JP2020093691A - Tire for motorcycle - Google Patents

Abstract

A pneumatic tire having a strip apex is improved to improve the turning performance of a two-wheeled vehicle. A two-wheel vehicle tire includes a tread, a pair of sidewalls, a pair of beads, a carcass and a pair of strip apex. Each strip apex is axially inward of the sidewall and axially outward of the carcass and bead apexes. [Selection drawing] Fig. 1

Description

The present disclosure relates to a pneumatic tire mounted on a two-wheeled vehicle.

The tire disclosed in Patent Document 1 includes a pair of beads, a carcass, and a pair of strip apex. The bead has a core and an apex that extends radially outward from the core. The carcass has a main portion bridged between a pair of bead cores, and a folded portion that is wound around the bead core from the inner side toward the outer side in the axial direction and extends toward the outer side in the radial direction.

The strip apex is laminated on the main part of the carcass from the outside in the axial direction. The radially inner portion of the strip apex is curved inward in the axial direction and inserted into the carcass ply (the region between the main portion and the folded portion). Specifically, the radially inner portion of the strip apex is arranged axially inward of the folded portion of the carcass ply and is sandwiched between the main portion of the carcass ply and the apex of the bead.

JP, 2018-522236, A

By the way, since a two-wheeled vehicle turns while running with its body leaning laterally, a two-wheeled vehicle tire is required to have a higher turning performance than a four-wheeled vehicle tire. Specifically, when the two-wheeled vehicle is turning, the tire is tilted to the side and the ground contact portion of the tire moves to the side, so that a heavy load is applied to the side of the tire. Therefore, the tire of the two-wheeled vehicle is required to have appropriate rigidity for preventing the tire from excessively bending during turning.

Therefore, it is an object of the present invention to provide an improvement in a pneumatic tire having a strip apex that improves turning performance when applied to a two-wheeled vehicle.

A two-wheeled vehicle tire according to one aspect of the present invention includes a tread, a pair of sidewalls, a pair of beads, a carcass and a pair of strip apex, and each of the sidewalls is substantially within a radial direction from an end of the tread. Each of the beads, each of which is located axially inward of the sidewall, has a core and an apex extending substantially outward in the radial direction from the core, and the carcass has the tread. And, the strip apex is bridged between the pair of beads along the inner side of the sidewall in the radial direction, each strip apex is located on the inner side in the axial direction of the sidewall, and the carcass and the bead. Located outside the apex in the axial direction.

Preferably, a radial outer end of the strip apex is located radially outward of a maximum width position of the carcass, and the tire is mounted on a regular rim, and a radial inner end of the strip apex is located. However, it may be configured to be located radially inward of the radially outer end of the flange of the regular rim.

Preferably, when PA is defined as a point that is ¼ times the half width LT from the tread end with respect to the axial half width LT of the tread surface, the radial outer end of the strip apex has a radius larger than the point PA. The structure may be located on the inner side in the direction.

Preferably, the radial inner end of the strip apex may be located radially outward of the core.

Preferably, the carcass has a first ply and a second ply laminated on the outer side in the radial direction of the first ply, and the first ply spans between the cores of the pair of beads. And a pair of folded-back portions respectively extending from both ends of the main portion, each of the folded-back portions being wound around the core of the bead from the axially inner side to the axially outer side. The second ply may extend outward in the radial direction, the second ply may be overlapped with the folded-back portion, and the strip apex may be located axially outside both the first ply and the second ply. ..

Preferably, the folded-back portion may be located outside of the second ply in the axial direction, and the folded-back portion may be sandwiched between the strip apex and the second ply.

Preferably, the inner end of the second ply in the radial direction may be located radially outward of the core.

Preferably, in a state where the tire is mounted on the regular rim, a radial inner end of the second ply may be positioned radially inward of a radial outer end of a flange of the regular rim.

Preferably, the strip apex may have a complex elastic modulus of 40 MPa or more and 100 MPa or less.

According to the present invention, the entire strip apex is positioned axially inside the sidewall and axially outside the carcass and bead apex. Therefore, the curvature of the strip apex is reduced as compared with the conventional configuration in which the radially inner portion of the strip apex is sandwiched between the carcass and the apex of the bead. When a load is applied to the tire, stress in the compression direction is generated on the inner surface side of the tire and stress in the tensile direction is generated on the outer surface side of the tire. Therefore, the strip apex extends along the pulling direction on the outer surface side of the tire side portion, and the rigidity of the tire side portion can be increased. As a result, even when a heavy load is applied to the side portion of the tire during turning of the two-wheeled vehicle, excessive bending of the tire is prevented, and good turning performance can be exhibited.

1 is a cross-sectional view orthogonal to a circumferential direction of a two-wheeled vehicle tire according to an embodiment. It is an expanded sectional view of FIG.

Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate. In this specification, the size and angle of each member of the tire are measured in a state where the tire is incorporated in a regular rim and the tire is filled with air so as to have a regular internal pressure. No load is applied to the tire during measurement. In the present specification, a regular rim means a rim defined in a standard on which a tire relies. “Standard rim” in JATMA standard, “Design Rim” in TRA standard, and “Measuring Rim” in ETRTO standard are regular rims. In the present specification, the normal internal pressure means the internal pressure defined in the standard on which the tire relies. "Maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in JATMA standard, "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA standard, and "INFLATION PRESSURE" in ETRTO standard are normal internal pressures.

FIG. 1 shows a pneumatic tire 1 for a two-wheeled vehicle. In FIG. 1, the vertical direction is the radial direction Y of the tire 1, the horizontal direction is the axial direction X of the tire, and the direction perpendicular to the plane of the drawing is the circumferential direction of the tire 1. In FIG. 1, the alternate long and short dash line CL represents the equatorial plane of the tire. The shape of the tire 1 is symmetrical with respect to the equatorial plane CL except for the tread pattern.

The tire 1 includes a tread 2, a pair of sidewalls 3, a pair of beads 4, a carcass 5, an inner liner 6, a reinforcing layer 7, and a pair of strip apex 8. The tire 1 is a tubeless tire. The tire 1 is attached to a two-wheeled vehicle that turns while the vehicle body is tilted to the side.

Since the tire 1 has a shape that is symmetrical in the axial direction X, in FIG. 1, one of the pair of sidewalls 3, the pair of beads 4, and the pair of strip apex 8 on one side in the axial direction X, the bead 4, Only the strip apex 8 is shown. Hereinafter, for simplification of the description, the sidewall 3, the bead 4, and the strip apex 8 will be described as a representative one arranged on one side in the axial direction X.

The tread 2 has a convex shape outward in the radial direction Y. The tread 2 forms a tread surface 2a that contacts the road surface. The tread 2 is provided with a plurality of grooves (not shown). A tread pattern is formed by these grooves. The tread 2 is made of crosslinked rubber.

The sidewall 3 extends substantially inward in the radial direction Y from the end of the tread 2. The sidewall 3 is located outside the carcass 5. The outer end of the sidewall 3 in the radial direction Y is joined to the tread 2. The sidewall 3 is made of crosslinked rubber. The sidewalls 3 prevent the carcass 6 from being damaged.

The bead 4 is located inside the sidewall 3 in the axial direction X. The bead 4 includes a core 11 and an apex 12 extending outward from the core 11 in the radial direction Y. The core 11 has a ring shape and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 12 is tapered outward in the radial direction Y. The apex 12 is made of high hardness crosslinked rubber.

The carcass 5 extends along the tread 2 and the sidewall 3. The carcass 5 is bridged between the beads 4 on both sides. The carcass 5 includes a first ply 13 and a second ply 14. The first ply 13 is bridged between the beads 4 on both sides. The first ply 13 has a main portion 13a that is bridged between the cores 11 of the beads 4 on both sides, and a radius that is extended from the end of the main portion 13a and is wound around the core 11 from the inner side to the outer side in the axial direction X. And a folded-back portion 13b extending outward in the direction.

The second ply 14 is superposed on the folded-back portion 13b. The second ply 14 is laminated on the outside of the main portion 13a of the first ply 13 in the radial direction Y. A portion of the second ply 14 that overlaps with the apex 12 is laminated outside the apex 12 in the axial direction X. When the tire 1 is assembled to the regular rim 10, the radially inner end 14a of the second ply 14 is located radially inward of the radially outer end 10aa of the flange 10a of the rim 10. However, the radial inner end 14 a of the second ply 14 is located outside the core 11 in the radial direction Y. That is, the second ply 14 is not wound around the core 11. Therefore, it is possible to prevent the thickness around the core 11 of the tire 1 from becoming too large. The folding|returning part 13a of the 1st ply 13 is located in the axial direction outer side of the 2nd ply 14, and is laminated|stacked on the 2nd ply 14 from the axial direction X outer side.

The first ply 13 and the second ply 14 of the carcass 5 each include a large number of cords and a topping rubber arranged in parallel. The absolute value of the angle formed by each code with respect to the equatorial plane is 75° to 90°. In other words, the carcass 5 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 5 may be formed from one ply.

The inner liner 6 is located inside the carcass 5. The inner liner 6 is joined to the inner surface of the carcass 5. The inner liner 6 is made of a crosslinked rubber having an excellent air shielding property. A typical base rubber of the inner liner 6 is butyl rubber or halogenated butyl rubber. The inner liner 6 holds the internal pressure of the tire.

The reinforcing layer 7 is located inside the radial direction Y of the tread 2. The reinforcing layer 7 is laminated on the carcass 5 from the outside in the radial direction Y to reinforce the carcass 5. In the example of FIG. 1, the reinforcing layer 7 is, for example, a band, but may be a belt and a band. The band consists of a cord and a topping rubber. The cord is spirally wound. The band 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 cord is made of organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers.

When the reinforcing layer 7 is composed of a belt and a band, the band is laminated outside the belt in the radial direction Y. The belt consists of an inner layer and an outer layer. Each of the inner layer and the outer layer is composed of many cords and topping rubbers arranged in parallel. Each cord is inclined with respect to the equatorial plane CL. A general absolute value of the inclination angle is 10° or more and 35° or less. The inclination direction of the cord of the inner layer with respect to the equatorial plane is opposite to the inclination direction of the cord of the outer layer with respect to the equatorial plane. The preferred material for the cord is steel. Organic fibers may be used for the cord. The width of the belt in the axial direction X is preferably 0.7 times or more the maximum width of the tire 1. The belt may comprise more than two layers.

As shown in FIGS. 1 and 2, the strip apex 8 is located inside the sidewall 3 in the axial direction. The strip apex 8 reinforces the portion of the carcass 5 on the bead 4 side. The strip apex 8 has a substantially uniform thickness as a whole, and is configured such that the difference between the maximum value and the minimum value of the thickness is within 0.1 mm. The strip apex 8 is made of crosslinked rubber. The strip apex 8 is harder than the tread 2 and the sidewall 3 and may be harder than the carcass 5.

The complex elastic modulus of the strip apex 8 is preferably larger than the complex elastic modulus of the apex 12 of the bead 4, for example. The complex elastic modulus of the strip apex 8 is set to a value of 40 MPa or more and 100 MPa or less, preferably 50 MPa or more and 80 MPa or less. The complex elastic modulus is measured according to the regulations of "JIS K 6394". In this measurement, a plate-shaped test piece (length=45 mm, width=4 mm, thickness=2 mm) is used. This test piece may be cut out from the tire 1, or may be cut out from this sheet by making a sheet from the rubber composition. The measurement conditions of this complex elastic modulus are as follows.
Viscoelasticity spectrometer: "VESF-3" by Iwamoto Seisakusho
Initial strain: 10%
Dynamic strain: ±2%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70℃

The entire strip apex 8 is located outside the carcass 5 in the axial direction X. The strip apex 8 is located outside the axial direction X of both the first ply 13 and the second ply 14. The strip apex 8 is located outside the bead 4 in the axial direction X. That is, a portion of the strip apex 8 in the radial direction (that is, a portion of the strip apex 8 that overlaps the apex 12 of the bead 4 in the axial direction X) is located between the carcass 5 and the apex 12 of the bead 4. Not sandwiched. In other words, the folded-back portion 13b of the first ply 13 is sandwiched between the strip apex 8 and the second ply 14.

Since the entire strip apex 8 is located outside the carcass 5 and the bead 4 in the axial direction X, the strip apex 8 is less curved than before. Therefore, when a load is applied to the tire 1, the strip apex 8 extends along the pulling direction on the outer surface side of the side portion of the tire 1, and the rigidity of the side portion of the tire 1 increases. Therefore, even when a heavy load is applied to the side portion of the tire 1 during turning of the two-wheeled vehicle, excessive bending of the tire 1 can be prevented.

The solid line BBL shown in FIGS. 1 and 2 is the bead baseline. The bead baseline is a line that defines the rim diameter of the regular rim 10 (see JATMA). The bead base line BBL extends in the axial direction X. The double-headed arrow P1 represents the radial distance from the bead base line BBL to the radially inner end 14a of the second ply 14, and in the present embodiment, the radius of the inner end 14a of the second ply 14 relative to the bead base line BBL. Directional height. A double-headed arrow S1 represents a radial distance from the bead base line BBL to the radially inner end 8b of the strip apex 8, and in the present embodiment, the radius of the inner end 8b of the strip apex 8 with respect to the bead base line BBL. Directional height. The double-headed arrow G represents the radial distance from the bead baseline BBL to the radially outer end 10aa of the flange 10a of the rim 10, and in the present embodiment, the radial direction of the outer end 10aa of the flange 10a based on the bead baseline BBL. It is high.

The double-headed arrow H1 represents the radial distance from the bead base line BBL to the maximum width position PW that exhibits the maximum width WT in the axial direction X of the carcass 5. In the present embodiment, the maximum distance of the carcass 5 based on the bead base line BBL. This is the radial height of the large position PW. A double-headed arrow H2 represents a radial distance from the bead base line BBL to the tread end PT, and is a radial height of the tread end PT based on the bead base line BBL in the present embodiment. The double-headed arrow S2 represents the radial distance from the bead baseline BBL to the radially outer end 8a of the strip apex 8, and in the present embodiment, the radius of the outer end 8a of the strip apex 8 with respect to the bead baseline BBL. Directional height. The double-headed arrow P2 represents the radial distance from the bead base line BBL to the radially outer end 13ba of the folded portion 13b of the first ply 13, and in the present embodiment, the outer end of the folded portion 13b with respect to the bead base line BBL. A radial height of 13 ba.

The radial outer end 8a of the strip apex 8 is located radially outside the maximum width position PW of the carcass 5. That is, the radial height S2 of the radial outer end 8a of the strip apex 8 is larger than the radial height H1 of the maximum width position PW of the carcass 5. Since the carcass 5 flexes most at the maximum width position PW, the strip apex 8 extends to the outer side in the radial direction from this position PW, so that the rigidity is improved. From this viewpoint, the difference (S2-H1) between the height S2 and the height H1 is preferably 2 mm or more, more preferably 4 mm or more. Further, in the present embodiment, the radial outer end 8a of the strip apex 8 is located radially outside the tread end PT. That is, the radial height S2 of the radial outer end 8a of the strip apex 8 is larger than the radial height H2 of the tread end PT. Therefore, even if the tire 1 tilts to the side and the ground contact portion of the tread surface 2a moves to the side, the strip apex 8 easily bears the ground load and the turning performance is improved.

On the other hand, when PA is defined as a point that is 1/4 times the half width LT from the tread end PT with respect to the axial half width LT of the tread surface 2a, the radial outer end 8a of the strip apex 8 has a radius larger than the point PA. Located inside the direction. Regarding the distance measured along the tread surface 2a in the cross section perpendicular to the circumferential direction of the tire 1, the distance L1 from the tread end PT to the radially outer end 8a of the strip apex 8 is from the tread end PT to the point PA. It is smaller than the distance LT/4. Further, in the present embodiment, the radial outer end 8a of the strip apex 8 is positioned radially inward of the radial outer end 13ba of the folded portion 13b of the first ply 13. That is, the radial height S2 of the radial outer end 8a of the strip apex 8 is smaller than the radial height P2 of the radial outer end 13ba of the folded portion 13ba. In other words, with respect to the distance measured along the tread surface 2a in the cross section perpendicular to the circumferential direction of the tire 1, the distance L1 from the tread end PT to the radially outer end 8a of the strip apex 8 is folded from the tread end PT. It is smaller than the distance L2 to the radially outer end 13ba of the portion 13ba. Therefore, the rigidity of the central portion of the tire 1 in the axial direction X does not become excessive, the riding comfort of the two-wheeled vehicle during straight running is improved, and the transient characteristics during turning running are maintained well.

When the tire 1 is mounted on the regular rim 10, the radial inner end 8b of the strip apex 8 is located radially inward of the radial outer end 10aa of the flange 10a of the rim 10. That is, the radial height S1 of the radial inner end 8b of the strip apex 8 is smaller than the radial height G of the radial outer end 10aa of the flange 10a of the rim 10. Therefore, even in the tire 1 in which the second ply 14 is not wound around the core 11, the rigidity of the tire 1 in the vicinity of the flange 10a of the rim 10 is improved, and the tire transmitted by the load transmitted from the flange 10a to the tire 1 is tired. The bead 4 side portion of 1 is prevented from excessively bending, and the turning performance is improved. From this viewpoint, the difference (G-S1) between the height G and the height S1 is preferably 2 mm or more, more preferably 4 mm or more.

On the other hand, the radial inner end 8b of the strip apex 8 is located radially outside the core 11 of the bead 4. Further, in the present embodiment, the radial inner end 8b of the strip apex 8 is located radially outward of the radial inner end 14a of the second ply 14. That is, the radial height S1 of the radial inner end 8b of the strip apex 8 is larger than the radial height P1 of the radial inner end 14a of the second ply 14. Therefore, while the rigidity of the side portion of the tire 1 is appropriately maintained, the portion of the tire 1 supported by the regular rim 10 is prevented from becoming excessively thick.

Hereinafter, the effects of the tire of the present invention will be clarified by examples, but the present invention should not be limitedly interpreted based on the description of the examples.

[Example 1]
Example 1 is the tire shown in FIGS. 1 and 2 and has the specifications shown in Table 2 below. The size of this tire is 180/55 ZR17 M/C. The size of the rim is 17M/C x MT 5.50. The strip apex had a complex elastic modulus of 60 MPa and a loss tangent of 0.15.

[Comparative Example 1]
The tire of Comparative Example 1 is a tire that does not include the strip apex and has the specifications shown in Table 1 below. In the tire of Comparative Example 1, the radially inner end of the second ply of the carcass is located radially outside the radially outer end of the rim flange. The tire of Comparative Example 1 has the same configuration as that of Example 1 except that the strip apex is not provided and the radial inner end of the second ply is positioned.

[Comparative example 2]
The tire of Comparative Example 2 is a tire that does not include the strip apex and has the specifications shown in Table 1 below. The tire of Comparative Example 2 has the same structure as that of Example 1 except that the strip apex is not provided.

[Comparative Example 3]
The tire of Comparative Example 3 includes a strip apex, but has the same configuration as the tire disclosed in Patent Document 1 above. In the tire of Comparative Example 3, the bead-side portion of the strip apex (that is, the portion of the strip apex that overlaps the bead apex) is located axially inward of the bead apex, and otherwise. It has the same configuration as that of the first embodiment.

[Example 2]
In the tire of Example 2, the height (radial position) of the radial inner end of the strip apex is the same as the height (radial position) of the radial outer end of the rim flange. The tire of Example 2 has the same configuration as that of Example 1 except for the height of the radial inner end of the strip apex.

[Example 3]
In the tire of Example 3, the height (radial position) of the outer end of the strip apex in the radial direction is the same as the height (radial position) of the maximum width position of the carcass. The tire of Example 3 has the same configuration as that of Example 1 except for the height of the radial outer end of the strip apex.

[Example 4]
In the tire of Example 4, the height (radial position) of the radial outer end of the strip apex is larger than the height (radial position) of the radial outer end of the folded portion of the first ply of the carcass. The tire of Example 4 has the same configuration as that of Example 1 except for the height of the radial outer end of the strip apex.

[Example 5]
In the tire of Example 5, the second ply of the carcass is located axially outside the folded-back portion of the first ply of the carcass. That is, the second ply is sandwiched between the folded portion of the first partial ply and the strip apex. The tire of Example 5 has the same configuration as that of Example 1 except for the axial position of the second ply of the carcass.

[Rigidity and high-speed stability]
In a two-wheeled vehicle with a displacement of 1300 cc, tires of 180/55ZR17 M/C size of Example/Comparative Example were mounted on a rim of 17 M/C×MT5.50 size on the rear wheel side, respectively, and an internal pressure of 290 kPa. The tire was filled with air so that Further, a tire having a size of 120/70ZR17 M/C was attached to a rim having a size of 17 M/C×MT3.50 on the front wheel side of the two-wheeled vehicle, and the tire was filled with air so that the internal pressure was 250 kPa. A rider was allowed to drive this motorcycle on a racing circuit to evaluate the feeling of rigidity and high-speed stability. The results are shown in Tables 1 and 2 below as indexes. It should be noted that the larger the numerical values of rigidity and high-speed stability, the better the performance.

As shown in Tables 1 and 2, the tires of the examples are superior in rigidity and high-speed stability to the tires of the comparative examples, and the turning performance as a two-wheeled vehicle is high. From this evaluation result, the superiority of the present invention is clear.

1 Tire 2 Tread 3 Sidewall 4 Bead 5 Carcass 6 Inner Liner 7 Reinforcing Layer 8 Strip Apex 10 Rim 10a Flange 11 Core 12 Apex 13 First Ply 13a Main Part 13b Folding Part 14 Second Ply

Claims (9)

With a tread, a pair of sidewalls, a pair of beads, a carcass and a pair of strip apex,
Each of the sidewalls extends substantially inward in the radial direction from the end of the tread,
Each of the beads is located axially inward of the sidewall, and has a core and an apex extending substantially outward in the radial direction from the core,
The carcass is bridged between the pair of beads along the inner side in the radial direction of the tread and the sidewall,
A tire for a two-wheeled vehicle, wherein each of the strip apex is located on the inner side of the sidewall in the axial direction and on the outer side of the carcass and the bead in the axial direction. The outer end in the radial direction of the strip apex is located radially outside of the maximum width position of the carcass,
The radial inner end of each of the strip apex is located radially inward of the radial outer end of the flange of the regular rim when the tire is mounted on the regular rim. Tires for motorcycles. When PA is defined as a point that is 1/4 times the half width LT from the tread end with respect to the axial half width LT of the tread surface,
The tire for a two-wheeled vehicle according to claim 2, wherein a radial outer end of the strip apex is located radially inward of the point PA. The tire for a two-wheeled vehicle according to claim 2 or 3, wherein an inner end in the radial direction of the strip apex is located radially outside of the core. The carcass has a first ply and a second ply laminated on the outer side in the radial direction of the first ply,
The first ply has a main portion bridged between the cores of the pair of beads, and a pair of folded-back portions extending from both ends of the main portion,
Each of the folded-back portions is wound from the axially inner side to the axially outer side around the core of the bead and extends radially outward,
The second ply is laid on the folded portion,
The tire for a two-wheeled vehicle according to any one of claims 1 to 4, wherein the strip apex is located on the outer side in the axial direction of both the first ply and the second ply. The folded-back portion is located on the outer side in the axial direction of the second ply,
The tire for a motorcycle according to claim 5, wherein the folded-back portion is sandwiched between the strip apex and the second ply. The tire for a two-wheeled vehicle according to claim 5 or 6, wherein an inner end in the radial direction of the second ply is located outside in the radial direction with respect to the core. The motorcycle according to claim 7, wherein a radial inner end of the second ply is located radially inward of a radial outer end of a flange of the regular rim when the tire is mounted on the regular rim. Tires. The tire for motorcycles according to any one of claims 1 to 8, wherein the strip apex has a complex elastic modulus of 40 MPa or more and 100 MPa or less.

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