JP2011230584A - Pneumatic radial tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for a motorcycle, which has improved a turning force by raising a grip when turning.SOLUTION: The pneumatic radial tire for the motorcycle is provided with one or more radial carcass layers 2 which stretch over a pair of right and left bead cores 1 in a toroidal shape, and a belt arranged outside in a radial direction of the tire, wherein the belt includes a circumferential belt layer 3 whose cord direction is substantially the circumferential direction of the tire. A rubber layer 4 whose tensile modulus of elasticity is 30-60 MPa when it is 100% stretched is continuously arranged inside in the radial direction of the tire of the radial carcass layer 2 around a tire equatorial plane with the width of 70-90% to the width of the circumferential belt layer 3.

Description

  The present invention relates to a pneumatic radial tire for motorcycles (hereinafter, also simply referred to as “tire”), and more specifically, an improvement of a pneumatic radial tire for a motorcycle including a circumferential belt layer on a radially outer side of a carcass ply. About.

  In recent years, motorcycles have become increasingly faster, and accordingly, pneumatic tires for motorcycles also serve as outermost belt layers in the circumferential direction so that they can withstand circumferential forces due to centrifugal force during high-speed running. A structure in which a belt layer is arranged has become common (see, for example, Patent Document 1).

  One of the important performances of such a tire for a motorcycle is a grip force when turning. In particular, in races and the like, in recent years, there has been an increasing demand for securing a sufficient grip when turning in a large camber angle region where the camber angle (camber angle, CA) is 50 ° or more.

  As an improved technique related to a pneumatic tire for motorcycles, for example, in Patent Document 2, a belt layer is provided with a spiral belt made of a highly elastic reinforcing cord, the cord direction being substantially the tire circumferential direction, and at least A technique for disposing a reinforcing rubber layer made of rubber that is the same or different from the carcass coating rubber in the tread region between two carcass plies is disclosed.

JP-A-10-67207 (Claims etc.) JP 2004-67059 A (Claims etc.)

  However, in a tire having a circumferential belt layer, since the restraint in the tire circumferential direction is too strong, the ground contact area in the large camber angle region becomes small, and the grip at the time of turning may be insufficient. It was sought after.

  Accordingly, an object of the present invention is to solve the above-mentioned problems and improve the turning force by raising the grip at the time of turning in a large camber angle region in a motorcycle pneumatic radial tire having a circumferential belt layer. An object of the present invention is to provide a pneumatic radial tire for a motorcycle.

  As a result of intensive studies, the present inventor has found that in a tire having a circumferential belt layer, the load is not distributed with respect to the shear force generated in the lateral direction with respect to the traveling direction in the contact surface. There is a region that is not gripped in the ground, and it has been found that the turning force can be improved by gripping the ground region that is not gripped, and the present invention has been completed.

That is, the pneumatic radial tire for a motorcycle of the present invention includes one or more radial carcass layers straddling a toroidal shape between a pair of left and right bead cores, and a belt disposed on the radial outer side of the radial carcass layer. In the pneumatic radial tire for a motorcycle, the belt includes a circumferential belt layer in which a cord direction is substantially a tire circumferential direction.
A rubber layer having a tensile modulus of elasticity of 30 to 60 MPa at 100% elongation is 70 to 90% of the width of the circumferential belt layer centering on the tire equatorial plane inside the radial carcass layer in the tire radial direction. It is characterized by being arranged continuously in width.

Further, another pneumatic radial tire for a motorcycle of the present invention includes one or more radial carcass layers straddling a toroidal shape between a pair of left and right bead cores, and a belt disposed on the radial outer side of the radial carcass layer. In a pneumatic radial tire for a motorcycle, the belt includes a circumferential belt layer whose cord direction is substantially the tire circumferential direction.
The tensile modulus at 100% elongation of the inner liner layer disposed in the tire innermost layer is 30 to 60 MPa, and the thickness of the inner liner layer is the width of the circumferential belt layer centered on the tire equatorial plane. On the other hand, the region having a width of 70 to 90% is formed thicker than the outside of the region.

  According to the present invention, it is possible to realize a pneumatic radial tire for a motorcycle that improves the turning force by raising the grip particularly when turning in the large camber angle region by the above configuration. It was.

1 is a cross-sectional view in the width direction showing an example of a pneumatic radial tire for a motorcycle according to the present invention. It is a graph which shows the load distribution ratio of the turning outside in the contact surface in the test tire of a prior art example and an Example, and a turning inside. It is a graph which shows the measurement result of the lateral force in the sample tire of a prior art example and an Example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view in the width direction showing an example of a pneumatic radial tire for a motorcycle according to the present invention. As shown in the figure, the pneumatic radial tire for a motorcycle according to the present invention has one or more layers straddling the toroidal shape between a pair of left and right bead cores 1, in the illustrated example, one radial carcass layer 2 and the outer side in the tire radial direction. And an arranged belt.

  In the present invention, the belt needs to include a circumferential belt layer whose cord direction is substantially the tire circumferential direction. Here, in the present invention, the fact that the cord direction is substantially the tire circumferential direction means, for example, that the cord angle is within a range of ± 0 ° to 10 ° with respect to the tire circumferential direction. In the illustrated example, only the circumferential belt layer 3 is provided as the belt. However, if desired, one or more belt layers may be further provided inside the circumferential belt layer 3 in the tire radial direction. it can. As a belt layer other than the circumferential belt layer in this case, for example, a pair of inclined belt layers having a cord angle of ± 60 ° to 90 ° with respect to the tire circumferential direction can be used.

  Further, in the present invention, the tensile elasticity at the time of 100% elongation is 70 to 90% of the width of the circumferential belt layer 3 centering on the tire equatorial plane, inside the radial carcass layer 2 in the radial direction of the tire. The rubber layer 4 having a rate of 30 to 60 MPa is continuously arranged. By arranging such a rubber layer 4, the bending rigidity of the tire can be increased in a large camber angle region (CA ≧ 50 °) inside the turning of the ground contact surface. Thereby, at the time of turning at a large camber angle, it is possible to obtain an effect of distributing a larger load on the tire on the inside of the turning in the contact surface. By increasing the ratio of the distributed load on the inside of the turn within the contact surface, the grip in this region can be raised, and as a result, the turning force can be improved and the corner can be escaped more quickly. At this time, since the total amount of the load applied to the tire is unchanged, the load distributed outside the turn decreases, but the load distributed more inside the turn than the outside of the turn can exert a larger gripping force. It can be done.

  In the present invention, the tensile elastic modulus at 100% elongation of the rubber layer 4 needs to be 30 to 60 MPa, and preferably 40 to 50 MPa. If the tensile elastic modulus of the rubber layer 4 is less than 30 MPa, the distributed load on the inside of the turn does not increase, and if it exceeds 60 MPa, the distributed load on the outside of the turn decreases too much. Cannot be obtained. Moreover, if the arrangement width of the rubber layer 4 is less than 70% of the width of the circumferential belt layer 3, the distributed load inside the turning will not increase, and if it exceeds 90%, the distributed load inside the turning will increase. In any case, the desired effect of the present invention cannot be obtained.

  In the present invention, the rubber layer 4 is not provided as an independent member, but the thickness of an inner liner layer (not shown) disposed in the innermost layer of the tire is set in the circumferential direction with the tire equatorial plane as the center. You may provide in the area | region of 70 to 90% of width | variety with respect to the width | variety of the belt layer 3, by forming thicker than the outer side of this area | region. Thus, even if the rubber layer is provided substantially by making the thickness of the inner liner layer thicker in the central region than in the tire side region, the desired effect of the present invention can be obtained similarly. In this case, in addition to having the function of preventing air permeation, it is necessary to provide the inner liner layer so that the tensile elastic modulus at 100% elongation is 30 to 60 MPa, preferably 40 to 50 MPa.

  In the present invention, only the point of providing the rubber layer is important, whereby the desired effect of the present invention can be obtained, and the other specific rubber layer or inner liner layer can be obtained. The rubber composition, the details of the tire structure, the material of each member, and the like can be appropriately configured according to conventional methods, and are not particularly limited.

  For example, as the reinforcing cord of the radial carcass layer 1, an organic fiber cord such as nylon or polyester can be used. Further, as the reinforcing cord of the circumferential belt layer 3, in addition to the steel cord, aromatic polyamide (aramid), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), rayon, Zylon (registered trademark) (polyparaphenylenebenzo) Organic fiber cords such as bisoxazole (PBO fiber) and aliphatic polyamide (nylon) can be used.

  Further, as shown in the drawing, the tire of the present invention includes a pair of left and right bead portions 11, a pair of sidewall portions 12 that are continuous with the bead portions 11, and a tread portion 13 that is continuous in a toroidal shape between the sidewall portions 12. A tread pattern is appropriately formed on the surface of the tread portion 13 (not shown).

Hereinafter, the present invention will be described in more detail with reference to examples.
<Conventional example>
A pneumatic radial tire for a motorcycle having a conventional structure, which includes two radial carcass layers (cord material: nylon) and a circumferential belt layer (cord material: steel) disposed on the outer side in the tire radial direction, was manufactured. . The tire conditions were as follows: tire size cross section: rear tire 180/55, tire inch diameter: rear tire 17 inch, test rim: MT 5.5 × 17 M / C, test use internal pressure: 290 kPa.

<Example>
On the inner side in the tire radial direction of the two radial carcass layers, a rubber layer having a tensile elastic modulus of 40 MPa at 100% elongation is 80% of the width of the circumferential belt layer centering on the tire equatorial plane. A pneumatic radial tire for a motorcycle was produced in the same manner as the conventional example except that the tires were continuously arranged.

  Each test tire obtained was subjected to a load distribution measurement test and an axial force measurement test using a flat belt testing machine in accordance with the following.

(1) Load distribution measurement test The load distribution in the contact surface was measured under the measurement conditions of CA = 50 ° and a load of 1500 N for each of the test tires of the conventional example and the example. The result is shown in the graph of FIG. 2 as a load distribution ratio between the turning outer side and the turning inner side. Here, this load distribution ratio is obtained when the load applied to the tire is divided into two parts with the center of contact being the center of contact (position of 1/2 of the maximum contact width) on the outside of the turn and the inside of the turn in the contact surface. It is defined as the ratio of the load between the outside of the turn and the inside of the turn. In this test, this load distribution ratio was used as an index of the distributed load inside the turning in the ground plane.

  As shown in the graph of FIG. 2, the load distribution ratio in the test tire of the conventional example is turning inside: turning outside = 50: 50, whereas the load distribution ratio in the test tire of the example is turning inside: turning. Outer side = 55: 45, and it can be seen that in the test tire of the example, the ratio of the distributed load on the inner side of the turn is increased by 5%.

(2) Axial force measurement test using a flat belt testing machine For each of the test tires of the conventional example and the example, the axial force was measured under measurement conditions of CA = 50 ° and a load of 1500 N, and the lateral force at CA = 50 ° was measured. The force is shown as an index relative to the conventional example. The larger the index, the greater the lateral force. The result is shown in the graph of FIG.

  As shown in the graph of FIG. 3, when the axial force of the test tire of the conventional example is 100, the lateral force of the test tire of the example is 108. In the test tire of the example, the lateral force of the test tire is 8 in comparison with the conventional example. It can be seen that% lateral force is improved.

  From the above results, by placing a rubber layer that satisfies the predetermined condition inside the radial carcass layer in the tire radial direction, the ratio of the distributed load inside the turning in the ground contact surface in the large camber angle region is increased, and It was confirmed that a tire with improved power and improved turning power could be obtained.

1 Bead core 2 Radial carcass layer 3 Circumferential belt layer 4 Rubber layer 11 Bead portion 12 Side wall portion 13 Tread portion

Claims (2)

One or more radial carcass layers straddling between a pair of left and right bead cores, and a belt disposed on the radial outer side of the radial carcass layer in the tire radial direction, the belt having a cord direction substantially in the tire circumferential direction In a pneumatic radial tire for a motorcycle including a circumferential belt layer,
A rubber layer having a tensile modulus of elasticity of 30 to 60 MPa at 100% elongation is 70 to 90% of the width of the circumferential belt layer centering on the tire equatorial plane inside the radial carcass layer in the tire radial direction. A pneumatic radial tire for a motorcycle, characterized by being continuously arranged in width. One or more radial carcass layers straddling between a pair of left and right bead cores, and a belt disposed on the radial outer side of the radial carcass layer in the tire radial direction, the belt having a cord direction substantially in the tire circumferential direction In a pneumatic radial tire for a motorcycle including a circumferential belt layer,
The tensile modulus at 100% elongation of the inner liner layer disposed in the tire innermost layer is 30 to 60 MPa, and the thickness of the inner liner layer is the width of the circumferential belt layer centered on the tire equatorial plane. In contrast, a pneumatic radial tire for a motorcycle is formed in a region having a width of 70 to 90% thicker than an outside of the region.

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