JP6040100B2 - Pneumatic tires for motorcycles - Google Patents

Description

  The present invention relates to a pneumatic tire mounted on a motorcycle. In particular, the present invention relates to improvements in tire treads.

  When the motorcycle turns, centrifugal force acts on the motorcycle. For cornering, a cornering force that balances this centrifugal force is required. For this reason, the rider tilts the motorcycle inward during turning. Turning is achieved by the camber thrust generated by this inclination. For the purpose of facilitating turning, motorcycle tires have a tread with a small radius of curvature.

  When the motorcycle travels straight, the center area of the tread comes into contact with the ground because the motorcycle is almost upright. At this time, since motorcycles often run at high speed, tires are required to have running stability. On the other hand, when the motorcycle turns, since the motorcycle is inclined, the shoulder region of the tread is grounded. At this time, since the lateral force applied to the tire increases, the tire requires a high grip force. In consideration of these matters, tires using different rubber for each tread region are disclosed in Japanese Patent Laid-Open Nos. 2005-271760, 2007-131112, 2008-302817, and 2010-111163. Has been.

  In the tire disclosed in Japanese Patent Application Laid-Open No. 2005-271760, high-hardness rubber is used in the center region of the tread. The shoulder region has a two-layer structure in which low-hardness rubber is laminated on the outer side in the radial direction of high-hardness rubber. The surface of the shoulder region is made of low hardness rubber.

  In the tire disclosed in Japanese Patent Application Laid-Open No. 2007-131112, the center region of the tread is composed of rubber with a high loss tangent (also referred to as tan δ), and the shoulder region is composed of rubber with a low loss tangent.

  In the tires disclosed in Japanese Patent Application Laid-Open Nos. 2008-302817 and 2010-111163, the tread includes a region located at the center and N regions located on the shoulder side from here. The rubber hardness of the center region is the highest and the region located on the shoulder side has a lower rubber hardness.

JP-A-2005-271760 JP 2007-131112 A JP 2008-302817 A JP 2010-111163 A

  A motorcycle sometimes turns with a large inclination (referred to as “full bank”) and turns with a relatively gentle inclination (referred to simply as “when turning”). At the time of full bank, the shoulder region is mainly grounded. The shoulder region is required to have the highest grip strength compared to other portions. On the other hand, when turning, the vicinity of the boundary between the center region and the shoulder region of the tire is mainly grounded. The vicinity of this boundary is called a middle region. The middle region is also required to have enough grip to withstand the lateral force of turning. The middle region contacts the ground every time the motorcycle turns. The middle area also comes into contact with the ground when moving from straight to full bank. Usually, the middle region is grounded more frequently than the shoulder region. Moreover, a large load is applied to the middle region during high-speed turning or acceleration from turning. For this reason, high wear resistance is required in the middle region in addition to gripping force.

  In the tire disclosed in Japanese Patent Application Laid-Open No. 2005-271760, the surface of the middle region is composed of either a low hardness rubber for the shoulder region or a high hardness rubber for the center region. When the surface of the middle region is made of low-hardness rubber, the surface is worn in a short time due to the above-described load. This wear of the surface causes a decrease in grip force during turning. On the other hand, in a tire in which the middle region is composed of high-hardness rubber, sufficient grip force cannot be obtained during turning.

  The same problem remains in the tire disclosed in Japanese Patent Laid-Open No. 2007-131112. If the middle region is made of high loss tangent rubber, its surface will wear in a short period of time. On the other hand, if this region is made of low loss tangent rubber, sufficient grip force cannot be obtained during turning.

  In the tires disclosed in Japanese Patent Application Laid-Open Nos. 2008-302817 and 2010-111163, the middle region is made of rubber having a lower hardness than the center region and a higher hardness than the shoulder region. However, with a single rubber, it is difficult to achieve both high grip strength and wear resistance.

  An object of the present invention is to provide a tire for a motorcycle that is excellent in turning performance, full bank traveling, and straight traveling performance, and that has excellent tread wear resistance.

  The pneumatic tire for motorcycles according to the present invention includes a tread whose surface forms a tread surface. The tread has a first rubber, a second rubber, and a third rubber. The tread includes a central portion positioned at the center, a pair of intermediate portions each positioned outside the central portion in the axial direction, and a pair of end portions positioned respectively outside the intermediate portions in the axial direction. The central portion has the first rubber. The intermediate portion includes the first rubber, the third rubber stacked on the radially outer side of the first rubber, and the second rubber stacked on the radially outer side of the third rubber. The end portion has the first rubber and the third rubber laminated on the outer side in the radial direction of the first rubber. The loss tangent LT1 of the first rubber is lower than the loss tangent LT2 of the second rubber, and the loss tangent LT2 is lower than the loss tangent LT3 of the third rubber. The hardness H1 of the first rubber is higher than the hardness H2 of the second rubber, and the hardness H2 is higher than the hardness H3 of the third rubber.

  Preferably, the loss tangent LT1 is not less than 0.23 and not more than 0.25, the loss tangent LT2 is not less than 0.25 and not more than 0.35, and the loss tangent LT3 is not less than 0.28 and not more than 0.49. is there.

  Preferably, the hardness H1 is 37 or more and 55 or less, the hardness H2 is 33 or more and 43 or less, and the hardness H3 is 30 or more and 34 or less.

  Preferably, a ratio (Wc / W) of the length Wc of the central portion measured along the tread surface to the length W of the tread surface is 0.15 or more and 0.30 or less, and the tread The ratio (We / W) between the total length We of the pair of end portions measured along the surface and the length W of the tread surface is 0.10 or more and 0.20 or less.

  The tire according to the present invention includes an “intermediate portion” for dealing with the above-described problem with respect to the middle region. The surface of the intermediate part is made of the second rubber. The loss tangent of the second rubber is higher than the loss tangent of the first rubber and lower than the loss tangent of the third rubber. The hardness of the second rubber is lower than that of the first rubber and higher than that of the third rubber. The second rubber has a medium hardness and a medium loss tangent. This rubber contributes to the improvement of the wear resistance of the intermediate part. The tire having the intermediate portion can suppress a decrease in grip force due to wear of the tread surface during turning. Further, a third rubber having a low hardness and a high loss tangent exists inside the second rubber in the radial direction. This third rubber contributes to an improvement in grip force. The tire having this intermediate portion has a high grip force when turning. Further, a first rubber having a high hardness and a low loss tangent exists inside the third rubber in the radial direction. This first rubber contributes to the improvement of the rigidity of the intermediate portion. The tire provided with this intermediate portion is excellent in running stability during turning. By configuring the middle region of the tire at the middle portion, a tire having excellent wear resistance, grip strength and running stability during turning can be obtained.

  The tire includes a “central portion” for forming a center region. The central portion is composed of a first rubber having high hardness and low loss tangent. Thereby, a center part has big rigidity. The tire provided with this central portion is excellent in running stability when going straight. The tire further includes an “end” for forming a shoulder region. The surface of this end is made of a third rubber having a low hardness and a high loss tangent. The grip strength of the end portion whose surface is made of the third rubber is large. The tire provided with this end portion has a sufficient grip force in a full bank.

  ADVANTAGE OF THE INVENTION According to this invention, the tire for motorcycles which is excellent in the performance of turning driving | running | working, a full bank driving | running | working, and a straight drive | running | working and excellent in the abrasion resistance of a tread can be provided.

FIG. 1 is a cross-sectional view showing a part of a tire according to an embodiment of the present invention.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 shows a pneumatic tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire 2. The shape of the tire 2 is symmetrical with respect to the equator plane except for the tread pattern.

  The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, an inner liner 12, a belt 14, a band 16, and a chafer 18. The tire 2 is a tubeless type. The tire 2 is attached to a motorcycle.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 20 that contacts the road surface. Although not shown, the tread surface 20 has grooves. A tread pattern is formed by this groove. The tread 4 need not be grooved.

  The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. This sidewall 6 is made of a crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 6 prevents the carcass 10 from being damaged.

  The bead 8 extends from the sidewall 6 substantially inward in the radial direction. The bead 8 includes a core 22 and an apex 24 that extends radially outward from the core 22. The core 22 is ring-shaped and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 24 is tapered outward in the radial direction. The apex 24 is made of a highly hard crosslinked rubber.

  The carcass 10 includes a first ply 10a and a second ply 10b. The first ply 10 a and the second ply 10 b extend along the inner surfaces of the tread 4 and the sidewall 6. The first ply 10a forms an inner portion of the carcass 10 in the radial direction. The first ply 10a is folded around the core 22 from the inner side to the outer side in the axial direction. The second ply 10b is located on the radially outer side of the first ply 10a. The second ply 10b is laminated with the first ply 10a.

  Although not shown, each carcass ply includes a plurality of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is 75 ° to 90 °. In other words, the carcass 10 has a radial structure. The cord is made of organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. The carcass 10 may be formed from a single ply.

  The belt 14 is located on the inner side in the radial direction of the tread 4. The belt 14 is laminated with the carcass 10. The belt 14 reinforces the carcass 10. The belt 14 includes an inner layer 14a and an outer layer 14b. Although not shown, each of the inner layer 14a and the outer layer 14b is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane. The absolute value of the tilt angle is usually 10 ° to 35 °. The inclination direction of the cord of the inner layer 14a with respect to the equator plane is opposite to the inclination direction of the cord of the outer layer 14b with respect to the equator plane. A preferred material for the cord is steel. An organic fiber may be used for the cord.

  The band 16 is located on the inner side in the radial direction of the tread 4. The band 16 is located on the radially outer side of the belt 14. The band 16 is laminated on the belt 14. The band 16 is made of a cord and a topping rubber. The cord is wound in a spiral. The band 16 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is 5 ° or less, and further 2 ° or less. The band 16 can contribute to the radial rigidity of the tire 2. The band 16 can suppress the influence of centrifugal force that acts during traveling. The tire 2 is excellent in high speed stability. A preferred material for the cord is steel. An organic fiber may be used for the cord. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The belt 14 and the band 16 constitute a reinforcing layer. The reinforcing layer may be formed only from the belt 14. A reinforcing layer may be formed only from the band 16.

  The inner liner 12 is located inside the carcass 10. The inner liner 12 is joined to the inner surface of the carcass 10. The inner liner 12 is made of a crosslinked rubber. The inner liner 12 is made of rubber having excellent air shielding properties. A typical base rubber of the inner liner 12 is butyl rubber or halogenated butyl rubber. The inner liner 12 holds the internal pressure of the tire 2.

  As shown in FIG. 1, the tread 4 includes a first rubber 26, a second rubber 28, and a third rubber 30. The tread 4 includes a central portion, a pair of intermediate portions, and a pair of end portions. In FIG. 1, a symbol C represents a central portion, a symbol M represents an intermediate portion, and a symbol E represents an end portion.

  The central part C is located at the center of the tread 4. The central portion C has the first rubber 26. The central portion C is composed of the first rubber 26. The first rubber 26 is laminated on the outer side in the radial direction of the band 16. The first rubber 26 forms the tread surface 20 of the central portion C.

  Each of the pair of intermediate portions M is located outside the central portion C in the axial direction. In FIG. 1, only one of the pair of intermediate portions M is shown. The other intermediate part M has the same structure. The intermediate part M has the first rubber 26, the second rubber 28 and the third rubber 30. The intermediate part M is composed of the first rubber 26, the second rubber 28 and the third rubber 30. The first rubber 26 is laminated on the outer side in the radial direction of the band 16. The third rubber 30 is laminated outside the first rubber 26 in the radial direction. The second rubber 28 is laminated on the outer side in the radial direction of the third rubber 30. The second rubber 28 forms the tread surface 20 of the intermediate portion M.

  Each of the pair of end portions E is located outside the intermediate portion M in the axial direction. In FIG. 1, only one of the pair of end portions E is shown. The other end E has the same structure. The end E has the first rubber 26 and the third rubber 30. The end E is composed of the first rubber 26 and the third rubber 30. The first rubber 26 is laminated on the outer side in the radial direction of the band 16. The third rubber 30 is laminated outside the first rubber 26 in the radial direction. The third rubber 30 forms the tread surface 20 of the end E.

  As shown in FIG. 1, the first rubber 26 in the central portion C, the first rubber 26 in the intermediate portion M, and the first rubber 26 in the end portion E are connected. In other words, the first rubber 26 extends from the central portion C to the end portion E. Further, the third rubber 30 at the intermediate portion M and the third rubber 30 at the end portion E are connected. In other words, the third rubber 30 extends from the intermediate portion M to the end portion E.

  As described above, in the present embodiment, the first rubber 26 is laminated on the radially outer side of the band 16. A base layer made of a crosslinked rubber may be present between the first rubber 26 and the band 16.

  The first rubber 26, the second rubber 28, and the third rubber 30 are each a crosslinked rubber composition (crosslinked rubber). The loss tangent LT1 of the first rubber 26 is lower than the loss tangent LT2 of the second rubber 28, and the loss tangent LT2 of the second rubber 28 is lower than the loss tangent LT3 of the third rubber 30. The hardness H1 of the first rubber 26 is higher than the hardness H2 of the second rubber 28, and the hardness H2 of the second rubber 28 is higher than the hardness H3 of the third rubber 30.

In the present invention, the loss tangents LT1, LT2 and LT3 are measured in accordance with the provisions of “JIS K 6394”. The measurement conditions are as follows.
Viscoelastic spectrometer: "VESF-3" manufactured by Iwamoto Seisakusho
Initial strain: 10%
Amplitude: ± 2.5%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 100 ° C

  In the present invention, the hardnesses H1, H2, and H3 are JIS-A hardnesses. This hardness is measured with a type A durometer in an environment of 23 ° C. in accordance with the provisions of “JIS-K6253”. More specifically, the hardness is measured by pressing a type A durometer against the cross section shown in FIG.

  Hereinafter, the manufacturing method of this tire 2 is shown.

  Although not shown, in the manufacture of the tire 2, the inner liner 12, the carcass 10, and the belt 14 are sequentially wound around the former. On the belt 14, a ribbon made of a cord and a topping rubber is spirally wound to form a band 16 having a jointless structure.

  On the band 16, a first strip made of a rubber composition for the first rubber 26, a second strip made of a rubber composition for the second rubber 28, and a rubber composition for the third rubber 30. Each third strip is spirally wound. These strips extend substantially circumferentially. These strips are laminated sequentially. In this way, a raw cover is obtained. The winding method from the first strip to the third strip, the winding order and the winding thickness of each strip are appropriately adjusted according to the configuration of the tread 4 described above.

  This raw cover is put into a mold of a vulcanizer. In this vulcanizer, a bladder is provided inside the mold. When thrown, the bladder is contracted. The inside of the bladder is filled with gas, and the bladder expands. The raw cover is pressed against the cavity surface of the mold by a bladder. The raw cover is pressurized and heated by a mold. The rubber composition of the raw cover flows by pressurization and heating. By heating, the rubber of the raw cover causes a crosslinking reaction, and the tire 2 is obtained. The first rubber 26 is obtained from the layer on which the first strip is wound. The second rubber 28 is obtained from the layer on which the second strip is wound. The third rubber 30 is obtained from the layer on which the third strip is wound. In the tire 2, the central portion C, the intermediate portion M, and the end portion E are formed by winding these three types of strips. The tread 4 is easy to manufacture.

  Below, the effect of this invention is demonstrated.

  When the motorcycle turns, the middle region of the tire 2 is mainly grounded. In the tire 2, the intermediate portion M is grounded at this time. A large load is applied to the intermediate portion M during high-speed turning or acceleration from turning. In the tire 2 according to the present invention, the surface of the intermediate portion M is constituted by the second rubber 28. As described above, the loss tangent LT2 of the second rubber 28 is higher than the loss tangent LT1 of the first rubber 26 and lower than the loss tangent LT3 of the third rubber 30. Further, the hardness H2 of the second rubber 28 is lower than the hardness H1 of the first rubber 26 and higher than the hardness H3 of the third rubber 30. The second rubber 28 has a medium hardness and a medium loss tangent. This rubber is excellent in wear resistance. In other words, the intermediate portion M is excellent in wear resistance. In the tire 2 including the intermediate portion M, even when a large load is applied to the intermediate portion M during high-speed turning or acceleration after turning, a decrease in grip force during turning due to wear of the tread surface 20 is suppressed.

  When turning for a motorcycle, the motorcycle is tilted. At this time, since the lateral force applied to the tire 2 is increased, the intermediate portion M is required to have a high grip force. In the middle part M of the tire 2, the third rubber 30 exists inside the second rubber 28 in the radial direction. The loss tangent LT3 of the third rubber 30 is higher than the loss tangent of the first rubber 26 and the second rubber 28, and the hardness H3 of the third rubber 30 is the hardness of the first rubber 26 and the second rubber 28. Low compared. The high loss tangent and low hardness of the third rubber 30 contribute to the improvement of the grip force of the intermediate portion M. The tire 2 including the intermediate portion M has a high grip force when turning.

  In the intermediate portion M, the first rubber 26 exists inside the third rubber 30 in the radial direction. The loss tangent LT1 of the first rubber 26 is lower than the loss tangent of the second rubber 28 and the third rubber 30, and the hardness H1 of the first rubber 26 is equal to the hardness of the second rubber 28 and the third rubber 30. Higher than that. Since the intermediate portion M includes the first rubber 26 having a low loss tangent and a high hardness, the intermediate portion M has sufficient rigidity. The tire 2 having the intermediate portion M is excellent in running stability during turning.

  When the motorcycle goes straight, the center region of the tire 2 is mainly grounded. In the tire 2, the central portion C is grounded at this time. Since the motorcycle often runs at a high speed when going straight, the tire 2 is required to have high running stability. Further, a large load is applied to the central portion C during acceleration and deceleration. For this reason, the central portion C is required to have high wear resistance. In the tire 2 according to the present invention, the central portion C is composed of a first rubber 26 having a low loss tangent and a high hardness. The central portion C having the first rubber 26 has great rigidity. This contributes to running stability during straight travel. The first rubber 26 has high wear resistance. The tire 2 having the central portion C is excellent in wear resistance when traveling straight.

  When the motorcycle is running on a full bank, the shoulder region of the tire 2 is mainly grounded. At this time, in the tire 2, the end E is grounded. At the time of the full bank, a very large lateral force is applied to the tire 2, so that the end portion E is required to have a higher grip force than that during normal turning. In the tire 2 according to the present invention, the surface of the end E is composed of the third rubber 30 having a high loss tangent and low hardness. The grip force of the end E having this rubber is strong. The tire 2 provided with the end E has a sufficient grip force even for full bank travel. In addition, at the end E, the first rubber 26 having a low loss tangent and a high hardness exists inside the third rubber 30 in the radial direction. Due to the first rubber 26, the end E has sufficient rigidity. The tire 2 provided with the end E is excellent in running stability during full banking.

  The loss tangent LT2 of the second rubber 28 is preferably 0.35 or less. The intermediate portion M including the second rubber 28 having a loss tangent LT2 of 0.35 or less is excellent in wear resistance during turning. In this respect, LT2 is more preferably equal to or less than 0.32. The loss tangent LT2 is preferably 0.25 or more. The intermediate portion M provided with the second rubber 28 having a loss tangent LT2 of 0.25 or more is excellent in gripping force during turning. In this respect, LT2 is more preferably equal to or greater than 0.28.

  The hardness H2 of the second rubber 28 is preferably 33 or more. The intermediate part M provided with the second rubber 28 having a hardness H2 of 33 or more is excellent in wear resistance during turning. In this respect, H2 is more preferably equal to or greater than 35. The hardness H2 is preferably 43 or less. The intermediate part M provided with the second rubber 28 having a hardness H2 of 43 or less is excellent in gripping force during turning. In this respect, H2 is more preferably 41 or less.

  The loss tangent LT1 of the first rubber 26 is preferably 0.25 or less. The central portion C, the intermediate portion M, and the end portion E provided with the first rubber 26 having a loss tangent LT1 of 0.25 or less contribute to excellent running stability during straight traveling, turning, and full banking. The loss tangent LT1 is preferably 0.23 or more. The central portion C, the intermediate portion M, and the end portion E provided with the first rubber 26 having a loss tangent LT1 of 0.23 or more contribute to excellent riding comfort during straight travel, turning, and full bank travel.

  The hardness H1 of the first rubber 26 is preferably 37 or more. The central portion C, the intermediate portion M, and the end portion E provided with the first rubber 26 having a hardness H1 of 37 or more contribute to excellent running stability during straight travel, turning, and full banking. In this respect, H1 is more preferably equal to or greater than 40. The hardness H1 is preferably 55 or less. The central portion C, the intermediate portion M, and the end portion E provided with the first rubber 26 having a hardness H1 of 55 or less contribute to excellent riding comfort during straight travel, turning, and full banking. In this respect, H1 is more preferably 50 or less.

  The loss tangent LT3 of the third rubber 30 is preferably 0.28 or more. The end portion E and the intermediate portion M provided with the third rubber 30 having a loss tangent LT3 of 0.28 or more are excellent in gripping force during full banking and turning. In this respect, LT3 is more preferably equal to or greater than 0.32. The loss tangent LT3 is preferably 0.49 or less. The end E provided with the third rubber 30 having a loss tangent LT3 of 0.49 or less is excellent in wear resistance during full banking. In this respect, LT3 is more preferably equal to or less than 0.45.

  The hardness H3 of the third rubber 30 is preferably 34 or less. The end portion E and the intermediate portion M provided with the third rubber 30 having a hardness H3 of 34 or less are excellent in gripping force during full banking and turning. In this respect, H3 is more preferably 33 or less. The hardness H3 is preferably 30 or more. The end E provided with the third rubber 30 having a hardness H3 of 30 or more is excellent in wear resistance during full banking. In this respect, H3 is more preferably 31 or more.

  The ratio (LT2 / LT1) between the loss tangent LT2 and the loss tangent LT1 is preferably 1.10 or more and 1.40 or less. In the tire 2 including the first rubber 26 and the second rubber 28 having a ratio (LT2 / LT1) of 1.10 or more, the running stability during straight traveling by the low loss tangent LT1 and the medium loss tangent LT2 are obtained. Grip characteristics when turning can be compatible. In the tire 2 including the first rubber 26 and the second rubber 28 having a ratio (LT2 / LT1) of 1.40 or less, when the ground contact surface of the tread 4 shifts from the central portion C to the intermediate portion M, The rider is less likely to feel discomfort due to the difference in rubber material.

  The ratio (H1 / H2) between the hardness H1 and the hardness H2 is preferably 1.10 or more and 1.30 or less. In the tire 2 provided with the first rubber 26 and the second rubber 28 having a ratio (H1 / H2) of 1.10 or more, the running stability during straight traveling due to the high hardness H1 and the moderate hardness H2 are caused. Grip characteristics when turning can be compatible. In the tire 2 including the first rubber 26 and the second rubber 28 having a ratio (H1 / H2) of 1.30 or less, when the ground contact surface of the tread 4 shifts from the central portion C to the intermediate portion M, The rider is less likely to feel discomfort due to the difference in rubber material.

  The ratio of loss tangent LT3 to loss tangent LT2 (LT3 / LT2) is preferably 1.10 or more and 1.30 or less. In the tire 2 including the second rubber 28 and the third rubber 30 having a ratio (LT3 / LT2) of 1.10 or more, wear resistance during turning by a medium loss tangent LT2 and high loss tangent LT3 Grip characteristics at full bank can be compatible. In the tire 2 including the second rubber 28 and the third rubber 30 having a ratio (LT3 / LT2) of 1.30 or less, when the ground contact surface of the tread 4 is shifted from the intermediate portion M to the end portion E, The rider is less likely to feel discomfort due to the difference in rubber material.

  The ratio of the hardness H2 to the hardness H3 (H2 / H3) is preferably 1.10 or more and 1.25 or less. In the tire 2 provided with the second rubber 28 and the third rubber 30 having this ratio (H2 / H3) of 1.10 or more, wear resistance during turning with a medium hardness H2 and low hardness H3. The grip characteristics at full bank can be compatible. In the tire 2 including the second rubber 28 and the third rubber 30 having a ratio (H2 / H3) of 1.25 or less, when the ground contact surface of the tread 4 is shifted from the intermediate portion M to the end portion E, The rider is less likely to feel discomfort due to the difference in rubber material.

  In FIG. 1, a double arrow Wc (one arrow is not shown) indicates a length measured along the tread surface 20 of the central portion C. Specifically, the length Wc is along the tread surface 20 between the axially inner end 32 of one second rubber 28 and the axially inner end of the other second rubber 28 (not shown). The length to be measured. Although not shown, the length W of the tread surface 20 is a length measured along the tread surface 20 between one tread end 36 and the other tread end. The ratio of the length Wc to the length W (Wc / W) is preferably 0.15 or more and 0.30 or less. The tire 2 having this ratio of 0.15 or more has a sufficient size of the central portion C to obtain good running stability during straight running. The tire 2 is excellent in running stability when going straight. In this respect, the ratio is more preferably equal to or greater than 0.18. The tire 2 having this ratio (Wc / W) of 0.30 or less has a size of the intermediate portion M sufficient to obtain a favorable turning grip force. The tire 2 is excellent in gripping power when turning. In this respect, the ratio is more preferably equal to or less than 0.25.

  In FIG. 1, a double-headed arrow We1 indicates a length measured along the tread surface 20 of one end E. Specifically, the length We1 is a length measured along the tread surface 20 between the axially outer end 34 and the tread end 36 of the second rubber 28. Although not shown, the length measured along the tread surface 20 of the other end E is also represented by a double-headed arrow We1. The total value We of the lengths measured along the tread surface 20 of the pair of end portions E is twice that of We1. The ratio (We / W) between the length We and the length W of the tread surface 20 is preferably 0.10 or more and 0.20 or less. The tire 2 having this ratio of 0.10 or more has a sufficient size of the end E for obtaining a gripping force necessary for full banking. The tire 2 is excellent in grip force at the time of full bank. In this respect, the ratio is more preferably equal to or greater than 0.13. The tire 2 having a ratio (We / W) of 0.20 or less has a size of the intermediate portion M sufficient to realize good wear resistance during turning. The tire 2 is excellent in wear resistance during turning. In this respect, the ratio is more preferably equal to or less than 0.17.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
A tire of Example 1 having the structure shown in FIG. 1 was obtained. The tire size was 190 / 55ZR17. Table 1 shows the specifications of the tire 2. The loss tangent LT1 was 0.23, the loss tangent LT2 was 0.29, and the loss tangent LT3 was 0.34. The hardness H1 was 47, the hardness H2 was 40, and the hardness H3 was 32. The ratio (Wc / W) was 0.2, and the ratio (We / W) was 0.15.

[Comparative Example 1]
A tire of Comparative Example 1 was obtained in which the tread was composed of a single rubber. The tire size was the same as the tire of Example 1. This rubber had a loss tangent of 0.26 and a hardness of 36.

[Comparative Example 2]
A tire of Comparative Example 2 was obtained in the same manner as Example 1 except that the end part was enlarged and the intermediate part was eliminated. The tire tread has a central portion and a large end portion.

[Comparative Example 3]
A tire of Comparative Example 3 was obtained in the same manner as in Example 1 except that the central part was enlarged and the intermediate part was eliminated. The tire tread is composed of a large central portion and an end portion.

[Comparative Example 4]
A tire of Comparative Example 4 was obtained in the same manner as in Example 1 except that the loss tangent LT1 was set to 0.31.

[Comparative Example 5]
A tire of Comparative Example 5 was obtained in the same manner as in Example 1 except that the hardness H1 was set to 36.

[Comparative Example 6]
A tire of Comparative Example 6 was obtained in the same manner as in Example 1 except that the loss tangent LT2 was 0.36.

[Comparative Example 7]
A tire of Comparative Example 7 was obtained in the same manner as in Example 1 except that the hardness H2 was 29.

[Comparative Example 8]
A tire of Comparative Example 8 was obtained in the same manner as in Example 1 except that the loss tangent LT3 was set to 0.26.

[Comparative Example 9]
A tire of Comparative Example 9 was obtained in the same manner as in Example 1 except that the hardness H3 was 43.

[Example 2-9]
A tire of Example 2-9 was obtained in the same manner as in Example 1 except that the loss tangents LT1, LT2, and LT3 were set to the values shown in Tables 3 and 4.

[Example 10-17]
Tires of Examples 10-17 were obtained in the same manner as Example 1 except that the hardnesses H1, H2, and H3 were set to the values shown in Tables 5 and 6.

[Example 18-21]
Tires of Examples 18-21 were obtained in the same manner as Example 1 except that the ratio (Wc / W) was changed to the values shown in Table 7.

[Examples 22-25]
Tires of Examples 22-25 were obtained in the same manner as in Example 1 except that the ratio (We / W) was changed to the values shown in Table 8.

[Abrasion resistance evaluation, grip strength and running stability evaluation]
The prototype tire was mounted on the rear wheel of a motorcycle (4 cycles) with a displacement of 1000 cc and filled with air so that its internal pressure was 250 kPa. The rear wheel rim size was set to MT6.00 × 17. A commercially available tire (size = 120 / 70ZR17) was attached to the front wheel and filled with air so that the internal pressure was 270 kPa. The size of the rim of the front wheel was MT3.50 × 17. This motorcycle was run on a test course whose road surface was asphalt, and sensory evaluation was performed by the rider. Also, the degree of wear of the tread after running was evaluated. Evaluation items at the time of turning are grip force, wear resistance, and running stability. Evaluation items for the full bank are grip strength and running stability. The evaluation items when going straight are running stability and wear resistance. The results are shown in Tables 1-8 below, with the index of Comparative Example 1 being 100. For all the evaluation items, the higher the value, the higher the evaluation.

  As shown in Table 1-8, the tire according to the present invention is highly evaluated in all items of gripping power, wear resistance, and running stability during turning. Moreover, this tire is excellent also in the grip force and driving | running | working stability at the time of a full bank, and driving | running | working stability and abrasion resistance at the time of linear driving | running | working. ADVANTAGE OF THE INVENTION According to this invention, the tire for motorcycles which is excellent in the performance of turning driving | running | working, a full bank driving | running | working, and a straight drive | running | working and excellent in the abrasion resistance of a tread can be provided. From this evaluation result, the superiority of the present invention is clear.

  The tire according to the present invention can be mounted on various motorcycles.

2 ... tyre 4 ... tread 6 ... side wall 8 ... bead 10 ... carcass 10a ... first ply 10b ... second ply 12 ... inner liner 14 ... Belt 14a ... Inner layer 14b ... Outer layer 16 ... Band 18 ... Chafer 20 ... Tread surface 22 ... Core 24 ... Apex 26 ... First rubber 28. .... Second rubber 30 ... Third rubber 32 ... Inner end 34 ... Outer end 36 ... Tread end

Claims (4)

The surface has a tread that forms a tread surface,
This tread has a first rubber, a second rubber and a third rubber,
The tread includes a central portion located at the center, a pair of intermediate portions each positioned outside the central portion in the axial direction, and a pair of end portions positioned respectively outside the intermediate portions in the axial direction.
This central portion has the first rubber,
The intermediate portion has the first rubber, the third rubber laminated on the radially outer side of the first rubber, and the second rubber laminated on the radially outer side of the third rubber,
The end portion has the first rubber and the third rubber laminated on the radially outer side of the first rubber,
The loss tangent LT1 of the first rubber is lower than the loss tangent LT2 of the second rubber, and the loss tangent LT2 is lower than the loss tangent LT3 of the third rubber,
A pneumatic tire for a motorcycle, wherein the hardness H1 of the first rubber is higher than the hardness H2 of the second rubber, and the hardness H2 is higher than the hardness H3 of the third rubber.   The loss tangent LT1 is 0.23 or more and 0.25 or less, the loss tangent LT2 is 0.25 or more and 0.35 or less, and the loss tangent LT3 is 0.28 or more and 0.49 or less. The tire according to 1.   The tire according to claim 1 or 2, wherein the hardness H1 is 37 or more and 55 or less, the hardness H2 is 33 or more and 43 or less, and the hardness H3 is 30 or more and 34 or less.   The ratio (Wc / W) between the length Wc of the central portion measured along the tread surface and the length W of the tread surface is 0.15 or more and 0.30 or less, and along the tread surface. The ratio (We / W) between the total length We of the pair of end portions measured in this way and the length W of the tread surface is 0.10 or more and 0.20 or less. The tire according to any one.

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