JPH05246209A - Radial tires for motorcycles - Google Patents

Abstract

(57) [Summary] [Purpose] To improve high-speed turning performance and durability while maintaining high-speed straightness. [Structure] The belt layer 7 is formed by a single ply piece 7a in which a belt-shaped cord made of organic fiber is covered with a topping rubber and a long strip-shaped ply is spirally wound at a small angle with respect to the tire equator. In addition, the rubber hardness of the bead apex 8 is 40 to 58 degrees in Shore A hardness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire for a motorcycle capable of improving running stability and durability in high-speed turns while maintaining running stability in straight running at high speed.

[0002]

2. Description of the Related Art In a tire for a motorcycle, since the vehicle body travels with a large inclination during turning, it is necessary to maintain running stability even during this turning, and a structure in which the lateral rigidity of the tire is large is provided. That is, a tire having a cross ply structure has been widely used. However, in recent years, as the highway network has been enhanced and the performance of the vehicle body has been improved, it has been demanded to improve the performance of motorcycle tires even at high speeds.

In response to such a demand for higher speed, tires having a radial structure have been developed even for motorcycles.
This radial tire for a motorcycle is formed, for example, by a ply piece obtained by spirally winding a narrow belt-shaped ply adjacent to the outside of a carcass as the entire belt layer as proposed by the applicant in Japanese Patent Application No. 2-103305. Since it is formed, the bending rigidity in the radial direction is low and therefore the ground contact property is high, so that the running stability is improved. Also, the envelope characteristic is good, and the riding comfort is improved.

Further, since the cords of the plies are continuous in the circumferential direction as compared with the conventional structure formed by joining cut plies, the belt layer has a high hoop effect and the tire outer diameter changes due to centrifugal force. Can be effectively prevented, and the traveling performance is improved when traveling straight ahead, especially at high speeds.

However, the belt layer formed by spirally winding the belt-shaped ply is inferior in lateral rigidity due to the flexibility of the belt layer when turning while tilting the vehicle body, and the camber thrust and the cornering force are both small, Since the high side force required during turning cannot be induced, there is a problem of poor turning performance.

In order to supplement the lateral rigidity, Japanese Patent Application No. 2-1
In No. 17937, the applicant proposed a method of increasing the tip height of the winding portion of the carcass, a method of increasing the tip height of the bead apex, and the like.

[0007]

However, although the lateral rigidity of the sidewall portion is increased by the above proposal, both sides of the tire become too hard and the vertical spring constant becomes high. In addition, the balance of the vertical spring constant and the horizontal spring constant is lost, so that the feeling of ground contact is insufficient during turning and the riding comfort is reduced.
There is a problem that the tire weight increases.

In addition, when the vehicle runs at high speed, it reacts sensitively to the unevenness of the road surface, which causes vibration of the vehicle body induced from the road surface, that is, a weave phenomenon, which is a factor inhibiting speeding up.

As a result of various investigations to solve the above-mentioned problems, the inventor has determined that the hardness of the bead apex is not the conventional one, rather than the height regulation of the bead apex and the height regulation of the winding portion of the carcass. It was possible to confirm by experiments that it is lower than that of the above-mentioned ones and it is effective to regulate the range.

An object of the present invention is to provide a radial tire for a motorcycle capable of enhancing the feeling of stability and improving the durability at the time of turning at a high speed while maintaining the running stability and the riding comfort at the time of going straight at a high speed.

[0011]

The present invention has a main body portion extending from an arc-shaped tread portion to a bead portion through a sidewall portion, and a winding portion that is connected to the main body portion and is folded back around a bead core of the bead portion. And a carcass using one or more carcass plies in which the carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire equator, and a belt layer arranged inside the tread portion and outside in the radial direction of the carcass, The bead apex extends radially outward from the outer end of the bead core in the radial direction between the carcass main body and the winding portion, and the distance between both ends of the tread portion in the tire axial direction is automatically set to the maximum width of the tire. A radial tire for a motorcycle, wherein the belt layer has an elastic modulus of 600 kg.
/ Mm ² or more belt cords made of organic fibers covered with topping rubber, formed by one or more ply pieces with small width and long strip ply spirally wound at an angle almost parallel to the tire equator In addition, the bead apex is a radial tire for a motorcycle, which is made of rubber having a Shore A hardness of 40 degrees or more and 58 degrees or less.

[0012]

Since the belt layer is composed of ply pieces formed by spirally winding a belt-shaped ply in which a belt cord is embedded in topping rubber, the tread portion is different from that of a conventional cross belt formed by using cut plies. In addition to softening the rigidity toward the inside in the radial direction to improve the grounding property and grip, there is no seam in the direction that inclines to the tire equator like the conventional belt layer with cut plies spliced straight and turning. It is possible to improve the stability of maneuvering in.

Further, the bead apex uses a rubber whose hardness is 40 degrees or more and 58 degrees or less of Shore A hardness. In the conventional bead apex, it is common to use a hard rubber having a Shore A hardness of 60 degrees or more in order to increase the vertical spring constant of the tire and prevent the sidewall from breaking at the time of turning. When such a hard rubber is used, the vertical spring constant of the tire becomes high, the riding comfort in straight running is impaired, and the camber angle is 30 to 4
On the other hand, the camber thrust is reduced when the vehicle travels at the maximum inclination angle of 5 degrees, and the overall traveling stability is reduced. By setting the Shore A hardness in the range of 40 to 58 degrees, preferably 48 to 54 degrees as in the configuration of the present application, the generation of camber thrust is stable and the riding comfort is improved in both straight traveling and turning traveling such as turning. The driving stability can be almost balanced.

Here, the vertical spring constant means that when the tire is mounted on a rim and a predetermined inner pressure is applied to the tire inner cavity, a load is applied to the tire to bend the tire and the lateral spring constant. And the correlation with the vertical deflection, and the tangent slope of the actual load in the deflection curve.

The hardness of the bead apex is Shore A.
If the temperature is less than 40 degrees, the molding workability will decrease and
The rigidity of the bead portion is reduced, and hip breakage is likely to occur during traveling, especially during turning traveling, resulting in poor traveling stability. On the other hand, if it exceeds 58 degrees, the spring constant increases and the riding comfort deteriorates. Further, the vibration of the vehicle body becomes large and the running stability becomes unstable.

As described above, in the motorcycle tire of the present invention, the above-mentioned components are organically combined and integrated so that the running stability during straight running is maintained while the running stability during turning is maintained. It can be improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 3, in the tire 1 for a motorcycle, a tread width TW, which is a distance in the tire axial direction between the edges E of the tread portion 2, has a maximum tire width, and a tread surface 2A.
Is formed as a tire for a motorcycle having an arc shape centered on the tire equator C, and includes a tread portion 2, sidewall portions 3 and 3 extending inward from the both ends of the tread portion 2, and the sidewall portion. 3 has a pair of bead portions 4 and 4 located at the inner end in the tire radial direction. Further, the motorcycle tire 1 has a winding portion in which a bead core 5 of the bead portion 4 is folded back from the inner side in the tire axial direction to the main body portion 6a extending from the tread portion 2 to the bead portion 4 through the sidewall portion 3. The carcass 6 includes a carcass 6b and a belt layer 7 disposed inside the tread portion 2 and outside the carcass 6 in the radial direction. Further, in the bead portion 4, a bead apex 8 is provided on the outer side in the tire radial direction of the bead core 5 and between the main body portion 6a of the carcass 6 and the folded portion 6b.
Start up.

In this embodiment, a filler 9 is provided between the carcass 6 of the tread portion 2 and the belt layer 7 and near the outer edge F of the belt layer.

In the present embodiment, the carcass 6 comprises at least one carcass ply having a radial array of carcass cords inclined at an angle of 70 to 90 degrees with respect to the tire equator C. In the present embodiment, one carcass ply is used. As the carcass cord, an organic fiber cord having an elastic modulus of 600 kgf / mm ² or more, such as nylon, polyester, or aromatic polyamide fiber, is preferably used. In the present embodiment, the carcass 6 has a hoisting height Hb, which is the height of the hoisting portion 6b from the bead base line BL, at the edge E of the tread portion 2.
Is set to 0.3 to 0.8 times the tread edge height Hs which is the distance from the bead base line BL.

In this embodiment, the belt layer 7 has a length BS between outer edges of the belt layer in the tire meridian section of 0.8 times or more the length L between the tread edges E along the tread surface 2A and 0. It is set within the range of 9 times or less.

The belt layer 7 is a narrow and long strip-shaped ply 1.
It consists of a ply piece 8 formed by spirally winding 0. As shown in FIG. 2, the belt-shaped ply 10 includes one belt cord 11 or two belt cords 11 arranged in parallel, and in this embodiment, two belt cords 11 are embedded in a topping rubber 12. The belt cord 11 is made of nylon, In addition to organic fiber cords such as polyester and aromatic polyamide, cords having an elastic modulus of 600 kgf / mm ² or more such as steel cords are used. As the belt cord 11, the aromatic polyamide fiber having tensile strength and elastic modulus substantially equal to that of steel and having a weight smaller than that of steel can be preferably used.

The belt-shaped ply 10 extends from left to right in FIG. 1 and the tire equator C from a starting point H1 which is an outer edge F of the belt layer 7 located near one end edge E of the tread portion 2.
The ply piece 8 can be formed by spirally winding at a small angle of 5 ° or less with respect to the tire equator C until reaching the end point H2 forming the outer edge F of the belt layer 7 in the vicinity of the other end edge E. . In addition, in the present embodiment, when the strip-shaped ply 10 is wound, as shown in FIG.
The band-shaped ply 10 is prevented from loosening. Belt layer 7
It is also possible to form two or more ply pieces 7a having the above-described structure, that is, a plurality of spiral windings of the strip-shaped ply 10 as two or more layers.

Since the carcass 6 has its cords arranged in a radial arrangement, the belt cord of the belt layer 7 cooperates with the cord of the carcass 6 to exert a hoop effect.

The bead apex 8 has a triangular shape tapering outward in the radial direction and has a Shore A hardness of 40.
It is formed in a range of not less than 40 degrees and not more than 58 degrees, preferably 48 to 54 degrees. The bead apex 8 is the height from the bead base line BL to the tip P in this embodiment, and the bead apex height Ha is the tread edge height H.
The length L of the bottom piece is set to be 0.4 to 0.7 times s, and the length L of the bottom piece is 0.4 to 0.7 times the bead bottom surface length B which is the length of the bead bottom surface 4a in the tire axial direction. Set to range.

In the tire meridian section between the belt layer 7 and the carcass 6 and from the outer edge of the tire layer in the tire axial direction, that is, toward the tire equator C, one end of the filler 9 is the long side of the belt layer 7. The distance S extends 0.075 times or more and 0.2 times or less of BS, and gradually decreases inward, while the other end extends along the outer surface of the carcass 6 main body 6a in the sidewall portion 3. And a gap G between the tip of the bead apex 15
Is formed and the thickness is gradually reduced inward in the radial direction.

By providing such a filler 9, the longitudinal spring constant of the tire tends to gradually increase as the camber angle increases, and when the camber angle is inclined at a maximum inclination angle of 30 to 40 degrees, the maximum value is obtained. The camber thrust of can be generated. As a result, the feeling of contact with the ground can be enhanced while maintaining the feeling of rigidity, and the running stability at the time of turning can be improved.

The area of the filler 9 between the belt layer 7 and the carcass 6 is 0.0 of the surface length BS of the belt layer 7.
If it is less than 75 times, the vertical spring constant fluctuates greatly when the camber angle is increased or decreased, so that the feeling of grounding at the time of turning becomes poor and the turning performance deteriorates, while if the range exceeds 0.2 times, the tread portion becomes larger. This is because the tread rigidity is increased even in the central region of 2, and as a result, the traveling stability and the riding comfort are deteriorated when the vehicle travels straight ahead, which is inferior in ground contact.

Further, in the filler 9, the thickness t on the normal line N passing through the outer edge F of the belt layer 7 is 0.05 to 0.5 times the rubber thickness T on the normal line N. The thickness t of the filler 9
However, if it is less than 0.05 times the rubber thickness T, the rubber of the filler 9 is thin and the touch feeling is inferior, while if it exceeds 0.5 times, the rigidity in the tread shoulder region becomes excessive and the riding comfort deteriorates. is there.

Moreover, the thickness of the filler 9 is gradually reduced inward, whereby the rigidity step of the tread portion 2 can be alleviated and the running stability at the time of turning can be further improved.

The filler 9 has a rubber hardness of 50 to 90 degrees of Shore A hardness, and is used as a tread rubber 16 forming the surface 2A of the tread portion 2 and a sidewall rubber 17 forming the side wall surface of the side wall portion 3. The hardness of rubber is set to be higher than that.

If the rubber hardness of the filler 9 is less than 50 degrees in Shore A hardness, the tread shoulder region is inferior in rigidity, and as a result, the feeling of rigidity during turning is deteriorated, the running stability during turning is deteriorated, and the durability is deteriorated. On the other hand, if it exceeds 90 degrees, the workability of the rubber composition is deteriorated, and the rigidity of the tread shoulder region becomes excessive, so that the running stability in straight running and turning running deteriorates.

[0032]

SPECIFIC EXAMPLE A tire having a tire size of 190 / 50R17 and having the configuration of FIG. 1 was prototyped according to the specifications shown in Table 1 (Examples 1 to 3) and its performance was tested. For comparison, a tire having a conventional structure without a filler (Comparative Examples 1 and 2) and a tire comparative example (3, 4) having a structure other than the structure of the present application were also tested to compare their performances.

The test conditions are as follows. 1) High-speed straight running stability, high-speed turning stability A trial tire was mounted on a motorcycle, and the automobile was run at 260 km / Hr on a test road, and evaluated according to the feeling of a test driver. It is displayed with the index. The larger the value, the better.

2) High-speed endurance test A trial tire with an internal pressure of 3.00 kgf / mm ² and a load of 355 kg was started at an initial speed of 250 km / hr and
A high speed endurance test was carried out by a step speed method in which the speed was increased by 10 km / hr every 0 minutes, and the judgment was made by the running distance until cracks occurred in the tread portion and the bead portion. In Table 1, the index is shown with the comparative example being 100. The larger the value, the better.

3) Camber Thrust Using a maneuverability tester, the tire internal pressure was 3.00 kgf / mm ² ,
The load was 355 kg and the camber angles were measured at 10 ° and 40 °, respectively, and indicated by an index with Comparative Example 1 being 100. The larger the value, the better. The test results are shown in Table 1.

4) Maneuverability It was judged based on the driver's feeling by running in an actual vehicle and displayed as an index with Comparative Example 1 as 100. The larger the value, the better.

[0037]

[Table 1]

[0038]

As described above, in the motorcycle tire of the present invention, the belt layer is spirally wound with the belt-shaped ply, and the hardness of the bead apex rubber is 40 to 5 in Shore A hardness.
Since the gist is to be within the range of 8 degrees, it is possible to improve straight running stability and improve durability while maintaining straight running stability during high speed running.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing an example of a strip ply.

FIG. 3 is a cross-sectional view illustrating the winding of the band-shaped ply.

[Explanation of symbols]

 2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 6a main body part 6b winding part 7 belt layer 8 bead apex 10 belt-shaped ply 11 belt cord 12 topping rubber C tire equator

Claims (1)

[Claims] 1. A carcass cord with respect to a tire equator having a main body portion extending from an arc-shaped tread portion through a sidewall portion to a bead portion, and a winding portion continuous with the main body portion and folded around a bead core of the bead portion. A carcass using one or more carcass plies arranged at an angle of 70 to 90 degrees, a belt layer arranged inside the tread portion and radially outside the carcass, and from a radial outer end of the bead core. A radial tire for a motorcycle, which comprises a bead apex extending radially outward between a carcass main body portion and a winding portion and having a maximum width of the tire as a distance between the tire axial ends of the tread portion, the belt layer capacitor small width of the elastic modulus was coated with topping rubber a belt cord made of 600 kg / mm ² or more organic fibers, an elongate strip ply And forming the one or more plies piece wound helically inclined in substantially parallel angle relative to Ya equator, the bead apex has a Shore A hardness 4
A radial tire for a motorcycle, which is made of a rubber of 0 degrees or more and 58 degrees or less.