JP2013166526A - Pneumatic radial tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for a motorcycle capable of eliminating a lack of lateral strength caused by a lack of rigidity at a tire side and further eliminating a lack of durability.SOLUTION: This invention relates to a pneumatic radial tire for motorcycle comprising at least one layer of carcass ply 2 folded back around and engaged with around bead cores each of which is buried at a pair of beads, at least one belt ply 3 arranged outside in a tire radial direction of the carcass ply 2, and a tread part 12 arranged outside in a radial direction of the tire of the belt ply 3. There is provided a flipper ply 5 outside the carcass ply 2 that is folded back outside around the bead core 1 from the inside of the tire and the folding-back end of the flipper ply 5 has a terminal end between the carcass ply 2 and the belt ply 3.

Description

  The present invention relates to a pneumatic radial tire for motorcycles (hereinafter, also simply referred to as “tire”), and more particularly, to a pneumatic radial tire for motorcycle mainly intended for use on rough terrain including muddy ground.

  Rough terrain tires are generally used at low internal pressures for the purpose of ensuring grip and grounding on unstable and slippery road surfaces. Therefore, it is used in a state where it is very easy to bend (a state where the tire is easily deformed by a load) as compared with a tire for other purposes running on a paved road with a relatively high internal pressure. In addition, as a special feature of the traveling course, there are many traveling situations where jumps, gaps, etc. are arranged and the tires are greatly bent. Therefore, a bias structure that can ensure steering stability (particularly, tire rigidity) has been developed as a mainstream for rough terrain tires when used under such conditions.

  The bias structure is composed of a carcass layer in which the entire region intersects from the side portion of the tire to the tread portion, and has an advantage that rigidity can be easily secured by the function of the laminated plate. That is, the bias structure is a structure that easily balances the tire rigidity with performance characteristics such as grip strength and ground contact feeling in a rough terrain tire that is generally used at a low internal pressure.

  In recent years, radial structuring of tires for rough terrain has also been studied, and tires have been proposed that have significantly improved traction performance and other steering stability performance compared to conventional bias structures. As a technique related to improvement of a tire having a radial structure, for example, Patent Document 1 discloses a so-called cord in which an uneven shape of a belt cord appears at the groove bottom around the tread block by setting the end of the belt layer to a predetermined position. There have been proposed a technique for improving the steering stability by arranging a technique for suppressing the projecting and arranging a block row of the tread portion so as to satisfy a predetermined relationship. In addition, Patent Documents 2 to 4 are cited as techniques for improving the traction performance and steering stability of a pneumatic tire for a motorcycle having a radial structure.

JP 2010-173659 A JP 2009-51360 A JP 2009-126422 A JP 2010-126033 A

  In a radial structure, it is common to arrange a hard belt layer so as to cover the entire tread surface (from one side of the tire shoulder to the opposite side of the shoulder), which is high due to the "tag" effect unique to the radial structure. Contributes to traction performance. However, the radial structure is, as the term suggests, the carcass layer forms an angle in a direction close to a straight line from the tire side part to the tread part (a direction perpendicular to the tire equatorial plane). It does not have a complicated carcass layer. Therefore, as a rough terrain tire used under a low internal pressure condition, it has been difficult to secure the rigidity of the side portion suitable for running on rough terrain with a general radial structure.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire for a motorcycle that can eliminate a shortage of lateral force and a shortage of durability caused by insufficient rigidity of the side portion, which is a disadvantage caused by the radial structure of the tire for rough terrain. It is in.

  As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be solved by setting the structure of a pneumatic tire for a motorcycle with a radial structure as follows. It came to complete.

That is, the pneumatic radial tire for a motorcycle according to the present invention includes at least one layer of a carcass ply that is folded and locked around a bead core embedded in each of a pair of bead portions, and the outer side of the carcass ply in the tire radial direction. In a pneumatic radial tire for a motorcycle, including at least one belt layer and a tread portion disposed on the outer side in the tire radial direction of the belt layer,
A flipper layer that is folded around the bead core from the inside to the outside of the tire is provided outside the carcass ply, and a folded end of the flipper layer terminates between the carcass ply and the belt layer. Is.

  In the present invention, the tread portion has a pattern composed of a plurality of block rows on the outer side in the tire radial direction, and the end portion of the belt layer is on the inner side in the tire width direction of the block row located on the outermost side in the tire width direction. It is preferable to terminate between the end portion and the end portion on the outer side in the tire width direction. In the present invention, the tread portion preferably has a two-layer structure of cap rubber and base rubber having different hardnesses.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic radial tire for motorcycles which can eliminate the lack of lateral force and the lack of durability resulting from the lack of rigidity of the side portion can be provided.

1 is a cross-sectional view in the width direction of a pneumatic radial tire for a motorcycle according to a preferred embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view in the width direction of a pneumatic radial tire for a motorcycle according to a preferred embodiment of the present invention. As shown in the figure, a pneumatic radial tire 10 for a motorcycle according to the present invention includes at least one carcass ply 2 that is folded and locked around a bead core 1 embedded in a pair of bead portions 11 (illustrated example). 2) and a pair of sidewall portions 13 extending inward in the tire radial direction from both ends thereof, and a tread portion 12 in the tread portion 12. At least one belt layer 3 is disposed outside the carcass ply 2 in the tire radial direction. In the illustrated example, the belt layer 3 is a spiral belt layer made of rubber-coated cord spirally wound in the circumferential direction, and a pattern made up of a plurality of block rows 14 is arranged on the outer side in the tire radial direction of the tread portion 12. Has been. A bead filler 4 is disposed on the outer side of the bead core 1 in the tire radial direction.

In the present invention, the flipper layer 5 is arranged on the outer side in the tire radial direction of the carcass ply 2, the bead core 1 is wound back from the inner side of the tire toward the outer side, and the folded end ends between the carcass ply 2 and the belt layer 3. Have By adopting such a configuration, in the radial tire for rough terrain where it is difficult to ensure the rigidity of the side portion 13 only with the carcass ply 2, the rigidity of the side portion 13 is ensured and the lack of lateral force and durability is eliminated. can do. Furthermore, by the folded end 5E ₁ flipper layer 5 and between the carcass ply 2 and the belt layer 3, ensuring the rigidity only side portions 13 which are required higher stiffness in the conventional structure, have sufficient rigidity The tread portion 12 is preventing the rigidity from becoming unnecessarily large.

  As the flipper layer 5, a plurality of highly elastic organic fiber cords arranged in a rubber coating can be used, and an aromatic polyamide cord can be preferably used as the organic fiber cord. In the present invention, the angle of the flipper layer 5 with respect to the tire radial direction can be in the range of 40 ° to 55 °. In the illustrated example, the number of flipper layers 5 is one, but a plurality of flipper layers 5 may be arranged as necessary.

  Further, the tire of the present invention has a tread surface covered with a belt layer, and the belt layer is high due to the “tag” effect unique to the radial structure when the vehicle body is raised (when the camber angle is small). Contributes to traction performance. However, as described above, rough terrain tires are used under low internal pressure conditions, so it is necessary to secure a feeling of grounding and grip by bending the tire, but when the vehicle body is tilted significantly (when a large camber angle is applied) ) Was affected by a high-rigidity belt layer, and appropriate bending could not be obtained, resulting in a decrease in grip. Therefore, in the present invention, as shown in the drawing, the end of the belt layer 3 is located between the end 14A on the tire width direction inner side and the end 14B on the outer side in the tire width direction of the block row 14 positioned on the outermost side in the tire width direction. It is preferable to terminate with.

  That is, since the belt layer 3 is not arranged at the full width of the tread portion 12, when the vehicle body is inclined and a grip or a feeling of grounding due to the deflection of the tire is required, it is difficult to bend by the highly rigid belt layer 3. It is possible to suppress and secure a grip and a feeling of grounding. On the other hand, in rough terrain traveling, when the vehicle body is raised and the tire is required to generate traction in the circumferential direction, high traction performance due to the “tag” effect unique to the radial structure can be exhibited.

  If the end of the belt layer 3 is arranged inside the outermost block row 14 in the width direction, the high rigidity belt layer 3 can eliminate the difficulty of bending, but at the same time, the outermost block row 14 Loss rigidity against lateral force. Therefore, by arranging the end portion of the belt layer 3 below the outermost block row 14, it is possible to ensure both appropriate deflection and shoulder block rigidity against lateral force. As a result, the bias structure contrast, straight traction and other steering stability can be greatly improved while solving the shortage of lateral force and lack of durability caused by the lack of side rigidity due to the radial structure of tires for rough terrain. Can do.

  Further, in the present invention, it is preferable that the tread portion 12 has a two-layer structure including a cap rubber on the tread surface side and a base rubber on the tread bottom surface side, and the cap rubber and the base rubber have different hardnesses. By making the tread rubber a two-layer structure of cap rubber and base rubber with different hardness, depending on the road surface condition, a combination of a hard cap rubber and a soft base rubber, or a combination of a soft cap rubber and a hard base rubber, etc. Thus, it is possible to ensure necessary characteristics without changing the rigidity of the entire block. The hardness of the cap rubber and the base rubber can be realized by appropriately selecting a rubber composition and its filler according to a conventional method.

  In the pneumatic radial tire for a motorcycle according to the present invention, it is important that the end portion of the belt layer 3 and the flipper layer 5 satisfy the above-described conditions, whereby the intended effect of the present invention can be obtained. Other conditions such as the tire structure and material are not particularly limited. For example, examples of the reinforcing material constituting the belt layer 3 include nylon fiber, aromatic polyamide (trade name: Kevlar), and steel. Among them, aromatic polyamide and steel can suppress expansion of the tread portion without stretching even at high temperatures.

  Further, the carcass ply 2 constituting the skeleton of the pneumatic radial tire for motorcycles of the present invention is formed by arranging relatively highly elastic textile cords in parallel with each other. The number of carcass plies 2 may be one or two, or three or more. Further, both end portions of the carcass ply 2 may be folded around the bead core 1 from the inner side of the tire as shown in FIG. 1 to be locked, or may be locked by being sandwiched by bead wires from both sides (not shown). ), Any fixing method may be used. An inner liner is disposed on the innermost layer of the tire (not shown).

  The pneumatic radial tire for motorcycles of the present invention can be suitably used for motorcycle rough terrain tires and motocross racing tires mainly intended for use on rough terrain including muddy ground.

Hereinafter, the present invention will be specifically described with reference to examples.
<Example>
A pneumatic radial tire for a motorcycle having a cross-sectional structure as shown in FIG. 1 was produced with a tire size of 120 / 80R19 in accordance with the following conditions. The test tire includes a carcass composed of two carcass plies (body plies) extending across a toroid between a pair of bead cores. Nylon fiber was used for the carcass ply, and the angle of the carcass was set to the radial direction (the angle with respect to the equator direction was 90 °).

  A spiral belt layer was disposed as the belt layer. The spiral belt layer was formed in a spiral shape by spirally winding a steel cord in which a steel single wire having a diameter of 0.18 mm was twisted in a 1 × 5 type in the equator direction. The spiral belt layer is a method in which a belt-like body in which a single parallel cord is embedded in a coated rubber is wound in a spiral direction along the tire equator direction in the tire rotation axis direction. Formed with. In addition, as a reinforcing cord for the flipper layer, a polyester cord of a double twist of 1500 denier was used, the number of drivings was 36/5 cm, and an angle with respect to the tire radial direction was 30 °.

<Comparative example>
A tire having the same structure as that of the example was manufactured except that the flipper layer was not disposed and the spiral belt layer was disposed in the entire width of the tread.

<Conventional example>
A tire having the same structure as that of the comparative example was manufactured except that the angle of the carcass was set to 30 ° with respect to the equator direction and a breaker was disposed instead of the belt layer. The material of the breaker cord and the cord structure were polyester cords of two twisted 1500 deniers, and the cord angle was 30 °.

<Driving test>
Each test tire obtained is mounted on a motorcycle wheel (WM2.15-19), the tire pressure is set to 80 kPa, and an actual vehicle running test is conducted on a course exclusively for rough terrain driving, rigidity, durability, straight ahead The traction and cornering characteristics were evaluated. The front tire was a conventional tire.

  Rigidity, straight traction, and cornering characteristics (grip and ground feel) were evaluated by the test rider's feeling. The result was an index with the conventional example being 100. In addition, durability was evaluated using a drum tester equipped with a drum having a smooth surface, and each tire was run (rotated) on the drum for a predetermined distance and cracked on the side. It was expressed as an index. The obtained results are shown in Table 1.

  Compared to the conventional tire, the comparative tire has greatly improved straight traction performance. However, the rigidity and durability decreased due to insufficient rigidity of the side portions. Further, due to the influence of the spiral belt layer arranged to the end of the tread, an appropriate deflection was not obtained when the camber angle was given, and the grip and the feeling of ground contact during cornering were lowered.

  It turns out that the tire of an Example has high traction performance like the tire of a comparative example. Further, in the tires of the examples, the lack of rigidity in the side portions was resolved, and the rigidity and durability were improved. Furthermore, by arranging the spiral belt layer under the outermost block row in the tire width direction, not at the tread edge, it is possible to obtain an appropriate deflection when giving a camber angle, and the grip and touch feeling at cornering are improved. .

  From the above, according to the present invention, it is possible to obtain a tire that is superior in rigidity, durability, and traction than the conventional bias structure.

1 Bead Core 2 Carcass 3 Belt 4 Bead Filler 5 Flipper Layer 10 Pneumatic Radial Tire for Motorcycle 11 Bead Part 12 Tread Part 13 Side Part 14 Block Row

Claims (3)

At least one layer of carcass ply folded and locked around a bead core embedded in each of a pair of bead portions, at least one belt layer radially outward of the carcass ply, and a tire of the belt layer In a pneumatic radial tire for a motorcycle provided with a tread portion arranged radially outside,
A flipper layer that is folded around the bead core from the inside to the outside of the tire is provided outside the carcass ply, and a folded end of the flipper layer terminates between the carcass ply and the belt layer. Pneumatic radial tire for motorcycles.   The tread portion has a pattern composed of a plurality of block rows on the outer side in the tire radial direction, and the end portion of the belt layer is located on the outermost side in the tire width direction and the tire width direction inner end portion and the tire width. The pneumatic radial tire for a motorcycle according to claim 1, wherein the pneumatic radial tire is terminated with an end portion on the outer side in the direction.   The pneumatic radial tire for a motorcycle according to claim 1 or 2, wherein the tread portion has a two-layer structure of a cap rubber and a base rubber having different hardnesses.

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