JP2006273240A - Pneumatic tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the high-speed durability of a pneumatic tire for a motorcycle by realizing the adequate physical properties of a tread part. <P>SOLUTION: The tangential force coefficient of a pneumatic tire mounted on a motorcycle is ≥1.1. The tire 1 has a pair of bead parts 3 with a bead core 2 embedded therein, a pair of side wall parts 4 extending from the bead parts 3 outwardly in the tire radial direction, and a tread part 5 extending across the side wall parts 4, 4. The tread part 5 is divided into three portions, i.e., a center area 9 including the tire equatorial plane CL, and shoulder areas 10, 10 located across the center area 9. In at least the center area 9, the ratio tan δ/E' of the loss tangent tan δ to the dynamic modulus E' of elasticity at 60°C is in a range of 0.025-0.075. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire for a motorcycle, and more particularly to a pneumatic tire suitable for use in a motorcycle having a large driving force, and improves the durability of the tire.

  One index indicating the driving performance of a motorcycle is a tangential force coefficient. “Tangential force” refers to the driving force generated on the contact surface of the tire mounted on the driving wheel of the vehicle. The value obtained by dividing the average value of the tangential force when traveling in the top gear by the tire load. It is called “tangential force coefficient”.

  As motorcycles have higher performance and higher output, the tangential force coefficient of the vehicle tends to increase, and tires mounted on such vehicles are required to have higher speed durability. Since tires repeatedly generate heat due to bending deformation due to unevenness on the road surface and the like, conventionally high speed durability has been improved by using rubber with a low loss tangent tan δ on the tread contact surface (for example, patents). Reference 1).

  Patent Document 2 describes a tire that has a so-called cap-and-base structure in which a shoulder portion is composed of two upper and lower layers, and the base layer is composed of hard rubber to improve durability.

  However, as the speed of the vehicle increases, the tires are also required to have higher performance. Finally, motorcycles having a design value of the tangential force coefficient of 1.1 or more have been developed. In addition, a tire with only a low loss tangent tan δ cannot satisfy the required high-speed durability.

JP 10-119513 A Japanese Patent Laid-Open No. 11-189010

  Accordingly, an object of the present invention is to provide a pneumatic tire excellent in high-speed durability that can be mounted on a motorcycle having a tangential force coefficient of 1.1 or more by optimizing the physical properties of the tread portion. It is in.

  In order to achieve the above object, the present invention is a pneumatic tire mounted on a motorcycle having a tangential force coefficient of 1.1 or more. Here, as described above, the “tangential force coefficient” is the average value of the tangential force when the tire mounted on the driving wheel of the vehicle travels in the top gear with the driving force generated on the ground contact surface as the tangential force. The value divided by the tire load.

  The pneumatic tire includes a pair of bead portions in which a bead core is embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portion, and a tread portion extending between both sidewall portions. At least the center region when the portion is divided into a center region including the tire equatorial plane and both shoulder regions located across the center region is a ratio of the loss tangent tan δ and the dynamic elastic modulus E ′ at 60 ° C. It is preferable that tan δ / E ′ is in the range of 0.025 to 0.075. The “center area” as used herein refers to the tire mounted on the applicable rim specified by JATMA, and the air pressure corresponding to the maximum load capacity is applied and the maximum load capacity acts on the road surface at a camber angle of 0 °. It shall mean the tread contact area.

  In this case, the loss tangent tan δ is more preferably 0.4 or less.

  Moreover, it is preferable that a tread part comprises the center area and both shoulder areas with the same rubber, or comprises both shoulder areas with a softer rubber than the center area.

  Furthermore, it is preferable that the tread portion is composed of a cap rubber layer on the tread surface side and a base rubber layer on the tread bottom surface side. In this case, the base rubber layer more preferably has a tangent loss tan δ at 60 ° C. of 0.35 or less.

  According to the present invention, by optimizing the physical properties of the tread portion, it is possible to provide a pneumatic tire excellent in high-speed durability that can be mounted on a motorcycle having a tangential force coefficient of 1.1 or more. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a cross section in the width direction of a first embodiment of a pneumatic tire (hereinafter referred to as “tire”) according to the present invention.

  A tire 1 shown in FIG. 1 is a tire that is mounted on a motorcycle having a tangential force coefficient of 1.1 or more and exhibits desired high-speed durability. Of course, it can also be used as a motorcycle tire having a tangential force coefficient of less than 1.1.

  The tire 1 includes a pair of bead portions 3 in which bead cores 2 are embedded, a pair of sidewall portions 4 that extend outward from the bead portion 3 in the tire radial direction, and a tread portion 5 that extends across both sidewall portions 4 and 4. With In this embodiment, for example, a carcass 6 is configured by rubber-covering a plurality of reinforcing elements such as high-elastic textile cords arranged in parallel so that an angle formed with the tire equatorial plane CL is 65 to 90 °. 6 is wound around the bead core 2 made of, for example, a non-stretchable annular body and the bead apex 7 disposed adjacent thereto on the bead core 2 from the inner side in the tire width direction to the outer side. Further, a ribbon-like member, for example, a rubber-coated non-extensible high elastic cord is spirally wound between the carcass 6 and the tread portion 5 so as to be substantially parallel to the tire equatorial plane CL. A belt 8 having a substantially same width as that of the belt 8 is disposed. This configuration is merely an example of a preferred embodiment, and a configuration similar to a conventionally known tire can be employed.

  In the tire 1 according to the present invention, at least when the tread portion 5 is divided into the center area 9 including the tire equatorial plane CL and the shoulder areas 10 and 10 located across the center area 9, at least. In the center region 9, the ratio tan δ / E ′ of the loss tangent tan δ and the dynamic elastic modulus E ′ at 60 ° C. is in the range of 0.025 to 0.075.

  As described above, in the conventional tire, in order to deal with a tire having a large tangential force coefficient, the tangent loss of the rubber constituting the tread portion has been reduced. This is because if the loss tangent is reduced, the heat generated by the rubber itself subjected to the bending deformation is reduced. However, if the tangent loss is reduced, tire slip during load rolling is also promoted, so there is a limit to reducing the amount of heat generated by only the tangent loss. In particular, when it is mounted on a motorcycle that exhibits an unprecedented large driving force with a tangential force coefficient of 1.1 or more, even if the tangent loss is reduced and the heat generation amount is reduced, the heat generation amount generated by slipping is reduced. As a result, the calorific value increased on the contrary, and it was difficult to satisfy the required high-speed durability.

  Therefore, the inventor conducted extensive research on the physical properties of the tread portion that can reduce both the heat generation of the rubber itself due to the bending deformation and the heat generation due to the slip, and as a result, the ratio of the loss tangent tan δ to the dynamic elastic modulus E ′ tan δ / It has been found that if E ′ is optimized, the required high-speed durability can be satisfied. Here, tan δ / E ′ is set to 0.025 to 0.075. When this ratio is less than 0.025, heat generation by slip becomes dominant, and when it exceeds 0.075, it is caused by bending deformation. This is because the heat generated by the rubber itself by absorbing energy becomes dominant and it is difficult to achieve the high-speed durability required in any case.

  From the viewpoint of effectively suppressing the heat generation of the rubber itself, the loss tangent tan δ is preferably 0.4 or less, more preferably 0.35 or less. From the viewpoint of reducing heat generation due to slip, dynamic elasticity It is preferable to increase the rate E ′.

  Further, in the case where simplification of the manufacturing process is particularly emphasized, the tread portion 5 can be configured with the center region 9 and the shoulder regions 10 and 10 made of the same rubber as shown in FIG.

  However, when the cornering property is particularly important, it is preferable to have a so-called tread division structure in which both shoulder regions 10 and 10 are made of a softer rubber than the center region 9 as shown in FIG. In the motorcycle, the center area 9 of the tread portion of the tire is mainly grounded during straight traveling, while the tire contact area is shouldered from the center area 9 of the tread portion as the vehicle is tilted while turning. Transition to zone 10. Comparing the traveling frequency of straight traveling and turning traveling, the frequency of straight traveling is much higher. Therefore, rubber that places importance on high-speed durability is arranged in the center area 9, and rubber that emphasizes gripping power in the shoulder area 10. By arranging the tire, a tire excellent in both high-speed durability and cornering properties can be obtained.

  Further, as shown in FIG. 3, it is preferable that the tread portion 5 has a so-called cap-and-base structure including a cap rubber layer 11 on the tread surface side and a base rubber layer 12 on the tread bottom surface side. Of the tread portion 5, it is mainly the rubber on the tread surface side that contributes to heat generation due to slip, and the rubber that mainly contributes to heat generation due to bending deformation is mainly rubber on the bottom surface side of the tread, so a cap-and-base structure is adopted. This is because by optimizing the physical properties of the cap rubber layer 11 and the base rubber layer 12, heat generation can be further suppressed and high-speed durability can be improved. More specifically, if the tan δ / E ′ of the cap rubber layer 11 is 0.025 to 0.075 and the tangent loss tan δ at 60 ° C. of the base rubber layer 12 is 0.35 or less, heat generation and deflection due to slipping are caused. Both heat generation due to deformation can be suppressed at a high level, and excellent high-speed durability can be obtained.

  Note that the above description shows only a part of the embodiment of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the gist of the present invention. . For example, as shown in FIG. 4, a tread division structure and a cap-and-base structure can be used in combination.

  Next, tires according to the present invention were prototyped and performance evaluations were performed, which will be described below.

  The tires of Examples 1 and 2 are motorcycle tires having a tire size of 190 / 50ZR17M / C. A carcass in which two layers of plies formed by rubber-coating nylon cords and a steel cord are coated with rubber. 1 (Example 1) and FIG. 3 (Example 2) having the structure shown in FIG. 1 and the specifications shown in Table 1. The tire of Example 2 has a base rubber layer with tan δ of 0.31.

  For comparison, the tire size, carcass and belt are the same as in Examples 1 and 2 and have the same structure as in FIG. 1, but the tan δ / E ′ of the tread is 0.025. A tire having a conventional example was also made as a prototype.

  Each of the test tires was assembled into a wheel having a size of MT6.00 to form a tire wheel, and the tire wheel was mounted on the rear wheel of the test vehicle, and each of the following tests was performed.

(Slip rate)
The ratio Vt / Vr of the tire circumferential speed Vt to the traveling speed Vr when traveling on the asphalt pavement test course on the dry road surface with the top gear was determined, and the slip ratio was evaluated based on this ratio. The evaluation results are shown in Table 1.

(High speed durability)
The test course was run with the top gear, the running distance until the tire broke down was measured, and the high-speed durability was evaluated based on the running distance. The evaluation results are shown in Table 1.

  In addition, the evaluation result of the slip ratio and high-speed durability shown in Table 1 is shown as an index ratio when the evaluation result of the tire of the conventional example is 100, and the evaluation result of the slip ratio is better as the numerical value is smaller, The higher the numerical value, the better the high-speed durability evaluation result.

  From the evaluation results shown in Table 1, it can be seen that the tires of Examples 1 and 2 are superior in both slip ratio and high-speed durability as compared with the tires of the conventional examples.

  As described above, the present invention provides a pneumatic tire excellent in high-speed durability that can be mounted on a motorcycle having a tangential force coefficient of 1.1 or more by optimizing the physical properties of the tread portion. Became possible.

1 is a cross-sectional view in a width direction of a typical pneumatic tire for a motorcycle according to the present invention. FIG. 5 is a cross-sectional view in the width direction of another pneumatic tire for a motorcycle according to the present invention. FIG. 5 is a cross-sectional view in the width direction of another pneumatic tire for a motorcycle according to the present invention. FIG. 5 is a cross-sectional view in the width direction of another pneumatic tire for a motorcycle according to the present invention.

Explanation of symbols

1 tire 2 bead core 3 bead part 4 sidewall part 5 tread part 6 carcass 7 bead epex 8 belt 9 tread part center area 10 tread part shoulder area 11 tread part cap layer 12 tread part base layer

Claims (7)

  A pneumatic tire mounted on a motorcycle having a tangential force coefficient of 1.1 or more.   A pair of bead portions with embedded bead cores, a pair of sidewall portions extending outward in the tire radial direction from the bead portions, and a tread portion extending between both sidewall portions, the tread portion being arranged on the tire equatorial plane The ratio of tan δ / E ′ between the loss tangent tan δ and the dynamic elastic modulus E ′ at 60 ° C. is at least at least the center region in the case where the center region is divided into three including the center region including the center region and the shoulder regions located across the center region. The pneumatic tire according to claim 1, which is in a range of 025 to 0.075.   The pneumatic tire according to claim 2, wherein the loss tangent tan δ is 0.4 or less.   4. The pneumatic tire according to claim 2, wherein the tread portion includes a center region and both shoulder regions made of the same rubber.   4. The pneumatic tire according to claim 2, wherein the tread portion is formed of rubber that is softer than the center region in both shoulder regions.   The pneumatic tire according to any one of claims 2 to 4, wherein the tread portion includes a cap rubber layer on a tread surface side and a base rubber layer on a tread bottom surface side.   The pneumatic tire according to claim 6, wherein the base rubber layer has a tangent loss tan δ at 60 ° C. of 0.35 or less.

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