, in which the reinforcing cord is arranged at an angle of 70 to 90 degrees to the circumferential direction of the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can increase the rigidity of a tread shoulder portion while minimizing an increase in cornering power, and achieves both turning performance and turning stability while maintaining riding comfort when traveling straight. The present invention relates to a radial tire for a motorcycle, which can be increased.

[0002]

2. Description of the Related Art With the improvement of the expressway network and the performance of vehicles in recent years, a shift to a radial structure which is excellent in high-speed running performance is being attempted even for motorcycle tires.

[0003] Such a tire having a radial structure has a strong belt layer on the outside of a radially arranged carcass. In recent years, in order to improve riding comfort in a radial tire, a cord is formed between plies as a belt layer. Japanese Patent Application Laid-Open No. 61-85203 and the like have proposed a type using a parallel code ply in which a low elasticity organic fiber cord is spirally wound in the circumferential direction, instead of the conventional cross cord ply cross-arranged as described above.

The parallel cord ply is provided with flexibility such as a reduced radially inward bending stiffness of the tread portion as compared with the cross cord ply, so that the contact property is improved, and the riding comfort and straight running stability are improved. It is said that it can improve the quality. However, due to the flexibility, the tread stiffness becomes too small during turning, and a so-called stiffness phenomenon particularly occurs during turning in a large vehicle, which tends to impair steering stability.

[0005] Accordingly, Japanese Patent Application Laid-Open No. Hei 3-231003 discloses that the outer side of a belt layer made of the parallel cord ply is provided for the purpose of improving the steering stability during turning while maintaining the riding comfort when traveling straight. Further, it is disclosed that a reinforcing layer in which organic fiber cords are arranged at an angle of 20 to 45 degrees is provided in a tread shoulder portion to appropriately increase the rigidity of the tread shoulder portion.

[0006]

However, in such a structure, although the phenomenon such as the above-mentioned stiffness is improved by the increase in rigidity due to the reinforcing layer, the cornering power at the time of turning is excessively increased, and as a result, the cornering power from the road surface is increased. When a tire is shaken by an external force or the like, a large lateral force is generated, which causes a problem that the stability at the time of turning is deteriorated, such as causing vibration and runout of the vehicle body.

Therefore, the invention according to claim 1 of the present invention is based on increasing the cord angle of the reinforcing cord in the tread reinforcing layer to an angle of 70 to 90 degrees, increasing the rigidity in the tread shoulder portion and increasing the cornering power. Of radial tires for motorcycles that can increase while minimizing power consumption, prevent stiffness during turning, suppress the occurrence of vehicle shake, etc., and improve both turning performance and turning stability It is an object.

A second object of the present invention is to provide a radial tire for a motorcycle, which can achieve the effect of improving the turning performance and the turning stability with a minimum necessary reinforcing ply, and is useful for suppressing an increase in tire weight. And

According to the third aspect of the present invention, it is possible to suppress the disorder of the cord arrangement of the band layer at the time of vulcanization molding, and in addition to the improvement of the turning performance and the turning stability, durability, stability, and turning transient characteristics. It is intended to provide a radial tire for a motorcycle that can improve the tire.

[0010]

In order to achieve the above-mentioned object, according to the present invention, the invention according to the first aspect of the present invention is directed to a method in which a bead portion is turned around a bead core of a bead portion from a tread portion to a side wall portion and a carcass. A carcass in which cords are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction, and a band layer arranged radially outside the carcass and inside the tread portion and spirally winding the band cord in the tire circumferential direction. A motorcycle radial tire comprising at least a tread shoulder portion between the band layer and the carcass, or at least a tread shoulder portion radially outside of the band layer, a reinforcing cord 70 to the tire circumferential direction. It features a tread reinforcement layer consisting of reinforcement plies arranged at an angle of 90 degrees.

[0011] In the invention according to claim 2, the reinforcing ply is
It is characterized by being formed from a pair of shoulder ply pieces arranged only on the tread shoulder portion.

[0012] According to a third aspect of the present invention, a reinforcing ply is provided.
It is characterized by a folded ply that has a folded ply that has a ply main part extending between the band layer and the carcass and a folded part that is folded from the inside to the outside in the radial direction around both ends of the band layer.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a radial tire 1 for a motorcycle (hereinafter referred to as a tire 1) has a tread surface 2.
A tread portion 2 in which S smoothly curves in an arc shape, sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and bead portions 4 located at radially inner ends of the respective sidewall portions 3 in the tire radial direction. With tread ends E1, E
The tread width TW, which is the distance between the tires 1 in the axial direction of the tire, is formed to be the maximum width of the tire.

The tire 1 has a carcass 6 bridged between the bead portions 4, a band layer 7 disposed radially outside the carcass 6 and inside the tread portion 2, and A tread reinforcing layer 9 is provided between the carcass 6 and at least radially outside the tread shoulder portion Y1 or the band layer 7 and interposed at least in the tread shoulder portion Y1. The tread shoulder portion Y1 is a region where the tread portion 2 contacts the ground when turning, and the region where the tread portion 2 contacts the ground when turning straight is referred to as a tread central portion Y2.

The carcass 6 has a folded portion on both sides of a main body portion extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3 to turn around the bead core 5 from inside to outside in the tire axial direction. And a bead apex rubber 8 having a triangular cross section extending from the bead core 5 to the outside in the tire radial direction between the main body portion and the folded portion.
Is filled.

The carcass 6 is composed of one or more carcass plies 6A in which the carcass cords 10 are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction, in this embodiment, one carcass ply 6A. The height H1 from the bead base line of the portion is set to a high turn-up configuration in which the height H2 to the tread end E1 is about 0.6 to 0.9 times, so that the tire lateral rigidity together with the bead apex rubber 8 is provided. Is increasing.

The band layer 7 comprises at least one band ply 7A spirally wound at an angle of 5 degrees or less with respect to the circumferential direction of the tire, in this example, one band ply 7A. In the present example, a strip-shaped and long narrow strip 12 in which one or a plurality of the strips are aligned.
And then spirally wound. This strip piece 1
2 is, for example, two band codes 1 as shown in FIG.
1 is embedded in topping rubber, has a flat rectangular cross-sectional shape, and the distance N from the side surface 12S to the center of the outermost band cord 11 is set to approximately 1/2 of the inter-cord pitch Pi.

The band ply 7A of this embodiment is formed by continuously winding the strip piece 12 from one tread end E1 to the other tread end E1 while the side surfaces 12S are in contact with each other. Using the strip strips 12, the strip strips 12 can be wound from the vicinity of the tire equator C toward the tread ends E1 on both sides or from the tread ends E1 on both sides toward the tire equator C. Further, when winding the strip piece 12, the vicinity of the side surface 12S may be overlapped and wound so as to prevent the cord from being loosened.

The band layer 7 usually reinforces the tread portion 2 by setting the band width BW in the tire axial direction to a range of 0.7 to 1.0 times the tread width TW. In order to reinforce and maintain the tire cross-sectional shape more reliably due to the tag effect, the band width BW is set to the tread width T.
W is preferably 0.8 times or more, and more preferably 0.9 times or more.

The tread reinforcement layer 9 is composed of, for example, one (one layer) reinforcement ply 9A in which the reinforcement cords 13 are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction. In this example, a pair of left and right shoulder ply pieces 1 arranged only on each tread shoulder portion Y1 by being separated from each other on both sides in the tire axial direction.
5 is formed. In addition, each shoulder ply piece 15
In this embodiment, the band layers are provided at symmetrical positions with respect to the tire equator C outside in the radial direction of the band layers 7, but may be arranged between the band layers 7 and the carcass 6 as required.

In such a tread reinforcing layer 9, since the shoulder ply piece 15 has a hollow shape, flexibility is imparted to the tread central portion Y2 by the circumferentially oriented band cord 11, thereby improving ride comfort and comfort. Straight running stability is maintained high.

In the tread shoulder portion Y1 where the shoulder ply piece 15 is interposed, as shown in FIG.
The reinforcing cords 13 are arranged in a lattice pattern together with the band cords 11, thereby increasing the cornering power during turning while minimizing the bending rigidity inward in the radial direction of the tire. In addition to preventing phenomena, it is possible to suppress the occurrence of deflection of the vehicle body due to an external force from the road surface or the like, thereby improving stability during turning.

In order to make the cornering power smaller, it is preferable that the cord angle of the reinforcing cord 13 is 80 degrees or more. Conversely, when the cord angle is less than 70 degrees,
The cornering power becomes excessive and the effect of improving turning stability cannot be exhibited.

Here, in order to surely achieve the effect of improving both the turning performance and the turning stability, the shoulder ply piece 15 must be at least 0.35 times the band width BW of the tire equator. Inner end position P separated from C
It is necessary to interpose a distance of 1 to 0.45 times the band width BW in the area range Y3 from the tire equator C to the outer end position P2. In other words, the distance Ka1 of the inner end of the shoulder ply piece 15 from the tire equator C
Is required to be not more than 0.35 times the bandwidth BW, and in order to further ensure the effect,
0.30 times or less is preferable. On the other hand, from the viewpoint of the ride comfort and the like, the distance Ka1 is 0.20 of the band width BW.
More preferably, it is more preferably 0.25 times or more.

The distance Ka2 of the outer end of the shoulder ply piece 15 from the tire equator C must be at least 0.45 times the band width BW for the above-mentioned reason. Preferably, it is 0.50 times or more, and it is desirable to improve the rigidity together with the band layer 7 up to the limit of the tread end E1 which is the turning limit. It is preferable to prevent damage from the outer end of the shoulder ply piece 15.

As the carcass cord 10, band cord 11, and reinforcing cord 13, organic fiber cords such as nylon, polyester, rayon and aromatic polyamide, steel fiber cords, glass fiber cords and the like can be used. It is preferable to use an organic fiber cord having a property.

FIG. 4 shows another embodiment of the tread reinforcing layer 9. In the figure, the tread reinforcement layer 9 is formed by folding the reinforcement ply 9A, in which the reinforcement cords 13 are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction, into a folded reinforcement ply 17.
Is formed by

The folded-back reinforcing ply 17 has a ply main portion 17A extending between the band layer 7 and the carcass 6.
And a folded portion 17B connected to both ends of the ply main portion 17A and being turned from the inside in the radial direction to the outside around both ends of the band layer 7 and along the outer surface in the radial direction of the band layer 7. Is extraly arranged only on the tread shoulder portion Y1, so that the rigidity of the tread shoulder portion Y1 can be increased as compared with the tread central portion Y2. The cord angle of the reinforcing cord 13 is 70 to 90 degrees, and the ply main portion 17A and the folded portion 1
Since the code crossing angle with 7B is extremely small,
A substantial lattice-like arrangement is formed between the band cord 11 and the cornering power.

The outer diameter of the tire after vulcanization is set to be, for example, about 3 to 5% smaller than the outer diameter of the tire before vulcanization. Circumference)
Also increase. When the circumferential length is increased, the gap between adjacent band cords is disturbed. In particular, in the case of a motorcycle tire in which the band layer 7 is formed by spiral winding of the cords and the curvature of the tread portion is small, the circumferential length is reduced. In order to counter the increase, the band cord tends to move outward in the tire axial direction, so that the band cord interval is increased and the interval is likely to vary.

However, the folded reinforcing ply 1
Since the cord 7 has a cord arrangement substantially perpendicular to the band cord 11, the cord has a large resistance to the movement of the cord, and increases the band cord spacing and the variation in the spacing over the entire width of the band layer 7, thereby improving the uniformity.

In the tire for a motorcycle, if the tread shoulder portion Y1 has a circumferential rigidity step, the vehicle tends to run out due to the force due to the step. However, the folded back reinforcing ply 17 is
In order to completely cover both ends of the band layer 7, the band cord 1
It is possible to prevent the rigidity step caused by the end of the winding start or winding end from changing the circumferential rigidity. In addition, by covering both ends of the band layer 7, cord loosening from the end of the band cord 11 can be prevented. As described above, by improving the uniformity of the band cord 11, preventing the circumferential rigidity step, and preventing the band cord loose, durability, steering stability and turning transient characteristics can be further improved.

In the folded reinforcing ply 17, the distance Kb1 of the inner end of the folded portion 17B from the tire equator C is not more than 0.35 times the band width BW for the same reason as the shoulder ply piece 15. And it is preferably 0.30 times or less.
It is preferably at least 0.20, more preferably at least 0.25 times W. The amount of protrusion Kb3 of the folded reinforcing ply 17 from the outer end of the band layer 7 is preferably 0 to 5 mm in order to prevent damage.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire having the structure shown in FIG.
5R17 tires are prototyped based on the specifications in Table 1, and at the same time, test tires are tested for high-speed durability, turning stability, and turning limit, and the results are shown in Table 1.

<1> As for high-speed durability, a test tire was mounted on a bench drum testing machine using a rim (MT 5.50 × 1).
7) Under the conditions of internal pressure (290 kPa) and load (178 kgf), the speed is increased from 230 km / h to 10 k every 10 minutes.
The speed was increased by m / h, and the speed at the time when the tire was broken was evaluated. In Table 1, "0" means that the tire was damaged at the same speed as Comparative Example 1, and "+2" means that the tire was damaged at a speed 20 km / h higher than Comparative Example 1. Further, in all the damage forms, the tread rubber at the center of the tread was peeled off from the outer surface of the band layer. <2> Regarding the turning stability and turning limit, the test tire was mounted on a rim (MT5.50 × 17) and the internal pressure (250 kP).
Motorcycle under the condition of a) (750cc, 4 cycles)
The vehicle was mounted on the rear wheel, and the vehicle was driven on a dry pavement road.
It was determined by the zero point method.・ Turn stability is a sensory evaluation of vehicle body runout that occurs when a small projection is crossed during a high-speed turn.
The larger the value, the less the deflection is generated and the higher the stability.・ As for the turning limit, the height of the limit speed in high-speed turning was evaluated. The larger the value, the higher the limit speed and the better the turning performance.

As the front wheels, conventional tires shown in Table 2 were used.

[0036]

[Table 1]

[0037]

[Table 2]

As shown in Table 1, in the tire of the example product in which the cord angle of the tread reinforcing layer was 70 to 90 degrees, the rigidity of the tread shoulder portion was increased while the cornering power was kept low. As compared with a tread reinforcing layer having a cord angle of 30 degrees, turning stability can be improved while maintaining other characteristics high. When the reinforcing ply is a folded reinforcing ply, the high-speed durability can be greatly improved.

[0039]

As described above, the tire of the present invention has a tread reinforcing layer having a cord angle of 70 to 90 degrees at least in the tread shoulder portion. Therefore, the rigidity of the tread shoulder portion is increased by increasing the cornering power. Can be increased while minimizing the swing, and the occurrence of the swing of the vehicle body and the like can be suppressed while preventing the phenomenon of the stiffness at the time of turning and both turning performance and turning stability can be improved. Also, when the reinforcing ply is formed of a folded reinforcing ply, the cord arrangement of the band layer at the time of vulcanization molding can be suppressed, and the outer end of the band layer can be covered and protected, so that durability, stability, and Turning transient characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is a perspective view illustrating a strip piece.

FIG. 3 is a development view showing a code arrangement of a carcass, a band layer, and a tread reinforcing layer.

FIG. 4 is a schematic sectional view showing another embodiment of the tread reinforcing layer.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Band layer 9 Tread reinforcement layer 9A Reinforcement ply 10 Carcass cord 11 Band cord 13 Reinforcement cord 15 Shoulder ply piece 17 Folding reinforcement ply 17A Ply main part 17B Folding part Y1 Tread shoulder part

Claims (3)

[Claims] 1. A carcass which is turned around a bead core of a bead portion from a tread portion to a sidewall portion and has carcass cords arranged at an angle of 70 to 90 degrees with respect to a tire circumferential direction, and a radius of the carcass A radial tire for a motorcycle comprising a band layer spirally wound in the tire circumferential direction with a band cord arranged outside the direction and inside the tread portion, at least a tread shoulder portion between the band layer and the carcass, Alternatively, a tread reinforcing layer made of a reinforcing ply in which reinforcing cords are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction is interposed at least in a tread shoulder portion on a radially outer side of the band layer. Radial tire for motorcycles. 2. The tread reinforcing layer includes a reinforcing ply consisting of a pair of shoulder ply pieces arranged only on each tread shoulder portion by being separated from each other on both sides in the axial direction of the tire. Radial tires for motorcycles. 3. The tread reinforcing layer includes a ply main portion extending between the band layer and the carcass, and is connected to both ends of the ply main portion and is turned around from both ends of the band layer from the inside to the outside in the radial direction. The radial tire for a motorcycle according to claim 1 or 2, further comprising a folded reinforcing ply having a folded portion along a radially outer surface of the band layer.