JP3471863B2 - Pneumatic radial tire for motorcycles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire for a two-wheeled vehicle having excellent straight running stability and durability. [0002] In a pneumatic radial tire for a two-wheeled vehicle, at least one carcass crown is formed by spirally winding a ply in which a plurality of cords are covered with rubber and formed into a belt shape. Tires with improved straight running stability have been developed by reinforcing with belt layers. [0003] Usually, an organic fiber such as polyamide is used for the cord constituting the belt layer. Therefore, a tire having this type of belt layer has a belt ply made up of two steel cords. Compared with the conventional belt structure laminated in an intersecting manner, the tread surface is not sufficiently suppressed due to the centrifugal force generated by high-speed rotation, and tread chunks (tread baldness), tread blows, etc. at high speeds As a result, the problem remains where the high-speed performance is inferior. On the other hand, Japanese Patent Laid-Open No. 4-362402 discloses N ×
There is disclosed a tire for a two-wheeled vehicle in which a steel cord having an M structure is applied to a belt layer that spirally winds the belt-like ply. In this tire, by applying a steel cord to the belt layer, it is possible to suppress the protrusion of the tread surface accompanying high-speed rotation. However, the steel cord, when excessive input is applied to the tire at the time of cornering or the like, particularly when compression input is applied, which is likely to occur in an area outside the vehicle at the time of cornering,
Since it is difficult for the cord to buckle, if it is repeatedly input, the cord will eventually break, and the durability of the tire will be significantly impaired. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to increase the speed of a tire having a belt layer formed by spirally winding a belt-like ply without sacrificing excellent straight running stability. An object of the present invention is to provide a tire for a two-wheeled vehicle having extremely little tread surface protrusion during rotation and excellent durability. The present invention uses a carcass formed of a ply of a radial arrangement code extending in a toroidal manner between a pair of bead portions as a skeleton, and is provided at least on both sides of the crown portion of the carcass. A pneumatic radial tire for a two-wheeled motor vehicle having a belt layer formed by spirally winding a belt-like ply in which one or a plurality of cords are covered with rubber, the belt layer being a filament made of one organic fiber 5 to which the sheath which consists of 2-5 steel filaments is twisted around the core which consists of 5
When composed of a composite cord with an elongation of 0.3 to 4% under a kg load, the composite cord has a cross section perpendicular to the longitudinal direction of the cord and a circular arc centered on the core filament is used as a gap between the sheath filaments. The central angle to the arc is 72
A pneumatic radial tire for a two-wheeled vehicle, characterized in that it has a large gap of more than 0 ° and has a sheath filament arranged in close proximity along the circumferential surface of the cord. Here, monofilaments or multifilaments can be used as the filaments made of organic fibers. FIG. 1 shows a cross section of a pneumatic radial tire for a motorcycle according to the present invention. In the figure, 1
Is a pair of bead cores, and a carcass 2 made of a ply of a radial arrangement cord extending in a toroidal shape is disposed between the bead cores 1, and further, a belt layer 3 and a tread are disposed outside the crown portion of the carcass 2 in the tire radial direction 4 are arranged in order. The belt layer 3 is formed by winding a belt-like ply 5 in which one or a plurality of cords, in the example shown in FIG. 2, two cords are aligned and covered with rubber, spirally around the crown portion of the carcass 2. It is turned and laminated on the carcass 2 as shown in FIG. The belt layer 3 may be installed on at least a part of the crown portion of the carcass 2 as shown in FIG. 4 (a) or (b), for example, and further, as shown in FIG. It is also possible to arrange two layers on both side regions. Next, a composite cord applied to the belt layer 3 will be described with reference to FIG. In the figure,
Reference numeral 6 denotes a core filament made of organic fibers, and is formed by twisting sheath filaments 7 to 10 having the same diameter around the core filament 6. The sheath filaments 7 to 10 have a center with respect to the arc when the arc of the circle centering on the core filament 6 is a gap between the sheath filaments in any cross section perpendicular to the longitudinal direction of the cord. Angle α is 72
It is important to have a large gap L of more than 0 ° and the remaining gap S to be narrow, that is, to arrange the sheath filaments close to each other along the circumferential surface of the cord.
Is less than the sheath filament diameter d, preferably 1 /
3 or less, more preferably, the gap S is substantially zero, in other words, except between the sheath filaments sandwiching the large gap L,
It is preferable that the sheath filaments are arranged in contact with each other. By arranging the sheath filament according to the above, when the sheath is given a predetermined type,
The phase between each sheath filament is substantially the same,
The cord breakage resistance is improved. Further, as a code used in the present invention,
It is important that the elongation under a 5 kg load is 0.3 to 4%. This is because if the elongation is less than 0.3%, the tire production process becomes difficult due to insufficient expansion of the tire from molding to vulcanization. On the other hand, if the elongation exceeds 4%, This is because it becomes difficult to suppress the protrusion of the tread surface. Adjusting the elongation to the above range can be achieved by controlling the shaping or twisting pitch of the steel filament. The diameter of the core filament is in the range of 1/3 to 2 times the sheath filament diameter, more preferably 1 /
About 2 to 7/4 times is preferable in order to improve the tensile rigidity of the cord and to avoid belt end separation. The filament used for the core and sheath is insufficient in strength if the diameter is less than 0.08 mm, while on the other hand, if it exceeds 0.20 mm, the belt weight increases, so use a filament in the range of 0.08 to 0.20 mm. Is preferred. Next, the twist pitch of the sheath filament is 6.0 mm
If it is less than 28 mm, it is economically disadvantageous. On the other hand, if it exceeds 28 mm, the cord breakage resistance deteriorates, so 9.0 to 24 mm is desirable. In addition, if the cord structure is a 1 + N structure, the cord breakage resistance can be similarly obtained regardless of whether the cord type is a closed type or an open type centering on the core. Here, in manufacturing the composite cord of the present invention, a required amount of mold is given by a preformer, and the three sheath filaments are made substantially in phase with each other, so that the core filament It can be twisted around the core filament, or can be produced by twisting around the core filament by applying a predetermined shaping amount to the three bundle wires with a preformer. Furthermore, the cord can be flattened with a pressing roll or the like to produce an elliptical cord. In the cord applied to the two-wheeled vehicle tire of the present invention, the cross section has a large gap L with a central angle α of 72 ° or more and the remaining gap S is narrowed. The reason why the sheath filaments are arranged in close proximity along the circumferential surface of the cord is as follows. Conventional steel cords of N × M twist structure such as 1 × 4 or 3 × 3 structure, that is, the above-mentioned Japanese Patent Laid-Open No. 4-3624
In the steel cord disclosed in the publication No. 02, when there is a compression bending input, as shown in FIG. 7, a compression buckling phenomenon that occurs at a critical point where there is a large bending deformation is recognized.
In the case of the cord used in the present invention shown in FIG. 7, no buckling phenomenon is observed as shown in FIG. This is because the arrangement of the sheath filaments shown in FIG. 6 makes the phase between the sheath filaments substantially the same. The input can be absorbed without causing buckling, and the deformation of the sheath filament can be followed by a core filament made of organic fibers having a lower elasticity than the steel filament, so that the core filament also does not buckle. It is considered that the buckling phenomenon does not occur because the compression bending input can be absorbed. However, if the central angle α is less than 72 ° or the gap S exceeds 1/3 of the sheath filament diameter d, a buckling phenomenon may occur as in the conventional cord. The upper limit of the central angle α is not particularly limited, and varies depending on the diameter of the core or sheath filament or the arrangement of the sheath filament. Therefore, the central angle α is 72 ° or more under the desired cord structure. What is necessary is just to ensure the large gap | interval which becomes. EXAMPLE Composite cords and steel cords produced according to Tables 1 and 2 were applied to the belt layer of a radial tire for a two-wheeled vehicle of size 170 / 60ZR 17 under the specifications shown in Tables 1 and 2, respectively. Applied. And the internal pressure is 1/2 of the prescribed
After mounting a tire of a suitable size on a motorcycle with a displacement of 750 cc and running for about 5000 km, the tire was disassembled and investigated for the presence of a cord that was broken in the belt layer. Next, a similar tire is filled with a specified internal pressure,
Set this tire on the drum and gradually increase the running speed on the drum, take a picture of the tread tread part at each speed range with a TV camera, measure the amount of protrusion, and approach at each speed range A comprehensive evaluation of the degree of squeeze was made by comparing the amount of squeeze. Also in this case, the result of Comparative Example 3 is shown as an index when the value is 100, and the larger the number, the better the result. Moreover, when manufacturing each tire, the workability, the molding accuracy, etc. in the molding process are mainly evaluated comprehensively and shown as the quality of the manufacturability. Further, it is mounted on the rear wheel of the above-mentioned two-wheeled vehicle, and the driver's grip force in normal driving during turning and driving immediately after overtaking the gap and how to sway the vehicle body due to disturbance in straight driving (straightness) After evaluating the feeling and driving the general road for 3000 km, the amount of wear was calculated by measuring the groove depth of the tread, and each was expressed as an index when the result of Comparative Example 3 was taken as 100. Larger numbers indicate better results. The evaluation results are also shown in Table 1. [Table 1] [Table 2] According to the present invention, the durability against compression deformation applied to the cord is remarkably improved. Therefore, the durability of a motorcycle tire having high straight running stability and high speed performance is remarkably improved. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a tire according to the present invention. FIG. 2 is a perspective view of a belt-like ply. FIG. 3 is an explanatory diagram showing the arrangement of belt layers. FIG. 4 is a cross-sectional view of a tire according to the present invention. FIG. 5 is a cross-sectional view of a tire according to the present invention. FIG. 6 is a cross-sectional view of a steel cord according to the present invention. FIG. 7 is a graph showing the relationship between compressive strain (%) and compressive stress (kgf) of a cord. [Explanation of Symbols] 1 Bead core 2 Carcass 3 Belt layer 4 Tread 5 Strip ply 6 Core filament 7 Sheath filament 8 Sheath filament 9 Sheath filament 10 Sheath filament

Continuation of front page (56) References JP-A-58-194604 (JP, A) JP-A-59-29501 (JP, A) JP-A-6-297905 (JP, A) JP-A 61-180200 (JP , U) Japanese Utility Model Publication 1-70897 (JP, U) Patent 3411615 (JP, B2) International Publication 80/002572 (WO, A1) (58) Fields studied (Int.Cl. ⁷ , DB name) B60C 9 / 00-9/22 D07B 1/06

Claims (1)

(57) [Claims] [Claim 1] A carcass made of a ply of a radial arrangement code extending in a toroidal manner between a pair of bead parts is used as a skeleton, and at least a part of a crown part of the carcass is
A pneumatic radial tire for a two-wheeled motor vehicle having a belt layer formed by spirally winding a belt-like ply in which one or more cords are covered with rubber, the belt layer comprising:
A composite cord formed by twisting a sheath made of 2 to 5 steel filaments around a core made of a filament made of a single organic fiber and having an elongation of 0.3 to 4% under a 5 kg load. Is a cross section perpendicular to the longitudinal direction of the cord, when the arc of a circle centering on the core filament is the gap between the sheath filaments,
A pneumatic radial tire for a two-wheeled vehicle having a large gap with a central angle with respect to the arc of 72 ° or more, and sheath filaments arranged adjacent to each other along the circumferential surface of the cord.