Tire for a motorized two-wheeled vehicle

Abstract

Provided is a motorcycle tire that improves wet performance and cornering performance. A motorcycle tire (1) includes a bias structure tire body (6), a crown belt layer (8) as a jointless crown belt ply (8A), and a tread rubber (9) disposed on the outer side in the tire radial direction of the crown belt layer (8). The tire body (6) includes an outer side tire body ply (12A). The 0°C tan δi of the tread rubber (9) in a crown region (Cr) is greater than the 0°C tan δo of the tread rubber (9) in a shoulder region (Sh). The angle (θc) of the tire body cord (10) of the outer side tire body ply (12A) in the crown region (Cr) is smaller than the angle (θs) of the tire body cord (10) of the outer side tire body ply (12A) in the shoulder region (Sh).

Description

TECHNICAL FIELD

[0001] The present application relates to a tire for a motorized two-wheeled vehicle. BACKGROUND

[0002] In the following Patent Literature 1, a tire for a two-wheeled vehicle is described, which divides the tread rubber of a tread portion into the tread rubber of a central portion and the tread rubber of a shoulder portion. In the tire for a two-wheeled vehicle, the ratio (tan δ1 / tan δ2) of the tangent of loss angle at 0°C (tan δ1) of the tread rubber of the central portion to the tangent of loss angle at 0°C (tan δ2) of the tread rubber of the shoulder portion is greater than 1.0. Thereby, the tire for a two-wheeled vehicle has high wet grip performance.

[0003] Patent Literature 1: International Publication No. 2017 / 204236

[0004] In recent years, in a tire for a motorized two-wheeled vehicle, it is desired to balance wet road performance and cornering performance, as a result of which, in the tire for a two-wheeled vehicle, there is room for improvement in cornering performance. SUMMARY

[0005] The present application is made in view of the above actual situation, and a main object thereof is to provide a tire for a motorized two-wheeled vehicle which improves wet road performance and cornering performance.

[0006] The invention described in Technical Solution 1 in the present application is a tire for a motorized two-wheeled vehicle, which includes: a tread portion; a pair of side portions; a pair of bead portions; a bias structure of a carcass which extends between the pair of bead portions; a crown layer which is disposed on the outside in the tire radial direction of the carcass and inside the tread portion; and a tread rubber which is disposed on the outside in the tire radial direction of the crown layer, the tread portion includes: a crown region which includes a tire equator; and a pair of shoulder regions which include both tread ends, the carcass includes a plurality of carcass plies which include a plurality of carcass cords, the carcass plies include an outside carcass ply which is disposed on the most outside in the tire radial direction, the crown layer is a jointless crown ply layer which includes crown cords which are disposed in a spiral shape at an angle of 5° or less with respect to the tire circumferential direction, the tangent of loss angle at 0°C (0°C tan δi) of the tread rubber in the crown region is greater than the tangent of loss angle at 0°C (0°C tan δo) of the tread rubber in each of the shoulder regions, and the angle θc of the carcass cords of the outside carcass ply in the crown region with respect to the tire circumferential direction is smaller than the angle θs of the carcass cords of the outside carcass ply in each of the shoulder regions with respect to the tire circumferential direction.

[0007] The tire for a motorized two-wheeled vehicle of the present application preferably has the angle of the carcass cords with respect to the tire circumferential direction of 20 degrees to 65 degrees.

[0008] The tire for a motorized two-wheeled vehicle of the present application preferably has each of the shoulder regions having a width of 20 mm or more on the tread surface from the tread end to the inside in the tire axial direction.

[0009] The tire for a motorized two-wheeled vehicle of the present application preferably has the tangent of the loss angle of the tread rubber at 70°C (70°C tan δi) in the crown region being smaller than the tangent of the loss angle of the tread rubber at 70°C (70°C tan δo) in the shoulder region.

[0010] The tire for a motorized two-wheeled vehicle of the present application preferably has the glass transition point of the tread rubber being -20°C to 5°C.

[0011] The tire for a motorized two-wheeled vehicle of the present application preferably has the glass transition point of the tread rubber in the crown region being smaller than the glass transition point of the tread rubber in the shoulder region.

[0012] The tire for a motorized two-wheeled vehicle of the present application preferably has the complex elastic modulus of the tread rubber at 0°C (0°C E*i) in the crown region being smaller than the complex elastic modulus of the tread rubber at 0°C (0°C E*o) in the shoulder region.

[0013] The tire for a motorized two-wheeled vehicle of the present application preferably has the ratio of the complex elastic modulus (0°C E*i) to the complex elastic modulus (0°C E*o) (0°C E*i / 0°C E*o) being 0.95 or less.

[0014] The tire for a motorized two-wheeled vehicle of the present application preferably has the ratio of the angle θc to the angle θs (θc / θs) being 0.35 to 0.90.

[0015] The tire for a motorized two-wheeled vehicle of the present application preferably has the tread rubber containing silica.

[0016] The tire for a motorized two-wheeled vehicle of the present application preferably has the outer side carcass ply being formed only by a main portion extending between the pair of bead portions.

[0017] The tire for a motorized two-wheeled vehicle of the present application preferably has the carcass ply including an inner side carcass ply disposed inside in the tire radial direction of the outer side carcass ply, the inner side carcass ply including a main portion extending between the bead core of each of the pair of bead portions and a pair of turn-back portions turned back from the inside in the tire axial direction to the outside around each of the bead cores.

[0018] The tire for a motorized two-wheeled vehicle of the present application, by adopting the above structure, is capable of exhibiting excellent wet performance and cornering performance. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1is a cross-sectional view showing one embodiment of a motorcycle tire according to the present application.

[0020] Figure 2 is Figure 1 an expanded view of the inside of the tread portion of

[0021] Explanation of Reference Numerals

[0022] 1: motorcycle tire; 6: carcass; 8: crown belt layer; 8A: jointless crown belt ply; 9: tread rubber; 10: carcass cord; 12A: outer side carcass ply; Cr: crown region; Sh: shoulder region. DETAILED DESCRIPTION

[0023] Hereinafter, one embodiment of the present application will be described based on the drawings.

[0024] Figure 1 is a tire meridian cross-sectional view including a tire rotation axis (omitted from the drawing) of a motorcycle tire 1 (hereinafter, sometimes simply referred to as "tire") in a normal state according to the present embodiment. The tire 1 according to the present embodiment is suitable for use in highway travel on dry asphalt pavement and the like, for example. However, the tire 1 according to the present application is not limited to such a mode.

[0025] The "normal state" refers to a state in which the tire 1 is assembled to a normal rim (not shown) and filled with a normal internal pressure without a load. Unless otherwise specified, the dimensions and the like of each portion of the tire are values measured in the normal state.

[0026] The "normal rim" refers to a rim that is prescribed for each tire according to a specification system including the specification to which the tire 1 is subjected, and is, for example, a standard rim if JATMA, "Design Rim" if TRA, or "Measuring Rim" if ETRTO.

[0027] The "normal internal pressure" refers to an air pressure determined for each specification according to a specification system including the specification to which the tire 1 is subjected, and is, for example, the highest air pressure if JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" if TRA, or "INFLATION PRESSURE" if ETRTO.

[0028] As shown in Figure 1 , the tire 1 according to the present embodiment curves the tread foot 2a of the tread portion 2 into a circular arc shape that protrudes to the outside in the tire radial direction in the tire meridian cross section. The tire 1 includes, for example, the tread portion 2, a pair of side portions 3, and a pair of bead portions 4.

[0029] In the present embodiment, the tread portion 2 includes a crown region Cr including a tire equator C, and a pair of shoulder regions Sh including both side tread ends Te. The crown region Cr extends, for example, to both sides in the tire axial direction from the tire equator C. The shoulder region Sh has, for example, a width Ws of 20 mm or more on the tread surface 2a from the tread end Te to the inner side in the tire axial direction. The width Ws is preferably 50% or less of the half of the tread development width TWe (shown in the drawing), for example. In the present embodiment, the shoulder region Sh is adjacent to the crown region Cr. The half of the tread development width TWe is the distance from the tire equator C to the tread end Te when the tread portion 2 is developed. Figure 2 The shoulder region Sh is adjacent to the crown region Cr. The half of the tread development width TWe is the distance from the tire equator C to the tread end Te when the tread portion 2 is developed.

[0030] A pair of side portions 3 are connected to both ends in the tire axial direction of the tread portion 2 and extend to the inner side in the tire radial direction. In the side portion 3 of the present embodiment, a side rubber 3G is provided. A pair of bead portions 4 are connected to each of the side portions 3 and extend to the inner side in the tire radial direction, for example. In each of the bead portions 4, a bead core 5 is embedded.

[0031] The tire 1 of the present embodiment includes a toroidal-shaped carcass 6 extending between the pair of bead portions 4, a crown belt layer 8 provided on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2, and a tread rubber 9 provided on the outer side in the tire radial direction of the crown belt layer 8.

[0032] Figure 2 is a developed view of the inside of the tread portion 2. As shown in the drawing, the carcass 6 of the present embodiment is of a bias construction. The bias construction refers to a construction in which a plurality of carcass cords 10 are inclined with respect to the tire circumferential direction. The carcass 6 is formed of a plurality of carcass plies 12 including the carcass cords 10 in the present embodiment. Figure 2

[0033] The carcass ply 12 of the present embodiment includes an outer carcass ply 12A provided on the outermost side in the tire radial direction. The angle θc of the carcass cords of the outer carcass ply 12A in the crown region Cr is smaller than the angle θs of the carcass cords of the outer carcass ply 12A in the shoulder region Sh. Thus, in the shoulder region Sh, which is the ground-contacting region during cornering, a larger side force is generated, and thus the cornering performance is improved.

[0034] ​The ratio of angle θc to angle θs (θc / θs) is preferably 0.35 to 0.90. This suppresses excessive increases in lateral resistance, maintains a light and agile handling feel in the motorized two-wheeled vehicle (hereinafter, sometimes referred to as "vehicle"), and thus provides excellent cornering performance. To effectively achieve this effect, the ratio (θc / θs) is further preferably 0.5 or more, and more preferably 0.75 or less. In this case, angle θc is the angle at the tire equator C, and angle θs is the angle located 20 mm inward from the tread end Te on the tread tread 2a towards the tire axial direction.

[0035] In this embodiment, the crown layer 8 is a seamless crown layer ply 8A, comprising crown cords 11 arranged in a spiral shape at an angle α of 5° or less relative to the tire circumference. This crown layer 8 suppresses tire outer diameter growth and improves high-speed stability during straight-line driving.

[0036] Although not specifically limited, the axial width Wa of the crown belt layer 8 is... Figure 1 (As shown) Preferably, the axial length TW of the tire between the tread ends Te and Te is 60% to 95%.

[0037] like Figure 1 As shown, the tread compound 9 is arranged, for example, across a pair of tread ends Te, Te. In this embodiment, the tread compound 9 forms the tread tread surface 2a. In this specification, the tread compound 9 in the crown region Cr is the crown rubber portion 13, and the tread compound 9 in the shoulder region Sh is the shoulder rubber portion 14. In this embodiment, the shoulder rubber portion 14 is adjacent to the sidewall compound 3G.

[0038] Generally, bias-ply tires 1 have superior cornering performance compared to radial tires, but their effectiveness is limited on wet roads. Furthermore, the air temperature is lower on wet roads than on dry roads. In this embodiment, the loss tangent (0°C tanδi) of the tread rubber portion 13 at 0°C is larger than the loss tangent (0°C tanδo) of the shoulder rubber portion 14 at 0°C. Therefore, wet road performance (especially wet braking performance) is improved in the tread area Cr, where there is a high chance of contact with the road during straight-line driving. In particular, the advantage of improved wet road performance lies in the bias-ply tire 1, which also exhibits excellent characteristics when driving on rough roads. Furthermore, since angle θs is larger than angle θc, the flexibility of the tire 1 is increased, the contact patch is larger, and therefore the lateral resistance is increased, particularly improving cornering performance in the bias-ply tire 1.

[0039] In the case where the loss tangent at 0°C (0°C tan δi) is excessively larger than the loss tangent at 0°C (0°C tan δo), the deformation of the crown region Cr during running increases, and the stability performance during high-speed running can be reduced. Also, the rigidity of the shoulder rubber portion 14 is excessively small, and the cornering performance can be deteriorated. Therefore, the loss tangent at 0°C (0°C tan δi) is preferably 0.2 or more, more preferably 0.4 or more, and preferably 1.0 or less, more preferably 0.7 or less, larger than the loss tangent at 0°C (0°C tan δo).

[0040] Generally, the motorized two-wheeled vehicle tilts during cornering. Also, in good conditions where the air temperature is high and the road surface is dry, the tilting can increase, and thus the grounding opportunity of the shoulder region Sh increases. Therefore, the loss tangent at 70°C (70°C tan δi) of the crown rubber portion 13 is smaller than the loss tangent at 70°C (70°C tan δo) of the shoulder rubber portion 14. Thus, during running on a dry asphalt road surface, the heat generation of the crown region Cr is suppressed, the stability performance during high-speed running is maintained at a high level, and the grounding performance during cornering running is improved, and the cornering performance is improved. In order to effectively exert the above effects, it is preferable that the loss tangent at 70°C (70°C tan δi) be 0.02 or more, more preferably 0.04 or more, and preferably 0.1 or less, more preferably 0.07 or less, smaller than the loss tangent at 70°C (70°C tan δo). Also, in order to manufacture such a crown rubber portion 13 and shoulder rubber portion 14, the carbon is added less to the crown rubber portion 13 than to the shoulder rubber portion 14.

[0041] In the present specification, the loss tangent and the complex elastic modulus are values measured by a viscoelastic spectrometer such as "EPLEXOR (registered trademark)" manufactured by GABO Co., Ltd. on the following conditions, using a test piece collected from the tread rubber 9 of the tire 1. The test piece has a shape of 20 mm in length, 4 mm in width, and 1 mm in thickness with the tire circumferential direction as the long side.

[0042] Frequency: 5 Hz

[0043] Initial tensile strain: 10%

[0044] Amplitude of dynamic strain: ±2.5%

[0045] The glass transition point Tg of the tread rubber 9 is preferably -20°C to 5°C. Since the glass transition point Tg of the tread rubber 9 is -20°C or higher, the wet braking performance can be improved. Since the glass transition point Tg of the tread rubber 9 is 5°C or lower, excessive deformation during running is suppressed, and the cornering performance and the stability during high-speed running are improved. The glass transition point is a value determined by using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan (KK) while increasing the temperature at a rate of 10°C / minute. In order to produce such a crown rubber portion 13 and shoulder rubber portion 14, an aromatic petroleum resin is added.

[0046] The glass transition point Tgl of the crown rubber portion 13 is preferably lower than the glass transition point Tg2 of the shoulder rubber portion 14. Since the glass transition point Tgl of the crown rubber portion 13 is lower than the glass transition point Tg2 of the shoulder rubber portion 14, the wet braking performance in the crown region Cr can be maintained. Also, in the shoulder region Sh, the cornering performance is improved by the improvement in the ground contact property due to the deformation of the shoulder rubber portion 14. In order to produce such a crown rubber portion 13 and shoulder rubber portion 14, the crown rubber portion 13 is added with less aromatic petroleum resin than the shoulder rubber portion 14.

[0047] In order to effectively exert the above-described effects, the difference between the glass transition points of the crown rubber portion 13 and the shoulder rubber portion 14 (Tg2-Tgl) is preferably 3°C or higher, more preferably 5°C or higher, and is preferably 10°C or lower, more preferably 8°C or lower.

[0048] The complex modulus at 0°C (0°C E*i) of the crown rubber portion 13 is lower than the complex modulus at 0°C (0°C E*o) of the shoulder rubber portion 14. Thereby, the wet performance and the cornering performance can be balanced at a high level. The complex modulus at 0°C (0°C E*i) is, for example, preferably 5 MPa or more, more preferably 10 MPa or more, and is preferably 20 MPa or less, more preferably 15 MPa or less, lower than the complex modulus at 0°C (0°C E*o). In order to produce such a crown rubber portion 13 and shoulder rubber portion 14, the crown rubber portion 13 is added with more oil than the shoulder rubber portion 14.

[0049] In order to exert the above-described effects, the ratio of the complex modulus at 0°C (0°C E*i) to the complex modulus at 0°C (0°C E*o) (0°C E*i / 0°C E*o) is preferably 0.95 or lower. When the ratio (0°C E*i / 0°C E*o) is too low, the wet performance can deteriorate. Therefore, the ratio (0°C E*i / 0°C E*o) is preferably 0.75 or more, more preferably 0.80 or more, and more preferably 0.90 or lower.

[0050] In this embodiment, the tread compound 9 contains silica. Silica increases the adhesion of the silanol-based tread compound 9 to the wet road surface, thereby improving wet braking performance. The silica content is preferably 80% by mass or more.

[0051] The mass percentage of silica in the crown rubber portion 13 is preferably greater than that in the shoulder rubber portion 14. The silica content of the crown rubber portion 13 is preferably 3% or more by mass, more preferably 5% or more by mass, more preferably 10% or less by mass, and more preferably 8% or less by mass.

[0052] like Figure 2 As shown, the carcass ply 12 further includes, for example, an inner carcass ply 12B disposed inside the outer carcass ply 12A in the tire radial direction. The carcass cords 10 of the outer carcass ply 12A and the carcass cords 10 of the inner carcass ply 12B intersect in the tire radial direction. The angle θ of the carcass cords 10 of each carcass ply 12A, 12B gradually increases, for example, from the tire equator C toward the tread ends Te on both sides.

[0053] The angle θ of the carcass cord 10 relative to the tire circumference is preferably 20 to 65 degrees. This generates greater camber thrust, thus improving cornering performance. Angle θ is more preferably 30 degrees or more, and more preferably 55 degrees or less. In this embodiment, the carcass cord 10 is composed of organic fiber cords.

[0054] like Figure 1 As shown, in this embodiment, the outer carcass ply 12A is formed solely by the main portion 15 extending between a pair of bead portions 4. Because this outer carcass ply 12A suppresses excessive lateral bounce of the tire 1, it improves cornering performance and ride comfort.

[0055] The inner carcass ply 12B includes, for example, a main body portion 16a extending between the bead cores 5, 5 and a pair of folded portions 16b that fold back from the inside to the outside of the tire axial direction around the bead core 5. Such an inner carcass ply 12B exhibits excellent stability at high speeds.

[0056] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific embodiments described above, and can be implemented in various ways.

[0057]

Example

[0058] A prototype with Figure 1 These are tires for motorized two-wheeled vehicles with a basic construction. Furthermore, the cornering and wet-road performance of each test tire was tested. The common specifications and testing methods for each test tire are as follows.

[0059] Cornering performance

[0060] The test driver made the test vehicle equipped with the test tire travel on a test course of dry asphalt pavement. After the travel, the test driver evaluated the easiness of turning, stability by sense organ. The evaluation was performed by 10-point scale. As a result, the larger the value, the more excellent.

[0061] Tire for front wheel (size, rim, internal pressure): 110 / 70-13 M / C, 13 x 3.00 MT, 200 kPa

[0062] Tire for rear wheel (size, rim, internal pressure): 130 / 70-13 M / C, 13 x 3.50 MT, 220 kPa

[0063] Test vehicle: motor two-wheeled vehicle with displacement of 250 cc

[0064] <Wet road performance>

[0065] The test driver measured the moving distance at the time of deceleration when traveling on a wet asphalt pavement using the above vehicle. The evaluation was expressed by an index of the reciprocal of the moving distance of Comparative Example 1 being 100. As a result, the larger the value, the more excellent.

[0066] Moving distance: the distance from the time of 40 km / h to the time of 10 km / h by working the brake is shown in Table 1.

[0067] [Table 1]

[0068]

[0069] From the test results, it was found that the tires of the Examples had excellent wet road performance and turning performance.

Claims

1. A tire for a motorized two-wheeled vehicle, comprising: a tread portion; a pair of sidewall portions; a pair of bead portions; a bias structure of a carcass extending between the pair of bead portions; a crown layer disposed outside in a tire radial direction of the carcass and inside of the tread portion; and a tread rubber disposed outside in a tire radial direction of the crown layer, the tread portion comprising: a crown region including a tire equator; and a pair of shoulder regions including both side tread ends, the carcass comprising a plurality of carcass plies including a plurality of carcass cords, the carcass plies including an outside carcass ply disposed most outside in a tire radial direction, the crown layer being a jointless crown ply layer including crown cords disposed in a spiral shape at an angle of 5° or less with respect to a tire circumferential direction, a tangent loss at 0°C of the tread rubber in the crown region 0°C tan δi being greater than a tangent loss at 0°C of the tread rubber in each of the shoulder regions 0°C tan δo, an angle θc of the carcass cords of the outside carcass ply with respect to a tire circumferential direction in the crown region being smaller than an angle θs of the carcass cords of the outside carcass ply with respect to a tire circumferential direction in each of the shoulder regions, the tread rubber including a crown rubber portion of the crown region and a shoulder rubber portion of the shoulder region, the tread rubber including silica, a mass % of silica of the crown rubber portion being greater than a mass % of silica of the shoulder rubber portion, a tangent loss at 70°C of the tread rubber in the crown region 70°C tan δi being smaller than a tangent loss at 70°C of the tread rubber in the shoulder region 70°C tan δo, a glass transition point of the tread rubber in the crown region being smaller than a glass transition point of the tread rubber in the shoulder region, a complex elastic modulus at 0°C of the tread rubber in the crown region 0°C E*i being smaller than a complex elastic modulus at 0°C of the tread rubber in the shoulder region 0°C E*o.

2. The tire for a motorized two-wheeled vehicle according to claim 1, wherein, an angle of the carcass cords with respect to a tire circumferential direction is 20 degrees to 65 degrees.

3. The tire for a motorized two-wheeled vehicle according to claim 1 or 2, wherein, each of the shoulder regions has a width of 20 mm or more on a tread surface from the tread end to an inside in a tire axial direction.

4. The tire for a motorized two-wheeled vehicle according to claim 1 or 2, wherein, a glass transition point of the tread rubber is -20°C to 5°C.

5. The tire for a motorized two-wheeled vehicle according to claim 1 or 2, wherein, a ratio 0°C E*i / 0°C E*o of the complex elastic modulus at 0°C 0°C E*i to the complex elastic modulus at 0°C 0°C E*o is 0.95 or less.

6. The tire for a motorized two-wheeled vehicle according to claim 1 or 2, wherein, a ratio θc / θs of the angle θc to the angle θs is 0.35 to 0.

90.

7. The tire for a motorized two-wheeled vehicle according to claim 1 or 2, wherein, the outside carcass ply is formed only by a main portion extending between the pair of bead portions. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 8. The motorcycle tire according to claim 1 or 2, wherein the carcass ply includes an inner carcass ply disposed on an inner side in a tire radial direction of the outer carcass ply, the inner carcass ply includes: a main body portion extending between the bead core of each of the pair of bead portions; and a pair of turn-back portions turned back from an inner side to an outer side in a tire axial direction around each of the bead cores.

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