JP2015033982A - Tire for motor cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire for a motor cycle that suppresses occurrence of crack in a trad rubber while improving turning performance.SOLUTION: A tire 1 for a motor cycle is provided with a carcass 6 and a tread reinforcing layer 7. A tread rubber 2G arranged in the tread portion 2 includes a first rubber layer 11 and a second rubber layer 21. A boundary face 13 between the first rubber layer 11 and the second rubber layer 21 has a lateral edge portion 14 appearing on a tire lateral face. An outer end 6e in a tire radial direction of a folded portion 6b is positioned further inside in the tire radial direction than an outer end 7e of the tread reinforcing layer 7. A height h1 in the tire radial direction of a bent region 16 is equal to 0.2 times of a height h0 of a grounding end or less. Distance L1 in the tire radial direction between an intermediate position 16m in the tire radial direction of the bent region 16 and the lateral edge portion 14 is equal to 0.1 times of the height h0 of the grounding end or more.

Description

  The present invention relates to a motorcycle tire that improves the turning performance and suppresses the occurrence of cracks in tread rubber.

  With the recent improvement in performance of motorcycles, high turning performance is required for motorcycle tires. In particular, motorcycle tires for racing are required to improve a feeling of grounding when turning at a large camber angle at which the tread grounding end touches (hereinafter sometimes referred to as “full bank”).

  Patent Document 1 below proposes a motorcycle tire in which the tread rubber has two layers including a cap rubber layer and a base rubber layer, and the cap rubber layer has a rubber hardness smaller than that of the base rubber layer. Such a cap rubber layer exhibits excellent grip performance, and the base rubber layer effectively maintains the rigidity of the tread rubber. As a result, the tire of Patent Document 1 below is expected to have the effect of improving the feeling of ground contact during turning.

JP 2007-223376 A

  In order to effectively exhibit the above-described effects even at the time of a full bank, a tire in which the cap rubber layer and the base rubber layer extend to the tire side surfaces can be considered. In this tire, the side edge portion of the boundary surface between the cap rubber layer and the base rubber layer appears on the side surface of the tire.

  However, the tire in which the side edge portion of the boundary surface between the cap rubber layer and the base rubber layer appears on the side surface of the tire has a problem that cracks starting from the side edge portion are likely to occur.

  The present invention has been devised in view of the actual situation as described above, and includes a tread rubber including two rubber layers, and a motorcycle in which a side edge portion of a boundary surface of the rubber layer appears on a tire side surface. The main object of the present invention is to provide a motorcycle tire that suppresses the occurrence of cracks in tread rubber while improving turning performance.

  The present invention includes a main body portion that extends from the tread portion through the side wall portions on both sides to the bead cores on the bead portions on both sides, and a pair of folded portions that are connected to the main body portion and folded around the bead core from the inner side to the outer side in the tire axial direction. And a tread reinforcing layer disposed outside the carcass in the tire radial direction and inside the tread portion, and the contact surface of the tread portion protrudes outward in the tire radial direction and has an arc shape. A curved tire for a motorcycle, wherein a tread rubber disposed in the tread portion includes a first rubber layer forming the ground contact surface and a second rubber layer disposed inside the first rubber layer. And a boundary surface between the first rubber layer and the second rubber layer is a side edge portion that appears on a tire side surface extending inward in the tire radial direction from a tread ground contact end that is an outer end of the ground contact surface. And the outer end of the folded portion in the tire radial direction is located on the inner side in the tire radial direction from the outer end of the tread reinforcing layer in the tire axial direction, and the outer end of the folded portion and the tread reinforcing layer The height in the tire radial direction of the bent region, which is a region between the outer ends, is 0.2 times or less the height of the ground contact edge, which is the distance in the tire radial direction from the bead base line to the tread ground contact edge, The distance in the tire radial direction between the intermediate position in the tire radial direction of the bent region and the side edge is 0.1 times or more the height of the ground contact edge.

  In the pneumatic tire according to the present invention, the carcass is convexly curved outward in the tire axial direction at the sidewall portion, and has a maximum width point that protrudes most outward in the tire axial direction. It is desirable that the outer end of the portion is disposed outside the maximum width point in the tire radial direction.

  In the pneumatic tire according to the present invention, the rubber thickness from the outer surface of the sidewall portion to the carcass at the maximum width point is desirably 2.0 mm or less.

  In the pneumatic tire according to the present invention, the tread reinforcing layer is formed of a belt layer in which a plurality of belt plies in which a belt cord is inclined at an angle of 15 to 45 ° with respect to the tire equator are arranged, and the belt The cord is preferably an aromatic polyamide.

  In the pneumatic tire according to the present invention, it is desirable that the second rubber layer has a larger complex elastic modulus E * than the first rubber layer.

  In the pneumatic tire according to the present invention, it is preferable that the side edge portion is located on the outer side in the tire radial direction with respect to the outer end of the tread reinforcing layer.

  In the pneumatic tire according to the present invention, the second rubber layer forms the tire side surface on the inner side in the tire radial direction from the side edge portion through the sidewall portions on both sides from the tread portion. It is desirable to have a toroidal shape that reaches the bead portion.

  In the motorcycle tire of the present invention, the tread rubber disposed in the tread portion includes a first rubber layer that forms a ground contact surface, and a second rubber layer disposed inside the first rubber layer. The boundary surface between the first rubber layer and the second rubber layer has a side edge portion that appears on the side surface of the tire extending inward in the tire radial direction from the tread contact end that is the outer end of the contact surface. Such a tread rubber exhibits the characteristics of the first rubber layer and the second rubber layer in a wide range even during full banking, and exhibits excellent turning performance.

  The outer end of the carcass folded portion in the tire radial direction is located on the inner side in the tire radial direction of the outer end of the tread reinforcing layer in the tire axial direction. Thereby, a folding | returning part and a tread reinforcement layer do not overlap. For this reason, deformation of the tire during turning occurs mainly in a bent region between the tread reinforcing layer and the folded portion.

  The height in the tire radial direction of the bent region, which is the region between the outer end of the folded portion and the outer end of the tread reinforcing layer, is the ground end height, which is the distance in the tire radial direction from the bead base line to the tread ground end. Is 0.2 times or less. As a result, the height in the tire radial direction of the bent region where deformation is likely to occur during turning is limited, and deformation of the tire during turning is reduced. For this reason, the feeling of grounding especially at the time of a full bank improves, and by extension, turning performance improves.

  The distance in the tire radial direction between the intermediate position in the tire radial direction of the bent region and the side edge portion is 0.1 times or more the height of the ground contact edge. Thereby, the side edge part which is easy to become the starting point of a crack is distribute | arranged to the position away from the intermediate position of the bending area | region which is easy to deform | transform at the time of turning. For this reason, the crack which started from the side edge part is suppressed effectively.

1 is a cross-sectional view showing an embodiment of a motorcycle tire of the present invention. FIG. 2 is an enlarged sectional view of the motorcycle tire of FIG. 1. It is an expanded sectional view showing other embodiments of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a tire meridian cross-sectional view including a tire rotation axis in a normal state of a motorcycle tire 1 (hereinafter, simply referred to as “tire”) of the present embodiment. The tire 1 of the present embodiment is a motorcycle tire for a slick race in which no groove is provided in the tread portion 2.

  The “normal state” is a no-load state in which the tire 1 is assembled to a normal rim (not shown) and filled with a normal internal pressure. Unless otherwise specified in the present specification, the dimensions of the respective parts of the tire 1 are values measured in a normal state.

  The “regular rim” is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, For ETRTO, "Measuring Rim".

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. “JAMATA” is the “highest air pressure”, TRA is the table “TIRE LOAD LIMITS AT” The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO.

  As shown in FIG. 1, the tire 1 of the present embodiment has a tread portion 2. In the tread portion 2, the contact surface 2 s between the tread contact ends Te and Te is curved outward in the tire radial direction so as to obtain a sufficient contact area even when turning with a large camber angle. . The tread width TW, which is the distance in the tire axial direction between the tread grounding ends Te, Te, forms the maximum tire width.

  FIG. 2 shows an enlarged cross-sectional view of the tire 1. As shown in FIG. 2, the tire 1 of the present embodiment includes a carcass 6, a bead apex rubber 8, a tread reinforcing layer 7, and a tread rubber 2G.

  The carcass 6 includes a main body portion 6a and a folded portion 6b. The main body 6a extends from the tread portion 2 to the bead cores 5 of the bead portions 4 on both sides through the side wall portions 3 on both sides. The folded portion 6b is connected to the main body portion 6a and folded around the bead core 5 from the inner side to the outer side in the tire axial direction.

  The carcass 6 has a maximum width point 15 that protrudes outward in the tire axial direction at the sidewall portion 3 and protrudes most outward in the tire axial direction. The outer end 6e in the tire radial direction of the folded portion 6b of the present embodiment is disposed on the outer side in the tire radial direction from the maximum width point 15.

  A distance L2 in the tire radial direction between the outer end 6e of the folded portion 6b and the maximum width point 15 is, for example, 2 to 7 mm, and more preferably 3 to 5 mm.

  The carcass 6 is formed by, for example, one carcass ply 6A. The carcass ply 6A has a carcass cord arranged with an inclination of, for example, 75 to 90 ° with respect to the tire equator C. As the carcass cord, for example, an organic fiber cord such as nylon, polyester, or rayon is suitably employed. Nylon is adopted for the carcass cord of this embodiment. As a result, the tire becomes lighter and the running performance is improved.

  The bead apex rubber 8 is disposed between the main body portion 6a and the folded portion 6b. The bead apex rubber 8 is formed of, for example, a hard rubber that tapers from the bead core 5 outward in the tire radial direction.

  The tread reinforcing layer 7 is disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2. The tread reinforcing layer 7 of the present embodiment is provided over substantially the entire area of the tread portion 2. The tread reinforcing layer 7 is made of, for example, a ply in which cords are arranged. The tread reinforcing layer 7 of this embodiment is formed of a plurality of belt plies. In the belt ply, the belt cord is inclined at an angle of 15 to 45 ° with respect to the tire equator C. The tread reinforcing layer 7 is provided with, for example, a jointless ply in which a narrow belt-like ply is spirally wound at an angle of 5 ° or less with respect to the tire circumferential direction as the outermost ply 7C in the tire radial direction. Also good.

  The cord of the tread reinforcing layer 7 is preferably an organic fiber cord such as polyester, nylon, rayon, or aromatic polyamide. The cord of this embodiment employs aromatic polyamide. Such a cord suppresses deformation of the tread portion 2 during traveling, and improves a feeling of grounding when the vehicle is tilted down.

  The outer end 6e in the tire radial direction of the folded portion 6b of the carcass ply 6A is located on the inner side in the tire radial direction with respect to the outer end 7e in the tire axial direction of the tread reinforcing layer 7. Thereby, the folding | returning part 6b and the tread reinforcement layer 7 do not overlap. For this reason, deformation of the tire during turning occurs mainly in the bent region 16 which is a region between the outer end 7e of the tread reinforcing layer 7 and the outer end 6e of the folded portion 6b.

  The height h1 in the tire radial direction of the bent region 16 is 0.2 times or less of the ground contact edge height h0 that is the distance in the tire radial direction from the bead base line BL to the tread ground contact edge Te. Thereby, the height in the tire radial direction of the bent region 16 where deformation is likely to occur during turning is limited, and deformation of the tire during turning is reduced. For this reason, the feeling of grounding especially at the time of a full bank improves, and by extension, turning performance improves. The bead base line BL is a tire axial line passing through a rim diameter position defined by a standard on which the tire is based.

  The ratio h1 / h0 between the height h1 of the bent region 16 and the ground contact end height h0 is preferably 0.15 or less, more preferably 0.10 or less. As a result, the deformation of the tire during turning is reduced, and the feeling of grounding during full banking is further improved. The ratio h1 / h0 is preferably 0.05 or more, more preferably 0.08 or more. When the ratio h1 / h0 is smaller than 0.05, the sidewall portion 3 is shear-deformed around the bent region 16, and the durability of the tire 1 may be reduced.

  A tread rubber 2 </ b> G disposed in the tread portion 2 includes a first rubber layer 11 made of the first rubber 10 and a second rubber layer 21 made of the second rubber 20.

  The first rubber layer 11 forms a ground contact surface 2 s of the tread portion 2. The first rubber layer 11 of the present embodiment forms the entire ground contact surface between the tread ground contact ends Te on both sides.

  The complex elastic modulus E * 1 of the first rubber 10 is, for example, 4.0 to 6.0 MPa. The loss tangent tan δ1 of the first rubber 10 is, for example, 0.10 to 0.20. Such a first rubber 10 generates moderate heat and softens during running, and exhibits excellent grip.

In this specification, the complex elastic modulus E * and the loss tangent tan δ are values measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the following conditions in accordance with the provisions of JIS-K6394. It is.
Initial strain: 10%
Amplitude: ± 1%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70 ° C

  The second rubber layer 21 is disposed inside the first rubber layer 11. In the tread portion 2, the second rubber layer 21 extends along the ground contact surface 2 s and the tread reinforcing layer 7.

  The second rubber layer 21 has a substantially constant rubber thickness at the center of the tread near the tire equator C. The rubber thickness t2 of the second rubber layer 21 at the tire equator C is preferably 0.5 mm or more, more preferably 1.0 mm or more, preferably 2.0 mm or less, more preferably 1.5 mm or less. . Such a second rubber layer 21 cooperates with the first rubber layer 11 to increase the rigidity of the tread rubber 2G in a well-balanced manner.

  The complex elastic modulus E * 2 of the second rubber 20 is preferably larger than the complex elastic modulus E * 1 of the first rubber 10. Such a second rubber 20 effectively maintains the rigidity of the tread rubber 2G and improves the feeling of grounding when the tread rubber is turned down.

  The complex elastic modulus E * 2 of the second rubber 20 and the complex elastic modulus E * 1 and the ratio E * 2 / E * 1 of the first rubber 10 are preferably 1.05 or more, more preferably 1.10 or more. , Preferably 1.20 or less, more preferably 1.25 or less. When the ratio E * 2 / E * 1 is smaller than 1.05, the rigidity of the tread rubber 2G may not be effectively maintained. Conversely, when the ratio E * 2 / E * 1 is greater than 1.25, the first rubber layer 11 and the second rubber layer 21 may be easily peeled off.

  The loss tangent tan δ2 of the second rubber 20 is preferably smaller than the loss tangent tan δ1 of the first rubber 10. Such a second rubber suppresses heat generation of the tread rubber 2G during traveling, and a decrease in grip performance due to heat is suppressed.

  The ratio tan δ2 / tan δ1 between the loss tangent tan δ2 of the second rubber 20 and the loss tangent tan δ1 of the first rubber 10 is preferably 0.95 or less, more preferably 0.90 or less, preferably 0.80 or more, more Preferably it is 0.85 or more. Thereby, the distribution of heat generation inside and on the surface of the tread rubber 2G at the time of traveling becomes appropriate, and excellent grip performance is exhibited while suppressing a decrease in performance due to heat.

  The first rubber layer 11 and the second rubber layer 21 are disposed throughout the tread portion 2. The boundary surface 13 between the first rubber layer 11 and the second rubber layer 21 has a side edge portion 14 that appears on the tire side surface 1s. The tire side surface 1s is a tire outer surface extending inward in the tire radial direction from the tread contact end Te. Such a tread rubber 2G exhibits the characteristics of the first rubber layer 11 and the second rubber layer 21 widely in the tread width direction even in a full bank where the tread ground end Te contacts the ground, and exhibits excellent turning performance. .

  The distance L1 in the tire radial direction between the intermediate position 16m in the tire radial direction of the bent region 16 and the side edge portion 14 is 0.1 times or more the ground contact edge height h0. Thereby, the side edge part 14 which tends to become a starting point of a crack is distribute | arranged to the position away from the intermediate position 16m of the bending area | region 16 which is easy to deform | transform at the time of turning. For this reason, the crack which started from the side edge part 14 is suppressed effectively.

  The distance L1 between the intermediate position 16m of the bent region 16 and the side edge portion 14 is preferably 0.12 times or more, more preferably 0.14 times or more, preferably 0.18 times or less of the ground contact end height h0. More preferably, it is 0.16 times or less. Accordingly, the distance L1 is ensured while the rubber thickness of the first rubber layer 11 in the vicinity of the tread grounding end Te is maintained. Accordingly, cracks on the tire side surface 1s are effectively suppressed while maintaining the turning performance.

  The side edge portion 14 is preferably located on the outer side in the tire radial direction with respect to the outer end 7 e of the tread reinforcing layer 7. Thereby, since the side edge part 14 is located in the outer side of a tire radial direction rather than the bending area | region 16, the crack in the tire side surface 1s is suppressed more effectively.

  The rubber thickness t1 from the outer surface 3s of the sidewall portion 3 to the carcass 6 at the maximum width point 15 is preferably 2.0 mm or less. When the rubber thickness t1 is larger than 2.0 mm, the tread portion 2 is difficult to bend, and the weight of the tire 1 increases, so that the turning performance may be deteriorated. The rubber thickness t1 is desirably 0.5 mm or more. When the rubber thickness t1 is smaller than 0.5 mm, the durability of the sidewall portion 3 may be reduced.

  It is desirable that the second rubber layer 21 has a toroidal shape extending from the tread portion 2 to the bead portions 4 on both sides through the sidewall portions 3 on both sides so as to form the tire side surface 1s. Thereby, the boundary of the different kind of rubber which appears on the tire side surface 1s becomes only the side edge portion 14. Therefore, the generation of cracks starting from the rubber boundary is effectively suppressed.

  FIG. 3 shows a cross-sectional view of a tire 1 according to another embodiment of the present invention. As shown in FIG. 3, the boundary surface 13 of another embodiment includes a first portion 13 a and a second portion 13 b. The first portion 13 a of the boundary surface 13 extends in a substantially arc shape along the ground contact surface 2 s of the tread portion 2. The second portion 13b is connected to the tread contact end Te side of the first portion 13a and is inclined outward in the tire radial direction toward the outer side in the tire axial direction. In this embodiment, the second portion 13b is curved in an arc shape protruding in the opposite direction to the first portion 13a. Thereby, the distance L1 between the side edge portion 14 and the intermediate position 16m of the bent region 16 is further increased, and cracks on the tire side surface 1s are effectively suppressed.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

Front wheel tires for motorcycles having the basic structure shown in FIG. 1 and based on the specifications shown in Table 1 were manufactured, and their performances were tested. As Comparative Examples 1 and 2, tires whose side edges were covered with cushion rubber and did not appear on the tire side surfaces were tested. The common specifications and test methods for each test tire are as follows.
Tire size: 95 / 70R17
Rim size: MT2.50
Tire internal pressure: 180kPa
Test vehicle: displacement 125cc

<Grounding feeling when turning>
The test vehicle traveled around a test course of 3700 m per lap, and the feeling of ground contact at the time of turning was evaluated by the driver's sensuality. A result is a score which sets the comparative example 1 to 100, and shows that the grounding feeling at the time of turning is excellent, so that a numerical value is large.

<The occurrence of cracks>
After a certain number of laps around the test course with the test vehicle, the occurrence of cracks on the side surface of the tire was visually confirmed. The results were evaluated in the following three stages.
A: No cracks are generated.
B: Cracks are not generated, but wrinkles are generated near the side edges.
C: Cracks are generated.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that in the motorcycle tire of the example, the occurrence of cracks in the tread rubber was suppressed while the touch feeling was improved.

2 tread portion 3 sidewall portion 4 bead portion 5 bead core 6 carcass 7 tread reinforcing layer 11 first rubber layer 13 boundary surface 14 side edge portion 16 bending region 16m intermediate position 21 second rubber layer

Claims (7)

A carcass including a main body part extending from the tread part through the side wall parts on both sides to the bead cores of the bead parts on both sides, and a pair of folded parts connected to the main body part and folded around the bead core from the inner side to the outer side in the tire axial direction; as well as,
Including a tread reinforcing layer disposed on the outside of the tire radius direction of the carcass and inside the tread portion;
Moreover, the tread portion is a tire for a motorcycle in which the contact surface of the tread is convex outward in the tire radial direction and curved in an arc shape,
The tread rubber disposed in the tread portion includes a first rubber layer that forms the ground contact surface, and a second rubber layer disposed inside the first rubber layer,
The boundary surface between the first rubber layer and the second rubber layer has a side edge portion that appears on a tire side surface extending inward in the tire radial direction from a tread contact end that is an outer end of the contact surface,
The outer end of the folded portion in the tire radial direction is located on the inner side in the tire radial direction of the outer end in the tire axial direction of the tread reinforcing layer,
The height in the tire radial direction of the bent region, which is the region between the outer end of the folded portion and the outer end of the tread reinforcing layer, is the distance in the tire radial direction from the bead base line to the tread ground contact end. Is less than 0.2 times the height of the ground contact,
A tire for a motorcycle, wherein a distance in the tire radial direction between an intermediate position in the tire radial direction of the bent region and the side edge portion is 0.1 times or more of a height of the ground contact edge. The carcass is convexly curved outward in the tire axial direction at the sidewall portion, and has a maximum width point that protrudes most outward in the tire axial direction,
2. The motorcycle tire according to claim 1, wherein the outer end of the folded portion is disposed on the outer side in the tire radial direction from the maximum width point. 3.   The motorcycle tire according to claim 2, wherein a rubber thickness from an outer surface of the sidewall portion to the carcass at the maximum width point is 2.0 mm or less. The tread reinforcing layer is formed of a belt layer in which a plurality of belt plies in which a belt cord is inclined at an angle of 15 to 45 ° with respect to the tire equator are arranged,
The motorcycle tire according to any one of claims 1 to 3, wherein the belt cord is an aromatic polyamide.   The motorcycle tire according to any one of claims 1 to 4, wherein the second rubber layer has a larger complex elastic modulus E * than the first rubber layer.   The motorcycle tire according to any one of claims 1 to 5, wherein the side edge portion is located on an outer side in a tire radial direction from the outer end of the tread reinforcing layer.   The second rubber layer has a toroidal shape extending from the tread portion to the bead portions on both sides through the side wall portions on both sides so as to form the tire side surface in the tire radial direction from the side edge portion. Item 7. The motorcycle tire according to any one of Items 1 to 6.

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