JPH04163207A - Radial tire for motorcycle - Google Patents

Abstract

PURPOSE:To improve rectilinear travel stability and turning performance during high speed travel by forming the belt ply of a belt layer into a folded ply, and providing a band layer extended surpassing the folded part inner end from the tire equator. CONSTITUTION:A belt layer 7 is formed of a first belt ply 11 adjacent to a carcass 6 and a second belt ply 12 disposed outside the first belt ply 11. Complex cords, formed by intertwisting high elastic filament made of an organic fiber and low elastic filament made of an organic fiber, are used for these plies 11, 12. The first belt ply 11 is provided, on both sides of a base part 11A adjacent to the carcass 6, with folded parts 11B folded back toward the tire equator C, enveloping both end parts F, F of the second ply 12 so as to be formed into a folded ply. A band ply 14 provided inside a band layer 9 is formed by spirally winding a small width ply from a specified starting point H1 to an end point H2, approximately parallel to the tire equator C.

Description

[Detailed Description of the Invention] [Field of Industrial Application] □The present invention improves both straight-line stability and turning performance by lowering the rigidity of the tread-shield portion at the central portion and increasing the tread shoulder portion. This invention relates to a radial tire for motorcycles that can be improved.

[Conventional technology]

In recent years, with the expansion of expressway networks, there has been a demand for improved performance for high-speed driving even for motorcycles.

These motorcycle tires have traditionally been designed and manufactured based on radial tires for four-wheeled vehicles, so they are unable to follow the turning characteristics of two-wheeled vehicles, which involve turning by tilting the vehicle body, resulting in poor turning performance. and poor durability. Also, it lacks stability when driving straight.

Conventionally, in high-speed motorcycle tires,
In order to prevent the child from peeling off due to repeated deformation of the tire tread while driving, there is a layer on the outside of the belt layer.
A band layer made of aromatic polyamide is provided to prevent the movement of the belt layer. He was becoming more sexually active.

[Problem to be solved by the invention]

However, when a reinforcing layer is uniformly provided on the outside of the belt layer a as shown in Fig. 8, the rigidity of the tread shoulder area increases and the car runs at an angle when turning. By increasing the cornering power,
Grip and stability are improved when driving on an incline.・
However, the cornering power at the center of the tread also increases at the same time, reducing straight-line stability during high-speed driving. Therefore, for a motorcycle tire capable of running at high speeds, it is preferable to form a tread part with a difference in rigidity between the two parts, and furthermore, in a low-load region where the stress applied to the belt cord is lower when driving straight than when turning. By functioning as a low-elasticity cord with high elongation and as a high-elasticity cord during turns when high response force is applied, it produces low cornering power when going straight and high camber thrust when turning. can be made,
It has been found that it is possible to simultaneously improve straight-line stability and turning performance at high speeds. In addition, it has been found that the occurrence of separation at the ends of the belt layer can be prevented, further improving high-speed running performance.

The present invention is based on the fact that the belt bridle cord forming the belt layer is a composite cord consisting of high elasticity filaments and low elasticity filaments, and that at least one of the plies is formed as a folded bridle, even during high-speed running. The object of the present invention is to provide a radial tire for a two-wheeled motor vehicle that has excellent durability and can improve straight-line running stability during high-speed running and cornering stability when turning.

[Means to solve the problem]

The present invention provides one or more carcass cords made of organic fibers that extend from the tread portion, pass through the sidewall portions, wrap around the bead cores of the bead portions, and are inclined at an angle of 70° to 90° with respect to the tire equator. It consists of a carcass made of carcass plies, a belt layer disposed inside the tread portion and radially outward of the carcass, and a band layer disposed radially outward of this belt layer. a first belt brace disposed adjacent to the first belt brace, and a second belt brace disposed outside the first belt brace, and the first belt brace includes the first belt brace on both sides of a base adjacent to the carcass. A folded ply having a folded part that wraps both ends of the second belt braai and folds back inward is used, and the band layer extends from the tire equator beyond the inner end of the folded part and is substantially parallel to the tire equator. The belt layer and the band layer are a radial tire for motorcycles using a belt bridle or band ply made of a composite cord made by twisting high elastic filaments made of organic fibers and low elastic filaments made of organic fibers. It is.

[Effect]

Since the tread portion is reinforced by the belt layer including the first and second belt plies and the band layer consisting of the band brace, the rigidity of the tread portion can be increased and durability can be improved.

Furthermore, since the first belt ply is a folded bridle that wraps around both ends of the second belt bridle, there is a difference in rigidity in the tread portion such that cornering force is smaller at the tread center portion than at the tread shoulder portion. In addition, the belt cord functions as a low elasticity cord when traveling straight,
It uses a composite cord that can function as a highly elastic cord when turning. Therefore, when driving at high speeds, the running stability when going straight is improved, while when turning when the tread shoulder is in contact with the ground, the running stability is improved both when going straight and when turning by improving both grip and running stability. This increases the speed of driving, making continuous high-speed driving possible on the road or on the circuit. Furthermore, since a band layer made of band plies is provided on the outside of the belt layer, which extends from the tire equator to beyond the inner end of the folded part, it is possible to prevent the end of the belt layer from peeling off due to repeated deformation of the tire during high-speed running. , durability can be further improved.

[Example] - An embodiment of the present invention will be described below based on 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 of the tread portion 3 inward in the tire radial direction, and a bead portion 4 located at the inner end of the sidewall portion 3 in the tire radial direction. The radial motorcycle tire 1 also includes a carcass 6 that passes from the tread portion 2 through the sidewall portion 3 and folds the bead core 5 of the bead portion 4 from the inside to the outside in the axial direction of the tire; It comprises a belt layer 7 disposed inside and radially outward of the carcass 6, and a band layer 9 disposed radially outward of the belt layer 7, and a bead having a triangular cross section on the radially outer side of the bead core 5 of the tire. Launch Apex 10.

The carcass 5 has an angle of 70 to 90 degrees with respect to the tire equator C.
The carcass cord is composed of one or more carcass plies, in this example two carcass plies, each having a radial arrangement of carcass cords inclined at an angle of . The carcass cord is an organic fiber cord such as nylon or polyaramid.

The belt layer 7 includes a first belt ply 11 disposed adjacent to the carcass 6, and a first belt ply 11 disposed adjacent to the carcass 6.
and a second belt ply 12 disposed on the outside of the belt.

The first belt ply 11 and the second belt ply 12 are
Composite cords made by twisting high elasticity filaments made of organic fibers and low elasticity filaments made of organic fibers are arranged side by side at an angle of 15 to 30 degrees with respect to the tire equator C, and the cords as the belt ply 11 are Place them across each other.

Further, the first belt ply 11 has both ends F of the second belt ply 12 on both sides □ of the base 11A adjacent to the carcass 6.
, Wrapping part 1 that wraps around F and turns back toward the tire equator C
1B, and thus the first belt ply 11 is formed as a folded ply.

In addition, in this embodiment, the second belt ply 12 has a distance L1 from the tire equator C of its end portion F to 0 of the tread width TW, which is the distance between the tire axial end edges E1.82 of the tread portion 2. It is set within a range of .35 times or more and 0.45 times or less. Further, the distance L2 between the inner end G, which is the edge of the folded portion 11B of the first belt ply 11 facing the tire equator C, and the end F of the second belt ply 12 is:
In this embodiment, the range is 0.20 times or more and 0.25 times or less of the tread width TW.

By setting the length of the folded portion 11B as described above, the folded portion 11B is positioned inside the tire contact surface during inclined driving.

The band layer 9 uses two band plies 14 and 15, inside and outside. In this embodiment, the inner band ply 14 is formed by winding a strip-shaped and long small and medium braai 20 around the outside of the belt layer 7. In addition, the outer band ply 15 is formed by winding the small braai 20 on the outside of the inner band ply 14 in the same manner as the inner band ply 14.

The small and medium ply 20 is formed by embedding one composite cord 21 or a plurality of composite cords 21 arranged in parallel, two in this embodiment, in a topping rubber 22 as shown in FIG.
A composite cord similar to the belt ply is used.

The inner band ply 14 is arranged on the left side in FIG. It is formed by spirally winding the tire equator C to the right and passing the inner end G of the folded portion 11B on the other edge E2 side, with the end point H2 being approximately parallel to the tire equator C. . In this embodiment, when winding the small and medium plies 20, as shown in FIG. ing.

It is preferable that the overlapping length L3 of the inner band ply 14 with the folded part 11B of the belt layer 7 is 10 mm or more in order to prevent the folded part 11B from shifting.

The outer band ply 15 is spirally wound around the small and medium ply 20 starting from the other edge E2 side, that is, in a spiral opposite to that of the inner band ply 14.

In addition, the outer band ply 15 has a medium dimension larger than that of the inner band ply 14, and both sides of the outer band ply 15 are aligned with the starting point H1 and end point H2 of the inner band ply 14. covered.

Note that the inner band brace 14 and the outer band brace 15 may be formed as a sheet body in which a plurality of band cords arranged in parallel are covered with topping rubber in the same way as the belt ply, instead of the spiral winding of the small and medium braces. good.

In addition, when the small and medium braai 20 are wound in the tire circumferential direction as in this embodiment, no seam is formed in the direction crossing the tire circumferential direction, so the running stability during running is further enhanced and the running speed is increased. It can be further increased.

As shown in FIG. 5(a), the composite cord 21 used for the belt layer and the band layer includes a high elastic filament 30.
．． , . . . and low elastic filaments 31 are twisted together.

The high elastic filament 30 is made of aromatic polyamide fiber, wholly aromatic polyester fiber, polyvinyl alcohol fiber or carbon fiber with a strength of 15 g/d or more, and has an elastic modulus of 1000 kg/mm2, preferably 1500 kg.
Fibers with a high elastic modulus exceeding 1000 to 8000 deniers are used.

Furthermore, as the low elasticity filament 31, nylon fiber,
Polyester fiber or vinylon fiber, etc., with an elastic modulus of 10
00 kg/mm' or less, preferably 7゛00 kg
/mm' or less is used.

Such a high modulus filament 30 can be made by simultaneously underburning one or more of them and twisting one or more low modulus filaments 11 which have been underburnt in the same direction in the opposite direction. The composite cord 21 is formed. In addition, when using a plurality of high modulus filaments 30 and low modulus filaments 31, each filament may be burnt individually, or a plurality of filaments may be burnt together. Further, the composite cord 21 may be made by twisting one high elastic filament 30 and one low elastic filament 31 together, as shown in FIG. 7(a).
It is also possible to form a composite cord 21 by using one cord and a plurality of cords, or by twisting a plurality of cords together.

When a tensile force is applied to such a composite cord 21, as shown in FIG. 5(b), the composite cord 21 is untwisted and elongated.

Also, by elongation, the initial twist pitch P of the composite cord 21
1 increases to pitch P2 due to elongation. As schematically shown in FIGS. 6(a) and 6(b), this elongation causes the high elastic filament 30A', which had a coiled shape in the initial state, to become a straight filament due to a predetermined elongation. It will be 30B. Therefore, from this state, the high modulus of elasticity of the high modulus filament 30 is exhibited.

By winding the high-elastic filament 30 in a spiral shape in advance, the elongation from the spiral state shown in FIG. 6(a) to the straight state shown in FIG. 6(b) is reduced. It is clear that the state shown in FIG. 6(b) can have a low elasticity region with low elongation and a high elasticity region with small elongation when a load is further applied from the state shown in FIG. 6(b). This state forms the inflection point of the elongation-stress curve.

In the composite cord 21, the inflection point (2) is thus set to be located in the range of 2 to 7% of the elongation. The composite cord 21 is a twisted body of high elasticity filaments 30 and low elasticity filaments 31, and therefore, as shown in FIG. 5(b).
As shown in <, 'The high-elasticity filament 30 and the low-elasticity filament 31 have twist even when a load is applied, and therefore the inflection point ■ is as shown in the schematic diagrams in Figures 6(a) and (b). It is not as noticeable as in other cases. Composite code 2
The stress-elongation curve of No. 1 is illustrated in FIG. In the figure, curve a shows the elongation curve of a low modulus filament 31 of 1260 d nylon, and of a high modulus filament 30 made of aromatic polyamide with a curve of 1500 d. Also, a composite cord 21 is made by twisting two of these high elasticity filaments 30 and one low elasticity filament 31.
The case is shown by curve C. It can be seen that the curve C is located between the curve a and the curve A, and the inflection point V is in the range of elongation of 2 to 7%. In addition, in the composite code 21, the inflection point V is the intersection point of the vertical line passing through the intersection X where the tangent S1 that is in contact with the curve in the state of zero elongation and the tangent S2 drawn to the curve C at the break point intersects. Defined.

Moreover, the composite cord 21 has a high elasticity region from the inflection point V to the breaking point, and a low elasticity region from the origin where the elongation is 0 to the inflection point V. The ratio EH/EL of the elastic modulus EH to the elastic modulus E'L in the low elasticity range is set in the range of 2 to 10. Such a composite cord 21 can be made by appropriately selecting the thickness, number, elastic modulus, etc. of the high-elastic filaments, the thickness, number, elastic modulus, etc. of the low-elastic filaments, and adjusting the twisting conditions such as the filament angle. , 7th
As shown in the figure, a composite code 21 that can satisfy the above range
can be formed. It can also be adjusted by selecting the stretching process applied to the composite cord 21, high elastic filament 30, and low elastic filament 31.

In addition, since the inflection point V exists in the range of 7% of the elongation, when the green tire is mounted in a vulcanization mold and the green tire is filled with internal pressure during tire production, the internal pressure causes The band layer 9 swells due to the expansion of the composite cord 21, and by pressing its outer peripheral surface against the inner surface of the mold, the groove shape formed in the mold can be carved in the tread portion 2.

In addition, the bulge caused by internal pressure filling in a raw tire is classified as composite code 2.
1 by elongation in the low elasticity region.

For this reason, the inflection point V is set in the range of elongation of 2 to 7%. In addition, the necessary composite code 21 inside the mold due to internal pressure filling
The elongation is preferably located near the inflection point V. As a result, inflation of the molded tire and expansion of the tire due to centrifugal force acting during high-speed rotation can be suppressed by the high elasticity region as shown in FIG. 8. For this reason,
The ratio of the elastic modulus EH in the high elasticity region to the elastic modulus BL in the low elasticity region,
EH/EL is set to 2-10. When it is less than 2, the above-mentioned suppressing effect is poor, and when it exceeds 10, it is unnecessary from the viewpoint of tire balance.

〔Concrete example〕

Tire size is 170/60R17 and 1.5
Regarding the tire (Example) having the configuration shown in the figure, the first
A prototype was manufactured according to the specifications shown in the table, and its performance was tested. For comparison, a test was also conducted on a belt layer and a band layer having the conventional configuration shown in FIG. 6, and the performance of the two was compared.

The test was conducted under the following conditions.

1) Grip characteristics Attach the sample tire to a motorcycle, and place the motorcycle on a test road at 260 km/h on a straight road.
220 km/h on a curved road with a radius of curvature of 400 m at a speed of
The vehicle was run at a speed of H and evaluated based on the feeling of the test driver. The comparative example is expressed as an index of 100, and the larger the value, the better.

2) High-speed stability when turning During the test described in item 1), the stability when passing through the curved road was evaluated based on the driver's feeling. Comparative example 1
It is indicated by an index of 00, and the larger the value, the better.

3) Belt ply peeling resistance: Apply internal pressure specified by JIS to the sample tire, and use an indoor durability test to apply the internal pressure specified by JIS and a load of 1.5 times the maximum load to the sample tire, and at a speed of 65 km/h. /H
The belt was run on the belt, and the running distance was evaluated based on the running distance until peeling occurred in the belt layer.

4) Using a high-speed durability drum testing machine, we applied the internal pressure and maximum load specified by JIS to the sample tire, and conducted a high-speed durability test using a step speed method in which the initial speed was increased from 200km/H to 10km/H every 20 minutes. The judgment was made based on the speed at which cracks appeared in the tread.

The speeds are shown in Table 1, and the larger the speed value, the better.

As a result of the above test, it was found that the tire of the present invention is most suitable as a tire for large motorcycles of 750 cc or more, and can withstand speeds of 280 km/H to 300 km/H.

(Straight stability at high speeds) Evaluated by feeling on a test course by experienced test riders.

〔Effect of the invention〕

As mentioned above, in the radial tire for motorcycles of the present invention, the belt ply of the belt layer is fold-braided, and since the band layer is provided extending from the tire equator beyond the inner end of the folded part, the structure of the belt layer is The number of overlapping layers in the tread shoulder area is larger than that in the center of the tread area,
Therefore, cornering force is smaller in the center area than in the tread shoulder area. As a result, even when traveling at high speeds, the running stability when traveling straight is improved, and the turning performance is also improved, making it possible to enhance the high-speed running range. Moreover, since the belt layer has the above-mentioned structure, peeling of the belt layer is prevented and durability is improved.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing one embodiment of the present invention, Fig. 2 is an expanded plan view showing the configuration of each fold bly, Fig. 3 is a perspective view illustrating a small 1] ply, and Fig. 4 is a cross-sectional view showing an embodiment of the present invention. 5(a) and 5(b) are front views illustrating the composite cord; FIGS. 6(a) and 6(b) are front views illustrating the elongation of the high-elastic cord; FIG. 7 is a diagram illustrating the elongation characteristics of a composite cord, and FIG. 8 is a diagram illustrating a conventional belt structure. 2...--Dou red part, 3-side wall part, 4-
...-bead part, 5-bead core, 6- carcass, 7----belt layer, 9...band layer, 1
1...-first belt braai, 11A-...-base,
11 B, - folded portion, 12, - 1111 second belt ply, 14.15. ,,,,,bandbrai,
21. - composite code, C, -11--tire equator,
G, - inner end. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Tadashi Naemura Figure 2w, 3rM Figure 4 Figure 5 (Figure 5(a) b) Figure 6(b) Figure 6(a) 2] 303] October 25, 1991 Administrative Director Wataru Fukazawa 3, Relationship with the amendment case Patent applicant address 1-1-4 Tsutsui-cho, Chuo-ku, Kobe City Address of agent: Yodoyou-ku, Osaka City Nishinakajima 4-2-26-5, subject to amendment

Claims (1)

[Claims] 1. From the tread portion, passing through the sidewall portion and turning around the bead core of the bead portion, and 70 degrees with respect to the tire equator.
A carcass consisting of one or more carcass plies having a carcass cord made of organic fibers inclined at an angle of 90 degrees, a belt layer disposed inside the tread portion and radially outward of the carcass, and this belt. a band layer disposed radially outwardly of the plies, the belt layer comprising a first belt ply disposed adjacent to the carcass;
a second belt ply disposed on the outside of the first belt ply, the first belt ply wrapping both ends of the second belt ply on both sides of the base adjacent to the carcass and extending inwardly. A folded ply having a folded part is used, and the band layer extends from the tire equator beyond the inner end of the folded part and is arranged substantially parallel to the tire equator, and the belt layer and the band layer is a radial tire for motorcycles that uses a belt ply or band ply made of a composite cord made by twisting high-modulus filaments made of organic fibers and low-modulus filaments made of organic fibers. 2. The pneumatic tire according to claim 1, wherein the high modulus filament is an organic fiber consisting of an aromatic polyamide fiber, a wholly aromatic polyester fiber, or a polyvinyl alcohol fiber having a strength of 15 g/d or more. 3. The pneumatic tire according to claim 1, wherein the low modulus filament is nylon fiber, polyester fiber, or vinylon fiber. 4. The composite cord is formed by twisting one or more high-elasticity filaments that are underburned and one or more low-elasticity filaments that are underburnt in the same direction in opposite directions. The pneumatic tire according to claim 1. 5. The composite cord has a stress-elongation curve having a low elasticity region from the origin to an inflection point and a high elasticity region exceeding the inflection point, and the inflection point is in the range of 2 to 7% elongation. Claim 1: Yes, and the ratio EH/EL of the elastic modulus EH in the high elasticity region to the elastic modulus EL in the low elasticity region is 2 to 10.
Pneumatic tires listed.