JP5081003B2 - Motorcycle tires - Google Patents

Description

  The present invention relates to a motorcycle tire that can exhibit optimum grip performance while ensuring durability.

  Unlike a four-wheeled vehicle such as a passenger car, a motorcycle turns with a large bank angle when turning. For this reason, tires used for motorcycles have a tread surface that is convex outward in the radial direction of the tire in a tire meridian cross section including the tire rotation axis, and the radius of curvature is larger than that of four-wheeled vehicle tires. And small. Conventionally, in order to improve the high-speed running stability and durability of such a motorcycle tire, a motorcycle tire comprising a tread rubber composed of a base rubber layer and a cap rubber layer, each of which is regulated in physical properties, is disclosed in the following patent. It is proposed in Document 1.

Japanese Patent Laid-Open No. 7-195906

  However, in the above-mentioned Patent Document 1, the center part, middle part, and shoulder part of the cap rubber layer that comes in contact with the road surface are all formed of rubber having the same physical properties, and for improvement in grip performance and durability, There was room for further improvement.

  That is, when the motorcycle tire is traveling straight, almost the entire center portion of the tread surface and a part of the middle portion are mainly in contact with the road surface. In other words, since the edge of the tread contact surface is located in the middle part, a large distortion occurs in the middle part. On the other hand, at the time of turning, the middle part and the shoulder part mainly contact the road surface. For this reason, the middle portion where there are many opportunities to contact the road surface tends to generate heat most easily among the tread rubber. In tread rubber for motorcycle tires, excellent grip performance is usually exhibited by moderate heat generation. However, excessive heat generation tends to cause damage such as blowout.

  The present invention has been devised in view of the above situation, and in the center part, middle part and shoulder part of the tread rubber arranged in the tread part, the respective thickness and the loss compliance at a temperature of 70 ° C. ( Based on limiting the loss compliance ratio (LC70 / LC100) to a certain range (LC70) and the loss compliance (LC100) at a temperature of 100 ° C (LC70), the optimum grip performance is achieved when going straight and turning. At the same time, the main purpose is to provide a motorcycle tire capable of improving durability.

   The invention of claim 1 of the present invention is a motorcycle tire in which the tread surface of the tread portion is convex outward in the tire radial direction and extends in a circular arc shape, and the tread rubber disposed on the tread portion is A center portion disposed in a region of 25 to 35% of a tread deployment width centered on the tire equator, a shoulder portion disposed in a region of 15 to 25% of the tread deployment width from the tread edge to the tire equator side, A middle portion disposed in a region between the center portion and the shoulder portion, wherein the thickness tm of the middle portion is 0.8 to 0.9 times the thickness tc of the center portion, and the shoulder The thickness ts of the part is 1.0 to 1.3 times the thickness tc of the center part, and the center part has a loss compliance (LC70) at a temperature of 70 ° C. and a loss compliance at a temperature of 100 ° C. Loss compliance ratio, which is the ratio (LC70 / LC100) to the liquid crystal (LC100) of 0.90 to 1.20, the loss compliance ratio of the middle portion is 0.90 to 1.30, and the shoulder portion has a loss compliance ratio. The ratio is 1.10 to 1.50.

In the invention of claim 2, the loss compliance ratio RLc of the center portion, the loss compliance ratio RLm of the middle portion, and the loss compliance ratio RLs of the shoulder portion satisfy the following relationship (1). This is a motorcycle tire.
RLm <RLc <RLs (1)

  The invention according to claim 3 is the motorcycle tire according to claim 1 or 2, wherein the thickness ts of the shoulder portion is larger than 1.0 times and not larger than 1.3 times the thickness tc of the center portion. It is.

  The invention according to claim 4 is the motorcycle tire according to claim 1 or 2, wherein the center portion has a thickness of 5.0 to 12.0 (mm).

  The motorcycle tire of the present invention has a thickness compliance, a loss compliance (LC70) at a temperature of 70 ° C., and a loss at a temperature of 100 ° C. in the center portion, middle portion, and shoulder portion of the tread rubber arranged in the tread portion. The loss compliance ratio, which is the ratio (LC70 / LC100) to compliance (LC100), is limited to a certain range. That is, the thickness of the middle portion where the running tire is greatly distorted and is likely to become high temperature due to heat generation is set smaller than the center portion and the shoulder portion. Since the rubber thickness has the greatest influence on the heat generation, reducing this can effectively suppress the heat generation in the middle part during traveling, thereby preventing damage such as blowout and improving durability.

  In each rubber part, when the loss compliance ratio is larger than 1, excellent grip performance can be exhibited at a low temperature of about 70 ° C., whereas when it is less than 1, it is excellent at a high temperature of about 100 ° C. Grip performance is demonstrated. Although heat generation is suppressed by reducing the relative thickness of the middle part, it still tends to be hotter than other areas, so the loss compliance ratio should be limited to include a smaller value than the shoulder part. Excellent grip performance even at high temperatures.

  On the other hand, since the shoulder portion is disposed at both end portions of the tread rubber, the structure easily radiates heat compared to the center portion and the middle portion. For this reason, heat generation is promoted and the grip performance is enhanced by setting the shoulder portion to have a large thickness. However, even in this case, since the shoulder portion tends to be lower in temperature than other rubbers, a grip can be exhibited even at low temperatures by setting the loss compliance ratio (LC70 / LC100) to be large.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a tire meridian cross-sectional view including a tire rotation axis of a motorcycle tire (hereinafter, simply referred to as “tire”) 1 of the present invention. The tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. Yeah.

  In the cross section, the tread surface 2A that comes in contact with the road surface of the tread portion 2 protrudes outward in the tire radial direction and extends in an arc shape. Further, the tread edges 2e and 2e, which are the outer ends of the tread surface 2A in the tire axial direction, are located on the outermost side in the tire axial direction. The tread portion 2 is provided with one or a plurality of drain tread grooves 11.

  The carcass 6 is composed of, for example, one or more radial structures in which carcass cords are arranged at an angle of, for example, 70 to 90 ° with respect to the tire equator C, in this example, one carcass ply 6A. As the carcass cord, for example, an organic fiber cord such as polyester, nylon, rayon, aramid, or a steel cord is used if necessary.

  The carcass ply 6A is folded back from the inner side to the outer side in the tire axial direction around the bead core 5 extending from the main body 6a and extending from the main body 6a to the bead core 5 of the bead part 4 through the sidewall part 3 and the bead part 4. And a folded portion 6b. A bead apex 8 made of hard rubber extending from the bead core 5 to the outer side in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A, and the bead portion 4 is appropriately reinforced.

  The belt layer 7 is composed of, for example, a plurality of belt plies having belt cords arranged in parallel, and these are stacked so that the belt cords cross each other. The belt cord is preferably an organic fiber such as rayon or aromatic polyamide or a steel cord.

  A tread rubber 9 is disposed on the tread portion 2 on the outer side in the radial direction of the belt layer 7. In the present embodiment, the tread rubber 9 constitutes from the outer surface of the belt layer 7 to the tread surface 2A. Further, the tread rubber 9 of the present embodiment is composed of three kinds of rubber materials having different blends, and specifically, a center portion having a development width W1 of 25 to 35% of the tread development width TW centering on the tire equator C. 9A, a pair of shoulder portions 9C having a development width W3 of 15 to 25% of the tread development width TW from the tread edge 2e, and a pair of middle portions 9B arranged between the center portion 9A and the shoulder portions 9C Composed. Each of the rubber portions 9A to 9C is divided by a normal line 12 standing on the tread surface 2A. For example, a boundary line that inclines outward or inward in the tire axial direction from the tread surface 2A toward the belt layer 7. It may be divided by.

  In the present embodiment, the tread rubber 9 has a middle portion 9B having a thickness tm of 0.8 to 0.9 times the thickness tc of the center portion 9A, and a shoulder portion 9C having a thickness ts of the center portion 9A. The thickness is set to 1.0 to 1.3 times the thickness tc. Here, the thicknesses tc, tm, and ts of the respective parts are the average thicknesses measured at a pitch of 5 mm in the development width direction in the parts excluding the respective tread grooves 11 (note that it is easy to understand in FIG. 1). Thus, the rubber parts 9A to 9C are given the average thickness symbols tc, tm and ts.)

  Regarding the heat generation of the tread rubber 9, the thickness has the greatest influence. The larger the thickness, the easier the heat generation, and the smaller the thickness, the less the heat generation. For this reason, the thickness tm of the middle portion 9B where the heat generation tendency has been seen most conventionally is set as small as 0.8 to 0.9 times the thickness tc of the center portion 9A. Thereby, the temperature rise of the middle part 9B depending on the rubber thickness is suppressed, and damage such as blowout is suppressed.

  Here, if the thickness tm of the middle portion 9B exceeds 0.9 times the thickness of the center portion 9A, the above heat generation cannot be sufficiently suppressed. On the other hand, when the thickness tm of the middle portion 9B is less than 0.8 times the thickness of the center portion 9A, the change in the thickness of the tread rubber 9 is increased, and the wear resistance and the like may be significantly deteriorated. Therefore, it is not preferable. In particular, the thickness tm of the middle portion 9B is preferably 0.83 times or more and 0.87 times or less of the thickness tc of the center portion 9A. Note that the middle portion 9B of the present embodiment is configured so that the thickness gradually decreases gradually toward the center of the developed width W2. However, it is not limited to such an aspect.

  On the other hand, the thickness ts of the shoulder portion 9C is likely to dissipate heat during traveling due to its positional factors, and as a result, it may not be able to rise to a temperature (usually around 70 ° C.) necessary for obtaining basic grip performance. For this reason, conventionally, there was a tendency that the grip performance at the shoulder portion 9C at the time of turning was insufficient. Therefore, in the present invention, the thickness ts of the shoulder portion 9C is relatively 1.0 to 1.3 times the thickness tc of the center portion 9A, more preferably larger than 1.0 times and 1.3 times or less. The shoulder portion 9C is positively heated to increase the grip performance when turning.

  Here, when the thickness ts of the shoulder portion 9C is less than 1.0 times the thickness tc of the center portion 9A, the shoulder portion 9C cannot be sufficiently heated, and as a result, the grip performance during turning is insufficient. On the other hand, if the thickness ts of the shoulder portion 9C exceeds 1.3 times the thickness tc of the center portion 9A, the mass of the tire increases, and excessive temperature rise may be caused to reduce durability. is there. From such a viewpoint, the thickness ts of the shoulder portion 9C is preferably 1.1 times or more and 1.2 times or less than the thickness tc of the center portion 9A. Note that the shoulder portion 9C of the present embodiment shows a preferred mode in which the thickness gradually increases gradually toward the tread edge 2e. However, it is not limited to such an aspect.

  Further, the thickness tc of the center portion 9A may be appropriately set according to the tire size or the like. However, if it is too large, the temperature may extremely increase due to heat generation, and as a result, the durability may be decreased. If it is too small, the tire life may be shortened. From this point of view, the thickness tc of the center portion 9A is preferably 6.0 mm or more, preferably 10.0 mm or less, more preferably 8.0 mm or less.

  Furthermore, in the present invention, the loss compliance ratio, which is the ratio (LC70 / LC100) of loss compliance (LC70) at a temperature of 70 ° C. and loss compliance (LC100) at a temperature of 100 ° C., is constant for each of the rubber portions 9A to 9C. Regulated to range. Specifically, the loss compliance ratio RLc of the center portion 9A is 0.90 to 1.20, the loss compliance ratio RLm of the middle portion 9B is 0.90 to 1.30, and the loss compliance ratio RLs of the shoulder portion 9C. Is set to 1.10 to 1.50.

Here, the loss compliance is a ratio {E ″ / (E *) ² } of the loss elastic modulus E ″ to the square of the complex elastic modulus (E *). Here, the complex elastic modulus (E *) and the loss elastic modulus E ″ are measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho under the following conditions in accordance with the provisions of JIS-K6394. The loss compliance at a measurement temperature of 70 ° C. is LC70, and the loss compliance at a measurement temperature of 100 ° C. is LC100.
Initial strain: 10%
Amplitude: ± 2.5%
Frequency: 10Hz
Deformation mode: Tensile

  Therefore, the larger the loss compliance value, the larger the energy loss. As a result, the rubber tends to generate heat and has excellent grip performance. In addition, a rubber having a loss compliance ratio that is a ratio (LC70 / LC100) of loss compliance (LC70) at a temperature of 70 ° C. to loss compliance (LC100) at a temperature of 100 ° C. is higher than a temperature of 100 ° C. Excellent grip performance at 70 ° C. In other words, excellent grip performance can be exhibited at low temperatures. On the other hand, a rubber having a loss compliance ratio smaller than 1 can exhibit excellent grip performance at a temperature of 100 ° C. rather than a temperature of 70 ° C. In other words, excellent grip performance can be exhibited at high temperatures. Similarly, in comparison between the loss compliance ratios, a rubber having a large loss compliance ratio is excellent in grip performance at a relatively low temperature, and a rubber having a low loss compliance ratio is excellent in grip performance at a high temperature.

  As described above, in the tire 1 of the present embodiment, the middle portion 9B that has a large distortion during traveling and easily generates heat regardless of whether the vehicle is traveling straight or turning is formed with a small thickness. As a result, heat generation in the middle portion 9B is suppressed as compared with the conventional case, but the temperature is still relatively high in the tread rubber 9. For this reason, in the middle portion 9B, the loss compliance ratio RLm is set in a range including a smaller value than the shoulder portion 9C, that is, 0.90 to 1.30. Thereby, the grip performance in the middle part 9B which tends to become high temperature is ensured.

  If the loss compliance ratio RLm of the middle portion 9B exceeds 1.30, sufficient grip performance cannot be exhibited in the middle portion 9B that is relatively hot during traveling. On the contrary, when the loss compliance ratio RLm of the middle portion 9B is less than 0.90, the grip performance at a low temperature is remarkably lowered. From such a viewpoint, the loss compliance ratio RLm of the middle portion 9B is preferably 0.90 or more, more preferably 0.95 or more, and preferably 1.30 or less, more preferably 1.10 or less. It is desirable to be.

  In addition, the center portion 9A is always in contact with the road surface mainly when traveling straight, and may generate heat up to a temperature that is the same as or slightly lower than that of the middle portion 9B. For this reason, in this embodiment, the value of the loss compliance ratio RLc of the center portion 9A is set to a range substantially equivalent to that of the middle portion 9B, that is, 0.90 to 1.20. Accordingly, the grip performance is exhibited even in the center portion 9A that is relatively hot.

  If the loss compliance ratio RLc of the center portion 9A exceeds 1.20, sufficient grip performance cannot be exhibited at the center portion 9A that is relatively hot during traveling. On the contrary, when the loss compliance ratio RLc of the center portion 9A is less than 0.90, the grip performance at a low temperature is remarkably lowered. From such a viewpoint, the loss compliance ratio RLc of the center portion 9A is preferably 0.90 or more, more preferably 0.95 or more, and preferably 1.20 or less, more preferably 1.10 or less. desirable.

  On the other hand, although the shoulder portion 9C promotes heat generation by increasing the thickness, the temperature during traveling is relatively low. For this reason, the loss compliance ratio RLs is set to the shoulder portion 9C in a range including the largest value compared to the center portion 9A and the middle portion 9B, that is, 1.10 to 1.50. Therefore, the shoulder portion 9C can exhibit grip performance even in a relatively low temperature state.

  In addition, when the loss compliance ratio RLs of the shoulder portion 9C is less than 1.10, the shoulder portion 9C having a relatively low temperature cannot obtain sufficient grip performance. The grip performance is significantly reduced. From such a viewpoint, the loss compliance ratio RLs of the shoulder portion 9C is preferably 1.10 or more, more preferably 1.20 or more, and preferably 1.50 or less, more preferably 1.30 or less. desirable.

As described above, the tire 1 of the present embodiment regulates the thickness of the center portion 9A, the middle portion 9B, and the shoulder portion 9C, and defines the loss compliance ratio corresponding to the temperature distribution during traveling. Thus, it is possible to exhibit optimum grip performance while ensuring durability. In particular, among the tread rubber 9, the loss compliance ratio RLm of the middle portion 9B that is likely to be the highest temperature during traveling is minimized, and the loss compliance ratio RLs of the shoulder portion 9C that is likely to be the lowest temperature during traveling is the largest. In other words, by satisfying the following relationship (1), more optimal grip performance can be exhibited.
RLm <RLc <RLs (1)

  As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to illustrated embodiment, It can deform | transform and implement in a various aspect.

Motorcycle tires (size: 120 / 70ZR17) having the specifications shown in Table 1 were prototyped, and the grip performance and durability were evaluated by actual vehicle running tests. Each sample tire had the same specifications as follows except for the parameters listed in Table 1.
Rubber composition of center part, middle part and shoulder part: Ratio of center part development width W1 according to Table 2 to tread development width Tw: 30%
Ratio of middle part development width W2 to tread development width Tw: 15%
Ratio of shoulder width W3 to tread width Tw: 20%
The test method is as follows.

<Grip performance>
A tire is mounted on the rear wheel of a motorcycle under the following conditions, and the vehicle runs at a speed of 100 km / h to 150 km / h on a dry asphalt circuit course, and the maximum vehicle speed (about 280 km / h from 250 km / h). The grip level during straight traveling and cornering at that time was evaluated by a 10-point method based on the rider's sensory evaluation. The larger the value, the better.
Rims: 3.5 x 17
Internal pressure: 190 kPa
Vehicle displacement: 600cc

<Durability>
After the grip performance test, the damage condition of the tire was visually confirmed, and the conventional example was evaluated with an index of 100. The larger the value, the better.
Tables 1 and 2 show the test results.

  As a result of the test, it was confirmed that the motorcycle tire of the example can exhibit optimum grip performance and is excellent in durability.

It is sectional drawing which shows one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motorcycle tire 2 Tread part 2A Tread surface 2e Tread edge 9 Tread rubber 9A Center part 9B Middle part 9C Shoulder part

Claims (4)

A tire for a motorcycle in which a tread surface of the tread portion is convex outward in the tire radial direction and curved in an arc shape,
The tread rubber disposed in the tread portion includes a center portion disposed in a region of 25 to 35% of the tread deployment width centered on the tire equator, and 15 to 25% of the tread deployment width from the tread edge to the tire equator side. A shoulder portion disposed in the region of the middle portion, and a middle portion disposed in the region between the center portion and the shoulder portion,
The thickness tm of the middle part is 0.8 to 0.9 times the thickness tc of the center part, and the thickness ts of the shoulder part is 1.0 to 1.3 of the thickness tc of the center part. As well as
The center portion has a loss compliance ratio of 0.90 to 1.20, which is a ratio (LC70 / LC100) of loss compliance (LC70) at a temperature of 70 ° C. and loss compliance (LC100) at a temperature of 100 ° C., and A motorcycle tire characterized in that a loss compliance ratio of a middle portion is 0.90 to 1.30, and a loss compliance ratio of the shoulder portion is 1.10 to 1.50. The motorcycle tire according to claim 1, wherein the loss compliance ratio RLc of the center portion, the loss compliance ratio RLm of the middle portion, and the loss compliance ratio RLs of the shoulder portion satisfy the following relationship (1).
RLm <RLc <RLs (1)   3. The motorcycle tire according to claim 1, wherein a thickness ts of the shoulder portion is greater than 1.0 times and less than or equal to 1.3 times the thickness tc of the center portion.   The motorcycle tire according to claim 1 or 2, wherein the center portion has a thickness of 5.0 to 12.0 (mm).