JP6514987B2 - Pneumatic tire for motorcycles - Google Patents

Description

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

  Heretofore, in the case of pneumatic tires for motorcycles, there has been a problem in that the durability of the tire is reduced due to breakage of the belt end or the ply end, especially when traveling under a relatively high load. The

  The inventors have found that the cause of such breakage of the belt end and the ply end is that the temperature inside the tire becomes high near the ground contact end of the tire during traveling, and that the heat radiation can be promoted in such a portion of the tire. Was found to be effective in improving the durability of the

  Therefore, in order to improve the durability of the tire, it is effective to provide a heat dissipation groove near the ground contact end to reduce the temperature inside the tire near the ground contact end. However, when the groove is provided near the ground contact end, the steering stability of the tire may be impaired.

  Then, an object of this invention is to provide the pneumatic tire for motorcycles which improved durability, maintaining steering stability of a tire.

The configuration of the present invention is as follows.
(1) In the pneumatic tire for motorcycles of the present invention, the tire is mounted on the application rim, filled with the prescribed internal pressure, and in the no-load reference state, from the tire equatorial plane to the tread end side The tread width of the tread surface, which is 50% apart from the half width of the peripherial length of the tread surface along the tire width direction of the tread surface, and 82% apart, in the tire width direction of the tread surface. When the area is an intermediate area, the intermediate area in each half of the tire includes a circumferential groove continuous in the circumferential direction of the tire and a cross groove extending intersecting the circumferential groove, the circumferential groove being the circumferential groove And at least one of the intersections with the intersection groove has a raised bottom adjacent to the intersection and in the circumferential direction of the tire, wherein the groove depth is shallower than the other part of the circumferential groove. To.

  According to the pneumatic tire for a motorcycle of the present invention having such a configuration, it is possible to improve the durability while maintaining the steering stability of the tire.

Here, the above “application rim” is an industrial standard effective for the area where the tire is produced and used, and in Japan, JATMA (Japan Automobile Tire Association) JATMA YEAR BOOK, in Europe ETRTO (The European Tire Standard rims in application size (STANDARDS MANUAL, ETRTO STANDARDS MANUAL, Measuring Rim, TRA described in STANDARDS MANUAL of the United States of America and YEAR BOOK of TRA (The Tire and Rim Association, Inc.) in the US) Design Rim in YEAR BOOK.
In addition, “specified internal pressure” refers to the air pressure corresponding to the maximum load capacity in the application size plating described in the above-mentioned JATMA YEAR BOOK etc. “Maximum load capacity” refers to the tire according to the above standard The maximum mass that can be loaded.

The “groove depth” in the present invention is the tire mounted on the applicable rim, filled with a prescribed internal pressure, and unloaded (hereinafter referred to as “reference state”), from the groove opening position to the tread surface Up to the maximum depth position shall be measured parallel to the tire radial direction.
In addition, “a circumferential groove continuous in the tire circumferential direction” may extend outside the intermediate region without being continuous in the intermediate region.

(2) In the pneumatic tire for a motorcycle according to the present invention, a value obtained by dividing the tire circumferential length of the portion other than the raised bottom portion of the circumferential groove by the pattern pitch length in the tire circumferential direction is 0.50 or more 0 It is preferable that it is .85 or less.
According to this configuration, it is possible to further improve the heat radiation effect by the circumferential groove while maintaining the steering stability more reliably.

  In addition, "pattern pitch" means the tire circumferential direction length per unit of the tread pattern repeated in the tire circumferential direction, and when the tire circumferential direction length per one unit changes in the tire circumferential direction, It shall refer to its average length.

(3) In the pneumatic tire for a motorcycle according to the present invention, the groove depth is 2.5 mm or more and 8.0 mm or less in the portion other than the bottom raising portion of the circumferential groove, and the groove depth in the bottom raising portion of the circumferential groove It is preferable that it is 0.5 mm or more and 2.0 mm or less.
According to this configuration, it is possible to further improve the heat radiation effect by the circumferential groove while maintaining the steering stability more reliably.

(4) In the pneumatic tire for motorcycles of the present invention, it is preferable that the negative ratio in the intermediate region is 25% or more and 55% or less.
According to this configuration, it is possible to further improve the heat radiation effect by the circumferential groove while maintaining the steering stability more reliably.
The “negative ratio” means the ratio {(groove area / tread area) × 100 (%)} of the groove area in the intermediate area to the area of the tread area of the intermediate area.

  According to the present invention, it is possible to provide a pneumatic tire for a motorcycle having improved durability while maintaining steering stability of the tire.

1 is a cross-sectional view in the tire width direction of a pneumatic tire for a motorcycle according to an embodiment of the present invention. FIG. 2 is a partial development view of a tread surface of a pneumatic tire for a motorcycle according to FIG. It is sectional drawing in alignment with the BB line of FIG.

Hereinafter, a pneumatic tire for a motorcycle (hereinafter, also simply referred to as a "tire") of the present invention will be described in detail with reference to the drawings, by exemplifying an embodiment thereof.
FIG. 1 shows a tire width direction cross section of a tire according to an embodiment of the present invention. This tire has a carcass 5 straddling between a pair of bead portions 11 as a skeleton, and a pair of sidewall portions 12 outside the bead portion 11 in the tire radial direction, and a tread portion 13 straddling between the sidewall portions 12 It is equipped. Although the carcass in the present embodiment is formed of one ply, two or more plies may be arranged. Moreover, although the inclined belt 3 which consists of two layers of inclined belt layers 3a and 3b is arrange | positioned on the tire radial direction outer side of the carcass 5 in the tread part 13 in this embodiment, it can also be set as another belt structure. . In the two inclined belt layers 3a and 3b, the respective cords are inclined with respect to the tire circumferential direction and extend across the layers.

  FIG. 2 shows a part of the tread surface 6 of the tire according to the present embodiment in an expanded state. In the present embodiment, patterns which are line symmetrical with respect to the equatorial plane CL are arranged mutually offset in the tire circumferential direction X on one side and the other side of the tread surface 6 with the tire equatorial plane CL as a boundary. ing. Accordingly, the configuration of the tread surface 6 of the embodiment will be described here as a representative of the tire half on the left side as viewed in the drawing.

First, in the present embodiment, from the tire equatorial plane CL to the tread end TE side, the tread width of the tread surface at 50% of the half width Lp of the perimeter of the tread surface 6 along the perimeter of the tread surface 6 And a circumferential groove extending in the circumferential direction of the tire in the intermediate region A, where the region in the tire width direction is an intermediate region A in the tread surface, which is also 82% apart and is interposed between the tread surface and the tire width direction position of the tread surface. 1 is formed. The circumferential groove 1 in the present embodiment is linear, but may be zigzag or curved.
Further, in the tread surface 6, two types of width direction grooves (intersection grooves) 2a and 2b are alternately formed in the tire circumferential direction X. More specifically, the widthwise groove 2a is a linear groove whose both ends are terminated in the tread surface 6, and extends in an inclined manner with respect to the tire width direction. Similarly, both ends of the width direction groove 2b terminate in the tread surface 6, but linear groove portions b1 to b3 having different inclination angles with respect to the tire width direction communicate with each other. In other words, the width direction groove 2b is bent and extended twice. It is preferable that the inclination angle with respect to the tire width direction of this width direction groove is 5 degrees or more and 25 degrees or less. The widthwise grooves 2a and 2b are grooves deeper than the circumferential groove 1 described above.

  Each of the circumferential groove 1 and the width direction grooves 2a and 2b crosses and extends. The circumferential groove 1 is adjacent to the intersection portion J in the tire circumferential direction at least one (all in the illustrated example) of the intersection portion J intersecting with the width direction grooves 2a and 2b, and the groove depth is the circumferential direction A raised bottom portion r is shallower than the other portions of the groove 1. For example, in the example of FIG. 2, although the groove depth d1 in the portion other than the bottom raising portion r of the circumferential groove 1 is 4 mm, the groove depth d2 in the bottom raising portion r of the circumferential groove 1 is 2 mm. In the present embodiment, the raised portions r are provided on both sides of the intersection portion J in the tire circumferential direction, but may be provided only on one side.

  As described above, in the tire according to the present invention, the circumferential direction groove 1 continuous in the tire circumferential direction in the intermediate region A in the reference state in which the application rim 7 is mounted, filled with the prescribed internal pressure, and not loaded. And a cross groove (in the present embodiment, width direction grooves 2a and 2b) extending in a direction intersecting with the circumferential groove 1, and the circumferential groove 1 is provided at at least one of intersections J with the cross groove. It is essential that the groove has a raised bottom portion r which is shallower than the other portions of the circumferential groove 1 adjacent to the intersection and the tire circumferential direction.

  As described above, when the circumferential groove 1 continuous in the tire circumferential direction is provided in the intermediate region A, the groove surface area of the intermediate region A near the ground contact end TE where the amount of heat generation during traveling of the vehicle is largest becomes large. The heat generated inside the tire can be expelled, and the temperature inside the tire near the ground contact end TE can be reduced. Furthermore, when the groove area in the intermediate region A increases, the volume of the rubber itself that causes heat generation is also reduced, so the temperature inside the tire in the vicinity of the ground contact TE also from the viewpoint of being able to reduce the heat generation amount itself. It is possible to lower As a result, it is possible to improve the durability of the tire by suppressing the occurrence of failures at the belt end and the ply end.

  However, at this time, in the intermediate region A, a rigid step is generated between the intersection J of the circumferential groove 1 and the width direction grooves 2a and 2b and a portion other than the intersection J, and the steering stability is lowered. There is a risk. Therefore, in the tire according to the present embodiment, at least one of the intersections J of the circumferential groove 1 is adjacent to the intersection J in the tire circumferential direction, and is a groove more than other portions of the circumferential groove 1 By providing the bottom raising portion r which is shallow in depth, the rigidity level difference is reduced and the steering stability is maintained.

  As described above, according to the configuration according to the embodiment of the present invention, the temperature inside the tire near the tread end is lowered as compared to the conventional one during high load traveling while maintaining the steering stability. Durability can be improved. In addition, according to the structure which concerns on one Embodiment of this invention so that it may describe also in the following Example, even when it is a case where the circumferential direction groove | channel 1 for thermal radiation is provided, it originates in this circumferential direction groove 1 Since the rigid step difference is sufficiently small, it is possible to suppress the occurrence of uneven wear of the tread surface and pattern noise.

In the present embodiment, the traction performance of the tire can be obtained by providing the width direction grooves 2a and 2b described above. From the viewpoint of obtaining sufficient traction performance, the groove depth of the widthwise grooves 2a and 2b is preferably 5 mm or more and 9 mm or less.
Further, in the present embodiment, the width direction grooves 2a and 2b extend to the outside in the tire width direction more than the tread ground contact end, that is, the portion of the middle region A coinciding with the outermost side in the tire width direction. Such a configuration is more preferable from the viewpoint of reducing pattern noise, but the width direction grooves 2a and 2b do not necessarily extend on both sides of the circumferential groove 1 in the tire width direction.

Further, in the tire according to the present embodiment, a value obtained by dividing the tire circumferential length L of a portion other than the raised bottom portion of the circumferential groove 1 by the pattern pitch length (not shown) in the tire circumferential direction is 0.50. It is preferable that it is 0.85 or less.
If this value is set to 0.50 or more, the heat radiation effect by the circumferential groove 1 can be further improved, and if it is set to 0.85 or less, steering stability can be more reliably maintained.
More preferably, it is 0.6 or more and 0.75 or less.

  Further, FIG. 3 shows a cross-sectional view when the crossing portion J of the circumferential groove 1 and the width direction groove 2a described in FIG. 2 is cut along the line B-B described in FIG. In the illustrated example, the raised bottom portion r is raised at a right angle to the bottom surface of the circumferential groove 1, but it may be, for example, a shape gently rising from the bottom surface of the circumferential groove 1. In this case, the region on the side of the intersection J from the start point of the ridge is taken as the bottom raising portion r.

As described above, the depth d1 of the circumferential groove 1 in the present embodiment is 4 mm, and the groove depth d2 at the raised bottom portion r is 2 mm, but the groove depth d1 is 2.5 mm or more and 8.0 mm or less The groove depth d2 is preferably 0.5 mm or more and 2.0 mm or less.
If the groove depth d1 is 2.5 mm or more and the groove depth d2 is 0.5 mm or more, a more sufficient heat dissipation effect can be obtained in the intermediate region A.
Further, when the groove depth d1 is 8.0 mm or less and the groove depth d2 is 2.0 mm or less, the rigidity of the entire tread surface 6 is increased, so that the steering stability can be more reliably maintained. Furthermore, the rigidity level difference in the intermediate region A can be made smaller, and the occurrence of uneven wear of the tread surface and pattern noise can be suppressed.

Further, in the tire according to the present embodiment, it is preferable that the negative ratio in the intermediate region A be 25% or more and 55% or less.
If it is 25% or more, a more sufficient heat dissipation effect can be obtained in the intermediate region A, and if it is 55% or less, steering stability can be more reliably maintained.
Furthermore, in the reference state, from the tire equatorial plane to both tread end sides, a predetermined area in the intermediate area A, which is 56% to 76% of the tire width direction area of the half width Lp of the periferli length of the tread surface. It is preferable that the negative rate in (not shown) is 35% or more and 80% or less.

  The above-described pneumatic tire for a motorcycle according to the present invention can be used as various motorcycle tires, but the radial tire for a motorcycle having the inclined belt described above (the cord angle of the carcass ply in the tire width direction is in the tire width direction On the other hand, it can be used particularly advantageously as a belted bias tire for motorcycles (MCS (the cord angle of the carcass ply is more than 25 ° with respect to the tire width direction)) having an inclined belt. However, the pneumatic tire for a motorcycle according to the present invention can also be used as an MCR of a mono-spiral belt structure or a normal MCS having no belt.

Examples of the present invention will be described below, but the present invention is not limited thereto.
Inventive Example tires and Comparative Example tires (both with a tire size of 180 / 60R16M / C) were produced on the basis of the specifications shown in Table 1, and the tire durability, steering stability, noise performance and uneven wear resistance were evaluated. .

  Each test tire has a carcass extending between a pair of bead portions as a frame, and is provided with a pair of side wall portions on the tire radial direction outer side of the bead portion and a tread portion extending between the side wall portions. More specifically, the present invention comprises a two-layer belt layer formed by rubber-coating an aramid cord at the tire radial direction outer side of the carcass, comprising a two-layer ply having a nylon cord, and at the tire radial direction outer side. And 1) a belt layer formed of rubber-coated nylon cords. The cord angle of the carcass ply with respect to the tire width direction is 15 °, the cord angle of each belt layer with respect to the tire circumferential direction is 15 °, and the cords of the two belt layers of aramid cord cross each other between layers There is.

Each test tire was attached to an application rim (MT 5.00-16 M / C), filled with an internal pressure of 280 kPa, and a tire loaded with STEP load was run on the test drum at a speed of 81 km.
The durability of the tire was evaluated by the load until a crack occurs in the above test.
The steering stability evaluation and the noise performance evaluation of the tire were conducted by a test drive with a professional test driver, and were performed by feeling evaluation.
The evaluation of the uneven wear resistance of the tire was evaluated by the amount of wear when traveling 2000 km.

  The results of Table 1 were indexed with the results of Comparative Example Tire 1 as 100. With regard to the durability, steering stability and noise performance of the tire, it is shown that the larger the index is, the better the performance, and for the uneven wear resistance of the tire, the smaller the index is, the better the performance is.

  1: circumferential groove, 2, 2a, 2b: width direction groove, 3: inclined belt, 3a, 3b: inclined belt layer, 5: carcass, 6: tread tread, 7: applicable rim, A: middle region, CL: Tire equator, J: intersection of circumferential groove and width direction groove, d1: groove depth in a portion other than bottom raising portion r of circumferential groove 1, d2: groove depth of bottom raising portion, r: bottom raising portion, TE: Tread end

Claims (4)

In the standard condition with the tire mounted on the applicable rim, filled with the specified internal pressure, and unloaded
From the tire equatorial plane to the tread end side, 50% of the tread width of the tread flat surface 50% apart along the perimeter of the tread flat surface of the tread flat surface, and the tread width of the tread flat surface spaced 82% as well When the tire width direction area in the tread surface sandwiched between the direction positions is an intermediate area,
The intermediate region in each of the tire half portions includes: a circumferential groove continuous in the circumferential direction of the tire; and a cross groove extending intersecting with the circumferential groove.
The circumferential groove has, at least at one of the intersections with the intersection groove, adjacent to the intersection and the circumferential direction of the tire, the groove having a raised bottom portion whose groove depth is shallower than other portions of the circumferential groove. A pneumatic tire for a motorcycle, characterized in that.   The air for a motorcycle according to claim 1, wherein a value obtained by dividing the tire circumferential length between the raised bottom portions of the circumferential groove by the pattern pitch length in the tire circumferential direction is 0.50 or more and 0.85 or less. Containing tire.   The groove depth is 2.5 mm or more and 8.0 mm or less at a portion other than the raised portion of the circumferential groove, and the groove depth at the raised portion of the circumferential groove is 0.5 mm or more and 2.0 mm or less. A pneumatic tire for a motorcycle according to item 1 or 2.   The pneumatic tire for a motorcycle according to any one of claims 1 to 3, wherein the negative rate in the intermediate region is 25% or more and 55% or less.

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