JP2007125987A - Pneumatic tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire of a motorcycle with excellent steering stability performance in high speed traveling by improving steering responsiveness and comfortability in handling and securing a gripping force in turning. <P>SOLUTION: This tire 10 is provided with a bead core 20, a bead 18, a carcass 16, an inclined belt layer 24 arranged outside the tire diametrical direction of the carcass, a spiral belt layer 22, and tread rubber 30 forming the tread 28. A central part of the tread 28 is formed of tread rubber 30A and side parts on both sides of it are formed of tread rubber 30B, the tread rubber 30A is harder than the tread rubber 30B, a boundary between the tread rubber 30A and 30B is formed within a grounding surface when a tire rotation axis is in parallel with a road surface on a cross-section in the tire cross direction. Consequently, the torsional rigidity of the central part is improved, the lateral bending rigidity of the side parts on the both sides is maintained in a low state, the steering responsiveness and the comfortability in handling are improved, the gripping force in turning is secured and the steering stability performance in high speed traveling is improved excellently. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire for a motorcycle that is excellent in handling stability performance at high speeds, and more particularly to a pneumatic tire for a motorcycle that is excellent in handling lightness, steering angle response, and gripping power during turning.

In order to increase the speed of vehicles in recent years, as a requirement item for tires, it has become important to secure a high grip force that supports the vehicle when turning. From this, in order to increase the grip strength of the tire, a flexible compound rubber with high grip strength is applied to the tread rubber, or the tire shoulder area (hereinafter simply referred to as the shoulder area) that contacts the road surface during turning is bent in the tire width direction. Techniques such as reducing rigidity (hereinafter simply referred to as “lateral bending rigidity”), improving flexibility, and improving ground contact are taken.
However, with these methods, the overall stiffness of the tire crown decreases, and the torsional rigidity of the tire crown decreases as the lateral bending rigidity of the shoulder region decreases. In addition, lightness may be impaired, and safe driving may be hindered (steering stability performance deteriorates).

On the other hand, in the tire disclosed in Patent Document 1, the tread portion of the tire having a spiral belt structure is divided into three in the tire axial direction (divided into a central region and both side regions of the tread portion), and both side regions are obtained. The ratio of loss tangent to JIS (A) hardness and dynamic complex modulus of the tread rubbers of the tread rubber is set to a value higher than those in the central area. As a result, the low lateral rigidity of the spiral structure is reinforced, and the grip force during turning is ensured, so that the cornering force and the camber thrust are improved and the turning performance is excellent.
Japanese Laid-Open Patent Publication No. 7-108805

  However, when the rigidity step where the rigidity of the tread portion changes, for example, in the shoulder region as in the tire of Patent Document 1, discontinuity occurs in the level of lateral force generated according to the camber angle at the time of turning. Therefore, the linearity of handling may be impaired, and the steering stability performance during high-speed traveling may be impaired.

  In the market, the tire tread stiffness distribution during high-speed driving is optimized, grip power during turning is ensured, tire torsional rigidity is high, rudder angle response and lightness pneumatic Tires are expected.

  The object of the present invention is to improve the steering angle responsiveness and lightness of handling in consideration of the above facts, and to ensure the grip force at the time of turning and to improve the steering stability performance at the time of high speed driving. The purpose is to provide tires.

  In order to achieve the above object, a pneumatic tire for a motorcycle according to claim 1 of the present invention includes a bead core embedded in a pair of left and right bead portions, a toroidal shape extending from one bead portion to the other bead portion. A carcass made of at least one carcass ply, the portion of which is wound around the bead core and locked to the bead core; a belt layer disposed on the outer side in the tire radial direction of the carcass; and a tire radial direction from the belt layer A pneumatic tire for a motorcycle including a tread rubber that is disposed outside and forms a tread portion that contacts a road surface, and in the tire width direction cross section, a central portion of the tread portion is formed of a first rubber, Both sides of the central portion are formed of a second rubber, the first rubber is harder than the second rubber, and the boundary between the first rubber and the second rubber is Characterized in that it is provided with a tire rotation axis in the ground plane when in parallel with the road surface.

Next, the function and effect of the pneumatic tire for a motorcycle according to claim 1 will be described.
In order to improve the grip force during turning, as described above, by reducing the lateral bending rigidity of the shoulder area that touches down during turning, the shoulder area can be made more flexible and the grounding performance can be improved. There is a method to apply a flexible compound rubber with a high grip force to the rubber, but no matter which method is used to improve the grip force, the torsional rigidity of the tire crown will decrease, rudder angle response and lightness The steering stability performance during high-speed driving deteriorates.

  Therefore, in the pneumatic tire for a motorcycle according to the present invention, the tread portion is the central portion and the side portions on both sides thereof, and the first rubber in the central portion is harder than the second rubber on the side portions on both sides, The lateral bending rigidity and torsional rigidity of the central portion are improved, and the steering angle response and lightness of handling are improved. At this time, since the lateral bending rigidity of the side portions on both sides is kept low, a high grip force is ensured. As a result, the steering angle responsiveness and lightness during straight traveling are improved, and the grip force during turning is ensured.

  Accordingly, the steering angle responsiveness and lightness are improved, the grip force at the time of turning is ensured, and the steering stability performance at the time of high speed running is excellent.

  In the pneumatic tire for a motorcycle according to the present invention, since the boundary between the first rubber and the second rubber is disposed in the ground contact surface when the tire rotation axis of the tread portion is parallel to the road surface, the first rubber The discontinuity of the lateral force generation level according to the camber angle at the time of turning due to the rigidity step between the second rubber and the second rubber is eliminated. For this reason, the linearity of handling is ensured and the steering stability performance is excellent.

In addition, the contact surface in this claim means a tire contact surface when assembled to a regular rim, filled with a regular internal pressure, placed perpendicular to a flat plate in a stationary state, and a regular load is applied, The distance in the tire axial direction of the contact surface is defined as the contact width.
“Regular rim” means, for example, a standard rim in the applicable size specified in the 2004 version of YEAR BOOK issued by JATMA. “Regular load” and “Normal internal pressure” are also issued by JATMA. This refers to the maximum load and the air pressure for the maximum load in the applicable size and ply rating defined in the 2004 YEAR BOOK.
When the TRA standard or ETRTO standard is applied at the place of use or manufacturing, the respective standards are followed.

  A pneumatic tire for a motorcycle according to a second aspect of the present invention is the pneumatic tire for a motorcycle according to the first aspect, wherein in the cross section in the tire width direction, the width of the ground contact surface is W1, and the width of the central portion is W2. In this case, 0.1W1 ≦ W2 is satisfied.

Next, the function and effect of the pneumatic tire for a motorcycle according to claim 2 will be described.
If 0.1W1> W2, the width W2 of the central portion is too narrow, so that the torsional rigidity is hardly improved, the steering angle responsiveness and the lightness are not improved, and the steering stability performance during high speed running is deteriorated. Therefore, it is preferable that the relationship between W1 and W2 satisfies 0.1W1 ≦ W2. The upper limit value of W2 is less than W1 as defined in claim 1.

  A pneumatic tire for a motorcycle according to claim 3 of the present invention is the pneumatic tire for motorcycle according to claim 1 or 2, wherein the cord of the belt layer is made of steel.

Next, functions and effects of the pneumatic tire for a motorcycle according to claim 3 will be described.
By making the cord of the belt layer made of steel, the rigidity of the tire is improved as a whole, and the steering angle response and lightness are also improved.
In particular, if the belt layer has a spiral belt structure, the cord is made of steel in addition to the gripping force due to the high grounding property due to the low lateral bending rigidity of the tire crown, which is a characteristic of the spiral belt. As a result, the torsional rigidity is improved, and the steering angle response and nimbleness are improved.

  A pneumatic tire for a motorcycle according to a fourth aspect of the present invention is the pneumatic tire for a motorcycle according to any one of the first to third aspects, wherein the belt layer includes one or a plurality of cores arranged in parallel. It is characterized by comprising a spiral belt layer formed by spirally winding a belt-like body in which a belt is embedded in a covering rubber.

Next, functions and effects of the pneumatic tire for a motorcycle according to claim 4 will be described.
Since the belt layer is formed of a spiral belt layer, deformation (expansion) of the tire toward the outer side in the tire radial direction during high-speed running is suppressed, and the ground contact shape is maintained, so that high-speed running durability is improved.

  A pneumatic tire for a motorcycle according to a fifth aspect of the present invention is the pneumatic tire for a motorcycle according to any one of the first to third aspects, wherein the belt layer includes one or a plurality of cores arranged in parallel. A spiral belt layer formed by spirally winding a belt-like body embedded in a covering rubber, and a plurality of layers extending between the spiral belt layer and the carcass and inclined with respect to the tire radial direction. And an inclined belt layer in which a cord of a book is embedded in a covering rubber.

Next, functions and effects of the pneumatic tire for a motorcycle according to claim 5 will be described.
Since the belt layer is composed of an inclined belt layer provided with a cord that is inclined with respect to the tire radial direction (perpendicular to the tire equatorial plane), lateral bending rigidity during turning can be ensured and high cornering force can be generated. .

  A pneumatic tire for a motorcycle according to a sixth aspect of the present invention is the pneumatic tire for a motorcycle according to any one of the first to third aspects, wherein the belt layer includes one or a plurality of cores arranged in parallel. A spiral belt layer formed by spirally winding a belt-like body embedded in a covering rubber, and a plurality of cords provided between the spiral belt layer and the carcass and arranged in parallel to each other. It is composed of a plurality of belt plies embedded in a covering rubber, and a cross belt layer in which the inclination directions with respect to the tire radial direction of the cords are opposite to each other between adjacent belt plies.

Next, functions and effects of the pneumatic tire for a motorcycle according to claim 6 will be described.
Since the belt layer is composed of an intersecting belt layer having cords inclined with respect to the tire radial direction, lateral bending rigidity at the time of turning can be ensured, and a higher cornering force can be generated.

  The pneumatic tire for a motorcycle according to claim 7 of the present invention is the pneumatic tire for motorcycle according to claim 5, wherein an angle B of the inclined belt layer with respect to a tire radial direction of the cord is 3 ° ≦ B ≦ 15 °. It is characterized by satisfying.

Next, functions and effects of the pneumatic tire for a motorcycle according to claim 7 will be described.
The reinforcing effect of the tire crown portion is improved by disposing the inclined belt layer including the cord having an angle B with respect to the tire radial direction between the spiral belt layer and the carcass.
If B <3 °, the cords of the inclined belt layer are substantially parallel to the tire radial direction, so that the effect of improving the torsional rigidity is small and the steering angle response and lightness are not improved. Further, if B> 15 °, the lateral bending rigidity of the belt layer becomes excessively large, resulting in poor ground contact during turning and a decrease in gripping force. Therefore, the angle B preferably satisfies 3 ° ≦ B ≦ 15 °.

  The pneumatic tire for a motorcycle according to claim 8 of the present invention is the pneumatic tire for motorcycle according to claim 6, wherein the angle B of the cord of the crossing belt layer with respect to the tire radial direction is 3 ° ≦ B ≦ 15 °. It is characterized by satisfying.

Next, functions and effects of the pneumatic tire for a motorcycle according to claim 8 will be described.
The reinforcing effect of the tire crown portion is improved by arranging the crossing belt layer including the cord having an angle B with respect to the tire radial direction between the spiral belt layer and the carcass.
At this time, if B <3 °, the cords of the crossing belt layers are substantially parallel to the tire radial direction, and therefore, the effect of improving the torsional rigidity is small, and the improvement of the steering angle response and lightness is small. Further, if B> 15 °, the lateral bending rigidity of the belt layer becomes excessively large, resulting in poor ground contact during turning and a decrease in gripping force. Therefore, the angle B preferably satisfies 3 ° ≦ B ≦ 15 °.

  The pneumatic tire for a motorcycle according to claim 9 of the present invention is the pneumatic tire for motorcycle according to any one of claims 1 to 8, wherein the elastic modulus of the first rubber is E1, and the second tire When the elastic modulus of rubber is E2, 1.1 ≦ E1 / E2 ≦ 1.7 is satisfied.

Next, functions and effects of the pneumatic tire for a motorcycle according to claim 9 will be described.
If 1.1> E1 / E2, there is little improvement in the torsional rigidity at the center, and little improvement in steering angle response and nimbleness. Also, the turning force during turning is reduced. If E1 / E2> 1.7, the difference in elastic modulus between the rubbers is too large, so that the linearity of handling is impaired, and the steering wheel may swing during traveling.
Therefore, it is preferable that 1.1 ≦ E1 / E2 ≦ 1.7 is satisfied.

A pneumatic tire for a motorcycle according to claim 10 of the present invention is the pneumatic tire for motorcycle according to claim 9, wherein the elastic modulus of the first rubber is E1 [kgf / mm ² ], and the second rubber. when the elastic modulus was E2 [kgf / mm ^2], and satisfies the ^{11kgf / mm 2 ≦ E1 ≦ 16kgf} / mm 2 and ^{7kgf / mm 2 ≦ E2 ≦ 13kgf} / mm 2.

Next, functions and effects of the pneumatic tire for a motorcycle according to claim 10 will be described.
If 11 kgf / mm ² > E1, there is little improvement in the torsional rigidity at the center, so the steering angle response and nimbleness are insufficient. If E1 <16 kgf / mm ² , the bending rigidity at the center (tire circumference) (Direction bending rigidity and lateral bending rigidity) are excessively improved, vibration absorption is impaired, and riding comfort performance is deteriorated.
If 7 kgf / mm ² > E2, the lateral bending rigidity commensurate with the gripping force at the side during turning cannot be ensured, so that the turning force is reduced and the turning performance is reduced, so that E2> 13 kgf / mm ² . For example, the lateral bending rigidity of the side portion is too large, and the grounding property at the time of turning is impaired, the grip force is lowered, and the steering stability performance is deteriorated.
Therefore, the elastic modulus E1 satisfies ^{11kgf / mm 2 ≦ E1 ≦ 16kgf} / mm 2, also the elastic modulus E2 preferably satisfies the ^{7kgf / mm 2 ≦ E2 ≦ 13kgf} / mm 2.

  A pneumatic tire for a motorcycle according to an eleventh aspect of the present invention is the pneumatic tire for a motorcycle according to any one of the first to tenth aspects, wherein the pneumatic tire is used for a front wheel of a motorcycle.

Next, functions and effects of the pneumatic tire for a motorcycle according to claim 11 will be described.
With regard to nimbleness and steering angle response, in the case of a two-wheeled vehicle, the influence of the front wheel that is a steered wheel is large, so the pneumatic tire for a motorcycle according to any one of claims 1 to 10 is applied to the front wheel of the motorcycle. When used, the effect of improving the steering angle responsiveness and nimbleness of handling is increased.

  The pneumatic tire for a motorcycle according to the present invention improves the steering angle response and lightness of handling, secures a grip force during turning, and has excellent steering stability performance during high-speed traveling.

[First Embodiment]
Next, a first embodiment of a pneumatic tire for a motorcycle according to the present invention will be described with reference to FIG. The pneumatic tire 10 for a motorcycle according to the present embodiment is a front tire, and the tire size is MCR180 / 55ZR17M / C.
As shown in FIG. 1, a pneumatic tire 10 for a motorcycle includes a first carcass ply 12 and a second carcass ply 14 in which a cord extending in a direction intersecting the tire equatorial plane CL is embedded. 16 is provided. 1 to 3, the carcass 16 is a single line, and the first carcass ply 12 and the second carcass ply 14 are not shown. In the present embodiment, the carcass 16 has a structure in which two carcass plies overlap each other. However, in other embodiments, the carcass 16 may have a structure having one carcass ply.

(Carcass)
Both ends of the first carcass ply 12 and the second carcass ply 14 are wound around the bead core 20 embedded in the bead portion 18 from the tire inner side toward the outer side.

  The first carcass ply 12 is formed by embedding a plurality of radially extending cords (for example, organic fiber cords such as nylon) in parallel in the covering rubber. In the present embodiment, the first carcass ply 12 has a tire equatorial plane CL. The angle of the cord with respect to the tire radial direction is set to 15 °. The second carcass ply 14 is also one in which a plurality of radially extending cords (for example, organic fiber cords such as nylon) are embedded in parallel in the covering rubber, and in this embodiment, the tire equatorial plane CL The angle of the cord with respect to the tire radial direction is set to 15 °. Further, the cord of the first carcass ply 12 and the cord of the second carcass ply 14 intersect each other and are inclined in opposite directions with respect to the tire equatorial plane CL. In the present embodiment, the first carcass ply 12 and the second carcass ply 14 are made of nylon.

(Inclined belt layer)
An inclined belt layer 24 is disposed outside the carcass 16 in the tire radial direction.
The inclined belt layer 24 is formed from a belt ply 24A.
The belt ply 24A is formed by embedding a plurality of cords (corresponding to a cord having a diameter of 0.5 mm in which nylon fibers are twisted) in parallel in a covering rubber, and in this embodiment, a tire equatorial plane. The angle of the cord with respect to the tire radial direction at CL is set to 10 °.
Further, the cord driving density in the belt ply 24A in the present embodiment is 10 pieces / 25 mm.

(Spiral belt layer)
A spiral belt layer 22 is provided outside the inclined belt layer 24 in the tire radial direction. The spiral belt layer 22 is formed by, for example, spiraling a long rubber-coated cord in which one cord is coated with an unvulcanized coating rubber, or a belt-like ply in which a plurality of cords are coated with an unvulcanized coating rubber. The angle of the cord with respect to the tire equatorial plane CL is approximately 0 ° (about 0 to 3 °). The cord of the spiral belt layer 22 may be an organic fiber cord or a steel cord.
In addition, the spiral belt layer 22 of the present embodiment is a spiral belt formed by embedding two parallel cords (steel cords obtained by twisting 1 × 2 type steel single wires having a diameter of 0.2 mm) in a covered rubber. It is formed by winding in the tire rotation axis direction. The cord driving density in the spiral belt layer 22 of this embodiment is 37/25 mm. A spiral belt layer formed by spirally winding a long rubber-coated cord in which one cord is coated with an unvulcanized coating rubber is called a monospiral belt layer.

(tread)
A tread rubber 30 forming a tread 28 is disposed on the outer side in the tire radial direction of the spiral belt layer 22.
Although the tread rubber 30 is formed of a plurality of types of rubber, the tread rubber 30 of the present embodiment is formed of two types of rubber described later. When viewed from the cross section in the tire width direction, the tread rubber 30A is the central portion of the tread 28, both side portions of the tread rubber 30A are tread rubber 30B, and the tread rubber 30A is harder than the tread rubber 30B. From this, it can be said that the tread rubber 30A has higher rigidity than the tread rubber 30B.
The boundary between the tread rubber 30A and the tread rubber 30B on both sides is provided in the ground contact surface of the tire 10 (the ground contact surface when the tire rotation axis is parallel to the road surface).

Further, when viewed from the cross section in the tire width direction, when the contact width of the tread 28 is W1, and the width of the tread rubber 30A measured along the tire axial direction is W2, it is preferable that 0.1W1 ≦ W2.
The angle B of the cord of the inclined belt layer 24 with respect to the tire radial direction is 80 ° in the present embodiment, but the range of the angle B preferably satisfies 3 ° ≦ B ≦ 15 °.

When the elastic modulus of the tread rubber 30A is E1 [kgf / mm ² ] and the elastic modulus of the tread rubber 30B is E2 [kgf / mm ² ], it is preferable that 1.1 ≦ E1 / E2 ≦ 1.7 is satisfied.
Also, E1 [kgf / mm ^2] range of preferably satisfies ^{11kgf / mm 2 ≦ E1 ≦ 16kgf} / mm 2, the range of E2kgf / mm ² satisfies the ^{7kgf / mm 2 ≦ E2 ≦ 13kgf} / mm 2 It is preferable.
In this embodiment, E1 and E2 are elastic moduli when the rubber temperature is 60 ° C.

(Function)
In the pneumatic tire 10 for a motorcycle according to the present embodiment, since the spiral belt layer 22 is provided on the outer side in the tire radial direction of the carcass 16, the rigidity in the tire circumferential direction of the tread 28 is increased, and the tire diameter of the tread 28 during high speed running is increased. The protrusion to the outside in the direction can be suppressed, and the high-speed durability is improved. Further, by providing the inclined belt layer 24, the lateral bending rigidity is improved, and a high cornering force can be generated during turning.

Furthermore, in the pneumatic tire 10 for a motorcycle according to the present embodiment, the tread 28 is formed of the tread rubber 30A and the tread rubber 30B, and the boundary between the tread rubber 30A and the tread rubber 30B is disposed within the ground contact surface of the tread 28. Further, by making the tread rubber 30A harder than the tread rubber 30B, the lateral bending rigidity and torsional rigidity of the central portion are improved. Further, the lateral bending rigidity of both sides is kept low. As a result, the steering angle responsiveness and lightness during straight traveling are improved, and the grip force during turning is ensured.
Accordingly, the steering angle responsiveness and lightness are improved, the grip force at the time of turning is ensured, and the steering stability performance at the time of high speed running is excellent.

  In addition, since the rigidity step between the tread rubber 30A and the tread rubber 30B is arranged in the ground plane, the discontinuity of the lateral force generation level according to the CA change during turning is eliminated, and the handling linearity is ensured. Excellent handling stability.

  If 0.1W1> W2, since the width W2 of the tread rubber 30A is too narrow, there is little improvement in torsional rigidity at the center, little improvement in rudder angle response and nimbleness, and steering stability performance at high speeds. Getting worse. Therefore, it is preferable that the relationship between W1 and W2 satisfies 0.1W1 ≦ W2. The upper limit value of W2 is less than W1 as defined in claim 1.

  Further, by making the cord of the spiral belt layer 22 made of steel, the grip force due to the high grounding property due to the low lateral bending rigidity of the tire crown portion, and the torsional rigidity by making the cord of the spiral belt layer 22 steel. The improvement in the steering angle response and lightness are improved.

Further, the reinforcing effect of the tire 10 is improved by disposing the inclined belt layer 24 including the cord having an angle B with respect to the tire radial direction between the spiral belt layer 22 and the carcass 16.
At this time, if B <3 °, the cord of the inclined belt layer 24 is substantially parallel to the tire radial direction, so that the effect of improving the torsional rigidity is small, and the improvement of the steering angle response and lightness is small. Further, if B> 15 °, the lateral bending rigidity of the belt layer becomes excessively large, resulting in poor ground contact during turning and a decrease in gripping force. Therefore, the angle B preferably satisfies 3 ° ≦ B ≦ 15 °.

  If 1.1> E1 / E2, the improvement in torsional rigidity at the center is small, the steering angle response and lightness are not improved, and the grip force during turning is also small. If E1 / E2> 1.7, the difference in elastic modulus between rubbers is too large, and the handling linearity may be impaired. Therefore, it is preferable that 1.1 ≦ E1 / E2 ≦ 1.7 is satisfied.

If 11 kgf / mm ² > E1, there is little improvement in the torsional rigidity at the center, so the steering angle response and nimbleness are insufficient. If E1 <16 kgf / mm ² , the bending rigidity at the center (tire circumference) (Direction bending rigidity and lateral bending rigidity) is excessively improved, vibration absorption is impaired, and riding comfort performance is deteriorated.
Further, if 7 kgf / mm ² > E2, the lateral bending rigidity commensurate with the grip force on both sides during turning cannot be ensured, and thus the turning performance deteriorates. If E2> 13 kgf / mm ² , the lateral bending rigidity is If it is too large, the ground contact property is impaired, the gripping power is lowered, and the steering stability performance at the time of turning is deteriorated. Therefore, the elastic modulus E1 satisfies ^{11kgf / mm 2 ≦ E1 ≦ 16kgf} / mm 2, also the elastic modulus E2 preferably satisfies the ^{7kgf / mm 2 ≦ E2 ≦ 13kgf} / mm 2.

  Further, by using the tire 10 as a front wheel, the steering angle responsiveness and lightness of the handling performance are improved, the grip force at the time of turning is ensured, and the steering stability performance at high speed traveling is excellent.

  In this embodiment, the cords of the belt ply 24A are nylon fibers. However, in other embodiments, the material of these cords may be aromatic polyamide fibers (for example, Kevlar: trade name).

[Second Embodiment]
Next, a second embodiment of the pneumatic tire for a motorcycle according to the present invention will be described with reference to FIG. The tire size of the pneumatic tire 10 for a motorcycle according to the present embodiment is MCR180 / 55ZR17M / C as in the first embodiment. As shown in FIG. 2, the pneumatic tire 10 for a motorcycle is different from the first embodiment in that an intersecting belt layer 26 is arranged instead of the inclined belt layer 24, and the other is the first implementation. It is the structure similar to a form. In addition, the same code | symbol is attached | subjected to the same structure as 1st Embodiment, and the description is abbreviate | omitted.

(Intersection belt layer)
The crossing belt layer 26 includes a first belt ply 26A and a second belt ply 26B.

  The first belt ply 26A is formed by arranging a plurality of cords (corresponding to a diameter of 0.5 mm in which nylon fibers are twisted in this embodiment) in parallel in a covering rubber, and in this embodiment, The angle of the cord with respect to the tire radial direction on the tire equatorial plane CL is set to 10 °. The second belt ply 26B is also formed by embedding a plurality of cords (corresponding to a diameter of 0.5 mm in which nylon fibers are twisted in this embodiment) in parallel in the covering rubber. In this embodiment, The angle of the cord with respect to the tire radial direction on the tire equatorial plane CL is set to 10 °.

  Note that the cord of the first belt ply 26A and the cord of the second belt ply 26B intersect with each other, and are inclined in opposite directions with respect to the tire equatorial plane CL. In addition, the cord driving density in the first belt ply 26A and the second belt ply 26B in the present embodiment is 37/25 mm, respectively.

(Function)
In the pneumatic tire 10 for a motorcycle according to the present embodiment, in addition to the effects of the first embodiment, the cord of the crossing belt layer 26 and the steel cord of the spiral belt layer 22 intersect with each other. Torsional rigidity and lateral bending rigidity are further improved. Therefore, the steering angle responsiveness and lightness of handling are improved, and the steering stability is improved because the feeling of rigidity at the time of turning is increased.

  In the present embodiment, the cords of the first belt ply 26A and the cords of the second belt ply 26B are nylon fibers, but in other embodiments, the material of these cords is an aromatic polyamide fiber (for example, , Kevlar: trade name).

[Third Embodiment]
Next, a third embodiment of the pneumatic tire for a motorcycle according to the present invention will be described with reference to FIG. Note that the tire size of the pneumatic tire 10 for motorcycles of the present embodiment (hereinafter simply referred to as the tire 10) is MCR180 / 55ZR17M / C, as in the first embodiment. In the tire 10, as shown in FIG. 3, the tread rubber 30 </ b> A tapers from the tread 28 tread surface side toward the tread 28 bottom surface side, and the boundary between the tread rubber 30 </ b> A and the tread rubber 30 </ b> B is connected at the bottom surface of the tread 28. ing. Specifically, the tread rubber 30A has an inverted triangular shape when viewed from a cross section in the tire width direction. This point is different from the first embodiment, and the other configuration is the same as that of the first embodiment. In addition, the same code | symbol is attached | subjected to the same structure as 1st Embodiment, and the description is abbreviate | omitted.

(Function)
In order for the boundary between the tread rubber 30A and the tread rubber 30B to be connected at the bottom surface of the tread 28, the boundary between the rubber viewed from the cross section in the tire width direction is closer to the tire equator surface on the tread bottom surface side than the tread tread surface side. It is necessary to. In other words, it is necessary to make the boundary an oblique shape. Thereby, the rigidity level | step difference at the boundary of the tread tread surface side can be made small, and the linearity of handling improves.

(Test example)
In order to confirm the performance improvement effect of the pneumatic tire for motorcycles of the present invention, five types of pneumatic tires for motorcycles of examples according to the first embodiment of the present invention, three types of pneumatic tires for motorcycles of comparative examples, In addition, one type of pneumatic tire for motorcycles of a conventional example was prepared, and a steering stability performance comparison test using an actual vehicle was performed. These two-wheeled pneumatic tires (hereinafter simply referred to as tires) were mounted on the front, and conventional tires were mounted on the rear for actual vehicle tests. The evaluation method is as follows.

  In the test, the test tire is mounted on a 1000cc sports-type motorcycle (hereinafter simply referred to as a motorcycle), and the vehicle is run on a test course. The test rider examines the lightness, turning power, and handling characteristics included in the handling stability. The evaluation result is shown in Table 1 as an index display when the steering stability performance of the tire of the spiral belt structure of the conventional example is set to 100. A larger evaluation value indicates a better result.

The size of the test tire is MCR180 / 55ZR17M / C. The tire is mounted on the rim MT5.5 × 17 and the tire is pressurized until the internal pressure becomes 250 kPa.
The tire of the conventional example was the same size, the same rim, and the same pressure as the test tire except that it was composed of one kind of tread rubber and only a spiral belt.

  From the results in Table 1, it can be seen that the tires of Examples 1 to 5 are more excellent in lightness and turning force handling than the tires of Comparative Examples 1 to 3 and the conventional example. Therefore, it can be seen that the tires of Examples 1 to 5 are more excellent in steering stability performance at high speed than the tires of Comparative Examples 1 to 3 and the conventional example.

It is sectional drawing along the rotating shaft of the pneumatic tire for two-wheeled vehicles which concerns on 1st Embodiment. It is sectional drawing along the rotating shaft of the pneumatic tire for two-wheeled vehicles which concerns on 2nd Embodiment. It is sectional drawing along the rotating shaft of the pneumatic tire for motorcycles concerning 3rd Embodiment.

Explanation of symbols

10 Pneumatic tire for two-wheeled vehicle 16 Carcass 18 Bead part 20 Bead core 22 Spiral belt layer 24 Inclined belt layer (belt layer)
26 Cross belt layer 28 Tread 30 Tread rubber 30A Tread rubber 30A
30B Tread rubber 30B

Claims (11)

A bead core embedded in a pair of left and right bead parts;
A carcass composed of at least one carcass ply that spans from one bead portion to the other bead portion in a toroidal shape, and an end portion is wound around the bead core and locked to the bead core;
A belt layer disposed on the outer side in the tire radial direction of the carcass;
A pneumatic tire for a motorcycle including a tread rubber disposed outside the belt layer in a tire radial direction and forming a tread portion that contacts a road surface,
In the tire width direction cross section, the center portion of the tread portion is formed of a first rubber, and the side portions on both sides of the center portion are formed of a second rubber,
The first rubber is harder than the second rubber,
The pneumatic tire for a motorcycle according to claim 1, wherein a boundary between the first rubber and the second rubber is disposed within a contact surface when the tire rotation axis is parallel to the road surface.   2. The pneumatic tire for a motorcycle according to claim 1, wherein 0.1 W <b> 1 ≦ W <b> 2 is satisfied when a width of the ground contact surface is W <b> 1 and a width of the central portion is W <b> 2 in a tire width direction cross section.   The pneumatic tire for a motorcycle according to claim 1 or 2, wherein the cord of the belt layer is made of steel.   4. The belt layer comprises a spiral belt layer formed by spirally winding a belt-like body in which one or a plurality of parallel cords are embedded in a covering rubber. The pneumatic tire for a motorcycle according to any one of the above. The belt layer is a spiral belt layer formed by spirally winding a belt-like body in which one or a plurality of parallel cords are embedded in a covering rubber;
2. An inclined belt layer, which is provided between the spiral belt layer and the carcass and has a plurality of cords extending obliquely with respect to a tire radial direction and embedded in a covering rubber. The pneumatic tire for a motorcycle according to any one of items 1 to 3. The belt layer is a spiral belt layer formed by spirally winding a belt-like body in which one or a plurality of parallel cords are embedded in a covering rubber;
The cord tire is composed of a plurality of belt plies provided between the spiral belt layer and the carcass and in which a plurality of cords arranged in parallel with each other are embedded in a covering rubber, and the belt plies adjacent to each other are adjacent to each other. The pneumatic tire for a motorcycle according to any one of claims 1 to 3, further comprising: an intersecting belt layer whose inclination directions with respect to the radial direction are opposite to each other.   The pneumatic tire for a motorcycle according to claim 5, wherein an angle B of the cord of the inclined belt layer with respect to a tire radial direction satisfies 3 ° ≦ B ≦ 15 °.   The pneumatic tire for a motorcycle according to claim 6, wherein an angle B of the cord of the crossing belt layer with respect to a tire radial direction satisfies 3 ° ≦ B ≦ 15 °.   9. Any one of claims 1 to 8, wherein 1.1 ≦ E1 / E2 ≦ 1.7 is satisfied, where E1 is an elastic modulus of the first rubber and E2 is an elastic modulus of the second rubber. A pneumatic tire for a motorcycle according to claim 1. When the elastic modulus of the first rubber is E1 [kgf / mm ² ] and the elastic modulus of the second rubber is E2 [kgf / mm ² ], 11 kgf / mm ² ≦ E1 ≦ 16 kgf / mm ² and 7 kgf The pneumatic tire for a motorcycle according to claim 9, wherein / mm ² ≦ E2 ≦ 13 kgf / mm ² is satisfied.   The pneumatic tire for a motorcycle according to any one of claims 1 to 10, wherein the pneumatic tire is used for a front wheel of a motorcycle.

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