JP4889032B2 - Pneumatic tires for motorcycles - Google Patents

Description

  The present invention relates to a pneumatic tire for a motorcycle (hereinafter, also simply referred to as “tire”), and more particularly to a pneumatic tire for a motorcycle according to improvement in steering stability performance.

  Since a motorcycle has a feature that the vehicle body tilts and turns, in a tire for a motorcycle, a portion of the tire that contacts the road surface moves due to the inclination of the vehicle body. Also, when standing upright, the speed is high and the braking force and driving force in the front-rear direction (tire equator direction) are applied. On the other hand, when turning the vehicle body, lateral force is mainly applied and the speed is slow. There is a feature that becomes. Therefore, how the tire tread portion is used also differs between the center portion and the shoulder portion. In particular, general consumers and riders who are racing are required to improve the grip when a motorcycle is greatly defeated.

From the above viewpoint, in a tire provided with a so-called spiral belt, which is a reinforcing member formed by spirally winding a reinforcing cord at an angle toward the tire circumferential direction, a portion that comes into contact with a vehicle when the vehicle body is largely tilted (tread end side) For example, Patent Documents 1 and 2 disclose techniques for improving the gripping force by disposing soft rubber. In these Patent Documents 1 and 2, the tread portion is divided into a center region in the width direction and shoulder regions on both sides thereof, and the desired tire characteristics are obtained by changing the hardness and elastic modulus of the tread rubber in each region. It is expressed.
JP-A-7-108805 (Claims etc.) JP 2000-158910 A (Claims etc.)

  However, with the improvement in the performance of motorcycles, further improvement in performance has been demanded for tires, and further improvement is required in terms of steering stability performance, that is, gripping force when a motorcycle is largely defeated. In addition, securing the wear resistance of the tread is one of the important required performances of the tire.

  Accordingly, an object of the present invention is to provide a pneumatic tire for a motorcycle that solves the above-described problems, ensures wear resistance performance, and improves handling stability performance at the time of turning compared to the conventional one by improving grip force. It is to provide.

  As described above, in a pneumatic tire for a two-wheeled vehicle, since the two-wheeled vehicle turns while tilting the vehicle body, the place where the tire tread portion is in contact with the road surface is different during straight traveling and during turning. That is, the center part of the tread is used when going straight, and the end part of the tread is used when turning. Also, the performance required for tires is required to grip against the input (ie acceleration / deceleration) in the circumferential direction (equatorial direction) of the tire when going straight, and against the lateral direction (width direction) of the tire when turning. Gripping is required.

  In order to turn a two-wheeled vehicle quickly, it is necessary to tilt the vehicle body greatly in order to balance the centrifugal force that increases with the turning speed, and it is necessary to be able to grip the tire by the centrifugal force. In other words, if the tire grip is insufficient when the vehicle body is greatly tilted, the vehicle cannot turn quickly, so the effect of the grip here on the turning performance is very large. Thus, the conventional approach is to change the rubber type between the tire center and the tire shoulder.

  Based on the above, the present inventor has conducted detailed research to further improve the grip when turning, and in particular, a grip angle at which the motorcycle vehicle falls most greatly (camber angle = CA) around 45 to 50 °. Worked on improving intensively. 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 increased, and as a result, the lap time is improved. Also, on general roads, increasing the grip during turning can contribute to safety.

  In a tire for a motorcycle, particularly with respect to turning performance when the vehicle body is largely tilted, one end of the tread of the tire is grounded to generate a grip. When the vehicle is turned with the vehicle body largely lowered, the grounding state as shown in FIGS. The ground contact shape at this time will be considered. 5 and 6, (a) is a cross-sectional view in the width direction of the tire at the time of contact, (b) is its contact shape, and FIG. 5 (b) is a cross-section in the tire circumferential direction. b) shows the deformation of the tread corresponding to each contact area with respect to the cross section in the tire width direction.

  First, consider a cross section in the tire circumferential direction. As shown in FIGS. 5 (a) and 5 (b), the deformation state of the tread portion is different between the region C near the center and the region A near the tread edge in the ground contact shape. Looking at the deformation of the tire in the tread portion in the rotational direction (also referred to as the tire circumferential direction or the tire front-rear direction), it is in the driving state near the tire center and in the braking state near the tread edge.

  Here, in the driving state, when the tire is cut along the circumferential direction, the tread deformation is sheared backward in the tire traveling direction on the lower surface of the tread (the surface in contact with the skeleton member inside the tire) This is a shearing state in which the tread surface that is in contact with 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, the braking state is the reverse of the driving state, and the deformation of the tread is a shearing state in which the tire inner side (belt) is sheared forward and the tread surface that is in contact with the road surface is deformed rearward, This is the movement of the tire when braking.

  As shown in FIG. 5, when the vehicle is turning at a large angle, such as 45 °, the vehicle is driven in the ground contact area near the tread center even when the tire is rotating without driving force or braking force. Appears and a braking state appears near the end of the tread. This is due to the difference in the radius of the belt portion of the tire (diameter difference). In a tire for a motorcycle, since the tire crown portion is greatly rounded, the distance from the rotation shaft to the belt is greatly different between the tread center portion and the tread end portion. In the case of FIG. 5, the radius R1 near the center of the ground contact shape is clearly larger than the radius R2 near the tread end portion of the ground contact shape. Since the angular speed at which the tire rotates is the same, the speed of the belt part (when the tire is in contact with the road surface, it means the speed in the tire circumferential direction along the road surface; the belt radius multiplied by the tire angular speed) is The portion of R1 having a larger radius is faster.

  The tread surface of the tire is not sheared in the front-rear direction at the moment of contact with the road surface, but proceeds with tire rotation while in contact with the road surface, and undergoes shear deformation in the front-rear direction when leaving the road surface. At this time, the tread near the tire center where the belt speed is fast becomes shearing deformation in the driving state, and the belt speed is slow at the end of the tread of the tire, so that braking deformation occurs. Further, at the center portion of the ground contact shape, there is almost no deformation of the tread in the tire circumferential cross section.

  The above is considered by the tire tread width. When turning at CA 45 to 50 °, approximately 1/4 of the tread width (full width) of the tire is grounded. As shown in the figure, when the quarter of the grounded area is divided into three equal parts and referred to as areas A, B, and C from the tread end, the area A is in a braking state, and the area B is in a neutral state with almost no deformation. Region C is in a driving state. The above is a deformation | transformation about the equator surface of a tire. The deformation of the braking state in the region A and the driving state in the region C means that the tread is deformed and sheared in the tire circumferential direction, so that the tread is easily slipped in the tire circumferential direction. That is, wear occurs in the region A and the region C.

  Next, the deformation | transformation in the width direction cross section of the tire shown in FIG. 6 is considered. Lateral tread deformation generates camber thrust. This is because when the trajectory of the arc is viewed from below the road surface, it becomes an ellipse when the camber is attached, and the belt draws an elliptic arc. Therefore, as shown in FIG. 6B, the trajectory of the belt becomes a crescent shape. On the other hand, when the surface of the tread comes into contact with the road surface at the stepping portion, it moves straight toward the kicking out as it is. The difference between the crescent-shaped trajectory and the straight trajectory is the transverse shear of the tread. As can be seen from FIG. 6B, this means that the portion with a long contact length has a large amount of lateral shear. That is, among the regions A, B, and C, in the ground contact state of CA 45 ° to 50 °, the ground contact length of the region B is the longest, and the lateral shear is the largest in the region B. Region A and region C have a short contact length, and therefore do not generate as much force as region B. In the regions A and C, the deformation in the tire circumferential direction (equatorial direction) described with reference to FIG. 5 is stronger than the deformation in the width direction.

  Based on the behavior of the tread as described above, as a result of further intensive studies, the present inventors have prescribed the elastic modulus of the regions A to C, thereby increasing the grip force at CA 45 ° to 50 °, The inventors have found that the wear on the tread surface can be suppressed, and have completed the present invention.

That is, a pneumatic tire for a motorcycle according to the present invention includes a bead core embedded in a pair of left and right bead portions, at least one carcass extending across a toroid between the pair of bead portions, and the carcass A pneumatic tire for a motorcycle having at least one belt layer disposed on the outer side in the tire radial direction of the tire and a tread portion disposed on the outer side in the tire radial direction of the belt layer.
Of the tread portion, a region of 50% of the tread development width centered on the tire equator plane is a tread center portion, a region of 25% of each tread development width on both sides of the tread center portion is a tread side portion, and When the tread side is divided into three equal parts from the tread edge to area A, area B, and area C,
The average elastic modulus at 100% elongation of the tread rubber in region B at 40 ° C. is higher than the average elastic modulus at 100% elongation of the tread rubber in region A and region C at 40 ° C. It is.

In the present invention, it is preferable that the average elastic modulus of each of the tread rubbers in the regions A, B, and C at 100% elongation at 40 ° C. satisfies the relationship of region B> region C> region A. Further, the tread rubber in the region B comprises two layers of inner and outer, elastic modulus at 100% elongation at 40 ° C. of the inner tread rubber, modulus at 100% elongation at 40 ° C. of the outer tread rubber Higher than that. Further, the tread rubber forming the tread surface of the region A and the region B is preferably made of the same kind of rubber. Furthermore, the present invention is also effective when the average elastic modulus at 100% elongation at 40 ° C. is the average elastic modulus at 100% elongation at 100 ° C.

  According to the present invention, by adopting the above-described configuration, a pneumatic tire for a motorcycle that achieves wear resistance performance and improved handling stability performance at the time of turning as compared with the prior art by improving gripping power is realized. It became possible.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view in the width direction of a pneumatic tire for a motorcycle according to a preferred embodiment of the present invention. As shown in the figure, a pneumatic tire 10 for a motorcycle according to the present invention includes at least one bead core 1 embedded in a pair of left and right bead portions 11 and a toroidal shape extending between the pair of bead portions 11. Carcass 2, at least one belt layer 3 disposed on the outer side in the tire radial direction, and a tread portion 12 disposed on the outer side in the tire radial direction of the belt layer 3.

  In the tire 10 of the present invention, as shown in the drawing, a region of 50% of the tread deployment width centered on the tire equatorial plane is a tread center portion of the tread portion 12, and 25% of each tread deployment width on both sides thereof. Define the region as the tread side. Here, expanding the tread means that the tread having a roundness in the width direction is flattened so that the length of the arc is a straight line. The 50 portion of the tread center portion was used as a tread center region, and the other portions were used as tread side portions. That is, the tread side portion is 25 on each of the left and right sides.

  When a tire contacts the road surface at a camber angle of 45 ° to 50 °, in a general motorcycle, the side portion of the tire is in contact with the road surface. That is, the region of the tread side portion of the one side 25 is grounded to the road surface. In the present invention, the tread side portion is further divided into three equal parts and defined as region A, region B, and region C from the tread end. As shown in FIGS. 5 and 6, when the motorcycle turns at a CA of 45 ° to 50 °, it is divided into three regions A, B, and C, respectively. This is because these regions show characteristic behavior. That is, as described above, the cross section in the tire circumferential direction is the region A: braking, the region B: neutral (no deformation), the region C: driving deformation, and the cross section in the tire width direction is the region A: transverse shear. Small, region B: large transverse shear, region C: small transverse shear.

  Regarding the above regions A to C, in the present invention, the average elastic modulus at 100% elongation of the tread rubber in the region B at 40 ° C. is the average elastic modulus at 100% elongation of the tread rubber in the region A and the region C at 40 ° C. It is important that the elastic modulus is set to be higher than that. That is, it is defined that the elastic modulus of the region B is larger than those of the other two regions. In this case, it is sufficient that the elastic modulus of the region B is larger than the regions A and C. As for the elastic modulus, both may be the same or either may be larger.

Here, the elastic modulus of each region is set to an average elastic modulus because, in the case of a motorcycle, the tread has a thickness, so that different types of rubber may be used in the thickness direction of the tread. Therefore, for example, when the tread has two layers and the inside has a high elastic modulus and the outside has a low elastic modulus, if the thickness of the two layers is the same, the average of both elastic moduli is simply obtained, and the thicknesses are different. For example, averaging is performed in consideration of thickness (volume). For example, when the thickness of the inner tread rubber is 3 mm and the elastic modulus is 100, and the thickness of the outer tread rubber is 4 mm and the elastic modulus is 150, the following formula:
(100 × 3 + 150 × 4) / (3 + 4) = 129
Accordingly, the average elastic modulus is 129.

  Also, the elastic modulus may change not in the thickness direction but also in the width direction of the tread. For example, this corresponds to the case where the region B is divided into two parts in a cross section parallel to the tire circumferential direction, and different rubber is used on the tire center side and the tread end side in the width direction. The elastic modulus is averaged according to This is the meaning of the average elastic modulus in the present invention.

  The reason why the elastic modulus of the region B is increased in the present invention is that the camber thrust (lateral force) is increased when the elastic modulus of the region B is increased. As shown in FIG. 5, in a tire for a motorcycle turning at a CA of 45 ° to 50 °, the longitudinal direction (tire equator direction) that does not contribute to the lateral force (camber thrust) of region A: braking and region C: driving. Deformation in the circumferential direction). When the shearing force due to this deformation increases, the tread cannot be attached to the road surface and slides in the circumferential direction. This sliding causes wear. Therefore, in the present invention, it is specified that the elastic modulus of the region B is increased and the elastic modulus of the regions A and C is decreased. Since the elastic moduli of the regions A and C are small, the shearing force can be small even if the tire circumferential deformation occurs. Therefore, the tread can stick without slipping from the road surface. Thereby, the amount of wear is suppressed in regions A and C.

  On the other hand, when the deformation in the lateral direction is confirmed, as shown in FIG. 6, the shear amount in the lateral direction of region B (direction of 90 ° with respect to the tire circumferential direction) is the largest, and the shear amount in regions A and C is small. . That is, if the elastic modulus of the region B is increased as in the present invention, a large camber thrust can be earned in the region B, which is very efficient. On the other hand, since the shear amount of the regions A and C is originally small, even if the elastic modulus is lowered, the reduction amount of the camber thrust is not so large. Conversely, if the elastic modulus of the regions A and C is lowered, the regions A and C will not slide in the tire circumferential direction and the tread will stick, so the friction coefficient of the regions A and C may increase and exert a force in the lateral direction. is there. It is known that the coefficient of static friction is larger than the coefficient of dynamic friction. If the tread adheres to the road surface without slipping, the coefficient of friction can be kept high. Regions A and C have a characteristic of sliding in the tire circumferential direction as shown in FIG. If this circumferential slip is eliminated, the regions A and C become completely sticky, the friction coefficient can be used as the static friction coefficient, and the lateral friction force may increase.

  On the other hand, when the elastic moduli of the regions A, B, and C are uniformly hardened, a large camber thrust in the lateral direction can be generated in the region B, but the tread slips in the circumferential direction in the regions A and C. Not only does the wear progress at C, but the friction coefficient decreases due to slipping in the regions A and C, and the force cannot be exerted in the lateral direction. Further, if the elastic modulus of the regions A, B, and C is uniformly softened, the slip in the equator direction (circumferential direction) of the regions A and C is reduced, but the shear force of the lateral tread in the region B is reduced. , Camber thrust is lowered.

  As described above, as in the present invention, the region grounded at CA 45 ° to 50 ° is divided into three, and only the elastic modulus of region B is increased, and the elastic modulus of regions A and C is kept low. Is effective against lateral force (grip). It is also effective against wear.

In the present invention, the difference between the elastic modulus of region B and the elastic modulus of region A is the following equation:
Elastic modulus of A × 1.1 ≦ B elastic modulus ≦ A elastic modulus × 3
Is preferably satisfied. If the difference in elastic modulus between these regions A and B is not 1.1 times or more, the effect is small. On the other hand, if the difference is 3 times or more, the physical properties of the rubber are too different, and peeling failure may occur at the interface between the rubber and the rubber. More preferably, the following formula:
Elastic modulus of A × 1.25 ≦ B elastic modulus ≦ A elastic modulus × 2
More preferably, the difference in elastic modulus between the regions A and B is 25% or more and 200% or less. If it is 25% or more, the effect becomes clearer. The same applies to the difference in elastic modulus between the regions B and C.

  In the present invention, the elastic modulus of each region is set to a value at a temperature of 40 ° C., because when the general user travels on a general road, the temperature of the tread shoulder portion becomes about 40 ° C. during the turn. . Since the tread shoulder is used only during turning, the temperature rises only during turning. In the case of a straight road, the tread rubber on the tread side is almost close to the air temperature, but the temperature rises instantaneously during turning. Although the temperature fluctuates in summer, winter and other environments (foreign countries, etc.), in the present invention, it is defined as 40 ° C. on average.

  Preferably, in the present invention, the average elastic modulus at 100% elongation at 40 ° C. of each of the tread rubbers in the regions A, B, and C satisfies the relationship of region B> region C> region A.

  There is a difference between the region A and the region C, and the region A does not become the center of the ground contact shape. That is, since the region A is on the tread end side in the tread side portion, it is always the end portion of the ground shape. On the other hand, in the region C, when the vehicle body is raised from a state of CA 45 ° to 50 ° and becomes CA 40 ° or CA 35 °, the region C may not be an end of the ground shape but a center portion of the ground shape. In other words, if the ground contact state near the maximum bank angle of the motorcycle is FIG. 5, the region A always shows the braking behavior of the region A, but the region C is not always in the driving state, and the region C Located in the center of the ground, it changes from driving to neutral. Furthermore, when it becomes the center of ground contact, it becomes the center of FIG. 6, and becomes the area | region which earns the camber thrust most.

  As described above, the region A is always used in the same way, but in the region C, it may be better to increase or decrease the elastic modulus depending on the bank angle of the vehicle. From this point of view, the area A is always soft rubber. In particular, especially in the case of a motorcycle race, since the frequency of use of an angle of CA 45 ° to 50 ° is clearly large, it is preferable that the region B is weighted and the region B is hard. As for the area C, since this portion is frequently used at CA 45 ° to 50 °, it is better to be softer than the area B. On the other hand, since it can be the center of grounding at CA 40 ° or CA 35 °, It is better to have a hardness of. Therefore, the elastic modulus has a grip performance not only in the case of CA 45 ° to 50 °, but also in the case of a bank angle slightly raised from this angle in the order of region B> region C> region A. It is suitable for maintaining.

In the present invention, the tread rubber in the region B is composed of two layers of the inner side and the outer side, and the elastic modulus at 100% elongation of the inner tread rubber at 40 ° C. is 100% of the outer tread rubber at 40 ° C. It is preferable to make it higher than the elastic modulus at the time of elongation. This is due to two reasons.

  The first is a manufacturing reason. In manufacturing a tire for a motorcycle, increasing the rubber type of the tread part unnecessarily leads to an increase in manufacturing cost. At most, about 4 types are the limits in terms of cost, and if the number of rubber types is increased further, the profitability cannot be obtained. Therefore, if an area in which two hard rubbers and soft rubbers are overlapped in two steps is formed, the elastic modulus can be controlled by the overlapping method.

  Another reason is grip strength. If the surface of the tire tread is made of soft rubber, the rubber can bite into the unevenness of the road surface, and the gripping power increases. That is, hard rubber is disposed inside the tread to ensure the rigidity of the tread, and the outer tread surface is softened to ensure biting into the road surface. In consideration of this, it is effective to double the tread rubber as described above.

  Furthermore, in the present invention, it is also preferable that the tread rubber forming the tread surface of the region A and the region B is made of the same kind of rubber. If the tread surface is covered with the same kind of rubber in the areas A and B, the rubber type can be saved. In this case, the average elastic modulus of the region B can be made harder than that of the region A by arranging hard rubber inside the region B.

  In the present invention, when assuming a motorcycle tire for sports or a motorcycle tire for racing, the average elastic modulus at 100% elongation at 40 ° C. is the average elastic modulus at 100% elongation at 100 ° C. And In such a motorbike, not only going straight but also cornering at high speed. Therefore, the temperature of the tread side portion reaches 100 ° C. or more. In particular, in a motorcycle race, since the corners are continuous, the temperature on the side of the tread is hardly lowered and may reach 120 ° C. In consideration of such a situation, in the case of a tire for a race or a tire for a sports motorcycle, it is necessary to satisfy the above-described conditions of the present invention regarding the average elastic modulus at 100 ° C.

  In the tire of the present invention, it is important to satisfy the above conditions for the tread rubber constituting the tread portion, whereby the desired effect of the present invention can be obtained, and other tire structures, materials, etc. The conditions are not particularly limited. For example, the tread rubber at the tread center portion is not particularly limited in the present invention, and may be the same as or different from the tread side portion. For example, the tread center portion often cruises at a high speed when standing upright, so the rubber and rubber type of the tread side portion are often changed by using rubber having excellent heat resistance.

  Preferably, a spiral belt layer having reinforcing elements having an angle of 0 to 3 ° with respect to the tire circumferential direction is disposed as the belt layer 3 to prevent expansion due to centrifugal force during high-speed running. In addition, the handling stability at high speed can be increased.

  In this case, as shown in the figure, there may be a case where only the spiral belt layer 3 is provided and no other crossing belt layer is provided. However, in addition to the spiral belt layer, a crossing belt layer may be additionally provided. For example, cords twisted with aromatic polyamide can be added by crossing at ± 60 ° with respect to the tire circumferential direction. Alternatively, the spiral belt layer may be doubled, or a belt having an angle of 90 ° with respect to the tire circumferential direction may be added in addition to the spiral belt layer to form a mesh with the spiral belt layer and strengthen it. It doesn't matter. Moreover, you may comprise a belt layer only with two or three or more crossing belt layers, without using a spiral belt layer. In this case, for example, a belt in which two cords twisted with aromatic polyamide are crossed at ± 30 ° with respect to the tire circumferential direction can be used as the belt layer.

  Further, for example, the tire of the present invention includes a pair of bead portions 11, a pair of sidewall portions 13 that are continuous with the bead portions 11, and a tread portion 12 that is continuous in a toroidal shape between the sidewall portions 13. The carcass 2 that reinforces each part between the bead parts includes at least one carcass ply formed by arranging relatively highly elastic textile cords in parallel with each other. The number of carcass plies may be one or two, or three or more. In the illustrated example, both ends of the carcass 2 are folded and locked to the bead core 1 from the inside to the outside of the tire, but the end of the carcass 2 is sandwiched between a bead wire and a bead wire. The end of the carcass 2 may be anchored to the bead core 1. Further, an inner liner is disposed on the innermost layer of the tire (not shown), and a tread pattern is appropriately formed on the surface of the tread portion 12 (not shown). The present invention is applicable not only to radial tires but also to bias tires.

Hereinafter, the present invention will be specifically described with reference to examples.
According to the following conditions, test tires having a cross-sectional structure shown in FIG. Each test tire is provided with two carcass 2 straddling a toroidal shape between a pair of bead portions 11, and a nylon cord is used for the carcass 2 in both the conventional example and the example (the carcass in the figure). 2 is indicated by a single line, but two are overlapping). The cord angle of the two carcass 2 may be in the radial direction (the angle with respect to the tire circumferential direction is 90 °), but in this embodiment, the ones having an angle with respect to the tire circumferential direction of ± 70 ° are used in a crossing manner.

  A spiral belt layer 3 is disposed on the outer side in the radial direction of the carcass 2. The spiral belt layer 3 is formed by winding a steel cord twisted by a 1 × 5 type steel single wire having a diameter of 0.12 mm and winding it in a spiral shape at an interval of 80/50 mm. A belt-like body (strip) in which the cord is embedded in the covering rubber is manufactured by a method of winding in the tire rotation axis direction in a spiral manner substantially along the tire circumferential direction. As shown in the figure, in the tire of this example, the belt layer was only a steel spiral belt layer, and no other crossing layer was provided. A tread portion 12 having a thickness of 7 mm is provided on the outer side of the spiral belt layer 3, and no groove is arranged on the surface of the tread portion 12 in the tires of the conventional example and the example.

  Based on the above structure, in the tread portion 12, a region of 50% of the tread deployment width centered on the tire equator plane is a tread center portion, and a region of 25% of each tread deployment width on both sides thereof is a tread side portion. Further, when the tread side portion is equally divided into three regions A, B and C from the end of the tread, the tread rubbers of these regions A to C are respectively changed according to the following, and each conventional example and example The test tire was manufactured. In this example, in order to perform an evaluation test of the test tire on a circuit, the tire was positioned for sports use, and the elastic modulus at 100 ° C. was used.

<Conventional example>
As shown in FIG. 4, the entire region of the tread portion 12 composed of the tread center portion and the tread side portion was made of a single kind of rubber. The elastic modulus at 100% elongation of this tread rubber is taken as 100.

<Example 1>
As shown in FIG. 1, only the tread rubber physical property of the region B in the tread side portion was changed, and the elastic modulus at 100% elongation of the region B was set to 150.

<Example 2>
As shown in FIG. 2, only the tread rubber in the region B of the tread side portion is composed of two layers of the inner side and the outer side, and the outer tread rubber is the same rubber as the region A, and the tread rubber physical properties of the inner tread rubber are as follows. Only changed. The thickness of the two layers is 4 mm on the inner side and 3 mm on the outer side. The elastic modulus at 100% elongation of the outer tread rubber was 100, and the elastic modulus at 100% elongation of the inner tread rubber was 150. Accordingly, the average elastic modulus of the region B was 129.

<Example 3>
As shown in FIG. 3, among the tread side portions, the region B is composed of an inner tread rubber thickness of 4 mm and an outer tread rubber thickness of 3 mm, and the region C is composed of an inner tread rubber thickness of 2 mm and an outer tread rubber thickness of 5 mm. It consisted of Region A consists of one layer. The boundary between the inner tread rubber and the outer tread rubber is slanted at the boundary between the region A and the region B and the boundary between the region B and the region C. This is rather than making a sharp corner. This is because peeling and breaking at the rubber-to-rubber interface is less likely to occur at an inclined and smooth boundary as shown in the figure. In Example 3, similarly to Example 2, the elastic modulus at 100% elongation of the inner tread rubber was 150, and the elastic modulus at 100% elongation of the outer tread rubber was 100. In addition, the average elasticity modulus of the area | region A in Example 3, the area | region B, and the area | region C is set to 100: 129: 114, and is the order of area | region B> area | region C> area | region A.

<Example 4>
As in Example 2, only the tread rubber in the region B of the tread side portion is composed of two layers of the inner side and the outer side, and the outer tread rubber is the same rubber as the region A, and is 100% of the inner tread rubber. The elastic modulus at time was 200. The other conditions were the same as in Example 2. The average elastic modulus of region B was 157.

<Example 5>
As in Example 2, only the tread rubber in the region B of the tread side portion is composed of two layers of the inner side and the outer side, and the outer tread rubber is the same rubber as the region A, and is 100% of the inner tread rubber. The elastic modulus at the time was 300. The other conditions were the same as in Example 2. The average elastic modulus of region B was 214.

<Side force evaluation>
For each test tire, the camber thrust was measured using a 3 m drum. Using a steel drum with a diameter of 3 m, each test tire was pressed at CA 40 ° and CA 50 °, and the camber thrust (lateral force Fy) at that time was measured. Since the surface of the drum was smooth, sandpaper having a roughness of # 40 was pasted on the drum circumference to make it look like a road surface. Each test tire was filled with an internal pressure of 210 kPa, rolled at a speed of 80 km / h, a load of 1500 N (about 150 kgf), and an SA (slip angle) of 0 °, and a lateral force for two levels of CA 40 ° and 50 °. Was measured. Since the speed was as high as 80 km / h, the tire generated heat and the tread side temperature was 110 ° C.

  The tires according to the conventional examples have a lateral force Fy value 1350N at CA 40 ° of 100 and a lateral force Fy value 1490N at CA 50 ° of 100, and each example at CA 40 ° and 50 ° respectively. The value of the lateral force Fy of the test tires was shown as an index. The results are shown in Table 1 below. The larger the value, the greater the lateral force.

＊１）各領域の弾性率は、各領域の温度１００℃における１００％伸び時の弾性率を意味し、各領域に２種類以上のゴムが存在するときは、それらの体積を考慮した平均弾性率である。

* 1) The elastic modulus of each region means the elastic modulus at 100% elongation at a temperature of 100 ° C. When there are two or more kinds of rubber in each region, the average elasticity considering their volume Rate.

  Although the present invention is targeted near the maximum bank angle (bank angle = CA) having a CA of 45 ° to 50 °, as is clear from Table 1 above, in the test tires of Examples 1 to 5, In any case, the CA50 ° Fy on the drum is improved.

  Also, from the comparison of Example 2, Example 4 and Example 5, if the elastic modulus of region B is about 130, the effect of improving Fy is clear, and if the elastic modulus of region B is about 160, the effect is improved. It is getting bigger. However, when the elastic modulus of the region B is about 210, the effect tends to be slightly dull, and the elastic modulus of about 150 seems to be the best.

  In Example 3, CA40 ° Fy is also effectively increased. This is because by slightly strengthening the region C, the effect is exhibited even at CA 40 ° where the region C is the center of grounding.

<Real car test>
Next, in order to confirm the performance improvement effect of the two-wheeled vehicle tire of the present invention, a result of a steering performance comparison test using an actual vehicle will be described. Since the test tire was a rear tire, the rear-only tire was replaced, and the front tire was always fixed with a conventional tire for an actual vehicle test. The evaluation method is shown below. The tire tread temperature after running was around 100 ° C.

  The above test tires were mounted on a 1000cc sports type motorcycle, allowed to run for 10 laps on the test course, and the steering stability (corning performance) during turning when the vehicle was largely defeated was evaluated. A comprehensive evaluation was performed using a 10-point method based on the feeling of the test rider. The rider made a limit run. The results are also shown in Table 1 above.

  The results showed almost the same tendency as the indoor Fy measurement results. What is characteristic is a comparison between Example 1 and Example 4. The elastic modulus of region B is an equivalent value, but Example 4 clearly has a higher score. This is presumably because Example 4 was made of soft rubber on the surface of the region B, so that the rubber bite into the rough irregularities of the road surface and gripped.

  Next, Example 3 has obtained the highest score of 9 points. This is because the rider evaluated the grip height of CA 40 °.

<Abrasion evaluation>
Finally, the amount of wear of each test tire was compared. The amount of wear was determined by measuring the weight of the tire when it was new, measuring the weight of the tire after the test run, and evaluating the difference in weight. Since the wear occurred almost on the side of the tread, this is considered to correspond to the amount of wear on the side. As a result, it was found that in the test tires of Examples 1 to 5, the wear amount was 7% to 15% less than the conventional examples.

  From the above, it can be said that the tire of the example has both a grip during turning and wear resistance. That is, it was confirmed that the performance of the test tires of each example according to the present invention was significantly improved as compared with the conventional tires.

1 is a cross-sectional view in the width direction showing a pneumatic tire for a motorcycle according to an embodiment of the present invention. 1 is a cross-sectional view in a width direction showing a pneumatic tire for a motorcycle according to Examples 2, 4, and 5. FIG. 6 is a cross-sectional view in the width direction showing a pneumatic tire for a motorcycle according to Embodiment 3. FIG. FIG. 3 is a cross-sectional view in the width direction showing a motorcycle pneumatic tire according to Conventional Example 1; FIG. 2 is a cross-sectional view in the width direction showing a grounding state of a pneumatic tire for a motorcycle when the vehicle body is largely turned, and (b) an explanatory diagram showing a grounding shape and a deformed state of a tread portion (tire circumferential direction). . FIG. 6 is a (a) cross-sectional view showing a ground contact state of a pneumatic tire for a motorcycle when the vehicle body is largely turned, and (b) an explanatory diagram showing a ground contact shape and a tread portion deformed state (tire width direction). .

Explanation of symbols

1 Bead core 2 Carcass 3 Belt layer 10 Pneumatic tire for motorcycle 11 Bead portion 12 Tread portion 13 Side wall portion

Claims (7)

A bead core embedded in each of the pair of left and right bead portions, at least one carcass extending across the toroid between the pair of bead portions, and at least one sheet disposed on the outer side in the tire radial direction of the carcass A pneumatic tire for a motorcycle having a belt layer and a tread portion arranged on the outer side in the tire radial direction of the belt layer,
Of the tread portion, a region of 50% of the tread development width centered on the tire equator plane is a tread center portion, a region of 25% of each tread development width on both sides of the tread center portion is a tread side portion, and When the tread side is divided into three equal parts from the tread edge to area A, area B, and area C,
The average elastic modulus at 100% elongation of the tread rubber in region B at 40 ° C. is higher than the average elastic modulus at 100% elongation of the tread rubber in region A and region C at 40 ° C. Pneumatic tire for motorcycles.   2. The motorcycle air according to claim 1, wherein the average elastic modulus at 100% elongation at 40 ° C. of the tread rubber in each of the regions A, B, and C satisfies the relationship of region B> region C> region A. Enter tire. The tread rubber in the region B is composed of two layers of an inner side and an outer side, and the elastic modulus at 100% elongation of the inner tread rubber at 40 ° C. is larger than the elastic modulus at 100% elongation of the outer tread rubber at 40 ° C. The pneumatic tire for a motorcycle according to claim 1 or 2, wherein the pneumatic tire is high. A bead core embedded in each of the pair of left and right bead portions, at least one carcass extending across the toroid between the pair of bead portions, and at least one sheet disposed on the outer side in the tire radial direction of the carcass A pneumatic tire for a motorcycle having a belt layer and a tread portion arranged on the outer side in the tire radial direction of the belt layer,
Of the tread portion, a region of 50% of the tread development width centered on the tire equator plane is a tread center portion, a region of 25% of each tread development width on both sides of the tread center portion is a tread side portion, and When the tread side is divided into three equal parts from the tread edge to area A, area B, and area C,
The average elastic modulus at 100% elongation of the tread rubber in region B at 100 ° C. is higher than the average elastic modulus at 100% elongation of the tread rubber in region A and region C at 100 ° C. Pneumatic tire for motorcycles. The motorcycle air according to claim 4, wherein the average elastic modulus at 100% elongation at 100 ° C. of the tread rubber in each of the regions A, B, and C satisfies the relationship of region B> region C> region A. Enter tire. The tread rubber in the region B is composed of two layers of an inner side and an outer side, and the elastic modulus at 100% elongation of the inner tread rubber at 100 ° C. is larger than the elastic modulus at 100% elongation of the outer tread rubber at 100 ° C. The pneumatic tire for a motorcycle according to claim 4 or 5, wherein the pneumatic tire is high. The pneumatic tire for a motorcycle according to any one of claims 1 to 6 , wherein the tread rubber forming the tread surfaces of the region A and the region B is made of the same kind of rubber.

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