JP2009120002A - Pneumatic tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for a motorcycle capable of improving traction performance especially during tight cornering wherein a vehicle is largely tiled, without impairing other performance. <P>SOLUTION: The pneumatic tire for a motorcycle is equipped with an annularly formed tread part 11. A spiral belt layer 3 wherein an angle with respect to a tire circumference direction is 0-5 degrees and an arrangement width is 0.5-0.8 times of a tread width is equipped in a crown part tire radial inner side of the tread part 11. The numbers of implanted cords forming the spiral belt layer 3 are different in a tire center part and a tire shoulder part, and a mean number of implanted cords of areas respectively of a width of 25% from both ends of the spiral belt layer 3 is smaller than a mean number of implanted cords of an area of a width of 50% of a center of the spiral belt layer 3, and the mean number of implanted cords of the both end areas is ≥0.2 and ≤0.8 of the mean number of implanted cords of the center area. <P>COPYRIGHT: (C)2009,JPO&INPIT

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 of a spiral belt layer.

  In high-performance two-wheeled vehicle tires, the rotational speed of the tires is high, and therefore the influence of centrifugal force is large, and the tread portion of the tires expands outward, which may impair steering stability performance. For this reason, a tire structure having a so-called spiral belt layer in which a reinforcing member (spiral member) made of organic fiber or steel is wound around the tread portion of the tire so as to be substantially parallel to the tire equatorial plane has been developed.

  As a spiral member used for this spiral belt layer, for example, nylon fiber, aromatic polyamide (Kevlar), steel or the like is used. Among them, aromatic polyamides and steels have recently been attracting attention because they can suppress expansion of the tread portion without stretching even at high temperatures. By wrapping such a spiral member around the crown of the tire, the so-called “tangle” effect (the tire is pressed by the centrifugal force even when the tire is pressed at a high speed by pressing the crown of the tire like a bath tub). Since it is possible to increase the effect of preventing the swelling and exhibiting high steering stability performance and durability, many techniques related to the improvement of these spiral members have been proposed so far (for example, Patent Document 1). ~ 5 etc.).

  It is known that a tire around which these spiral members are wound is excellent in handling stability performance at high speed and has very high traction. However, with regard to the turning performance when the vehicle (motorcycle) is largely defeated, just because the spiral member is wound, the steering stability performance does not improve dramatically. Consumers and riders who are racing may be asked to improve grip when a bike is knocked down.

Further, it is known that the durability performance at high speed is particularly improved by the elastic modulus of the spiral member (in addition, the elastic modulus per unit width of the spiral member can be controlled by the number of driving). Generally, when a member having a high elastic modulus is used for a spiral belt, centrifugal expansion of a tread portion of a tire can be suppressed, and durability performance at high speed is improved. In the case of a motorcycle tire, since the central region of the tread used at high speed receives a large centrifugal force, it is effective to use a spiral member having a high elastic modulus in order to prevent centrifugal expansion. On the other hand, the tread end regions that contact the ground when the bike is greatly defeated are not used as fast as the central part, so use a spiral belt with a lower elastic modulus than the central part and place importance on grounding stability. There is also. As described above, in the tire for a motorcycle, since the required performance is different between the center region and the end region of the tread, a patent has been filed in which the driving of the spiral member is changed at an arrangement position (for example, Patent Documents 6 and 7). ).
JP 2004-067059 A JP 2004-067058 A JP 2003-011614 A JP 2002-316512 A JP 09-226319 A Japanese Patent Laid-Open No. 50-121903 Japanese Patent Laid-Open No. 10-86608

  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 ground is different between when going straight and when turning. That is, there is a feature that the center portion of the tread portion is used when going straight and the end portion of the tread portion is used when turning. Therefore, the shape of the tire is very round compared to the tire for passenger cars. This round crown shape (the shape of the tread portion of the tire is called a crown shape) has the following unique characteristics especially during turning.

  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 a large tilt, the grounding state as shown in FIG. 6 is obtained. Considering the ground contact shape at this time, as shown in the drawing, the deformation state of the tread differs between the ground shape near the center and the ground shape near the tread end. Looking at the deformation of the tread in the tire rotation direction (also referred to as the tire circumferential direction or the tire longitudinal direction), the driving state is near the tire center, and the braking state is near the tire tread edge.

  Here, the driving state means that when the wheel is cut along the tire equator direction, the deformation of the tread is caused by the lower surface of the tread (the surface in contact with the skeleton member inside the tire) being sheared rearward in the tire traveling direction. This is a shearing 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, the braking state is the reverse of the driving state, and the deformation of the tread is a sheared 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. 6, when turning with a large camber angle (CA) such as 45 degrees, the ground contact area near the tread center even when the tire is rotated with no driving force or braking force applied. The driving state appears at the front and the braking state appears near the tread edge. 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. 6, the radius R1 near the center of the ground contact shape is clearly larger than the radius R2 near the tread edge of the ground 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 the rotation of the tire 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 speed of the belt is fast becomes shearing deformation in the driving state, and at the end of the tread of the tire, the speed of the belt is slow, so that braking deformation occurs. This is a modification of the tread in the front-rear direction.

  Due to such extra deformation during turning, the tread causes reverse shear deformation in the forward and backward directions, which includes useless behavior and wasteful tire grip force during turning. Ideally, if all the deformations of the tread that are in contact with the ground are the same, the gripping force will be maximum, but the excessive deformation as described above will occur, and depending on the grounding location, the gripping force may be It may not occur. For example, when considering acceleration when the tire is tilted, the driving force is applied to the tire, but the tread near the center already in the driving state exhibits the driving grip as soon as the driving force is applied to the tire. On the other hand, the tread at the tread end already in the braking state cannot easily contribute to the driving force because the braking deformation once returns to neutral and then shifts to the deformation on the driving side. A large traction force is required to bring the tread end into the driving state. When the accelerator is opened and a driving force is applied to the tire to apply such a traction force, the tire center side in the driving state is originally The tread slides easily and falls into an idle state.

  Accordingly, an object of the present invention is to eliminate the above-mentioned problems unique to motorcycles, and to improve the traction performance during deep cornering, especially when the vehicle is greatly defeated, without impairing other performances. To provide tires.

As a result of intensive studies to solve the above problems, the present inventors have found the following.
In other words, if the tread deformation of the tire shoulder part (tread end part) originally on the braking side is set to the driving side as much as possible, the traction force can be exerted greatly at the tread end part. Conceivable. One solution is to increase the belt speed at the tread edge. However, the belt speed is determined by the belt radius as described above, and if the belt radius is increased, the belt cannot be used as a tire for a motorcycle. Therefore, it is conceivable to increase the belt speed by making the belt easily extend in the equator direction at the end of the tread after being grounded. In other words, when turning at a large CA, if the center half of the grounding shape has a structure in which the belt does not extend in the equator direction, and if the belt is extended in the equator direction for the half on the tread end side, then the tread after grounding. By extending the belt on the side, the belt speed on the tread end side is increased, and braking deformation on the tread end side can be reduced. As a result, the traction (acceleration from a turn with a large tilt of the motorcycle) at the time of large CA is improved.

  In conventional motorcycle tires, the spiral belt layer is usually wound around the entire tread region. With such a tire, the belt of the shoulder portion of the tread cannot be extended in the equator direction. Therefore, if the spiral belt layer is disposed only on the center side without being wound around the tread edge, the belt speed at the tread edge increases at the time of large CA, that is, at the time of turning with a large camber angle. The traction grip can be improved. In addition, when the belt speed of the tread shoulder portion increases at the time of large CA, it means that the belt speed of the tread shoulder portion approaches the belt speed on the tread center side, and this causes an extra movement of the tread that is grounded. It is suppressed. In other words, the tread that has been sheared in the reverse direction so far has the shear in the same direction, so that useless movement is eliminated and the occurrence of uneven wear can be suppressed. In addition, since the spiral belt layer is arranged in the tread center part, it is possible to suppress the expansion due to the centrifugal force of the tire during high-speed driving (high speed = the motorcycle is upright). Steering stability at the time can be maintained as high as a tire with a full width spiral belt layer.

  From the above viewpoint, as a result of further studies, the inventors have determined that the spiral belt layer is not disposed on the shoulder portion, and the number of cords forming the spiral belt layer is set to the tire center portion and the tire shoulder portion. In other words, the inventors have found that the above problem can be solved by defining the ratio within a specific range, and have completed the present invention.

That is, the present invention is a pneumatic tire for a motorcycle including a tread portion formed in an annular shape,
A spiral belt layer having an angle with respect to the tire circumferential direction of 0 to 5 degrees and an arrangement width of 0.5 to 0.8 times the tread width is provided on the inner side in the tire radial direction of the tread portion. The number of cords forming the spiral belt layer is different between the tire center portion and the tire shoulder portion, and the average number of cords driven in a region having a width of 25% from both ends of the spiral belt layer is the spiral belt layer. Less than the average number of codes in the center 50% width area, and the average number of codes in the both end areas is not less than 0.2 times and not more than 0.8 times the average number of codes in the center area. It is characterized by this.

  In the tire according to the present invention, adjacent to the spiral belt layer, there is a belt intersection layer made of organic fibers that is wider than the spiral belt layer and has an angle of 30 degrees or more and less than 85 degrees with respect to the tire circumferential direction. It is preferable that it is disposed. In the present invention, between the tread layer and the spiral belt layer, adjacent to the tread layer, a belt reinforcing layer made of an organic fiber cord having an angle with respect to the tire circumferential direction of 85 degrees to 90 degrees, It is also preferable that the tread width is 90% or more and 110% or less of the tread width. It is also preferable that a rubber layer is disposed.

  According to the present invention, the above-described configuration enhances the steering stability performance at high speed, and in particular, the traction performance when accelerating from the deep cornering that greatly depresses the vehicle (bike) and the stability when the vehicle body is collapsed. It has become possible to realize a high-performance pneumatic tire for motorcycles that can improve both. Moreover, according to this invention, the effect which improves the abrasion resistance performance of a tire shoulder part can also be acquired.

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, the pneumatic tire for a motorcycle of the present invention includes a tread portion 11 formed in an annular shape, a pair of sidewall portions 12 disposed on the inner side in the tire radial direction from both sides thereof, and the sidewall portions 12. At least one piece extending between a pair of bead cores (made up of bead wires 1 in the illustrated example) embedded in the bead parts 13 respectively. In the illustrated example, two carcass 2 are provided.

  In the tire of the present invention, as shown in the drawing, the angle with respect to the tire circumferential direction is 0 to 5 degrees inside the crown portion tire radial direction of the tread portion 11, and the arrangement width is 0.5 to 0.5 of the tread width. A spiral belt layer 3 that is 0.8 times is disposed. Here, the full width of the tread is the distance of the curved surface from the tread end on one side to the tread end on the opposite side along the surface of the tire. The grounds for setting the width are based on the ground contact portion in the vicinity of 50 degrees CA where the motorcycle falls most and the ground contact portion at the position where the motorcycle is slightly raised.

  When turning at a CA of 50 degrees, only the tread shoulder portion having a width 0.2 to 0.25 times the entire width of the tread is grounded (see FIG. 6). This is about 1/4 of the total width. As described above, a spiral belt is wound around the tread center portion at the time of large CA to prevent the skeleton member from extending in the circumferential direction in the ground contact range, and conversely, the spiral belt is not wound around the tread end portion side. I want to actively extend the frame member in the circumferential direction. Half of the grounding part at the time of large CA is 0.1 times the width of the tread, and when the spiral belt is not wound around this width, there is no spiral belt at the 0.1 times wide part on both sides. The total width is 0.8 times the tread width. This is the basis for the upper limit.

  The above upper limit is an ideal value for ground contact when the motorcycle is most collapsed. However, when the motorcycle accelerates, it has the feature that it starts accelerating from the time it falls most and gradually raises the vehicle body, that is, the ground contact portion of the tire gradually moves closer to the center. Further, the motorcycle accelerates most in the range of CA 30 to 45 degrees than in the case of CA 50 degrees when the motorcycle fell most. In consideration of maximizing the traction performance at this time, it is better that the spiral width is narrower than the above 0.8 times width. Therefore, 0.5 times is set as the lower limit of the spiral width. When the spiral width is 0.5 times the tread width, the spiral end is located at the center in the width direction of the ground contact portion at CA 30 to 40 degrees. If the spiral width is less than 0.5 times, the position is shifted from the center in the width direction of the ground contact shape of CA 30 to 40 degrees, which is not preferable. That is, the spiral width is too narrow.

  In summary, it can be said that there are the following features. That is, when the spiral belt layer 3 is disposed at a width 0.8 times the upper limit of the tread width, the end of the spiral label can be positioned at the center of the ground contact shape near the CA of 50 degrees at which the motorcycle falls most. The grip improvement effect becomes high in the initial stage. In addition, the effect is high at a low-speed corner where a motorcycle is greatly defeated (it is possible to greatly defeat a motorcycle at a low-speed corner). On the other hand, when the arrangement width of the spiral belt layer 3 is 0.5 times the tread width which is the lower limit, the spiral end portion can be arranged at the center of the ground contact shape when the bike is slightly raised (CA30-40). Degree), the grip improvement effect can be demonstrated in the middle of acceleration when the car body is slightly raised from the start of acceleration. In addition, it demonstrates the effect of increasing the grip at high-speed corners that do not overwhelm the bike.

  Further, in the present invention, the number of cords forming the spiral belt layer is changed between the tire center portion and the tire shoulder portion so that the cord is dense at the tire center portion and sparse at the tire shoulder portion. When the arrangement width of the spiral belt is narrowed as in the present invention, compared to the case where the spiral belt is at the full width of the tread, when the vehicle body is tilted, there is no sudden spiral belt in the tread shoulder portion (belt shearing). (The rigidity will be lowered). Therefore, here, a sudden grip change occurs when the vehicle body is brought down, and there arises a problem that the rider feels a step difference of the tire and cannot bring down the vehicle body. In the present invention, in order to relieve this steep rigidity step, the tire shoulder portion of the spiral belt layer is sparsely driven to have a low elasticity characteristic. As a result, the change in grip becomes gentle, so that the rider can bring down the vehicle body without feeling uncomfortable. Further, since the shearing strain applied to the end portion of the spiral belt can be reduced by relaxing the rigidity step, it is possible to prevent a crack failure that is likely to occur at the end portion.

  From the above, in the present invention, in the spiral belt layer, the number of driving of the tire shoulder portion is made dense to increase the shear rigidity of the belt in the ground contact region at the time of large CA. More specifically, the average driving number of cords in the 25% width region from both ends of the spiral belt layer is smaller than the average driving number of cords in the 50% width region in the center of the spiral belt layer. To do.

  The ratio of the average number of shots in the both end regions and the central region of the spiral belt layer is set so that the average number of shots in the both end regions satisfies 0.2 to 0.8 times the average number of shots in the central region. . The reason why the lower limit is set to 0.2 times is that when the lower limit is less than 0.2 times, the cords are driven too sparsely to withstand centrifugal force, and a cord breakage failure occurs. On the other hand, the reason why the upper limit is set to 0.8 times or more is that if it is 0.8 times or more, the difference in rigidity control due to driving is too small to exhibit the effect of relaxing the rigidity step. The difference in the average number of cords to be driven is preferably 0.25 to 0.6 times in order to maximize the effect of reducing the rigidity step.

  In the present invention, the conditions relating to the number of implantations are defined by the average number of implantations at both ends of the spiral belt layer at 25% width and the average number of implantations at the center region of 50% width. . Here, the average number of implantations means the average value of the number of implantations in each region, and the number of implantations does not have to be constant in each region. Therefore, for example, the number of drivings may be gradually reduced from the center part to the shoulder part. In addition, the number of shots in an actual tire can be obtained, for example, by measuring with a cut surface obtained by cutting the tire in the width direction.

  In the present invention, the spiral belt layer is not particularly limited as long as the cord material satisfies the above conditions with respect to the average number of driving of the cords, and even if an organic fiber cord is used, a steel cord is used. Also good. Specifically, for example, twisted cords such as aromatic polyamide (trade name: Kevlar), nylon, and aromatic polyketone can be used as the organic fiber cord. In the case of a steel cord, for example, five steel single wires having a wire diameter of 0.2 mm or five steel single wires having a wire diameter of 0.4 mm can be used without being twisted.

  Organic fiber cords are easier to bend than steel cords, and can be deformed flexibly against bending out of the ground plane. For this reason, for example, when driving on rough paved roads, or when driving on joints of expressways, sudden push-ups and large vibrations do not occur, and the ride feels soft. On the other hand, in the case of the organic fiber cord, it is difficult to have rigidity in the compression direction of the cord, the shear rigidity of the belt is lowered, and it is necessary to drive a large amount in order to increase the steering stability performance. On the other hand, the steel belt is resistant to compression, and even with a small amount of driving, the shear rigidity of the belt can be increased to improve the steering stability performance.

  FIG. 2 shows a pneumatic tire for a motorcycle according to another preferred embodiment of the present invention. In the present invention, as shown in the figure, the belt crossing layer 4 that is adjacent to the spiral belt layer 3 and wider than the spiral belt layer 3 and has an angle with respect to the tire circumferential direction of 30 degrees or more and less than 85 degrees. It is preferable to arrange. This is because if the belt crossing layer does not exist here on the left and right shoulder parts where the spiral belt is not wound, the shear rigidity of the belt will be reduced, and the grip force during turning will be reduced due to the belt being too weak. Because.

  The reason why the angle of the belt crossing layer 4 disposed in the tread shoulder portion is 30 degrees or more and less than 85 degrees is as follows. When the angle with respect to the equator direction is less than 30 degrees, that is, the direction approaches the spiral belt layer, and the belt has a characteristic that it is difficult to extend in the tire circumferential direction (equator direction). This is contrary to the spirit of the present invention in which the shoulder belt extends in the equator direction in the ground contact area. When the belt is less than 30 degrees, the skeleton member is less likely to extend in the equator direction at the shoulder portion, the belt speed of the shoulder portion does not increase, and the tread of the shoulder portion remains in a braking deformation, making it difficult to obtain a traction grip. On the other hand, when the shoulder belt exceeds 85 degrees, the crossing effect sufficient for the belt crossing layer (the effect of increasing the shear rigidity of the belt by overlapping the belts in opposite directions) cannot be obtained, The belt does not have sufficient rigidity to obtain a sufficient turning grip. The angle is preferably 45 degrees or more because the skeletal member tends to extend in the equator direction. Moreover, 80 degrees or less is good also when exhibiting shear rigidity. Therefore, it is preferably 45 degrees or more and 80 degrees or less.

  An organic fiber cord is used as the material of the belt crossing layer 4. This is because if a cord having rigidity in the compression direction of the cord, such as a steel cord, is arranged as a belt crossing layer, the skeleton member has a characteristic that it is difficult to bend out of the plane, the ground contact area is reduced, and the gripping force is reduced. If it is an organic fiber cord, it does not have a great rigidity for compression in the cord direction, it can reduce the out-of-plane rigidity of the skeleton member and increase the ground contact area, and it is very strong in the tension direction of the cord This is because the rigidity can be effectively increased due to the rigidity. In the present invention, as described above, a steel cord may be used for the spiral belt. This is because spiral belts are not interlaced, and even if steel is used, there is no fear of increasing the out-of-plane bending rigidity of the belt more than necessary. If two or more steel belts are used in an interlaced manner, it is difficult to deform and the ground contact area is reduced. As the organic fiber cord used for the belt crossing layer 4, the same organic fiber cord as that used for the spiral belt layer 3 can be used.

  In the present invention, the belt crossing layer 4 may be disposed on the outer side in the tire radial direction of the spiral belt layer 3 as shown in FIG. 2, or may be disposed on the inner side in the tire radial direction of the spiral belt layer ( As long as it is disposed adjacent to the spiral belt layer 3, there is no particular limitation on the arrangement order.

  In the present invention, as shown in FIG. 1, an organic fiber having an angle of 85 degrees to 90 degrees with respect to the tire circumferential direction is adjacent to the tread layer 11 between the tread layer 11 and the spiral belt layer 3. It is also preferable to arrange a belt reinforcing layer 5 made of a cord. Even if the number of driving of the spiral belt layer is changed between the tire center portion and the tire shoulder portion, the rigidity step at the boundary between the portion where the spiral belt exists and the portion where the spiral belt does not exist is not lost. Therefore, in order to further relax the step, it is difficult to feel this step by providing the belt reinforcing layer 5 that is adjacent to the tread layer 11, that is, as the belt disposed in the outermost layer, continuous from the tire center to the tire shoulder. is doing.

  The reason why the angle of the belt reinforcing layer 5 is set to 90 degrees with respect to the tire equator direction is that the step is most effectively prevented from being felt by arranging the cords along the width direction. Here, the reason why the width is given as an angle of 85 degrees to 90 degrees includes a manufacturing error. Further, the arrangement width of the belt reinforcing layer 5 is 90% or more and 110% or less of the entire width of the tread. The purpose of this member is to prevent the step from being felt, that is, the end of the spiral belt is covered with the member so that the outermost belt is not divided. Therefore, it is preferable to widen the arrangement width and cover the entire area of the tread. If the arrangement width is 90% or more of the total tread width, the step of the spiral belt can be sufficiently covered. In addition, about an upper limit, it may exceed a tread width and may reach a side part. However, if it exceeds 110%, there will also be 90-degree belts on the side of the tire, making the side difficult to bend and causing the tire to become hard (that is, making the tire difficult to bend and riding comfort performance). May worsen). Therefore, the upper limit was made 110%.

  The material of the belt reinforcing layer 5 is organic fiber because the tire for motorcycles has a very round cross section, and if the steel having rigidity on the compression side of the cord is used in the tire width direction, the tire becomes difficult to bend. This is because the ground contact area is reduced. Organic fibers have low rigidity on the compression side of the cord, and there is no fear of reducing the ground contact area.

  In addition, since the reason for providing the belt reinforcing layer 5 is to eliminate the step at the end of the spiral belt, it is meaningless if the diameter of the cord is too thin. On the other hand, if the diameter of the cord is too large, the cord has a rigidity on the compression side although it is an organic fiber. Therefore, the diameter of the cord of the belt reinforcing layer 5 is preferably 0.5 mm or greater and 1.2 mm or less.

  Here, as described above, since the belt crossing layer 4 may be provided inside or outside the spiral belt layer 3, the belt crossing layer 4 is spiral as the arrangement order of these and the belt reinforcing layer 5. When present inside the belt layer 3, the belt reinforcing layer 5 is disposed just outside the spiral belt layer 3 (see FIG. 3). On the other hand, when the belt crossing layer 4 exists outside the spiral belt layer 3, the belt reinforcing layer 5 is disposed on the outer side of the two belt crossing layers 4 just outside the outer belt (not shown). In any case, it is necessary to dispose the belt reinforcing layer 5 immediately inside the tread portion 11 and adjacent to the tread portion 11.

  FIG. 4 shows a cross-sectional view of a pneumatic tire for motorcycles according to still another preferred embodiment of the present invention. In the present invention, when the belt reinforcing layer 5 is disposed, as shown in the drawing, a buffer having a thickness of 0.3 to 1.5 mm is provided on the inner side in the tire radial direction of the belt reinforcing layer 5 and adjacent to the belt reinforcing layer 5. It is also preferable to dispose the rubber layer 6. This buffer rubber layer 6 has an effect of suppressing wear of the tread of the shoulder portion.

  FIG. 6 shows the behavior in the tread width direction when the tire turns at a CA of 50 degrees. On the other hand, in the region where the tread is in contact with the road surface, the tread end portion of FIG. And the tread center area are different. This is because the belt speed is different between the area near the center of the ground contact shape and the area near the tread end of the ground contact shape. A tire for a motorcycle has a large roundness in a cross section in the width direction. Therefore, the belt radius, which is the distance from the rotating shaft to the belt, is larger in the region near the tread center. Therefore, the belt speed, that is, the belt speed until the tread is separated from the road surface after the tread contacts the road surface until the tread moves away from the road surface is higher in the region near the tread center. This is because the belt speed is obtained by multiplying the belt radius by the rotational angular velocity of the tire. Due to the speed difference in the circumferential direction of the belt, the tread is in the driving state near the center of the tire, and the braking state is in the region near the end of the tread of the tire (described above).

  In the present invention, by reducing the width of the spiral belt, the portion of the belt around which the spiral belt is not wound extends along with the grounding in the circumferential direction, the belt speed is improved, and unnecessary deformation of these treads is alleviated. It has been described above. However, reducing the width of the spiral belt to alleviate it does not completely eliminate the extra deformation.

  When the shock absorbing rubber layer 6 is provided on the inner side in the tire radial direction of the belt reinforcing layer 5, the shock absorbing rubber layer 6 shears and deforms in the circumferential direction. Therefore, the driving deformation and braking deformation described above are used instead of the tread as shoulders. The circumferential deformation is further alleviated. On the other hand, since the buffer rubber layer 6 has the belt reinforcing layer 5 along the tire width direction on the upper surface thereof, it is difficult to be sheared and deformed in the tire width direction. Therefore, the deformation of the tread is not replaced with respect to the tire width direction, and the lateral shear deformation of the tread remains large even when the buffer rubber layer 6 is disposed. That is, the cushioning rubber layer 6 shoulders deformation only in the tire circumferential direction, and further reduces grip deformation by reducing deformation in the tread circumferential direction. On the other hand, deformation in the tire width direction does not replace shoulder side deformation of the tread. The deformation is kept large and the lateral force can be kept high. As in the present invention, when the width of the spiral belt is narrowed and such a buffer rubber layer 6 is provided, since unnecessary deformation of the tread in the tire circumferential direction is further suppressed, a great effect is obtained, which is very preferable. . The belt reinforcing layer 5 and the shock absorbing rubber layer 6 are preferably arranged widely, particularly in the range of 90% or more (particularly 110% or less) of the tread width.

  In the tire of the present invention, it is important only to satisfy the above-mentioned conditions relating to the spiral belt layer, whereby the desired effect of the present invention can be obtained, and other conditions such as tire structure and material Is not particularly limited.

For example, the carcass 2 that forms the skeleton of the tire of the present invention 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. Further, both ends of the carcass 2 may be sandwiched and locked by the bead wires 1 from both sides as shown in FIG. 1 or the like, or may be folded around the bead core from the inside of the tire to the outside (not shown). Any 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 11 (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.
<Example 1>
A pneumatic tire for a motorcycle having a cross-sectional structure as shown in FIG. 1 was produced with a tire size of 190 / 50ZR17 in accordance with the following conditions. Each test tire includes a carcass composed of two carcass plies (body plies) extending across a toroid between a pair of bead cores. Here, nylon fiber was used for the carcass ply. The angle of the two carcasses was set to the radial direction (90 degrees with respect to the equator direction). Moreover, the end part of each carcass ply was pinched | interposed and locked from the both sides in the bead part as shown in the figure.

  A spiral belt layer was disposed outside the carcass in the tire radial direction. The spiral belt layer is formed by spirally winding a steel cord in which a steel single wire having a diameter of 0.18 mm is twisted in a 1 × 5 type in the equator direction, that is, spirally wound. A belt-like body (strip) in which a cord is embedded in a coated rubber was manufactured by a method of winding in a tire rotation axis direction spirally along a substantially tire circumferential direction. Further, the number of cords for forming the spiral belt layer was set to 60/50 mm for the 50% width region in the center and 25/50 mm for the 25% width regions from both ends. In this case, the average number of implantations is 25/60 = 0.42 times sparser in both end regions than in the central region.

  Here, the total tread width of each test tire is 240 mm along the tread surface. Further, since the total width of the spiral belt layer is 170 mm, which is 0.71 times the total width of the tread, in this case, the number of driving in the portion of the spiral belt layer having a width of 85 mm in the tire center portion is 60/50 mm. The number of driving in the portion of the tire shoulder portion having a width of 42.5 mm is 25/50 mm.

  In addition, a belt reinforcing layer made of an aromatic polyamide fiber having an angle of 90 degrees with respect to the tire circumferential direction was disposed outside the spiral belt layer in the tire radial direction. For the belt reinforcing layer, cords having a diameter of 0.7 mm formed by twisting aromatic polyamide fibers were arranged at an angle of 90 degrees with respect to the tire circumferential direction at a driving number of 50/50 mm. The width of the belt reinforcement layer was the same as the tread width. A tread layer having a thickness of 7 mm is disposed outside the belt reinforcing layer in the tire radial direction, and a predetermined groove is disposed on the surface thereof.

  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.

<Example 2>
A pneumatic tire for a motorcycle having a cross-sectional structure as shown in FIG. 2 was produced according to the following conditions. One carcass ply was arranged in the radial direction (angle with respect to the equator direction is 90 degrees). Further, two belt crossing layers were arranged outside the spiral belt layer in the tire radial direction without arranging the belt reinforcing layer. The belt crossing layer was formed by placing cords having a diameter of 0.5 mm twisted from aromatic polyamide fibers and placing them at a number of 50/50 mm. The angle of the belt crossing layers was ± 60 degrees with respect to the tire circumferential direction, and crossed each other. The arrangement width of the belt crossing layer was 250 mm for the first sheet (inner side) and 230 mm for the second sheet (outer side).

<Example 3>
A pneumatic tire for a motorcycle having a cross-sectional structure as shown in FIG. 3 was produced according to the following conditions. One carcass ply was arranged in the radial direction (angle with respect to the equator direction is 90 degrees). In addition, two belt crossing layers similar to those in Example 2 were arranged on the inner side in the tire radial direction of the spiral belt layer. Therefore, in this case, the belt crossing layer exists just outside the carcass, and the spiral belt layer exists outside the belt crossing layer. Further, on the outer side in the tire radial direction of the spiral belt layer, a belt reinforcing layer made of an aromatic polyamide fiber having an angle with respect to the tire circumferential direction of 90 degrees was arranged in the same manner as in Example 1. A tread exists outside the belt reinforcing layer.

<Example 4>
A pneumatic tire for a motorcycle was manufactured in the same manner as in Example 3 except that the belt reinforcing layer was not disposed on the outer side in the radial direction of the spiral belt layer.

<Example 5>
4 has a cross-sectional structure as shown in FIG. 4 except that a buffer rubber layer having a thickness of 0.6 mm is disposed on the inner side of the belt reinforcing layer of Example 3 and adjacent to the belt reinforcing layer. A pneumatic tire for a motorcycle was produced. The material of the buffer rubber layer was the same as the coating rubber used for the belt reinforcing layer. The arrangement width was also the same as the arrangement width 240 mm of the belt reinforcing layer.

<Examples 6 to 9>
A pneumatic tire for a motorcycle was manufactured in the same manner as in Example 3 except that the number of driven spiral belt layers and the total width were changed as shown in the following table.

<Conventional example>
A pneumatic tire for a motorcycle having a cross-sectional structure as shown in FIG. 5 was produced according to the following conditions. For Conventional Examples 1 and 2, the number of carcass plies is one, and they are arranged in the radial direction (angle with respect to the equator direction is 90 degrees). In the conventional example 3, the number of carcass plies is two and they are arranged in the radial direction (the angle with respect to the equator direction is 90 degrees). On the outside thereof, the belt crossing layers similar to those of Example 3 were arranged for Conventional Examples 1 and 2.

  Further, as for the spiral belt layer, in the conventional example 1, a steel belt was used, and the number of driving was fixed to 25/50 mm. Also, in the conventional example 2, a steel belt was used, and the number of driving was fixed to 60/50 mm. Further, in the conventional example 3, a steel belt was used, and the number of driving was fixed to 40/50 mm.

<Comparative Example 1>
A pneumatic tire for a motorcycle was manufactured in the same manner as in Example 3 except that the spiral belt layer was a steel belt and the number of shots was constant and 25 pieces / 50 mm.

<Comparative example 2>
A pneumatic tire for a motorcycle was manufactured in the same manner as in Example 3 except that the spiral belt layer was a steel belt and the number of shots was constant and 60/50 mm.

<Comparative Example 3>
A pneumatic tire for a motorcycle was manufactured in the same manner as in Example 3 except that the number of driven spiral belt layers and the total width were changed as shown in the following table.

  The specified test was performed on each of the obtained test tires.

<Drum test>
First, it was measured using a drum whether the traction when the vehicle body was tilted, which is the main object of the present invention, was improved. The method of measuring traction using a drum is as follows.

  As a testing machine, sandpaper was affixed to a drum having a diameter of 3 m, and the surface of the sandpaper was regarded as a road surface. The drum was rolled at a speed of 80 km / h, and a tire was pressed onto the drum at a CA of 35 degrees and a CA of 50 degrees. Each test tire was filled with an internal pressure of 240 kPa and pressed with a load of 150 kgf. The tire has a chain that transmits power to the rotating shaft, and a driving force can be applied. The driving force was applied using a motor. The tire was rotated at 80 km / h, driving force was applied, and the tire was linearly accelerated to 120 km / h over a period of 3 seconds. At this time, since the drum is rolling at 80 km / h, a driving force is applied to the tire, and the traction can be measured with the vehicle body tilted.

  The force acting in the direction parallel to the tire rotation axis (that is, the tire width direction) and the force acting in the direction perpendicular to the tire rotation axis are measured by a force sensor installed at the center of the tire wheel, and this force is The force in the drum width direction and the drum rotation direction are decomposed according to the camber angle, the drum width direction force is Fy, and the drum rotation direction force is Fx (Fx and Fy are coordinates with respect to the ground). . That is, Fy indicates a lateral force for turning the motorcycle, and Fx indicates a driving force for accelerating the motorcycle. By drawing these as Fx on the horizontal axis and Fy on the vertical axis, a waveform as shown in FIG. 7 is obtained. Although this is called a friction ellipse, the intercept of Fy at Fx0 indicates a pure lateral force at a driving force of 0, and this is a force called camber thrust. In this test, the grip performance of a tire in a traction state can be evaluated by applying a driving force to the tire to accelerate the rotation of the tire. With time, the waveform of the graph moves in the positive direction of Fx. The maximum value of Fx can be said to be an index of traction grip.

  With the maximum value of Fx of the test tire of Conventional Example 1 being 100, the performance of other examples was evaluated by an index. This was done for two levels of CA 35 degrees and CA 50 degrees. The results are shown in the table below.

<Driving 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 each of the test tires was a rear tire, an actual vehicle test was performed by exchanging only the rear tire. The front tire was always fixed with a conventional one. The evaluation method is shown below.

  Each test tire was mounted on a 1000cc sports-type motorcycle, and the vehicle was run on a test course. The steering stability (cornering performance) was comprehensively evaluated by a 10-point method based on the feeling of the test rider. On the course, the motorcycle ran intensely in consideration of motorcycle racing, and the maximum speed reached 180 km / h. The test items are low-speed corner traction performance (acceleration performance from a state where the vehicle body is greatly lowered at a speed of 50 km / h), high-speed corner traction performance (acceleration performance from a state where the vehicle body is slightly lowered at a speed of 120 km / h), The grip stability (discontinuity) when the car body is tilted down.

  Moreover, the partial wear state of the tire shoulder part when 10 laps of test courses were run was confirmed. The amount of wear of the tire shoulder portion was measured, and the amount of wear of another example when the amount of wear of the tire of Conventional Example 1 was set to 100 was shown as an index. About the amount of wear, the smaller the value, the less the wear and the better. The amount of wear was determined by measuring the weight of the tire when it was new and comparing the weight of the tire at the end of the test. After the test, most of the wear occurred in the shoulder portion, and the difference in weight can be said to be the difference in wear of the shoulder portion. The results are also shown in the table below.

From the above results, the following can be understood.
First, for each of the examples, it is clear that the stability at the time of tilting is significantly improved as compared with Comparative Example 1 and Comparative Example 2 in which the spiral belt width is narrowed with a single member. It can be seen that it is important to reduce the rigidity step. In Example 1, there is no belt crossing layer. Therefore, manufacturing costs can be saved. Further, compared with the conventional example 3 in the comparison of the example 1 without the belt crossing layer, the Fx index of both CA 35 degrees and CA 50 degrees is improved in both the low speed corners and the high speed corners. The performance is getting better. Wear has also improved.

  Example 2 and Example 4 are cases where two belt crossing layers are provided. Compared with the conventional examples 1 and 2, both the traction performance and the wear resistance performance are significantly improved. Further, the comparison between Example 4 and Example 6 shows the effect of disposing the buffer rubber layer. Further, traction performance and wear resistance performance in one step are obtained by the buffer rubber layer.

  From the comparison between Example 4 and Examples 3 and 5, the effect of the arrangement of the belt reinforcing layer and the buffer rubber layer on the stability at the time of tilting can be seen. By adding the belt reinforcing layer and the buffer rubber layer, the rigidity step is further eliminated and the stability is increased.

  From the relationship between Example 3, Example 6, and Example 7, the influence of the arrangement width of the spiral belt layer can be seen. When the spiral belt width is widened, the Fx index at the time of large CA is improved, that is, a large effect is obtained at a low-speed corner at the time of large CA that greatly depresses the vehicle body. However, if it is completely wide like the conventional example, there is no effect of improving the traction performance. On the other hand, if the spiral belt width is narrowed, a large effect can be obtained when the CA is small, that is, at a high-speed corner of about 35 degrees CA. However, if it is made too narrow as in Comparative Example 3, the effect is lost.

  From the comparison between Example 3 and Example 8, the difference between the case of using the steel spiral belt and the case of using the Kevlar spiral belt can be seen. When the Kevlar spiral belt is used, the rigidity difference at both ends is further relaxed, so the stability when the vehicle body is lowered is improved, but the traction performance is slightly reduced. Moreover, from the relationship between Example 3 and Example 9, the influence of the difference in the number of driving of a shoulder part is understood. When the difference in the number of driving is small as in the ninth embodiment, the spiral belt cords in both end regions become dense, the rigidity step is increased, and stability when the vehicle body is tilted is lost.

  In Example 5, a belt reinforcing layer and a buffer rubber layer are added to the narrow spiral belt layer according to the present invention. In this evaluation, Example 5 shows the best results in all of the traction performance, the stability performance when collapsed and the wear resistance performance, and the performance improvement at a significantly higher level is achieved as compared with the conventional example. You can see that it is made. In addition, the falling stability performance of the vehicle body exceeded the conventional example in which the spiral belt was arranged to the end, and this confirmed the effect of the combination of the preferred conditions of the present invention.

  From the above results, it is confirmed that the present invention makes it possible to achieve a high level of compatibility between the steering stability performance (traction performance) when turning the vehicle body greatly and the stability when the vehicle body is brought down. It was.

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. FIG. 5 is a cross-sectional view in the width direction showing a pneumatic tire for a motorcycle according to still another preferred embodiment of the present invention. FIG. 5 is a cross-sectional view in the width direction showing a pneumatic tire for a motorcycle according to still another preferred embodiment of the present invention. It is sectional drawing of the width direction which shows the pneumatic tire for two-wheeled vehicles which concerns on a prior art example. 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). It is a graph which shows the friction ellipse which shows the relationship between Fx and Fy.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 3 Spiral belt layer 4 Belt crossing layer 5 Belt reinforcement layer 6 Buffer rubber layer 11 Tread part 12 Side wall part 13 Bead part

Claims (4)

In a pneumatic tire for a motorcycle including a tread portion formed in an annular shape,
A spiral belt layer having an angle with respect to the tire circumferential direction of 0 to 5 degrees and an arrangement width of 0.5 to 0.8 times the tread width is provided on the inner side in the tire radial direction of the tread portion, The number of cords forming the spiral belt layer is different between the tire center portion and the tire shoulder portion, and the average number of cords driven in a region having a width of 25% from both ends of the spiral belt layer is the spiral belt layer. Is less than the average number of codes in the 50% width region, and the average number of both end regions is not less than 0.2 times and not more than 0.8 times the average number of the center regions. This is a pneumatic tire for motorcycles.   A belt intersection layer made of organic fibers that is wider than the spiral belt layer and has an angle with respect to the tire circumferential direction of 30 degrees or more and less than 85 degrees is disposed adjacent to the spiral belt layer. The pneumatic tire for motorcycles according to 1.   Between the tread layer and the spiral belt layer, adjacent to the tread layer, a belt reinforcing layer made of an organic fiber cord having an angle with respect to the tire circumferential direction of 85 degrees to 90 degrees is 90% or more of the tread width. The pneumatic tire for a motorcycle according to claim 1 or 2, wherein the pneumatic tire is arranged with a width of% or less.   The pneumatic tire for a motorcycle according to claim 3, wherein a shock absorbing rubber layer having a thickness of 0.3 to 1.5 mm is disposed on the inner side in the tire radial direction of the belt reinforcing layer and adjacent to the belt reinforcing layer.

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