JP2009051317A - Pneumatic tire for two-wheeled vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for a two-wheeled vehicle improved in lateral grip performance and also in the abrasion resistance of a tread shoulder, in a circuit where use frequencies of one side and the other side in the tire width direction of a tread are different. <P>SOLUTION: This tire 10 includes a carcass 14, a spiral belt 16, a crossing belt 17, and the tread 18 sequentially arranged outside a tire radial direction. Soft rubber parts 22, 23 having developed widths W1, W2 from a tread end T set within a range of 5-30% of a tread developed width L and lower Shore-A hardness than that of a center rubber part 26 are formed on at least tread sides of both sides in the tire width direction of the tread 18. The soft rubber part 22 is made different in at least one of the Shore A-hardness, a thickness and a developed width from those of the other soft rubber part 23. Thereby, the lateral grip performance can be improved, and the abrasion resistance of the tread shoulder S can be improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire for two-wheeled vehicles, and in particular, in a circuit having different usage frequencies on one side and the other side in the tire width direction of the tread portion, while improving the lateral grip property and improving the wear resistance of the tread shoulder portion. The present invention relates to an improved pneumatic tire for a motorcycle.

  Motorcycles have the feature of turning by tilting the vehicle body. Therefore, in a tire used for a motorcycle, a portion that contacts the road surface moves due to the inclination of the vehicle body when turning. In addition, the speed is high when the vehicle body is upright, and a force in the longitudinal direction of the vehicle body (the equator direction of the tire) is applied to the tire by the braking force and the driving force, but a large lateral force is mainly applied when the vehicle is tilted. Therefore, good lateral grip properties are required for the shoulder portion of the tire. In particular, in motorcycle racing tires that require speed, it is common to change the type of rubber at the tire center and tire shoulder.

  Also, in pneumatic tires for racing and competition motorcycles, rubber that does not generate heat easily is placed in the tire center part because the speed when traveling straight is very fast, or the tread center part has a two-layer structure that does not generate heat easily. Various measures have been taken, such as placing rubber and placing rubber with high grip performance on the outside (tread side of the tread).

  On the other hand, in the tire shoulder portion, since a large lateral force is required at the time of turning, a soft rubber with high grip performance is disposed. However, the tire shoulders generate heat during traveling, turning performance decreases with traveling, wear of the shoulders progresses, grip performance is lost, or rubber in the shoulders deteriorates due to heat generation. There's a problem. With respect to such a problem, Patent Documents 1 and 2 disclose a technique for solving the above problem by changing the rubber physical properties in the thickness direction of the tread portion.

  In general, when the dynamic elastic modulus (E ′), which is an index of the elastic modulus of rubber, is small as rubber characteristics, it means that the rubber is soft, and the soft rubber bites into the unevenness of the road surface, so that the grip performance is high. On the other hand, soft rubber has a characteristic of high wear rate. The softness of rubber can also be indicated by hardness, that is, Shore A hardness. Rubber with a small Shore A hardness is soft and has a high grip performance but a poor wear resistance.

  By the way, in a pneumatic tire for a motorcycle, since the motorcycle turns while tilting the vehicle body, the portion in contact with the road surface of the tread portion differs between when going straight and when turning. That is, the center part of the tread portion is in contact with the road surface when going straight, and the end side of the tread portion is in contact with the road surface when turning. In motorcycle competitions and races, lateral force (lateral grip force) during turning is particularly important. If the side grip force at the time of turning is sufficient, not only can the corner be turned at high speed, but also the straight (straight line) that follows the corner has a high speed of exiting the corner, so the initial speed is fast and the speed can be put even on a straight line. be able to. That is, if the lateral grip force of the tire can be increased, the lap time can be shortened in competitions and races.

  From the above, it is required to grip the tire in the lateral direction (width direction) during turning. In order to turn a motorcycle quickly, it is necessary to greatly depress the vehicle body in order to balance the centrifugal force that increases with the turning speed, and it is necessary to be able to grip the tire so that the centrifugal force can be countered. In other words, if the grip force of the tire when the vehicle body is largely tilted is insufficient, the vehicle cannot turn quickly, so the influence of the grip here on the turning performance is very large.

Among circuits where motorcycle racing is performed, there are circuits with different frequency of right turn and left turn. For example, in a clockwise circuit (clockwise circuit), there are many clockwise corners. Also, depending on the shape of the corner, there is a course in which a so-called high-speed corner that can turn at a high speed is only a right turn, and a low-speed corner at a low speed is only a left turn. Fast corners have high centrifugal force and tight input to the tires. For this reason, tire wear tends to proceed at the high-speed corner, and the rubber tends to generate heat because the tire rotation speed is high. Thus, depending on the circuit, the tire performance required for the right turn and the left turn may differ.
JP 2006-76355 A JP 2005-271760 A

  In consideration of the above facts, the present invention provides a motorcycle that improves lateral grip and improves wear resistance of a tread shoulder portion in a circuit in which the frequency of use on one side and the other side of the tread portion in the tire width direction is different. It is an object to provide a pneumatic tire for use.

  The present inventor conducted detailed research to improve the grip performance during turning when completing the present invention. In particular, we worked to intensively improve grip performance at a bank angle (camber angle) of 45 to 50 degrees where a motorcycle vehicle falls most. This is because, for example, in a race, the turning speed is very important, and if the turning speed is high, the speed on the straight next to the corner is also high, and as a result, the lap time is improved. Also, increasing the grip force when turning on general roads can contribute to safety.

  Then, the present inventor conducted the following examination on the turning performance when the vehicle body is largely tilted with a tire for a motorcycle.

  In a pneumatic tire for a motorcycle, with respect to turning performance when the vehicle body is largely tilted, the end of one side in the tire width direction of the tread portion of the tire is in contact with the road surface to generate a grip. When the vehicle is turned with the vehicle body largely tilted, the ground contact shape between the road surface and the tread portion is as shown in FIG. When the motorcycle body turns and turns, that is, when the tire camber angle (hereinafter referred to as CA) is in the range of 45 to 55 degrees, the tire tread width (full width) is almost ¼. The ground area is grounded. The grounded area is divided into three equal parts, and the areas A, B, and C are defined from the tread edge.

  Hereinafter, tread deformation in a cross section in the width direction of the tire will be examined. This is because a lateral force is generated in the tire due to the deformation of the tread portion. The deformation of the tread portion in the lateral direction (width direction) generates camber thrust (lateral force).

  FIG. 12 shows a cross section when the tire is grounded and rotating at 50 degrees CA. The shape of the grounding part is shown below the cross section. Depending on the dimensions of the tire and the like, the ground contact shape may be a shape in which a part of an ellipse is missing or a half moon shape (see FIG. 13).

  Described in the width direction deformation of the tread portion of the region B having the elliptical ground shape shown in FIG. The tread surface (tread surface), that is, the position in contact with the road surface at the center position in the tire width direction of region B is defined as Q point, and the deepest portion of the tread portion is defined as P point inside Q point. FIG. 12 shows the locus of the point P and the locus of the point Q at the time of rolling on the ground. Point P is a point where the tread portion is in contact with the belt (frame member) of the tire, and since the tire rolls with a CA attached thereto, the locus of point P draws a bow-like curve. On the other hand, since the point Q is fixed to the road surface when the tread surface of the tread portion contacts the road surface, it moves linearly in the direction of the road surface, that is, in the tire traveling direction. Accordingly, the locus of point Q draws a straight line.

  In this way, the tread portion undergoes lateral shear due to the difference between the locus of point P and the locus of point Q. It is just a relationship between bow and string, and receives the maximum amount of lateral shear directly under the load. Since the tread portion is deformed in the lateral direction (width direction) by this lateral shearing amount, lateral force (camber thrust) is generated. From such a camber thrust generation mechanism, the longer the contact length (circumferential length of the contact shape, that is, the length in the tire equator direction), the greater the difference in trajectory between points P and Q, and the tread portion is Receives a large shear force. When the contact length is short, the shear amount (lateral direction, that is, the shear amount in the tire width direction) received by the tread portion is small.

  As shown in FIG. 12, when the ground contact shape is elliptical, the lateral shear amount in the region B is the largest, the lateral shear amount in the region A is then large, and the lateral shear amount in the region C is small. In FIG. 12, the radius of rotation at the center of the region A is shown as RA, and the radius of rotation at the center of the region C is shown as RC. As shown in FIG. 13, when the ground contact shape is a half-moon shape, the region B and the region A receive a large amount of lateral shear, and the region C has a small amount of lateral shear. That is, in the turning at the time of the large CA where the CA is 45 degrees to 55 degrees, the area B and the area A are parts that greatly increase the lateral force.

  On the other hand, when the inclination angle (bank angle, CA) of the motorcycle is observed, the motorcycle cannot fall down when the CA is 45 degrees to 55 degrees or more. That is, the area A is an area that contacts the ground only when the motorcycle is tilted at the maximum angle. The region B is also used mainly when the motorcycle is greatly inclined. On the other hand, the area C is an area that is used particularly frequently when the bike is slightly tilted after the bike is largely tilted, that is, when CA is around 40 degrees. In other words, the area C is used in the process of tilting the motorcycle, is used when the motorcycle is further tilted, and is also used in the process of accelerating the motorcycle and standing upright. In particular, when considering a rear tire with high wear, this region C is a region that is used when the motorcycle is greatly defeated and accelerated from there, that is, the motorcycle often transmits a large driving force around CA 40 degrees. C can be said to be a region that frequently receives both the longitudinal drive input and the lateral input during acceleration. Therefore, this region C is a portion where the wear of the tread portion proceeds.

The areas A to C are summarized as follows.
Area A: Used only when the maximum CA (45 degrees to 55 degrees), and receives a lateral input. It greatly contributes to the generation of lateral grip force at the maximum CA (especially when the ground contact shape is a half-moon shape).
Area B: Used mainly at maximum CA (45 ° to 55 °). This greatly contributes to the generation of lateral grip force at the maximum CA (especially when the ground contact shape is elliptical). It is also grounded at the time of maximum CA or CA 40 degrees, and is used more frequently than area A.
Area C: Also used when the maximum CA (45 to 55 degrees). Further, it is used in the process of reaching the maximum CA, and particularly in the case of a rear tire, it is used mainly at the start of full-scale acceleration at CA 40 degrees, and thus becomes a part with severe wear. Compared with the area A and the area B, the frequency of use is clearly higher. Further, when CA is 40 degrees, it becomes the center of the grounding shape and the grounding length is extended, so that the amount of shear in the lateral direction is large and wear is severe.

If soft rubber is used for the tread portion in consideration of the characteristics of the rubber described above, the soft rubber tends to bite into the road surface and the grip (friction coefficient) increases. However, soft rubber has the property of high wear rate. For this reason, even if soft rubber is arranged in each of the areas A, B, and C to obtain an ideal grip, from the above characteristics, especially in the area C, soft rubber with severe wear is arranged. It is impossible to do.
However, if specializing in competitions and races, if either one of the right turn and the left turn is extremely severe and the other is not severe, one of the treads in the tire width direction It is desirable to change the rubber placement position between the side and the other side.

  Another characteristic may be due to the characteristics of the mechanism of camber thrust generation in pneumatic tires for motorcycles. The difference between the locus of point P and the locus of point Q shown in FIG. 12 is the amount of lateral deformation of the tread portion. This amount of lateral deformation is a constant displacement. That is, since this trajectory is determined by the tire geometry, the maximum amount of lateral shear is a constant amount. For example, in a normal tire, the amount of lateral shear in the region B at the time of large CA is about 7 mm. Therefore, regardless of whether the rubber in the tread portion is hard or soft, the transverse shear amount is a constant value of about 7 mm. That is, when the rubber of the tread portion is soft, the displacement is constant, so that the force for deforming the tread portion is small (that is, the generated lateral force (camber thrust) is small). On the contrary, if the rubber of the tread portion is hard, a large force is required to laterally deform the tread portion by a certain amount (that is, the generated lateral force increases). That is, the camber thrust (lateral force) largely depends on the rigidity of the tread portion (elastic modulus and hardness of the tread rubber).

  However, in reality, hard rubber is difficult to bite into fine irregularities on the road surface, and as a result, the friction coefficient is small and slippery. For this reason, if the rubber is too hard, the ground contact surface of the tread portion and the road surface slide, so that the amount of displacement is reduced and lateral force is not generated.

  The present inventor has conducted the above-described studies and repeated further experiments to further study and have completed the present invention.

  The pneumatic tire for a motorcycle according to claim 1, wherein at least one carcass, at least one belt disposed on the outer side in the tire radial direction of the carcass, and a tread disposed on the outer side in the tire radial direction of the belt. A pneumatic tire for a motorcycle having a width of 5 to 30% of the width of the tread, and at least on the tread surface side of the tread portion in the tire width direction. A soft rubber portion having a Shore A hardness lower than that of the center side rubber portion adjacent to the tire center side is formed, and one soft rubber portion has a Shore A hardness, a thickness, and a developed width as compared with the other soft rubber portion. It is characterized by at least one of them being different.

  In Claim 1, the area | region of a soft rubber part is prescribed | regulated using the expansion | deployment width | variety (periphery direction width | variety). Here, the developed width means a width when a part rounded in the width direction is developed so as to be linear or planar so that the arc is a straight line. Therefore, the tread deployment width (deployment width of the tread portion) is a width in a substantially arc direction along the outer periphery of the tread portion, and is an interval between tread ends in a state where the tread portion is deployed. Further, the developed width of the soft rubber portion is a width in a substantially arc direction along the outer periphery of the soft rubber portion.

The pneumatic tire for a motorcycle according to claim 1 stipulates that a soft rubber portion having a shore A hardness (soft) lower than the center-side rubber portion is formed on at least the tread side on both sides in the tire width direction of the tread portion. Yes.
In addition, the soft rubber portion has a development width from the tread end within a range of 5 to 30% of the tread development width. In addition, it is good also as a structure which arrange | positions a soft rubber part on the tread side at the tread end side, and arrange | positions the rubber part which consists of rubbers different from a soft rubber part inside, and is comprised so that a tread end side may be only a soft rubber part. May be.

  By the way, the soft rubber part is arranged on the tread part on the tread side. The soft rubber part softer than the center side rubber part bites into the fine irregularities of the aggregate such as asphalt, and the friction coefficient becomes high and the grip property is improved. Because. On the other hand, as described above, the lateral displacement amount of the tread shoulder portion of the pneumatic tire for a motorcycle is geometrically determined. If all the tread shoulder portion is made of a soft rubber portion, the shear rigidity of the tread shoulder portion is reduced. It decreases, and it becomes impossible to generate a large lateral force. Therefore, it is preferable to arrange the soft rubber portion only on the tread shoulder portion on the tread surface side.

  The Shore A hardness can be measured using a commercially available hardness meter. For example, after tread rubber is cut out and immersed in hot water at 100 ° C. for 30 minutes and the temperature of the rubber is set to 100 ° C., the hardness can be measured with a hardness meter. Usually, a material having a high hardness has a high dynamic elastic modulus.

  Although the softness is defined by the Shore A hardness in claim 1, it may be defined by using the dynamic elastic modulus (E '). The dynamic elastic modulus can be measured, for example, by adding a frequency of 15 Hz and a strain of 5% to a rubber sample with a sine wave and measuring the reaction force at that time. In this case, the dynamic elastic modulus may be measured at a temperature of 100 ° C., a frequency of 15 Hz, and a strain of 5% using a viscoelasticity measuring device manufactured by Rheometrics. In particular, in the case of motorcycle tires, the temperature of the tread shoulder may exceed 100 ° C. Therefore, the dynamic elastic modulus E ′ at 100 ° C. is measured according to the purpose, and the present invention is applied. It is good also as a dynamic elastic modulus. Although the temperature is not particularly defined in claim 1, it is preferable to use a dynamic elastic modulus of 50 ° C. for a general consumer tire, and a dynamic elastic modulus of 100 ° C. or higher is used for a racing tire. Is preferred.

  Next, the developed width of the soft rubber portion will be described. The reason for setting the development width of the soft rubber portion within the range of 5 to 30% of the tread development width is to include the range of the portion to be grounded at CA 45 degrees to 55 degrees. By disposing the soft rubber portion softer than the center-side rubber portion in this range, it is possible to increase the grip force during turning.

  Specifically, as described above with reference to FIG. 12, grounding at CA 45 to 55 degrees is an area where the development width from the tread edge is 25% of the tread development width. If the upper limit is set to 30%, a high lateral force can be obtained not only at 45 degrees CA but also at 40 degrees CA where the vehicle is raised slightly. More practically, as described above, when the region A, the region B, and the region C in FIG. 12 are separated, it is easy to place soft rubber in the region A, and the region B is placed next. Cheap. In the region C, traction is added and the frequency of use is high, so that soft rubber is easily worn and needs attention. For this reason, when a soft rubber is disposed in the region C, it is preferable to use it on the side where the frequency of use during turning is low.

  The lower limit is set to 5% because the effect of arranging the soft rubber portion is difficult to appear unless there is a development width of 5% or more.

  When the development width of the soft rubber part is less than 5% of the tread development width, the range in which the soft rubber part is arranged is too narrow even if the soft rubber part is arranged in the region A shown in FIG. Less effective. For this reason, it was 5% or more. When the development width of the soft rubber part exceeds 30% of the tread development width, it approaches the region used when standing upright, and the action is different from that of turning that requires lateral force (lateral grip force), which is inappropriate.

  Further, the center of contact of the tire at 40 degrees CA is the periphery of the region C in FIG. 12, and this region is a region of about 16% to 30% from the tread end with the tread end as a base point. If the soft rubber portion is disposed up to this region, there is a risk that the soft rubber portion will be worn early due to severe input during acceleration. For this reason, the soft rubber portion is disposed in this region when the frequency of use is low, when it is often used in a low-speed corner where the input during turning is small, or when the softening ratio is reduced.

  For example, when the soft rubber portion is disposed within a range of 30% of the tread development width from the tread end, the softening ratio of the soft rubber portion is 20% (when the hardness of the center rubber portion is 100%, When the soft rubber part is disposed within a range of 15% of the tread development width from the tread edge, the softening ratio is 30% (70% hardness). Furthermore, when the soft rubber portion is disposed only within a range of 10% of the tread development width from the tread edge, it is preferable to adjust the softening ratio to 40% (60% hardness).

  Next, an operation when the Shore A hardness of the soft rubber portion on one side in the tire width direction of the tread portion is different from the Shore A hardness of the rubber portion on the other side will be described.

In circuits where the frequency of use on one side and the other side in the tire width direction of the tread is different (that is, circuits where the frequency and input of the right turn and left turn are different), the less frequently used side than the more frequently used side By disposing the soft soft rubber portion, the merit of the present invention can be enjoyed in a balanced manner on one side and the other side in the tire width direction of the tread portion.
In other words, the side grip is improved by placing a very soft soft rubber part on the less frequently used side, and it is made resistant to wear by placing a soft rubber part made of slightly soft rubber on the frequently used side. Can do. And by determining the softness of the soft rubber part according to the usage frequency of the one side and the other side in the tire width direction of the tread part, the progress of the wear of the soft rubber part on the one side and the soft rubber part on the other side is progressed. It can be made uniform.

Here, when a very soft soft rubber part is arranged on both the one side and the other side in the tire width direction of the tread part, the less frequently used side is good, but wear on the frequently used side progresses early. In the second half of the race, you will not get proper grip.
If a soft rubber part is placed on both the one side and the other side in the tire width direction of the tread part, the frequently used side is good, but the grip side should be increased more on the less frequently used side. I can, but I can't make use of it.

  In addition, it is preferable to dispose a hard rubber portion having a Shore A hardness higher than that of the soft rubber portion or a low loss tangent rubber portion having a low loss tangent tan δ inside the soft rubber portion (inner side in the tire radial direction).

  Next, an operation when the thickness of the soft rubber portion on one side in the tire width direction of the tread portion is different from the thickness of the rubber portion on the other side will be described.

  As described above, when the tread shoulder portion has a plurality of rubber layers (for example, two layers), the soft rubber portion is uneven on the road surface by making the tread side softer than the center side rubber portion. However, if the entire tread shoulder is softened, it will be easily worn, and the soft rubber will reduce the tread rigidity and the lateral grip. It is preferable to dispose a hard rubber part (a rubber part having a Shore A hardness higher than that of the soft rubber part) on the inner side.

  Here, when the hard rubber portion is arranged inside the soft rubber portion, by changing the thickness of the soft rubber portion on one side of the tread portion in the tire width direction and the thickness of the soft rubber portion on the other side, The shear rigidity of the rubber (tread rubber) forming the tread portion can be changed. When the thickness of the soft rubber portion is thin, the shear rigidity of the tread portion is increased, and it is possible to withstand strong lateral input. That is, it has excellent wear resistance. On the other hand, when the thickness of the soft rubber part is thick, the wear speed is fast, but the grip force is strong. Further, since the soft rubber part softer than the center side rubber part is more distorted and more likely to generate heat, the tread rubber tends to generate heat more easily if the soft rubber part is thicker.

  From the above, on the tire width direction one side and the other side of the tread portion where the frequency of use is high, the thickness of the soft rubber portion is reduced to increase the rigidity of the tread portion and to be resistant to wear. On the side where the usage frequency is low, the side where the usage frequency is low gives the grip strength priority by increasing the thickness of the soft rubber portion. Here, since the low usage frequency is low, the soft rubber portion is likely to be worn, so that the progress of wear can be adjusted to the same level as the high usage frequency side. Furthermore, since the soft rubber part generates high heat, the temperature of the tread part can be increased even if the frequency of use is low. The temperature of the tread portion is raised because the tread rubber used in the race is designed to improve the grip when the temperature becomes high. This tread rubber is sufficient if it does not reach a high temperature of about 100 ° C. This is because a sufficient grip force cannot be obtained.

Further, if hard rubber is disposed on the side where the frequency of use is low, since the distortion of the rubber is small and the heat generation is small, the tread rubber does not easily reach a high temperature. On the other hand, if the soft rubber part is arranged on the frequently used side, heat is generated immediately, and the tread temperature becomes 100 ° C. or higher.
In particular, when soft rubber is used under severe input conditions that are frequently used for a long time, bubbles are formed inside the rubber, and a so-called blow phenomenon occurs in which the rubber is destroyed starting from the bubbles. From this point of view, the soft rubber part on the frequently used side is thin to suppress heat generation, and the soft rubber part on the infrequently used side is thickened to increase the grip power and reduce input. It is effective to make the tread portion easily generate heat. Therefore, such characteristics can be easily adjusted by changing the thickness of the soft rubber portion on one side in the tire width direction of the tread portion and the thickness of the soft rubber portion on the other side.

  Next, an operation when the development width of the soft rubber portion on one side in the tire width direction of the tread portion is different from the development width of the rubber portion on the other side will be described.

  Depending on the frequency of use of one side and the other side of the tread portion in the tire width direction, for example, when the usage frequency is very high, the soft rubber portion is arranged only in the above-mentioned contact-shaped region A, and the region B or region By disposing a tire center side rubber portion harder than the soft rubber portion (having a higher Shore A hardness) in C, it is possible to suppress wear in the regions B and C.

  Further, when the usage frequency is slightly high, the soft rubber portions are arranged in the region A and the region B. When the frequency of use is low, it is possible to maximize the grip force by arranging the soft rubber portion in the areas A to C. In a circuit where the frequency of use of one side and the other side of the tread portion in the tire width direction is different, it is possible to arrange the rubber of the tread portion according to the usage frequency of the one side and the other side in consideration of input during turning. This eliminates the imbalance of wear on both tread shoulders due to inputs during turning, increases the development width of the soft rubber part on the less frequently used side, making it easier to heat the rubber with less input, and also gripping power You can earn the maximum amount.

  From the above, the pneumatic tire for a motorcycle according to claim 1 can improve the lateral grip property in a circuit having different usage frequencies on one side and the other side in the tire width direction of the tread portion, and can also improve the tread shoulder portion. It is possible to improve the wear resistance.

  The pneumatic tire for a motorcycle according to claim 2, wherein at least one carcass, at least one belt disposed on the outer side in the tire radial direction of the carcass, and a tread disposed on the outer side in the tire radial direction of the belt. A pneumatic tire for a motorcycle including a portion, wherein the development width from the tread end is within a range of 5 to 30% of the tread development width only on one side in the tire width direction of the tread portion, and on the tire center side A soft rubber portion having a Shore A hardness lower than that of the center-side rubber portion adjacent to is formed on at least the tread surface side.

  The pneumatic tire for a motorcycle according to claim 2 is soft only on one side (one side) of the tread portion, when the frequency of use during turning is extremely different on one side and the other side in the tire width direction of the tread portion. It was specified that the rubber part was arranged and the soft rubber part was not arranged on the other side. Thereby, since the soft rubber part is not disposed on the other side, the wear resistance performance can be prioritized. That is, the soft rubber portion is not arranged on the side where the usage frequency is high. On the other hand, a soft rubber portion is arranged on the side where the frequency of use is low. The less frequently used side is less frequently used and therefore wears less. For this reason, it is possible to gain grip power by mounting the soft rubber portion, and to quickly generate the tread rubber with a small amount of input, and to reach an appropriate temperature.

  The pneumatic tire for a motorcycle according to claim 3 is the pneumatic tire for a motorcycle according to claim 1 or 2, wherein the development width of the soft rubber portion gradually increases from the tread surface toward the inner side in the tire radial direction. It is characterized by spreading.

  The pneumatic tire for a motorcycle according to claim 3 stipulates that the development width gradually increases from the tread surface side toward the inner side in the tire radial direction so that the exposed area increases as the soft rubber portion wears. did. This is because when the tire tread portion is worn, the thickness of the tread portion is reduced, so that the tread rigidity is increased, the tread surface is easily slid from the road surface, and the grip force tends to decrease. Therefore, the grip force can be supplemented by increasing the exposure of the soft rubber portion. Especially for racing tires, it is important to maintain the grip of the tire even if the race progresses and the number of laps is repeated. With this configuration, even if the tread portion wears out, the soft rubber portion As the exposure range increases, the area with a high friction coefficient increases and the grip force can be maintained. The configuration as claimed in this claim may be utilized on both tread end sides, or may be utilized only on one tread end side.

  The pneumatic tire for a motorcycle according to claim 4 is the pneumatic tire for motorcycle according to any one of claims 1 to 3, wherein the thickness of the soft rubber portion is an average thickness of the tread portion. It is characterized by being in the range of 20% to 100%.

  In the pneumatic tire for a motorcycle according to claim 4, the thickness of the soft rubber portion is defined in comparison with the average thickness of the tread portion. Here, the thickness of the soft rubber portion is preferably 20% or more. If it is less than 20%, the thickness of the soft rubber portion is too thin, and even if the soft rubber portion is soft, it is difficult to bite into the unevenness of the road surface. Further, there is a concern that the soft rubber portion will be worn out immediately. The maximum thickness of the soft rubber part is 100%.

  Further, although depending on the characteristics of the soft rubber part, when the soft rubber part is made of a very soft rubber, the thickness of the soft rubber part is preferably 80% or less. As mentioned earlier, the lateral displacement of the tread shoulder of a motorcycle is geometrically determined, and if all the tread shoulder is softened, the shear rigidity of the tread will be reduced and a large lateral force can be generated. Because it disappears.

  The pneumatic tire for a motorcycle according to claim 5 is the pneumatic tire for a motorcycle according to any one of claims 1 to 4, wherein at least a part of the tread center portion of the tread portion includes two types. It is characterized by being formed by laminating the above rubber layers.

  In the pneumatic tire for a motorcycle according to claim 5, it is defined that at least a part of the tread center portion is formed by laminating two or more kinds of rubber layers. In addition, a tread center part is the center part of a tread part, The expansion | deployment width | variety is 25% of a tread expansion | deployment width | variety. This is because the developed width of the portion in contact with the road surface when the motorcycle is upright is about 25% of the tread developed width. Here, even if the entire region of the tread center portion (about 25% of the tread deployment width) is not two layers, at least the most, specifically, 15% of the tread deployment width of the tread center portion. It is effective if there are two layers with the above width.

The reason why the tread center part is made of two layers is to suppress the heat generation of the tread rubber. If hard rubber is arranged inside the tread portion and soft rubber is arranged outside (tread side), the external soft rubber gains a grip and the internal rubber suppresses heat generation. Further, if a rubber having a low loss tangent (tan δ) is used as the internal rubber, heat generation of the rubber can be further suppressed. Among racing tires, there is also a motorcycle competition that travels at a speed exceeding 300 km / h when traveling straight ahead. In such a competition, the tread portion repeatedly undergoes deformation at a high frequency from high speed running and generates heat. Due to the heat generation, a blow phenomenon occurs in which the oil inside the tread portion is vaporized and bubbles are generated, and a failure may occur in which a part of the tread portion is chipped and scattered from the bubbles. For this reason, in such advanced racing tires, it is preferable to arrange rubber with a very low loss tangent that does not easily generate heat inside the tread portion, while using rubber with a high grip on the tread surface side.
Here, according to the pneumatic tire for a motorcycle according to claim 5, not only the large CA of 45 to 55 degrees CA, but also the driving and braking characteristics at the time of straight traveling can be improved.

  The pneumatic tire for a motorcycle according to claim 6 is the pneumatic tire for a motorcycle according to claim 5, wherein the center-side rubber portion forms an outermost rubber layer of the tread center portion. It is said.

  In the pneumatic tire for a motorcycle according to claim 6, it is specified that the center-side rubber portion forms the outermost rubber layer of the tread center portion. By doing so, it is possible to reduce the number of rubber types forming the tread portion, which is efficient.

  The pneumatic tire for a motorcycle according to claim 7 is the pneumatic tire for a motorcycle according to claim 5 or 6, wherein the innermost rubber layer of the tread center portion is at least a part of the soft rubber portion. It is characterized by extending in the tire width direction until it overlaps.

  The pneumatic tire for a motorcycle according to claim 7 stipulates that the innermost rubber layer of the tread center portion extends in the tire width direction until it overlaps at least a part of the soft rubber portion. For example, if the innermost rubber layer of the tread center portion is made of rubber that is less likely to generate heat than the outermost rubber layer, this will place a soft rubber portion on the tread shoulder and heat generation will increase. Even so, since there is rubber that does not easily generate heat inside the tread portion, the amount of heat generation can be controlled to prevent the tread shoulder portion from blowing.

  The innermost rubber layer of the tread center portion of the pneumatic tire for a motorcycle according to claim 7 may be widely present only on one side of both sides of the tread portion in the tire width direction. If the innermost rubber layer is widely arranged only on the frequently used side, the heat resistance on the frequently used side can be improved and blow failure can be prevented.

  The pneumatic tire for a motorcycle according to claim 8 is the pneumatic tire for a motorcycle according to any one of claims 1 to 7, wherein the at least one belt is 5 in the tire equator direction. It features a spiral belt with a cord angle of less than 1 degree.

  The pneumatic tire for a motorcycle according to claim 8 stipulates that a spiral belt is used for the tire belt. A spiral belt is a belt that includes a cord having an angle of 0 to 5 degrees with respect to the equator direction, and a continuous body in which one or more cords are coated with unvulcanized rubber is continuously formed along the tire circumferential direction. It can be formed by spiral winding. Since such a belt has a cord extending in the circumferential direction, the tire is difficult to expand due to centrifugal force, and is particularly excellent in steering stability performance at high speeds. Therefore, it has come to be widely used in recent high-performance tires. However, such a member is effective for steering stability performance during high-speed driving, but the speed is slow at CA 45 to 55 degrees when the vehicle body is greatly tilted, so that the effect of difficult centrifugal expansion is diminished and the lateral grip force is reduced. Is not much different from conventional tires without spiral belts. Therefore, it is preferable to apply the present invention to such a high-performance tire because the lateral grip force at the time of large CA is increased and the performance balance as a high-performance tire is improved.

  The pneumatic tire for a motorcycle according to claim 9 is the pneumatic tire for a motorcycle according to claim 8, wherein the development width of the spiral belt is in the range of 60% to 90% of the tread development width. It is a feature.

  In the pneumatic tire for a motorcycle according to claim 9, the development width of the spiral belt is defined. The developed width of the spiral belt is a width in a substantially arc direction along the outer periphery of the spiral belt.

  FIG. 12 shows the behavior of the tread portion in the tire width direction cross section when the tire turns at 50 degrees CA. On the other hand, the deformation in the circumferential direction of the tread portion also occurs in the region A, the region B, and the region. C is different. This is because the belt speed is different between the area C near the ground-shaped tire center and the area A near the tread edge of the ground-shaped.

  A pneumatic tire for a motorcycle has a large roundness in a cross section in the tire width direction. For this reason, the area C is larger in the area A and the area C in terms of the belt radius, which is the distance from the rotating shaft to the belt. That is, the radius RC is larger than the radius RA. This means that the speed of the belt, that is, the belt speed from when the tread portion comes into contact with the road surface until the tire advances and the tread portion moves away from the road surface is higher in the region C. This is because the belt radius is obtained by multiplying the belt radius by the rotational angular velocity of the tire, and the rotational speed of the tire is the same in both the region A and the region C. Due to the speed difference in the circumferential direction of the belt, the tread portion is in the driving state in the region C near the center of the tire, and the braking state is in the region A near the tread end of the tire.

  Driving is when the tire is cut in a circle along the tire equator direction (circumferential direction), the deformation of the tread portion is caused by the inner surface of the tread portion (the surface in contact with the skeleton member inside the tire) being rearward in the tire traveling direction. This is a shear state in which the tread surface that is sheared by the ground and touches the road surface is deformed forward in the tire traveling direction, and is a deformation that occurs when a driving force is applied to the tire. On the other hand, braking is the reverse of driving, and the deformation of the tread portion is a sheared state where the tire inner side (belt) is sheared forward and the tread tread that is in contact with the road surface is deformed rearward and braked. When the tires move. The deformation of the tread portion in the circumferential direction occurs only when the tire rolls in an idle state without receiving driving force or braking force. Due to the shear deformation in the circumferential direction, the tread surface easily slips from the road surface in the region A and the region C, and wear progresses.

  Here, when the development width of the spiral belt as in claim 9 is used, the spiral belt is not disposed in the region A of FIG. As a result, the belt in the region A can extend in the circumferential direction at the grounded portion. Since the spiral belt is wound along the circumferential direction, the belt does not stretch in the circumferential direction when the spiral belt is present, but without the spiral belt, only the angled belt can be stretched in the circumferential direction. it can. The belt in the region A extends as it rotates and then contacts the road surface. As the belt stretches, the belt speed is accelerated by the stretch of the belt. Therefore, the belt speed in the region A is increased, the difference from the belt speed in the region C is reduced, the driving deformation in the region C and the braking deformation in the region A are decreased, and the tread tread becomes less slippery from the road surface. Improved.

  Further, since the soft rubber portion is disposed in the tread shoulder portion, the soft rubber portion is easily worn. However, according to the ninth aspect, the wear resistance can be improved and the wear can be improved.

  The development width of the spiral belt was set to 60% to 90%. In FIG. 12, the grounding width of the grounding shape is an area of 25% of the tread portion, and the width of the grounding center is 75%. Therefore, it is ideal that the development width of the spiral belt is 75%. However, even if it is not exactly 75%, the effect can be obtained if it is 60% or more and 90% or less. If it exceeds 90%, the spiral belt is also disposed in the region A, and the effect that the skeleton member (belt) in the region A extends in the circumferential direction is reduced. If it is less than 60%, there will be no spiral belt in the region C, and even if the belt in the region A extends in the circumferential direction, the belt in the region C also extends in the circumferential direction. Cannot be obtained.

  A more preferable range of the development width of the spiral belt is 66% or more and 84% or less. As described above, the ground contact width in FIG. 12 is 25% of the tread developed width, and when the ground contact width is equally divided into the region A, the region B, and the region C, the region becomes approximately 8%. The developed width of the spiral belt is set around 75%, which is the center in the tire width direction of the ground contact shape. If it is 84% or less, the portion where the spiral belt is not disposed is an area of 8% from the tread edge, and there is no spiral belt in the area A of FIG. Therefore, the belt extends reliably in the circumferential direction in the region A.

  If the development width of the spiral belt is 66% or more of the tread development width, the spiral belt surely exists in the region C. Therefore, the area C cannot be extended, and the area A is extended. With such a configuration, it is possible to reliably make a difference in belt elongation between the region A and the region C, reduce the belt speed of the tread portion in the region A and the region C, and waste the tread portion in the circumferential direction. Can be suppressed. In addition, since the spiral belt always exists in the region C, at least the region C exhibits a tagging effect even during high-speed rolling, and the steering stability performance can be ensured to a minimum.

  As described above, the pneumatic tire for a motorcycle according to the present invention can improve the lateral grip performance on the circuit where the frequency of use on the one side and the other side of the tread portion is different, and the tread shoulder portion can be improved. It has an excellent effect that the wear resistance can be improved.

  Hereinafter, a pneumatic tire for a motorcycle will be cited as an embodiment, and an embodiment of the present invention will be described. In the second and subsequent embodiments, the same components as those already described are denoted by the same reference numerals, and description thereof is omitted.

[First Embodiment]
First, the first embodiment will be described. As shown in FIG. 1, a pneumatic tire 10 for a motorcycle according to the present embodiment (hereinafter simply referred to as a tire 10) includes a pair of left and right bead portions 12 and a toroid shape from one bead portion 12 to the other bead portion 12. And at least one carcass 14 extending in the direction.

(Carcass)
Although the carcass 14 is omitted in FIGS. 1 and 2, two carcasses 14 are arranged. In addition, two end portions of the carcass 14 are sandwiched from both sides (the tire inner side and the outer side) by a bead wire 13 that forms the bead core 11 in the bead portion 12 and are locked to the bead core 11. In other embodiments, two end portions of the carcass 14 may be collectively wound around the bead core 11 from the tire inner side to the tire outer side and fixed.

  Further, the carcass 14 is formed by embedding a plurality of radially extending cords (for example, organic fiber cords such as nylon) in parallel in the covering rubber, and in this embodiment, a tire equatorial plane (tire center). The angle of the cord with respect to the tire equatorial plane CL on CL is set to 90 degrees. In this embodiment, the cord of the carcass 14 is made of nylon (“Nylon” is a registered trademark of DuPont) having a diameter of 0.6 mm, and 65 cords are driven into the carcass 14. / 50mm.

(Spiral belt)
A spiral belt 16 is disposed on the outer side in the tire radial direction of the crown portion of the carcass 14. This spiral belt 16 is a rubber-coated cord member in which one or a plurality of cords (for example, organic fiber cords such as Kevlar) are arranged in parallel and embedded in the covering rubber, and the angle of the cord is on the tire equatorial plane CL. On the other hand, it is spirally wound so as to form an angle of 5 degrees or less.

In this embodiment, the cord of the spiral belt 16 is made of twisted fiber of aromatic polyamide (trade name “Kevlar”) to a diameter of 0.7 mm, and the cord is driven at 50/50 mm. Is set. In another embodiment, the cord of the spiral belt 16 may be a steel cord in which a steel single wire having a diameter of 0.21 mm is twisted in a 1 × 3 type. When this steel cord is used, the cord is driven. It is preferable to set the interval to 30/50 mm.
Further, in the present embodiment, as shown in FIG. 1, the development width of the spiral belt 16 and the tread development width L are substantially the same.

(Intersection belt)
An intersecting belt 17 formed by laminating two belt plies is disposed outside the spiral belt 16 in the tire radial direction. This belt ply is formed by arranging a plurality of cords (organic fiber cords having a diameter of 0.7 mm by twisting aromatic polyamide fibers) in parallel and embedded in a covering rubber. Further, the two belt plies are laminated so that the angles of the cords with respect to the tire equatorial plane CL are opposite to each other, and in this embodiment, the angle of the cord with respect to the tire equatorial plane CL is set to 50 degrees. Has been. In this embodiment, the cord driving distance between the two belt plies is set to 30/50 mm.
Further, as shown in FIG. 1, the belt ply disposed on the inner side in the tire radial direction of the crossing belt 17 is denoted by reference numeral 17A, and the belt ply disposed on the outer side in the tire radial direction is denoted by reference numeral 17B. In the present embodiment, the development width of the belt ply 17A is set wider than the development width of the belt ply 17B.

(Tread part)
As shown in FIGS. 1 and 2, a tread portion 18 is disposed on the outer side of the cross belt 17 in the tire radial direction.
The tread portion 18 includes a soft rubber portion 22 disposed on the tread end T side on the one side in the tire width direction (left side in FIG. 1) and at least on the tread surface side, and the other side in the tire width direction (see FIG. 1). On the tread end T side on the right side) and at least on the tread side, adjacent to the tire radial direction outside of the soft rubber portion 22 and the soft rubber portion 22 and the soft rubber portion 23 and adjacent to the tire equatorial plane CL side And a low-loss tangent rubber portion 28 that is adjacent to the outer side in the tire radial direction of the spiral belt 16 and that extends to both sides in the tire width direction across the tire equatorial plane CL. Has been.

  The soft rubber portion 22 has a development width W1 from one tread end T within a range of 5 to 30% of a tread development width L (twice the development width from the tire equatorial plane CL to the tread end T), and The Shore A hardness is set lower than that of the center-side rubber portion 26. In addition, the thickness H1 of the soft rubber portion 22 is preferably in the range of 20 to 100% of the average thickness of the tread portion 18.

  The soft rubber portion 23 has a development width W2 from the other tread end T within a range of 5 to 30% of a tread development width L (twice the development width from the tire equatorial plane CL to the tread end T), and The Shore A hardness is set lower than that of the center-side rubber portion 26. In addition, the thickness H2 of the soft rubber portion 23 is preferably in the range of 20 to 100% of the average thickness of the tread portion 18.

  As shown in FIG. 1, the center-side rubber portion 26 forms the outermost layer of the tread center portion C. Accordingly, the center side rubber portion 26 is interposed between the soft rubber portion 22 and the low loss tangent rubber portion 28. The tread center portion C is a region extending in the tire width direction around the tire equatorial plane CL, and the development width of this region is 25% of the tread development width L. Further, the tread shoulder portion S is a region from the end of the tread center portion C in the tire width direction to the tread end T.

  The low-loss tangent rubber portion 28 constitutes the innermost layer of the tread center portion C, and both end portions in the tire width direction extend to both tread shoulder portions S. The low loss tangent rubber portion 28 has a loss tangent set lower than that of the soft rubber portion 22 and the center rubber portion 26, and the thickness gradually decreases from the tire equatorial plane CL to the tread end T.

  In the present embodiment, the tread portion 18 is not provided with a groove, but a drainage groove may be provided. Further, the tread surface (or simply the tread surface) of the present embodiment refers to a surface that contacts the road surface of the tread portion.

In this embodiment, the Shore A hardness M1 of the soft rubber portion 22 is different from the Shore A hardness M2 of the soft rubber portion 23, and the Shore A hardness of the soft rubber portion 23 is greater than the Shore A hardness M1 of the soft rubber portion 22. M2 is set to be low.
Furthermore, the Shore A hardness M1 is preferably in the range of 50% to 90% of the Shore A hardness M0 of the center side rubber portion 26, and the Shore A hardness M2 is in the range of 40% to 80% of the Shore A hardness M0. It is preferable to be inside.
The thickness H1 of the soft rubber portion 22 and the thickness H2 of the soft rubber portion 23 are set to be the same, and the development width W1 of the soft rubber portion 22 and the development width W2 of the soft rubber portion 23 are set to be the same. Yes.

Next, the operation of the first embodiment will be described.
In the tread portion 18, the Shore A hardness M1 of the soft rubber portion 22 is lower than the Shore A hardness M0 of the center side rubber portion 26, and the Shore A hardness M2 of the soft rubber portion 23 is lower than the Shore A hardness M0. The lateral grip at the time is improved. As a result, when running on a circuit with a motorcycle equipped with the tire 10, the corner can be turned at a high speed, and the straight following the corner also has a fast corner escape speed. Speed can be put. As a result, the lap time can be shortened. Therefore, the tire 10 is excellent in turning performance (steering stability performance).

Further, when running on a circuit configured such that the use frequency of one side of the tread portion 18 in the tire width direction is high and the use frequency of the other side is low, the soft rubber portion 22 is provided on the high use side. Since the soft rubber portion 23 is arranged on the side where the usage frequency is low, the side grip performance is improved on the side where the usage frequency is low, and the usage frequency is high on the side where the usage frequency is high. More resistant to wear than the lower side.
Furthermore, by determining the Shore A hardness of each of the soft rubber portion 22 and the soft rubber portion 23 according to the frequency of use of one side and the other side in the tire width direction of the tread portion 18 in the circuit, the soft rubber portion 22 and The progress of wear with the soft rubber portion 23 can be made uniform.

  From the above, the tire 10 can improve the lateral grip and improve the tread shoulder portion S in a circuit configured such that the frequency of use on one side and the other side of the tread portion 18 in the tire width direction is different. It is possible to improve the wear resistance.

  Further, the development widths W1 and W2 of the soft rubber portions 22 and 23 are within the range of 5 to 30% of the tread development width L, and the upper limit is 30%. In addition to the region where the development width from the top is 25% of the tread development width L), and a region where the ground contacts at 40 degrees CA, a high lateral force can be obtained even when the vehicle body is raised slightly. The lower limit is set to 5% because the effect of disposing the soft rubber portions 22 and 23 hardly appears unless there is a development width of 5% or more. Further, when the upper limit of 30% is exceeded, the region is close to the region used when standing upright, so that the action differs from that during turning that requires a lateral grip force, which is inappropriate.

  The thicknesses H1 and H2 of the soft rubber portions 22 and 23 are preferably 20 to 100% of the average thickness of the tread portion 18, respectively. This is because if the thicknesses H1 and H2 are less than 20%, the thicknesses H1 and H2 are too thin, so that even if the soft rubber portions 22 and 23 are soft, the center side rubber portion 26 on the inner side in the tire radial direction is harder than that. It is difficult to bite into the uneven surface of the road. Further, there is a concern that the soft rubber portions 22 and 23 are worn out immediately. The maximum thicknesses H1 and H2 of the soft rubber portions 22 and 23 are 100%.

  Since the low loss tangent rubber portion 28 having a lower loss tangent than the center side rubber portion 26 is disposed in the innermost layer of the tread center portion C, the tread is formed at the low loss tangent rubber portion 28 while gaining a grip at the center side rubber portion 26. Rubber heat generation can be suppressed. Note that the low-loss tangent rubber portion 28 is effective if provided in at least a region of 15% or more of the tread deployment width L in the tread center portion C.

In addition, since the center-side rubber portion 26 forms the outermost rubber layer of the tread center portion C, the number of rubber types forming the tread portion 18 can be reduced, which is efficient.
The provision of the spiral belt 16 on the tire 10 makes it difficult for the tire 10 to expand due to centrifugal force during traveling, and improves steering stability performance during high-speed traveling.
If the Shore A hardness M1 is greater than 90% of the Shore A hardness M0, the difference in hardness with the center side rubber portion 26 will be small, meaning that soft rubber will not be placed, and the effect of improving the lateral grip will be very small. Become. Further, if the Shore A hardness M2 is less than 40% of the Shore A hardness M0, the difference in Shore A hardness between the center side rubber portion 26 and the soft rubber portion 23 becomes too large, and there is a rigidity step at the boundary between these rubbers. This causes problems such as promoting the occurrence of uneven wear or causing cracks between the two. Furthermore, if the difference between the Shore A hardness M1 and the Shore A hardness M2 is less than 10%, the difference in performance between the left and right is less likely to appear. Accordingly, the lower limit of Shore A hardness M1 is preferably 10% higher than the lower limit of Shore A hardness M2, and the upper limit of Shore A hardness M2 is preferably 10% lower than the upper limit of Shore A hardness M1.
Accordingly, the Shore A hardness M1 is preferably in the range of 50% to 90% of the Shore A hardness M0, and the Shore A hardness M2 is preferably in the range of 40% to 80% of the Shore A hardness M0.

  In the present embodiment, a narrow unvulcanized rubber continuous body (rubber strip) made of unvulcanized rubber, at least part of the tread rubber, is automatically circumferentially and spirally formed using a dedicated molding machine. Molded by wrapping around. The tread shoulder portion S is molded in such a manner that the tire cross section is large in roundness. If the operator manually places a wide tread member on the tread shoulder portion S, it is difficult to ensure molding accuracy (shape accuracy). Because.

[Second Embodiment]
Next, a second embodiment will be described. As shown in FIG. 3, in the pneumatic tire 30 for a motorcycle according to the present embodiment (hereinafter simply referred to as the tire 30), the thickness H1 of the soft rubber portion 22 and the thickness H2 of the soft rubber portion 23 are compared with the first embodiment. And the thickness H2 of the soft rubber portion 23 is set to be thicker than the thickness H1 of the soft rubber portion 22. In the present embodiment, the Shore A hardness M1 of the soft rubber portion 22 and the Shore A hardness M2 of the soft rubber portion 23 are set to be the same, and the development width W1 and the development width W2 are set to be the same. .

Next, the operation of the second embodiment will be described. Note that the description of the same operation as that obtained in the first embodiment is omitted.
When running on a circuit similar to the first embodiment (a circuit configured such that the use frequency of one side of the tread portion 18 in the tire width direction is high and the use frequency of the other side is low). The soft rubber portion 22 is disposed on the side, the soft rubber portion 23 is disposed on the less frequently used side, and the center rubber portion 26 is adjacent to the inner side in the tire radial direction of the soft rubber portions 22 and 23. Since it is arranged, the shear rigidity of the tread shoulder portion S on the frequently used side is stronger than that on the less frequently used side and can withstand strong lateral input, that is, it is resistant to wear. On the other hand, the side grip force is improved on the low-use side than on the high-use side. Here, since the usage frequency is low on the side where the usage frequency is low, even if the soft rubber portion 23 is easily worn, the progress of wear can be adjusted to the same level as the usage frequency side. That is, the progress of wear of the soft rubber portion 22 and the soft rubber portion 23 can be made uniform.

  Further, when the soft rubber portion 22 is arranged on the side where the frequency of use is low, since the distortion of the rubber is small and the heat generation is small, the tread rubber does not easily reach a high temperature. On the other hand, if the soft rubber part 23 is disposed on the side where the frequency of use is high, heat is generated immediately, and the tread temperature becomes 100 ° C. or higher. When the soft rubber portion 23 is used under severe input conditions that are frequently used for a long time, bubbles are formed inside the rubber, and a so-called blow phenomenon occurs in which the rubber is destroyed starting from the bubbles. From this point of view, the thickness H1 of the soft rubber portion 22 is reduced to suppress heat generation, and the thickness of the soft rubber portion 23 is increased to increase the grip force and to make the tread portion 18 easily generate heat with less input. It is preferable.

  From the above, the tire 30 can improve the lateral grip performance in the circuit configured such that the frequency of use on one side and the other side of the tread portion 18 in the tire width direction is different, and the tread shoulder portion S. It is possible to improve the wear resistance.

[Third Embodiment]
Next, a third embodiment will be described. As shown in FIG. 4, in the pneumatic tire 40 for a motorcycle according to the present embodiment (hereinafter simply referred to as a tire 40), the deployment width W1 of the soft rubber portion 22 and the deployment of the soft rubber portion 23 are compared with the first embodiment. Unlike the width W2, the development width W2 of the soft rubber portion 23 is set wider than the development width W1 of the soft rubber portion 22. In the present embodiment, the Shore A hardness M1 of the soft rubber portion 22 and the Shore A hardness M2 of the soft rubber portion 23 are set to be the same, and the thickness H1 and the thickness H2 are set to be the same.

Next, the operation of the third embodiment will be described. Note that the description of the same operation as that obtained in the first embodiment is omitted.
When running on a circuit similar to the first embodiment (a circuit configured such that the use frequency of one side of the tread portion 18 in the tire width direction is high and the use frequency of the other side is low). Since the soft rubber portion 22 is arranged on the side and the soft rubber portion 23 is arranged on the low-use side, the ground contact area of the soft rubber portion is larger on the low-use side than on the high-use side. The grip force is improved and the contact area is widened, so the tread rubber can be easily heated with less input, and the grip force can be further increased. Further, since the ground contact area of the soft rubber portion is narrower on the side where the usage frequency is higher than on the side where the usage frequency is low, the wear of the tread shoulder portion S can be suppressed.
For this reason, by adjusting the development width W1 of the soft rubber portion 22 and the development width W2 of the soft rubber portion 23, it is possible to eliminate the wear imbalance of the tread shoulder portions S due to the input during turning.

  From the above, the tire 40 can improve the lateral grip performance and the tread shoulder portion S in a circuit configured so that the frequency of use on one side and the other side of the tread portion 18 in the tire width direction is different. It is possible to improve the wear resistance.

[Fourth Embodiment]
Next, a fourth embodiment will be described. As shown in FIG. 5, in the pneumatic tire 50 for a motorcycle according to this embodiment (hereinafter simply referred to as a tire 50), the soft rubber portion is provided only on the other side in the tire width direction of the tread portion 18 as compared with the first embodiment. 23, and the center-side rubber portion 26 is extended to the tread end T without the soft rubber portion 22 being arranged on one side.

Next, the operation of the fourth embodiment will be described. Note that the description of the same operation as that obtained in the first embodiment is omitted.
When running on a circuit similar to the first embodiment (a circuit configured such that the use frequency of one side of the tread portion 18 in the tire width direction is high and the use frequency of the other side is low). Since the center side rubber portion 26 is disposed on the entire side and the soft rubber portion 23 is disposed only on the less frequently used side, the side grip property is lower on the less frequently used side than on the less frequently used side. In addition to improving, the tread rubber can immediately generate heat even with a small amount of input, and the tread portion 18 can reach an appropriate temperature. On the other hand, since the center side rubber portion 26 is in contact with the road surface on the side where the usage frequency is high, it is more resistant to wear than the side where the usage frequency is low.

  From the above, the tire 50 can improve the lateral grip performance in the circuit configured such that the frequency of use on one side and the other side of the tread portion 18 in the tire width direction is different, and the tread shoulder portion S. It is possible to improve the wear resistance.

[Fifth Embodiment]
Next, a fifth embodiment will be described. As shown in FIG. 6, in the pneumatic tire 60 for a motorcycle according to the present embodiment (hereinafter simply referred to as the tire 60), the Shore A hardness M <b> 1 of the soft rubber portion 22 and the soft rubber portion 23 are compared with those of the first embodiment. Unlike the Shore A hardness M2, the thickness H1 and the thickness H2 are different, and the development width W1 and the development width W2 are different. The Shore A hardness M2 is set lower than the Shore A hardness M1, the thickness H2 is thicker than the thickness H1, and the development width W2 is set wider than the development width W1.

Next, the operation of the fifth embodiment will be described.
In the fifth embodiment, all of the actions obtained in the first to third embodiments can be obtained.

[Sixth Embodiment]
Next, a sixth embodiment will be described. As shown in FIG. 7, in the pneumatic tire 70 for a motorcycle according to the present embodiment (hereinafter simply referred to as the tire 70), the development widths W <b> 1 and W <b> 2 of the soft rubber portions 22 and 23 are larger than those in the first embodiment. The difference is that it gradually spreads from the tread side toward the inner side in the tire radial direction. FIG. 7 shows only the tread end T side where the soft rubber portion 22 is provided.

Next, the operation of the sixth embodiment will be described. Note that the description of the same operation as that obtained in the first embodiment is omitted.
As the wear of the tread portion 18 of the tire 70 progresses, the thickness of the tread portion 18 becomes thin and the tread rigidity increases, and the tread portion 18 tends to slip from the road surface, so that the grip force tends to decrease. According to the configuration of the present embodiment, as the wear progresses, the exposed areas of the soft rubber portions 22 and 23 increase, so that the grip force corresponding to the decrease can be compensated. In particular, it is important for a tire for competition to maintain the grip strength of the tire even if the race progresses and the number of laps is repeated. With such a configuration, even if the wear of the tread portion 18 progresses, the soft rubber Since the exposed range of the portions 22 and 23 increases, the region with a high friction coefficient increases and the grip force can be maintained over a long period of time.

In the present embodiment, the development widths W1 and W2 of the soft rubber portions 22 and 23 are gradually widened from the tread side toward the inner side in the tire radial direction, but the present invention is limited to this configuration. However, only the soft rubber portion 22 may gradually expand from the tread side toward the tire radial direction inner side, and only the soft rubber portion 23 may gradually expand from the tread side toward the tire radial inner side. It is also possible to use a configuration with
In addition to the first embodiment, the configuration of the present embodiment may be applied to any of the second to fifth embodiments. In addition, in 4th Embodiment, it shall apply only to the soft rubber part 23. FIG.

[Seventh Embodiment]
Next, a seventh embodiment will be described. As shown in FIG. 8, the pneumatic tire 80 for a motorcycle according to the present embodiment (hereinafter simply referred to as a tire 80) has a different rubber structure on the tread end T side compared to the first embodiment. In the present embodiment, the inner side in the tire radial direction of the soft rubber portion 23 is adjacent to the cross belt 17, and the tire center side is adjacent to the center side rubber portion 26. In FIG. 8, only the tread end T side where the soft rubber portion 23 is provided is shown.

Next, the operation of the seventh embodiment will be described. Note that the description of the same operation as that obtained in the first embodiment is omitted.
In the case of traveling on the same circuit as the first embodiment (a circuit configured such that the use frequency on one side of the tread portion 18 in the tire width direction is high and the use frequency on the other side is low), the use frequency is low. Since the soft rubber portion 23 is arranged on the side, the tread portion 18 can be effectively heated with a small amount of input.

In the present embodiment, the soft rubber portion 23 is arranged so that the inner side in the tire radial direction is adjacent to the crossing belt 17 and the tire center side is adjacent to the center side rubber portion 26. However, the configuration may be such that the inner side in the tire radial direction of the soft rubber portion 22 is adjacent to the crossing belt 17 and the tire center side is adjacent to the center-side rubber portion 26. Both the soft rubber portion 23 and the soft rubber portion 23 may be configured to apply the configuration of the present invention.
In addition to the first embodiment, the configuration of the present embodiment may be applied to any of the second to sixth embodiments. In the embodiment having the configuration in which the thicknesses H1 and H2 of the soft rubber portions 22 and 23 of the second embodiment are different, the configuration of the present invention is applied to the soft rubber portion 22 or the soft rubber portion 23. Only one of them. In the embodiment having the configuration in which the soft rubber portion 23 is disposed only on the other side of the tread portion 18 as in the fourth embodiment, the application of the configuration of the present invention is only the soft rubber portion 23.

[Eighth Embodiment]
Next, an eighth embodiment will be described. As shown in FIG. 9, the pneumatic tire 90 for a motorcycle according to this embodiment (hereinafter simply referred to as a tire 90) has a different rubber structure on the tread end T side compared to the first embodiment. In the present embodiment, both ends in the tire width direction of the low-loss tangent rubber portion 28 extend to the inside in the tire radial direction of the respective regions where the soft rubber portions 22 and 23 are arranged, and overlap with each other via the center-side rubber portion 26. Yes. FIG. 9 shows the tread end side where the soft rubber portion 22 is provided.

Next, the operation of the eighth embodiment will be described. Note that the description of the same operation as that obtained in the first embodiment is omitted.
Since both end portions in the tire width direction of the low-loss tangent rubber portion 28 extend to the inside in the tire radial direction of the respective regions where the soft rubber portions 22 and 23 are arranged, heat generation of the soft rubber portions 22 and 23 occurs. Even if it becomes larger, the low loss tangent rubber portion 28 controls the amount of heat generation, and the tread shoulder portion S can be prevented from blowing.

In the present embodiment, both end portions in the tire width direction of the low-loss tangent rubber portion 28 extend to the inside in the tire radial direction in the region where the soft rubber portions 22 and 23 are arranged, and overlap with each other via the center-side rubber portion 26. However, the present invention is not limited to this configuration, and the soft rubber portion 22 or the soft rubber portion 23 is disposed only at one end of the low loss tangent rubber portion 28 in the tire width direction. It is good also as a structure which extends to the tire radial inside of an area | region and has overlapped via the center side rubber part 26. FIG.
In addition to the first embodiment, the configuration of the present embodiment may be applied to any of the second to sixth embodiments. In the embodiment having a configuration in which the soft rubber portion 23 is disposed only on the other side of the tread portion 18 as in the fourth embodiment, the configuration of the present invention is applied only to the soft rubber portion 23.

[Ninth Embodiment]
Next, a ninth embodiment will be described. As shown in FIG. 10, the pneumatic tire 100 for a motorcycle according to the present embodiment (hereinafter simply referred to as the tire 100) has a different tread end rubber structure compared to the first embodiment. In the present embodiment, both ends in the tire width direction of the low-loss tangent rubber portion 28 extend on both sides in the tire width direction, and at least a part overlaps adjacent to the inner side in the tire radial direction of the soft rubber portions 22 and 23, respectively. The tire center sides 22 and 23 are adjacent to the center rubber portion 26. In addition, in FIG. 10, the tread end side of the side in which the soft rubber part 22 is provided is shown.

Next, the operation of the ninth embodiment will be described. Note that the description of the same operation as that obtained in the first embodiment is omitted.
Since both ends of the low loss tangent rubber portion 28 in the tire width direction extend on both sides in the tire width direction and at least a part of the low loss tangent rubber portion 28 is adjacent to the inner side in the tire radial direction of the soft rubber portions 22 and 23, the soft rubber portion 22 is overlapped. , 23, the low loss tangent rubber portion 28 controls the amount of heat generation, and the tread shoulder portion S can be prevented from blowing. Further, in this embodiment, since the center side rubber portion 26 is not interposed between the soft rubber portions 22 and 23 and the low loss tangent rubber portion 28 as compared with the eighth embodiment, the tread portion 18 can be formed with less input. Because it can generate heat, it has excellent lateral grip.

In the present embodiment, the both ends of the low-loss tangent rubber portion 28 in the tire width direction extend to both sides in the tire width direction, and at least a part of the low-loss tangent rubber portion 28 is adjacent to the inner side in the tire radial direction of the soft rubber portions 22 and 23. However, the present invention is not necessarily limited to this configuration, and only one end portion in the tire width direction of the low-loss tangent rubber portion 28 is adjacent to the inner side in the tire radial direction of the soft rubber portion 22 or the soft rubber portion 23. It is also possible to have a configuration in which they overlap.
In addition to the first embodiment, the configuration of the present embodiment may be applied to any of the second to sixth embodiments. In the embodiment having a configuration in which the soft rubber portion 23 is disposed only on the other side of the tread portion 18 as in the fourth embodiment, the configuration of the present invention is applied only to the soft rubber portion 23.

[Tenth embodiment]
Next, a tenth embodiment will be described. As shown in FIG. 11, in the pneumatic tire 110 for a motorcycle according to the present embodiment, the development width of the spiral belt 16 is different compared to the first embodiment. In the present embodiment, the development width W3 of the spiral belt 16 is set within a range of 60% to 90% of the tread development width L.

Next, the operation of the tenth embodiment will be described. Note that the description of the same operation as that obtained in the first embodiment is omitted.
When the development width W3 of the spiral belt 16 exceeds 90% of the tread development width L, the area where the spiral belt 16 is not arranged is too narrow, and the cross belt 17 cannot be sufficiently extended, and the tread shoulder portion S is worn. Not improved. Further, if the development width W3 is less than 60% of the tread development width L, the area where the spiral belt 16 is not arranged is too wide, and the cross belt 17 in the area where the spiral belt 16 is not arranged extends as a whole. S wear is not improved. On the other hand, if the developed width W3 of the spiral belt 16 is in the range of 60% or more and 90% or less of the tread developed width L, the crossing belt 17 in the region where the spiral belt 16 is not arranged is extended and the tread portion is expanded. The speed difference with the 18 contact surface is reduced, and the wear resistance in the tread shoulder portion S is improved.

  In addition to the first embodiment, the configuration of the present embodiment may be applied to any of the second to ninth embodiments.

[Other embodiments]
In the first to ninth embodiments, the spiral belt 16 or the spiral belt 16 is disposed outside the carcass 14 in the tire radial direction. However, the present invention is not limited to this configuration, and the spiral belt 16 is not disposed. In this case, it is preferable to set the angle of the cords of the belt ply 17A and the belt ply 17B of the crossing belt 17 with respect to the tire equatorial plane CL to 30 degrees.

  In the first to tenth embodiments, the cross belt 17 is disposed outside the spiral belt 16 in the tire radial direction. However, the present invention is not limited to this configuration, and the cross belt 17 is not disposed. Alternatively, as an alternative to the crossing belt 17, a belt formed by burying a plurality of parallel cords in the covering rubber may be used so that the angle of the cord with respect to the tire equatorial plane CL on the tire equatorial plane CL is One sheet may be arranged to be 90 degrees.

  The embodiments of the present invention have been described above with reference to the embodiments. However, these embodiments are merely examples, and various modifications can be made without departing from the scope of the invention. It goes without saying that the scope of rights of the present invention is not limited to these embodiments.

<Test example>
In order to confirm the effect of the present invention, the present inventor made eight examples of a pneumatic tire for a motorcycle according to the present invention (hereinafter referred to as Examples 1 to 8) and two examples of a pneumatic tire for a motorcycle for comparison ( Hereinafter, a performance test was performed to evaluate the performance of an example of a conventional pneumatic tire for a motorcycle (hereinafter referred to as a conventional example). All tire sizes are 190 / 50ZR17.

  The basic structure of each tire used in this test is substantially the same as the basic structure of the tire of the first embodiment, and the set values of each tire are the deployment width of the belt ply 17A is 250 mm and the deployment width of the belt ply 17B. 230 mm, the thickness of the tread portion 18 is all 7 mm (that is, the average thickness of the tread portion 18 is 7 mm), the tread development width L is 240 mm, and the Shore A hardness M0 of the center side rubber portion 26 at 100 ° C. is 35 (dynamic elastic modulus). E ′ is set to 1.42 MPa). The low-loss tangent rubber portion 28 has a development width of 140 mm, a thickness (on the tire equatorial plane) of 3 mm, and a Shore A hardness of 100 ° C. of 50 (dynamic elastic modulus E ′ is equivalent to 2.60 MPa). Has been.

Hereinafter, the specification of each tire used in this test example will be described. Table 1 summarizes the specifications of each tire. In the following description, the numerical values indicating the widths all mean the numerical values of the development width.

(Conventional example)
A tire in which only one type of rubber forming the tread portion 18 is used, and the Shore A hardness at 100 ° C. of the rubber is set to 35.

(Example 1)
A tire having the same structure as the tire of the first embodiment. The soft rubber portion 22 has a Shore A hardness M1 of 100 ° C. of 30 (dynamic elastic modulus E ′ is equivalent to 1.16 MPa), a development width W1 of 40 mm, and a thickness H1 of 4 mm. The Shore A hardness M2 at 25 ° C. is set to 25 (the dynamic elastic modulus E ′ is equivalent to 0.92 MPa), the developed width W2 is set to 40 mm, the thickness H2 is set to 4 mm, and the developed width W3 of the spiral belt 16 is set to 240 mm. ing. Moreover, the arrangement | positioning shape of the soft rubber parts 22 and 23 is made into FIG. 2, respectively.

(Example 2)
A tire having the same structure as the tire of the second embodiment. The 100 ° C Shore A hardness M1 of the soft rubber portion 22 is set to 30, the developed width W1 is set to 40 mm, and the thickness H1 is set to 2 mm. The Shore A hardness M2 of the soft rubber portion 23 at 100 ° C is 30 and the developed width W2 is set to 30 mm. 40 mm, the thickness H2 is set to 7 mm, and the development width W3 of the spiral belt 16 is set to 240 mm. Further, the arrangement shape of the soft rubber portion 22 is shown in FIG. 2, and the arrangement shape of the soft rubber portion 23 is shown in FIG.

(Example 3)
A tire having the same structure as the tire of the third embodiment. The 100 ° C Shore A hardness M1 of the soft rubber portion 22 is set to 30, the developed width W1 is set to 25 mm, and the thickness H1 is set to 4 mm. The Shore A hardness M2 of the soft rubber portion 23 at 100 ° C is 30 and the developed width W2 is set to 30 mm. 70 mm, the thickness H2 is set to 4 mm, and the development width W3 of the spiral belt 16 is set to 240 mm. Moreover, the arrangement | positioning shape of the soft rubber parts 22 and 23 is made into FIG. 2, respectively.

Example 4
A tire having the same structure as the tire of the fourth embodiment. The 100 ° C Shore A hardness M2 of the soft rubber portion 23 is set to 25, the developed width W2 is set to 40 mm, the thickness H2 is set to 4 mm, and the developed width W3 of the spiral belt 16 is set to 180 mm. Moreover, the arrangement | positioning shape of the soft rubber part 23 is made into FIG.

(Example 5)
A tire in which the development width W3 of the spiral belt 16 of the tire of Example 3 is set to 180 mm.
(Example 6)
The tire in which the arrangement shape of the soft rubber portions 22 and 23 of the tire of Example 1 is shown in FIG.

(Example 7)
The tire in which the thickness H1 of the soft rubber portion 22 of the tire of Example 1 is set to 4 mm and the thickness H2 of the soft rubber portion 23 is set to 4 mm. Further, the arrangement shape of the soft rubber portion 22 is shown in FIG. 9, and the arrangement shape of the soft rubber portion 23 is shown in FIG.
(Example 8)
The tire of Example 7 in which the development width W1 of the soft rubber portion 22 is set to 25 mm, the development width W2 of the soft rubber portion 23 is set to 70 mm, and the development width W3 of the spiral belt 16 is set to 180 mm.

(Comparative Example 1)
A tire in which the 100 ° C Shore A hardness M1 of the soft rubber portion 22 of the tire of Example 1 is set to 25 and the 100 ° C Shore A hardness M2 of the soft rubber portion 23 is set to 25.
(Comparative Example 2)
A tire in which the development width W3 of the spiral belt 16 of the conventional tire is set to 180 mm.

(Test method and evaluation results)
In this test example, using these tires, the following three types of tests were performed to evaluate the performance of each tire.

(Test A) Evaluation of lateral grip property by measuring lateral force at 50 degrees CA In test A, as a testing machine, paste # 40 sandpaper on a steel drum with a diameter of 3 m, and use sandpaper on the road surface. I like it.

  Each tire was assembled on a wheel having a rim width of 6 inches and a rim diameter of 17 inches, and the tire internal pressure was set to 200 kPa. Then, it was pressed against the drum at a CA of 50 degrees, a load of 1500 N, and a SA of 0 degrees, and the drum was rotated so that the tire rolled at 100 km / h, and the lateral force in this state was measured from a three-component force meter attached to the rotating shaft of the tire. did. Lateral force is camber thrust.

  When measuring the lateral force, it was measured 5 minutes after the tire started rotating. At this time, the tire was sufficiently warmed, and the temperature of the tread shoulder portion was about 100 ° C.

In test A, the lateral force of the conventional example was set to a lateral force index of 100. The lateral force of Conventional Example 1 was 1700N. And about each other tire, the lateral force index used as the relative evaluation with respect to a prior art example was calculated | required. This index is also shown in Table 1. Table 1 shows that the greater the lateral force index, the greater the lateral force and the better the lateral grip.
Further, the lateral force was measured on both ends of the tread in the tire width direction. That is, the camber was tilted 50 degrees to the left and right for measurement.

(Test B) Evaluation of Steering Stability on Test Course In Test B, a comprehensive steering stability test was conducted on a test course by skilled riders. Since the prepared tire was a rear tire, an actual vehicle test was performed by replacing the rear-only tire. The front tire was always fixed with a conventional one.

  In this test B, a 1000 cc sports type motorcycle was prepared, and the vehicle was actually driven on a test course, and the steering stability (cornering performance) at the time of turning the vehicle was largely evaluated. The evaluation was a comprehensive evaluation based on a 10-point method based on the rider's feeling. The turning evaluation was performed on the left and right, and the right and left turns were assigned. The test course used the circuit (refer FIG. 14) with many left turns. The evaluation results are also shown in Table 1. In Table 1, it shows that steering stability is so good that a score (score) is high.

  In Test B, the lap time for one round of the test course is about 130 seconds for any tire. In Test B, this test course was made 6 laps. Table 1 shows the average of lap times when the test course is made 6 laps for each tire. The lower the average lap time, the better.

  FIG. 14 is a graph showing the usage frequency of the bank angle (camber angle) of one circuit round. The vertical axis indicates the percentage of time used for one round of time. In this circuit, as can be seen from FIG. 14, the left turning corner is very many, and the left tread is frequently used.

(Test C) Evaluation of wear amount Before performing Test B, the weight of each tire was measured in advance. The weight of the tire was a value measured by removing it from the rim.

  Then, after 6 laps of the test course in Test B, deposits such as rubber debris and pebbles adhered to the tire were removed cleanly, the tire was removed from the rim, and the tire weight was measured. At this time, the tire was cut into two right and left at the equator plane of the tread center portion, and the weight of the right tire and the weight of the left tire were measured. The amount of wear on the left and right sides of the tire is measured by subtracting the weight of the tire after running from the weight of one tire when it is new.

  The weight difference from the new article can be evaluated as the amount of wear. Since there were many corners on the test course, wear was concentrated on the tread shoulder. That is, the obtained weight difference can be considered as the wear amount of the tread shoulder portion from the new article.

  In evaluating the wear amount, the wear amount on the right side (low usage frequency side) of the conventional example was set as an index 100, and for other tires, an index serving as a relative evaluation with respect to the conventional example was obtained. The evaluation results are also shown in Table 1. Table 1 shows that the lower the wear index, the better the wear resistance.

(Consideration from tests A to C)
From the above evaluation results, the present inventor conducted the following consideration.
The conventional example, comparative example 1 and example 1 are compared. In the conventional example, the tread portion has no soft rubber portion. In contrast, in Comparative Example 1, the soft rubber portions 22 and 23 are arranged symmetrically. By placing soft rubber parts on the left and right, the lateral force index on the drum has improved, and the grip on the circuit has also improved. And lap time was shortened. However, the left side (frequently used side) wears a lot, and in the second half of the lap (5th and 6th laps in 6 laps), the left tread is worn out, so the grip force is lost and the lap time It was conspicuous that it fell.

In contrast, in Example 1, the left soft rubber portion (23) is slightly hardened. In Example 1, in the left turn, the grip is less likely to be lowered even when traveling is repeated. Therefore, the lap time is faster than Comparative Example 1. Further, the left side wear amount was improved as compared with Comparative Example 1.
In Example 1, the wear amount was improved and the lap time was shortened by 2 seconds or more as compared with the conventional example.

  Race tires are used under extremely harsh input conditions, so they slip sideways during driving or slip longitudinally with engine torque. Wear is characterized by being promoted when slippage is large. Therefore, when the soft rubber portion is arranged and the grip force is increased, the slip may be settled and the wear may be improved. In the case of a commercially available tire, when the soft rubber portion is disposed, the soft rubber portion is likely to be worn out and wear is generally advanced, but the opposite phenomenon may be observed in circuit driving with severe input. This time, the wear performance of Comparative Example 1 is improved as compared with the conventional example. However, on the left side of Comparative Example 1, the amount of improvement in wear was small because the soft rubber part was too soft for the input. Compared with this, although the soft rubber part on the left side of Example 1 is harder than Comparative Example 1, the wear performance is improved.

  In Example 2, soft rubber portions having the same hardness and the same width are arranged on both sides in the tire width direction. However, the thickness of the arranged soft rubber part is different. On the right side, a soft rubber part was arranged for the entire thickness of the tread shoulder part. On the left side, a soft rubber portion is disposed only on the tread side with a thickness of 2 mm.

By changing the thickness of the soft rubber part, the rigidity of the tread part can be adjusted. Further, by arranging the soft rubber portion thickly, even if the usage frequency is low, the tread portion immediately generates heat, and the tread portion is warmed to an appropriate temperature for generating a grip.
Example 2 had a higher score than Conventional Example 1 and Comparative Example 1, and the lap time at the circuit was also shortened. As for wear, the left side wear was particularly improved.

  In Example 3, soft rubber portions having the same hardness and the same thickness are arranged and the width thereof is changed. The width of 25 mm corresponds to 10% of the tread width and corresponds to the area A in FIG. The width of 70 mm corresponds to 29% of the tread width, and is a width that covers all of the areas A to C in FIG. In this circuit, since the right-hand turn is extremely small, the right tread portion has no problem even if the soft rubber portion is arranged in the region C. Rather, since the right soft rubber portion was softened to increase the grip force, tire slippage was suppressed in the right turn, and the amount of wear was improved despite the placement of the soft rubber portion. Since the left side of the turn is difficult to input and is used for a long time, the soft rubber portion is disposed only in the region A of FIG. On the left side as well, the grip strength increased and the amount of wear decreased.

  In Example 4, the left side is the same as the conventional one, and the soft rubber portion is arranged only on the right side. In this way, there is an advantage that the manufacturing process is simplified and facilitated. In Example 4, the width of the spiral belt was set to 180 mm corresponding to 75% of the developed tread width. As a result, the amount of wear was reduced, and the lap time on the circuit was faster than the conventional example.

  In Comparative Example 2, the width of the spiral belt of the conventional example is changed to 180 mm, but even when compared with Comparative Example 2, Example 4 in which a soft rubber portion is arranged on the surface of the right tread rubber that is less frequently used. The lap time has been shortened. This is because the grip force on the right side which is not frequently used is improved by the soft rubber portion.

In Example 5, the width of the spiral belt of Example 3 is 180 mm.
In Comparative Example 2, the width of the spiral belt of the conventional example is 180 mm, but the lap time is shortened by 1.5 seconds compared to the conventional example. On the other hand, in Example 5, the lap time is shortened by 2 seconds compared to Conventional Example 3, and the effect is great. In addition, the amount of wear was confirmed to be greatly improved.
As described above, when the soft rubber portion is disposed and the width of the spiral belt is reduced to 180 mm, a larger effect can be obtained than when each element is used alone.
In Example 5, the lap time is very fast and the amount of wear is extremely small.

  In Example 6, the soft rubber portion is gradually exposed as it wears. In Example 1, the soft rubber portions are arranged with the same width in the thickness direction. However, when these are compared, Example 6 has a faster average lap time. This is because the grip force was maintained especially in the second half of the lap. As a result, the amount of wear in Example 6 is less than that in Example 1.

  Example 7 has a structure in which a low loss rubber portion having a small loss tangent inside the tread center portion and hardly generating heat reaches the tire shoulder portion. In this way, by arranging the low-loss rubber portion that does not easily generate heat inside, the temperature of the tread shoulder portion does not rise excessively even if traveling is repeated, and an appropriate temperature can be maintained. Therefore, stable lap time could be measured even in the second half of the lap. As a result, the average lap time for 6 laps became faster.

In Example 8, all the good parts of the previous examples were combined. The hardness, thickness, and width of the left and right soft rubber portions were changed, and the low-loss rubber portion that hardly generated heat at the tread center portion was extended to the tread shoulder portion. As a result, the lap time showed a significant improvement of 5 seconds 7 compared to the conventional example. The amount of wear was also greatly reduced.
Thus, a synergistic effect can be expected by combining the configurations of the present invention.

1 is a tire radial direction cross-sectional view of a motorcycle pneumatic tire according to a first embodiment. 1 is a partial tire radial direction sectional view showing a tread end side of a pneumatic tire for a motorcycle according to a first embodiment. It is a tire radial direction sectional view of the pneumatic tire for motorcycles concerning a 2nd embodiment. It is a tire radial direction sectional view of the pneumatic tire for motorcycles concerning a 3rd embodiment. It is a tire radial direction sectional view of the pneumatic tire for motorcycles concerning a 4th embodiment. It is a tire radial direction sectional view of the pneumatic tire for motorcycles concerning a 5th embodiment. It is a tire radial direction fragmentary sectional view showing the tread end side of the pneumatic tire for motorcycles concerning a 6th embodiment. It is a tire radial direction fragmentary sectional view showing the tread end side of the pneumatic tire for motorcycles concerning a 7th embodiment. It is a tire radial direction fragmentary sectional view showing the tread end side of the pneumatic tire for motorcycles concerning an 8th embodiment. It is a tire radial direction fragmentary sectional view showing the tread end side of the pneumatic tire for motorcycles concerning a 9th embodiment. It is a tire radial direction sectional view of the pneumatic tire for motorcycles concerning a 10th embodiment. It is explanatory drawing explaining the grounding of the pneumatic tire for two-wheeled vehicles. It is explanatory drawing which shows another contact surface shape by the grounding of the pneumatic tire for motorcycles. It is a figure which shows the usage frequency of each CA of the circuit used for a test.

Explanation of symbols

10 tires (pneumatic tires for motorcycles)
14 Carcass 16 Spiral belt 18 Tread part 22 Soft rubber part 23 Soft rubber part 26 Center side rubber part 28 Low-loss tangent rubber part 30 Tire (pneumatic tire for motorcycle)
40 tires (pneumatic tires for motorcycles)
50 tires (pneumatic tires for motorcycles)
60 tires (pneumatic tires for motorcycles)
70 tires (pneumatic tires for motorcycles)
80 tires (pneumatic tires for motorcycles)
90 tires (pneumatic tires for motorcycles)
100 tires (pneumatic tires for motorcycles)
110 tires (pneumatic tires for motorcycles)
L tread deployment width T tread edge W1 deployment width (deployment width of one soft rubber part)
W2 deployment width (deployment width of the other soft rubber part)
W3 width (spiral belt width)
H1 thickness (thickness of one soft rubber part)
H2 thickness (thickness of one soft rubber part)
M1 Shore A hardness (Shore A hardness of one soft rubber part)
M2 Shore A hardness (Shore A hardness of the other soft rubber part)

Claims (9)

A pneumatic tire for a motorcycle comprising at least one carcass, at least one belt disposed on the outer side in the tire radial direction of the carcass, and a tread portion disposed on the outer side in the tire radial direction of the belt. And
At least on the tread side on both sides of the tread portion in the tire width direction, the development width from the tread end is within a range of 5 to 30% of the tread development width, and the shore is larger than the center side rubber portion adjacent to the tire center side. A soft rubber part with low A hardness is formed,
A pneumatic tire for a motorcycle, wherein one soft rubber portion is different from the other soft rubber portion in at least one of Shore A hardness, thickness, and development width. A pneumatic tire for a motorcycle comprising at least one carcass, at least one belt disposed on the outer side in the tire radial direction of the carcass, and a tread portion disposed on the outer side in the tire radial direction of the belt. And
Only on one side of the tread portion in the tire width direction, the development width from the tread end is within a range of 5 to 30% of the tread development width, and the Shore A hardness is lower than the center side rubber portion adjacent to the tire center side. A pneumatic tire for a motorcycle, characterized in that the soft rubber portion is formed at least on the tread side.   3. The pneumatic tire for a motorcycle according to claim 1, wherein a development width of the soft rubber portion gradually increases from a tread surface toward an inner side in a tire radial direction. 4.   The pneumatic tire for a motorcycle according to any one of claims 1 to 3, wherein a thickness of the soft rubber portion is in a range of 20% to 100% of an average thickness of the tread portion. tire.   The air for a motorcycle according to any one of claims 1 to 4, wherein at least a part of the tread center portion of the tread portion is formed by laminating two or more rubber layers. Tires.   The pneumatic tire for a motorcycle according to claim 5, wherein the center side rubber portion forms an outermost rubber layer of the tread center portion.   The pneumatic tire for a motorcycle according to claim 5 or 6, wherein an innermost rubber layer of the tread center portion extends in a tire width direction until it overlaps at least a part of the soft rubber portion. .   The motorcycle air according to any one of claims 1 to 7, wherein the at least one belt includes a spiral belt having a cord angle of 5 degrees or less with respect to a tire equator direction. Tires.   The pneumatic tire for a motorcycle according to claim 8, wherein a development width of the spiral belt is in a range of 60% to 90% of a tread development width.

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