JP5202153B2 - Pneumatic tires for motorcycles - Google Patents

Description

  The present invention relates to a pneumatic tire for a motorcycle.

When cornering with motorcycle tires, unlike so-called four-wheeled vehicle tires such as passenger cars, trucks, buses, etc., which mainly corner the tire by giving a slip angle, the camber tilts the tire with respect to the road surface. It is necessary to add corners.
For this reason, in a motorcycle tire, the contact area of the tread portion varies greatly between straight traveling and cornering.

  That is, when running straight, the central area of the tread, including the tire equatorial plane, touches the road surface and functions to transmit driving force and braking force to the road surface, and during cornering, the shoulder area including the tread grounding end It functions to contact the road surface and generate a lateral force that opposes the centrifugal force acting on the motorcycle. The intermediate region located in the middle of these regions transmits a driving force and a braking force to the road surface, for example, at a corner rise, and also functions to generate a lateral force against the centrifugal force at the cornering. Will do.

  Therefore, as the tread rubber disposed in the tread portion of the tire for a motorcycle, each function as described above is provided in each grounding region only by selecting a single rubber type or a single rubber hardness. Could not be fully demonstrated.

  Thus, for example, Patent Document 1 discloses that a tread is divided into five regions including a center region, a pair of shoulder regions, and a pair of intermediate regions located between the center region and the shoulder region. By making the 300% modulus of the rubber composition in the region smaller than the 300% modulus of the rubber composition in the center region and larger than the 300% modulus of the rubber composition in the shoulder region, There is a motorcycle tire that is intended to prevent a 300% modulus from changing abruptly in the transition to the middle region, the transition from the middle region to the center region, the transition from the shoulder region to the middle region, and the transition from the middle region to the shoulder region. Have been described.

However, although the pneumatic tire for a motorcycle described in Patent Document 1 does not cause a sharp change in gripping property at the time of transition from straight traveling to turning, and at the time of transition from turning to straight traveling, in particular, , The driving force and lateral force generated as the force against the centrifugal force at the corner rise during cornering, etc., and the road surface holding power and gripping force are still insufficient with respect to the unevenness of the road surface. There was anxiety about running stability due to slippage due to lack of.
JP 2007-168531 A

  Accordingly, the present invention provides a pneumatic tire for a motorcycle that has improved drivability and braking performance, particularly when imparting a middle camber angle to the tire without worrying about running stability.

A pneumatic tire for a motorcycle according to the present invention includes a tread portion including a tread rubber having a layer structure of one or more layers, and a pair of sidewall portions extending inward in the tire radial direction continuously to each side portion of the tread portion. And a bead portion continuous in the tire radial direction inside these sidewall portions, wherein the tread portion has a ground contact region including a central region including a tire equatorial plane and a pair of shoulders including a tread ground contact end. 100% of the portion that forms at least the ground contact surface of the intermediate tread rubber, which is composed of five regions including a region and a pair of intermediate regions located between the central region and the shoulder region. The modulus is 100% of the portion of the central tread rubber disposed over the entire central region that forms at least the ground plane. Las and shoulder tread rubber disposed over the whole of the shoulder region, rather smaller than any of the 100% modulus of a portion forming at least the ground surface, the approximation of the joint line between the central tread rubber and the intermediate tread rubber While extending the virtual virtual extension component of the straight line and the virtual extension component of the approximate straight line of the joint line between the intermediate tread rubber and the shoulder tread rubber in a direction that intersects the tire equatorial plane inside the tire, The angle of intersection on the tire equatorial plane side between the approximate straight line of the joint line between the central tread rubber and the intermediate tread rubber and the tangent drawn to the joint point on the ground contact surface of the central tread rubber and the intermediate tread rubber is α, An approximate straight line of a joining line between the intermediate tread rubber and the shoulder tread rubber, the intermediate tread rubber, and The intersection angle β is smaller than the intersection angle α, where β is the angle of intersection on the tire equatorial plane side with the tangent drawn to the junction point on the ground contact surface of the shoulder tread rubber .
Here, “tread rubber having a layer structure of one or more layers” means not only a case where the tread rubber of the tread portion has a single layer structure but also a tread rubber having a laminated structure such as a cap-and-base structure. is there.

  Here, 100% modulus is a value obtained by preparing a JIS dumbbell-shaped No. 3 sample, performing a tensile test at a speed of 500 ± 25 mm / min at room temperature in accordance with JIS K6251, and measuring the tensile stress.

  In such a tire, it is more preferable that the shoulder tread rubber has a 100% modulus of at least a portion forming the ground contact surface smaller than a 100% modulus of the central tread rubber at least a portion forming the ground contact surface.

  Also preferably, the 100% modulus of at least the portion of the intermediate tread rubber that forms the ground contact surface is in the range of 1.0 to 1.5 MPa.

  More preferably, the central tread rubber has a 100% modulus of at least a portion forming the ground contact surface in a range of 1.3 to 1.8 Mpa, and the shoulder tread rubber has a 100% modulus of at least a portion forming the ground contact surface. 1.1 to 1.6 Mpa.

And preferably, the peripheral length of the ground contact surface of the intermediate tread rubber in the meridian section of the tire is in a range of 20 to 80% of the total peripheral length of the ground contact region.
Here, “periphery length” means JATMA (Japan Automobile Tire Association) YEAR BOOK in Japan, ETRTO (European Tire and Rim Technical Organization) STANDARD IN MANUAL, and TRA (THE TIRE IN C ARIA) in the United States. After assembling the tire to the applicable rim specified by the BOOK, the length in the tread width direction measured along the tread surface under the internal pressure filled with the maximum air pressure specified by JATMA etc. It shall be said.

  More preferably, the peripheral length of the contact surface of the central tread rubber in the meridian cross section of the tire is in the range of 10 to 35% of the total peripheral length of the contact region, and the peripheral length of the contact surface of the shoulder tread rubber is This range is 5 to 35% of the total peripheral length of the grounding region.

  In any of the tires described above, it is preferable to use the tire for mounting a rear wheel of a motorcycle.

  In pneumatic tires for motorcycles, the center area that contacts the ground when traveling straight ahead must have physical properties that are suitable for efficiently transmitting the driving and braking forces to the road surface. It is necessary to have physical properties suitable for generating force. In addition to the efficient road surface transmission of driving force and braking force at the corner rising, etc., the physical property that generates sufficient lateral force is given to the middle region of the tread part located between both regions It becomes necessary to do.

  Therefore, in the pneumatic tire for motorcycles of the present invention, attention was paid to the modulus of the tread rubber as an index of rigidity against the extension of the tread portion due to external force. In this case, as a measure of the modulus, 100% modulus, which is a value at 100% elongation at which data is relatively stable, was adopted.

  Then, 100% modulus of at least the portion forming the ground contact surface of the intermediate tread rubber disposed over the entire intermediate region is 100 of the portion forming at least the ground contact surface of the central tread rubber disposed over the entire central region. In particular, the cornering in which the middle camber angle is imparted to the tire is achieved by reducing the% modulus and the shoulder tread rubber disposed over the entire shoulder region to be smaller than at least the 100% modulus of the portion forming the ground contact surface. The large grip force applied at the time of acceleration, such as time and corner rise, can increase the envelope property against unevenness of the road surface and improve the road surface holding force, and can exert a lateral force sufficient to counter the centrifugal force .

Hereinafter, a pneumatic tire for a motorcycle will be described in detail with reference to the drawings.
FIG. 1 is a meridian cross-sectional view showing an embodiment of a pneumatic tire for a motorcycle .

  In the figure, 1 is a tread portion, 2 is a pair of sidewall portions extending radially inward continuously to the respective side portions of the tread portion 1, and 3 is a bead continuing radially inward of the sidewall portion 2. Each part is shown.

  This tire has a carcass 5 in which a side portion is folded around a bead core 4 of a bead portion 3 from a tread portion 1 through a sidewall portion 2. As shown in the figure, the carcass 5 is constituted by a single carcass ply, but the carcass can also be constituted by a plurality of carcass plies.

A belt 6 made of at least one reinforcing cord layer is disposed on the outer peripheral side of the crown region of the carcass 5, and this belt 6, for example, includes one or a plurality of rubber-coated cords in the tire circumferential direction. It can be set as what is called a spiral belt structure wound continuously by the extended attitude to.
A tread rubber 7 that extends in an arc shape to the maximum width position of the tire and forms a ground contact region of the tread portion 1 is provided on the outer peripheral side of the belt 6. Further, side rubbers 8 that contribute to the formation of the sidewall portions 2 are provided on both sides of the tread rubber 7.
Furthermore, although omitted in FIG. 1, a required groove can be formed on the surface of the tread rubber 7.

  In the tire shown here, the contact area of the tread portion 1 includes a center area A that includes the tire equatorial plane in the center, a shoulder area C that includes the tread contact end, a center area A, and a shoulder area C. The shoulder region C and the intermediate region B are formed in pairs at positions that are symmetric with respect to the equator plane, respectively.

Further, here, the tread rubber 7 disposed in each of the regions has a single-layer structure, and the 100% modulus of the intermediate tread rubber 7b disposed over the entire intermediate region B is set over the entire central region A. It is made smaller than the 100% modulus of the central tread rubber 7a disposed and the 100% modulus of the shoulder tread rubber 7c disposed over the entire shoulder region C.
Here, more preferably, the 100% modulus of the shoulder tread rubber 7c is made smaller than the 100% modulus of the central tread rubber 7a.

  In a tire for a motorcycle, the center area A of the tread portion 1 of the tire is mainly grounded during straight traveling, while the ground contact area of the tire is shouldered from the center area A of the tread portion 1 by giving a camber angle during cornering traveling. Transition to region C. Comparing the frequency of straight travel and cornering travel, since the frequency of straight travel is much higher, 100% modulus rubber with high wear resistance is placed in the center area A, and the grip in the shoulder area C By disposing rubber with a low 100% modulus that places emphasis on the force and holding force on the uneven road surface, a tire excellent in both wear resistance and cornering properties can be obtained.

  And, by setting the 100% modulus of the intermediate tread rubber 7b in the range of 1.0 to 1.5 Mpa, sufficient grip force is secured to generate lateral force and driving force at the corner rising or the like. Can do.

  When the 100% modulus of the intermediate tread rubber 7b is less than 1.0 Mpa, the wear life of the intermediate tread rubber 7b is insufficient due to insufficient wear resistance. When the intermediate tread rubber 7b exceeds 1.5 Mpa, the holding force on the road surface is insufficient and sufficient. There is a tendency that the grip power cannot be exhibited.

  By setting the 100% modulus of the central tread rubber 7a in the range of 1.3 to 1.8 Mpa and the 100% modulus of the shoulder tread rubber 7c in the range of 1.1 to 1.6 Mpa, the wear life and moderate Safe handling performance can be achieved, and both economy and safety can be achieved.

  When the 100% modulus of the central tread rubber 7a is less than 1.3 Mpa, the wear resistance is insufficient, a sufficient wear life cannot be secured, and the economic efficiency is lowered. When the center tread rubber 7a exceeds 1.8 Mpa, the road surface holding force is deteriorated and The driving safety tends to decrease due to a decrease in grip force.

  When the 100% modulus of the shoulder tread rubber 7c is less than 1.1 Mpa, the steering stability during cornering is lowered. When the shoulder tread rubber 7c exceeds 1.6 Mpa, the grip force is insufficient due to the decrease in the road surface holding force and the turning performance is lowered. Tend.

More preferably, in a meridional section of the tire, the periphery length L _b of the ground contact surface of intermediate tread rubber 7b, 20 to 80% of the total periphery length L of the ground area.

In the meridional section of the tire, the periphery length L _b of the ground contact surface of intermediate tread rubber 7b, by 20 to 80% of the total periphery length L of the ground area, during acceleration of the rising or the like of the corner , Can demonstrate sufficient grip.

Periphery length L _b of the ground contact surface of intermediate tread rubber 7b is less than 20% of the total periphery length L of the ground area, during acceleration of the rising or the like of the corner, it is impossible to ensure a sufficient grip, 80 When it exceeds%, the intermediate tread rubber 7b having a low modulus enters the central region A, and uneven wear resistance tends to decrease.

Also preferably, in a meridional section of the tire, the periphery length L _a of the ground plane of the central tread rubber 7a, and 10 to 35% of the total periphery length L of the ground area, contact of the shoulder tread rubber 7c the periphery length L _c of the ground, to 5 to 35% of the total periphery length L of the ground area.

In the meridional section of the tire, the periphery length L _a of the ground plane of the central tread rubber 7a, and 10 to 35% of the total periphery length L of the ground area, periphery length of the ground plane of the shoulder tread rubber 7c By setting the length L _c to be in the range of 5 to 35% of the total peripheral length L of the ground contact region, it is possible to deal with each of retention, driving performance and cornering performance during straight traveling and cornering.

Periphery length L _a of the ground plane of the central tread rubber 7a is less than 10% of the total periphery length L of the ground area, since the low rigidity intermediate tread rubber 7b enters the ground area during straight, wear resistance If it exceeds 35%, rubber with high rigidity enters the middle region, so that the unevenness of the road surface tends to deteriorate and grip performance tends to deteriorate.

Periphery length L _c of the ground contact surface of shoulder tread rubber 7c is less than 5% of the total periphery length L of the ground area, as a result of low rigidity intermediate tread rubber 7b enters large ground area when cornering, than necessary When the rigidity is reduced and a large camber angle is applied, the intermediate tread rubber 7b collapses and falls down, resulting in a decrease in handling performance. If it exceeds 35%, rubber with high rigidity enters the intermediate region B. There is a tendency for grip performance to decrease.

FIG. 2 is a meridian cross-sectional view showing one embodiment of a pneumatic tire for motorcycles of the present invention.
In the pneumatic tire for a motorcycle, an approximate straight line j1 of the joint line between the center tread rubber 7a and the intermediate tread rubber 7b, and an approximate line of the joint line between the intermediate tread rubber 7b and the shoulder tread rubber 7c. The virtual extension line segment of j2 is inclined and extended in the direction intersecting the tire equator plane inside the tire, the approximate straight line j2 of the joint line between the intermediate tread rubber 7b and the shoulder tread rubber 7c, and their treads The intersection angle β on the tire equatorial plane side with the tangential line drawn at the joint point on the rubber ground surface, the approximate straight line j1 of the joint line between the central tread rubber 7a and the intermediate tread rubber 7b, and the ground surface of these tread rubbers The angle of intersection with the tangential line drawn at the junction at the tire equatorial plane side is smaller than α.
Thus, the shoulder tread rubber 7c, which is grounded during cornering with a large camber angle, is peeled off from the joint point between the intermediate tread rubber 7b and the shoulder tread rubber 7c on the grounding surface against the lateral force received from the road surface by centrifugal force. It is possible to reduce the lateral force component in the direction and improve the peeling resistance.

  By the way, in the case of a motorcycle, since the rear wheel (rear) is a driving wheel, the present invention is effective when applied to a tire for mounting a rear wheel. Therefore, the present invention is preferably applied to a tire for mounting a rear wheel.

Next, Example tire 1 to Example tire 5 having a structure as shown in FIG. 2 and having a rear tire size of 190 / 50ZR17, provided with one steel monofilament spiral belt and two nylon carcass, and Comparative Example Tire 1 to Comparative Example Tire 6 were prototyped, and the grip properties, wear resistance, and handling properties were evaluated when the respective specifications were changed as shown in Tables 1 and 2.
In each evaluation, the value of Comparative Example Tire 1 was set to 100 and indicated as an index. It shows that it is so favorable that a numerical value is large.
The front tire was 120 / 70ZR17 in size, and was reinforced as one steel monofilament spiral belt and two rayon carcass.
In the present invention, since the tire structure other than the tread portion does not require modification, the tire structure is substantially the same as that of a conventional pneumatic tire for motorcycles.

(Test method)
(Grip property)
Each test tire is mounted on a rim with a rim size of MT 6.00 × 17, the internal pressure is 290 kPa, a 1000 cc actual vehicle, a load of 300 kg, a test speed of 40 to 250 km / h, a traveling distance of 10 km, and a camber angle Table 3 shows the grip performance evaluated by the rider's feeling by repeatedly running at 0 to 50 °.

(Abrasion resistance)
Each test tire is mounted on a rim with a rim size of MT 6.00 × 17, the internal pressure is 290 kPa, a 1000 cc real vehicle, a high-speed peripheral circuit with a load of 300 kg, a test speed of 40 to 250 km / h, a travel distance of 10 km, and a camber angle Table 3 shows the wear resistance evaluated by reducing the groove depth when the vehicle is repeatedly run at 0 to 50 °.

(Handling properties)
Each test tire is mounted on a rim with a rim size of MT 6.00 × 17, the internal pressure is 290 kPa, a 1000 cc actual vehicle, a load of 300 kg, a test speed of 40 to 250 km / h, a traveling distance of 10 km, and a camber angle Table 3 shows the handling performance evaluated with the feeling of the evaluation rider.

  From the results of Table 3, Example Tire 1 to Example Tire 5 were able to improve grip properties without impairing wear resistance and handling performance compared to Comparative Example Tire 1 to Comparative Example Tire 6.

1 is a cross-sectional view in the width direction showing an example of a pneumatic tire for a motorcycle . 1 is a cross-sectional view in the width direction showing one embodiment of a pneumatic tire for a motorcycle of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Carcass ply 6 Belt 7 Tread rubber 7a Center tread rubber 7b Middle tread rubber 7c Shoulder tread rubber 8 Side rubber A Center area B Middle area C Shoulder area

Claims (7)

A tread portion including a tread rubber having a layer structure of one or more layers, a pair of sidewall portions extending inward in the tire radial direction continuously to the respective side portions of the tread portion, and inward of the tire radial direction of these sidewall portions. In a pneumatic tire for a motorcycle having a continuous bead portion,
The contact area of the tread portion is composed of five areas: a center area including the tire equatorial plane, a pair of shoulder areas including the tread contact edge, and a pair of intermediate areas positioned between the center area and the shoulder area. 100% modulus of at least the portion forming the ground contact surface of the intermediate tread rubber disposed over the entire intermediate region is at least the portion of the central tread rubber disposed over the entire central region forming the ground contact surface. 100% modulus and, shoulder tread rubber disposed over the whole of the shoulder region, rather smaller than any of the 100% modulus of a portion forming at least the ground surface,
The virtual extension component of the approximate straight line of the joint line between the center tread rubber and the intermediate tread rubber, and the virtual extension component of the approximate straight line of the joint line between the intermediate tread rubber and the shoulder tread rubber are provided inside the tire. Inclined and extended in a direction intersecting the equator plane, an approximate straight line of the joint line between the central tread rubber and the intermediate tread rubber, and a joint point on the ground contact surface of the central tread rubber and the intermediate tread rubber The angle of intersection on the tire equatorial plane side with the drawn tangent line is α, the approximate straight line of the joining line between the intermediate tread rubber and the shoulder tread rubber, and the joining point on the ground contact surface of the intermediate tread rubber and the shoulder tread rubber When the angle of intersection with the drawn tangent on the tire equatorial plane side is β,
The pneumatic tire for a motorcycle , wherein the intersection angle β is smaller than the intersection angle α .   The pneumatic tire for a motorcycle according to claim 1, wherein the shoulder tread rubber has a 100% modulus of at least a portion forming the ground contact surface smaller than a 100% modulus of the central tread rubber at least a portion forming the ground contact surface.   The pneumatic tire for a motorcycle according to claim 1 or 2, wherein a 100% modulus of at least a portion forming the ground contact surface of the intermediate tread rubber is in a range of 1.0 to 1.5 Mpa.   The central tread rubber has a 100% modulus of at least a portion forming the ground contact surface in the range of 1.3 to 1.8 Mpa, and the shoulder tread rubber has a 100% modulus of at least a portion forming the ground contact surface of 1. The pneumatic tire for a motorcycle according to any one of claims 1 to 3, which is in a range of 1 to 1.6 Mpa.   5. The motorcycle according to claim 1, wherein a peripheral length of a ground contact surface of the intermediate tread rubber in a meridian cross section of the tire is in a range of 20 to 80% of a total peripheral length of the ground contact region. Pneumatic tire.   Within the meridian section of the tire, the peripheral length of the ground contact surface of the central tread rubber is in the range of 10 to 35% of the total peripheral length of the ground contact region, and the peripheral length of the ground contact surface of the shoulder tread rubber is The pneumatic tire for a motorcycle according to any one of claims 1 to 5, which is in a range of 5 to 35% of a total peripheral length of the region.   The pneumatic tire for a motorcycle according to any one of claims 1 to 6, which is a tire for mounting a rear wheel of a motorcycle.

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