JP6503257B2 - Motorcycle tire - Google Patents

Description

  The present invention relates to a tire for a motorcycle (hereinafter, also simply referred to as a "tire"), and more specifically, a pneumatic radial for a motorcycle having an improved relationship between a contact shape of the tire and an inclined groove provided on a tread surface. It relates to the tire.

  Unlike the four-wheeled vehicle such as a passenger car or a truck or bus, the tire for a motorcycle has a smaller radius of curvature than that of a four-wheeled tire because of the characteristics of a two-wheeled vehicle that tilts and turns the vehicle. The cross section has a round tire shape. That is, in a motorcycle tire, it is common that the tread central portion is mainly in contact with the vehicle when the vehicle is traveling straight and the tread shoulder is in contact with the vehicle during cornering.

  As a technique for defining the curvature of the tread surface of a motorcycle, for example, Patent Document 1 discloses a tread whose outer surface is a tread surface, and a substantially inward radial extension from an end of the tread, and an outer surface is a sidewall surface It is disclosed that the tread surface has a convex shape having a radius of curvature of 190 mm or more and 210 mm or less in a cross section perpendicular to the circumferential direction of the tire.

JP, 2008-273422, A

  Heretofore, in such a tire for a motorcycle, as a method for reducing noise, a method of reducing a groove in a contact area or reducing a groove depth is mainly used. However, depending on the pattern formed on the tread surface, there is a problem of noise caused by the pattern, and this problem can be solved without losing other performance such as tire durability to realize a tire with reduced noise. It was being asked.

  Therefore, an object of the present invention is to provide a motorcycle tire in which noise caused by a pattern is reduced without deteriorating other performance such as tire durability.

  As a result of intensive investigations, the inventor of the present invention has found that the above-mentioned problems can be solved by defining the relationship between the contact shape of the tire and the inclined groove provided on the tread surface in a predetermined manner, thus completing the present invention. It came to

That is, according to the present invention, there is provided a tire for a motorcycle having a tread portion, side wall portions and bead portions continuous with both sides of the tread portion, and in which a rotational direction at the time of wearing the vehicle is specified.
Of the tread portion, the radius of curvature Rc of the tread surface at the center portion centered on the tire equator line is 150 to 250 mm, and the radius of curvature Rs of the tread surface at the shoulder portion located outside the center portion is 80 to 100 mm And
The tread surface has an inclined main groove in which a first groove portion and a second groove portion are connected via a bending point, and the first groove portion is disposed in a ground contact area when traveling straight, The groove portion 2 is disposed straddling the ground contact area when going straight and the outer ground area located outside the ground contact area when going straight,
The inclination angle θ1 of the first groove with respect to the tire circumferential direction is 0 to 23 °, and the inclination angle θ2 of the second groove with respect to the tire circumferential direction is 50 to 70 °.
The inflection point between the first groove portion and the second groove portion is on the outer side in the tire width direction than a position at which 17% of the half width of the tread periphery length is separated from the tire equator line Exist and
The ratio Rc / Rs of the radius of curvature Rc of the tread surface at the center portion to the radius of curvature Rs of the tread surface at the shoulder portion is expressed by the following formula (1):
1.7 ≦ Rc / Rs ≦ 3.1 (1)
It is characterized by satisfying the relationship represented by

  In the tire according to the present invention, preferably, the length L1 of the first groove portion is 34 to 82% of the half width of the tread periphery length. In the tire according to the present invention, preferably, an intersecting belt layer composed of two or more inclined belts arranged so that cord directions cross each other between layers is provided on the inner side in the tire radial direction of the tread surface.

  Here, the tread periphery length refers to one tread end TE to the other tread end in the tire width direction in a cross section in the tire width direction under no load condition where the tire is assembled to the application rim and filled with a prescribed internal pressure. The length measured along the tread surface up to TE. The angle of the cords constituting the carcass ply, the belt layer and the like with respect to the circumferential direction of the tire is also measured under an unloaded condition in which the tire is assembled to the application rim and the prescribed internal pressure is filled.

  In addition, “application rim” refers to a standard rim specified in the following standard according to the tire size, or Design Rim or Measuring Rim, and “specified internal pressure” refers to the maximum load capacity in the following standard. The correspondingly defined air pressure is referred to as "maximum load capacity", which refers to the maximum load that is allowed to be applied to the tire according to the following specifications. And, the standard is determined by the industry standard effective for the area where the tire is produced or used, for example, in the US, it is YEAR BOOK of TRA (THE TIRE and RIM ASSOCIATION INC.), And Europe Then, it is STANDARDS MANUAL of ETRTO (The European Tire and Rim Technical Organization), and in Japan, it is YEAR BOOK of JATMA (Japan Automobile Tire Association).

  According to the present invention, it has become possible to realize a motorcycle tire in which noise caused by a pattern is reduced without impairing other performance such as tire durability.

FIG. 1 is a partial development view showing a tread surface of an example of a motorcycle tire of the present invention. FIG. 1 is a widthwise sectional view showing an example of a motorcycle tire according to the present invention.

Hereinafter, a tire for a motorcycle according to the present invention will be described in detail with reference to the drawings.
The tire for a motorcycle according to the present invention is a tire for a motorcycle, which has a tread portion, side wall portions and bead portions continuous with both sides of the tread portion, and in which a rotational direction at the time of wearing the vehicle is specified. In this case, the largest effect is obtained. FIG. 1 is a partial development view showing a tread surface of an example of a tire for a motorcycle according to the present invention, and the arrow in the figure shows the rotation direction of the tire. FIG. 2 is a widthwise sectional view showing an example of a motorcycle tire according to the present invention.

  The illustrated tire 100 for a motorcycle according to the present invention has a tread portion 101, a pair of sidewall portions 102 continuous with both sides of the tread portion 101, and a pair of bead portions 103 continuous with the pair of sidewall portions 102, respectively. doing. In the tire according to the present invention, the radius of curvature Rc of the tread surface at the center portion CE centering on the tire equator line CL in the tread portion 101 is 150 to 250 mm, preferably 160 to 200 mm, and the outside of the center portion CE The radius of curvature Rs of the tread surface at the shoulder portion SH located at is 80 to 100 mm, preferably 85 to 95 mm. By forming the tread surface with such a radius of curvature, the contact area at the time of straight running increases, so that the temperature rise of the entire contact surface can be suppressed and the bending in the tire radial direction near the contact end becomes small. The temperature rise inside the ground end can be suppressed, and the durability can be improved. If the curvature radius Rc of the tread surface at the center portion CE is less than 150 mm, pattern noise and durability deteriorate due to the change in the contact shape, and if it exceeds 250 mm, steering stability is increased. It gets worse. If the radius of curvature Rs of the tread surface at the shoulder portion SH is less than 80 mm, the roll characteristics at the time of turning tend to fall, and if it exceeds 100 mm, the roll characteristics at the time of turning become too heavy.

  Here, in the present invention, the boundary point between the center portion CE and the shoulder portion SH, that is, the position of the contact point between tread surfaces having different curvature radii is 20% of the half width TW / 2 of the tread periphery length from the tire equator line CL. Shall be in the range of ̃60%.

  Further, the tire according to the present invention has the inclined main groove 10 in which the first groove portion 11 and the second groove portion 12 are connected via the bending point X on the tread surface. Among them, the first groove portion 11 is disposed in the ground contact area Q1 when traveling straight, and the second groove portion 12 is arranged straddling the ground contact area Q1 when traveling straight and the outer ground area Q2 located outside thereof. That is, a bending point X connecting the first groove portion 11 and the second groove portion 12 exists in the straight contact area Q1. In the present invention, while the groove length L1 of the first groove portion 11 is shortened and the inclination angle θ1 of the first groove portion 11 with respect to the tire circumferential direction is reduced, the groove is provided in the center portion to ensure drainage. In order to do this, it is necessary for the bending point X to be present in the contact area Q1 when traveling straight. If the groove length L1 of the first groove portion 11 is too long or the inclination angle θ1 of the first groove portion 11 is too large, the pattern noise will be deteriorated.

  Here, in the present invention, the straight contact area Q1 means that the radius of curvature Rc of the tread surface at the center portion and the radius of curvature Rs of the tread surface at the shoulder portion take specific values within the scope of the present invention. It refers to the area where the tire comes into contact with the vehicle during straight running under an unloaded condition where the tire is assembled to the application rim and filled with a prescribed internal pressure. The straight contact area Q1 can be in the range of 10% to 50% of the half width TW / 2 of the tread periphery length on both sides in the tire width direction from the tire equator line CL. In the illustrated example, the straight contact area Q1 exists in the center portion CE.

  Furthermore, in the tire of the present invention, the inclination angle θ1 of the first groove portion 11 with respect to the tire circumferential direction is 0 to 23 °, preferably 10 to 20 °, and the inclination of the second groove portion 12 with respect to the tire circumferential direction. It is necessary that the angle θ2 be 50 to 70 °, preferably 55 to 65 °. When the inclination angle θ1 of the first groove portion 11 exceeds 23 °, the pattern noise is deteriorated, and when it is less than 0 °, the groove is not formed in the center portion, and the wet grip performance is deteriorated. If the inclination angle θ2 of the second groove 12 is less than 50 °, the pattern noise will deteriorate, and if it exceeds 70 °, the groove will be too close to the tire width direction and the uneven wear performance will deteriorate. . That is, pattern noise, which is noise due to the pattern of grooves formed on the tread surface, tends to deteriorate as the overlap between the contour of the ground contact surface and the inclined groove increases, so it is present in the straight contact area Q1. In the first groove portion 11, the smaller the inclination angle θ1 with respect to the tire circumferential direction, the less the overlap with the outer shape of the ground contact surface, so that the pattern noise reduction effect can be obtained. On the other hand, pattern noise is reduced in the second groove 12, which exists from the ground contact area Q1 to the outer ground contact area Q2 when going straight, because the larger the inclination angle θ2 with respect to the tire circumferential direction, the more difficult it is to overlap with the outer surface of the ground surface. You can get the effect. Here, the inclination angle with respect to the tire circumferential direction of each groove means an angle on the acute angle side among straight lines connecting the tire width direction inner points of the groove ends of the groove with respect to the tire circumferential direction.

  Furthermore, in the tire according to the present invention, the bending point X between the first groove and the second groove is 17% of the half width TW / 2 of the tread periphery length from the tire equator line CL. It exists in the tire width direction outer side, and is in contact area Q1 at the time of going straight. Preferably, the inflection point X of the inclined main groove 10 is on the outer side in the tire width direction than a position at which 20% of the half width TW / 2 of the tread periphery length is separated from the tire equator line CL Shall exist in If the bending point X of the inclined main groove 10 exists at a position separated by 17% of the half width TW / 2 of the tread periphery length from the tire equator line CL or at the inner side in the tire width direction, pattern noise deteriorates and straight running If it exists outside the ground contact area Q1, that is, in the outer ground contact area Q2, the groove is not present at the center portion, and the wet grip performance is deteriorated. Here, the inflection point X means an intersection point of a ridge line of the tire width direction inner groove wall 11i of the first groove portion 11 and a ridge line of the tire width direction inner groove wall 12i of the second groove portion 12.

Furthermore, in the tire of the present invention, the ratio Rc / Rs of the curvature radius Rc (mm) of the tread surface at the center portion CE and the curvature radius Rs (mm) of the tread surface at the shoulder portion SH is expressed by the following equation (1) ),
1.7 ≦ Rc / Rs ≦ 3.1 (1)
It is also necessary to satisfy the relationship represented by The ratio Rc / Rs preferably satisfies the relationship represented by 1.75 ≦ Rc / Rs ≦ 2.35. If the ratio Rc / Rs is smaller than 1.7, the tread height Ht becomes too small, the contact area at the time of turning decreases, and the grip performance at the time of turning decreases. On the other hand, if the ratio Rc / Rs is larger than 3.1, the ratio of the radius of curvature Rc of the center portion CE to the radius of curvature Rs of the shoulder portion SH becomes too large, and the reaction force when the vehicle is inclined is The roll characteristic on steering stability, which is a characteristic, does not change linearly. Here, the tread height Ht refers to the tire radial direction from the outer surface of the tread portion 101 to the tread end TE in the cross section in the tire width direction under an unloaded condition where the tire is assembled to the application rim and filled with a prescribed internal pressure. Means distance.

  As described above, in the tire according to the present invention, the radius of curvature of the tread surface is large at the center portion and small at the shoulder portion, and by providing a predetermined inclined main groove at the center portion, durability and steering stability are obtained. It has become possible to reduce pattern noise without deteriorating various performances such as drainage.

  In the present invention, the length L1 of the first groove portion 11 is preferably 34 to 82% of the half width of the tread periphery length, and more preferably 40 to 60%. If the length L1 of the first groove portion 11 is less than 34% of the half width of the tread periphery length, the groove does not exist in the center portion, and the wet grip performance tends to be deteriorated. On the other hand, when the length L1 of the first groove portion 11 exceeds 82% of the half width of the tread periphery length, pattern noise tends to be deteriorated. Here, the length L1 of the first groove portion 11 was measured along the extending direction of the first groove portion 11 between the tire circumferential direction both end portions of the tire width direction inner groove wall 11i of the first groove portion 11 Means distance. In the first groove portion 11 present in the ground contact area Q1 when going straight, since it is difficult for the length L1 to overlap with the outer shape of the ground plane, it is preferable to be able to obtain an effect of reducing pattern noise.

  Furthermore, in the present invention, the groove width of the first groove portion 11 and the second groove portion 12 is preferably 2 to 12% of the half width of the tread periphery length, and more preferably 2.5 to 8%. preferable. When the groove width of the first groove portion 11 and the second groove portion 12 is less than 2% of the half width of the tread periphery length, the wet grip performance is deteriorated. On the other hand, if the groove width of the first groove portion 11 and the second groove portion 12 exceeds 12% of the half width of the tread periphery length, the negative ratio becomes too high and the tread shear rigidity is excessively lowered, and the steering stability is deteriorated. Do. Here, the groove widths of the first groove portion 11 and the second groove portion 12 mean the distance between the groove walls measured in the direction perpendicular to the extending direction of each groove. The groove depth of each inclined main groove can be, for example, 5 to 8.5 mm.

  In the tire according to the present invention shown in the drawings, the inclined main groove 10 is a first groove portion 11 present in the contact area Q1 when traveling straight and a second groove 11 extending over the contact area Q1 when traveling straight and the outer contact area Q2. In addition to the groove portion 12, a third groove portion 13 present in the outer ground contact area Q2 is provided. The third groove 13 is connected to the second groove 12 via a bending point Y, that is, the second groove 12 has a first point via a bending point X and a bending point Y at both ends thereof. It is connected to the groove 11 and the third groove 13. Here, the inflection point Y means an intersection point of a ridge line of the tire width direction inner groove wall 12i of the second groove 12 and a ridge line of the tire width direction outer groove wall 13o of the third groove 13. When the inclined main groove 10 is made up of the first groove portion 11, the second groove portion 12 and the third groove portion 13, the effect of improving the wet grip by the improvement of the drainage property can be obtained. The illustrated inclined main groove 10 is generally inclined rearward from the front in the tire rotational direction to the outer side in the tire width direction, and does not cross the tire equator line CL and does not reach the tread end TE. It ends in the tread surface at both ends of the direction. More specifically, the first groove 11 and the second groove 12 are inclined rearward from the front in the tire rotation direction toward the rear in the tire width direction, and the third groove 13 is from the front in the tire rotation direction to the rear. Toward the inside of the tire width direction.

  Further, a substantially C-shaped or substantially inverted C-shaped auxiliary groove 20 is disposed in the outer contact area Q2 of the tread surface of the tire according to the present invention shown. The sub-grooves 20 shown are located outside the first groove portion 11 and the second groove portion 12 of the inclined main groove 10 in the tire width direction, and both ends of the groove do not open to the tread end TE. It ends in the tread surface. By providing such a sub groove 20, it is possible to obtain the effect of improving the durability by improving the heat radiation effect. The groove width of the sub groove 20 can be, for example, 4 to 8 mm, and the groove depth can be, for example, 4 to 6 mm.

  The tire 100 of the present invention shown in the drawing has a carcass 104 of at least one, particularly two or more, in the illustrated example, two carcass plies extending between a pair of bead portions 103 as a skeleton. In the illustrated example, the end of the carcass 104 is folded back and locked to the bead core 105 from the inside of the tire to the outside, but may be sandwiched by bead wires from both sides and locked, and there is no particular limitation. The angle of the ply cord of the carcass 104 can be, for example, 65 ° to 80 ° in either the left or right direction with respect to the tire circumferential direction. Here, the angle of the ply cord refers to the acute angle side of the angles formed by the extending direction of the reinforcing cords constituting the carcass ply with respect to the tire circumferential direction.

  Further, in the illustrated tire 100, at least one sheet is disposed so that at least one sheet intersects between the layers in the tire radial direction inner side of the tread surface and at the tire tire radial direction outer side of the carcass 104; For example, an intersecting belt layer 106 composed of two or three, in the illustrated example, three inclined belts, is provided. Here, the two or three inclined belts are sequentially referred to as a first inclined belt 106a, a second inclined belt 106b, and a third inclined belt 106c from the inner side in the tire radial direction. In the present invention, of the two or three inclined belts, the ratio BW2 between the width BW2 along the tread surface of the second inclined belt 106b located second from the inner side in the tire radial direction and the tread periphery length TPW It is preferable that / TPW is in the range of 40% to 80%.

  When considering an intersecting layer composed of two or more inclined belts as a curved surface having a double curvature and a thickness, this intersecting layer becomes flat when a load is applied to the tire. In the process of deformation such that the belt having a curvature becomes flat, the end portion of the belt is deformed so as to extend in the circumferential direction of the tire, and the elongation in the circumferential direction of the tire generates shear strain between the belt layers, It is thought to cause BES. Therefore, it is advantageous for improving the BES resistance that the tire circumferential direction elongation at the belt end is small. In addition, in the case of a tread having a round cross section with a small radius of curvature, such as a tire for a motorcycle, the smaller the width of the belt disposed inside, the smaller the difference in diameter between the belt center portion and the belt end portion. The tire circumferential direction elongation of the belt end decreases. Therefore, in the present invention, the width BW2 of the second inclined belt 106b is set to a narrow range such that the ratio BW2 / TPW is 40% to 80% in relation to the tread periphery length TPW. The tire circumferential direction elongation of the belt end at the time of deformation can be reduced to improve the BES resistance, and from this point as well, the durability can be improved. In the present invention, in particular, the belt durability is synergistically improved by increasing the curvature radius Rc of the tread surface at the center portion CE as described above and defining the width BW2 of the second inclined belt 106b. It is possible to

  If the width BW2 of the second inclined belt 106b is less than 40% in the ratio BW2 / TPW, that is, if the width is too narrow, the lateral force at the time of turning decreases, and the steering stability at the time of turning deteriorates. If the ratio BW2 / TPW exceeds 80%, that is, if the width is too wide, the effect of improving BES resistance can not be sufficiently obtained, and desired durability may not be obtained. The width BW2 of the second inclined belt 106b is preferably in the range of 40% to 80%, more preferably in the range of 50% to 70%, and still more preferably in the range of 55% to 65% in the ratio BW2 / TPW. .

  When the width of the inclined belt is narrowed, the generation width of tension by the belt is narrowed, so the elongation of the belt at the time of filling the tire with internal pressure becomes large, and the interlaminar shear strain of the belt by the internal pressure filling becomes large, Unlike tires for trucks and buses used with high internal pressure, the tire for motorcycles has a low internal pressure of about 280 kPa, so it can be estimated that the influence of interlayer shear strain due to internal pressure filling on durability is small.

  Therefore, in the present invention, the range of the radius of curvature Rc of the center portion and the radius of curvature Rs of the shoulder portion, and the range of the ratio BW2 / TPW of the second inclined belt BW2 to the tread periphery length TPW are prescribed. As a result, it is possible to obtain a motorcycle tire having improved tire durability by improving BES resistance while securing steering stability at the time of turning.

  Here, in the present invention, when there are three inclined belts, the widths of the three inclined belts are preferably set so as to satisfy the relationship shown by WB3> WB1> WB2. That is, it is preferable that the width WB3 of the third inclined belt 106c is the widest, and the width WB2 of the second inclined belt 106b is the narrowest. Thereby, the effect of suppressing the interlayer shear strain of the first inclined belt 106a and the second inclined belt 106b by the third inclined belt 106c can be obtained.

  Furthermore, in the tire 100 of the present invention, the cord angle of the inclined belt constituting the crossing belt layer 106 is, for example, 15 ° or more and 26 ° or less, particularly 15 ° or more and 20 ° or less with respect to the tire circumferential direction. Is preferred. The high speed durability can be improved by setting the cord angle of the inclined belt in the above range. Here, the cord angle refers to the acute angle side of the angles formed by the extending direction of the reinforcing cords constituting the inclined belt with respect to the tire circumferential direction.

  In the present invention, the belt cord of the crossing belt layer 106 is not particularly limited, and known cords can be used. For example, aromatic polyamide (aramid, for example, DuPont brand name: Kevlar) or polyethylene naphthalate (polyamide naphthalate) Organic fibers such as PEN), polyethylene terephthalate (PET), rayon, aliphatic polyamide (nylon) and the like, and materials made of materials such as glass fibers and carbon fibers can be appropriately selected and used. Preferably, the first inclined belt 106a and the second inclined belt 106b positioned from the inner side in the tire radial direction to the first and second sheets are made of aromatic polyamide, and the third inclined belt is positioned from the inner side in the tire radial direction. The third inclined belt 106c with the inclined belt 106c is made of aliphatic polyamide. Thereby, appropriate tire rigidity can be secured, which is preferable.

  The present invention is useful as a rear tire for a motorcycle, and can be applied to any tire of radial structure and bias structure. Examples of the tire size to which the present invention is applied include 200 / 55R16M / C, 240 / 55R16M / C, and the like.

Hereinafter, the present invention will be described in more detail using examples.
Example 1
A tire for a motorcycle having a tread pattern as shown in FIG. 1 and a cross-sectional structure as shown in FIG. 2 was produced with a tire size of 200 / 55R16M / C. This tire has a carcass consisting of two nylon carcass plies (cord angle: + 75 ° and -75 ° with respect to the circumferential direction of the tire) as a skeleton, and from the inner layer side to the crown portion in the radial direction outer side thereof. Two aramid inclined belts (cord angle: + 15 ° and -15 ° to the tire circumferential direction) and one nylon inclined belt (cord angle: + 15 ° to the tire circumferential direction) are provided The

  Of the tread portion of the tire, the radius of curvature Rc of the tread surface at the center portion is 160 mm, the radius of curvature Rs of the tread surface at the shoulder portion is 90 mm, and the ratio Rc / Rs thereof is 1.8. Moreover, the tread periphery length TW of this tire is 231.6 mm, and the boundary point between the center portion and the shoulder portion exists at 43.8% of the half width TW / 2 of the tread periphery length from the tire equator line CL. It was

  The tread main surface of this tire is provided with an inclined main groove in which a first groove, a second groove and a third groove are connected via a bending point, and of these, the first groove is straight when going straight The second groove portion is disposed in the ground contact region, the second groove portion is disposed straddling the ground contact region and the outer ground contact region during straight movement, and the third groove portion is disposed in the outer ground contact region. Further, the straight contact area Q1 is in the range of 34.9% of the half width TW / 2 of the tread periphery length on both sides in the tire width direction from the tire equator line CL.

  In this tire, the inclination angle θ1 of the first groove with respect to the tire circumferential direction is 15 °, and the inclination angle θ2 of the second groove with respect to the tire circumferential direction is 58 °, and the distance between the first groove and the second groove is Inflection point X was located at a distance of 29% of the half width of the tread periphery length from the tire equator line. Further, the length L1 of the first groove was 48% of the half width of the tread periphery length, and the groove depth of the first groove and the second groove was 8 mm.

Examples 2 to 16
Tires of Examples 2 to 16 were produced in the same manner as Example 1 except that each parameter was changed as shown in the following table.

Conventional Example 1
A tire of Conventional Example 1 was produced in the same manner as in Example 1 except that each parameter was changed as shown in the following table at a tire size of 200/55 R16 M / C.

<Durability>
Drum running test where each obtained test tire is assembled on a rim of rim size MT 6.00-16 M / C, filled with internal pressure 280 kPa, and the load is increased stepwise from a load of 4.04 kN at a speed of 81 km / h The durability was evaluated by the distance traveled until the crack occurred. The durability is indicated by an index based on Conventional Example 1 being 100, and the larger the numerical value, the longer the travel distance and the better the durability.

<Evaluation of noise level>
Each of the obtained test tires is assembled on a rim of rim size MT 6.00-16 M / C, filled with an internal pressure of 280 kPa, and traveled at a speed of 60 km / h with a load of 2.58 kN loaded. The noise level (dB) was calculated.
These results are shown together in the following table.

＊１）傾斜主溝の屈曲点Ｘが、タイヤ赤道線からトレッドペリフェリー長の半幅の何％を隔てた位置に存在するかを示す。
＊２）第１の溝部の長さＬ１が、トレッドペリフェリー長の半幅ＴＷ／２の何％であるかを示す。

* 1) It shows that the bending point X of the inclined main groove is located at a position of a half width of the tread periphery length apart from the tire equator line.
* 2) It shows what% of the half width TW / 2 of the tread periphery length is the first groove length L1.

  From the results shown in the above table, it was confirmed that in the tire of the present invention, the noise caused by the pattern is reduced without deteriorating the tire durability.

DESCRIPTION OF REFERENCE NUMERALS 10 inclined main groove 11 first groove portion 12 second groove portion 13 third groove portion 20 sub groove 100 tire 101 tread portion 102 sidewall portion 103 bead portion 104 carcass 105 bead core 106 intersecting belt layer 106 a first inclined belt 106 b second Inclined belt 106c Third inclined belt CE Center part SH Shoulder part TE Tread end Q1 Straight contact area Q2 outer contact area X, Y Inflection point

Claims (3)

A tire for a motorcycle comprising a tread portion, side wall portions and bead portions continuous with both sides of the tread portion, and in which a rotational direction at the time of wearing the vehicle is specified,
Of the tread portion, the radius of curvature Rc of the tread surface at the center portion centered on the tire equator line is 150 to 250 mm, and the radius of curvature Rs of the tread surface at the shoulder portion located outside the center portion is 80 to 100 mm And
The tread surface has an inclined main groove in which a first groove portion and a second groove portion are connected via a bending point, and the first groove portion is disposed in a ground contact area when traveling straight, The groove portion 2 is disposed straddling the ground contact area when going straight and the outer ground area located outside the ground contact area when going straight,
The inclination angle θ1 of the first groove with respect to the tire circumferential direction is 0 to 23 °, and the inclination angle θ2 of the second groove with respect to the tire circumferential direction is 50 to 70 °.
The inflection point between the first groove portion and the second groove portion is on the outer side in the tire width direction than a position at which 17% of the half width of the tread periphery length is separated from the tire equator line Exist and
The ratio Rc / Rs of the radius of curvature Rc of the tread surface at the center portion to the radius of curvature Rs of the tread surface at the shoulder portion is expressed by the following formula (1):
1.7 ≦ Rc / Rs ≦ 3.1 (1)
A tire for a motorcycle characterized by satisfying the relationship represented by   2. The tire according to claim 1, wherein the length L 1 of the first groove portion is 34 to 82% of a half width of the tread periphery length.   The tire for a motorcycle according to claim 1 or 2, further comprising an intersecting belt layer composed of two or more inclined belts arranged so that cord directions cross each other between layers in the tire radial direction inner side of the tread surface.

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