JP4344623B2 - Pneumatic tires for motorcycles - Google Patents

Description

  The present invention relates to a pneumatic tire for a motorcycle including a bead filler made of rubber having a triangular cross section and a hard rubber filler on the outer side in the tire width direction of the carcass.

  In order to ensure stability during turning due to the recent increase in speed of motorcycles, it is necessary to ensure lateral rigidity that can withstand strong turning force, and as a countermeasure, tires are increased by increasing the bead filler. A technique for increasing the rigidity of the side portion has been taken.

  However, the above method has a tendency to reduce the absorbability with respect to road surface unevenness, and has a tendency to hinder stable running because it causes instability such that the installation surface rebounds.

Therefore, a technique has been developed to increase the turning force without increasing the rigidity of the entire side part as much as possible by intensively placing hard rubber in the side back region where a large amount of compression is applied particularly during turning (for example, Patent Documents). 1).
JP-A-9-39521

  However, due to the recent increase in horsepower and speed of motorcycles, even with the use of the above-mentioned new technology, the lack of turning power due to insufficient rigidity has become prominent, and further technical development has been required.

  In order to effectively improve such lateral rigidity, it is indispensable not only to increase the compression rigidity of the back surface of the bead but also to increase the tensile rigidity inside the vicinity of the bead core. However, since it is necessary not to impair the absorbability, the reinforcement needs to be minimized.

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a pneumatic tire for a motorcycle that improves lateral rigidity during turning and absorbability to absorb road surface irregularities during turning.

  In order to solve the above problems, the feature of the present invention is that a body portion that reinforces the pair of sidewall portions and the tread portion between the bead cores embedded in the pair of bead portions, and the bead core is folded back from the tire inner side to the outer side. A pneumatic tire for a motorcycle including a carcass having a folded portion and a bead filler made of rubber having a triangular cross section, disposed between the main body portion and the folded portion, the outer side in the tire width direction of the folded portion The hard rubber filler having substantially the same hardness as the bead filler, the folded portion extends outward in the tire radial direction to the range beyond the outer end of the hard rubber filler in the tire radial direction, and the tire width direction of the bottom portion of the bead filler If the width is W and the width in the tire width direction of the bead core is BW, 0.6 ≦ W / BW ≦ 1.1, and the heel end of the bead portion When the distance from the tread portion to the tread end is SH and the distance from the heel end of the beat portion to the outer end in the tire radial direction of the bead filler is 0.08 ≦ h / SH ≦ 0.20, hard If the maximum thickness of the rubber filler in the tire width direction is t, 0.1 ≦ t / BW ≦ 0.7, and the distance from the heel end of the beat portion to the outer end in the tire radial direction of the hard rubber filler is H Then, 0.3 ≦ H / SH ≦ 0.8, and the distance from the tire radial inner side end of the bead filler to the tire radial outer side of the hard rubber filler is A, and the distance from the tire radial outer end of the bead filler is hard. The gist of the present invention is a pneumatic tire for a motorcycle in which D / A ≦ 0.35, where D is the distance from the rubber filler to the inner side in the tire radial direction. Here, “substantially equivalent hardness” means that the hardness difference between the bead filler and the hard rubber filler is within 2 °.

  According to the pneumatic tire for a motorcycle according to the feature of the present invention, by arranging the bead filler and the high rubber filler at appropriate positions, the lateral rigidity at the time of turning and the absorbability to absorb the unevenness of the road surface at the time of turning are obtained. Can be improved.

  Further, the folded portion in the pneumatic tire for a motorcycle according to the feature of the present invention needs to extend outward in the tire radial direction to a range exceeding the inner radial end of the hard rubber filler. If the folded portion does not reach the inner end in the tire radial direction of the hard rubber filler, the turning force is reduced due to insufficient rigidity.

  Further, the pneumatic tire for a motorcycle according to the feature of the present invention needs to satisfy 0.6 ≦ W / BW ≦ 1.1. If this ratio is less than 0.6, the reinforcing effect is small, and if it exceeds 1.1, the rigidity is so great that the deterioration of the absorbability becomes remarkable.

  The pneumatic tire for a motorcycle according to the feature of the present invention needs to satisfy 0.08 ≦ h / SH ≦ 0.20. When this ratio is less than 0.08, the reinforcing effect is small, and when it exceeds 0.2, the rigidity becomes large and the deterioration of absorbability becomes remarkable.

  Further, the pneumatic tire for a motorcycle according to the feature of the present invention needs to satisfy 0.1 ≦ t / BW ≦ 0.7. When this ratio is less than 0.1, the reinforcing effect is small, and when it exceeds 0.7, the rigidity is so great that the deterioration of absorbability becomes remarkable.

  Also, the pneumatic tire for a motorcycle according to the feature of the present invention needs to satisfy 0.3 ≦ H / SH ≦ 0.8. When this ratio is less than 0.3, the reinforcing effect is small, and when it exceeds 0.8, the rigidity is so high that the deterioration of absorbability becomes remarkable.

  The pneumatic tire for a motorcycle according to the feature of the present invention needs to satisfy D / A ≦ 0.35. When the bead filler and the hard rubber filler are overlapped in the tire radial direction, if the overlapping amount is 35% or more, the rigidity of the overlapping region is increased, and the deterioration of the absorbability becomes remarkable. Further, when the bead filler and the hard rubber filler are separated from each other in the tire radial direction, if the separation amount is 35% or more, a region having low rigidity is generated locally, resulting in a decrease in turning force.

  Further, it is desirable that the hardness Hd of the bead filler rubber of the pneumatic tire for a motorcycle according to the feature of the present invention is 50 ° or more. If it is less than 50 °, the reinforcing effect is reduced. Here, “hardness Hd” refers to the hardness measured at a test temperature of 25 ° C. using a type A tester in a durometer hardness test according to JIS K6253-1993.

  A pneumatic tire for a motorcycle according to a feature of the present invention is disposed on the outer side in the tire radial direction of the carcass layer, and is formed by winding a cord having a strength of 137N or more spirally at an angle substantially toward the circumferential direction of the tire. It is desirable to further include a spiral belt layer. In the circumferential spiral belt, the ground contact portion is softer than a cross belt made by plying with a certain angle, so that the ground contact area can be increased while maintaining the belt effect, and the grip performance is improved. In addition, it is difficult to deform due to centrifugal force during high-speed running, and is often used for ultra-high-speed running tires. Therefore, in the structure using the spiral belt, the contribution of the side rigidity is large in the overall tire rigidity, so the effect of improving the lateral rigidity during turning and the absorbability to absorb the unevenness of the road surface during turning is effective. high.

  Further, the folded portion of the pneumatic tire for a motorcycle according to a feature of the present invention may extend outward in the tire radial direction to the inner side in the tire radial direction of the belt layer end. By arranging the folded portion in this way, the contribution of side rigidity is increased in the overall tire structure.

  Moreover, the hard rubber filler of the pneumatic tire for a motorcycle according to the feature of the present invention may be formed of two kinds of rubbers having different hardnesses. Rigidity can be ensured by concentrating hard rubber having a higher hardness in the side rear region where a large amount of compression is applied during turning.

  The pneumatic tire for a motorcycle according to the feature of the present invention is preferably used for a rear tire.

  Since cross belts can ensure the lightness of handling, in recent years, tires with a cross belt structure tend to be used at the front and tires with a circumferential spiral structure tend to be used at the rear. The pneumatic tire for a motorcycle according to the feature of the present invention preferably has a spiral belt structure, and its effect is high when applied to a rear tire.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire for two-wheeled vehicles which improves the lateral rigidity at the time of turning and the absorptivity which absorbs the unevenness | corrugation of the road surface at the time of turning can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Structure of pneumatic tires for motorcycles)
As shown in FIG. 1, the pneumatic tire for a motorcycle according to the embodiment of the present invention extends between the pair of bead portions 1 and the pair of sidewall portions 2 and the sidewall portions 2 with respect to the tire equatorial plane CL. And a tread portion 3 connected in a toroidal shape. The carcass 5 is a toroidal radial carcass that reinforces the bead part 1, the sidewall part 2, and the tread part 3 between a pair of bead cores 4 embedded in the bead part 1. Arranges the belt layer 6 and reinforces the tread portion 3. Note that the pneumatic tire for a motorcycle according to the present embodiment is a high-performance MC radial tire having a flatness ratio of 60% or less.

  The carcass layer is a textile carcass of at least one layer, and a body portion 5a that reinforces the pair of sidewall portions 2 and the tread portion 3 between the bead cores embedded in the pair of bead portions, and the bead core 4 from the tire inner side to the outer side. And a folded portion 5b. The carcass layer is made of a cord having a strength of 137N or more.

  The belt layer 6 is formed by embedding a single wire or a plurality of parallelly extending cords in the covering rubber. In the present embodiment, the belt layer 6 is a circumferential spiral belt layer that is wound in a spiral shape at an angle substantially toward the circumferential direction of the tire. The circumferential spiral belt is a radial tire belt having a structure in which one cord is continuously wound in the circumferential direction of the tire. Actually, there are many cases where several cords are arranged and wound at the same time for the convenience of manufacturing. As the cord of the belt layer 6, for example, polyamide such as 6,6-nylon can be used, and other fiber materials such as polyester and aromatic polyamide can be preferably used. Alternatively, a conventional twisted steel cord can be used. The strength of the cord of the belt layer 6 is 137N or more.

  In addition, since the belt layer 6 has a spiral belt structure, the contribution of side rigidity in the overall tire rigidity increases, so the pneumatic tire for a motorcycle according to this embodiment is preferably used as a rear tire.

  The pneumatic tire for a motorcycle according to the embodiment of the present invention has a bead filler 7 made of a rubber having a triangular cross section disposed between the main body 5a and the folded portion 5b, and on the outer side in the tire width direction of the folded portion 5b. And a hard rubber filler 8 having substantially the same hardness as the bead filler 7. The hardness Hd of the bead filler 7 and the hard rubber filler 8 is 50 ° or more.

  Hereinafter, the positional relationship among the bead core 4, the feed filler 7, the hard rubber filler 8, and the carcass folded portion 5b will be described in detail with reference to FIG.

  The folded portion 5b extends outward in the tire radial direction to a range exceeding the inner end in the tire radial direction of the hard rubber filler 8.

  Further, when the width in the tire width direction of the bottom side of the bead filler 7 is W and the width in the tire width direction of the bead core 4 is BW, 0.6 ≦ W / BW ≦ 1.1. The corner portion connected to the sidewall portion 2 of the bead portion 1 is defined as the heel portion 1a, the distance from the heel portion 1a end to the tread portion end of the tread portion 3 is SH, and from the heel portion 1a end to the tire radial outer end of the bead filler 7 Where h is 0.08 ≦ h / SH ≦ 0.20.

  Further, when the maximum thickness of the hard rubber filler 8 in the tire width direction is t, 0.1 ≦ t / BW ≦ 0.7. When the distance from the end of the heel portion 1a to the outer end in the tire radial direction of the hard rubber filler 8 is H, 0.3 ≦ H / SH ≦ 0.8. A is the distance from the tire radial inner end of the bead filler 7 to the tire radial outer side of the hard rubber filler 8, and D is the distance from the tire radial outer end of the bead filler 7 to the tire radial inner side of the hard rubber filler 8. Then, D / A ≦ 0.35. Here, the bead filler 7 and the hard rubber filler 8 may be arranged at positions overlapping in the tire radial direction or may be arranged at positions separated from each other. That is, the distance D may be a distance that overlaps in the tire radial direction (overlap amount) or a distance that is separated in the tire radial direction (separation amount).

  The pneumatic tire for a motorcycle according to the present embodiment is not limited to the structure shown in FIG. For example, as shown in FIG. 3, a two-layer cross belt may be provided instead of the circumferential spiral belt. For example, steel cords arranged in parallel, covered with coding rubber, and two layers laminated at an intersection angle of 15 to 30 degrees with respect to the tire equator line can be used. Such a cross belt structure can ensure the lightness of handling.

  Further, as shown in FIG. 4, the folded portion 5b of the pneumatic tire for a motorcycle according to the present embodiment may have a structure extending outward in the tire radial direction to the inner side in the tire radial direction of the belt layer 6 end. By arranging the folded portion 5b in this way, the contribution of side rigidity is increased in the overall tire structure.

  Furthermore, the hard rubber filler 8 of the pneumatic tire for a motorcycle according to the present embodiment may be formed of two kinds of rubbers having different hardnesses as shown in FIG. Here, the hardness of the rubber 8b on the inner side in the tire radial direction is larger than the hardness of the rubber 8a on the outer side in the tire radial direction (8b> 8a). Since the hardness of the rubber 8a on the outer side in the tire radial direction is 50 ° or more, 8b has a higher hardness. Of course, the type of rubber is not limited to the two types shown in FIG. 5, and three or more types of rubber may be used.

  The positional relationship among the bead core 4, the feed filler 7, the hard rubber filler 8, and the carcass folded-back portion 5 b in the bead portion 1 of the pneumatic tire for a motorcycle shown in FIGS. 3 to 5 is the same as that described in FIG. 2. is there.

(Operation and effect of the pneumatic tire for a motorcycle according to the present embodiment)
In order to cope with the recent increase in the speed of motorcycles, pneumatic tires for motorcycles have been required to have improved lateral stiffness during turning and absorbability to absorb road surface irregularities during turning.

  As a result of FEM (finite element method) analysis of the strain distribution generated inside the tire during turning, a compressive strain is generated at the upper edge of the rim flange contact on the side, and a large tension is generated on the carcass body near the bead core. It was found that the body ply was deformed to be bent outward.

  For this reason, in order to effectively improve the lateral rigidity, it is indispensable not only to increase the compression rigidity of the back surface of the bead but also to increase the tensile rigidity in the vicinity of the bead core. However, since it is necessary not to impair the absorbability, the reinforcement needs to be minimized.

  Therefore, the pneumatic tire for a motorcycle according to the present embodiment includes the hard rubber filler 8 having substantially the same hardness as the bead filler 7 on the outer side in the tire width direction of the folded portion 5b, and the folded portion 5b includes the hard rubber filler 8. , Extending to the outside in the tire radial direction up to a range beyond the outer end in the tire radial direction, assuming that the width in the tire width direction of the bottom side of the bead filler 7 is W and the width in the tire width direction of the bead core 4 is BW, 0.6 ≦ W / BW ≦ 1.1, SH is the distance from the heel part 1a end of the bead part 1 to the tread part 3 tread edge, and the distance from the heel part 1a end of the beat part 1 to the outer end in the tire radial direction of the bead filler 7 is If h is 0.08 ≦ h / SH ≦ 0.20, and if the maximum thickness of the hard rubber filler 8 in the tire width direction is t, 0.1 ≦ t / BW ≦ 0.7, beats Part 1 If the distance from the end of the portion 1a to the outer end in the tire radial direction of the hard rubber filler 8 is H, 0.3 ≦ H / SH ≦ 0.8, and the hard rubber filler 8 from the inner end in the tire radial direction of the bead filler 7 And D / A ≦ 0.35, where A is the distance from the outer side in the tire radial direction and D is the distance from the outer end in the tire radial direction of the bead filler 7 to the inner side in the tire radial direction of the hard rubber filler 8. For this reason, by arrange | positioning the bead filler 7 and the hard rubber filler 8 in a suitable position, the lateral rigidity at the time of turning and the absorptivity which absorbs the unevenness | corrugation of the road surface at the time of turning can be improved.

  Further, as shown in FIG. 1, the pneumatic tire for a motorcycle according to the present embodiment is disposed outside the carcass layer in the tire radial direction, and a cord having a strength of 137N or more is spiraled at an angle substantially toward the circumferential direction of the tire. A spiral belt layer 6 wound in a shape can be further provided. For this reason, since the contribution of the side stiffness is large in the overall tire stiffness, the effect of improving the lateral stiffness during turning and the absorbability to absorb the road surface irregularities during turning is high.

  Further, as shown in FIG. 4, the folded portion 5 b of the pneumatic tire for a motorcycle according to the present embodiment can be configured to extend outward in the tire radial direction to the inner side in the tire radial direction of the end of the belt layer 6. By arranging the folded portion 5b in this way, the contribution of side rigidity is increased in the overall tire structure.

  Further, the hard rubber filler 8 of the pneumatic tire for a motorcycle according to the present embodiment can be formed of two kinds of rubbers having different hardnesses as shown in FIG. Rigidity can be ensured by concentrating hard rubber having a higher hardness in the side rear region where a large amount of compression is applied during turning.

  The pneumatic tire for a motorcycle according to this embodiment preferably has a spiral belt structure, and the effect is high when applied to a rear tire.

  Examples of the pneumatic tire according to the embodiment of the present invention will be described in detail below. In order to confirm the effect of the present invention, the turning force and absorbency evaluation were performed on the seven types of tires of the examples to which the present invention was applied and the three types of tires of the comparative examples.

  In both the examples and the conventional example, the tire size was MCR190 / 50ZR17M / C, the rim diameter was MT6.0 × 17, and the internal pressure was 290 kPa.

  As shown in FIG. 6, Comparative Example 1 and Comparative Example 2 were structures having no hard rubber filler as compared with the structure of FIG. 1 described in the embodiment.

  As shown in FIG. 7, Comparative Example 3 was a structure having no bead filler as compared to the structure of FIG. 1 described in the embodiment.

  Examples 1-7 were structures which have a bead filler and a hard rubber filler, as shown in FIG.

  The positional relationship between the bead core 4, the feed filler 7, and the hard rubber filler 8 in Comparative Examples 1 to 3 and Examples 1 to 7 is as shown in Table 1. In the column of the distance D% in Table 1, “+” indicates the overlap amount when the bead filler 7 and the hard rubber filler 8 overlap in the tire radial direction, and “−” indicates the bead filler 7 and the hard rubber. The separation amount when the filler 8 is separated in the tire radial direction is shown.

The hardness of the bead filler in Comparative Examples 1 and 2 and Examples 1 to 7 was 91 °, and the hardness of the hard rubber filler in Comparative Example 3 and Examples 1 to 7 was 91 °. Moreover, the strength of the belt cords in Comparative Examples 1 to 3 and Examples 1 to 7 was 372N.

  The results of the evaluation of turning force and absorbency are expressed as an index of the results of driving stability evaluation using actual vehicles. About turning force evaluation, it was set as the index display which set the comparative example 2 to 100, and it was supposed that it was so favorable that the value was large. In addition, for the evaluation of absorbency, index display was made with Comparative Example 1 as 100, and the larger the value, the better.

(result)
The results are shown in Table 1.

  It turned out that Examples 1-7 improve turning power and absorptivity compared with comparative examples 1-3. Therefore, it has been found that by including the bead filler and the hard rubber filler, the lateral rigidity at the time of turning and the absorbability for absorbing the unevenness of the road surface at the time of turning are improved.

  Moreover, it turned out that Example 1, Example 5, and Example 6 improve turning force and absorptivity with sufficient balance compared with the other Examples. Therefore, by setting W / BW to about 0.9, h / SH to about 0.15, t / BW to about 0.4, H / SH to about 0.6, and D to about 22 to 30%, It was found that both rigidity and absorbency were improved.

  Moreover, it turned out that turning force improves Example 2 compared with Example 1. Therefore, it was found that by setting W / BW to about 1.0 and h / SH to about 0.2, the lateral rigidity during turning is improved.

  Further, it was found that the turning force of Example 3 was improved as compared with Example 1. Therefore, it was found that by setting W / BW to about 1.1, the lateral rigidity during turning is improved.

  Moreover, it turned out that turning force improves Example 4 compared with Example 1. Therefore, it was found that by setting t / BW to about 0.6, the lateral rigidity during turning is improved.

  Moreover, it turned out that the turning force of Example 7 improves compared with Example 1. Therefore, it was found that by setting D to about +30, the lateral rigidity during turning is improved.

1 is a cross-sectional view including a tire rotation axis of a pneumatic tire for a motorcycle according to an embodiment (No. 1). It is an enlarged view of the bead part of FIG. FIG. 6 is a cross-sectional view including the tire rotation axis of the pneumatic tire for a motorcycle according to the present embodiment (No. 2). FIG. 3 is a cross-sectional view including a tire rotation axis of a pneumatic tire for a motorcycle according to the present embodiment (No. 3). FIG. 6 is a sectional view including a tire rotation axis of a pneumatic tire for a motorcycle according to the present embodiment (No. 4). 3 is a cross-sectional view including a tire rotation axis of a pneumatic tire for a motorcycle according to Comparative Example 1 and Comparative Example 2. FIG. FIG. 6 is a cross-sectional view including a tire rotation axis of a pneumatic tire for a motorcycle according to Comparative Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Bead part 2 ... Side wall part 3 ... Tread part 4 ... Bead core 5a ... Carcass main-body part 5b ... Carcass folding | turning part 6a, 6b, 6c ... Belt layer 7 ... Bead filler 8, 8a, 8b ... Hard rubber filler

Claims (5)

A carcass having a main body portion that reinforces a pair of sidewall portions and a tread portion between bead cores embedded in a pair of bead portions, a folded portion that is folded back from the tire inner side to the outer side in the bead core, and the main body portion, A pneumatic tire for a motorcycle including a bead filler made of rubber having a triangular cross section disposed between the folded portions,
On the outer side in the tire width direction of the folded portion, comprising a hard rubber filler having substantially the same hardness as the bead filler,
The folded portion extends outward in the tire radial direction to a range exceeding the inner end in the tire radial direction of the hard rubber filler,
When the width in the tire width direction of the bottom portion of the bead filler is W and the width in the tire width direction of the bead core is BW, 0.6 ≦ W / BW ≦ 1.1,
When the distance from the heel end of the bead portion to the tread end of the tread portion is SH, and the distance from the heel end of the beat portion to the outer end in the tire radial direction of the bead filler is h, 0.08 ≦ h /SH≦0.20,
When the maximum thickness of the hard rubber filler in the tire width direction is t, 0.1 ≦ t / BW ≦ 0.7,
When the distance from the heel portion end of the beat portion to the outer end in the tire radial direction of the hard rubber filler is H, 0.3 ≦ H / SH ≦ 0.8,
A is the distance from the tire radial inner end of the bead filler to the tire radial outer side of the hard rubber filler, and D is the distance from the tire radial outer end of the bead filler to the tire radial inner side of the hard rubber filler. Then, it is D / A <= 0.35. The pneumatic tire for motorcycles characterized by the above-mentioned.   2. A spiral belt layer that is disposed outside the carcass layer in the tire radial direction and is formed by winding a cord having a strength of 137N or more in a spiral shape at an angle substantially toward the circumferential direction of the tire. The pneumatic tire for motorcycles described in 1.   The pneumatic tire for a motorcycle according to claim 1 or 2, wherein the folded portion extends outward in the tire radial direction to the inner side in the tire radial direction of the belt layer end.   The pneumatic tire for a motorcycle according to any one of claims 1 to 3, wherein the hard rubber filler is formed of two kinds of rubbers having different hardnesses. The pneumatic tire for a motorcycle according to any one of claims 1 to 4, wherein the pneumatic tire is used for a rear tire.

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