WO2007023895A1

WO2007023895A1 - Pneumatic tire for bicycle

Info

Publication number: WO2007023895A1
Application number: PCT/JP2006/316609
Authority: WO
Inventors: Makoto Ishiyama; Hiroyuki Matsumoto; Shinsaku Katayama
Original assignee: Bridgestone Corporation
Priority date: 2005-08-25
Filing date: 2006-08-24
Publication date: 2007-03-01
Also published as: JP2007055510A; JP4814582B2

Abstract

A pneumatic tire for a bicycle in which turning performance on a wet pavement is enhanced as compared with that of a conventional tire. Assuming the region of 60% of the development width of a tread (28) is a tread central portion and the outside of the tread central portion in the direction of tire width is a tread side portion, a plurality of inclination grooves (50) are formed in the tread side portion and an elongated land portion (56) is sectioned on the tread side portion such that the length in the extending direction is three times or more the width and the ratio t/h between the height h and the width t becomes 0.6-2.0. Consequently, both drainage performance and block rigidity can be satisfied at a high level at a ground contacting portion during turning, and a higher grip force than before can be attained during turning on a wet pavement.

Description

Specification

Pneumatic tires for motorcycles

Technical field

[0001] The present invention relates to a pneumatic tire for a motorcycle, and more particularly to a pneumatic tire for a motorcycle that can improve turning performance on a wet road surface.

Background art

[0002] When a tire travels on a wet road surface, a groove is arranged in the tread portion in order to obtain a road surface that is not obstructed by the rubber force water film on the tread surface and a good ground contact state (example) For example, see Patent Document 1.)

That is, the groove disposed in the tire tread portion serves as an escape route for the water squeezed by the tread and the road surface, and has a role of efficiently draining the water.

[0003] On the other hand, the groove arranged in the tread divides the tread into blocks of land, which reduces the rigidity of the tread. Therefore, in the tread land, the road surface and the tire surface are grounded. When braking force, driving force, or lateral force is applied, it tends to fall down due to shear deformation. When such a fall occurs, the tread itself moves and the rider immediately feels that the tires are unstable, and because the tread falls, a part of the tread surface floats off the road surface and the grip area decreases. Power is reduced. This is a force that occurs even on wet roads. In the case of commercially available tires, you must run on both wet and dry roads. It becomes a big problem even on the road surface.

Such block lift of road force is a major problem because it induces uneven wear.

[0004] Regarding the tread pattern of a two-wheeled vehicle, the way in which the grooves are arranged is technically difficult, and is a major factor that affects wet performance.

Therefore, the tire pattern is determined with a good balance between the groove layout that can drain water efficiently, the groove layout that does not reduce the rigidity of the tread, and the good design.

[0005] In addition, unlike tires for passenger cars and trucks, motorcycle tires tilt the vehicle body. Due to the characteristics of a motorcycle that turns, the tread part that touches the road surface differs between straight running without tilting the vehicle and cornering when tilting the vehicle.

Therefore, in motorcycle tires, there are cases in which the pattern inclination is characterized on the center side and on the shoulder side.

[0006] That is, the groove is arranged on the center side so that the torque is stronger than the input in the front-rear direction (= equator direction = circumferential direction) of the tire, and the input on the width direction of the tire (lateral force) on the shoulder side The groove arrangement is strong against both the tire input in the circumferential direction (traction and brake).

As for the shoulder side, considering that the car is tilted and turning, the lateral force is mainly applied when turning at a constant speed without opening the accelerator or without applying the brake, and when accelerating from turning at a constant speed. Since the driving force is applied and both the lateral force and the driving force are applied, the shoulder side needs to have a pattern strong against both the lateral force and the driving force.

[0007] Especially in the case of a motorcycle race, steering stability performance is particularly important during turning. When cornering in rainy weather, tires with low wet turning performance cannot speed up and the lap time cannot be shortened. In addition, even in commercial vehicles, tires with poor wet turning performance on ordinary roads may slip.

Patent Document 1: Japanese Patent Laid-Open No. 2003-211917

Disclosure of the invention

Problems to be solved by the invention

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to provide a pneumatic tire for a motorcycle that can improve the turning performance on a wet road surface as compared with a conventional tire.

Means for solving the problem

[0009] Regarding the wet performance, conventionally, the depth of the groove, the width of the groove, and the volume of the groove have been regarded as important. Furthermore, the land shape and the land height (ie, the depth of the groove agree) are important for the land section separated by grooves. As described above, a tire having a good grip with respect to lateral force and braking / driving force is necessary for the shoulder side of a motorcycle tire.

[0010] Considering the characteristics of the vehicle body, the driving force is applied to the rear wheel tire. Therefore, the rear wheel tire needs to be gripped particularly with respect to the driving force.

The front wheels, on the other hand, have no driving force, but a large braking force is applied to the tire because the vehicle load is applied to the front wheel tire during braking. The front wheels must have a front-rear grip corresponding to the brake and a lateral grip against the lateral force.

[0011] When attention is paid to the wet performance when the vehicle turns, the shoulder side (tread end side) of the tread portion contacts the road surface. Thinking about the groove shape on the shoulder side of the tread, the tread groove is a force that increases drainage performance when it is thinned. The rigidity of the tread decreases, the tread behaves softly and there is no rigidity! Part of the land rises from the road surface and the ground contact area is reduced, resulting in a decrease in grip. This is a problem if the land is chopped too much with a slender groove.

[0012] On the other hand, if there are not too many grooves on the land, water will not flow easily and hydroplaning will occur. The fact that there are few grooves in the land means that the width of the land is wide, and the land is slightly tilted by traction and lateral force. descend.

As described above, the land portion may not be too rigid or too weak.

[0013] The inventor paid attention to such a phenomenon and conducted extensive research. As a result, by optimizing the shape of the land portion, the contact state between the land portion and the road surface at the time of wet road surface turning is improved. I discovered that the grip was improved.

[0014] The invention according to claim 1 has been made in view of the above-mentioned facts, and has a plurality of land portions partitioned by a plurality of grooves in a tread, and the length is within the plurality of land portions. Is a pneumatic tire for motorcycles that includes a slender land part that is more than three times the width of the tire.The center of the tread is the area where 60% of the developed width of the tread is centered on the tire equatorial plane. When the outside in the width direction is the tread side, at least a part of the elongate land is arranged on the tread side, the height of the elongate land is h, and the width of the elongate land is t In addition, it is characterized in that t / h satisfies 0.6 to 2.0 in the region of 70% or more of the elongated land length. [0015] First, in the present invention, the reason for limiting the range to 0.6 to 2.0 for tZh, which is the ratio of the width t of the elongated land portion to the height h of the elongated land portion. Will be explained.

The inventor prepared several types of block samples and conducted an experiment to see the deformation of the block. As shown in Fig. 7 (A), the size of the block sample 100 is 8 mm high, 30 mm deep, and 30 mm long. This block sample 100 is made of the average tread rubber used in motorcycle tires. The block sample 100 is formed with land portions 104 partitioned by grooves 102, and several types of block samples 100A to G having different ratios tZh of the height h of the land portion 104 and the groove width t are prepared (Fig. (See 8.)

[0016] Specifically, block samples 100A to 100A having eight, six, five, four, three, two, and one land portion 104 were prepared. The shape of the groove 102 is a rectangular parallelepiped, and the depth of the groove 102 is 6 mm. That is, the land portions 104 obtained by digging the grooves 102 in the block are all rectangular parallelepipeds.

In addition, the ratio of the block area to the groove area (negative rate) was processed so that all samples were the same.

[0017] As shown in FIG. 7A, using these block samples 100A to 100G, an experiment was performed in which a shearing force was applied on a glass plate 106 simulating a wet road surface.

The glass plate 106 is 10 mm thick and has a sufficient width. On one side, narrow grooves 108 with a width of 0.5 mm and a depth of 0.5 mm are regularly processed in a grid pattern at intervals of 1 mm. Yes.

[0018] The surface of the glass plate 106 on which the groove 108 was formed was placed horizontally with the road surface being considered, and water was sufficiently sprayed thereon to create a wet road surface state. The block sample 100 has its base part (the upper part in Fig. 7 (A)) fixed to a smooth iron plate (not shown) with an adhesive so that the base part is always kept horizontal, with a force F of 200N. Press vertically against the glass surface.

[0019] The block sample 100 is pressed with a force of 200 N for 2 seconds, and the force is also a speed of 20 mmZ seconds, and the block sample 100 is moved in a direction perpendicular to the groove 102 of the block sample 100 (arrow B direction). At this time, the force applied in the moved direction was defined as Fx, and the Fx was measured.

As shown in Fig. 7 (B), this Fx increased in movement starting force, peaked at a certain point, and then settled to a constant value. This is because the block sticks to the road surface and begins to slide Represents the change in the coefficient of friction up to That is, the change until the state changes from sticking friction to sliding friction.

[0020] A value obtained by dividing the maximum Fx value by a vertical load of 200 N was defined as a friction coefficient. Such an experiment was performed 10 times on one sample, and the average value was taken as the coefficient of friction of the sample. Fig. 9 (A) shows the results of organizing the data with tZh representing the land shape on the horizontal axis and the friction coefficient on the vertical axis. As a result, it was found that the friction coefficient was maximized when tZh was a certain value.

From these research results, it is clear that the elongated land portion has a high friction coefficient when tZh is set to 0.6 to 2.0, which is the basis for the numerical limitation of the present invention. Yes.

[0021] The reason why t / h has an optimum value is as follows. When t / h is less than 0.6, the block easily falls down due to the lateral shearing force that weakens the rigidity of the block. As a result, the contact area between the block and the glass surface (road surface) is reduced. Decrease. In other words, the ratio of the part that rises to V is large! / (See Fig. 9 (B)).

On the other hand, when tZh is larger than 2.0, the phenomenon shown in Fig. 9 (D) occurs. That is, the rigidity of the block is very high and the amount of lateral deformation is small, but if the block is tilted even a little, most of the ground contact surface will be lifted off the road surface. In other words, since the width t is wide, a slight inclination deformation of the block has a great influence and reduces the ground plane.

Fig. 9 (C) is within the appropriate range of tZh, which is numerically limited by the present invention, and the floating ratio of the block (based on the tread area of the block) is moderately suppressed.

[0022] In the pneumatic tire for a motorcycle according to claim 1, when the length is set to be not less than three times the width, the ratio tZh between the height h and the width t is from 0.6 to 2.0. Since it is arranged on the tread side of at least a part of the satisfactory slender land portion, the contact state between the land portion and the road surface when turning on a wet road surface is improved, and the grip force can be improved.

[0023] The invention according to claim 2 is the pneumatic tire for a motorcycle according to claim 1, wherein the elongated land portion is disposed at an angle with respect to the tire circumferential direction and spaced apart in the tire circumferential direction. It is characterized by being formed between the grooves having.

Next, the operation of the pneumatic tire for a motorcycle according to claim 2 will be described.

The grooves defining the elongated land portions have an angle with respect to the tire circumferential direction. It is not a circumferential groove. This is because the elongated land portion is provided on the tread side portion, and the tread side portion contacts the ground when the vehicle is tilted. Considering the case where the vehicle body is tilted (that is, including the behavior of a motorcycle starting to turn while applying a brake, the behavior of continuing to turn at a certain inclination, and the behavior of accelerating from the rotation and standing the vehicle upright) The side is grounded, and the lateral force is applied to the tread side in addition to the lateral force.

Because the front wheels are mainly responsible for braking in addition to turning, both lateral force and braking force are applied when the brake is applied. At this time, the force applied to the tread side is in an oblique direction, and if the groove is inclined along this direction, the grip can be kept high.

[0025] On the other hand, lateral force and driving force are simultaneously applied to the rear wheels when the vehicle is tilted to accelerate the state force accelerator. Since the force applied to the tread is oblique, it is preferable to set an inclination angle for the elongated land portion disposed on the tread side portion. Therefore, Claim 2 stipulates that an angle is given to the circumferential direction.

The inclination angle may be 90 degrees, but in this case, the groove is in the tire width direction and the tread is very strong against lateral force. The distance between the grooves may be equal. However, the sound generated when the land hits the road surface is generated at regular intervals when the land is equally spaced. Since the level is bad, usually, a device that shifts the interval (so-called pitch noiration) is made.

[0026] The invention according to claim 3 is the pneumatic tire for a motorcycle according to claim 2, wherein the elongated land portion continuously extends in the tread deployment width direction over 10% of the entire tread width. It is characterized by that.

Next, the operation of the pneumatic tire for a motorcycle according to claim 3 will be described.

Even if the elongated land portion extends continuously in the tire width direction, if the extended length is less than 10% of the total width of the tread, the proportion of the pattern in the pattern is small and depends on the other components of the pattern. The wet turning performance is affected, and the effect of the elongated land according to the present invention is reduced. Note that the elongated land portion may extend over the entire width direction of the pattern.

[0027] The invention according to claim 4 is the elongated pneumatic tire for motorcycles according to claim 3. Tilt the land so that it is positioned in the tire rotation direction on the shoulder side and on the tire equator side! /, Characterized by that!

Next, the operation of the pneumatic tire for a motorcycle according to claim 4 will be described.

In a two-wheeled vehicle, braking force and lateral force are mainly applied to the front wheels, and driving force and lateral force are mainly applied to the rear wheels. The lateral force is the same for the front and rear wheels, but the front and rear force is the braking force for the front wheels and the driving force for the rear wheels.

In other words, on the front wheels, it is possible to incline the inclined groove so that the shoulder side is located in the tire rotation direction relative to the tire equatorial plane side.When lateral force and braking are applied simultaneously, the direction of the resultant force is the inclination of the inclined groove. It is preferable to suppress the deformation of the land part.

[0029] The invention according to claim 5 is the pneumatic tire for a motorcycle according to claim 3, wherein the elongated land portion is inclined so that the tire equatorial plane side is positioned in the tire rotation direction more than the shoulder side! /, Characterized by that!

[0030] Next, the operation of the pneumatic tire for a motorcycle according to claim 5 will be described.

As explained in the operation of claim 4, the driving force and the lateral force are mainly applied to the rear wheel. In the rear wheel, it is possible to incline the inclined groove so that the tire equatorial plane side is positioned more in the tire rotation direction than the shoulder side. When lateral force and driving force are applied simultaneously, the direction of the resultant force is the inclination of the inclined groove. It is in the shape along the line, and is preferable in suppressing the deformation of the land.

[0031] The invention according to claim 6 is the pneumatic tire for a motorcycle according to claim 4 or claim 5, wherein the angular force of the center line in the width direction of the elongated land portion with respect to the tire circumferential direction is from the tire equatorial plane side to the shoulder side. It is characterized in that it is set within a range of 10 to 30 degrees on the tire equator side and within a range of 50 to 90 degrees on the shoulder side.

Next, the operation of the pneumatic tire for a motorcycle according to claim 6 will be described.

When two-wheeled vehicles are to be deeply cornered, the body should be greatly tilted while turning and the area near the tread edge of the tire should be used. At this time, since the lateral force acts on the tire more than the longitudinal force, the elongated land near the tread end extends in the direction along the lateral force, that is, on the shoulder side. Then, it is preferable to set the angle of the width direction center line of the elongated land part within the range of 50 to 90 degrees.

This is the same regardless of whether the front wheel tire or the rear wheel tire is used. [0033] On the other hand, when considering the escape from a corner that accelerates from a state in which the vehicle body is greatly inclined, in addition to lateral force, driving force is applied to this in the case of a rear wheel. As the vehicle accelerates, the fallen body gradually approaches its upright position. In other words, the place where the tire is in contact with the ground moves from the end side of the tire to the tire equatorial plane side with acceleration. Here, the rate of lateral force decreases with acceleration, and the rate of acceleration force increases, so the resultant force also approaches the lateral force of the tire.

In addition, the front wheel tire is normally subjected to a braking force S under a relatively small inclination angle of the vehicle body.

Therefore, on the shoulder side, the angle of the center line in the width direction of the elongated land part may be 50 to 90 degrees, and on the tire equator side, the angle of the center line in the width direction of the elongated land part may be in the range of 10 to 30 degrees. preferable.

It is preferable to set the angle of the center line in the width direction of the elongated land portion symmetrically on the right and left sides of the tire equator because the tire performance does not change between right turn and left turn.

[0034] Further, in the middle part between the tire equatorial plane side and the shoulder side, the angle between the tire equatorial plane side groove and the shoulder side groove is set to an intermediate angle, and the tire equatorial plane side force gradually increases toward the shoulder side. It is preferable to make it.

The invention's effect

As described above, according to the pneumatic tire for a motorcycle of the present invention, there is an excellent effect that the turning performance on the wet road surface can be improved as compared with the related art.

Brief Description of Drawings

FIG. 1 is a cross-sectional view along the rotational axis of a pneumatic tire for a motorcycle according to a first embodiment.

FIG. 2 is a development view of a tread of a pneumatic tire for a motorcycle according to a first embodiment (Example 1 in a test).

FIG. 3 is a development view of the tread of Example 2.

FIG. 4 is a development view of the tread of Example 3.

FIG. 5 is a development view of the tread of Example 4.

FIG. 6 is a development view of the tread of Comparative Example 1. [FIG. 7] (A) is an explanatory diagram showing a test of a block sample, and (B) is a graph showing a test result.

[FIG. 8] (A) to (G) are side views of the block sample.

[FIG. 9] (A) is a graph showing the coefficient of friction obtained for the test result force, and (B) to (D) are side views showing the deformation state of the block.

Explanation of symbols

[0037] 10 Pneumatic tires for motorcycles

28 tread

50 inclined grooves

56 Land

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of a pneumatic tire for a motorcycle according to the present invention will be described with reference to FIGS. 1 and 2.

(Carcass)

As shown in FIG. 1, the pneumatic tire 10 for a motorcycle according to the present embodiment includes a first carcass ply 12 and a second carcass ply 14 in which cords extending in a direction intersecting the tire equatorial plane CL are embedded. It has a carcass 16 constructed.

Note that the pneumatic tire 10 for a motorcycle according to the present embodiment is for a rear wheel, and the tire size is 190Z50ZR17.

[0039] Each end portion of the first carcass ply 12 and the second carcass ply 14 is wound around the bead core 20 embedded in the bead portion 18 with the tire inner force also being directed outward. Yes.

The first carcass ply 12 has a plurality of radially extending cords (nylons) arranged in parallel in the covered rubber, and in this embodiment, the cord for the tire equator surface at the tire equator position. The angle is set to 80 degrees. The second carcass ply 14 is also formed by embedding a plurality of cords (nylon) extending in the radial direction in parallel in the coated rubber, and in this embodiment, the cord angle with respect to the tire equatorial plane is also 80 degrees. Is set to Note that 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 angle of the cord is set to 80 degrees, but other angles such as 90 degrees may be used.

[0040] (Main crossing layer)

A main crossing layer 26 is disposed outside the carcass 16 in the tire radial direction. The main crossing layer 26 of the present embodiment is composed of a first belt ply 26A and a second belt ply 26B.

The first belt ply 26A is a cord in which a plurality of cords (corresponding to a diameter of 0.7 mm in which aromatic polyamide fibers are twisted in this embodiment) are arranged in parallel in a coated rubber and embedded at 50 spacing Z50mm. The angle of the cord with respect to the tire equator at the position of the tire equator is set to 33 degrees. The second belt ply 26B is also formed by arranging a plurality of cords (corresponding to a cord with a diameter of 0.7 mm in which aromatic polyamide fibers are twisted in this embodiment) in parallel in the covering rubber and placing them in parallel at a driving interval of 50 Z50 mm The cord angle with respect to the tire equatorial plane is set to 33 degrees.

The cords of the first belt ply 26A and the cords of the second belt ply 26B cross each other, and are inclined in opposite directions with respect to the tire equatorial plane CL.

[0041] A tread rubber 30 that forms a tread 28 is disposed on the outer side of the main crossing layer 26 in the tire radial direction.

In the present embodiment, the main crossing layer 26 may be composed of a belt ply having three or more forces composed of two belt plies. In this embodiment, the main crossing layer 26 is used to reinforce the crown portion of the carcass 16, but a spiral belt layer often used in the structure of a pneumatic tire for a high-performance motorcycle in recent years is used. OK.

[0042] The snail belt layer is, for example, a long rubber-coated cord in which one cord is covered with an unvulcanized coating rubber, or a belt-like ply in which a plurality of cords are covered with an unvulcanized coating rubber. Can be formed by spirally winding the cord, and the extending direction of the cord is substantially the tire circumferential direction. The cord of the spiral belt layer may be an organic fiber cord or a steel cord. [0043] More specifically, the spiral belt layer is a spiral belt in which cords of 0.7 mm diameter twisted with aromatic polyamide fibers are embedded in the coated rubber so that the driving distance is 50 and Z is 50 mm. It can be formed by winding.

[0044] Such a spiral belt layer may be arranged outside the main crossing layer 26 in the tire radial direction, or a spiral belt layer using a steel cord may be used instead of the main crossing layer 26. Also good.

[0045] (tread pattern)

As shown in FIG. 2, the tread 28 is formed with two circumferential main grooves 40 each having a groove width of 5 mm extending in the circumferential direction on both sides of the tire equatorial plane CL. Further, the tread 28 is formed with an inclined groove 50 from a position spaced outward in the tire width direction from the circumferential main groove 40 on the outer side in the tire width direction toward the tread end 28E.

[0046] The groove depths of the circumferential main groove 40 and the inclined groove 50 are all 6 mm in this embodiment.

The developed width of the tread 28 of this embodiment is 240 mm. The inclined groove 50 has a groove width of 4 mm, and the tread end 28E force is also formed within a range of 65 mm toward the tire equator side. The angle of the inclined groove 50 with respect to the tire circumferential direction is 50 degrees with respect to the tire equatorial plane CL.

In the tread side portion, the width of the elongated land portion 56 delimited by the groove is set to 10 mm in this embodiment. The width of the elongated land portion 56 and the groove width of the inclined groove 50 are measured at a position of 32.5 mm from the tread end 28E to the tire equatorial plane side.

The pattern negative rate is 28.6% on the tread side.

[0047] Note that the pneumatic tire for a motorcycle has a very round cross-sectional shape of the tread 28, and the pattern end is rounded. Therefore, when engraving the pattern depicted in Fig. 2, Like the paper affixed to the rope, the land and groove widths become narrower as they approach the pattern edge. Also in this embodiment, the actual width of the groove and the width of the land portion are processed so as to become narrower as they approach the end of the pattern. Therefore, in order to measure the average value on the side of the pattern, a groove is carved to the above-mentioned width at 32.5 mm from the end of the trade.

[0048] Here, assuming that the height of the elongated land portion 56 is h and the width of the elongated land portion 56 is t, tZh is 0.6 in an area of 70% or more of the extended length of the elongated land portion 56. It is necessary to satisfy ~ 2.0. In this embodiment, the average tZh of the elongated land portion 56 is 1.67. More specifically, Tretz The tZh of the elongated land part 56 measured at a position of 65 mm toward the tire equatorial plane is also 1.84, and the tread edge 28E force is also measured at a position of 32.5 mm toward the tire equatorial plane. Zh is 1.67, and tZh of the slender land 56 measured at the tread edge 28E is 1.50.

[0049] Since the tread 28 for a motorcycle is rounded, the diameter at the tire equatorial plane CL is maximum, and the diameter of the tread end 28E is smaller than the diameter of the tire equatorial plane CL. Since Fig. 2 is a developed view, the tread edge is drawn in the circumferential direction so as to be the same as the circumferential length of the tire equatorial plane.

[0050] (Action)

The operation of the pneumatic tire 10 for a motorcycle according to this embodiment will be described.

This pneumatic tire 10 for a motorcycle is used for the rear wheel of a motorcycle and exhibits its ability. In the pneumatic tire 10 for a motorcycle according to the present embodiment, the inclined groove 50 is inclined so that the tire equatorial plane side is closer to the tire rotation direction side (arrow A direction side) than the tread end side. When the driving force is applied simultaneously, the direction of the resultant force follows the inclination of the inclined groove (that is, the direction of the resultant force approaches the direction along the longitudinal direction of the elongated land portion 56). The deformation of the part 56 is effectively suppressed.

[0051] In addition, since the elongated land portion 56 that satisfies the ratio tZh between the height h and the width t of 0.6 to 2.0 is arranged on the tread side, the drainage performance of the portion that contacts the ground during turning And block rigidity can be achieved at high dimensions, and a higher gripping force can be obtained when turning on a wet road than before.

If the extended length of the elongated land portion 56 is less than 10% of the total tread width in the tread deployment width direction, the proportion of the elongated land portion 56 in the pattern becomes a force and depends on the other components of the pattern. The wet turning performance is affected, and the grip force when turning on a wet road surface cannot be obtained sufficiently.

[0052] [Other Embodiments]

In the above embodiment, the inclination angle of the inclined groove 50 is constant, but the inclination angle may be different depending on the part. For example, when a motorcycle is cornering deeply, tilt the vehicle body while turning and use the vicinity of the tread edge of the tire, but since the lateral force acts on the tire more than the longitudinal force, Elongated land near the tread edge 56 Is extending in the direction along the direction of lateral force input, that is, the angle of the center line in the width direction of the elongated land portion 56 with respect to the tire circumferential direction is preferably set within a range of 50 to 90 degrees. Yes.

[0053] On the other hand, considering the state force when the vehicle body is greatly inclined, the place where the tire touches the ground moves from the tread edge side to the tire equator side with acceleration, With acceleration, the ratio of lateral force decreases and the ratio of acceleration force increases, so the resultant force also approaches the tire circumferential direction from the lateral direction. Therefore, on the tire equatorial plane side, the angle of the widthwise center line of the elongated land portion 56 with respect to the tire circumferential direction is preferably within a range of 10 to 30 degrees.

[0054] Although the rear wheel has been described in the above embodiment, the present invention can also be applied to a pneumatic tire for a motorcycle for a front wheel.

As the pneumatic tire for a motorcycle used for the front wheel, for example, a pattern in which the rotation direction of the tire having the tread pattern shown in each of FIGS. 1 to 4 is reversed from that shown in the figure can be used. That is, when used for the front wheel, the inclined groove 50 is inclined so that the shoulder side is positioned in the tire rotation direction more than the tire equatorial plane side.

As a result, when lateral force and braking force are applied simultaneously, the direction of the resultant force follows the inclination of the inclined groove 50, and deformation of the elongated land portion 56 can be effectively suppressed.

[0055] (Rear tire test)

In order to confirm the performance improvement effect of the present invention, the result of a comparison test on the maneuverability on a wet road surface using an actual vehicle will be described below. Rear test tires were prepared, and only the rear tires were replaced for actual vehicle tests. The front tire was always fixed with a conventional one.

[0056] In the test, the test tire was mounted on the rear wheel of a sport type motorcycle of lOOOOcc, and the vehicle was run quite intense (close to the limit) on a test course on a rainy day. The rainfall was stable all day and was always in a uniform wet state. For one tire, the test course was run 4 laps, and the average lap time for 4 laps was calculated. Since the center part of these tires had the same pattern, the difference was the cornering performance. It was. We also comprehensively evaluated the steering stability performance in the wet state due to the feeling of the test rider at the same time using the 10-point method. In addition, the test rider's evaluation comments are added and the results are shown. First, the test tire will be described.

(Tire of Example 1)

3 is a tire according to the above-described embodiment having the pattern of FIG.

[0058] (Tire of Example 2)

It has the pattern of Fig. 3. Except for the width of the elongated land portion 56 on the shoulder side and the width of the inclined groove 50, all are the same as in Example 1. The negative rate is also matched. The width t of the elongated land portion 56 is 7. Omm, and the width of the inclined groove 50 is 2.8 mm.

The average value of tZh is 1.17. More specifically, the tread end 28E force was also measured at a position where the tZh of the elongated land portion 56 measured at 65 mm toward the tire equatorial plane was 1.29, and the tZh 28E from the tread end 28E toward the tire equatorial plane 32.5 mm. The tZh of the elongated land portion 56 is 1.17, and the tZh of the elongated land portion 56 measured at the tread edge 28E is 1.05.

[0059] (Tire of Example 3)

It has the pattern of Fig. 4. Except for the width of the elongated land portion 56 on the shoulder side and the width of the inclined groove 50, all are the same as in Example 1. The negative rate is also matched. The width t of the elongated land portion 56 is 5. Omm, and the width of the inclined groove 50 is 2. Omm.

The average value of tZh is 0.83. More specifically, the tread end 28E force was also measured at a position of 65 mm toward the equatorial plane of the tire, and the tZh of the elongated land portion 56 was 0.91, and the tread end 28E was measured at a position of 32.5 mm toward the tire equatorial plane. The tZh of the elongated land portion 56 is 0.83, and the tZh of the elongated land portion 56 measured at the position of the tread edge 28E is 0.75.

[0060] (Tire of Example 4)

It has the pattern of FIG. The center part is the same as in Example 1. Long inclined grooves 50A extending from the tread end 28A to the vicinity of the center and short inclined grooves 50B extending similarly from the tread end 28A are alternately formed. The angle of each inclined groove is 15 degrees with respect to the tire circumferential direction on the center side, and 70 degrees with respect to the tire circumferential direction on the tread end side. The negative rate is the same as in Example 1.

In addition, at the position where the tread end force is 32.5 mm toward the tire equatorial plane, each inclined groove has a groove width of 4 mm and an angle with respect to the tire circumferential direction of 40 degrees, which is the same as in Example 1. In addition, the elongated land portion 56 is also located 32.5 mm from the tread edge 28E to the tire equator side. The width is 10 mm, which is the same as in Example 1.

The average value of tZh is 1.67. More specifically, the tZh of the elongated land portion 56 measured at a position of 65 mm toward the tire equator side at the tread edge 28E force is 1.84, and the tZh is measured at a position of 32.5 mm from the tread edge 28E toward the tire equator side. The tZh of the elongated land portion 56 is 1.67, and the tZh of the elongated land portion 56 measured at the position of the tread edge 28E is 1.50.

[0061] (Tire of Comparative Example 1)

It has the pattern shown in FIG. The force is the same pattern as in Example 1. The width of the slender land portion 56 on the shoulder side is 16 mm, and the width of the inclined groove 50 is 6.4 mm.

The average value of tZh is 2.67. More specifically, the tread end 28E force was measured at a position of 65 mm toward the tire equatorial plane at a tZh of 2.94 and the tZh at the tread end 28E from the tire equatorial plane side was measured at a position of 32.5 mm. The tZh of the elongated land portion 56 is 2.67, and the tZh of the elongated land portion 56 measured at the position of the tread edge 28E is 2.40! /.

[0062] (Tire of Comparative Example 2)

The width of the elongated land on the shoulder side is 3mm and the width of the inclined groove is 1.2mm, which is the same pattern as in Example 1.

The average value of tZh is 0.5. More specifically, the tread end 28E force was also measured at a position of 65 mm toward the equatorial plane of the tire, and the tZh of the elongated land portion 56 was 0.45, and the elongate measured at a position of 32.5 mm from the tread end 28E to the tire equatorial plane. The tZh of land part 56 is 0.50, and the tZh force of elongated land part 56 measured at the position of tread edge 28E is .55.

[0063] (Tire of Comparative Example 3)

A pattern obtained by reversing the pattern of Example 1.

[0064] The test results are shown below.

(Example 1)

t / h: l. 67

Lap time: 52 seconds 4

Wet driving score: 7 points

Rider's comment: It is very stable at the corner where it is greatly defeated. I felt a firm grip when opening the accelerator and accelerating from a state where it was greatly defeated. [Example 2]

t / h: l. 17

Lap time: 51 seconds 9

Wet driving score: 8 points

Rider's comment: Basically, it feels the same as the pattern in Example 4, but the grip force when accelerating by opening the accelerator is better than Example 1 even when the state force is greatly lowered.

[0066] (Example 3)

t / h: 0.83

Lap time: 51 seconds 4

Wet driving score: 9 points

Rider's comment: Basically, it feels the same as in Example 1, but the overall grip is higher than in Example 1. In particular, even when the state force is greatly defeated, the grip when opening the accelerator and accelerating is very good.

[0067] (Example 4)

t / h: l. 67

Lap time: 51 seconds 8

Wet driving score: 9 points

Rider's comment: The grip is very high. In addition, the motion when accelerating by opening the state force accelerator greatly depressed feels smooth. In other words, there is a sense of security that the grip is always generated stably.

[0068] (Comparative Example 1)

t / h: 2. 67

Lap time: 54 seconds 7

Wet driving score: 4 points

Rider comment: There are few grips. Even when the state force is greatly defeated, the tires are likely to slip when the accelerator is opened and accelerated. The vehicle is likely to become unstable.

[0069] (Comparative Example 2) t / h: 0.5

Lap time: 55 seconds 5

Wet driving score: 2 points

Rider's comment: Because of the tiredness, you can't defeat the car body. Make sure you lose time in the corners. Even if you try to knock it down, you can't beat it because there is no grip.

[0070] (Comparative Example 3)

t / h: l. 67

Lap time: 53 seconds 6

Wet driving score: 6 points

Rider's comment: A greatly defeated state force When opening the accelerator and accelerating, it behaves like a slip. Force that feels a little stable during braking The tire slides greatly during acceleration.

[0071] Verification of effect.

The tires according to the present inventions of Examples 1 to 4 clearly had higher wet handling stability than the comparative examples. Most of the conventional average patterns, as in Comparative Example 1, have a tZh greater than 2.5! /, So it was confirmed that the tire according to the present invention functioned well.

[0072] From a comparison between Examples 1 to 3 and Comparative Examples 1 and 2, it can be seen that there is an appropriate value for tZh. In the actual vehicle test, Example 3 was the most appropriate tZh. This can be explained by the falling or rising of the block, as shown in the previous experiment.

In other words, if tZh is too large, the block will be tilted only a little, and the floating area will increase, making it difficult for traction to occur. On the other hand, as shown in Comparative Example 2, in the case of very finely engraved blocks, the block itself collapses easily, and the contact area is reduced because it tries to catch the road surface only with the corners of the blocks. It seems to have been very small.

[0073] From the comparison between Example 1 and Example 4, it can be seen that gradually increasing the groove angle leads to an improvement in wet performance. This is because of the characteristic of the posture change when turning the motorcycle, and when it is greatly tilted, the traction in the front-rear direction acts in the acceleration state in which the vehicle body that has a good direction close to the lateral groove that generates lateral force is raised to some extent. Therefore, the equator groove is suitable. It shows that you are doing.

From the comparison between Example 1 and Comparative Example 3, the pattern directionality is known. In the case of the rear wheel, the traction is an important performance, and the traction in the direction as in Example 1 is easier to force. On the other hand, Comparative Example 3 seems to have lost some gripping force because the direction of the force does not match the direction of the elongated land during the force trough.

[0075] The tires of the examples having the present invention were confirmed to have significantly improved wet handling stability as compared with the tires of the comparative examples.

Claims

The scope of the claims

[1] A pneumatic tire for a motorcycle having a plurality of land portions divided by a plurality of grooves in a tread, and including a slender land portion whose length is three times or more of the width within the plurality of land portions. There,

Centering on the tire equatorial plane, when 60% of the tread width is the center of the tread and the outer side in the tire width direction of the center of the tread is the tread side, at least a part of the elongated land is on the tread side. Placed in the

When the height of the elongated land part is h and the width of the elongated land part is t, tZh should satisfy 0.6 to 2.0 in the region of 70% or more of the extended length of the elongated land part. A characteristic pneumatic tire for motorcycles.

[2] The two-wheeled vehicle according to claim 1, wherein the elongated land portions are formed between grooves arranged at intervals in the tire circumferential direction and having an angle with respect to the tire circumferential direction. Pneumatic tire.

[3] The pneumatic tire for a motorcycle according to claim 2, wherein the elongate land portion extends continuously in the tread deployment width direction over 10% of the entire width of the tread.

4. The pneumatic tire for a motorcycle according to claim 3, wherein the elongated land portion is inclined so that the shoulder side is positioned in the tire rotation direction with respect to the tire equatorial plane side.

5. The pneumatic tire for a motorcycle according to claim 3, wherein the elongated land portion is inclined such that a tire equatorial plane side is positioned in a tire rotating direction with respect to a shoulder side.

[6] The angle of the center line in the width direction of the elongated land with respect to the tire circumferential direction is set large from the tire equator side to the shoulder side, within a range of 10 to 30 degrees on the tire equator side, and on the shoulder side The pneumatic tire for a motorcycle according to claim 4 or claim 5, wherein the pneumatic tire is set within a range of 50 to 90 degrees.