JP5182662B2 - 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 an improvement in a tread portion.

  Since motorcycles have the feature of turning with the vehicle body tilted, the portion of the tire that contacts the road surface moves due to the vehicle body inclination. In addition, the speed is high when standing upright and a force in the front-rear direction of the braking force and driving force (the equator direction of the tire) is applied, but a large lateral force is mainly applied when turning the vehicle body. Therefore, a lateral grip is required at the shoulder portion of the motorcycle tire.

  On the other hand, as for the center part of a motorcycle tire, a commercially available tire often uses a rubber having high wear resistance because the frequency of straight running is high. Also, in racing and competition tires, because the speed when going straight is very high, rubber that does not generate heat easily is placed in the tread center part, or the tread center part has a two-layer structure and rubber that does not generate heat easily inside The rubber has been devised such as placing rubber with high grip on the outside.

  In particular, when a motorcycle race or a general consumer rides hard, tire shoulders generate heat during driving, resulting in deterioration of turning performance, progress of wear on the shoulders, shoulders. Deterioration of rubber occurs.

  On the other hand, 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 is high. On the other hand, soft rubber has the property of fast wear. Further, the softness of rubber can be expressed by hardness, that is, Shore A hardness, and rubber having a small Shore A hardness is soft and has a high grip but a poor wear resistance.

Since the two-wheeled vehicle has the characteristic of turning by tilting the vehicle body and the characteristic of the tread part that touches the road surface moving by the inclination of the vehicle body, the function of the tread of a motorcycle is separated between the center part and the shoulder part. A plurality of different rubbers may be used. For example, Patent Documents 1 and 2 disclose a technique in which a tread portion of a motorcycle tire is divided into a center portion and a shoulder portion, and the rubber physical properties are changed in each. Patent Document 3 discloses a pneumatic tire in which the tread portion is composed of two layers of a cap rubber and a base rubber, and the rubber physical properties of each rubber are changed. Patent Document 4 discloses a tread shoulder. A motorcycle tire is disclosed in which a part is formed by laminating an inner layer made of a high hardness crosslinked rubber and an outer layer made of a low hardness crosslinked rubber. These Patent Documents 3 and 4 relate to techniques for changing rubber physical properties in the tire thickness direction.
JP 2000-158910 A (Claims etc.) JP-A-7-108805 (Claims etc.) JP 2006-76355 A (Claims etc.) JP 2005-271760 A (Claims etc.)

  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 between straight traveling and 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.

  Especially when turning, it is required to grip the tire in the lateral direction (width direction), but in order to turn the motorcycle faster, it is necessary to tilt the vehicle body to balance the centrifugal force that increases with the turning speed. In addition, the tire must be able to grip so that it can resist 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 influence of the grip here on the turning performance is very large. On the other hand, since a large burden is applied to the end portion of the tread due to the lateral force applied at the time of turning, it is an important issue for suppressing wear associated with traveling.

  Therefore, in addition to excellent grip performance during turning, that is, steering stability performance, the shoulder portion of a motorcycle tire is required to be able to suppress tread wear during traveling, and these requirements are highly satisfied. There was a need for a pneumatic tire for motorcycles to obtain.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire for a motorcycle that suppresses wear on a tread shoulder portion and improves steering stability performance (lateral grip) during turning.

  The present inventors have intensively studied to further improve the grip when turning in a motorcycle tire, and in particular, a bank angle at which a motorcycle is most inclined (camber angle, hereinafter referred to as “CA” as a camber angle) 45 to 45. We worked on intensively improving the grip around 50 degrees. This is because, for example, in a race, the turning speed is very important, and if the turning speed is high, the speed of the straight next to the corner is also increased, and as a result, the lap time is improved. In addition, when driving on ordinary roads, it is possible to contribute to safety by increasing the grip during turning.

  In a tire for a motorcycle, particularly with respect to turning performance when the vehicle body is greatly tilted, the end of one side of the tread of the tire is grounded to generate a grip. When the vehicle is turned with the vehicle body largely lowered, the tire is in a ground contact state as shown in FIG. The ground contact shape at this time will be considered.

  When the motorcycle body turns significantly and turns, that is, when the tire CA turns at 45 to 55 degrees, approximately 1/4 of the tire tread width (full width) is grounded. The 1/4 area that is in contact with the ground at the time of turning is divided into three equal parts, which are defined as area A, area B, and area C from the tread edge.

  Here, tread deformation in the cross section in the width direction of the tire is considered. This is because a lateral force is generated in the tire due to the deformation of the tread. The deformation of the lateral tread generates a camber thrust (lateral force).

  FIG. 4 shows a cross section when the tire is grounded and rotating at 50 degrees CA. The shape of the ground contact portion is shown below the tire cross section. As shown in the figure, depending on each tire, the ground contact shape may be a shape with a part of an ellipse missing or a half-moon shape.

  The deformation in the width direction of the tread in the region B in the case of the substantially elliptical ground contact shape of FIG. 4 will be described. Assuming that the surface of the tread in region B, that is, the point in contact with the road surface is Q, and the deepest point of the tread inside Q point is P point, these P point and Q point are as shown in the figure at the time of ground rolling. Draw a trajectory. Point P is the point where the tread is in contact with the tire belt (frame member). Since the tire rolls with the CA attached, it draws a bow-like curve. On the other hand, the point Q is fixed to the road surface when the tread surface contacts the road surface and moves linearly in the direction of the road surface, that is, in the tire traveling direction. This difference in movement causes the tread to undergo transverse shear. This is just a bow-string relationship and is subject to maximum lateral shear directly under the load. The tread undergoes lateral deformation by this lateral shearing amount, and the tread is sheared laterally, so that lateral force (camber thrust) is generated.

  Due to this mechanism of camber thrust generation, the longer the contact length (the contact shape of the tire in the circumferential direction = the length in the equator direction), the greater the difference in the trajectory between points P and Q, and the greater the tread is sheared. become. On the contrary, when the contact length is short, the amount of shearing of the tread (lateral direction = shear in the tire width direction) is small. Therefore, as shown in the figure, when the ground contact shape is substantially elliptical, the region B receives the largest shear, the region A has the largest shear, and the region C has the less shear. On the other hand, when the ground contact shape is a half-moon shape, the region B and the region A receive a large shear, and the region C has a small shear. That is, in the turning at the time of 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 to CA 45 ° to 55 ° 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 in an area where the inclination is slightly restored after the motorcycle is greatly inclined, that is, in the vicinity of CA 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 tread wear proceeds.

In summary, the following can be said.
Area A: Used only when the maximum CA (45 degrees to 55 degrees), and receives a lateral input. This greatly contributes to the occurrence of lateral grip 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 occurrence of lateral grip at the maximum CA (especially when the ground contact shape is elliptical). In addition, it is grounded at 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 in particular, in the case of a rear tire, it is used mainly at the start of full-scale acceleration at 40 degrees CA, so it is a part with severe wear. Compared with the area A and the area B, the frequency of use is clearly higher. Further, when the angle is CA 40 degrees, it becomes the center of the ground contact shape, and the ground contact length is extended, so that the shear in the lateral direction is increased and the wear is severe.

  Another characteristic may be due to the characteristics of the mechanism of camber thrust generation in motorcycle tires. The difference between the trajectories of point P and point Q shown in FIG. 4 is the amount of lateral deformation of the tread, and this amount of lateral deformation is a constant displacement. That is, since this trajectory is determined by the geometric factor of the tire, the maximum lateral shearing amount is a constant amount. In a normal tire, the amount of lateral shear in region B in FIG. 4 at the time of large CA is about 7 mm. Therefore, regardless of whether the tread rubber is hard or soft, the lateral shearing amount is a constant value of about 7 mm. That is, when the tread rubber is soft, the displacement is constant, so that the force for deforming the tread is small, that is, the generated lateral force is small. On the contrary, if the rubber of the tread is hard, a large force is required to laterally deform the tread by a certain amount, that is, the generated lateral force (camber thrust) becomes large. In other words, the magnitude of the camber thrust (lateral force) depends largely on the rigidity of the tread (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.If the rubber is too hard, the surface of the tread slips, and slipping reduces the amount of displacement, resulting in lateral force. Disappears.

  From the above viewpoint, as a result of further study, the present inventors have examined the portion of the tread shoulder portion that contributes to the grip from the region A to the region B of the tread surface that contributes to the generation of lateral force at the maximum CA, and the use It has been found that the above-mentioned problems can be solved by arranging different rubbers for the region C having high frequency and high wear, and the present invention has been completed.

That is, the pneumatic tire for a motorcycle of the present invention is a pneumatic tire for a motorcycle including a tread portion formed in an annular shape.
Dissimilar rubber is disposed on both ends of the tread surface in the tire width direction, the disposition width of the dissimilar rubber on the tread surface is within a range of 5% to 14% of the tread development width from the tread end, and Shore a hardness of dissimilar rubber, rather smaller than the Shore a hardness of the rubber disposed adjacent in the tire width direction inner side of said heterologous rubber,
Of the tread portion, at least 15% of the tread development width centered on the tire equator plane is made of two types of rubber laminated in the thickness direction, and the portion made of the two types of rubber and the different type The tread between the two ends where the rubber is placed is formed in one layer,
Of the two kinds of laminated rubber, the surface rubber and the rubber adjacent to the different rubber are made of the same kind of rubber .

  In the present invention, the disposition width of the dissimilar rubber preferably increases from the tread surface toward the inside in the tire radial direction, and the dissimilar rubber thickness is preferably 20% to 70% of the total thickness of the tread rubber. It is as follows. Further, in the present invention, the average thickness of the tread rubber in the range from the tread end to 10% of the tread development width is from 10% to 25% of the tread development width based on the tread end. It is preferably smaller than the average thickness.

  Furthermore, in the present invention, it is preferable that a hard rubber having a thickness of 6 mm or less is disposed on at least a part of the wall surface portion at the tread end.

  Furthermore, in the present invention, it is preferable that at least a part of the tread portion is formed by winding a narrow and long rubber strip spirally in the tire circumferential direction. Furthermore, the tire of the present invention preferably includes a spiral belt having an angle with respect to the tire circumferential direction of 0 to 5 degrees on the inner side in the crown portion tire radial direction of the tread portion. Preferably, a belt layer having an angle with respect to the tire circumferential direction of 80 degrees or more and 90 degrees or less is provided between the tread portion and the spiral belt, and at least part of the thickness between the spiral belt and the belt layer has a thickness. It is more preferable to have a buffer rubber layer of 0.3 mm or more and 3 mm or less.

  According to the present invention, by adopting the above-described configuration, the pneumatic stability for a two-wheeled vehicle that improves the steering stability performance (lateral grip) at the time of turning, particularly at the time of turning at a large CA, while suppressing wear of the tread shoulder portion. It became possible to realize tires. Further, in the present invention, a lateral grip can be maintained even when worn, and a tire excellent in grip and wear resistance can be provided particularly when used as a racing tire.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view in the width direction of a pneumatic tire for a motorcycle according to a preferred embodiment of the present invention. As shown in the figure, the motorcycle tire of the present invention includes a pair of bead cores 1 embedded in a pair of left and right bead portions 11 and at least one extending from one bead portion to the other bead portion in a toroidal shape. The carcass 2 is provided, at least one belt 3 arranged on the outer side in the tire radial direction, and a tread portion 12 formed in an annular shape and arranged on the outer side in the radial direction.

  In the tire of the present invention, different types of rubber 6 are disposed at both ends in the tire width direction on the surface of the tread portion 12, and the arrangement width of the different types of rubber 6 on the tread surface is 5% to 14% of the tread developed width from the tread end. Is within the range. Here, deploying 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, and the tread deployment width is a cross section of the tread in the tire width direction cross section. It is the width along the curved surface of the tread surface from one end to the other end. In the present invention, when the developed width is 100, soft different rubber 6 having a predetermined physical property value is disposed on the surface in the range of 5 to 14 from the tread edge at both ends in the tire width direction of the tread. Yes. The definition of the arrangement width is the width on the surface of the tread portion, and the width on the surface of the tread is the above-described arrangement width even when the width of the different rubber 6 is different in the depth direction.

  That is, in the present invention, at both ends of the tread, the rubber type is changed between the tread surface and the inside of the tread, and soft rubber is disposed on the tread surface. The reason why soft rubber is disposed on the tread surface at the end of the tread is that the soft rubber bites into the fine irregularities of the aggregate such as asphalt, and the friction coefficient is increased to improve the grip. On the other hand, as described above, the lateral displacement of the shoulder tread of a two-wheeled vehicle is geometrically determined. If all of the tread is softened, the shear rigidity of the tread decreases, and a large lateral force cannot be generated. . Therefore, only the tread surface is softened. Here, disposing different types of rubber on the tread surface in the present invention means that the tread has a laminated structure with the different types of rubber as the surface layer at least at both ends in the tire width direction.

  The hardness of the dissimilar rubber 6 used in the present invention is defined by the Shore A hardness. That is, as the different rubber 6, it is necessary to use a rubber having a Shore A hardness smaller than that of the rubber disposed adjacent to the inner side in the tire width direction of the different rubber 6. In the present invention, the temperature for measuring the Shore A hardness of the dissimilar rubber 6 can be 50 ° C. or 100 ° C. or higher, and it is preferable to use the Shore A hardness at 50 ° C. as an index for general consumer tires. However, in the case of racing tires for motorcycles in particular, the tread temperature of the shoulder portion may exceed 100 ° C., so the Shore A hardness at 100 ° C. or higher, for example, 100 ° C. is used according to the purpose. The Shore A hardness can be measured using a commercially available hardness meter. For example, after tread rubber is cut out and stored in a high temperature chamber kept at 50 ° C. for 30 minutes to bring the rubber temperature to 50 ° C., the hardness meter The hardness can be measured with

  Further, as an index of the hardness of the different rubber 6, the dynamic elastic modulus E 'may be used as a substitute for the Shore A hardness. Usually, a material having a high hardness also has a high dynamic elastic modulus. 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, specifically, for example, manufactured by Rheometrics It can measure using a viscoelasticity measuring apparatus. Also in this case, the measurement temperature can be 50 ° C., 100 ° C., or higher. When the dynamic elastic modulus E ′ is used, a rubber having a smaller dynamic elastic modulus E ′ than the rubber disposed adjacent to the inner side in the tire width direction is used as the different rubber 6.

  The hardness of the different rubber 6 can be set to about 50 to 90% of the hardness of the adjacent rubber (that is, the Shore A hardness or the dynamic elastic modulus E ′) when any of the above indices is used. If the different rubber 6 is too soft, the wear becomes intense, and uneven wear in which only the different rubber is worn tends to occur. On the other hand, if it is too hard, the difference between the different rubber and the adjacent rubber is reduced, and the effect of the present invention is reduced. Neither is preferred.

  In the present invention, the reason why the disposition width of the different rubber 6 is 5% or more and 14% or less of the tread development width is based on how the tread is used at the time of large CA as described with reference to FIG. In FIG. 4, the area grounded at the time of large CA is a quarter of the developed width of the tread, that is, an area of 25%. The region A and region B in FIG. 4 contribute to the lateral force, that is, about half of 25%, and the region of 12.5% from the end of the tread contributes to the lateral force. In particular, the region A is a portion that is grounded only at CA 45 to 55 degrees, and generates a large lateral force only at the time of large CA. Region A is a region from the tread edge to about 8% of the tread deployment width.

  From the ground contact characteristics at the time of large CA, if the disposition width of the different rubber 6 is less than 5% of the tread development width, it is included in the region A in FIG. 4, but the range is too narrow and the effect is reduced. On the other hand, if it exceeds 14%, it is an area used other than the maximum CA time, which is represented by area C in FIG. 4, that is, an area that is frequently used, and is soft up to an area where a large driving force is applied at CA 40 degrees. Since rubber is arranged, wear proceeds when a soft different rubber is arranged on the tread surface. The soft rubber is preferably used only at the time of large CA (ie, less frequently used) because of its function, and is preferably disposed at a site that contributes to the lateral grip. Therefore, it is set to 5% or more and 14% or less of the tread development width. More preferably, it is 8% or more and 14% or less, More preferably, it is the range of 10%-12.5%.

  Further, regarding the hardness of the different rubber 6, the comparison object is a surface rubber arranged on the tire center side of the different rubber 6. The rubber on the center side is a portion corresponding to the region C in FIG. 4, that is, a severely worn rubber used at the time of acceleration at CA 40 degrees, and is compared with this. In the present invention, the different kind of rubber 6 needs to be softer than the rubber in this part. A rubber harder than the different rubber is used on the inner side of the different rubber 6. If this hard rubber is the same as the surface rubber on the tire center side, it is preferable because the production is efficient. In addition, it is the area | region C of FIG. 4 that becomes the ground contact center of a tire at CA 40 degree | times, and this part is an area | region of about 16%-25% from a tread edge part, if a tread edge part is made into a base point. If a soft rubber is placed in this portion, the rubber on the surface will be worn early due to severe input during acceleration.

  Note that Patent Document 4 describes that a low-hardness cross-linked rubber is disposed on the outer layer of the shoulder portion, and a range of a surface distance of 15% to 30% from the tread end portion is disclosed with regard to a preferable range thereof. However, since the region C in FIG. 4 is also included in this range, the wear proceeds very quickly especially when soft rubber is used in the region of 16% or more starting from the tread edge. Therefore, uneven wear occurs at the end of the tread, and steering stability performance is impaired due to wear. When this is used for ordinary tires, as the wear progresses, the tires are more likely to skid during acceleration, and from the consumer's standpoint, wear on the shoulders of the tires progresses and the grooves partially disappear. Therefore, it is easy to be evaluated as a tire with poor wear performance. On the other hand, when used for motorcycle competitions such as racing, the soft rubber in the region of 16% to 30% from the end of the tread wears early in the course of running the race distance, and hard rubber appears from the inside. Although the initial grip is high, the grip is lost later in the race, and a stable grip cannot be maintained throughout one race. In the present invention, unlike the above-mentioned patent document 4, the problem due to the progress of wear is also taken into consideration, and the part where the soft rubber is arranged is the part used only at the time of large CA, and not the traction but only the lateral force. By using only a portion that is less frequently used but greatly contributes to the lateral grip, the wear does not progress even when soft rubber is used while maintaining the height of the grip.

  FIG. 3A shows an enlarged partial cross-sectional view of a disposition site of different types of rubber. As shown in the figure, the dissimilar rubber 6 can be arranged without changing the arrangement width in the depth direction, but as shown in FIG. It can also be arranged to increase inward in the direction. That is, in this case, as wear progresses, the exposed amount (exposed area) of the soft different rubber 16 at the end of the tread increases, and the width of the different rubber 16 increases in the depth direction. When the tread of the tire is worn, the thickness of the tread is reduced, so that the rigidity of the tread is increased and the surface of the tread rubber is easily slipped from the road surface. Therefore, although the grip force tends to decrease, the effect of compensating the grip force can be obtained by increasing the exposure of the dissimilar rubber 16 due to wear as the configuration shown in FIG. Especially for racing tires, it is important to maintain the grip of the tire even if the race progresses and the number of laps increases. With such a configuration, the range of soft rubber increases even if the wear progresses. Therefore, it is possible to maintain the grip by increasing the region having a high friction coefficient.

  Further, the thickness of the different rubber is preferably 20% to 70% of the total thickness of the tread rubber. If the thickness of the dissimilar rubber is less than 20%, the surface rubber layer is too thin, and even if the rubber is soft, it is difficult to bite into the unevenness of the road surface. There is also a concern that it will wear out quickly. On the other hand, if the thickness of the dissimilar rubber exceeds 70%, there is a wide soft rubber layer in the thickness direction of the tread, so the overall rigidity of the tread decreases and the lateral grip (lateral force = camber thrust) decreases. To do. The thickness is more preferably 40% to 70% in order to maintain the grip force even after wear. In particular, since a commercially available tire is used until it is relatively worn, the thickness is preferably thick, and 40 to 70% is preferable. On the other hand, some of the tires for competition are intended to run faster by one lap, such as a tire used for qualifying. In such a tire, from the balance between rigidity and grip, the thickness is preferably thin, and 20% to 40% is appropriate.

  In the present invention, the average thickness of the tread rubber in the range from the tread end to 10% of the tread development width is the average thickness of the tread rubber in the range from 10% to 25% of the tread development width based on the tread end. It is preferable to make it smaller than the average thickness. That is, the thickness of the tread at the position where the soft different rubber is arranged is made thinner than the other portions. The range from the tread end to 10% of the tread development width corresponds to the location of such a different rubber, and the range from the tread end to 10% of the tread development width is the start point and 25% is the end point. Corresponds to the remaining grounding portion turning at 50 degrees CA. Thus, the tread rigidity is improved by thinning the portion where the soft rubber is disposed. That is, the overall thickness of the tread is reduced by the softening of the rubber. Since the tread rigidity is proportional to the cube of the thickness, for example, when the thickness of the tread is 8 mm, about 0.5 mm to 1.5 mm has a sufficient effect.

  If the entire thickness is reduced, the tread rigidity is improved, but the slip on the tire surface increases as a whole, and the wear life is reduced. Therefore, it is preferable to thin only the portion where the soft rubber is disposed.

  Moreover, in the tire of this invention, it is preferable that a tread center part consists of two types of rubber laminated | stacked on the thickness direction so that it may show in figure. Here, the tread center portion is a region of 25% of the tread developed width in the tread center portion. This is because the width in contact with the road surface when the bike is upright is about 25%. In this case, not all of the tread center portion may be formed of two layers, and at least most of them, specifically, at least 15% of the tread deployment width centered on the tire equator plane and two layers. If it is, an effect is acquired and it is suitable.

  The reason why the tread center portion is preferably formed of two layers is to suppress heat generation, that is, to suppress rolling resistance. For example, if hard rubber is arranged in the two inner layers and soft rubber is arranged in the outer layer, the outer rubber gains a grip and the inner rubber suppresses heat generation. Further, if rubber having a low loss tangent tan δ is used for the inner layer, heat generation of the rubber is further suppressed, and rolling resistance is improved. In particular, with commercially available tires, it takes a long time to travel straight, and considering the recent environment (low fuel consumption), it is important to suppress fuel consumption by suppressing rolling resistance during straight travel. For this reason, it is preferable to use a rubber having a low tan δ inside the tread of the tire center portion that contacts the ground when traveling straight. On the other hand, as for 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 is repeatedly deformed 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 is vaporized and bubbles are generated, and a failure may occur in which a part of the tread is chipped and scattered from the bubbles. For this reason, it is preferable to use a rubber with a very low loss tangent tan δ that does not easily generate heat in the tread, and a rubber with a high grip on the surface of the tread even in such an advanced competition tire. As a result, not only the large CA of 45 to 55 degrees CA, but also the driving and braking characteristics when traveling straight can be improved.

  In this case, it is preferable that the surface layer rubber in the tread center portion and the rubber adjacent to the different rubber are made of the same type of rubber. Thereby, the kind of rubber forming the tread can be reduced, which is efficient.

  Further, in the tire of the present invention, as shown in FIG. 3 (C), it is preferable to reinforce by placing hard rubber 7 having a thickness of 6 mm or less on at least a part of the wall surface portion of the tread end. Here, the hard rubber 7 is a rubber whose hardness is harder than the rubber forming the tread, and more specifically, a rubber having a Shore A hardness of 60 or more and 95 or less at room temperature. By fixing the wall surface with such hard rubber, the tread can be prevented from falling when the tread is laterally deformed, and the tread end can be prevented from being lifted off the road surface. In particular, in the present invention, since soft different rubber is disposed on the surface of the tread end, it is effective to reinforce the wall surface with such hard rubber. Since the hard rubber 7 is hard, the friction coefficient is low. Therefore, when reaching the tread surface, the improvement of the frictional force due to the contact of the hard rubber 7 cannot be expected, and conversely, the contact area of the dissimilar rubber 26 is reduced. Therefore, as shown in the figure, it is more preferable to reinforce only the portion that does not contact the surface of the wall surface at the tread end. Further, since the hard rubber 7 is exposed when it is worn, the hard rubber 7 is preferably thin. Depending on the hardness of the rubber, the hard rubber 7 is effective if it has a thickness of 1 mm. More preferably, the thickness is 2 mm or more and 5 mm or less.

  In the present invention, the tread portion can be formed by a technique in which a narrow and long rubber strip is spirally stacked in the tire circumferential direction and wound. In the present invention, the tire shoulder portion where the rubber is changed is a position where the roundness is large in the tire cross section, and if the operator manually places a wide tread member as in the conventional manufacturing method, the molding accuracy (shape accuracy) Is difficult to secure. Therefore, it is possible to manufacture a tire with high shape accuracy by using a method of automatically winding a narrow unvulcanized rubber continuous body using a dedicated molding machine. If this method is applied to at least a part of the tread portion, an effect of improving the shape accuracy can be obtained, and may be applied to the whole. This technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-240098.

  In the present invention, the spiral belt 4 is preferably used as the belt 3. A spiral belt is a belt that includes a cord having an angle of 0 to 5 degrees with respect to the tire circumferential direction, and a continuous body in which one or two or more cords are coated with unvulcanized rubber, It can be formed by continuously spirally winding the tread portion along the tire circumferential direction. Since such a spiral belt has a cord extending in the tire circumferential direction, disposing the spiral belt makes it difficult for the tire 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. On the other hand, such a circumferential member is effective for steering stability performance at high speeds, 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 reduced. The side grip is not much different from the conventional tire without spiral belt. Therefore, it is preferable to apply the present invention to such a high-performance tire because the lateral grip at the time of large CA is increased and the performance balance as a high-performance tire is improved.

  Spiral belts may be formed of steel cords in addition to organic fiber cords such as aromatic polyamides. For example, 30 cords of steel cords in which a steel single wire having a diameter of 0.21 mm is twisted in a 1 × 3 type are used. For example, it can be formed by spirally winding at 50 mm.

  In the example shown in FIG. 1, as the belt 3, together with the spiral belt 4, two crossing belt layers 5 that cross each other are provided on the outer side in the tire radial direction. In the present invention, as shown in FIG. The belt layer 8 having an angle with respect to the tire circumferential direction of 80 degrees or more and 90 degrees or less is preferably disposed outside the spiral belt 4 in the tire radial direction. The belt layer 8 in the width direction can be formed using an organic fiber cord such as aromatic polyamide.

  In a tire using a spiral belt, the spiral belt is difficult to extend in the circumferential direction, and prevents the tire from being centrifugally expanded. If only a spiral belt is used, the belt rigidity can be kept relatively high, so there are some tires in which the belt portion is composed of only the spiral belt. In addition, when a spiral belt is used, the belt rigidity increases, so the belt to be fitted to the spiral belt is mostly at an angle of 45 to 80 degrees with respect to the tire circumferential direction, and the spiral belt almost receives the internal pressure of the tire. ing. Therefore, if the spiral belt is damaged, it can lead to tire burst. For example, when the tread is worn and thinned, if you step on the protrusion at high speed, or if you continue to use the tire even though it is worn, the spiral belt will be exposed. The possibility of breaking is not zero. Then, the effect which protects the spiral belt 4 can be acquired by arrange | positioning the belt layer 8 with the code | cord | chord which follows a tire width direction so that the spiral belt 4 may be covered from the outer side.

  Further, if the belt layer 8 in the width direction, which forms 80 degrees or more and 90 degrees or less in the tire circumferential direction, is widely disposed on the shoulder portion of the tire, that is, up to the position of the soft dissimilar rubber 6 disposed on the surface of the tire shoulder portion. If arranged, the reinforcing fibers in the tire width direction are present in the outermost layer of the belt, the tread base becomes stronger in the width direction, and the belt has rigidity against the transverse shear of the tread, so high lateral force Can be maintained.

  Further, when the spiral belt 4 and the belt layer 8 in the width direction are disposed, a buffer rubber layer having a thickness of 0.3 mm or more and 3 mm or less is provided at least at a part between the spiral belt 4 and the belt layer 8. Is preferably arranged (not shown). This buffer rubber layer has an effect of suppressing wear of the tread of the shoulder portion. The reason why it is preferable to provide such a buffer rubber layer is as follows.

  As shown in the behavior of the tread in the width direction when the tire of FIG. 4 turns at 50 degrees CA, the deformation in the circumferential direction of the tread is different between the region A and the region C. This is because the belt speed is different between the area C near the center of the ground contact shape and the area A near the tread edge of the ground contact shape. Since the tire for a motorcycle has a large roundness in the cross section in the width direction, the region C is larger in the region A and the region C in the belt radius, which is the distance from the rotation shaft to the belt. Therefore, the speed of the belt, that is, the belt speed until the tread moves away from the road surface after the tread contacts the road surface and the tread leaves 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 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 edge of the tire. Here, driving means that when the tire is cut along the circumferential direction, the deformation of the tread is caused by the inner surface of the tread (the surface in contact with the skeleton member inside the tire) being sheared backward in the tire traveling direction. This is a shear state in which the tread surface that is in contact with the ground is deformed forward in the tire traveling direction, which 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 tread deformation is a sheared state in which the inside of the tire (belt) is sheared forward and the tread surface that is in contact with the road surface is deformed backward, and braking is applied. Tire movement. The deformation of the circumferential tread occurs only when the tire rolls in an idle state without receiving driving force or braking force. Then, due to the shear deformation in the circumferential direction, the tread easily slips from the road surface in the region A and the region C, and wear progresses. Such excessive deformation during turning is likely to cause uneven wear on the tire shoulder, so it is preferable that there is no such deformation.

  When the cushioning rubber layer is provided, the cushioning rubber layer undergoes shear deformation in the circumferential direction, so that the above-described driving deformation and braking deformation are substituted for the tread and the circumferential deformation of the tread is alleviated. On the other hand, since the shock absorbing rubber has a belt along the tire width direction on its upper surface, it is not easily sheared and deformed in the width direction. For this reason, the transverse shear deformation of the tread remains large even when the cushioning rubber is disposed without changing the tread deformation in the width direction. In other words, the shock absorbing rubber layer shoulders deformation only in the tire circumferential direction and reduces the circumferential deformation of the tread to prevent uneven wear, while the lateral deformation of the tread remains large without replacing the shoulder in the width direction. And, there is an effect that the lateral force can be kept high. When the soft different rubber 6 is disposed on the surface of the tread end portion as in the present invention, the soft rubber is easily worn, and thus it is very preferable to provide such a buffer rubber layer. It is preferable that the belt layer and the buffer rubber layer at 80 ° to 90 ° with respect to the tire circumferential direction are particularly widely arranged so as to overlap the positions where the different types of rubber at the tread ends and the surface are arranged.

  In the tire of the present invention, only the point that the different rubber 6 is arranged at both ends in the tire width direction on the surface of the tread portion is important, whereby the desired effect of the present invention can be obtained, and the other tires The conditions such as structure and material are not particularly limited.

  As described above, in the present invention, it is preferable to dispose at least the spiral belt 4 as the belt 3, and the spiral belt may be disposed alone or in the cross belt 5 (FIG. 1) or in the width direction. You may arrange | position in combination with the belt layer 8 (FIG. 2). Further, the spiral belts may be arranged in a double manner, or only the crossing belt layer 5 may be configured without the spiral belt. Here, the crossing belt layer 5 can be provided by, for example, reinforcing cords made of aromatic polyamide or the like being crossed at ± 20 degrees to 80 degrees with respect to the tire circumferential direction. You may provide by the above, and there is no restriction | limiting in particular.

  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. The both ends of the carcass 2 may be either folded back and locked to the bead core 1 from the inside of the tire as shown in FIG. 1 or sandwiched by bead wires from both sides as shown in FIG. The fixing method may be used. 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.
(First embodiment)
In accordance with the following conditions, a pneumatic tire for a motorcycle was manufactured with a tire size of 190 / 50ZR17. Each test tire is provided with a carcass made of one carcass ply (body ply) extending across a toroid between a pair of bead cores, and the carcass ply has a diameter of 0. A 6 mm cord arranged in parallel at a driving interval of 65/50 mm and made into a sheet with unvulcanized rubber was used. Further, the carcass arrangement direction was radial (the angle with respect to the tire circumferential direction was 90 degrees). Further, the end portion of the carcass is fixed by being wound around the bead core from the tire inner side to the outer side at the bead portion.

  A spiral belt was disposed outside the carcass in the tire radial direction. The spiral belt is formed by winding a cord having a diameter of 0.7 mm twisted from an aromatic polyamide (trade name: Kevlar) fiber and winding the cord in the tire circumferential direction at a number of 50/50 mm. A belt-like body (strip) in which the cord was embedded in the covering rubber was manufactured by a method of winding the belt in the tire rotation axis direction in a spiral manner substantially along the tire circumferential direction. Further, two crossing belt layers were arranged on the outer side in the tire radial direction of the spiral belt. The crossing belt layer was arranged by crossing cords of 0.7 mm in diameter twisted with aromatic polyamide fibers at an angle of ± 50 degrees with respect to the tire circumferential direction at a driving number of 30/50 mm. A tread portion was provided outside the crossing belt layer, and the thickness of the tread portion was 7 mm, which was the same thickness from the center portion to the shoulder portion. In addition, diagonal grooves having a width of 8 mm and a depth of 5 mm are alternately arranged in a square shape on the surface of the tread portion so that the ratio of the grooves to the entire tread is 10% (FIG. 1B). )).

  Based on the above structure, the configuration of the tread portion was changed as follows, and test tires of the respective conventional examples, examples, reference examples, and comparative examples were manufactured. The developed width of the tread (the length of the arc along the roundness) is 240 mm, the width of the spiral belt is 220 mm, the width of the first (inner) crossing belt is 250 mm, and the second (outer) crossing. The belt width was 230 mm. In the following, the dynamic elastic modulus E ′ was measured at a temperature of 50 ° C., a frequency of 15 Hz, and a strain of 5% using a viscoelasticity measuring device manufactured by Rheometrics.

<Conventional example 1>
The entire region of the tread portion was made of a single type of rubber. The dynamic elastic modulus E ′ of the tread rubber of Conventional Example 1 at a temperature of 50 ° C. was 4.0 MPa. Assuming that the value of the dynamic elastic modulus E ′ is 100, hereinafter, the elastic modulus of each rubber is indicated by an index.

<Example 1>
As shown in FIG. 1, dissimilar rubber 6 was disposed at both ends of the tread surface in the tire width direction with an arrangement width (tread surface width) of 25 mm and a depth of 4 mm. The index value of the dynamic elastic modulus E ′ of this different rubber was 70. Further, the boundary in the depth direction between the dissimilar rubber and the rubber disposed adjacent to the inner side in the tire width direction was perpendicular to the depth direction and was not inclined. Further, the tread center portion is divided into two layers, and the surface layer rubber is the same as the rubber adjacent to the center of the soft different rubber 6 at the end of the tread, and the index value of the dynamic elastic modulus E ′ is 100. there were. On the other hand, as the inner layer rubber 12A, a rubber having an index value 150 of the dynamic elastic modulus E ′ is used. The arrangement width of the inner layer rubber 12A was 120 mm.

<Examples 2 to 10, Reference Example 1, Comparative Examples 1 to 4>
Using the test tire of Example 1 as a basic structure, the disposition conditions of different rubbers were changed as shown in the following table, and test tires of Examples, Reference Examples, and Comparative Examples were prepared.

<Conventional example 2>
A test tire of Conventional Example 2 was manufactured in the same manner as Conventional Example 1 except that the tread center portion was configured in two layers with the same configuration as in Example 1.

<Comparative Example 5>
Comparative Example 5 is similar to Conventional Example 2 except that the average thickness of the tread rubber in the range from the tread edge to 10% of the tread development width is 0.7 mm thinner than the other parts. A test tire was produced.

<Measurement of lateral force at 50 degrees CA>
About each produced test tire, the lateral force measurement in CA50 degree was implemented. A # 40 sandpaper was attached to a steel drum with a diameter of 3 m to make it look like a road surface. Each test tire was assembled on a wheel having a rim width of 6 inches and a rim diameter of 17 inches and filled with an internal pressure of 240 kPa. The tire was pressed against a drum at a CA of 50 degrees, a load of 1500 N, and a SA of 0 degrees, and rotated at a speed of 40 km / h. The lateral force at this time was measured from a three-component force meter attached to the rotating shaft of the tire. Lateral force is camber thrust. The lateral force was measured when the tire started rotating for 5 minutes. At this time, the tire was sufficiently warmed, and the tread temperature of the shoulder portion was about 50 ° C. The results are shown as an index with the lateral force of Conventional Example 1 being 100. The lateral force of Conventional Example 1 was 1350N.

<Rolling resistance test>
The rolling resistance test was evaluated by measuring with a rolling resistance tester at an internal pressure of 240 kPa, a load of 1500 N, a slip angle (SA) of 0 degree, a CA of 0 degree, and a speed of 80 km / h. The results are shown as an index with the rolling resistance of Conventional Example 1 as 100. The smaller the index, the lower the resistance and the more fuel efficient.

<Evaluation at the test course>
On the test course, a comprehensive ride stability test (operation test) was conducted by skilled riders. Since each test tire was a rear tire, only the rear tire was replaced and an actual vehicle test was performed. The front tire was always fixed with a conventional one. Each test tire is mounted on a 1000cc sports-type motorcycle, run on a test track, evaluated with a focus on steering stability (cornering performance) when the vehicle is greatly tilted, and 10 Overall evaluation was made by the point method. The layout of the test course was specially set up so that the corner grip performance could be confirmed especially when it was greatly defeated by providing six corners to defeat CA 50 degrees at a speed of around 50 km / h. The lap time for one lap was about 60 seconds, and this was 15 laps. The rider was given a comprehensive sensory score for 15 laps.

<Evaluation of wear amount>
Before the actual vehicle test, the tire weight was measured. Then, after 15 laps of the test course, deposits such as rubber debris and pebbles adhered to the tire were removed, the tire weight was measured, and the weight difference from the new article was evaluated as the amount of wear. Since the special test course had many corners, wear was concentrated on the shoulder. That is, this weight difference can be considered as the amount of wear of the shoulder portion from the new article. With the wear weight of the tire of Conventional Example 1 as 100, the wear amount of each test tire was compared by index.

  These results are shown in the table below.

＊１）異種ゴムのトレッド表面における配設幅（ｍｍ）、および、この配設幅のトレッド展開幅に占める比率（％）（トレッド端からの範囲）を示す。
＊２）異種ゴムの厚み（ｍｍ）、および、この厚みがトレッドゴムの総厚みに占める比率を示す。
＊３）２層の場合の幅は、常に１２０ｍｍである。

* 1) The arrangement width (mm) of the different rubber on the tread surface and the ratio (%) of the arrangement width to the tread development width (range from the tread edge) are shown.
* 2) Indicates the thickness (mm) of different rubber and the ratio of this thickness to the total thickness of the tread rubber.
* 3) The width in the case of two layers is always 120 mm.

<Effect of the width of the soft rubber on the tread edge>
By comparing the results of Conventional Example 2, Examples 1 to 3 and Comparative Examples 1 to 3, the effect of the arrangement width can be understood. Compared with the conventional example 2 (without surface rubber), those with the surface rubber of 15 mm to 45 mm have improved lateral force at the drum = camber thrust, and it can be seen that there is an effect of improving the lateral grip. . Comparative Example 1 has a width of 10 mm, but if the width is 10 mm, the surface rubber contact area is too small and there is almost no effect. In addition, when the width is 25 m or more, the rate of improvement in the lateral grip is almost constant, and it can be seen that the lateral grip can be sufficiently improved if the width is about 25 mm. Conversely, if there is a certain width, it can be seen that the effect of improving the lateral grip is diminished even if the width is further increased. This tendency also appears in the steering stability performance score on the test course. When the width exceeds 25 mm, the score is the same level with 9 points.

  On the other hand, looking at the amount of wear, there was a large difference in the amount of wear between the width of 30 mm and the width of 35 mm. Furthermore, when the width is 45 mm, the amount of wear increases drastically, but this is because the part where the soft rubber is placed extends to the part that is frequently used during traction at CA 40 degrees, and it accelerates by applying driving force from the corner where the motorcycle is greatly defeated. This is because the wear of the tire progresses when this is done, and this part is worn out.

  From the above, from the aspect of steering stability performance, the lateral grip is improved to a level that does not improve further around 25 mm to 30 mm in width, and the wear performance deteriorates sharply when the width is 35 mm or more. As for the tire of the embodiment, it can be seen that it is appropriate that the disposition width of the dissimilar rubber is about 15 mm to 30 mm. That is, 5% or more and 14% or less of the tread development width is suitable, and more preferably 10% or more and 14% or less.

<Effect of different rubber thickness on tread edge>
From the comparison of Conventional Example 2, Examples 1, 4, 5, 6 and Comparative Example 4, the effect of the thickness of the different rubber can be seen. Each of the thicknesses of 1 mm, 2 mm, 4 mm, and 5 mm had a higher lateral force index on the drum than that of Conventional Example 2, and a higher score on the test course. However, in Comparative Example 4, the lateral force index was 1% lower than that in Conventional Example 2, and the lateral force was lowered despite the soft rubber disposed at the tread end. This is because the tread rigidity at the end of the tread has decreased, and even if the friction coefficient has increased because the rubber is soft and easily bites into the road surface, the lateral shear rigidity of the tread has decreased, so the lateral force is no longer generated. . Thus, no effect was obtained even if soft rubber was placed over the entire tread thickness, and it was confirmed that it was effective to place soft rubber only on the surface of the tread edge as in each example. .

  As for the preferred value of the thickness of the different types of rubber, in the case of the present embodiment, it can be seen that 1 mm is slightly thin, and although there is an effect, the degree of improvement is small. In this embodiment, it is understood that a thickness of 2 mm to 5 mm is appropriate, and a thickness of 0.2 to 0.7 (20% to 70%) of a total thickness of 7 mm of the tread is appropriate. More preferably, it is 0.3 to 0.7 (30% to 70%).

<Effect of two-layered center part>
From the comparison between Conventional Example 1 and Conventional Example 2 and the comparison between Reference Example 1 and Example 1, the effect of making the tread center part two layers can be seen. In the present embodiment, when soft different rubber is not disposed at the tread end as in the conventional example, the lateral force index in the drum is determined depending on whether the center portion is divided into two layers or not. There was no difference. However, as in the example, when different rubber is arranged on the tire shoulder portion to form two layers and generate a large lateral force, the tread center portion has two layers to further increase the lateral force. I understand that. This is because the lateral deformation of the tire has increased due to the increased lateral force of the tire, and the rigidity of the tire center has increased by hardening the rubber inside the tread center. It is.

  Referring to FIG. 4, in the ground contact state of CA 50 degrees, the tire center portion is not in contact with the road surface and exists immediately next to the ground contact surface. At this time, the tire center portion plays the same role as the sidewall of the tire. If this portion is hardened, the lateral rigidity of the tire is increased. In the case of a two-wheeled vehicle tire, the center portion of the tire is a tread portion that comes into contact with the tire, but serves as a side portion when turning at a CA of 50 degrees. As in the example, when the soft rubber is placed on the tread shoulder and the lateral force during turning is increased, the deformation of the tire increases, so that the steering stability can be improved by reinforcing the center of the tire. improves. That is, since the tread center portion has two layers and rubber (hard rubber) having a high dynamic elastic modulus is disposed inside, the lateral grip is also improved.

  As described above, making the tread center part into two layers not only simply reduces the rolling resistance when traveling straight, but also saves fuel consumption, as shown in this embodiment, soft rubber is applied to the surface of the shoulder part. Combined with the arrangement, it was confirmed that there is an effect that the lateral grip can be further improved.

<Rubber softness effect>
By comparing the tires with different dynamic elastic moduli of different rubbers based on the structure of Example 1, the influence of the dynamic elastic modulus can be understood. From the comparison of Examples 1, 7, 8, 9 and Conventional Example 2, the effect is small when the elastic modulus index of the different rubber is 90. This is because the effect is diminished because the difference in hardness is small. Also, if the elastic modulus index of different types of rubber is 30, the effect is still small, but this is because the rubber becomes softer, the bite into the road surface is greatly increased and the friction coefficient is improved, but the rubber is too soft and the tread This is because the transverse shear rigidity of the steel sheet is reduced, and the improvement in the friction coefficient is offset.

  From the tendency in the present embodiment, preferable results are obtained when the elastic modulus index of rubber is 70 and 50. From the above, it can be determined that 40 to 80 is appropriate as the elastic modulus index. In addition, when the elastic modulus index is 30 or 50, it can be seen that the wear has deteriorated, and it can be said that the preferable value is 60 to 80 considering the wear performance.

<Effect of thinning the tread edge>
Example 10 and Comparative Example 5 are tires manufactured so that the average thickness of the tread rubber in the region from the tread end portion to 10% of the tread development width is 0.7 mm thinner than the other portions. The thickness of the other part is 7 mm and is uniform. The thickness is gradually reduced toward the end in the above range. In Example 10, the thickness of the soft rubber on the surface was maintained as it was, and the thickness of the internal rubber was gradually reduced toward the tread edge. From the comparison between Example 1 and Example 10 and the comparison between Conventional Example 2 and Comparative Example 5, the effect of thinning the tread edge can be seen.

  From a comparison between Example 1 and Example 10, in Example 10 in which the rubber at the end of the tread was thinned, the lateral force of the drum was improved, and the test stability performance test score on the test course was also high. Comparative Example 5 also has the same tendency as compared with Conventional Example 2. However, in Comparative Example 5, the amount of wear after running is large. This is because only the tread thickness is reduced without softening the rubber at the end of the tread, so the rigidity of the tread in this part is improved compared to the others, and the tread surface is slippery because the deformation of the tread is small. This is because it became easier. That is, the end tread slips and the end wear progresses. On the other hand, in Example 10 in which the tread surface was covered with soft rubber, the rubber on the surface was soft and the deformation was large. Therefore, by reducing the thickness of the tread, the balance of rigidity with other parts becomes appropriate. Therefore, compared with Example 1 before thinning, there is almost no deterioration of wear. Thus, it can be seen that by combining the control of the thickness of the tread with the structure in which the rubber on the surface is softened, the steering stability performance can be improved and the wear life can be maintained.

(Second embodiment)
In accordance with the following conditions, a pneumatic tire for a motorcycle was manufactured with a tire size of 190 / 50ZR17. Each test tire has a carcass composed of two carcass plies (body plies) extending in a toroidal shape between a pair of bead cores. As the carcass plies, Kevlar (aromatic polyamide) fibers are used. The twisted cords having a diameter of 0.6 mm were arranged so that the driving at the tire center portion was 40 pieces / 50 mm. Further, the two carcass plies crossed each other, and the angle at the tire center portion was ± 40 degrees with respect to the tire circumferential direction. The end portion of the carcass reaches the bead portion. In the bead portion, two pieces are bundled together and fixed by being sandwiched by bead wires from both sides.

  Further, a spiral belt was disposed on the outer side in the tire radial direction of the carcass in the tread portion. The spiral belt was formed by twisting seven steel wires having a diameter of 0.12 mm to form one steel cord, and spirally winding the tread on the tread so that the driving interval was 50/50 mm. Further, one belt layer having an angle of 90 degrees with respect to the tire circumferential direction was disposed outside the spiral belt in the tire radial direction. This 90-degree belt layer was formed by arranging cords of 0.6 mm in diameter twisted with aromatic polyamide fibers at a driving interval of 50/50 mm. A tread portion was provided outside the 90-degree belt layer, and the thickness of the tread portion was uniformly 8 mm from the center portion to the shoulder portion.

  The developed width of the tread (the length of the arc designed along the roundness) was 240 mm, the width of the spiral belt was 240 mm, and the width of the 90-degree belt on the radially outer side was also 240 mm. The tread center portion is divided into two layers. As the inner layer rubber 12A, a rubber having a Shore A hardness of 120 ° C. and a very low loss tangent tan δ is disposed with a width of 120 mm and a thickness of 4 mm. On the other hand, as the surface rubber 12B, a rubber having a Shore A hardness of 45 at 120 ° C. and a width of 90 mm was disposed.

  Based on the above structure, the configuration of the tread portion was changed as follows, and test tires of the respective conventional examples, examples, and comparative examples were manufactured. In any case, since the tire center portion has a two-layer structure, the structure of the center portion is not mentioned in the table.

<Conventional Example 3, Comparative Examples 6 and 7>
A rubber 12C having a Shore A hardness of 35 at 120 ° C. was disposed on both sides of the tread center portion, and a different kind of rubber was not disposed on the surface. This corresponds to the case where the rubber at the tread end in FIG. 2 is removed and replaced with a rubber having a Shore A hardness of 35. Each test tire was manufactured by changing the conditions for the hard rubber on the wall surface at the tread edge and the buffer rubber layer between the spiral belt and the 90-degree belt layer. As hard rubber, one having a Shore A hardness of 70 ° C. at 120 ° C. is used, and as shown in FIG. It was arranged to be 4 mm. Further, the hard rubber was not exposed on the surface, and the height was arranged from a position of 1 mm to a position of 8 mm from the surface. Furthermore, the rubber type of the buffer rubber was the same type as the belt coating rubber covering the 90 degree belt.

<Examples 11 to 14, Comparative Example 8>
As shown in FIG. 2, dissimilar rubber 6 having a Shore A hardness of 27 at 120 ° C. was disposed at both ends of the tread surface in the tire width direction according to the conditions shown in the following table. Each test tire was manufactured by changing the conditions for the hard rubber on the wall surface at the tread edge and the buffer rubber layer between the spiral belt and the 90-degree belt layer.

  The following evaluations were made for each test tire. Prepare three tires, one for lateral force evaluation when new, the other for lateral force evaluation assuming wear by scraping the tread surface, and the other for actual vehicle testing. It was. The tire of the second embodiment was evaluated assuming that it is used in competition.

<CA50 degree lateral force measurement (when new)>
A # 40 sandpaper was attached to a steel drum with a diameter of 3 m to make it look like a road surface. Each test tire was assembled on a wheel having a rim width of 6 inches and a rim diameter of 17 inches and filled with an internal pressure of 200 kPa. The tire was pressed against a drum at a CA of 50 degrees, a load of 1500 N, and a SA of 0 degrees, and rotated at a speed of 100 km / h. The lateral force at this time was measured from a three-component force meter attached to the rotation shaft of the tire. Lateral force is camber thrust. The lateral force was measured when the tire started rotating for 5 minutes. At this time, the tread temperature of the shoulder portion was sufficiently warmed to be about 120 ° C. The results are shown as an index with the lateral force of Conventional Example 3 as 100. The lateral force of Conventional Example 3 was 1900N.

<Evaluation of lateral force of tires assuming wear>
Next, the tire surface of each test tire was uniformly cut by 3 mm from the center portion to the shoulder portion. The tire was subjected to the same test as described above, and the tire lateral force after 5 minutes from the rotation was measured.

<Evaluation at the test course>
On the test course, a comprehensive ride stability test was conducted by skilled riders. Since each test tire was a rear tire, only the rear tire was replaced and an actual vehicle test was performed. The front tire was always fixed with a conventional one. Each test tire was modified on a 1000cc sports-type motorcycle and used on a motorcycle for competition. The maximum speed reached 320 km / h. The results were comprehensively evaluated by a 10-point method based on the feeling of the test rider. The test was performed for 20 laps, and the average lap time for the first 10 laps and the average lap time for the last 10 laps were obtained. As for lap time, the lap time when the rider made a mistake was excluded from the average calculation. The feeling score of the steering stability performance was also evaluated separately for the first 10 laps and the second 10 laps. The layout of the circuit was four corners where the car body was greatly collapsed at a speed of 80 km / h to 120 km / h. Moreover, the tire temperature immediately after running 20 laps was about 120 degreeC.

<Evaluation of wear amount>
Before the actual vehicle test, the tire weight was measured. Then, after making 20 laps on the test course, the rubber debris and pebbles adhering to the tire were removed, the tire weight was measured, and the weight difference from the new article was evaluated as the amount of wear. Since the special test course had many corners, wear was concentrated on the shoulder. That is, this weight difference can be considered as the amount of wear of the shoulder portion from the new article. With the wear weight of the tire of Conventional Example 3 as 100, the wear amount of each test tire was compared by index. In Conventional Example 3, the amount of wear at the shoulder when the circuit was turned 20 times reached 4 mm.

  These results are shown in the table below.

＊１）異種ゴムのトレッド表面における配設幅（ｍｍ）、および、この配設幅のトレッド展開幅に占める比率（％）（トレッド端からの範囲）を示す。
＊２）異種ゴムの厚み（ｍｍ）、および、この厚みがトレッドゴムの総厚みに占める比率を示す。
＊４）異種ゴムと、そのタイヤ幅方向内側に隣接して配置されたゴムとの深さ方向の境界の形状を示す。
＊５）トレッド端の壁面部における硬質ゴムの有無を示す。
＊６）スパイラルベルトと９０度ベルト層との間における緩衝ゴム層の有無を示す。

* 1) The arrangement width (mm) of the different rubber on the tread surface and the ratio (%) of the arrangement width to the tread development width (range from the tread edge) are shown.
* 2) Indicates the thickness (mm) of different rubber and the ratio of this thickness to the total thickness of the tread rubber.
* 4) Denotes the shape of the boundary in the depth direction between different types of rubber and the rubber disposed adjacent to the inside in the tire width direction.
* 5) Indicates the presence or absence of hard rubber on the wall surface at the tread edge.
* 6) Indicates the presence or absence of a buffer rubber layer between the spiral belt and the 90-degree belt layer.

<Effects of arranging different types of rubber>
By comparing Conventional Example 3, Example 11 and Comparative Example 8, the effect of dissimilar rubber arrangement can be seen. In Example 11, compared with Conventional Example 3, the lateral force index when new and when the 3 mm tread was shaved was improved. In addition, the lap time when running on the circuit is also faster than 1 second, so the effect is clear. Further, the amount of wear is improved in Example 11 compared to Conventional Example 3. This is because in such a tire for competition, the engine power is strengthened and high, so the driving force during acceleration when escaping from the corner is very strong, and the tire accelerates while sliding. When the grip force of the tire is increased, slipping of the tire is suppressed and the amount of wear can be reduced. As in Example 11, when the lateral grip force is increased, the tire firmly grips in the lateral direction at the time of acceleration, so that it is possible to suppress unnecessary idle rotation of the tire and despite using soft rubber at the tread end, The wear was improved.

  In Comparative Example 8, soft rubber is arranged over the entire thickness of the tread. In this tire, the tread lateral shear rigidity at the tread edge is too low, and the soft rubber is used on the tread surface. As a result, the merit of the higher friction coefficient was offset, and as a result, the lateral force index did not change. Therefore, the lateral force was not different from the conventional example. Even when the circuit was running, because the grip force was insufficient, the tire was liable to slip, the tire slipped, and the amount of wear on the tire was large. Since soft rubber was used, the amount of wear increased compared to the tire of Conventional Example 3.

  From the above results, it can be seen that it is preferable to soften only the surface of the tire instead of making the entire thickness of the end portion of the tread soft rubber.

<Effect of expanding the width of different types of rubber in the depth direction>
From a comparison between Example 11 and Example 12, the effect of disposing different types of rubber on the surface of the tread edge so as to widen the arrangement width in the depth direction can be seen. It is a comparison between (A) and (B) of FIG. In Example 12, the lateral force index of the tire when new was also increased by 1 point. This is because the soft rubber exists diagonally inside, and even if there is a hard rubber on the surface, the soft rubber is inside, so that the hard rubber tends to bite into the road surface and the friction coefficient increases. Moreover, in the drum evaluation with the tire scraped off by 3 mm assuming wear, the amount of decrease in the lateral force from when it was new is suppressed. This is because the amount of exposed soft rubber increases with tire wear. Even in running on the test course, Example 12 has a higher score in the latter half of the running than in Example 11.

<Effects of hard rubber>
From the comparison between Examples 12 and 13, the effect of arranging hard rubber can be seen. The hard rubber has a Shore A hardness of 120 ° C. of 70, which is harder than any rubber constituting the tread rubber. By arranging hard rubber as in Example 13, it is possible to prevent soft rubber from being placed on the surface and prevent the lateral rigidity of the tread from being lowered. Both improved. In addition, although the case where a hard rubber was applied with respect to the tread rubber structure of the prior art example 3 was made into the comparative example 6, in this case, compared with Example 13 which applied the hard rubber to Example 12, the improvement effect of lateral force Less is. This is because the conventional example 3 uses a hard rubber at the end portion of the tread, so that the lateral shear rigidity of the tread can be maintained to some extent without being reinforced with the hard rubber. As in this embodiment, when soft rubber is used for the tread edge, the effect of hard rubber is very effective.

<Effects of cushion rubber>
From comparison between Example 13 and Example 14, the effect of the arrangement of the buffer rubber layer can be seen. In Example 14, a buffer rubber layer is disposed between the 90-degree belt and the spiral belt. As described above, by arranging the buffer rubber, the skeleton member can move flexibly in the circumferential direction while enhancing the shear rigidity in the width direction of the skeleton member, and the unnecessary shearing in the circumferential direction of the tread can be reduced. . Therefore, slipping of the tire is suppressed, wear is reduced, and grip is improved. Example 14 shows the highest score and the fastest lap time in this test. Furthermore, it is an advantage that the amount of wear is extremely small. This is due to the fact that as the tires for competition increase in grip, slipping decreases and wear increases.

  In addition, although the thing which has arrange | positioned hard rubber and buffer rubber to the prior art example 3 is the comparative example 7, the effect of Example 14 is large compared with these cases. This is because the soft rubber on the surface of the end portion of the tread according to the present invention, the buffer rubber and the hard rubber synergistically improved the effect.

1 is a cross-sectional view in a width direction showing a pneumatic tire for a motorcycle according to a preferred example of the present invention. It is a width direction sectional view showing a pneumatic tire for two-wheeled vehicles concerning other suitable examples of the present invention. It is an expanded partial sectional view which shows the arrangement | positioning site | part of dissimilar rubber. It is sectional drawing which shows the tire just under a load when a two-wheeled vehicle is turning by big CA (CA50 degree | times).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 3 Belt 4 Spiral belt 5 Crossing belt layer 6 Different rubber 7 Hard rubber 8 Belt layer 11 of width direction Bead part 12 Tread part 12A Surface rubber 12B Inner layer rubber 12C Rubber 13 outside tread center part Side wall part

Claims (9)

In a pneumatic tire for a motorcycle including a tread portion formed in an annular shape,
Dissimilar rubber is disposed on both ends of the tread surface in the tire width direction, the disposition width of the dissimilar rubber on the tread surface is within a range of 5% to 14% of the tread development width from the tread end, and Shore a hardness of dissimilar rubber, rather smaller than the Shore a hardness of the rubber disposed adjacent in the tire width direction inner side of said heterologous rubber,
Of the tread portion, at least 15% of the tread development width centered on the tire equator plane is made of two types of rubber laminated in the thickness direction, and the portion made of the two types of rubber and the different type The tread between the two ends where the rubber is placed is formed in one layer,
A pneumatic tire for a two-wheeled vehicle, characterized in that a surface layer rubber of the two kinds of laminated rubber and a rubber adjacent to the dissimilar rubber are made of the same kind of rubber .   The pneumatic tire for a motorcycle according to claim 1, wherein the disposition width of the different rubber increases from the tread surface toward the inside in the tire radial direction.   The pneumatic tire for a motorcycle according to claim 1 or 2, wherein a thickness of the different rubber is 20% or more and 70% or less of a total thickness of the tread rubber.   The average thickness of the tread rubber in the range from the tread end to 10% of the tread development width is smaller than the average thickness of the tread rubber in the range from 10% to 25% of the tread development width based on the tread end. The pneumatic tire for a motorcycle according to any one of Items 1 to 3.   The pneumatic tire for a motorcycle according to any one of claims 1 to 4, wherein a hard rubber having a thickness of 6 mm or less is disposed on at least a part of a wall surface portion at a tread end.   The pneumatic tire for a motorcycle according to any one of claims 1 to 5, wherein at least a part of the tread portion is formed by winding a narrow and long rubber strip spirally in the tire circumferential direction. .   The pneumatic tire for a motorcycle according to any one of claims 1 to 6, further comprising a spiral belt having an angle with respect to a tire circumferential direction of 0 to 5 degrees inside a crown tire radial direction of the tread portion.   The pneumatic tire for a motorcycle according to claim 7, further comprising a belt layer having an angle with respect to a tire circumferential direction of not less than 80 degrees and not more than 90 degrees between the tread portion and the spiral belt.   The pneumatic tire for a motorcycle according to claim 8, further comprising a buffer rubber layer having a thickness of 0.3 mm or more and 3 mm or less at least partly between the spiral belt and the belt layer.

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