JP2017030565A - Pneumatic tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability while maintaining steering stability of a tire.SOLUTION: In a reference state, when a region in a tire width direction in a step face of a tread, sandwiched between a position in the tire width direction of the step face of the tread separated by 50% of a half width of a periphery length of the step face of the tread along the periphery of the step face of the tread from a tire equator surface toward an end of the tread and a position in the tire width direction of the step face of the tread separated by 82% of the half width, is set as an intermediate region A, the intermediate region A in each half part of a tire is provided with a circumferential groove 1 continuing in a tire circumference direction and a crossing groove extending to cross the circumferential groove 1. At least one of crossing portions J crossing the crossing groove of the circumferential groove 1 has a raised part r which is adjacent in the tire circumference direction to the crossing portions J and smaller in a groove depth than the other part of the circumferential groove.SELECTED DRAWING: Figure 2

Description

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

  Conventionally, in pneumatic tires for motorcycles, particularly in running under a relatively high load, deterioration of tire durability due to damage at the belt end or ply end has been a problem. It was.

  The inventor found that the cause of the damage such as the belt end and the ply end is that the temperature inside the tire near the ground contact end of the tire becomes high during traveling, and that the heat release in such a portion is promoted. It 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 radiating groove in the vicinity of the ground contact end to lower the temperature inside the tire near the ground contact end. However, if a groove is provided near the ground contact end, the steering stability of the tire may be impaired.

  Accordingly, an object of the present invention is to provide a pneumatic tire for a motorcycle that has improved durability while maintaining the steering stability of the tire.

The configuration of the present invention is as follows.
(1) The pneumatic tire for a motorcycle according to the present invention has a tire mounted on an applicable rim, filled with a specified internal pressure, and in a reference state in which no load is applied, from the tire equator surface to the tread end side, to the tread tread surface periphery. Along the tire width direction of the tread tread sandwiched between the tire width direction position of the tread tread and the tire width direction position of the tread tread that is also 82% apart. When the region is an intermediate region, the intermediate region in each of the tire halves includes a circumferential groove continuous in the tire circumferential direction, and a cross groove extending across the circumferential groove, and the circumferential groove Is characterized in that at least one of the intersecting portions with the intersecting groove has a bottom raised portion adjacent to the intersecting portion in the tire circumferential direction and having a groove depth shallower than other portions of the circumferential groove. To.

  According to the pneumatic tire for a motorcycle of the present invention having such a configuration, the durability can be improved while maintaining the steering stability of the tire.

The “applicable rim” is an industrial standard that is valid for the region where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) JATMA YEAR BOOK, in Europe ETRTO (The European Tire) and Rim Technical Organization, Inc.) STANDARDS MANUAL, and in the United States, TRA (The Tire and Rim Association, Inc.) YEAR BOOK, etc., standard rims for applicable sizes (ETRTO STANDARDS MANUAL, Measuring Rim, TRA "YEAR BOOK" refers to Design Rim).
The “specified internal pressure” refers to the air pressure corresponding to the maximum load capacity in the applicable size and plating described in the above JATMA YEAR BOOK, etc. The “maximum load capacity” refers to the tire according to the above standards. The maximum mass allowed to be loaded.

The “groove depth” in the present invention refers to the position of the groove opening to the tread tread in a state where the tire is mounted on the applied rim, filled with the specified internal pressure, and is unloaded (hereinafter referred to as “reference state”). Up to the maximum depth position shall be measured parallel to the tire radial direction.
In addition, the “circumferential groove continuous in the tire circumferential direction” may not extend continuously in the intermediate region, but may partially extend outside the intermediate region.

(2) In the pneumatic tire for a motorcycle of the present invention, a value obtained by dividing the tire circumferential length of a portion other than the raised portion of the circumferential groove by the pattern pitch length in the tire circumferential direction is 0.50 or more and 0 .85 or less is preferable.
According to this configuration, it is possible to further improve the heat dissipation 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 unit changes in the tire circumferential direction, It shall mean the average length.

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

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

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

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

Hereinafter, a pneumatic tire for a motorcycle (hereinafter, also simply referred to as “tire”) of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a cross section in the tire width direction 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, a pair of sidewall portions 12 on the outer side in the tire radial direction of the bead portions 11, and a tread portion 13 straddling between the sidewall portions 12. It has. In addition, although the carcass in this embodiment consists of one layer of plies, two or more layers of plies can also be arranged. In the present embodiment, the inclined belt 3 including the two inclined belt layers 3a and 3b is disposed on the outer side in the tire radial direction of the carcass 5 in the tread portion 13. However, another belt structure may be used. . In the two inclined belt layers 3a and 3b, the respective cords are inclined with respect to the tire circumferential direction and extend so as to intersect each other.

  FIG. 2 shows a developed portion of the tread surface 6 of the tire according to the present embodiment. In the present embodiment, patterns that are line-symmetric with respect to the equator plane CL are arranged on the one side and the other side of the tread tread 6 with the tire equator plane CL as a boundary, and are shifted from each other in the tire circumferential direction X. ing. Therefore, the configuration of the tread tread 6 of this embodiment will be described as a representative of the left half of the tire toward the paper.

First, in this embodiment, the tire width direction position of the tread tread that is 50% apart from the tire equatorial plane CL toward the tread end TE side along the periphery of the tread tread 6 along the half width Lp of the peripheral length of the tread tread 6. Similarly, when the tire width direction region of the tread tread that is 82% apart and sandwiched between the tread treads in the tire width direction is the intermediate region A, the circumferential groove that is continuous in the tire circumferential direction is the intermediate region A. 1 is formed. Although the circumferential groove 1 in this embodiment is linear, it can also be zigzag or curved.
In addition, two types of width direction grooves (intersection grooves) 2 a and 2 b are alternately formed on the tread surface 6 over the tire circumferential direction X. More specifically, the width direction groove 2a is a linear groove whose both ends are terminated in the tread surface 6, and extends inclining with respect to the tire width direction. Similarly, both ends of the width direction groove 2b terminate in the tread surface 6, but linear grooves b1 to b3 having different inclination angles with respect to the tire width direction are configured to communicate with each other. In other words, the width direction groove 2b is bent and extended twice. The inclination angle of the width direction groove with respect to the tire width direction is preferably 5 ° or more and 25 ° or less. The width direction grooves 2a and 2b are grooves whose depth is deeper than that of the circumferential groove 1 described above.

  Each of the circumferential groove 1 and the width direction grooves 2a and 2b extends so as to cross each other. The circumferential groove 1 is adjacent to the intersecting portion J in the tire circumferential direction at at least one (all in the illustrated example) of the intersecting portion J intersecting with the widthwise grooves 2a and 2b, and has a groove depth in the circumferential direction. The bottom raised portion r is shallower than other portions of the groove 1. For example, in the example of FIG. 2, the groove depth d1 in the portion other than the raised bottom portion r of the circumferential groove 1 is 4 mm, but the groove depth d2 in the raised 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 intersecting portion J in the tire circumferential direction, but may be provided only on one side.

  Thus, in the tire according to the present invention, in the reference state that is mounted on the application rim 7, filled with the specified internal pressure, and in the no-load state, the circumferential groove 1 that is continuous in the tire circumferential direction in the intermediate region A, Crossing grooves (in this embodiment, width direction grooves 2a and 2b) extending across the circumferential groove 1, and the circumferential groove 1 is provided at at least one of intersections J with the crossing groove, It is essential that the groove depth has a bottom raised portion r adjacent to the intersecting portion in the tire circumferential direction and having a shallower groove depth than other portions of the circumferential groove 1.

  As described above, when the circumferential groove 1 that is continuous in the tire circumferential direction is provided in the intermediate region A, the groove surface area of the intermediate region A that is near the ground contact TE and has the largest amount of heat generated during vehicle travel is increased. The release of heat generated inside the tire can be promoted, and the temperature inside the tire in the vicinity of the ground contact end TE can be lowered. Furthermore, if the groove area in the intermediate region A is increased, the volume of the rubber itself that causes heat generation is also reduced. Therefore, from the viewpoint of reducing the heat generation amount itself, the temperature inside the tire in the vicinity of the ground contact TE is also reduced. Can be reduced. As a result, the occurrence of failure at the belt end and the ply end can be suppressed, and the durability of the tire can be improved.

  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 grooves 2a and 2b and a portion other than the intersection J, and steering stability is reduced. There is a fear. Therefore, in the tire according to the present embodiment, at least one of the intersecting portions J of the circumferential groove 1 is adjacent to the intersecting portion J in the tire circumferential direction and is grooved more than other portions of the circumferential groove 1. By providing the bottom raised portion r having a shallow depth, the rigidity step is reduced and the steering stability is maintained.

  As described above, according to the configuration of the embodiment of the present invention, the temperature inside the tire near the tread end during high-load traveling is reduced as compared with the conventional tire while maintaining steering stability. The durability of can be improved. As described in the following examples, according to the configuration of the embodiment of the present invention, even when the circumferential groove 1 for heat dissipation is provided, the circumferential groove 1 is caused. Since the rigidity level difference is sufficiently small, it is possible to suppress uneven wear on the tread surface and generation of pattern noise.

In the present embodiment, the traction performance of the tire can be obtained by providing the width direction grooves 2a and 2b. From the viewpoint of obtaining sufficient traction performance, the groove depths of the width direction grooves 2a and 2b are 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 outer side in the tire width direction from the tread grounding end, that is, the portion of the intermediate region A that coincides 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 need to extend on both sides of the circumferential groove 1 in the tire width direction.

In the tire according to the present embodiment, the value obtained by dividing the tire circumferential length L of the portion other than the raised 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 0.50 or more, the heat dissipation effect by the circumferential groove 1 can be further improved, and if it is 0.85 or less, steering stability can be more reliably maintained.
More preferably, it is 0.6 or more and 0.75 or less.

  3 shows a cross-sectional view of the intersection J between the circumferential groove 1 and the width direction groove 2a shown in FIG. 2 cut along the line BB shown in FIG. In the illustrated example, the bottom raised portion r is raised at a right angle with respect to the bottom surface of the circumferential groove 1, but may be a shape that gently rises from the bottom surface of the circumferential groove 1, for example. In this case, the region on the side of the intersection J from the starting point of the ridge is defined as a bottom raised 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 in the bottom raised portion r is 2 mm, but the groove depth d1 is 2.5 mm or more and 8.0 mm or less. And the groove depth d2 is preferably 0.5 mm or more and 2.0 mm or less.
If the groove depth d1 is set to 2.5 mm or more and the groove depth d2 is set to 0.5 mm or more, a more sufficient heat dissipation effect can be obtained in the intermediate region A.
Further, if the groove depth d1 is set to 8.0 mm or less and the groove depth d2 is set to 2.0 mm or less, the rigidity of the entire tread 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 further reduced, and the occurrence of uneven wear on the tread surface and pattern noise can be suppressed.

In the tire according to this embodiment, the negative rate in the intermediate region A is preferably 25% or more and 55% or less.
If it is 25% or more, a 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.
Further, in the reference state, from the tire equatorial plane to both tread end sides, a predetermined region in the intermediate region A that is a tire width direction region of 56% to 76% of the half width Lp of the peripheral length of the tread tread surface (see FIG. The negative rate in (not shown) is preferably 35% or more and 80% or less.

  The above-described pneumatic tire for motorcycles of the present invention can be used as various types of motorcycle tires. However, the motorcycle radial tire (MCR (carcass ply cord angle is in the tire width direction) having the inclined belt described above can be used. And a belted bias tire for motorcycles having an inclined belt (MCS (carcass ply cord angle is more than 25 ° with respect to the tire width direction)). However, the pneumatic tire for motorcycles of the present invention can also be used as an MCR having a monospiral 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.
Invention example tires and comparative example tires (both tire sizes are 180 / 60R16M / C) were prototyped under the specifications shown in Table 1, and the durability, steering stability, noise performance and uneven wear resistance of the tires were evaluated. .

  Each test tire has a carcass straddling between a pair of bead portions as a skeleton, and includes a pair of sidewall portions on the outer side in the tire radial direction of the bead portions, and a tread portion straddling the sidewall portions. More specifically, a carcass made of two layers of plies having nylon cords is provided, and two belt layers formed by rubber coating aramid cords on the outer side in the tire radial direction of the carcass, and on the outer side in the tire radial direction. A belt layer made of rubber coated nylon cord. 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 made of aramid cords cross each other between the layers. Yes.

Each test tire was assembled to an applicable rim (MT5.00-16 M / C), filled with an internal pressure of 280 kPa, and loaded with a STEP load, and run on a test drum at a speed of 81 km / h.
The durability of the tire was evaluated by the load until cracks occurred in the above test.
Tire driving stability evaluation and noise performance evaluation were performed by a test run with a professional test driver and feeling evaluation.
The evaluation of uneven wear resistance of the tire was evaluated by the amount of wear during running at 2000 km.

  The results in Table 1 are indicated by an index with each result of Comparative Example Tire 1 being 100. As for the durability, steering stability and noise performance of the tire, the larger the index, the better the performance. As for the uneven wear resistance of the tire, the smaller the index, the better the performance.

  1: circumferential groove, 2, 2a, 2b: width groove, 3: inclined belt, 3a, 3b: inclined belt layer, 5: carcass, 6: tread surface, 7: applied rim, A: intermediate region, CL: Tire equator, J: intersection of circumferential groove and width groove, d1: groove depth in a portion other than the raised portion r of circumferential groove 1, d2: groove depth of the raised portion, r: raised portion, TE: Tread edge

Claims (4)

In the standard state where the tire is attached to the applicable rim, filled with the specified internal pressure, and no load is applied,
From the tire equator surface to the tread edge side, along the periphery of the tread surface, the tire width of the tread surface that is spaced by 50% of the half width of the peripheral length of the tread surface and the tire width direction position of the tread surface that is also 82% apart When the region in the tire width direction on the tread surface sandwiched between the direction position is the intermediate region,
The intermediate region in each of the tire halves includes a circumferential groove continuous in the tire circumferential direction, and an intersecting groove extending across the circumferential groove,
The circumferential groove has, at least one of the intersecting portions with the intersecting groove, adjacent to the intersecting portion in the tire circumferential direction and a bottom raised portion whose groove depth is shallower than other portions of the circumferential groove. This is a pneumatic tire for motorcycles.   2. The motorcycle air according to claim 1, wherein a value obtained by dividing a tire circumferential length between bottom raised portions of the circumferential groove by a pattern pitch length in the tire circumferential direction is 0.50 or more and 0.85 or less. Tires.   The groove depth in a portion other than the raised portion of the circumferential groove is 2.5 mm or more and 8.0 mm or less, and the groove depth in the raised portion of the circumferential groove is 0.5 mm or more and 2.0 mm or less. Item 3. 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 a negative rate in the intermediate region is 25% or more and 55% or less.

Images