JP5788217B2 - Pneumatic tires for motorcycles - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a pneumatic tire for a motorcycle (hereinafter, also simply referred to as “tire”). The present invention relates to a compatible pneumatic tire for a motorcycle.

  Today, tires for four-wheeled vehicles such as passenger cars, trucks, and buses are designed to reduce the loss of strain energy generated inside the tires while driving with the aim of improving the fuel efficiency. Measures have been taken to reduce the strain energy loss of the tread rubber. However, when the strain energy loss of the tread rubber compound is reduced, the grip performance is also lowered, and in particular, it is difficult to apply to a tire in which exercise performance is important, such as a tire for a motorcycle.

  Another technique for reducing the rolling resistance of motorcycle tires is to improve the tread pattern. For example, in Patent Document 1, three circumferential grooves, that is, a central circumferential main groove and a central circumferential sub-groove on both outer sides thereof are provided in a ground contact surface region during straight traveling, and the central circumferential main groove is formed into a groove. A technique has been proposed in which rolling resistance is reduced without deteriorating the transient characteristics from straight running to turning by using a wide groove having a width of 8 mm or more.

JP 2009-298387 A

  As described above, in order to reduce rolling resistance without impairing the steering stability, the tread rubber composition and the improvement of the tread pattern as in Patent Document 1 have been studied, but the tire structure itself has been studied. The current situation has not been examined.

  Accordingly, an object of the present invention is to provide a pneumatic tire for a motorcycle that has both higher functionality and economy than the conventional one by reducing rolling resistance without impairing steering stability from the tire structure itself. It is in.

  As a result of intensive studies on the structure of the tire in order to solve the above problems, the present inventor has found that the above problems can be solved when the curvature (crown R) of the tread surface satisfies a predetermined relationship. The invention has been completed.

That is, the motorcycle pneumatic tire of the present invention includes a tread portion formed in an annular shape, a spiral belt layer having an angle of 0 ° to 5 ° with respect to the tire circumferential direction inside the tire radial direction of the tread portion, In a pneumatic tire for a motorcycle comprising:
When the radius of curvature of the tread center portion around the tire equatorial plane of the tread portion is R1, and the radius of curvature of the tread side portions on both sides of the tread center portion is R2, R1 and R2 are represented by the following formula (1),
R1> R2 (1)
Satisfying the relationship represented by
The inflection points of R1 and R2 are present on the outer side in the tire width direction than the ground contact width during straight running,
R1 and R2 are represented by the following formula (2),
1.06 ≦ R1 / R2 ≦ 1.17 (2)
Satisfying the relationship represented by
The inflection point is 0.01 Tw to 0.20 Tw away from the end of the ground contact width when the ground contact width during straight traveling is Tw, and is used for the front of a motorcycle. It is.

  Here, the “contact width” is the contact width at the maximum load (maximum load capacity) of a single wheel in the application size described in the following standard, and the internal pressure is the application described in the following standard. The air pressure with respect to the maximum load (maximum load capacity) of a single wheel in the size, and the rim is a standard rim (or “Applied Rim” or “Recommended Rim”) in the application size described in the following standards.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the pneumatic tire for motorcycles by which rolling resistance was reduced without impairing steering stability, and which was highly compatible with functionality and economical efficiency conventionally.

1 is a cross-sectional view of a pneumatic tire for a motorcycle according to a preferred embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail.
FIG. 1 shows a sectional view of a pneumatic tire for a motorcycle according to a preferred embodiment of the present invention. As shown in the figure, a pneumatic tire for a motorcycle according to the present invention includes a bead core 1 embedded in a pair of left and right bead portions 11, a pair of sidewall portions 12 connected to the pair of bead portions 11, and both sidewall portions. And a tread portion 13 connected in a toroidal shape between the two, and at least one layer for reinforcing each portion between the bead portions 11, in the illustrated example, a carcass 2 composed of two layers of carcass plies, and an outer side in the tire radial direction Further, the reinforcing cord is spirally wound in the circumferential direction, and has a spiral belt layer 3 having an angle with respect to the tire circumferential direction of 0 ° to 5 °.

In the tire of the present invention, when the radius of curvature of the tread center portion Tc centering on the tire equatorial plane of the tread portion 13 is R1, and the radius of curvature of the tread side portion Ts on both sides of the tread center portion is R2, R1 and R2 are The following formula (1),
R1> R2 (1)
And an inflection point P between R1 and R2 is present on the outer side in the tire width direction than the ground contact width Tw during straight traveling. By setting the tire structure as described above, the rolling resistance can be reduced without reducing the steering stability. Hereinafter, the mechanism will be described in detail.

  The tire for a two-wheeled vehicle has a feature in a traveling form in which a lateral force is generated by giving a camber angle at the time of turning, and a turning force necessary for turning is ensured. Therefore, it is common to set the crown R to be smaller than that of a four-wheeled vehicle tire. Further, in a tire for a motorcycle, since the rear tire functions as a driving wheel, it is necessary to increase the ground contact width, and therefore a relatively wide tire is used. On the other hand, since the front tire requires a degree of freedom around the handle shaft as a steering wheel, a relatively narrow tire is used, and the crown R is generally set smaller than the rear tire.

  In order to respond to recent high-speed and high-powered vehicles, a compound with excellent grip performance can be used, and a high rotational direction (circumferential) rigidity and excellent grounding properties that can handle high horsepower are flexible. In order to obtain out-of-plane bending rigidity, a monospiral belt structure in which a belt is wound around a tire in a spiral shape is often employed for both a front tire and a rear tire. However, a compound having excellent grip performance tends to contradict the reduction in rolling resistance, particularly in a front tire in which the crown R is small and a large distortion occurs in the tread surface portion due to wiping. In addition, the monospiral belt structure has high rigidity in the circumferential direction, but has low rigidity in the tire width direction. Therefore, it is important to suppress deformation in the tire width direction without impairing other performance.

In order to effectively suppress the wiping in the tire width direction, it is effective to increase the crown R in the region that contacts the ground during straight traveling, but if the crown R in the center portion of the narrow front tire is increased, Naturally, the crown R of the shoulder portion becomes small, and the handling characteristics from straight running to turning run change greatly, resulting in deterioration of steering stability. Therefore, in the present invention, in order to achieve reduction in rolling resistance without impairing handling characteristics, the curvature radius R1 of the tread center portion Tc and the curvature radius R2 of the tread side portion Ts on both sides of the tread center portion are as follows.
R1> R2
In addition, the inflection point P of R1 and R2 is disposed near the end of the contact width during straight traveling and on the outer side in the tire width direction than the end of the contact width.

In the present invention, R1 and R2 are represented by the following formula (2),
1.06 ≦ R1 / R2 ≦ 1.14 (2)
It is preferable to satisfy the relationship represented by: An R1 / R2 value of less than 1.06 is not preferable because the effect of reducing rolling resistance is small. On the other hand, if the value of R1 / R2 is larger than 1.14, the handling characteristics may not be sufficiently improved, which is not preferable.

  In the present invention, the position of the inflection point P is preferably 0.01 Tw to 0.20 Tw on the outer side in the tire width direction from the end of the contact width when Tw is the contact width during straight traveling. If the position of the inflection point P is outside the above range, the effect of the present invention may not be sufficiently obtained.

  In the present invention, it is only important that the radius of curvature R1 of the tread center portion Tc and the radius of curvature R2 of the tread side portion Tc satisfy a predetermined relationship, whereby the desired effect of the present invention can be obtained. Other conditions such as the tire structure and material are not particularly limited. For example, the tread rubber of the tread center portion Tc and the tread side portion Ts is not particularly limited in the present invention, and may be the same as or different from the tread side portion. Moreover, you may provide the area | region which has a different curvature radius R3 in the tire width direction outer side of the tread side part Ts.

  In the illustrated example, a spiral belt layer 3 made of a reinforcing element having an angle of 0 ° to 5 ° with respect to the tire circumferential direction is disposed as a belt layer. ) May be arranged. The spiral belt layer 3 can be formed by covering one or a plurality of cords with rubber and winding the cord around the tread so as to be spirally wound around the tread in the tire manufacturing process. . The spiral belt layer 3 may be formed of a steel cord in addition to an organic fiber cord such as aromatic polyamide. For example, a steel cord in which a steel single wire having a diameter of 0.21 mm is twisted in a 1 × 3 type is inserted into the spiral belt layer 3. It can be formed by winding in a spiral shape at 30 pieces / 50 mm. The crossing belt layer (not shown) can be provided by, for example, reinforcing cords made of aromatic polyamide or the like crossed at ± 20 ° to 80 ° with respect to the tire circumferential direction.

  Further, for example, the tire of the present invention includes a pair of bead portions 11, a pair of sidewall portions 12 connected to the bead portions 11, and a tread portion 13 connected in a toroidal shape between the sidewall portions 12. The carcass 2 that is provided and reinforces these parts across the bead parts 11 is composed of at least one carcass ply formed by arranging relatively highly elastic textile cords in parallel with each other. The number of carcass plies may be one or two, or three or more. In the example shown in the drawing, both ends of the carcass 2 are folded and locked to the bead core 1 from the tire inner side to the outer side. Further, an inner liner is disposed on the innermost layer of the tire (not shown), and a tread pattern is appropriately formed on the surface of the tread portion 13 (not shown). The present invention is applicable not only to radial tires but also to bias tires.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Examples 1-4, Reference Examples 1-3 and Comparative Examples 1, 2>
A pneumatic tire for a motorcycle of the type shown in FIG. 1 was produced with a tire size MCR120 / 70ZR17M / C. The positions of R1, R2 and the inflection point P are as shown in Table 1 below. The test tire includes a carcass composed of two carcass plies extending across a toroid between a pair of bead cores. Here, nylon fiber was used for the carcass ply. The angle of the two carcass was 90 ° with respect to the radial direction (equatorial direction). A spiral belt layer was disposed outside the carcass in the radial direction of the tire. The spiral belt layer was formed in a so-called spiral shape in which a steel cord twisted by a 1 × 5 type steel single wire having a diameter of 0.18 mm was spirally wound in the equator direction. The spiral belt layer is a method in which a belt-like body in which a single parallel cord is embedded in a coated rubber is wound in a spiral direction along the tire equator direction in the tire rotation axis direction. Formed with.

<Rolling resistance>
Each test tire was assembled on an MT 3.50 × 17 rim, the internal pressure was 250 kPa, and rolling resistance was measured by a drum test method defined in JIS D 4234. The obtained results were evaluated by an index with the result of Comparative Example 1 as 100. The smaller this value, the smaller the rolling resistance and the better the fuel consumption. The obtained results are also shown in Table 1.

<Handling>
Each test tire was assembled on a rim of MT 3.50 × 17, and the internal pressure was set to 250 kPa, and was mounted as a front tire on a 1000 cc actual vehicle. The rear tire was a tire of tire size MCR190 / 50ZR17M / C, assembled to a rim of MT 6.00 × 17, and filled with an internal pressure of 290 kPa. Thereafter, a traveling course with a load of 300 kg, a test speed of 40 to 250 km / h, and a traveling distance of 10 km was repeatedly run at a camber angle of 0 to 50 °, and the handling was evaluated by the feeling of the evaluation rider. The obtained results are also shown in Table 1 as an index with the tire of Comparative Example 1 as 100. A larger value means higher grip and better handling. If this value is within ± 5, it is within the allowable range and may be treated as an equivalent level.

※ 変曲点が、直進走行時の接地幅の端部からＴｗの何倍離れているかを示す。

* Shows how many times Tw the inflection point is from the end of the ground contact width when running straight ahead.

  Table 1 shows that the pneumatic tire for motorcycles of the present invention can reduce rolling resistance without impairing steering stability.

1 Bead core 2 Carcass 3 Spiral belt layer 11 Bead part 12 Side wall part 13 Tread part

Claims (1)

In a pneumatic tire for a motorcycle, comprising a tread portion formed in an annular shape, and a spiral belt layer having an angle with respect to the tire circumferential direction of 0 to 5 ° inside the tire radial direction of the tread portion,
When the radius of curvature of the tread center portion around the tire equatorial plane of the tread portion is R1, and the radius of curvature of the tread side portions on both sides of the tread center portion is R2, R1 and R2 are represented by the following formula (1),
R1> R2 (1)
Satisfying the relationship represented by
The inflection points of R1 and R2 are present on the outer side in the tire width direction than the ground contact width during straight running,
R1 and R2 are represented by the following formula (2),
1.06 ≦ R1 / R2 ≦ 1.17 (2)
Satisfied in represented by the relationship,
The inflection point is 0.01 Tw to 0.20 Tw away from the end of the ground contact width when the ground contact width during straight traveling is Tw, and is used for the front of a motorcycle. Pneumatic tire for motorcycles.

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