JP6523138B2 - Pneumatic radial tire for motorcycles - Google Patents

Description

  The present invention relates to a pneumatic radial tire for a motorcycle (hereinafter, also simply referred to as a "tire"), and more specifically, a pneumatic radial for a motorcycle suitable for heavy vehicles, having both durability and wet grip highly compatible. It relates to the tire.

  In recent years, motorcycles in categories such as touring and sports have been increasing in size. Such a tire for a motorcycle is required to ensure running stability and grip performance at cornering and high speed stability at straight running. In particular, for the rear tire which is a driving tire to which a large torque is applied, improvement of the performance is required. For example, Patent Document 1 can be cited as a technique for improving the high-speed stability of a motorcycle tire during straight running, the running stability during cornering, and the grip performance.

  Specifically, in Patent Document 1, a motorcycle tire having a carcass comprising three or four carcass plies and a spiral belt layer on the outer side of the carcass in the tire radial direction is disclosed. , Where L is the distance from the tire equator to the tread end and B is the distance from the tire equatorial plane to the end of the spiral belt layer, the distance B is within the range of 0.5 L to 0.8 L Motorcycle tires have been proposed.

JP, 2009-126422, A

  However, with the increase in size of motorcycles, the load applied to the tire is becoming heavier, and a tire used for a heavy vehicle is required to have improved durability. However, it is difficult to simultaneously achieve both durability and wet grip of a tire used for a heavy-duty vehicle, and at present there is a demand for a technique for achieving both of these in a highly compatible manner.

  Therefore, an object of the present invention is to provide a pneumatic radial tire for a motorcycle suitable for heavy vehicles, which has both durability and wet grip properties.

  As a result of intensive studies to solve the above problems, the inventor of the present invention has achieved the above problems by setting the configuration of the carcass and the configuration of the tread portion as follows in a radial tire for a motorcycle having a spiral belt layer. It has been found that it can be eliminated, and the present invention has been completed.

That is, in the pneumatic radial tire for a motorcycle according to the present invention, a pair of bead portions in which a bead core is embedded, a pair of sidewall portions extending outward from the bead portion in the tire radial direction, and a pair of sidewall portions A spiral belt having a tread portion extending across, a carcass including at least four or more radial carcass plies, and an angle of 0 to 5 ° with respect to a tire circumferential direction of the tread portion disposed outside the tire radial direction of the carcass A pneumatic radial tire for a motorcycle comprising:
At least two turn-up plies in which the at least four or more radial carcass plies are wound outward from the inside in the tire width direction of the bead core, and at least two down plies in which the bead core is terminated without being wound up; Consists of
When the distance from the tire equator to the tread end along the surface of the tread portion is L, and the tread portion is a center region including the tire equator in the tire width direction and a shoulder region outside the center region in the width direction, The division position of the center area and the shoulder area is in the range from 0.12 L to 0.22 L from the tire equator, and the hardness Hd (c) of the rubber of the center area is from the Hd (s) of the rubber of the shoulder area Is also characterized by a large size. Here, the distance L is a value measured in a normal internal pressure specified by JATMA and in a no-load state.

  In the tire according to the present invention, preferably, tan δ (c) of the rubber in the center region is 0.2 to 0.35, and tan δ (s) of the shoulder region is 0.35 to 0.85. Moreover, in the tire according to the present invention, it is preferable that the Hd (c) is 60 to 70, and the Hd (s) is 50 to 60. Furthermore, in the tire according to the present invention, it is preferable that the turn-up ply is two and the down ply is two. Here, the hardness of the rubber of the tread portion is Shore A hardness, and tan δ is measured under the conditions of a temperature of 0 ° C., a strain amplitude of 1% and a frequency of 52 Hz in accordance with JIS K7198. It is a value obtained by dividing by the dynamic storage modulus.

  According to the present invention, it is possible to provide a pneumatic radial tire for a motorcycle suitable for heavy vehicles, which has both durability and wet grip properties.

FIG. 1 is a cross-sectional view in the tire width direction of a pneumatic radial tire for a motorcycle according to a preferred embodiment of the present invention. FIG. 8 is a cross-sectional view of a pneumatic radial tire for a motorcycle according to Conventional Example 1 in the tire width direction.

Hereinafter, the pneumatic tire of the present invention will be described in detail using the drawings.
FIG. 1 is a cross-sectional view in the tire width direction of a pneumatic radial tire for a motorcycle according to a preferred embodiment of the present invention. As illustrated, the tire 10 of the present invention includes a pair of bead portions 1, a pair of sidewall portions 2 extending outward from the bead portion 1 in the tire radial direction, and a tread portion extending across the pair of sidewall portions 2 3 and a carcass 4 consisting of at least four (four in the illustrated example) radial carcass plies 4a to 4d for reinforcing these portions, and the carcass 4 in the tread portion 3 is provided on the outer side in the tire radial direction A spiral belt layer 5 having an angle of 0 to 5 ° with respect to the tire circumferential direction is disposed. The spiral belt layer 5 sufficiently enhances the bending rigidity of the tread installation area at the time of straight running and improves the high speed stability. In the tire 10 of the present invention, the width of the spiral belt layer 5 is L, where L is the distance from the tire equator to the tread end along the surface of the tread portion 3 in order to obtain the desired effect. About 0.5 L to 0.8 L from the equator E is preferable.

  In the tire 10 of the present invention, the carcass 4 comprises at least four or more radial carcass plies, and at least four or more radial carcass plies are at least two sheets wound up from the inside in the tire width direction of the bead core 6 to the outside. A turn-up ply (4a, 4b in the illustrated example), and at least two down plies extending from one sidewall section 2 to the other sidewall section 2 and terminating without being wound up on the bead core 6 (illustrated example In 4c and 4d). In the illustrated example, the down plies 4c, 4d are terminated between the main portion and the folded portion of the turnup plies 4a, 4b, and in the illustrated example, the radial carcass plies 4a, 4b, 4c and 4d The ends terminate at different positions in the tire radial direction. Moreover, in the example of illustration, the edge part of down ply 4c, 4d is terminated between the main-body part of turn-up ply 4a, 4b, and the bead filler 7. FIG. With such a structure of the down plies 4c, 4d, the durability of the tire is improved.

  In general, in tires for motorcycles, large distortion occurs in the carcass ply when heavy load is applied, and the fibers of the reinforcing cords of the carcass ply are subjected to compressive stress in the longitudinal direction, and CBU (carcass ply cutting) occurs due to cord fatigue. Resulting in. In order to improve the durability to this CBU, it is effective to increase the number of carcass plies to disperse the distortion. Therefore, in the tire 10 of the present invention, at least four radial carcass plies are provided.

  Moreover, in the tire 10 of the present invention, at least two of the at least four radial carcass plies 4a to 4d are the downplies 4c and 4d. Considering only the durability, all the radial carcass plies 4a to 4d may be turn-up plies, but in this case the rigidity of the sidewall portion 2 is increased, and the grip and absorbability at the time of turning are improved. It may get worse. Moreover, such a structure is not preferable because it increases the production cost. From this point of view, it is preferable that the structure of the carcass 4 includes two down plies 4c and 4d and two turn-up plies 4a and 4b as shown in the drawing.

  When five or more radial carcass plies are used, for example, the number of down plies may be increased, and when five radial carcass plies are provided, two turn-up plies and three down plies may be used. In the tire 10 of the present invention, the angle of the radial carcass ply with respect to the tire circumferential direction is preferably in the range of 90 ± 25 °, and particularly preferably 90 ± 17 °.

  Furthermore, in the tire 10 of the present invention, the tread portion 3 is divided into a center region 3c including the tire equator and a shoulder region 3s on the outer side in the tire width direction of the center region 3c. As described above, in the tire 10 of the present invention, since the number of radial carcass plies is at least four or more, the thickness of the tread portion 3 may be increased, and the high-speed durability may be reduced. Therefore, in the tire 10 of the present invention, high-hardness rubber is disposed in the center region 3c of the tread portion 3 to improve high-speed durability. However, high hardness rubbers have low tan δ at 0 ° C. and wet grip performance is degraded. Therefore, the center area 3c is narrowed to enlarge the shoulder area 3s, and rubber having a relatively low hardness is disposed in the shoulder area 3s in the shoulder area 3s to prevent a decrease in wet grip performance.

  Specifically, when the distance from the tire equator E to the tread end along the surface of the tread portion 3 is L, the division position of the center region 3 c and the shoulder region 3 s is 0. 0 from the tire equator E of the tread portion 3. 12 L to 0.22 L Here, the dividing position of the center area 3 c and the shoulder area 3 s is based on the surface of the tread portion 3. In addition, the hardness Hd (c) of the rubber in the center area 3c is made larger than the hardness Hd (s) of the rubber in the shoulder area 3s, but the hardness Hd (c) of the rubber in the center area 3c is preferably 60 to 70, The hardness Hd (s) of the rubber in the shoulder region 3s is preferably 50 to 60.

  Furthermore, in the tire 10 of the present invention, tan δ (c) of the rubber in the center region 3c is preferably 0.2 to 0.35, and tan δ (s) of the shoulder region 3 s is 0.35 to 0.85. Is preferred. By satisfying this range, it is possible to secure sufficient wet grip performance. In the illustrated example, the boundary between the center region 3c and the shoulder region 3s is inclined with respect to the tire radial direction, but in the tire 10 of the present invention, the boundary between the center region 3c and the shoulder region 3s is , And the surface of the tread portion 3 as a reference.

  Specifically as a rubber component of tread rubber, for example, styrene butadiene copolymer rubber (SBR), natural rubber (NR), styrene isoprene copolymer rubber (SIR), polyisoprene rubber (IR) Synthetic rubbers such as polybutadiene rubber (BR), butyl rubber (IIR), and ethylene-propylene copolymer can be used. The hardness and tan δ of the tread rubber can be appropriately adjusted by adjusting the amount of resin, carbon black, silica and the like in the rubber composition. For example, to increase the value of tan δ, the amounts of carbon black and silica in the rubber composition may be increased, and to decrease the value of tan δ, the amounts of carbon black and silica may be reduced.

  The tire 10 of the present invention is a pneumatic radial tire for a motorcycle having the spiral belt layer 5, and as long as the configuration of the carcass 4 and the tread portion 3 satisfies the above requirements, there is no particular limitation. A known structure and material can be applied as appropriate. For example, as illustrated, the bead filler 7 may be disposed on the tire radial direction outer side of the bead core 6. For the carcass cords of the radial carcass plies 4a to 4d, polyamide such as nylon, polyester such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), organic fiber cord such as aramid or rayon can be used.

  The spiral belt layer 5 of the tire 10 according to the present invention is formed by spirally winding a long rubber-coated cord in which one cord is covered with rubber or a belt-like ply in which a plurality of cords is covered with rubber. The cord can be formed by twisting, and as the cord, other than steel cord, organic fibers such as aramid, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), rayon, nylon, etc., further, glass fiber, carbon fiber, etc. The thing of a material can be selected suitably and can be used.

  Furthermore, in the tire 10 of the present invention, an inner liner may be disposed on the innermost layer of the tire (not shown), and furthermore, a tread pattern is appropriately formed on the surface of the tread portion 3 Also good (not shown). The tire 10 of the present invention can be suitably used for a rear tire which is a driving wheel of a motorcycle.

Hereinafter, the present invention will be described in more detail using examples.
Example 1
A pneumatic radial tire for a motorcycle of the type shown in FIG. 1 was produced with a tire size of 190/55 ZR17 M / C. The carcass has four carcass plies made of nylon. The first and second carcass plies from the inner side in the tire radial direction are used as turn-up plies, and the third and fourth carcass plies are used as down plies. A steel cord was used for the belt cord of the spiral belt layer. The angle of the carcass ply was set to 75 ° with respect to the tire circumferential direction, and the spiral belt layer was set to approximately 0 ° with respect to the circumferential direction. The hardness Hd (c) of the rubber in the center region of the tread portion was 62, and tan δ (c) at 0 ° C. was 0.28. The hardness Hd (s) of the rubber in the shoulder region was 58, and tan δ (s) at 0 ° C. was 0.41. The boundary between the center area and the shoulder area is as shown in Table 1 below.

<Examples 2 to 4, Comparative Examples 1 and 2, and Conventional Examples 1 to 3>
Examples 2 to 4 and Comparative Example 1 are the same as Example 1 except that the carcass structure, the angle of the carcass ply, and the boundary between the center region and the shoulder region are changed to the values shown in Tables 1 and 2 from the tire equator. The tires of No. 2 and Conventional Examples 1 to 3 were produced. FIG. 2 is a cross-sectional view in the tire width direction of a pneumatic radial tire for a motorcycle according to Conventional Example 1.

  Each of the obtained tires was evaluated for heavy load durability, high speed durability and wet grip. Evaluation conditions are as follows.

<Heavy load durability>
The test was performed under the following conditions to determine the load at which a failure occurs. Based on the obtained results, an index was calculated using Conventional Example 1 as 100. The higher the number, the better the result. The results are shown in Table 1.
Rim: MT 6.00-16M / C
Internal pressure: 340 kPa
Load: Step load Speed at test: 81 km / h

<High-speed durability>
The test was conducted under the following conditions to determine the speed at which a failure occurs and the load. Based on the obtained results, an index was calculated using Conventional Example 1 as 100. The higher the number, the better the result. The results are shown in Table 1.
Rim: MT 6.00-16M / C
Internal pressure: 300 kPa
Load: Step load Speed at test: Step speed

<Wet grip>
Under the following conditions, an actual vehicle feeling test on a wet road surface by a rider was performed, and the obtained result was calculated as an index with Conventional Example 1 being 100. The higher the number, the better the result. The results are shown in Table 1.
Rim: MT 6.00-16M / C
Test vehicle: 1200CC touring bike internal pressure: 290kPa
Load: 200 kg

※：タイヤ赤道から、センター領域３ｃとショルダー領域３ｓとの境界までの距離

※: The distance from the tire equator to the boundary between the center area 3c and the shoulder area 3s

  From Tables 1 and 2, it can be seen that the tire of the present invention is improved in durability under heavy load with almost no decrease in wet grip.

DESCRIPTION OF SYMBOLS 1 and 11 bead part 2 12 side wall part 3 13 tread part 4a-4d 14a-14c radial carcass ply 4 14 carcass 5 15 spiral belt layer 6 16 bead core 7 17 bead filler 10 20 Pneumatic radial tire (tire)

Claims (4)

A pair of bead portions in which a bead core is embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portion, a tread portion extending across the pair of sidewall portions, and at least four or more radial carcasses A pneumatic radial tire for a motorcycle comprising: a carcass comprising a ply; and a spiral belt layer having an angle of 0 to 5 degrees with respect to the circumferential direction of the tire of the tread portion disposed radially outward of the carcass. In
At least two turn-up plies in which the at least four or more radial carcass plies are wound outward from the inside in the tire width direction of the bead core, and at least two down plies in which the bead core is terminated without being wound up; Consists of
When the distance from the tire equator to the tread end along the surface of the tread portion is L, and the tread portion is a center region including the tire equator in the tire width direction and a shoulder region outside the center region in the width direction, The division position of the center area and the shoulder area is in the range from 0.12 L to 0.22 L from the tire equator, and the hardness Hd (c) of the rubber of the center area is from the Hd (s) of the rubber of the shoulder area A pneumatic radial tire for a motorcycle characterized by being large.   The pneumatic radial for a motorcycle according to claim 1, wherein tan δ (c) of the rubber in the center region is 0.2 to 0.35, and tan δ (s) of the shoulder region is 0.35 to 0.85. tire.   The pneumatic radial tire for a motorcycle according to claim 1 or 2, wherein the Hd (c) is 60 to 70, and the Hd (s) is 50 to 60.   The pneumatic radial tire for a motorcycle according to any one of claims 1 to 3, wherein the turn-up ply is two and the down ply is two.

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