JP2015160480A - Pneumatic tire for two-wheeled automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for a two-wheeled automobile having excellent turning performance and absorptivity without spoiling productivity.SOLUTION: This tire 2 includes a tread 4, a pair of side walls 6, a pair of beads 8 and a carcass 10. The bead 8 includes a core 24 and an apex 26 which extends in a radial outer direction. A tip 36b of the apex 26 is positioned near an end 22 of the tread 4. The apex 26 includes: an inner layer 32a; a middle layer 32b which is positioned outside the inner lyer 32a in an axial direction; and an outer layer 32c which is positioned outside the middle layer 32b in the axial direction. A width of the middle layer 32b is equal to or more than 1 mm. A hardness of the middle layer 32b is equal to or more than 70. The hardness of the middle layer 32b is larger than that of the inner layer 32a and the outer layer 32c.

Description

  The present invention relates to a pneumatic tire for a motorcycle.

  The pneumatic tire includes a tread, a sidewall, and a bead. The outer surface of the tread is a tread surface. The tire contacts the tread surface. The sidewall extends radially inward from the end of the tread. In the tire, the side wall portion is bent. The bead is located substantially radially inward of the sidewall. In the tire, this bead portion is fitted to the rim.

  The bead includes a core and an apex. The core is made of a non-stretchable wire. The apex extends radially outward from the core. The apex tapers radially outward. Apex is made of a crosslinked rubber.

  Apex having high hardness may be employed. This apex can contribute to rigidity. This tire is excellent in turning performance.

  An apex having an elongated shape may be employed. In this tire, the deflection of the sidewall portion is not unique. Since this part is bent appropriately, this tire is excellent in absorbency.

  Thus, the configuration of the apex affects the turning performance and absorbability of the tire. Various studies have been made on the structure of the apex from the viewpoint of achieving both turning performance and absorbability. Examples of this study are disclosed in JP2003-291613A, JP2007-099152A, and JP2007-290443A.

JP 2003-291613 A JP 2007-099152 A JP 2007-290443 A

  A thin and hard apex may be employed from the viewpoint of both turning performance and absorbability. In this case, the apex may curl during formation, and the tire may not be manufactured stably. This apex inhibits productivity. From the viewpoint of curling prevention, when the width of the apex is increased, the rigidity becomes excessive and the absorbability is lowered.

  An object of the present invention is to provide a pneumatic tire for a two-wheeled vehicle that is excellent in turning performance and absorbability without impairing productivity.

  The pneumatic tire for a motorcycle according to the present invention includes a tread whose outer surface forms a tread surface, a pair of sidewalls that extend substantially inward in the radial direction from the end of the tread, and each of which is more radial than the sidewall. A pair of beads positioned substantially inside, and a carcass spanned between one bead and the other bead along the inside of the tread and the sidewall. The bead includes a core and an apex extending radially outward from the core. The tip of the apex is located in the vicinity of the end of the tread. The apex includes an inner layer, a middle layer positioned outside the inner layer in the axial direction, and an outer layer positioned further outside the middle layer in the axial direction. The width of this middle layer is 1 mm or more and 3 mm or less. The hardness of this middle layer is 70 or more and 85 or less. The hardness of the middle layer is higher than the hardness of the inner layer and the outer layer.

  Preferably, in the pneumatic tire for a motorcycle, a radial distance from the tip of the apex to the end of the tread is 5 mm or less.

  Preferably, in the pneumatic tire for a motorcycle, the outer end of the middle layer is a tip of the apex.

  Preferably, in the pneumatic tire for a motorcycle, the hardness of the inner layer is 60 or less. The outer layer has a hardness of 60 or less.

  Preferably, the pneumatic tire for a two-wheeled vehicle is for a front wheel.

  In the pneumatic tire for a motorcycle according to the present invention, the middle layer that forms part of the apex is thin and hard. This middle layer can contribute to turning performance and absorbability. In addition, since the inner layer and the outer layer can contribute to maintaining the apex shape, curling of the apex during formation is prevented in this tire. This tire can be manufactured stably. According to the present invention, a tire in which both turning performance and absorbency are achieved can be obtained without impairing productivity.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional perspective view showing a bead forming a part of the tire of FIG. 1.

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

  The tire 2 shown in FIG. 1 exhibits a substantially bilaterally symmetric shape centered on a one-dot chain line CL in the drawing. This alternate long and short dash line CL represents the equator plane of the tire 2. In FIG. 1, the vertical direction is the radial direction, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction.

  The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a belt 12, a band 14, an inner liner 16, and a chafer 18. The tire 2 is a tubeless type. The tire 2 is attached to a two-wheeled vehicle. More specifically, the tire 2 is attached to the front wheel of a two-wheeled vehicle. In other words, the tire 2 is for a front wheel of a two-wheeled vehicle.

  The tread 4 is made of a crosslinked rubber having excellent wear resistance. The tread 4 has a shape protruding outward in the radial direction. The tread 4 includes a tread surface 20. The tire 2 is grounded on the tread surface 20. The tread surface 20 has no groove. Grooves may be cut into the tread surface 20 to form a tread pattern.

  The sidewall 6 extends substantially inward in the radial direction from the end 22 of the tread 4. The sidewall 6 is made of a crosslinked rubber. 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 is located substantially inward of the sidewall 6 in the radial direction. The bead 8 includes a core 24 and an apex 26 that extends radially outward from the core 24. The core 24 has a ring shape. The core 24 is formed by winding a non-stretchable wire. Typically, a steel wire is used for the core 24. The apex 26 is tapered outward in the radial direction. The apex 26 is made of a crosslinked rubber.

  The carcass 10 includes a carcass ply 28. The carcass ply 28 is bridged between the beads 8 on both sides, and extends along the inside of the tread 4 and the sidewall 6. The carcass ply 28 is folded around the core 24 from the inner side to the outer side in the axial direction. The carcass 10 may be composed of two or more carcass plies 28.

  Although not shown, the carcass ply 28 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 usually 65 ° to 90 °. In other words, the carcass 10 has a radial structure. The cord is usually made of organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The belt 12 is located on the radially outer side of the carcass 10. The belt 12 is laminated with the carcass 10. The belt 12 reinforces the carcass 10. The belt 12 includes a belt ply 30. Although not shown, the belt ply 30 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 not less than 10 ° and not more than 35 °. In the tire 2, the belt 12 may be composed of two or more belt plies 30. In this case, the belt 12 is configured such that the direction of inclination of the cord of the belt ply 30 located on the inner side is opposite to the direction of inclination of the cord of the outer belt ply 30 located on the outer side in the radial direction. preferable. A preferred material for the cord is steel. An organic fiber as described above may be used for the cord.

  The band 14 is located outside the belt 12 on the inner side in the radial direction of the tread 4. The band 14 is laminated on the belt 12. Although not shown, the band 14 is composed of a cord and a topping rubber. The cord extends substantially in the circumferential direction and is wound spirally.

  In the tire 2, the absolute value of the angle formed by the cord of the band 14 with respect to the equator plane is 5 ° or less, particularly 2 ° or less. In the present invention, the direction in which the absolute value of the angle formed with respect to the equator plane is 5.0 ° or less is the “substantially circumferential direction”.

  In the tire 2, the band 14 has a so-called jointless structure. The band 14 can contribute to the rigidity of the tire 2 in the radial direction. In the tire 2, the influence of the centrifugal force that acts during traveling is suppressed. The tire 2 is excellent in high speed stability.

  In the tire 2, the cord of the band 14 is usually made of an organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  As described above, the bead 8 of the tire 2 includes the apex 26. As shown, the apex 26 is divided into three layers 32 in the axial direction. The apex 26 includes an inner layer 32a, an intermediate layer 32b, and an outer layer 32c. The inner layer 32a forms an inner part of the apex 26 in the axial direction. The inner layer 32 a extends outward in the radial direction from the upper surface 34 of the core 24. The middle layer 32b is located outside the inner layer 32a in the axial direction. The middle layer 32b forms the central portion of the apex 26 in the axial direction. The middle layer 32 b extends radially outward from the upper surface 34 of the core 24. The outer layer 32c is located further outside the middle layer 32b in the axial direction. The outer layer 32c forms an outer portion of the apex 26 in the axial direction. The outer layer 32 c extends radially outward from the upper surface 34 of the core 24.

  In the tire 2, an end 36 b (hereinafter referred to as an outer end) located outside in the radial direction of the middle layer 32 b is the tip of the apex 26. Therefore, the whole inner layer 32a is located inside the middle layer 32b in the axial direction. In the axial direction, the entire outer layer 32c is located outside the middle layer 32b. In the tire 2, the middle layer 32b is sandwiched between the inner layer 32a and the outer layer 32c in the axial direction. In the tire 2, an end 36a (hereinafter referred to as an outer end) located on the outer side in the radial direction of the inner layer 32a may be set to an equivalent position in the radial direction to the outer end 36b of the middle layer 32b. The outer end 36a of the inner layer 32a may be located inside the outer end 36b of the middle layer 32b in the radial direction. In the tire 2, an end 36c (hereinafter referred to as an outer end) located on the outer side in the radial direction of the outer layer 32c may be set to an equivalent position in the radial direction to the outer end 36b of the middle layer 32b. The outer end 36c of the outer layer 32c may be located inside the outer end 36b of the middle layer 32b in the radial direction.

  The tire 2 is manufactured as follows. The rubber composition for the inner layer 32a, the rubber composition for the middle layer 32b, and the rubber composition for the outer layer 32c are extruded simultaneously. These rubber compositions are integrated to obtain an apex 26 having a substantially triangular cross section. This apex 26 is laminated 32 on the core 24, and the bead 8 is obtained.

  Shown in FIG. 2 is a bead 8 in a state prior to vulcanization. As shown, the middle layer 32b is elongated. The cross section of the middle layer 32b is not a shape that tapers outward from the core 24 but a rectangular shape. The apex 26 having the middle layer 32b is difficult to curl. Moreover, the middle layer 32b is sandwiched between the outer layer 32c and the inner layer 32a. The outer layer 32 c and the inner layer 32 a can contribute to maintaining the shape of the apex 26. In the tire 2, curling of the apex 26 during the formation is effectively prevented. The tire 2 can be manufactured stably.

  In the method for manufacturing the tire 2, the bead 8 shown in FIG. 2 is assembled with another rubber member to obtain a raw cover (unvulcanized tire). Although not shown, this raw cover is put into a mold. The outer surface of the raw cover is in contact with the cavity surface of the mold. The inner surface of the raw cover contacts the bladder or the core. The raw cover is pressurized and heated in the mold. The rubber composition of the raw cover flows by pressurization and heating. The rectangular middle layer 32b is deformed into a tapered shape as shown in FIG. The rubber causes a crosslinking reaction by heating, and the tire 2 is obtained.

  As shown in FIG. 1, in the tire 2, the tip 36 b of the apex 26 is located in the vicinity of the end 22 of the tread 4. The apex 26 is divided into three in the axial direction, and the hardness Hm of the middle layer 32b forming the central portion thereof is higher than the hardness Hi of the inner layer 32a. The hardness Hm of the middle layer 32b is higher than the hardness Ho of the outer layer 32c. In other words, the middle layer 32b is thin and hard. The middle layer 32b can contribute to the turning performance and absorbability of the tire 2. The tire 2 is excellent in turning performance and absorbability.

  In this specification, the hardness Hi of the inner layer 32a, the hardness Hm of the middle layer 32b, and the hardness Ho of the outer layer 32c are JIS-A hardness. These hardnesses are measured with a type A durometer in an environment of 23 ° C. in accordance with the provisions of “JIS-K6253”. More specifically, these hardnesses are measured by pressing a type A durometer against the cross section shown in FIG.

  In the tire 2, the hardness Hm of the middle layer 32b is 70 or more. By setting the hardness Hm to 70 or more, the middle layer 32b can effectively contribute to the turning performance and absorbability of the tire 2. In the tire 2, the hardness Hm of the middle layer 32b is preferably 90 or less. Thereby, the rigidity of the middle layer 32b is appropriately maintained, and the inhibition of absorbability by the middle layer 32b can be prevented. In this respect, the hardness Hm of the intermediate layer 32b is more preferably 85 or less.

  In the tire 2, the inner layer 32a is located on the inner side in the axial direction of the middle layer 32b, and can prevent deformation of the middle layer 32b during manufacturing. In the tire 2, the hardness Hi of the inner layer 32a is lower than the hardness Hm of the middle layer 32b. In other words, the inner layer 32a can prevent the deformation of the middle layer 32b while suppressing the influence on the rigidity of the apex 26. From this viewpoint, the hardness Hi of the inner layer 32a is preferably 60 or less. From the viewpoint of having an appropriate rigidity and effectively preventing deformation of the middle layer 32b, the hardness Hi of the inner layer 32a is preferably 40 or more, and more preferably 45 or more.

  As described above, in the tire 2, the hardness Hi of the inner layer 32a is lower than the hardness Hm of the middle layer 32b. Thereby, the influence on the rigidity of the apex 26 by the inner layer 32a is suppressed. From this viewpoint, the difference (Hm-Hi) between the hardness Hm of the intermediate layer 32b and the hardness Hi of the inner layer 32a is preferably 10 or more. The difference (Hm-Hi) is preferably 40 or less from the viewpoint that the inner layer 32a can effectively contribute to preventing deformation of the middle layer 32b.

  In the tire 2, the outer layer 32c is positioned on the outer side in the axial direction of the middle layer 32b, and can prevent deformation of the middle layer 32b during manufacturing. In the tire 2, the hardness Ho of the outer layer 32c is lower than the hardness Hm of the middle layer 32b. In other words, the outer layer 32 c can prevent the deformation of the middle layer 32 b while suppressing the influence on the rigidity of the apex 26. From this viewpoint, the hardness Ho of the outer layer 32c is preferably 60 or less. From the viewpoint of having appropriate rigidity and effectively preventing deformation of the middle layer 32b, the hardness Ho of the outer layer 32c is preferably 40 or more, and more preferably 45 or more.

  As described above, in the tire 2, the hardness Ho of the outer layer 32c is lower than the hardness Hm of the middle layer 32b. Thereby, the influence on the rigidity of the apex 26 by the outer layer 32c is suppressed. From this viewpoint, the difference (Hm−Ho) between the hardness Hm of the middle layer 32b and the hardness Ho of the outer layer 32c is preferably 10 or more. From the viewpoint that the outer layer 32c can effectively contribute to preventing deformation of the middle layer 32b, the difference (Hm−Ho) is preferably 40 or less.

  As shown in the drawing, in the tire 2, the apex 26 extends from the core 24 to the vicinity of the end 22 of the tread 4 on the inner side in the axial direction of the sidewall 6. In the tire 2, a portion unique to the rigidity of the sidewall 6 portion is not formed. Since the side wall 6 is appropriately bent, the tire 2 is excellent in absorbability.

  In FIG. 1, a double-headed arrow D represents a radial distance from the tip 36 b of the apex 26 to the end 22 of the tread 4. In the present specification, when the tip 36b of the apex 26 is located inside the end 22 of the tread 4 in the radial direction, the distance D is indicated by a positive value. When the tip 36b of the apex 26 is located outside the end 22 of the tread 4 in the radial direction, the distance D is indicated by a negative value.

  In the tire 2, the distance D is preferably 5 mm or less. Thereby, it is possible to prevent the formation of a portion peculiar to the rigidity of the portion of the sidewall 6 of the tire 2. In the tire 2, the side wall 6 is appropriately bent. The tire 2 is excellent in absorbability. From the viewpoint that the inhibition of absorbability by the apex 26 is prevented, the distance D is preferably -5 mm or more.

  In FIG. 1, a double arrow W represents the width of the middle layer 32 b that forms part of the apex 26. The width W is measured at the end of the middle layer 32b located on the core 24 side.

  In the tire 2, the width W is preferably 1 mm or more and 3 mm or less. By setting the width W to be 1 mm or more, the intermediate layer 32b has appropriate rigidity. The middle layer 32b can effectively contribute to the turning performance and absorbability of the tire 2. By setting the width W to 3 mm or less, the rigidity of the middle layer 32b is appropriately maintained, and the inhibition of absorbability by the middle layer 32b can be prevented.

  In the present invention, the size and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire 2. In the present specification, the normal rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. “Maximum air pressure” in JATMA standard, “Maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures.

  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 pneumatic tire for a motorcycle of Example 1 having the basic configuration shown in FIG. 1 and having the specifications shown in Table 1 below was obtained. The size of the tire was 120 / 70ZR17. This tire is for front wheels. In this tire, the radial distance D from the tip of the apex to the end of the tread was 0 mm. The outer layer hardness Ho was set to 60. The middle layer had a hardness Hm of 80. The hardness Hi of the inner layer was 60. The width W of this middle layer was 2 mm. In Example 1, the difference (Hm−Ho) between the hardness Hm of the middle layer and the hardness Ho of the outer layer is 20 and the difference (Hm−Hi) between the hardness Hm of the middle layer and the hardness Hi of the inner layer is 20 Met.

[Example 2-6]
A tire of Example 2-6 was obtained in the same manner as Example 1 except that the distance D was as shown in Table 1 below.

[Examples 7-9 and Comparative Example 2]
Tires of Examples 7-9 and Comparative Example 2 were obtained in the same manner as Example 1 except that the width W was as shown in Table 2 below.

[Example 10-11 and Comparative Example 3-4]
The tires of Example 10-11 and Comparative Example 3-4 are the same as Example 1 except that the hardness Hm, difference (Hm-Ho) and difference (Hm-Hi) of the middle layer are as shown in Table 3 below. Got.

[Example 12-15]
The tires of Examples 12-15 were the same as Example 1 except that the hardness Ho of the outer layer, the hardness Hi of the inner layer, the difference (Hm-Ho), and the difference (Hm-Hi) were as shown in Table 4 below. Obtained.

[Comparative Example 5]
Comparative Example 5 except that the hardness Ho of the outer layer, the hardness Hm of the intermediate layer, the hardness Hi of the inner layer, the difference (Hm-Ho) and the difference (Hm-Hi) were as shown in Table 5 below. Tires.

[Example 16]
The tire of Example 16 was obtained in the same manner as in Example 1 except that the distance D, width W, middle layer hardness Hm, difference (Hm-Ho), and difference (Hm-Hi) were as shown in Table 5 below. It was.

[Comparative Example 1]
Comparative Example 1 is a conventional tire. The tire apex is composed of a single rubber composition. The apex had a hardness of 70 °. The distance D was 15 mm.

[Evaluation of turning force and absorbency]
Prototype tires were mounted on the front wheels of a commercial two-wheeled vehicle (4-stroke) with a displacement of 1300 cc. The rim was MT3.50 × 17 and the tire air pressure was 250 kPa. Note that a commercially available conventional tire is mounted on the rear wheel. The nominal nominal size of the rear wheel tire is 180 / 55ZR17. The rim was MT 5.50 × 17 and the tire air pressure was 290 kPa. On the circuit course, turning from 100 km / h to 150 km / h and turning from 200 km / h to the maximum speed of the vehicle (about 280 km / h) are performed. And sensory evaluation on absorbency. Larger values indicate better results. The results are shown in Tables 1 to 5 below.

[Evaluation of longitudinal and lateral stiffness]
The transverse spring constant and longitudinal spring constant of the tire were measured under the following conditions.
Rim used: MT3.50
Internal pressure: 250 kPa
Load: 1.5kN
Regarding the longitudinal spring constant, the load dependency (ratio of change in the longitudinal spring constant with respect to the load change) was measured by changing the load from 0.8 kN to 1.8 kN. The results are shown in Tables 1 to 5 below as index values with a maximum of 10 points. Regarding the lateral stiffness, it is shown that the higher the numerical value, the higher the lateral spring constant. With respect to the longitudinal rigidity, the higher the numerical value, the smaller the rate of change, in other words, the smaller the load dependency.

[Cost Evaluation]
The cost per tire was calculated. The results are shown in Tables 1 to 5 below as index values with 10 points being perfect. The higher the value, the lower the cost.

[Comprehensive evaluation]
The average values of the turning force and absorbency are shown in the following Tables 1 to 5 as comprehensive points. Higher numbers indicate better. In addition, the case where this total score is 6.0 or more is set as the pass.

  As shown in Tables 1 to 5, the pneumatic tires of the examples have higher evaluation than the pneumatic tires of the comparative examples. From this evaluation result, the superiority of the present invention is clear.

  The apex described above can be applied to various pneumatic tires.

2 ... tyre 4 ... tread 6 ... side wall 8 ... bead 10 ... carcass 12 ... belt 14 ... band 22 ... end 24 ... core 26 ... Apex 28 ... Carcass ply 30 ... Belt ply 32, 32a, 32b, 32c ... Layer

Claims (5)

A tread whose outer surface forms a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the end of the tread, a pair of beads each positioned substantially radially inward of the sidewall, and the tread And a carcass stretched between one bead and the other bead along the inside of the sidewall,
The bead includes a core and an apex extending radially outward from the core,
The tip of this apex is located near the end of the tread,
The apex includes an inner layer, a middle layer positioned outside the inner layer in the axial direction, and an outer layer positioned further outside the middle layer in the axial direction.
The width of this middle layer is 1 mm or more and 3 mm or less,
The middle layer has a hardness of 70 to 85,
A pneumatic tire for a two-wheeled vehicle in which the hardness of the middle layer is higher than the hardness of the inner layer and the outer layer.   The pneumatic tire for a motorcycle according to claim 1, wherein a radial distance from a tip of the apex to an end of the tread is 5 mm or less.   The pneumatic tire for a motorcycle according to claim 1 or 2, wherein an outer end of the middle layer is a tip of the apex. The inner layer has a hardness of 60 or less,
The pneumatic tire for a motorcycle according to any one of claims 1 to 3, wherein the outer layer has a hardness of 60 or less.   The pneumatic tire for a motorcycle according to any one of claims 1 to 4, which is for a front wheel.

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