JP7230479B2 - Two-wheeled vehicle tire - Google Patents

Description

The present disclosure relates to pneumatic tires mounted on two-wheeled vehicles.

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

The strip apex is laminated to the main portion of the carcass from the axial outside. A radially inner portion of the strip apex is curved axially inward and inserted into the interior of the carcass ply (the region between the main portion and the turnup portion). Specifically, the radially inner portion of the strip apex is located axially inward of the turnup portion of the carcass ply and is sandwiched between the main portion of the carcass ply and the bead apex.

JP 2018-52236 A

By the way, since a two-wheeled vehicle turns while tilting its body to the side, tires for two-wheeled vehicles are required to have higher turning performance than tires for four-wheeled vehicles. Specifically, when a two-wheeled vehicle turns, the tire tilts to the side, causing the contact point of the tire to move sideways, and a strong load is applied to the side of the tire. Therefore, a tire of a two-wheeled vehicle is required to have an appropriate rigidity to prevent excessive tire deflection during cornering.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an improvement in a pneumatic tire having a strip apex to improve 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 apexes, each of the sidewalls extending substantially inward from the edge of the tread in the radial direction. Each bead has a core and an apex extending generally radially outward from the core, with each bead being positioned axially inward of the sidewall, the carcass extending from the tread. and along the radially inner side of the sidewall and spanned between the pair of beads, each of the strip apexes being located axially inward of the sidewall, and the carcass and the bead located axially outside the apex of the

Preferably, the radially outer end of the strip apex is located radially outside the maximum width position of the carcass, and the radially inner end of the strip apex is positioned radially outwardly of the tire mounted on a regular rim. may be located radially inward of the radially outer end of the flange of the regular rim.

Preferably, when a point corresponding to 1/4 times the half width LT of the tread surface from the tread end is defined as PA, the radially outer end of the strip apex has a radius greater than the point PA. It is good also as composition located in the direction inner side.

Preferably, the radially inner end of the strip apex may be positioned radially outside of the core.

Preferably, the carcass has a first ply and a second ply laminated radially outwardly of the first ply, and the first ply spans between the cores of the pair of beads. and a pair of folded portions extending from both ends of the main portion, and each folded portion is wound around the core of the bead from the inner side to the outer side in the axial direction. Extending radially outward, the second ply may overlap the turnup portion, and the strip apex may be axially outward of both the first ply and the second ply. .

Preferably, the folded portion may be positioned axially outside the second ply, and the folded portion may be sandwiched between the strip apex and the second ply.

Preferably, the radially inner end of the second ply may be positioned radially outside of the core.

Preferably, the radially inner end of the second ply may be located radially inwardly of the radially outer end of the flange of the regular rim when the tire is mounted on 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 invention, the entire strip apex is located axially inside the sidewall and axially outside the carcass and bead apex. As such, the curvature of the strip apex is reduced compared to conventional arrangements in which the radially inner portion of the strip apex is sandwiched between the carcass and the bead apex. When a load is applied to the tire, compressive stress is generated on the inner surface of the tire and tensile stress is generated on the outer surface 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 if a strong load is applied to the side portion of the tire when the two-wheeled vehicle turns, the tire is prevented from flexing excessively, and good turning performance can be exhibited.

1 is a cross-sectional view orthogonal to the circumferential direction of a tire for a two-wheeled vehicle according to an embodiment; FIG. 2 is an enlarged sectional view of FIG. 1; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings. In this specification, the dimensions and angles of each member of the tire are measured when the tire is mounted on a regular rim and inflated to a regular internal pressure. No load is applied to the tire during the measurement. As used herein, the term "regular rim" means a rim defined in the standards on which tires rely. A "standard rim" in the JATMA standard, a "design rim" in the TRA standard, and a "measuring rim" in the ETRTO standard are regular rims. As used herein, the normal internal pressure means the internal pressure defined in the standards on which the tire relies. The "maximum air pressure" in JATMA standards, the "maximum value" in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA standards, and the "INFLATION PRESSURE" in ETRTO standards are regular internal pressures.

FIG. 1 shows a pneumatic tire 1 for a two-wheeled vehicle. 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 paper surface is the circumferential direction of the tire 1. As shown in FIG. In FIG. 1, the dashed-dotted line CL represents the equatorial plane of the tire. The shape of this tire 1 is symmetrical with respect to the equatorial plane CL, except for the tread pattern.

The tire 1 comprises 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. Tire 1 is a tubeless tire. The tire 1 is mounted on a two-wheeled vehicle that turns while tilting the vehicle body sideways.

Since the tire 1 has a symmetrical shape in the axial direction X, in FIG. Only strip apex 8 is shown. In the following, for simplification of explanation, the sidewall 3, the bead 4 and the strip apex 8 arranged on one side in the axial direction X will be representatively explained.

The tread 2 has an outwardly convex shape in the radial direction Y. As shown in FIG. The tread 2 forms a tread surface 2a that contacts the road surface. The tread 2 is carved with a plurality of grooves (not shown). These grooves form a tread pattern. The tread 2 is made of crosslinked rubber.

The sidewall 3 extends substantially inward in the radial direction Y from the edge of the tread 2 . The sidewall 3 is positioned outside the carcass 5. - 特許庁A radial Y outer end of the sidewall 3 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. As shown in FIG. The bead 4 comprises a core 11 and an apex 12 extending outward in the radial direction Y from the core 11 . The core 11 is ring-shaped and includes a wound non-stretchable wire. A typical material for the wire is steel. Apex 12 tapers outwardly in radial direction Y. The apex 12 is made of crosslinked rubber with high hardness.

Carcass 5 runs along tread 2 and sidewalls 3 . The carcass 5 is spanned between the beads 4 on both sides. The carcass 5 consists of a first ply 13 and a second ply 14 . The first ply 13 spans between the beads 4 on both sides. The first ply 13 includes a main portion 13a that spans between the cores 11 of the beads 4 on both sides, and an end of the main portion 13a that extends from the core 11 in the axial direction X and is wound from the inside to the outside in the radial direction. and a folded portion 13b extending outward.

The second ply 14 is overlaid on the folded portion 13b. The second ply 14 is laminated on the outer side in the radial direction Y of the main portion 13 a of the first ply 13 . A portion of the second ply 14 that overlaps the apex 12 is laminated on the outside of the apex 12 in the axial direction X. As shown in FIG. When the tire 1 is mounted on the regular rim 10 , the radial inner end 14 a of the second ply 14 is located radially inward of the radial outer end 10 aa of the flange 10 a of the rim 10 . However, the radially inner end 14a of the second ply 14 is located radially outside of the core 11 in the Y direction. That is, the second ply 14 is not wrapped around the core 11 . Therefore, the thickness around the core 11 of the tire 1 is prevented from becoming too large. The folded portion 13a of the first ply 13 is positioned axially outward of the second ply 14 and is laminated on the second ply 14 from the axial direction X outer side.

The first ply 13 and the second ply 14 of the carcass 5 are each composed of a large number of parallel cords and a topping rubber. The absolute value of the angle that each code makes with the equatorial plane ranges from 75° to 90°. In other words, the carcass 5 has a radial structure. The cord consists of organic fibers. Preferred organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers. Carcass 5 may be formed from one ply.

The inner liner 6 is positioned 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 crosslinked rubber with excellent air shielding properties. A typical base rubber for the inner liner 6 is butyl rubber or halogenated butyl rubber. The inner liner 6 retains the internal pressure of the tire.

The reinforcing layer 7 is located inside the tread 2 in the radial direction Y. As shown in FIG. 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 it may be made up of a belt and a band. A 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 circumferentially. The angle of the cords with respect to the circumferential direction is 5° or less, or even 2° or less. The cord consists of organic fibers. Preferred organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers.

When the reinforcing layer 7 consists of a belt and a band, the band is laminated on the outer side in the radial direction Y of the belt. The belt consists of an inner layer and an outer layer. Each of the inner layer and the outer layer consists of a number of parallel cords and a topping rubber. Each cord is inclined with respect to the equatorial plane CL. A general absolute value of the tilt angle is 10° or more and 35° or less. The direction of inclination of the cords of the inner layer with respect to the equatorial plane is opposite to the direction of inclination of the cords of the outer layer with respect to the equatorial plane. A 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 three or more layers.

As shown in FIGS. 1 and 2, the strip apex 8 is located axially inside the sidewall 3 . 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 thickness and the minimum 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 sidewalls 3 and may be harder than the carcass 5 .

The complex modulus of elasticity of strip apex 8 is preferably greater than the complex modulus of elasticity of apex 12 of bead 4, for example. The complex elastic modulus of the strip apex 8 is set to, for example, 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 in accordance with "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 a sheet produced from the rubber composition. The measurement conditions for this complex elastic modulus are as follows.
Viscoelastic spectrometer: Iwamoto Seisakusho's "VESF-3"
Initial strain: 10%
Dynamic strain: ±2%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70°C

The entire strip apex 8 is located outside the carcass 5 in the axial direction X. The strip apex 8 is located axially X outside 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. As shown in FIG. That is, the radially inner portion of the strip apex 8 (that is, the portion of the strip apex 8 that overlaps the apex 12 of the bead 4 in the axial direction X) is between the carcass 5 and the apex 12 of the bead 4. not sandwiched. In other words, the folded portion 13 b of the first ply 13 is sandwiched between the strip apex 8 and the second ply 14 .

Since the strip apex 8 as a whole is positioned axially outside the carcass 5 and the bead 4 as a whole, the curvature of the strip apex 8 is smaller 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 , increasing the rigidity of the side portion of the tire 1 . Therefore, even if a strong load is applied to the side portion of the tire 1 when the two-wheeled vehicle turns, it is possible to prevent the tire 1 from being excessively flexed.

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). A bead baseline BBL extends in the axial direction X. A double-headed arrow P1 represents the radial distance from the bead baseline BBL to the radially inner end 14a of the second ply 14, which in this embodiment is the radius of the inner end 14a of the second ply 14 relative to the bead baseline BBL. is the directional height. A double-headed arrow S1 represents the radial distance from the bead baseline BBL to the radially inner end 8b of the strip apex 8, which in this embodiment is the radius of the inner end 8b of the strip apex 8 relative to the bead baseline BBL. is the directional height. A 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, in this embodiment the radial direction of the outer end 10aa of the flange 10a relative to the bead baseline BBL. Height.

A double-headed arrow H1 represents the radial distance from the bead baseline BBL to the maximum width position PW exhibiting the maximum width WT in the axial direction X of the carcass 5. It is the radial height of the large position PW. A double-headed arrow H2 represents the radial distance from the bead baseline BBL to the tread edge PT, which in this embodiment is the radial height of the tread edge PT with respect to the bead baseline BBL. A double arrow S2 represents the radial distance from the bead baseline BBL to the radially outer end 8a of the strip apex 8, which in this embodiment is the radius of the outer end 8a of the strip apex 8 relative to the bead baseline BBL. is the directional height. A double-headed arrow P2 represents the radial distance from the bead baseline BBL to the radial outer end 13ba of the folded portion 13b of the first ply 13. In this embodiment, the outer end of the folded portion 13b is based on the bead baseline BBL. 13 ba radial height.

A radially outer end 8 a 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 greater than the radial height H1 of the carcass 5 at the maximum width position PW. Since the carcass 5 bends most at the maximum width position PW, the strip apex 8 extends radially outward from this position PW, thereby improving the rigidity. From this point of view, 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 this embodiment, the radially outer end 8a of the strip apex 8 is positioned radially outwardly of the tread edge PT. That is, the radial height S2 of the radially outer end 8a of the strip apex 8 is greater than the radial height H2 of the tread edge PT. Therefore, even if the tire 1 inclines laterally and the ground-contacting portion of the tread surface 2a moves laterally, the strip apex 8 easily bears the ground-contact load, thereby improving the turning performance.

On the other hand, when the point corresponding to 1/4 times the half width LT from the tread end PT to the axial half width LT of the tread surface 2a is PA, the radially outer end 8a of the strip apex 8 has a radius larger than the point PA. Direction inside. 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 edge PT to the radial outer edge 8a of the strip apex 8 is the distance from the tread edge PT to the point PA. smaller than the distance LT/4. Further, in this embodiment, the radially outer end 8a of the strip apex 8 is located radially inside the radially 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, 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 edge PT to the radial outer edge 8a of the strip apex 8 is the distance L1 from the tread edge 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, and the ride comfort of the two-wheeled vehicle is improved during straight running, and the transitional characteristics during cornering are maintained well.

When the tire 1 is mounted on the regular rim 10 , the radially inner end 8 b of the strip apex 8 is located radially inward of the radially outer end 10 aa of the flange 10 a of the rim 10 . That is, the radial height S 1 of the radially inner end 8 b of the strip apex 8 is less than the radial height G of the radially outer end 10 aa of the flange 10 a 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 near the flange 10a of the rim 10 is improved, and the load transmitted from the flange 10a to the tire 1 increases the tire 1. Excessive bending of the bead 4 side portion of 1 is prevented, and turning performance is improved. From this point of view, 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 radially inner end 8b of the strip apex 8 is positioned radially outside of the core 11 of the bead 4 . Further in this embodiment, the radially inner end 8b of the strip apex 8 is located radially outside the radially inner end 14a of the second ply 14 . That is, the radial height S 1 of the radially inner end 8 b of the strip apex 8 is greater than the radial height P 1 of the radially inner end 14 a of the second ply 14 . Therefore, the portion of the tire 1 supported by the regular rim 10 is prevented from becoming excessively thick while the rigidity of the side portion of the tire 1 is appropriately maintained.

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

[Example 1]
Example 1 is the tire shown in Figures 1 and 2, with the specifications shown in Table 2 below. The size of this tire is 180/55ZR17 M/C. The rim size is 17M/C x MT5.50. The strip apex has 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 without a 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 flange of the rim. 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 position of the radially inner end of the second ply.

[Comparative Example 2]
The tire of Comparative Example 2 is a tire without a strip apex and has the specifications shown in Table 1 below. The tire of Comparative Example 2 has the same configuration as that of Example 1 except that it does not have a strip apex.

[Comparative Example 3]
The tire of Comparative Example 3 has 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 the rest It has the same configuration as the first embodiment.

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

[Example 3]
In the tire of Example 3, the height (radial position) of the radially outer end of the strip apex 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 radially outer end of the strip apex is greater than the height (radial position) of the radially outer end of the turnup 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 positioned axially outside the turn-up portion of the first ply of the carcass. That is, the second ply is sandwiched between the folded portion of the first 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, a 180/55ZR17 M/C size tire of Example/Comparative Example was mounted on a 17M/C×MT5.50 size rim on the rear wheel side, and the internal pressure was 290 kPa. The tire was filled with air so that A 120/70ZR17 M/C size tire was attached to a 17M/C×MT3.50 size rim on the front wheel side of the two-wheeled vehicle, and the tire was inflated to an internal pressure of 250 kPa. A rider was asked to drive this two-wheeled vehicle on a racing circuit to evaluate its rigidity and high-speed stability. The results are shown as indices in Tables 1 and 2 below. It should be noted that the higher the values of stiffness 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, and the turning performance as a two-wheeled vehicle is higher than the tires of the comparative examples. From this evaluation result, the superiority of the present invention is clear.

REFERENCE SIGNS LIST 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 portion 13b turn-up portion 14 second ply

Claims (5)

Equipped with a tread, a pair of sidewalls, a pair of beads, a carcass and a pair of strip apex,
each said sidewall extending generally radially inward from an edge of said tread;
each of the beads positioned axially inwardly of the sidewalls and having a core and an apex extending substantially radially outward from the core;
The carcass spans between the pair of beads along the radially inner side of the tread and the sidewall,
each said strip apex being axially inward of said sidewall and axially outward of said carcass and said bead;
The carcass has a first ply and a second ply laminated radially outward of the first ply,
The first ply has a main portion spanning between the cores of the pair of beads and a pair of folded portions extending from both ends of the main portion,
each of the turn-ups extending radially outwardly wrapped around the core of the bead from the axially inner side to the axially outer side;
The second ply is superimposed on the folded portion,
A two-wheeled vehicle tire, wherein the strip apex is axially outward of both the first ply and the second ply. The folded portion is positioned axially outside the second ply,
2. The tire for a two-wheeled vehicle according to claim 1 , wherein said turn-up portion is sandwiched between said strip apex and said second ply. The two-wheeled vehicle tire according to claim 1 or 2 , wherein the radially inner end of the second ply is positioned radially outwardly of the core. 4. The two-wheeled vehicle according to claim 3 , wherein the radially inner end of the second ply is positioned radially inwardly of the radially outer end of the flange of the regular rim when the tire is mounted on the regular rim. for tires. The tire for a two-wheeled vehicle according to any one of claims 1 to 4 , wherein the strip apex has a complex elastic modulus of 40 MPa or more and 100 MPa or less.

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