JP4118391B2 - Pneumatic radial tire for motorcycles - Google Patents

Description

【００４５】
【発明の効果】
前記実施例からも明らかなように、この発明によれば、主にはそれのベルト構造の故に、ハンドリングの軽快性を高めることができ、また、傾斜副溝をもって、すぐれたウェットグリップ性をおよびシミーの有効なる抑制を実現することができる。
しかも、その傾斜副溝それ自身の形成態様に基づき、溝底クラックの発生を十分に防止することができる。
【図面の簡単な説明】
【図１】この発明に係るトレッドパターンの形態を、複数種類の傾斜副溝とともに示す略線展開図である。
【図２】図１のＡ−Ａ線に沿う断面図である。
【図３】この発明に係るベルトの構成形態を示す子午線断面図である。
【図４】比較タイヤ１のベルト構造およびパターン構成を示す図である。
【図５】比較タイヤ２のベルト構造およびパターン構成を示す図である。
【図６】実施例タイヤのベルト構造およびパターン構成を示す図である。
【図７】従来タイヤのトレッドターンの略線展開図である。
【図８】他の従来タイヤのトレッドターンの略線展開図である。
【符号の説明】
１ トレッド踏面
２，３ 傾斜主溝
４〜１１ 傾斜副溝
７ａ，７ｂ 副溝部分
８ａ，９ａ，１０ａ，１０ｂ 主要部分
１２ ビードコア
１３ ラジアルカーカス
１４ ベルト
１４ａ ベルトコード
１５ トレッド
１５ａ トレッド踏面[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a pneumatic radial tire for motorcycles, particularly a tire suitable for use on a front wheel, and in particular, excellent durability, wet road surface and dry road based on an appropriate combination of a pattern configuration and a belt structure. It realizes excellent handling stability.
[0002]
[Prior art]
A belt provided with a belt cord extending substantially in the tread circumferential direction is provided, and an inclined main groove having an acute side inclination angle of 45 ° or more with respect to the tread circumferential direction is formed on the tread surface from the tread center to the tread shoulder region. As a conventional tread pattern of this type of tire having an extended directional pattern, for example, with respect to the inclined main groove, each side of the tread center C as shown in FIG. In some cases, the inclined main grooves 51 and 52 that are curved in a convex shape toward the rotational direction of the tire are provided symmetrically with respect to the tread center C.
[0003]
However, in such a tire, and in the tread pattern, there is a problem that shimmy is likely to occur particularly in the front wheel tire due to the high bending rigidity of the tread in the meridian section of the tire. Further, since the circumferential direction components of the main grooves 51 and 52 are small, there is a problem that wet drainage performance, side slip resistance and the like are low, and high road surface grip force on a wet road surface cannot be exhibited.
[0004]
On the other hand, in the tread tread surface, in addition to the inclined main grooves 51, 52, in addition to providing a circumferential groove that is linearly continuous in the tread circumferential direction, when adjusting the bending rigidity of the tread, Although it is possible to suppress the occurrence of shimmy and improve wet drainage performance, bending at the groove bottom portion of the circumferential groove is related to the belt layer cord extending substantially in the tread circumferential direction. There is a durability inconvenience that the drag is locally reduced and the groove bottom crack is generated relatively early.
[0005]
Therefore, as shown in part in FIG. 8, in addition to the inclined main grooves 51 and 52, the tread tread surface is provided with a zigzag circumferential groove 53 that continuously extends in a zigzag shape in the tread circumferential direction. An inclined sub-groove 54 or 55 that intersects the main grooves 51 and 52 or opens at both ends is provided, or extends between the main grooves 51 and 52 in a straight line without communicating with them. For example, an inclined sub-groove 56 that is inclined at a large angle α exceeding 30 ° with respect to the direction is provided.
[0006]
According to these, because of the presence of the zigzag circumferential groove 53 and the inclined sub-grooves 54, 55, or 56, generally, improvement of wet drainage performance is realized together with suppression of shimmy.
[0007]
[Problems to be solved by the invention]
However, when the zigzag circumferential groove 53 continuous in the tread circumferential direction is provided, it is better than the straight groove, but it is also disadvantageous to stability and maneuverability because the rigidity in the tire meridian section is too low. In addition, when the inclined sub-grooves 54 and 55 that intersect or open the main grooves 51 and 52 are provided, the rigidity is lower than that of the zigzag circumferential groove 53, which is further disadvantageous in terms of stability and maneuverability.
Moreover, in any of these cases, the occurrence of groove bottom cracks in the circumferential groove 53 and the sub-grooves 54 and 55 cannot be sufficiently suppressed.
[0008]
When the inclined sub-groove 56 having an inclination angle α exceeding 30 ° with respect to the tread circumferential direction is provided, the wet drainage performance is not so improved, and the tread circumferential component of the sub-groove 56 is small. Also, since the tread circumferential length of the groove edge is short, there is a problem that the side slip resistance of the tire cannot be increased as expected.
[0009]
Therefore, the applicant previously as Japanese Patent Application No. 10-1434, while preventing the occurrence of shimmy, while improving the stability and maneuverability on the dry road surface, in addition to ensuring excellent wet drainage performance , Proposed a pneumatic radial tire for motorcycles that has improved side-slip resistance sufficiently, improved handling stability on wet road surfaces, and effectively prevented the occurrence of groove bottom cracks, and advantageously improved tread durability .
This invention is a further improvement of the invention according to the previous application. By properly combining the pattern configuration according to the invention and the belt structure, in addition to the above effects, the meridian section of the tire Increases the rigidity balance to prevent the occurrence of groove bottom cracks more advantageously, realizes the bending rigidity of the tread that is effective in reducing the cornering power against the handle shimmy, and gives a camber angle in terms of maneuverability and light of the case is to provide a pneumatic radial tire for a motorcycle capable of obtaining good balance linearity of the change in the operating force required for it.
[0010]
[Means for Solving the Problems]
A pneumatic radial tire for a motorcycle according to the present invention includes a belt in which a belt cord is substantially extended in a tread circumferential direction, and an inclined main groove having an acute angle inclination angle with respect to the tread circumferential direction of 45 ° or more on a tread surface. Extending from the tread center or the vicinity thereof to the tread shoulder region, for example, on each side of the tread center, between the two inclined main grooves, the acute angle side inclination angle with respect to the tread circumferential direction thereof is It has a directional pattern formed by extending inclined sub-grooves that are smaller than the inclined main grooves, and the belt cord arrangement density is larger than the tread shoulder area in the tread center area, and the groove width of the inclined main grooves is Assemble the tire between the tread ends under no load condition with the tire mounted on the standard rim and filled with 80% of the maximum air pressure. The main portion of the inclined sub-groove having a width and depth larger than the other portion is terminated without opening the inclined main groove, and the tread of the main portion is adjusted to be 3 to 15% of the length. The acute side inclination angle with respect to the circumferential direction is set to a range of 0 to 30 °, the groove width of the main portion is made narrower than that of the inclined main groove, and the length of the main portion in the circumferential direction of the tread is made smaller than that of the inclined main groove. and 30 to 80% of the disposition pitch, and further that of 50% to 100% of the range of the inclined main groove depth of the main portion, together with a tread circumferential length of each inclined main groove, the inclined sub The total length in the tread circumferential direction, which is the sum of the lengths of the main portions of the grooves in the tread circumferential direction , is made longer in the tread center area than in the tread shoulder area.
[0011]
Here, the inclined sub-groove can be disposed so as to overlap the tread center. In this case, the inclined sub-groove extends between the two pairs of inclined main grooves communicating with each other at the tread center. Become.
Further, the tread center area here means an inner area when a distance of about 1/4 of the peripheral length is taken on both sides of the tread center. Accordingly, the tread shoulder region is the outer region thereof.
[0012]
Here, the main part of the inclined sub-groove refers to a wide part and a deep part when the sub-groove has at least one of a groove width and a groove depth. When the groove width and the groove depth are both constant, the entire inclined sub-groove becomes the main part.
[0013]
By the way, when each of the sub-groove has a narrow groove width and a deep groove depth part and a wide width and shallow part, the main part is a deep groove part. And when there are multiple wide or deep portions in one sub-groove, these multiple locations are all the main parts of one inclined sub-groove. The length of the main part is the sum of them.
This is almost the same when a plurality of sub-groove portions extend at intervals on a single straight line.
[0014]
In such a pneumatic radial tire, the belt cord is extended substantially in the tread circumferential direction by, for example, spiral winding of one or a plurality of cords, so that high speed durability and stable driving on a dry road surface are achieved. In addition, the inclined main groove has an acute side inclination angle of 45 ° or more with respect to the tread circumferential direction, and smooth and quick side drainage is achieved. In addition, it is possible to provide braking performance, and further, it is possible to ensure bending rigidity in the meridian cross section and to provide excellent road surface grip force when turning on a dry road surface.
[0015]
In addition, by setting the groove width of the inclined main groove in the range of 3 to 15% of the peripheral length between the tread ends, the tread bending rigidity in the equator section of the tire or in a section parallel thereto is moderately increased. By lowering, the contact length / width can be increased moderately, and excellent grip on dry and wet roads, slip control and stability can be achieved, and sufficient drainage can be achieved. And excellent grip on wet roads. That is, if it is less than 3%, the tread bending rigidity cannot be advantageously reduced, and the drainage cannot be sufficiently ensured. Therefore, the above grip force, slip control performance, stability, and wet road The grip is not enough. On the other hand, if it exceeds 15%, the grip stability on the dry road cannot be sufficiently ensured because the tread rigidity is too low.
Here, the groove width of the inclined main groove is specified based on the peripheral length under no-load condition filled with 80% of the maximum air pressure. When considering this, the ratio of the contact width to the peripheral length is used to define the main groove width that works effectively in the contact surface against the change of the contact width in proportion to the peripheral length. This is because is appropriate and simple.
[0016]
Further, the inclined sub-groove is finished without opening the main portion of the inclined sub-groove to the inclined main groove, and the acute angle side inclination angle of the main portion with respect to the tread circumferential direction is in a range of 0 to 30 °. In addition to improving the wet drainage performance by comprehensively optimizing the width, depth, etc. of the main part, the arrangement method, dimensions, etc. of the inclined sub-grooves, the tread bending within the meridian section of the tire The groove bottom crack resistance is advantageously improved by securing a moderate rigidity, and the groove edge length effective for the lateral direction input can be sufficiently secured to provide a high side slip resistance. An inclined sub-groove can be arranged at a position particularly effective for lowering the cornering power with respect to the handle shimmy, that is, in a contact area during straight traveling.
[0017]
As a result, it is possible to increase the lateral grip on wet roads, bring about the required rigidity when driving on dry roads, and fully optimize the lightness and stability of handling. Especially in the front tire, the occurrence of shimmy can be effectively suppressed.
[0018]
By the way, when the inclination angle of the main part exceeds 30 °, the drainage performance is lowered, and the lateral grip force on the wet road surface, in other words, the side slip resistance may be lowered.
[0019]
Further, here, by making the groove width of the main portion narrower than that of the inclined main groove, it is possible to effectively ensure steering stability and wear resistance. That is, if the groove width of the main part is wider than that of the inclined main groove, the tread bending rigidity in the meridian section may be reduced more than necessary, and the steering stability may be impaired. The wear resistance may be deteriorated.
[0020]
In addition, by making the length of the tread circumferential direction of the main portion in the range of 30 to 80% of the pitch of the inclined main groove, it is possible to ensure higher wet drainage performance, side slip resistance, etc. Can also be increased sufficiently. That is, when it is less than 30%, it is difficult to sufficiently exert the effect of arranging the inclined sub-groove, and when it exceeds 80%, the bending rigidity in the meridian cross section of the tread becomes too low, and steering stability is reduced. The decline cannot be denied.
[0021]
In addition, in this tire, the depth of the main portion is set to 50 to 100% of that of the inclined main groove, thereby ensuring better wet drainage performance. That is, if it is less than 50%, wet drainage performance tends to be insufficient, and if it exceeds 100%, the tread thickness on the inner periphery side from the groove bottom becomes too thin, and there is a high risk of occurrence of puncture due to nails or the like. Become.
[0022]
In addition, here, the belt cord density is made larger in the tread center area than in the tread shoulder area, and the total length in the tread circumferential direction of each of the inclined main grooves and the sub-groove main parts is determined by the tread center. By making the length longer than the tread shoulder area in the area, the bending rigidity in the meridian cross section of the tread is compared with the mutual arrangement mode of the belt cord and the inclined subgroove by combining with the above-described configuration. Under the relation, it is possible to appropriately balance and secure the groove bottom crack resistance, and to advantageously improve the groove edge length against the lateral input. Also, for handle shimmies, this also obtains bending rigidity within the meridian section of the tread that is appropriate for lowering the cornering power due to the belt cord arrangement density distribution and the inclined sub-groove arrangement mode. In addition, a bending stiffness distribution suitable for ensuring steering stability can be obtained.
[0023]
Therefore, according to this, it becomes possible to balance each effect mentioned above about the lateral direction grip force on a wet road surface, the rigidity feeling on a dry road surface, etc. more effectively.
[0024]
By the way, under the belt structure where the density of belt cords is larger in the tread center area than in the tread shoulder area, the total length in the tread circumferential direction of the main part of each inclined main groove and sub-groove is calculated as the tread center area and the tread. If it is equivalent to the shoulder area, or if it is made longer in the tread shoulder area, a groove bottom crack is likely to occur in the tread shoulder area where the bending rigidity in the meridian cross section is further reduced. By increasing the rigidity, straight running stability is deteriorated and shimmy is likely to occur. Furthermore, the rigidity of the ground contact portion when the camber angle is applied is reduced, the cornering force is reduced, and the turning force is reduced.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on the drawings.
FIG. 1 is a schematic line development view partially showing the form of a tread pattern according to the present invention with respect to eight kinds of inclined sub-grooves. Normally, all of the inclined sub-grooves are arranged symmetrically with respect to the tread center. And repeatedly formed at equal pitches in the tread circumferential direction.
[0026]
As shown in the figure, inclined main grooves 2 and 3 having an acute-side inclination angle β of 45 ° or more with respect to the tread circumferential direction are linearly extended from the tread center C to the tread end E on the tread road surface 1. At the same time, the inclined main grooves 2 and 3 are positioned symmetrically with respect to the tread center C.
[0027]
Here, each of the inclined main grooves 2 and 3 has a peripheral length of 3 to 15 between the tread ends in an unloaded state in which the tire is assembled to the standard rim and filled with 80% of the maximum air pressure. % Having a groove width in the range of%.
[0028]
The first aspect of the inclined sub-groove formed between the inclined main grooves is positioned so as to overlap the tread center C as shown by 4 in the figure, and ends without opening any of the inclined main grooves. The inclined sub-groove 4 has a constant width and depth over its entire length. Accordingly, the inclined sub-groove 4 has an acute-side inclination angle of 0 ° with respect to the tread circumferential direction and does not have a substantial inclination, and the whole forms a main part.
[0029]
By the way, here, the groove width of the inclined sub-groove 4 is narrower than that of the inclined main grooves 2 and 3, and the length in the tread circumferential direction is 30 to 80 of the arrangement pitch of the inclined main grooves 2 and 3. % And its depth is in the range of 50-100% of that of the inclined main grooves 2,3.
[0030]
Although the inclined sub-groove 4 as described above extends substantially in the same direction as the belt layer cord, the sub-groove 4 is discontinuous with the inclined main grooves 2 and 3, and the discontinuous portion is not present. Since it functions to keep the tread rigidity sufficiently high against bending deformation in the meridian section of the tire, the occurrence of cracks in the bottom of the sub-groove 4 is sufficiently prevented. In addition, the sub-groove 4 extending in the tread circumferential direction can provide particularly excellent wet drainage performance, and the groove edge can provide a high side slip resistance against the wet road surface.
[0031]
In the figure, 5 and 6 indicate the second and third aspects of the inclined sub-groove, respectively. These sub-grooves 5 and 6 extend at the respective sides of the tread center C so as to be inclined in the same direction as the inclined main grooves 2 and 3, and have an inclination angle θ on the acute angle side with respect to the tread circumferential direction. ₁ and θ ₂ are in the range of 0 to 30 °.
[0032]
In this case, the circumferential length of the tread is longer than the minor groove 6 in the minor groove 5, but any of those circumferential lengths sufficiently satisfies the requirements described above. The same applies to the groove width and the groove depth.
[0033]
The inclined sub-groove 7 of the fourth aspect is composed of two sub-groove portions 7a and 7b that are spaced on the same straight line. Here, the sub-groove portions 7a and 7b are Both form the main part of the sub-groove 7. Therefore, the tread circumferential length of the main portion here means the tread circumferential direction component of the sum of the sub-groove portions 7a and 7b.
[0034]
The inclined sub-groove 8 of the fifth aspect extends toward the tread end side substantially parallel to the main groove 3 at the end of the wide main portion 8a inclined in the same direction as the inclined main groove 3 on the tire rotation direction side. The narrow bent portion 8b is provided, and here, the main portion 8a is assumed to satisfy the above requirements.
[0035]
As shown in FIG. 1, the inclined sub-groove 9 according to the sixth aspect has a large groove width at each end of the main portion 9a having a large groove width and a deep groove depth as shown in FIG. 3, straight extension portions 9b and 9c having a narrow groove width and a shallow depth are formed. Again, the main part 9a shall satisfy all of the above-mentioned requirements.
[0036]
In the inclined sub-groove 10 of the seventh aspect, the main portions 10a and 10b formed in substantially the same manner as the sub-groove parts 7a and 7b of the inclined sub-groove 7 of the fourth aspect are mutually connected with a narrow intermediate portion 10c. Here, the intermediate portion 10c does not become a main portion.
The inclined sub-groove 11 of the eighth aspect has an inclined direction opposite to the main groove 3.
[0037]
As described above, various aspects of the inclined sub-groove have been described. By forming at least one inclined sub-groove in these aspects regularly on the tread surface 1, as described above, high wet drainage and side slip In addition to providing drag, it is possible to greatly improve the tread durability by preventing the occurrence of cracks in the bottom of the sub-groove.
[0038]
FIG. 3 is a meridian cross-sectional view showing the configuration of the belt according to the present invention, in which 12 is a pair of bead cores, 13 is a toroidal extension between the bead cores, and each end portion is a bead core. A radial carcass wound around 12 from the inside to the outside is shown.
[0039]
Here, a belt 14 and a tread 15 are sequentially arranged on the outer peripheral side of the crown portion of the radial carcass 13, and the belt 14 is substantially moved in the tread circumferential direction by, for example, spiral winding of a belt cord 14a. In addition to the extended configuration, the belt cord 14a is arranged in a density that is greater than the tread shoulder region in the tread center region, and is formed on the tread 15a of the tread 15 as described above. The total length in the tread circumferential direction of both the grooves 2 and 3 and the main portions of the inclined sub-grooves 4 to 11 is made longer in the tread center area than in the tread shoulder area.
[0040]
According to these things, it is possible to provide excellent lateral grip on wet roads, and in addition, rigidity on dry roads, lightness of handling, stability, shimmy suppression etc. The effect of the above can be effectively balanced and exerted by the rigidity distribution as required within the meridian section based on the arrangement of the belt cord 14a and the inclined subgrooves 4 to 11.
[0041]
【Example】
Featuring various handling and wet grip performances on dry roads when driving a real vehicle when a pneumatic radial tire for motorcycles of 120 / 70ZR17 is filled with air pressure of 2.5 kg / cm ² and used as a front wheel tire. The evaluation was made with a ring, and the groove bottom crack resistance was evaluated with a drum test. The results are shown in Table 1.
[0042]
Here, the comparative tire 1 has the belt structure and the pattern configuration shown in FIG. 4, the comparative tire 2 has the belt structure and the pattern configuration shown in FIG. 5, and the example tire has those shown in FIG. It was supposed to have.
The number of belt cords of the comparative tire 1 is 58/5 cm in the tread center area and 42/5 cm in the tread shoulder area, and that of the comparative tire 2 is both in the tread center area and the tread shoulder area. 50 tires / 5 cm, and that of the example tire was the same as that of the comparative example tire 1.
[0043]
Further, in the tread patterns shown in FIGS. 4 to 6, since the inclined main grooves are all formed under the same conditions, the total length in the tread circumferential direction of only the inclined subgroove is a ratio to the tread circumferential length. As a result, both the comparative tire 2 and the example tire were 50% in the tread center region and 20% in the tread shoulder region.
[0044]
[Table 1]

[0045]
【The invention's effect】
As is clear from the above-described embodiments, according to the present invention, the lightness of handling can be improved mainly because of the belt structure thereof, and excellent wet grip performance can be achieved with the inclined sub-groove. Effective suppression of shimmy can be realized.
In addition, the occurrence of groove bottom cracks can be sufficiently prevented based on the formation of the inclined subgroove itself.
[Brief description of the drawings]
FIG. 1 is a schematic line development view showing a form of a tread pattern according to the present invention together with a plurality of types of inclined sub-grooves.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a meridian cross-sectional view showing the configuration of the belt according to the present invention.
4 is a view showing a belt structure and a pattern configuration of a comparative tire 1. FIG.
FIG. 5 is a view showing a belt structure and a pattern configuration of a comparative tire 2;
FIG. 6 is a diagram showing a belt structure and a pattern configuration of an example tire.
FIG. 7 is a schematic development view of a tread turn of a conventional tire.
FIG. 8 is a schematic development view of a tread turn of another conventional tire.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tread tread 2, 3 Inclined main groove 4-11 Inclined sub groove 7a, 7b Sub groove part 8a, 9a, 10a, 10b Main part 12 Bead core 13 Radial carcass 14 Belt 14a Belt cord 15 Tread 15a Tread tread

Claims (1)

A belt having a belt cord extending substantially in the tread circumferential direction is provided, and an inclined main groove having an acute side inclination angle of 45 ° or more with respect to the tread circumferential direction is formed on the tread tread shoulder from the tread center or the vicinity thereof. A pneumatic radial for two-wheeled vehicles having a directional pattern formed by extending an inclined sub-groove that is smaller than the inclined main groove between the inclined main grooves and having an acute-side inclination angle with respect to the tread circumferential direction. Tire,
The belt cord density is greater in the tread center area than in the tread shoulder area.
The groove width of the inclined main groove is in the range of 3 to 15% of the peripheral length between the tread ends under no load condition with the tire assembled to the standard rim and filled with 80% of the maximum air pressure. ,
The main portion having at least one of the width and the depth of the inclined sub-groove larger than the other portion is terminated without opening the inclined main groove, and the acute inclination angle of the main portion with respect to the tread circumferential direction is set to 0 to 30. The width of the main portion is narrower than that of the inclined main groove, and the length in the tread circumferential direction of the main portion is in the range of 30 to 80% of the pitch of the inclined main groove. The depth of the part is in the range of 50 to 100% of that of the inclined main groove,
The total length in the tread circumferential direction of the sum of the tread circumferential length of each inclined main groove and the tread circumferential length of the main part of the inclined sub-groove is made longer in the tread center area than in the tread shoulder area. Pneumatic radial tire for motorcycles.

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