Motorcycle tires

Abstract

To provide a tire for a motor cycle improved in wet performance and steering performance.SOLUTION: A tire for a motor cycle includes a carcass 6 having a bias structure, a band layer 8 which is a jointless band ply 8A, and a tread rubber arranged outside in a tire radial direction of the band layer 8. The carcass 6 includes an outer carcass ply 12A. 0°Ctanδi of the tread rubber in a crown region Cr is larger than 0°Ctanδo of the tread rubber in a shoulder region Sh. An angle θc of a carcass cord 10 of the outer carcass ply 12A in the crown region Cr is smaller than an angle θs of the carcass cord 10 of the outer carcass ply 12A in the shoulder region Sh.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tire for a motorcycle. [Background technology]

[0002] Patent Document 1 listed below describes a motorcycle tire in which the tread rubber of the tread portion is divided into a center portion tread rubber and a shoulder portion tread rubber. In this motorcycle tire, the ratio (tan δ1 / tan δ2) of the loss tangent (tan δ1) of the center portion tread rubber at 0°C to the loss tangent (tan δ2) of the shoulder portion tread rubber at 0°C is set to be greater than 1.0. This is said to give the motorcycle tire excellent wet grip performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 204236 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for motorcycle tires that offer both wet performance and cornering performance, but there is still room for improvement in the cornering performance of motorcycle tires.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a motorcycle tire having improved wet performance and cornering performance. [Means for solving the problem]

[0006] The invention of claim 1 of the present invention is a tire for motorcycles, comprising: a tread portion; a pair of sidewall portions; a pair of bead portions; a bias-structured carcass extending between the pair of bead portions; a band layer disposed radially outward of the carcass and within the tread portion; and a tread rubber disposed radially outward of the band layer, the tread portion comprising a crown region including the tire equator and a pair of shoulder regions including both tread edges, the carcass comprising a plurality of carcass plies including a plurality of carcass cords, the carcass ply comprising an outer ply disposed radially outward of the outer ply, The motorcycle tire includes a carcass ply, the band layer being a jointless band ply including band cords spirally arranged at an angle of 5° or less with respect to the tire circumferential direction, the loss tangent at 0°C (0°C tan δi) of the tread rubber in the crown region being larger than the loss tangent 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 outer 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 outer carcass ply with respect to the tire circumferential direction in each of the shoulder regions.

[0007] In the motorcycle tire according to the present invention, the angle of the carcass cord with respect to the circumferential direction of the tire is preferably 20 to 65 degrees.

[0008] In the motorcycle tire according to the present invention, it is preferable that each of the shoulder regions has a width of 20 mm or more on the tread surface from the tread end toward the inside in the tire axial direction.

[0009] In the motorcycle tire according to the present invention, it is desirable that the loss tangent at 70°C (70°C tanδi) of the tread rubber in the crown region is smaller than the loss tangent at 70°C (70°C tanδo) of the tread rubber in the shoulder region.

[0010] In the motorcycle tire according to the present invention, the glass transition point of the tread rubber is preferably from -20 to 5°C.

[0011] In the motorcycle tire according to the present invention, it is desirable that the glass transition temperature of the tread rubber in the crown region is lower than the glass transition temperature of the tread rubber in the shoulder region.

[0012] In the motorcycle tire according to the present invention, it is desirable that the complex modulus of elasticity at 0°C (0°C E*i) of the tread rubber in the crown region is smaller than the complex modulus of elasticity at 0°C (0°C E*o) of the tread rubber in the shoulder region.

[0013] In the motorcycle tire according to the present invention, it is desirable that the ratio (0°C E*i / 0°C E*o) of the complex elastic modulus (0°C E*i) to the complex elastic modulus (0°C E*o) is 0.95 or less.

[0014] In the motorcycle tire according to the present invention, it is desirable that the ratio (θc / θs) of the angle θc to the angle θs is 0.35 to 0.90.

[0015] In the motorcycle tire according to the present invention, the tread rubber preferably contains silica.

[0016] In the motorcycle tire according to the present invention, it is preferable that the outer carcass ply is formed only by a main portion extending between a pair of bead portions.

[0017] In the motorcycle tire according to the present invention, it is desirable that the carcass ply includes an inner carcass ply arranged radially inward of the outer carcass ply, and that the inner carcass ply includes a main body portion extending between bead cores embedded in each of a pair of bead portions, and a pair of turn-up portions turned back around each bead core from the inside to the outside in the tire axial direction. [Effects of the Invention]

[0018] The motorcycle tire of the present invention employs the above-described configuration, and is therefore able to exhibit excellent wet performance and cornering performance. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view showing an embodiment of a motorcycle tire of the present invention. [Figure 2] FIG. 2 is a development view of the inside of the tread portion of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0020] An embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a tire meridian cross-sectional view including the tire rotation axis (not shown) of a motorcycle tire 1 (hereinafter sometimes simply referred to as "tire") according to this embodiment in a normal state. The tire 1 according to this embodiment is suitable for use, for example, in on-road driving on dry asphalt roads. However, the tire 1 of the present invention is not limited to this embodiment.

[0021] The "normal state" refers to a state in which the tire 1 is mounted on a normal rim (not shown), inflated to a normal internal pressure, and no load is applied. Unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal state.

[0022] A "genuine rim" is a rim that is defined for each tire by a standard system that includes the standard on which tire 1 is based, such as a standard rim in the case of JATMA, a "Design Rim" in the case of TRA, or a "Measuring Rim" in the case of ETRTO.

[0023] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which tire 1 is based. In the case of JATMA, it is the maximum air pressure, in the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is "INFLATION PRESSURE".

[0024] 1, in a tire 1 of this embodiment, a tread surface 2a of a tread portion 2 is curved in an arc shape that is convex outward in the tire radial direction in a tire meridian cross section. The tire 1 includes, for example, the tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4.

[0025] In this embodiment, the tread portion 2 includes a crown region Cr including the tire equator C and a pair of shoulder regions Sh including both tread edges Te. The crown region Cr extends, for example, to both sides in the tire axial direction with the tire equator C as its center. The shoulder regions Sh have a width Ws of, for example, 20 mm or more on the tread surface 2a from the tread edge Te to the tire axially inward. The width Ws is preferably, for example, 50% or less of the half tread developed width TWe (shown in FIG. 2). In this embodiment, the shoulder regions Sh are adjacent to the crown region Cr. The half tread developed width TWe is the distance from the tire equator C to the tread edge Te when the tread portion 2 is developed.

[0026] The pair of sidewall portions 3 are connected to both ends of the tread portion 2 in the tire axial direction and extend radially inward of the tire. In this embodiment, a sidewall rubber 3G is arranged in the sidewall portion 3. Each of the pair of bead portions 4 is connected to each sidewall portion 3, for example, and extends radially inward of the tire. A bead core 5 is embedded in each bead portion 4.

[0027] The tire 1 of this embodiment includes a toroidal carcass 6 extending between a pair of bead portions 4, a band layer 8 arranged radially outside the carcass 6 and inside the tread portion 2, and a tread rubber 9 arranged radially outside the band layer 8.

[0028] Fig. 2 is a development view of the inside of the tread portion 2. As shown in Fig. 2, the carcass 6 of this embodiment has a bias structure. The bias structure is a structure in which a plurality of carcass cords 10 are inclined with respect to the tire circumferential direction. In this embodiment, the carcass 6 is formed of a plurality of carcass plies 12 including the carcass cords 10.

[0029] The carcass ply 12 of this embodiment includes an outer carcass ply 12A disposed radially outermost in the tire. 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. This allows a large cornering force to be generated in the shoulder region Sh that comes into contact with the ground during cornering, improving cornering performance.

[0030] The ratio (θc / θs) of the angle θc to the angle θs is preferably 0.35 to 0.90. This suppresses an excessive sudden increase in cornering force, maintaining a light and responsive feel when leaning the motorcycle (hereinafter sometimes referred to as "vehicle"), thereby achieving excellent cornering performance. To effectively achieve this effect, the ratio (θc / θs) is more preferably 0.5 or more, and even more preferably 0.75 or less. In this case, the angle θc is the angle on the tire equator C, and the angle θs is the angle at a position 20 mm axially inward on the tread surface 2a from the tread edge Te.

[0031] The band layer 8 of this embodiment is a jointless band ply 8A including band cords 11 spirally arranged at an angle α of 5° or less with respect to the tire circumferential direction. Such a band layer 8 suppresses growth of the tire outer diameter and improves high-speed stability during straight running.

[0032] Although not particularly limited, the width Wa (shown in FIG. 1) of the band layer 8 in the tire axial direction is preferably 60% to 95% of the length TW between the tread ends Te, Te in the tire axial direction.

[0033] As shown in Fig. 1, the tread rubber 9 is disposed, for example, so as to straddle a pair of tread ends Te, Te. In this embodiment, the tread rubber 9 forms the tread surface 2a. In this specification, the tread rubber 9 in the crown region Cr is referred to as a crown rubber portion 13, and the tread rubber 9 in the shoulder region Sh is referred to as a shoulder rubber portion 14. In this embodiment, the shoulder rubber portion 14 is adjacent to the sidewall rubber 3G.

[0034] Generally, bias-structured tires 1 have superior cornering performance compared to so-called radial-structured tires, but this effect is less pronounced on wet roads. Furthermore, the air temperature is lower on wet roads than on dry roads. In this embodiment, the loss tangent (0°C tan δi) of the crown rubber portion 13 at 0°C is set larger than the loss tangent (0°C tan δo) of the shoulder rubber portion 14 at 0°C. This improves wet performance (especially wet braking performance) in the crown region Cr, which often comes into contact with the ground during straight driving, etc. In particular, the bias-structured tire 1, which also excels in rough road driving, offers significant benefits in terms of improving wet performance. Furthermore, because the angle θs is larger than the angle θc, the flexibility of the tire 1 is improved and the contact patch is larger, which increases cornering force and improves cornering performance, particularly in bias-structured tires 1.

[0035] If the loss tangent (0°C tanδi) is excessively larger than the loss tangent (0°C tanδo), deformation of the crown region Cr during driving may become large, which may reduce stability during high-speed driving. Furthermore, the rigidity of the shoulder rubber portion 14 may become excessively small, which may result in poor cornering performance. Therefore, the loss tangent (0°C tanδi) is preferably larger than the loss tangent (0°C tanδo) by 0.2 or more, more preferably by 0.4 or more, more preferably by 1.0 or less, and even more preferably by 0.7 or less.

[0036] Generally, motorcycles roll during cornering. Under favorable conditions, such as high temperatures and dry road surfaces, the roll can be increased, increasing the chances of the shoulder region Sh coming into contact with the ground. For this reason, the loss tangent (70°C tan δi) of the crown rubber portion 13 at 70°C is set smaller than the loss tangent (70°C tan δo) of the shoulder rubber portion 14 at 70°C. This suppresses heat generation in the crown region Cr when traveling on dry asphalt roads, maintaining high stability during high-speed traveling, and enhancing ground contact during cornering, improving cornering performance. To effectively achieve the above-mentioned effects, the loss tangent (70°C tan δi) is preferably at least 0.02 smaller than the loss tangent (70°C tan δo), more preferably at least 0.04 smaller, more preferably at most 0.1, and even more preferably at most 0.07. In order to manufacture such crown rubber portion 13 and shoulder rubber portion 14, the crown rubber portion 13 is added with less carbon than the shoulder rubber portion 14.

[0037] In this specification, the loss tangent and the complex modulus are values ​​measured under the following conditions using a viscoelasticity spectrometer such as "IPLEXER (registered trademark)" manufactured by GABO Corporation on a test specimen taken from the tread rubber 9 of the tire 1. The test specimen has a shape of 20 mm in length, 4 mm in width, and 1 mm in thickness, with the long side extending in the tire circumferential direction. Frequency: 5Hz Initial extension strain: 10% Dynamic strain amplitude: ±2.5%

[0038] The glass transition temperature Tg of the tread rubber 9 is preferably -20 to 5°C. Since the glass transition temperature Tg of the tread rubber 9 is -20°C or higher, wet braking performance can be improved. Since the glass transition temperature Tg of the tread rubber 9 is 5°C or lower, excessive deformation during driving is suppressed, improving cornering performance and stability during high-speed driving. The glass transition temperature is a value measured in accordance with JIS-K7121 using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan, Inc., while increasing the temperature at a rate of 10°C / min. An aromatic petroleum resin is added to manufacture the crown rubber portion 13 and shoulder rubber portion 14.

[0039] The glass transition temperature Tg1 of the crown rubber portion 13 is preferably lower than the glass transition temperature Tg2 of the shoulder rubber portions 14. Because the glass transition temperature Tg1 of the crown rubber portion 13 is lower than the glass transition temperature Tg2 of the shoulder rubber portions 14, wet braking performance is maintained in the crown region Cr. Furthermore, in the shoulder regions Sh, cornering performance is improved by improving ground contact due to deformation of the shoulder rubber portions 14. Note that, in order to manufacture such crown rubber portion 13 and shoulder rubber portions 14, less aromatic petroleum resin is added to the crown rubber portion 13 than to the shoulder rubber portions 14.

[0040] In order to effectively exert the above-mentioned effects, the difference in glass transition point (Tg2-Tg1) between the crown rubber portion 13 and the shoulder rubber portion 14 is preferably 3°C or more, more preferably 5°C or more, and is preferably 10°C or less, and more preferably 8°C or less.

[0041] The complex modulus of elasticity at 0°C (0°C E*i) of the crown rubber portion 13 is set smaller than the complex modulus of elasticity at 0°C (0°C E*o) of the shoulder rubber portions 14. This allows for high levels of both wet performance and cornering performance. The complex modulus of elasticity (0°C E*i) is preferably small at, for example, 5 MPa or more, more preferably small at, for example, 10 MPa or more, more preferably small at, for example, 20 MPa or less, and even more preferably small at, for example, 15 MPa or less. In order to manufacture such crown rubber portion 13 and shoulder rubber portion 14, more oil is added to the crown rubber portion 13 than to the shoulder rubber portion 14.

[0042] In order to achieve the above-mentioned effects, the ratio (0°C E*i / 0°C E*o) of the complex elastic modulus (0°C E*i) to the complex elastic modulus (0°C E*o) is preferably 0.95 or less. However, if the ratio (0°C E*i / 0°C E*o) is too small, wet performance may 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 less.

[0043] In this embodiment, the tread rubber 9 contains silica. Silica increases the adhesive force between the tread rubber 9 and a wet road surface due to silanol groups, thereby improving wet braking performance. The silica content is preferably 80 mass % or more.

[0044] The mass % of silica in the crown rubber portion 13 is preferably greater than the mass % of silica in the shoulder rubber portions 14. The mass % of silica in the crown rubber portion 13 is preferably 3 mass % or more of the silica in the shoulder rubber portions 14, more preferably 5 mass % or more, and is preferably 10 mass % or less, more preferably 8 mass % or less.

[0045] 2, the carcass ply 12 further includes, for example, an inner carcass ply 12B disposed radially inward of the outer carcass ply 12A. The carcass cords 10 of the outer carcass ply 12A and the carcass cords 10 of the inner carcass ply 12B cross each other radially inward and outward. The angle θ of the carcass cords 10 of each carcass ply 12A, 12B gradually increases from the tire equator C toward both tread edges Te.

[0046] The angle θ of the carcass cord 10 with respect to the tire circumferential direction is preferably 20 to 65 degrees. This allows a large camber thrust to be generated, thereby improving cornering performance. The angle θ is more preferably 30 degrees or more, and more preferably 55 degrees or less. In this embodiment, the carcass cord 10 is made of organic fiber cord.

[0047] 1, in this embodiment, the outer carcass ply 12A is formed only by a main portion 15 extending between a pair of bead portions 4. Such an outer carcass ply 12A prevents the lateral spring of the tire 1 from becoming excessively high, thereby improving cornering performance and ride comfort.

[0048] The inner carcass ply 12B includes, for example, a main body portion 16a extending between the bead cores 5, 5, and a pair of turned-up portions 16b turned up from the inside to the outside in the tire axial direction around the bead core 5. Such an inner carcass ply 12B has excellent stability performance during high-speed running.

[0049] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above specific embodiments and can be modified and implemented in various ways. [Example]

[0050] Motorcycle tires were prototyped with the basic structure shown in Figure 1. The cornering performance and wet performance of each sample tire were then tested. The common specifications and test methods for each sample tire are as follows:

[0051] <Turning performance> A test rider drove a test vehicle fitted with a sample tire on a test course with a dry asphalt surface. After the run, the test rider sensorily evaluated the ease of cornering and stability. The evaluation was made on a 10-point scale with 10 being the maximum score. The higher the score, the better the result. Front tire (size, rim, internal pressure): 110 / 70-13M / C, 13 x 3.00MT, 200kPa Rear tire (size, rim, internal pressure): 130 / 70-13M / C, 13 x 3.50MT, 220kPa Test vehicle: 250cc motorcycle

[0052] <Wet performance> A test rider used the vehicle to measure the distance traveled during deceleration while driving on a wet asphalt road surface. The evaluation is expressed as an index, with the reciprocal of the distance traveled in Comparative Example 1 set to 100. The higher the numerical value, the better the result. Distance traveled: Distance traveled when braking from 40 km / h to 10 km / h The test results are shown in Table 1.

[0053] [Table 1]

[0054] As a result of the test, it is understood that the tires of the examples have excellent wet performance and cornering performance. [Explanation of symbols]

[0055] 1. Motorcycle tires 6. Carcass 8 Band Layer 8A Jointless Band Ply 9 Tread rubber 10 Carcass Cord 12A outer carcass ply Cr Crown region Sh Shoulder region

Claims

1. A tire for a motorcycle, A tread portion; A pair of sidewall portions; a pair of bead portions; a bias structure carcass extending between the pair of bead portions; a band layer disposed on the outer side of the carcass in the tire radial direction and inside the tread portion; a tread rubber disposed on the outer side of the band layer in the tire radial direction, The tread portion includes a crown region including a tire equator and a pair of shoulder regions including tread edges on both sides, The carcass includes a plurality of carcass plies including a plurality of carcass cords, The carcass plies include an outer carcass ply disposed outermost in the tire radial direction, the band layer is a jointless band ply including a band cord spirally arranged at an angle of 5° or less with respect to the tire circumferential direction, a loss tangent at 0°C (0°C tanδi) of the tread rubber in the crown region is greater than a loss tangent at 0°C (0°C tanδo) of the tread rubber in each shoulder region, an angle θc of the carcass cord of the outer carcass ply in the crown region with respect to the tire circumferential direction is smaller than an angle θs of the carcass cord of the outer carcass ply in each shoulder region with respect to the tire circumferential direction, the tread rubber includes a crown rubber portion in the crown region and a shoulder rubber portion in the shoulder region, The tread rubber contains silica, the mass% of silica in the crown rubber portion is greater than the mass% of silica in the shoulder rubber portion, a loss tangent at 70°C (70°C tanδi) of the tread rubber in the crown region is smaller than a loss tangent at 70°C (70°C tanδo) of the tread rubber in the shoulder region; Tires for motorcycles.

2. 2. The motorcycle tire according to claim 1, wherein the angle of the carcass cord with respect to the tire circumferential direction is 20 to 65 degrees.

3. 3. The motorcycle tire according to claim 1, wherein each of the shoulder regions has a width of 20 mm or more that increases on the tread surface from the tread end toward the tire axially inward.

4. A motorcycle tire as described in any one of claims 1 to 3, wherein the glass transition temperature of the tread rubber is -20 to 5°C.

5. A motorcycle tire as described in any one of claims 1 to 4, wherein the glass transition point of the tread rubber in the crown region is lower than the glass transition point of the tread rubber in the shoulder region.

6. A motorcycle tire described in any one of claims 1 to 5, wherein the complex modulus of elasticity at 0°C (0°C E*i) of the tread rubber in the crown region is smaller than the complex modulus of elasticity at 0°C (0°C E*o) of the tread rubber in the shoulder region.

7. A motorcycle tire as described in claim 6, wherein the ratio (0°C E*i / 0°C E*o) of the complex elastic modulus (0°C E*i) to the complex elastic modulus (0°C E*o) is 0.95 or less.

8. A motorcycle tire described in any one of claims 1 to 7, wherein the ratio (θc / θs) of the angle θc to the angle θs is 0.35 to 0.

90.

9. A motorcycle tire as described in any one of claims 1 to 8, wherein the outer carcass ply is formed only by a main portion extending between the pair of bead portions.

10. The carcass ply includes an inner carcass ply arranged radially inward of the outer carcass ply, 10. The motorcycle tire according to claim 1, wherein the inner carcass ply includes a main body portion extending between bead cores embedded in a pair of bead portions, and a pair of turn-up portions turned back around each of the bead cores from the inside to the outside in the tire axial direction.

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