JPH05213005A - Radial tire for motorcycle - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the maneuverability during turning, to improve the steering stability when going straight, and to improve the convergence of vibration. [Construction] Carcass 6 using a carcass cord made of wholly aromatic polyester fiber having a tensile elastic modulus of 100 to 300 g / d and a twisting coefficient of 1900 to 3100 and a tensile elastic modulus of 8
By including the belt layer 7 using a belt cord made of an aromatic polyamide fiber having a twist coefficient of 0 to 280 g / d and a twist coefficient of 1900 to 3100, it is possible to easily balance the vehicle body weight and the camber thrust at the time of turning, and It is possible to improve running stability, steering stability when going straight, and convergence of vibration.

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, which is excellent in high-speed durability and can improve steering stability, especially kinetic performance when traveling in an inclined state.

[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 appeared even in motorcycles. However, since this radial tire for motorcycles was designed and manufactured based on the radial tires for four-wheeled vehicles, it was impossible to follow the turning peculiar to two-wheeled vehicles in which the vehicle body is tilted and turned. That is, since the lateral rigidity of the carcass is inferior to that of a tire with a cross-ply structure, the force that supports the vehicle body when turning is peculiar to a motorcycle is insufficient.
Further, since the belt rigidity is high, there is a problem that the camber thrust becomes small and the turning performance deteriorates.

In a tire used for a motorcycle for high speed running, nylon fiber is used for a carcass cord of a carcass to balance the camber thrust and the vehicle body weight during turning.

[0005]

However, the displacement is 250
For medium- and large-sized vehicles that exceed cc, the conventional one that uses nylon or polyester fiber cords as a carcass cord has a low tensile modulus of elasticity and the cord itself is inferior in strength. There is a problem that the lateral rigidity required during traveling is poor, the camber thrust cannot be maintained high, and the steering stability, especially the turning performance, and the durability are poor.

In addition, it has been proposed to increase the number of carcass plies or to add a reinforcing layer to the sidewall portion in order to increase the strength and the lateral rigidity of the tire. 244603, JP 58-20503, U.S. Pat. No. 4,263,955, JP 59-20707 and JP 63-305007.
In each of the above items, a cord reinforcing layer or a rubber reinforcing layer is added from the side wall portion or the tread portion to the side wall portion.Thus, the lateral rigidity can be increased, of course, but neither increase the tire weight. It is difficult to do so, and the running resistance of the tire increases as the material cost and tire weight increase, and therefore the fuel efficiency of the vehicle decreases.

On the other hand, when an aromatic polyamide fiber known as a high-strength organic fiber is used as a carcass cord, the required carcass strength can be obtained, but the flex fatigue resistance is poor, and when the tire is repeatedly deformed, It is not suitable for use as a carcass cord because it causes breakage damage to the carcass cord.

The inventor of the present invention further examined the characteristics of various organic fiber cords, and as a result, by using wholly aromatic polyester fibers having a high modulus, it is possible to improve the flex resistance and fatigue and improve the durability of the carcass. ,
The strength of the carcass is increased, and it is possible to support a heavy vehicle body, even for medium and large motorcycles. In addition, it produces high camber thrust and stabilizes maneuvering while tilting, such as when turning. It was found that it could improve the sex.

The present invention is based on the use of a wholly aromatic polyester fiber for the carcass cord and a belt ply using the aromatic polyamide fiber for the belt cord of the belt layer, and improves the kinetic performance during turning. Along with improving steering stability when going straight,
An object of the present invention is to provide a radial tire for a motorcycle, which has excellent vibration convergence and durability and can be suitably used even in a medium-sized or large-sized motorcycle.

[0010]

The present invention comprises an organic fiber which is folded from the tread portion through the sidewall portion around the bead core of the bead portion and is inclined at an angle of 70 ° to 90 ° with respect to the tire equator. A carcass comprising one or more carcass plies with a carcass cord, and a belt layer consisting of one or more belt plies arranged inside the tread and radially outside the carcass and having a belt cord. A radial tire for a motorcycle, wherein the carcass cord has a tensile elastic modulus of 100 g /
d or more and 300 g / d or less, carcass cord 10 cm
The twisting coefficient WT which is the product N√D of the number of twists N per length and the square root of the total number of Denieres D of the carcass cord
1 is formed using a wholly aromatic polyester fiber cord of 1900 or more and 3100 or less, while the belt ply has a tensile elastic modulus of 80 g / d or more and 280 g / d or less, a twist number n of the belt cord and the belt cord. A radial tire for a motorcycle, characterized in that it is formed by using an aromatic polyamide fiber cord having a twist coefficient WT2, which is a product n√d of the square root of the total Denier's number d, of 1900 or more and 3100 or less.

[0011]

In the radial tire for a motorcycle constructed as described above, a wholly aromatic polyester fiber cord having specified characteristic values is used as a carcass cord as described above.

The wholly aromatic polyester fiber is a rigid, high-performance organic compound having a molecular structure shown in Chemical formula 1, for example, in which an aromatic compound having a benzene ring and a ring in which a plurality of benzene rings are condensed is ester-bonded (--O--CO). It is a fiber and is known as a so-called polyarylate fiber.

[0013]

[Chemical 1]

[0014]

[Table 1]

[0015]

[Table 2]

As shown in Table 1, this fiber has a high tensile strength, a tensile elastic modulus and a low breaking strength which are almost the same as those of aromatic polyamide fiber known as other high performance organic fiber, so-called para-aramid fiber (PPTA). Elongation, and therefore, sufficient carcass strength can be maintained without increasing the number of carcass plies. Also, this product has flexural fatigue resistance, that is, the tenacity retention rate when a flexing test with a flexing angle of 130 degrees and a flexing number of 10,000 times was performed on 1500 d / 1, 80 t / m short fibers is shown in Table 2. The wholly aromatic polyamide fiber is 51%, while the wholly aromatic polyester fiber is 9%.
It is extremely large at 7%. Therefore, fatigue of the carcass cord can be prevented when the tire is repeatedly deformed, and the carcass durability can be improved and the service life thereof can be improved.

Since the carcass layer of the tire acts as a pressure vessel of the tire and plays an important role in maintaining the strength of the tire, a cord having a high strength is required, while a tire having a large bank angle is inclined and turned. It is conceivable that if the deformation is large, the maneuverability will be significantly reduced, and in order to prevent this, the tire needs high lateral rigidity. For this reason also, the tensile elastic modulus of the cord forming the carcass is 100 g / d to 3
The range is set to 00 g / d.

When the pressure is less than 100 g / d, the lateral rigidity as a pressure container is deteriorated by filling the internal pressure, and the tire deformation is increased, so that the maneuverability of the tire is deteriorated. Again 3
If it exceeds 00 g / d, the riding comfort is poor when driving straight ahead.

The twisting coefficient WTI of the carcass cord is regulated in order to impart elongation to the carcass cord and suppress compression fracture of the cord at the time of filling with internal pressure.
If the twist coefficient is less than 1900, the elongation is small, and the compression fracture suppressing effect is insufficient. On the other hand, if it exceeds 3100, the elongation is excessive, the tire rigidity is impaired, the running performance is deteriorated, and the carcass cord is difficult to manufacture. ..

Moreover, the wholly aromatic polyester fiber is shown in FIG.
As shown in FIG. 4, by providing a vibration damping property and a shock absorbing property which are superior to those of other tire cord materials, the damping performance of the vehicle body vibration is changed and the shock from the road surface is absorbed and eased to improve the riding comfort. The wandering property can be improved.

By using such a novel wholly aromatic polyester fiber cord as a carcass cord,
It not only increases tire lateral rigidity without significantly increasing tire weight and durability, but also facilitates vehicle body weight and camber thrust even during leaning, which is a driving mode peculiar to motorcycles such as when turning. Can be balanced. Therefore, it can be suitably used even in a large motorcycle having a heavy vehicle body and equipped with a powerful engine.

Further, the belt cord has a tensile elastic modulus of 8
0 g / d to 280 g / d, twist coefficient WT2 is 1900 to
3100 aromatic polyamide fiber cords are used.
Since the aromatic polyamide fiber has high tensile strength and tensile elastic modulus as described above, the belt layer can sufficiently increase the rigidity of the belt layer against the radial outward force of the tread portion in cooperation with the carcass having the above configuration. As a result, the lifting of the tread portion can be suppressed even with a high centrifugal force due to high speed running, and a high level of durability performance is exhibited.

On the other hand, with respect to the pushing force of the tread portion to the inner side in the radial direction, the rigidity of the belt layer becomes sufficiently small, and the tire exhibits high envelope characteristics and the riding comfort can be improved. In addition, a wide ground contact area can be secured when traveling straight ahead and when turning, so that excellent traveling stability can be provided.

When PPTA (high modulus) shown in Table 1 is used as the aromatic polyamide fiber, the tensile elastic modulus is remarkably increased, and the grip property and running stability at the time of turning are remarkably improved and the turning performance is further improved. You can do it.

As described above, according to the present application, the structure of the carcass described above is organically integrated with the structure of the belt layer, so that the vehicle body is heavy and a powerful engine is installed.
Even when used in large motorcycles, it improves running stability when turning and steering stability when going straight,
Moreover, the durability can be improved.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the figure, a radial tire 1 for a motorcycle includes a tread portion 2, a sidewall portion 3 extending from both ends thereof toward a tire radial direction inner side, and a bead portion 4 located at an inner end of the sidewall portion 3 in the tire radial direction. In addition, the radial tire 1 for a motorcycle has a bead core 5 of a bead portion 4 passing through the tread portion 2 through the sidewall portion 3.
A carcass 6 which is folded back from the inner side in the tire axial direction to the outer side, and a belt layer 7 arranged inside the tread portion 2 and on the outer side in the radial direction of the carcass 6, and also on the outer side in the tire radial direction of the bead core 5. Start up the bead apex 10 having a triangular cross section. In this embodiment, the band layer 9 is arranged on the outer side in the radial direction of the belt layer 7.

The carcass 6 is composed of at least one carcass ply 6A, 6B having two or more radial carcass cords inclined at an angle of 85 to 90 degrees with respect to the tire equator C, and two carcass plies 6A, 6B in this embodiment. As described above, the carcass cord is an organic fiber cord made of wholly aromatic polyester fiber having a tensile elastic modulus of 100 to 300 g / d and a twisting coefficient WT1 of 1900 to 3100.

The carcass plies 6A and 6B are formed as a sheet body by topping a carcass cord made of the above-mentioned wholly aromatic polyester fibers and arranged in parallel with a topping rubber. In this embodiment, the modulus of the topping rubber is set in the range of 60 to 90 kg / cm ² . If the modulus is less than 60 kg / cm ² , the highly elastic performance of the cord due to the use of the wholly aromatic polyester fiber as the carcass cord is not utilized, and the carcass 6 is easily deformed, resulting in poor lateral rigidity. On the other hand, if it exceeds 90 kg / cm ² , the rigidity becomes excessive and the ride quality may deteriorate.

The belt layer 7 includes a first belt ply 11 arranged adjacent to the carcass 6 in this embodiment,
It comprises a second belt ply 12 arranged outside the first belt ply 11.

The first belt ply 11 and the second belt ply 12 each have an organic fiber cord made of the aromatic polyamide fiber having a tensile elastic modulus of 80 to 280 g / d and a twisting coefficient WT2 of 1900 to 3100, and a tire equator C. Against 1
Belt ply 1 is installed in parallel at an angle of 0 to 30 degrees.
The cords 1 and 12 are arranged so as to intersect each other.

The belt layer in the radial tire has a role like a hoop that accelerates the carcass. Therefore, it is preferable to arrange the belt cords at an angle in the range of 10 ° to 30 ° with respect to the tire equator so that the arrangement angle can be easily exerted. Further, in order to suppress the deformation of the ground contact surface of the tread portion, in addition to the belt cord having the above-mentioned structure, it is preferable to use a rubber having a high elastic modulus as a topping rubber for topping the belt cord. With this configuration, the wear resistance of the tread rubber is improved and the rolling resistance of the tire is also reduced, so that the fuel efficiency is improved. Furthermore, by using an aromatic polyamide fiber cord that has a smaller specific gravity than steel (0.185 times that of steel), the weight of the tire is reduced, which contributes to the reduction of fuel consumption of the tire and the centrifugal force of the tire causes the tire to rotate at a high speed. Since it is reduced, the lifting of the belt layer is suppressed and the durability of the tire is improved.

In this embodiment, the first belt ply 11 is wrapped around both ends F, F of the second belt ply 12 on both sides of the base 11A adjacent to the carcass 6 and folded back toward the tire equator C. It has a folding part 11B, and thus the first part
The belt ply 11 is formed as a fold ply.

When the belt layer 7 is formed as a folded ply as in the present embodiment, the belt ply ends are not exposed at both edges of the belt layer 7, and therefore the belt ply can be prevented from peeling off. The durability of the tread portion 2 can be improved.

The band layer 9 uses two band plies 14 and 15 inside and outside. In this embodiment, the inner band ply 14 is a belt-shaped long elongate narrow ply 20.
It is formed by winding it on the outside of. The outer band ply 15 is formed by winding the narrow width ply 20 on the outer side of the inner band ply 14 and similarly to the inner band ply 14.

As shown in FIG. 5, the narrow ply 20 comprises one band cord 21 or two band cords 21 arranged in parallel, and in this embodiment, two band cords 21 are embedded in a topping rubber 22. As with the belt ply, a highly elastic cord such as aromatic polyamide fiber is used.

In the inner band ply 14, the small width ply 20 having the above-described structure is set to have a starting point H1 on the peripheral surface of the folded portion 11B which extends beyond the inner end G of the folded portion 11B on one end edge E1 side from the tire equator C. In FIG. 1, the inner end G of the folded portion 11B on the other end edge E2 side beyond the tire equator C from left to right.
It is formed by spirally winding the point that exceeds the end point H2 and substantially parallel to the tire equator C. In this embodiment, when winding the narrow ply 20, as shown in FIG.
The side edges 20a, 20a of the small width ply 20 facing each other are wrapped around each other and wound to prevent the small width ply 20 from loosening.

The outer band ply 15 is spirally wound by using the narrow ply 20 and starting from the other edge E2 side by a spiral opposite to that of the inner band ply 14. Further, the outer band ply 15 has a width dimension larger than that of the inner band ply 14, and the outer band ply 1
Both sides of 5 are the starting point H1 and the ending point H of the inner band ply 14.
Covers 2.

When the band layer 9 is formed by winding the narrow width ply 20 in the tire circumferential direction as in the present embodiment, a seam in a direction intersecting with the tire circumferential direction does not occur, so that running stability during running is ensured. And the traveling speed can be further increased.

In the present invention, the belt layer 7 may be formed by stacking two belt plies 11 and 12 each composed of two cut plies using aromatic polyamide fibers as shown in FIG. Further, the carcass ply may be formed as a jointless structure by winding a narrow width ply 20 like the band ply of the band layer 9 shown in FIGS. 5 and 6, and the present invention can be modified into various modes. ..

[0040]

SPECIFIC EXAMPLE A tire having a tire size of 170 / 60R17 was prototyped according to the specifications shown in Table 3 (Examples 1 to 3) and its performance was tested. For comparison, the tires (Comparative Examples 1 to 3) in which the cords of the carcass and the belt layer were made of conventional fibers were also tested to compare their performances. The test results are shown in Table 3. The test was conducted under the following conditions.

[0041]

[Table 3]

1) Steering stability (straight and turning) and riding comfort A trained test rider runs on a test course,
It was judged by feeling, and Comparative Example 1 was 10
It was evaluated by an index of 0. The larger the value, the better. During the test, the tires shown in Table 3 were attached to the rear wheels, and the 120 / 70R17 cross-ply tires were attached to the front wheels.

2) High speed durability Initial speed of 150 km using a 60 inch diameter drum tester
Starting from / H, the speed was increased by 10 km / H every 10 minutes, the speed at which the standing wave was generated was measured by visual observation, and the comparative example 1 was displayed as an index of 100. The higher the value, the higher the speed at which the standing wave occurs and the better.

3) Rolling resistance Using an indoor drum tester with an outer diameter of 1.7 m, a tire internal pressure of 2.8 kgf / cm ² and a peripheral speed of 80 km / H,
The resistance value was measured in three stages of 100 km / H and 150 km / H, and the average value thereof is represented by an index with Comparative Example 1 being 100. The larger the value, the better.

[0045]

As described above, in the radial tire for a motorcycle according to the present invention, the carcass cord is formed by using the wholly aromatic polyester fiber, so that the vehicle body weight and the camber thrust are easily balanced even when the vehicle is running on a slope. In addition, it is possible to improve the running stability at the time of turning together with the use of the aromatic polyamide fiber for the belt cord, and to improve the steering stability when going straight, the convergence of vibration, and the durability. It can be suitably used for medium and large-sized motorcycles.

[Brief description of drawings]

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

FIG. 2 is a developed plan view showing an example of the configurations of the carcass and the belt layer.

FIG. 3 is a diagram showing vibration damping properties of wholly aromatic polyester fibers.

FIG. 4 is a diagram showing the impact absorption of wholly aromatic polyester fibers.

FIG. 5 is a perspective view illustrating a narrow ply.

FIG. 6 is a cross-sectional view showing the winding.

FIG. 7 is a cross-sectional view schematically showing another configuration of the carcass and the belt layer.

[Explanation of symbols]

 2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 6A, 6B carcass ply 7 belt layer 11, 12 belt ply

[Table 3]

[Table 3]

Claims (1)

[Claims] 1. A carcass cord comprising an organic fiber which is folded from a tread portion through a sidewall portion and around a bead core of a bead portion and is inclined at an angle of 70 ° to 90 ° with respect to the tire equator. A carcass consisting of a carcass ply of No. 1 and a belt cord arranged inside the tread portion and radially outside the carcass 1
A radial tire for a motorcycle, comprising a belt layer composed of one or more belt plies, wherein the carcass cord has a tensile modulus of 100 g / d or more and 300 g / d or less, and the number of twists per 10 cm length of the carcass cord. The twist coefficient WT1, which is the product N√D of N and the square root of the total Denier number D of the carcass cord, is 1900 or more and 31
On the other hand, the belt ply has a tensile modulus of 80 g.
/ D or more and 280 g / d or less, an aromatic polyamide fiber cord having a twist coefficient WT2 of 1900 or more and 3100 or less, which is a product n√d of a twist number n of the belt cord and a square root of a total Denier number d of the belt cord. A radial tire for a motorcycle, which is formed by using.