JP6013938B2 - Motorcycle tires - 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.

  A centrifugal force acts on a motorcycle when turning. A motorcycle turns by tilting the vehicle body inward as the steering wheel is operated. In a tire of a motorcycle, a cornering force is generated according to the slip angle, and a camber thrust is generated according to the camber angle. At the time of turning, the cornering force and the camber thrust balance with the centrifugal force, and the motorcycle can turn stably.

  A motorcycle tire includes a tread having a small radius of curvature along its axial direction in order to facilitate turning. When traveling straight, the center region located at the center in the axial direction of the tread is grounded. At the time of turning, the shoulder region located on the tread end side is grounded. Considering the respective roles in the center region and the shoulder region, tires employing a divided tread are used. For each region, wear resistance and grip performance are important. Regarding the divided tread, a technique disclosed in Japanese Patent Laid-Open No. 2005-271760 is known.

JP-A-2005-271760

  In a tire employing a divided tread, the crosslinked rubber in each divided region is different from each other. As a result, a difference in wear amount tends to occur between the crosslinked rubbers in the respective regions. For example, if low hardness rubber is disposed in the shoulder region in order to improve the grip performance during turning, there is a problem that the wear resistance is lowered. As a method of suppressing the difference in the amount of wear while selecting a material suitable for the role of each region, a measure is taken to reinforce the tread in the shoulder region with a band, a belt, or the like. However, this method may cause new problems such as a decrease in tire productivity and an increase in cost.

  The present invention has been made in view of the current situation, and an object of the present invention is to provide a motorcycle tire having a tread excellent in wear resistance and grip performance.

The motorcycle tire according to the present invention is:
With a tread,
The tread includes a center region located in the center in the axial direction, and a pair of shoulder regions located outside the center region in the axial direction.
The shoulder region includes a lower layer located on the radially inner side, an upper layer located on the radially outer side, and an intermediate layer located between the lower layer and the upper layer,
The above three layers of the shoulder region are composed of different crosslinked rubbers,
The lower layer and the center region are composed of the same crosslinked rubber,
The magnitude relationship of the loss tangent tan δ of each crosslinked rubber constituting the three layers is the upper layer <intermediate layer and the lower layer <intermediate layer.

  Preferably, the magnitude relation of the loss tangent tan δ of each crosslinked rubber constituting the upper layer and the lower layer is lower layer <upper layer.

  Preferably, the size relationship of the modulus M300 of each crosslinked rubber constituting the upper layer and the intermediate layer is intermediate layer <upper layer.

  Preferably, the magnitude relationship of the hardness of each crosslinked rubber constituting the upper layer and the intermediate layer is intermediate layer <upper layer.

Preferably, in the axial direction, it comprises a pair of intermediate regions located between the center region and the shoulder region,
The intermediate region includes a lower layer located radially inward, an upper layer located radially outward, and an intermediate layer located between the lower layer and the upper layer,
The magnitude relationship of the loss tangent tan δ of each crosslinked rubber constituting the three layers in the intermediate region is upper layer <intermediate layer and lower layer <intermediate layer.

  Preferably, the magnitude relationship of the loss tangent tan δ of each crosslinked rubber constituting the upper layer and the lower layer in the intermediate region is lower layer <upper layer.

  Preferably, the magnitude relationship of the modulus M300 of each crosslinked rubber constituting the upper layer and the intermediate layer in the intermediate region is intermediate layer <upper layer.

  Preferably, the magnitude relationship of the hardness of each crosslinked rubber constituting the upper layer and the intermediate layer in the intermediate region is intermediate layer <upper layer.

  Preferably, the magnitude relationship of the loss tangent tan δ between the crosslinked rubber constituting the upper layer of the shoulder region and the crosslinked rubber constituting the upper layer of the intermediate region is intermediate region <shoulder region.

  Preferably, the magnitude relationship of the loss tangent tan δ between the crosslinked rubber constituting the intermediate layer of the shoulder region and the crosslinked rubber constituting the intermediate layer of the intermediate region is intermediate region <shoulder region.

  Preferably, the size relationship of the modulus M300 between the crosslinked rubber constituting the upper layer of the shoulder region and the crosslinked rubber constituting the upper layer of the intermediate region is shoulder region <intermediate region.

  Preferably, the size relationship of the modulus M300 between the crosslinked rubber constituting the intermediate layer of the shoulder region and the crosslinked rubber constituting the intermediate layer of the intermediate region is shoulder region <intermediate region.

  In the tire according to the present invention, the three layers of the cross-linked rubber constituting each of the center region and the shoulder region of the tread are configured in accordance with each role. This tire is excellent in wear resistance and grip performance while being a tire having different materials from the center region to the shoulder region.

FIG. 1 is a cross-sectional view showing a part of a motorcycle tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a part of a motorcycle tire according to another embodiment of the present invention.

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

  In FIG. 1, the vertical direction is the tire radial direction (hereinafter also simply referred to as the radial direction), and the horizontal direction is the tire axial direction (hereinafter also simply referred to as the axial direction). The tire 2 has a substantially bilaterally symmetrical shape with respect to a center line CL indicated by a one-dot chain line. This center line CL represents the equator plane EQ. The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a belt 12, a band 13, an inner liner 14, and a chafer 16. The tire 2 is a tubeless type pneumatic tire. The tire 2 is attached to the rear wheel of the motorcycle. The tire 2 is a rear tire.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 18 that contacts the road surface. The tread 4 includes a center region 20 located in the center along the axial direction, and a pair of shoulder regions 22 located on both outer sides of the center region 20. Center region 20 includes an equatorial plane EQ. The shoulder region 22 is a pair of regions that are symmetrical with respect to the equator plane EQ.

  In the present embodiment, the width of the center region 20 is about 15% or more and about 30% or less of 1/2 of the tread width TW, and the width of the shoulder region 22 is tread on one side on the left and right sides of the center line CL of the cross section of the tire 2. It is about 70% or more and about 85% or less of ½ of the width TW. Each of the above widths including the tread width TW is not a width seen in the tire radial direction, but a width exhibiting an arc shape along the tread surface 18 in the axial direction as shown in FIG. It can be said that all of the above widths are the widths seen in the radius direction of curvature of the tread.

  The shoulder region 22 includes three layers 22A, 22B, and 22C that are stacked in the radial direction. The shoulder region 22 includes a shoulder lower layer (hereinafter also simply referred to as a lower layer) 22A, a shoulder intermediate layer (hereinafter also simply referred to as an intermediate layer) 22B, and a shoulder upper layer (hereinafter also simply referred to as an upper layer) 22C. . The lower layer 22A is located on the radially inner side. The upper layer 22C is located on the radially outer side. The intermediate layer 22B is located between the lower layer 22A and the upper layer 22C.

  The tread 4 is formed from a crosslinked rubber composition (crosslinked rubber). The center region 20 and the shoulder lower layer 22A are both formed from a first crosslinked rubber. The center region 20 and the shoulder lower layer 22A are continuously formed from the same first crosslinked rubber. The shoulder intermediate layer 22B is formed from a second crosslinked rubber. The shoulder upper layer 22C is formed of a third crosslinked rubber.

  The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The sidewall 6 is made of a crosslinked rubber composition. The sidewall 6 absorbs an impact from the road surface by bending. Furthermore, 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 24 and an apex 26 that extends radially outward from the core 24. The apex 26 is tapered outward in the radial direction. The apex 26 is made of a crosslinked rubber composition. The apex 26 has a high hardness.

  The carcass 10 includes a first carcass ply 28 and a second carcass ply 29. The first carcass ply 28 is bridged between the two beads 8 and extends along the tread 4 and the sidewall 6. The first carcass ply 28 is folded around the core 24 from the inner side to the outer side in the axial direction. The second carcass ply 29 extends to the lower part of the sidewall 6 along the tread 4 and the sidewall 6. The end of the folded portion of the first carcass ply 28 is located outside the end of the second carcass ply 29 in the radial direction.

  Although not shown, each carcass ply 28, 29 is made of a cord and a topping rubber. The absolute value of the angle formed by the cord with respect to the equator plane CL is 65 ° to 90 °. In other words, the tire 2 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 belt 12 is located between the carcass 10 and the tread 4. The belt 12 is laminated with the carcass 10. The belt 12 reinforces the carcass 10. In the present embodiment, the belt 12 includes a first layer 12a and a second layer 12b in order from the radially inner side. Although not shown, the belt 12 includes a large number of cords arranged in parallel and a topping rubber. Each cord can be formed from steel. An organic fiber may be used for the cord. This cord is inclined with respect to the equator plane EQ. The belt layer is not limited to two layers, and may be a single layer or three or more layers.

  The band 13 is located on the radially outer side of the second layer 12 b of the belt 12. In the axial direction, the width of the band 13 is larger than the width of the second layer 12 b of the belt 12. Although not shown, the band 13 is composed of a cord and a topping rubber. The cord is wound in a spiral. The band 13 has a so-called jointless structure. The cord extends substantially in the circumferential direction. Since the belt 12 is restrained by this cord, lifting of the belt 12 is suppressed. The cord is made of organic fiber.

  The inner liner 14 is joined to the inner peripheral surface of the carcass 10. The inner liner 14 is made of a crosslinked rubber. The inner liner 14 is made of rubber having excellent air shielding properties. The inner liner 14 plays a role of maintaining the internal pressure of the tire 2.

  Below, the physical property of the 1st crosslinked rubber of the tread 4 mentioned above, the 2nd crosslinked rubber, and the 3rd crosslinked rubber is demonstrated. In the present tire 2, the loss tangent tan δ of the second crosslinked rubber is set larger than the loss tangent tan δ of the first crosslinked rubber and the third crosslinked rubber. Therefore, the magnitude relationship (high / low relationship) of the loss tangent tan δ of the three layers constituting the shoulder region 22 is as follows. Upper layer 22C <intermediate layer 22B, and lower layer 22A <intermediate layer 22B.

  A crosslinked rubber having a large loss tangent tan δ has a large hysteresis loss. A tire provided with a tread made of this crosslinked rubber has an increased grip limit and excellent grip performance. This tire is excellent in turning performance. However, in this tire, the heat resistance is lowered.

  A crosslinked rubber having a small loss tangent tan δ has a small hysteresis loss. This cross-linked rubber has low exothermic properties and prevents excessive temperature rise. A tire provided with a tread made of this crosslinked rubber contributes to blow resistance. This tire is excellent in abrasion wear resistance. However, with this tire, the grip limit is reduced.

  As described above, in the tire 2, the center region 20 is made of the first crosslinked rubber having a low tan δ. When the motorcycle goes straight, the center region 20 of the tire 2 is mainly grounded. The low tan δ center region 20 contributes to improvement in fuel consumption, straight running stability, and wear resistance.

  Further, in the tire 2, the shoulder intermediate layer 22B is made of a second crosslinked rubber having a high tan δ. When the motorcycle turns, the shoulder region 22 of the tire 2 is mainly grounded. The tire 2 has excellent grip performance and improves turning performance. The shoulder upper layer 22C, which has a great influence on the wear resistance of the tire, is composed of a low tan δ third crosslinked rubber. The tire 2 has high abrasion wear resistance. The tire 2 is excellent in heat resistance (high-speed durability). The shoulder lower layer 22A is made of a low modulus first crosslinked rubber. This lower layer 22A has a low hysteresis loss. As a result, the blow resistance, heat resistance and adhesion are improved.

  From this viewpoint, in the shoulder region 22, the ratio of tan δ of the upper layer (third crosslinked rubber) 22C to tan δ of the intermediate layer (second crosslinked rubber) 22B is preferably 80% or more and less than 100%. Further, the ratio of tan δ of the lower layer (first crosslinked rubber) 22A to tan δ of the intermediate layer (second crosslinked rubber) 22B is preferably 50% or more and 95% or less. In the shoulder region 22, the tan δ of the lower layer (first crosslinked rubber) 22A is preferably 0.20 or more and 0.55 or less. The tan δ of the intermediate layer (second crosslinked rubber) 22B is preferably 0.30 or more and 0.60 or less. The tan δ of the upper layer (third crosslinked rubber) 22C is preferably 0.25 or more and less than 0.60.

  The loss tangent tan δ is preferably lower layer 22A <upper layer 22C. That is, it is preferable that the loss tangent tan δ of the third crosslinked rubber is larger than the loss tangent tan δ of the first crosslinked rubber. Comparing the loss tangent tan δ of the entire three layers 22A, 22B, and 22C of the shoulder region 22, it is preferable that the lower layer 22A <the upper layer 22C <the intermediate layer 22B. This is because the blow is suppressed in the lower layer 22A having a low loss tangent tan δ and the grip performance is improved in the intermediate layer 22B having a high loss tangent tan δ. From this viewpoint, the ratio of tan δ of the upper layer (third crosslinked rubber) 22C to tan δ of the lower layer (first crosslinked rubber) 22A is preferably 110% or more and 150% or less.

Here, the loss tangent tan δ is measured by a viscoelastic spectrometer (trade name “VA-200”, manufactured by Shimadzu Corporation) under the conditions shown below in accordance with the provisions of “JIS-K 6394”. .
Initial strain: 10%
Amplitude: ± 2%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70 ° C

  In the tire 2, it is preferable that the 300% modulus M300 of the third crosslinked rubber (hereinafter simply referred to as modulus, M300 or modulus M300) is larger than the modulus M300 of the second crosslinked rubber. That is, it is preferable that the size relationship (height relationship) of the modulus M300 of the crosslinked rubber is: shoulder intermediate layer 22B <shoulder upper layer 22C.

  A rubber having a large modulus M300 is excellent in abrasion wear resistance. A tire provided with a tread made of this crosslinked rubber is excellent in wear appearance (wear skin). Moreover, this tire is excellent in heat resistance (high-speed durability). A rubber having a small modulus M300 has reduced abrasion resistance. Abrasive wear is wear that occurs when a hard and sharp protrusion scratches the rubber surface, and an ablation pattern in a direction perpendicular to the slip direction is generated.

  As described above, in the tire 2, the shoulder upper layer 22 </ b> C that has a large influence on the wear resistance is formed of the high-modulus third crosslinked rubber. The tire 2 has high abrasion wear resistance. From this viewpoint, the ratio of M300 of the intermediate layer (second crosslinked rubber) 22B to M300 of the upper layer (third crosslinked rubber) 22A is preferably 80% or more and less than 100%. In the shoulder region 22, the M300 of the intermediate layer (second crosslinked rubber) 22B is preferably 4.0 MPa or more and less than 8.0 MPa. The M300 of the upper layer (third crosslinked rubber) 22C is preferably 5.0 MPa or more and 8.0 MPa or less.

  Here, the 300% modulus M300 is a tensile stress measured when the rubber is stretched 300% under the condition of 30 ° C. in accordance with the provisions of “JIS-K 6301”.

  In the tire 2, the rubber hardness of the third crosslinked rubber is preferably larger than the hardness of the second crosslinked rubber. That is, regarding the hardness relationship of the crosslinked rubber (larger or smaller relationship), it is preferable that shoulder intermediate layer 22B <shoulder upper layer 22C. The reason for this is as follows.

  High hardness rubber is excellent in wear resistance. A tire provided with a tread made of this crosslinked rubber has a small amount of wear and can be expected to have an extended life (improvement of wear life). Furthermore, this tire is excellent in blow resistance. This tire is excellent in straight running stability. On the other hand, rubber with low hardness is excellent in grip performance. From this viewpoint, the ratio of the hardness of the intermediate layer (second crosslinked rubber) 22B to the hardness of the upper layer (third crosslinked rubber) 22C is preferably 70% or more and less than 100%. In the shoulder region 22, the hardness of the intermediate layer (second crosslinked rubber) 22B is preferably 35 or more and less than 70. The hardness of the upper layer (third crosslinked rubber) 22C is preferably 50 or greater and 70 or less.

  The blow refers to breakage of rubber splattered due to boiling of rubber of the tire. As the blow resistance is higher, such breakage can be suppressed.

  Here, the rubber hardness is measured by pressing a type A durometer against the tire 2 under a condition of 23 ° C. in accordance with the provisions of “JIS-K 6253”.

  Although not shown, in the manufacturing process of the tire 2, the inner liner 14 and the carcass ply 28 are sequentially wound around the former. On the carcass ply 28, a ribbon made of a cord and a topping rubber is spirally wound. The ribbon forms a belt ply having a jointless structure. The ribbon extends substantially in the circumferential direction.

  A first strip made of uncrosslinked rubber is spirally wound on the belt ply. The first strip extends substantially in the circumferential direction. The first strips are laminated sequentially. When the first strip is wound, a second strip made of uncrosslinked rubber is wound continuously with the first strip. The second strip extends substantially in the circumferential direction. The second strip is sequentially laminated. When the second strip has been wound, the third strip is continuously wound around the second strip. A green tire is thus obtained. The winding method from the first strip to the third strip, the winding order of each strip, and the winding thickness can be appropriately adjusted depending on the configuration of the tread.

  The green tire is put into a mold and is pressurized and heated. A cross-linking reaction occurs in the rubber by heating, and the tire 2 is obtained. A first crosslinked rubber is obtained from the first strip. A second crosslinked rubber is obtained from the second strip. A third crosslinked rubber is obtained from the third strip. In the tire 2, since three types of strips are used and wound sequentially, the center region 20 and the shoulder lower layer 22A are easily formed. The shoulder intermediate layer 22B and the shoulder upper layer 22C are easily formed. The tread 4 is easily manufactured by a strip wind method.

  FIG. 2 shows a tire 32 according to another embodiment. Here, the configuration of the tread 34 different from that of the tire 2 of FIG. 1 will be mainly described. The same members are denoted by the same reference numerals as in FIG. 1 and the description thereof is omitted.

  The tread 34 of the tire 32 has a shape protruding outward in the radial direction. The tread 34 includes, in the axial direction, a center region 20 located in the center, a pair of intermediate regions 36 located on both outer sides of the center region 20, and a pair of shoulders located on both outer sides of the intermediate regions 36. Region 38. Center region 20 includes an equatorial plane EQ. The intermediate region 36 and the shoulder region 38 are a pair of regions that are symmetric with respect to the equator plane EQ.

  In the present embodiment, on one side on the left and right sides of the center line CL of the cross section of the tire 32, the width of the center region 20 is about 5% to 40% of 1/2 of the tread width TW, and the width of the intermediate region 36 is tread width. The width of the shoulder region 38 is about 5% to 40% of 1/2 of the tread width TW. Each of the above widths is not a width seen in the tire radial direction, but a width exhibiting an arc shape along the tread surface 18 in the axial direction as shown in FIG. It can be said that all of the above widths are the widths seen in the radius direction of curvature of the tread.

  The intermediate region 36 includes three layers 36A, 36B, and 36C that are stacked in the radial direction. The intermediate region 36 includes an intermediate region lower layer (hereinafter also simply referred to as a lower layer) 36A, an intermediate region intermediate layer (hereinafter also simply referred to as an intermediate layer) 36B, and an intermediate region upper layer (hereinafter also simply referred to as an upper layer) 36C. I have. The lower layer 36A is located on the radially inner side. The upper layer 36C is located on the radially outer side. The intermediate layer 36B is located between the lower layer 36A and the upper layer 36C.

  The shoulder region 38 includes three layers 38A, 38B, and 38C that are stacked in the radial direction. The shoulder region 38 includes a shoulder lower layer (hereinafter also simply referred to as a lower layer) 38A, a shoulder intermediate layer (hereinafter also simply referred to as an intermediate layer) 38B, and a shoulder upper layer (hereinafter also referred to simply as an upper layer) 38C. . The lower layer 38A is located on the radially inner side. The upper layer 38C is located on the radially outer side. The intermediate layer 38B is located between the lower layer 38A and the upper layer 38C.

  The tread 34 is formed from a crosslinked rubber composition (crosslinked rubber). The center region 20, the intermediate region lower layer 36A, and the shoulder lower layer 38A are all formed from the first crosslinked rubber described above. The center region 20, the intermediate region lower layer 36A, and the shoulder lower layer 38A are continuously formed from the same first crosslinked rubber. The shoulder intermediate layer 38B is formed from the second crosslinked rubber described above. The shoulder upper layer 38C is formed from the above-described third crosslinked rubber. The intermediate region intermediate layer 36B is formed from a fourth crosslinked rubber. The middle region upper layer 36C is formed of a fifth crosslinked rubber.

  Below, the physical property of the 4th crosslinked rubber of the tread 34 mentioned above and the 5th crosslinked rubber is demonstrated. The physical properties of the first crosslinked rubber, the second crosslinked rubber and the third crosslinked rubber have already been explained. That is, the physical properties of the three layers 38A, 38B, and 38C of the shoulder region 38 of the tire 32 are the same as those of the three layers 22A, 22B, and 22C of the shoulder region 22 of the tire 2 of FIG. The center region 20 has already been described. Therefore, detailed description is omitted. Also in the shoulder region 38 of the tire 32, the same function and effect as those in the shoulder region 22 of the tire 2 described above can be achieved.

  In the tire 32, the loss tangent tan δ of the fourth crosslinked rubber is larger than the loss tangent tan δ of the first crosslinked rubber and the fifth crosslinked rubber. Therefore, the magnitude relationship (high / low relationship) of the loss tangent tan δ of the three layers constituting the intermediate region 36 is as follows. The upper layer 36C <the intermediate layer 36B and the lower layer 36A <the intermediate layer 36B.

  In the intermediate region 36, the ratio of tan δ of the upper layer (fifth crosslinked rubber) 36C to tan δ of the intermediate layer (fourth crosslinked rubber) 36B is preferably 70% or more and less than 100%. The ratio of tan δ of the lower layer (first crosslinked rubber) 36A to tan δ of the intermediate layer (fourth crosslinked rubber) 36B is preferably 60% or more and 90% or less. In the intermediate region 36, the tan δ of the lower layer (first crosslinked rubber) 36A is preferably 0.20 or more and 0.55 or less. The tan δ of the intermediate layer (fourth crosslinked rubber) 36B is preferably 0.30 or more and 0.60 or less. The tan δ of the upper layer (fifth crosslinked rubber) 36C is preferably 0.25 or more and less than 0.60.

  In the tire 32, the modulus M300 of the fifth crosslinked rubber is preferably larger than the modulus M300 of the fourth crosslinked rubber. That is, for the cross-linked rubber M300, it is preferable that the intermediate region intermediate layer 36B <the intermediate region upper layer 36C. The ratio of M300 of the intermediate layer (fourth crosslinked rubber) 36B to M300 of the upper layer (fifth crosslinked rubber) 36C is preferably 70% or more and less than 100%. In the intermediate region 36, the M300 of the intermediate layer (fourth crosslinked rubber) 36B is preferably 4.0 MPa or more and less than 7.0 MPa. M300 of the upper layer (fifth crosslinked rubber) 36C is preferably 4.5 MPa or more and 7.0 MPa or less.

  In the tire 32, the rubber hardness of the fifth crosslinked rubber is preferably larger than the hardness of the fourth crosslinked rubber. That is, with respect to the hardness of the crosslinked rubber, it is preferable that the intermediate region intermediate layer 36B <the intermediate region upper layer 36C. The ratio of the hardness of the intermediate layer (fourth crosslinked rubber) 36B to the hardness of the upper layer (fifth crosslinked rubber) 36C is preferably 70% or more and less than 100%.

  Due to the rubber configuration of the upper, middle, and lower layers 36A, 36B, and 36C of the intermediate region 36 described above, also in the intermediate region 36 of the tire 32, the same functions and effects as those in the shoulder region 22 of the tire 2 described above are obtained. Can be played.

  The loss tangent tan δ preferably satisfies the intermediate region lower layer 36A <intermediate region upper layer 36C. That is, it is preferable that the loss tangent tan δ of the fifth crosslinked rubber is larger than the loss tangent tan δ of the first crosslinked rubber. Comparing the loss tangent tan δ of the entire three layers 36A, 36B, 36C of the intermediate region 36, the lower layer 36A <the upper layer 36C <the intermediate layer 36B. This is because the blow is suppressed in the lower layer 36A having a low loss tangent tan δ and the grip performance is improved in the intermediate layer 36B having a high loss tangent tan δ. From this viewpoint, the ratio of tan δ of the upper layer (fifth crosslinked rubber) 36C to tan δ of the lower layer (first crosslinked rubber) 36A is preferably 110% or more and 150% or less.

  Next, it is preferable that the intermediate region 36 and the shoulder region 38 of the tire 32 have the following physical property relationship.

  First, the magnitude relationship of the loss tangent tan δ between the third crosslinked rubber constituting the shoulder upper layer 38C and the fifth crosslinked rubber constituting the intermediate region upper layer 36C is intermediate region 36 <shoulder region 38. The magnitude relationship of the loss tangent tan δ between the second crosslinked rubber constituting the shoulder intermediate layer 38B and the fourth crosslinked rubber constituting the intermediate region intermediate layer 36B is intermediate region 36 <shoulder region 38.

  The size relationship of the modulus M300 between the third crosslinked rubber constituting the shoulder upper layer 38C and the fifth crosslinked rubber constituting the intermediate region upper layer 36C is such that the shoulder region 38 <the intermediate region 36. The size relationship of the modulus M300 between the second crosslinked rubber constituting the shoulder intermediate layer 38B and the fourth crosslinked rubber constituting the intermediate region intermediate layer 36B is shoulder region 38 <intermediate region 36.

  The magnitude relationship of the hardness of the third crosslinked rubber constituting the shoulder upper layer 38C and the fifth crosslinked rubber constituting the intermediate region upper layer 36C is shoulder region 38 <intermediate region 36. Further, the magnitude relation of the hardness of the second crosslinked rubber constituting the shoulder intermediate layer 38B and the fourth crosslinked rubber constituting the intermediate region intermediate layer 36B is shoulder region 38 <intermediate region 36.

  As described above, when the upper layer 36C and the intermediate layer 36B of the intermediate region 36 are compared with the upper layer 38C and the intermediate layer 38B of the shoulder region 38, the loss tangent tan δ is larger in the shoulder region 38, and the modulus M300 is The intermediate region 36 is made larger. As a result, high grip performance can be obtained by the shoulder region 38 when the motorcycle turns. Then, when the motorcycle enters the acceleration phase later in its turn, it raises the car body slightly. At this time, in the middle region 36 of the tire that is in contact with the ground, the friction from the ground is greater with respect to the shoulder region during turning. However, since the modulus M300 is increased in the intermediate region 36 as described above, wear is suppressed. The tire 32 is excellent in transient characteristics at the time of transition between turning and straight traveling.

  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]
As Example 1, a test tire shown in FIG. 1 in which the tread rubber was divided into a center region and a shoulder region was manufactured. The tire of Example 1 does not have a tread middle region. The shoulder region includes three layers in the radial direction: a lower layer, an intermediate layer, and an upper layer. The size of the test tire is 190 / 50ZR17. The internal pressure of the test tire is 250 kPa. The physical properties (loss tangent tan δ, modulus M300, rubber hardness) of each region and each layer in the tire tread are shown as indices in Table 1. This index is obtained by setting the physical property value of the tread rubber of Comparative Example 1 to 100, and will be described later. What is indicated by a mark “-” in the table indicates that the physical property is not measured. A tread performance test described later was performed on the tire. The evaluation results of the test are as described in Table 1. A mark “-” in the table indicates that the test is not performed.

[Example 2-11]
As Examples 2 to 11, test tires shown in FIG. 1 in which tread rubber was divided into a center region and a shoulder region were manufactured. The physical properties (loss tangent tan δ, modulus M300, rubber hardness) of each region and each layer in the tread of these tires are as described in Tables 1 and 2. Regarding Examples 2 to 11, the tire configuration and rubber properties other than those described above are the same as in Example 1. A tread performance test described later was performed on the tire. The test evaluation results are as described in Tables 1 and 2.

[Comparative Example 1]
As Comparative Example 1, a test tire in which the tread rubber was integrally formed from a single rubber without being divided into any region and any layer was manufactured. The physical properties (loss tangent tan δ, modulus M300, rubber hardness) of the tread rubber of this tire are shown as an index in Table 1. The index 100 represents 0.32 for the loss tangent tan δ, 6.0 MPa for the modulus M300, and 60 for the rubber hardness. Regarding Comparative Example 1, the tire configuration and rubber properties other than those described above are the same as in Example 1. A tread performance test described later was performed on the tire. The evaluation results of the test are as described in Table 1.

[Comparative Example 2-5]
As Comparative Examples 2 to 5, test tires shown in FIG. 1 in which the tread rubber was divided into a center region and a shoulder region were manufactured. The physical properties (loss tangent tan δ, modulus M300, rubber hardness) of each region and each layer in the tread of these tires are as described in Tables 1 and 2. Regarding Comparative Examples 2 to 5, the tire configuration and rubber properties other than those described above are the same as in Example 1. A tread performance test described later was performed on the tire. The test evaluation results are as described in Tables 1 and 2.

[Examples 12-23]
As Examples 12 to 23, test tires shown in FIG. 2 in which the tread was divided into a center region, an intermediate region, and a shoulder region were manufactured. Each of the shoulder region and the intermediate region has three layers of a lower layer, an intermediate layer, and an upper layer in the radial direction. The physical properties (loss tangent tan δ, modulus M300, rubber hardness) of each region and each layer in the tire tread are as described in Tables 3 and 4. Regarding Examples 12 to 23, the tire configuration and rubber properties other than those described above are the same as in Example 1. A tread performance test described later was performed on these tires. The test evaluation results are as described in Tables 3 and 4.

[Comparative Examples 6 and 7]
As Comparative Examples 6 and 7, test tires shown in FIG. 2 in which the tread was divided into a center region, an intermediate region, and a shoulder region were manufactured. Each of the shoulder region and the intermediate region has three layers of a lower layer, an intermediate layer, and an upper layer in the radial direction. The physical properties (loss tangent tan δ, modulus M300, rubber hardness) of each region and each layer in the tread of these tires are as described in Table 4. For Comparative Examples 6 and 7, the tire configuration and rubber properties other than those described above are the same as in Example 12. A tread performance test described later was performed on these tires. The evaluation results of the test are as described in Table 4.

[Tread performance test]
The test tire was mounted on the rear wheel of a 1000 cc motorcycle that was a test vehicle. Conventional tires were mounted on the front wheels. This test vehicle ran on the circuit course. Through this running test, the test tires were evaluated for dry grip performance, abrasive wear resistance (wear appearance), wear resistance (wear life), and blow resistance.

  Regarding dry grip performance, sensory evaluation was performed by the driver after driving on the dry road surface. Evaluation is represented by the index which set the evaluation result of the comparative example 1 as a reference | standard to 100. FIG. The higher the number, the higher the evaluation.

  With respect to the abrasive wear resistance (wear appearance) performance, the surface of the test tire was visually inspected after the test vehicle traveled 10 laps on the circuit course. The abrasive wear resistance was quantitatively evaluated by measuring the pitch of the abrasive wear scratches. Evaluation is represented by the index which set the evaluation result of the comparative example 1 as a reference | standard to 100. FIG. The higher the number, the higher the evaluation.

  Regarding the wear resistance (wear life) performance, the amount of wear of the test tire was measured after the test vehicle traveled 10 laps on the circuit course. The reciprocal of this amount of wear was calculated and an index was assigned. Evaluation is represented by the index which set the evaluation result of the comparative example 1 as a reference | standard to 100. FIG. The higher the number, the higher the evaluation.

  With respect to the blow resistance, a test on a test tire was performed by a bench test apparatus equipped with a tire driving drum. The index indicating the blow resistant performance was given to the time from the start of running to the occurrence of blow. The longer this time, the better the blow resistance. It is represented by an index with the evaluation result of Comparative Example 1 as a reference being 100. The higher the number, the higher the evaluation.

[Evaluation of test results]
The tires of the examples are highly evaluated for the various performances described above compared to the tires of the comparative examples. 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, 32 ... Tire 4, 34 ... Tread
6 ... sidewall
8 ... Bead 10 ... Carcass 12 ... Belt 13 ... Band 14 ... Inner liner 16 ... Chafer 18 ... Tread surface 20 ... Center region 22, 38 ... Shoulder region 24 ... Core 26 ... Apex 28 ... First carcass ply 29 ... Second carcass ply 36 ... Intermediate region CL ... Center line of tire cross section EQ ... Equatorial plane (of tire) TW ... Tread width (along tread surface)

Claims (12)

With a tread,
The tread includes a center region located in the center in the axial direction, and a pair of shoulder regions located outside the center region in the axial direction.
The shoulder region includes a lower layer located on the radially inner side, an upper layer located on the radially outer side, and an intermediate layer located between the lower layer and the upper layer,
The above three layers of the shoulder region are composed of different crosslinked rubbers,
The lower layer and the center region are composed of the same crosslinked rubber,
A motorcycle tire in which the magnitude relationship of the loss tangent tan δ of each crosslinked rubber constituting the three layers is an upper layer <an intermediate layer and a lower layer <an intermediate layer.   The motorcycle tire according to claim 1, wherein a magnitude relationship of loss tangent tan δ of each crosslinked rubber constituting the upper layer and the lower layer is lower layer <upper layer.   The motorcycle tire according to claim 1 or 2, wherein the size relationship of the modulus M300 of each crosslinked rubber constituting the upper layer and the intermediate layer is intermediate layer <upper layer.   The tire for a motorcycle according to any one of claims 1 to 3, wherein the hardness relationship of the respective crosslinked rubbers constituting the upper layer and the intermediate layer is intermediate layer <upper layer. In the axial direction, it comprises a pair of intermediate regions located between the center region and the shoulder region,
The intermediate region includes a lower layer located radially inward, an upper layer located radially outward, and an intermediate layer located between the lower layer and the upper layer,
5. The automatic relationship according to claim 1, wherein the magnitude relationship of the loss tangent tan δ of each crosslinked rubber constituting the three layers in the intermediate region is an upper layer <intermediate layer and a lower layer <intermediate layer. Tires for motorcycles.   The motorcycle tire according to claim 5, wherein a magnitude relationship of loss tangent tan δ of each crosslinked rubber constituting the upper layer and the lower layer in the intermediate region is lower layer <upper layer.   The motorcycle tire according to claim 5 or 6, wherein the size relationship of the modulus M300 of each crosslinked rubber constituting the upper layer and the intermediate layer in the intermediate region is intermediate layer <upper layer.   The motorcycle tire according to any one of claims 5 to 7, wherein the hardness relationship between the upper layer and the crosslinked rubber constituting the intermediate layer in the intermediate region is intermediate layer <upper layer.   The magnitude relationship of the loss tangent tan δ between the crosslinked rubber constituting the upper layer of the shoulder region and the crosslinked rubber constituting the upper layer of the intermediate region is intermediate region <shoulder region. The motorcycle tire described.   The magnitude relationship of the loss tangent tan δ between the crosslinked rubber constituting the intermediate layer of the shoulder region and the crosslinked rubber constituting the intermediate layer of the intermediate region is intermediate region <shoulder region. The motorcycle tire described.   The motorcycle according to any one of claims 5 to 10, wherein the size relationship of the modulus M300 between the crosslinked rubber constituting the upper layer of the shoulder region and the crosslinked rubber constituting the upper layer of the intermediate region is shoulder region <intermediate region. Tires.   The size relationship of the modulus M300 between the crosslinked rubber constituting the intermediate layer of the shoulder region and the crosslinked rubber constituting the intermediate layer of the intermediate region is shoulder region <intermediate region. Motorcycle tires.

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