JPH10109507A - Tyre for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase rigidity near a tread end edge and also improve a turning transitional characteristic by the linear deformation of a side wall part in response to a load and improve the limit running performance of turning. SOLUTION: In the type meridian section in a standard state rimed a type to a normal rim and filled a normal inner pressure, the outer surface 3S of a side wall part from the separation point P1 at which the outer surface of a bead part starts to separate from the flange Rf of the normal rim upto the end edge Te of a tread part is form end in nearly straight line shape in which the maximum dislocation amount X in an orthogonally crossing direction with this straight line K from the straight line K with a length Ls connecting the separation point P1 with the end edge Te of the tread part is 0.05 times of the length Ls or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire for a motorcycle capable of increasing rigidity in the vicinity of an edge of a tread and, in particular, greatly improving a cornering performance in turning.

[0002]

2. Description of the Related Art With the improvement of the expressway network and the performance of vehicles, the transition to a radial structure which is excellent in high-speed running performance is being promoted even for motorcycle tires. In order to improve ride comfort in a tire having a structure, a parallel cord ply in which a cord is spirally wound substantially parallel to the tire equator is used as a belt layer instead of a conventional belt in which cords cross each other between plies. Is being done.

[0003] Since this is provided with flexibility such as a reduction in bending rigidity of the tread portion inward in the radial direction,
On the other hand, the camber thrust and the cornering force generated at the time of turning become too small, and the turning performance tends to be impaired.

[0004]

SUMMARY OF THE INVENTION Accordingly, Japanese Patent Application Laid-Open No. Hei.
As shown in FIG. 4, a cord reinforcing layer b is provided on the outside of the belt layer a and on the tread shoulder portion with the aim of improving the turning performance while maintaining the riding comfort when traveling straight, as shown in FIG. It has been proposed to provide.

However, such a cord reinforcing layer b
Even in the case where the tread edge te is provided, the rigidity at the tread edge te is insufficient, and the tread edge te is not sufficiently rigid. There is a problem that can not be obtained.

[0006] As a result of the study by the present inventors, it has been found that the limit traveling performance of the turning greatly affects the contour of the outer surface of the sidewall portion. That is, as shown in FIG. 4, the conventional contour shape has a side wall portion outer surface c with respect to a straight line k connecting the separation point p at which the bead portion starts to separate from the rim flange and the tread edge te. The upper part c1 is bent in a concave shape and the lower part c2 is curved in a substantially S-shape protruding. For this reason, the side wall portion is liable to cause an accordion-like bending deformation due to the load from the road surface, the rigidity near the tread edge te is impaired, and the side force decreases as the camber angle approaches the limit, causing only the stiffness to occur. It is presumed.

Therefore, the present invention is based on the fact that the outer surface of a sidewall portion extending from a separation point P1 from a rim flange to an edge Te of a tread portion is formed substantially in a straight line. It is an object of the present invention to provide a motorcycle tire capable of improving turning transient characteristics by linearly deforming a sidewall portion according to a load and greatly improving turning performance at a limit of turning.

[0008]

In order to achieve the above object, in the motorcycle tire of the present invention, the tread width, which is the distance between the edges Te of the tread portion in the tire axial direction, forms the maximum width of the tire. And a motorcycle tire having a carcass whose tread surface has a convex arc shape and which is turned around the bead core of the bead portion through the sidewall portion from the tread portion, and assembling the tire with a regular rim, In the tire meridional section in the standard state filled with the normal internal pressure, the outer surface of the sidewall portion from the separation point P1 at which the outer surface of the bead portion starts to separate from the flange of the normal rim to the end edge Te of the tread portion is the distance Point P
It is assumed that the maximum deviation X in the direction perpendicular to this straight line from the straight line of length Ls connecting 1 to the edge Te of the tread portion is substantially linear not more than 0.05 times the length Ls. It is a characteristic.

The maximum displacement X is determined by the length Ls
It is more preferably 0.02 times or less.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a motorcycle tire 1 is, in this example, a radial tire for a rear wheel of a large vehicle, a tread portion 2 having a tread surface 2S smoothly curved in a convex arc shape, and both end edges Te ( A sidewall portion 3 extending inward in the tire radial direction from a tread edge Te), and a bead portion 4 located at a radially inner end of each sidewall portion 3 in the tire radial direction. The tread width TW, which is the distance between Te in the tire axial direction, is formed to be the maximum width of the tire. Further, the motorcycle tire 1 is provided with a carcass 6 bridged between the bead portions 4, and a band layer 7 disposed radially outside the carcass 6 and inside the tread portion 2. .

FIG. 1 shows JATMA, TRA, ETR
FIG. 4 shows a meridional section of a tire in a standard state where the tire is assembled to a regular rim R defined by a tire standard such as TO and filled with a regular internal pressure.

The carcass 6 has, at both ends of a main body portion extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3, folded portions for turning around the bead core 5 from the inside in the tire axial direction to the outside. The space between the main body and the folded portion is filled with a bead apex rubber 8 having a triangular cross section and extending outward from the bead core 5 in the tire radial direction.

The carcass 6 has carcass cords arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction.
Formed from one or more carcass plies in this example,
The folded portion of the carcass ply has a high turn-up configuration in which the carcass ply is wound up to the vicinity of the tread edge Te, thereby increasing the tire lateral rigidity together with the bead apex rubber 8.

The band layer 7 is formed by spirally winding a band cord at an angle of 5 degrees or less with respect to the tire circumferential direction.
In the present embodiment, the band cord is formed into a band-shaped small-width ply in which one or a plurality of the band cords are arranged and spirally wound. The band ply is formed by continuously winding the small width ply from one tread edge Te to the other tread edge Te. For example, two small width plies are used. The ply may be wound from the vicinity of the tire equator C toward the tread edges Te on both sides, or from the tread edges Te on both sides toward the tire equator C.

The band layer 7 preferably has a band width BW in the tire axial direction of 0.7 to 1.0 times the tread width TW, whereby the tread portion 2 having a small radius of curvature is curved. Of the tire is tightened with uniform tension, and in this example, the tire flatness is restricted to 60% or less.

In the meridional section of the tire in the standard state, the tread surface 2S has a radius of curvature Cr of 0.3 to 0.8 times the tread width TW in the center region Y1 where the tire touches the ground during straight running. On the other hand, in the shoulder region Y2 extending from the central region Y1 to the tread edge Te, the tread width TW is 0.4 to less than 0.4.
It is formed by an arc having a curvature radius Sr of 1.0 times. In order to increase the contact area with the increase of the camber angle at the time of turning, and to enhance the stability at the time of turning, it is preferable to satisfy Sr> Cr.
/Cr≧1.2 is preferable. Further, in the shoulder region Y2, the radius of curvature is preferably formed in a series of convex arcs in which the radius of curvature is increased continuously or stepwise outward in the tire axial direction.

The radii of curvature Cr and Sr are defined as a curvature passing through a total of three points, that is, both end points of the area and a point on the tread surface at the axial center of the both end points. Table 1
All the tires inside are Cr = 90mm, Sr = 120mm, S
r / Cr = 1.2.

The outer surface of the bead portion 4 is formed on the regular rim R
The outer surface 3S of the sidewall portion 3 from the separation point P1 at which separation from the flange Rf starts, to the tread edge Te.
Are formed substantially linearly. The outer surface 3S is a substantial profile surface of the side wall portion 3, for example, a pattern of characters, symbols, etc. formed on the side wall portion 3, a rim protector line, and an air release for vulcanization. Local irregularities due to vent lines (convex lines) and the like are excluded.

As described above, the outer surface 3S of the sidewall portion
Is formed substantially in a straight line, the load applied from the road surface during the cornering of the turn causes the sidewall portion 3 to be deformed in the compression direction, and the rigidity near the tread edge Te is reduced by the rigidity of the entire sidewall portion 3. And raise it. Thereby, as the camber angle at the time of turning approaches the limit, the side force also increases, and it is possible to suppress the occurrence of the waist. In addition, since the sidewall portion 3 is linearly deformed according to the load, good transient characteristics during turning can be obtained,
Excellent turning performance with high steering stability can be exhibited. When the vehicle is traveling straight, the load applied from the road surface deforms the side wall portion 3 in the bending direction, which contributes to improvement in ride comfort such as flexibility. Such an effect is most remarkably exhibited particularly in a radial structure having a small tire lateral rigidity with a carcass cord angle of 85 to 90 degrees.

Here, "substantially linear" means, as shown in FIG. 2, the maximum of the direction orthogonal to the straight line K from the straight line K of the length Ls connecting the separation point P1 and the tread edge Te. Is less than or equal to 0.05 times the length Ls. Therefore, the maximum displacement amount X is equal to the length Ls.
If the range is not more than 05 times, for example, as shown by a dashed line in FIG. The arc-shaped curves M1 and M2 may be curved and protrude to either one. At this time, it is preferable that the height position where the displacement amount X is the maximum is substantially at the center of the outer surface 3S in terms of rigidity.

It should be noted that the deviation X is equal to the inner side of the tire (-
On the other hand, when the length Ls exceeds 0.05 times the length Ls, the effect of improving the turning performance cannot be sufficiently achieved.
It is better to be less than twice. On the other hand, if the length Ls exceeds 0.05 times the length Ls on the outer side (+ side) of the tire, the effect of improving the turning performance cannot be expected any more. Are easily damaged by curbs and the like, and the durability is reduced. Therefore, 0.0
It is better to be twice or less.

As shown in FIGS. 3A to 3D, the side wall portion outer surface 3S is formed by combining an arcuate curved portion n1 protruding to one of the plus side and the minus side and a straight line portion n2 along the straight line K. Composite curves M3 to M6, or a composite curve combining different curvature portions. Also in this case, although the turning transient characteristic is slightly inferior to the arc-shaped curves M1 and M2, the tread edge T
There is an effect of increasing the rigidity in the vicinity of e, and the turning performance can be improved. Note that it is preferable to have a straight portion as much as possible in terms of increasing rigidity and weight, and in the case of FIGS. 3A to 3D, the length L of the curved portion n1 and the straight portion n2 is used.
The ratio of L1 and L2 is preferably such that the ratio L1 / L2 is 0.4 to 0.6, and the maximum deviation X is the length L of the curve portion n1.
It is 0.05 times or less of 1 and 0.01 times or less.
It is preferable in terms of increasing rigidity and weight.

The angle α between the straight line K and the tire radial line LK is preferably 10 to 30 °, more preferably 15 to 25 °. If the angle α is larger than 30 °, the rigidity of the sidewall portion at the time of running at the limit becomes insufficient, and the user is likely to be only stiff. In order to reduce the angle α while maintaining the tire width (tread width) required for each tire size and the curvature of the tread surface required for tire performance, the lower part of the sidewall portion 3 is required. Will be increased. From the viewpoint of weight, the angle α is preferably less than the specified value. Note that the angle α of the example tire in Table 1 is 20 degrees.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire having the structure shown in FIG.
5R17 tires were prototyped based on the specifications in Table 1, and each test tire was manufactured using a large motorcycle (75) under the conditions of a regular rim 17 × MT5.50 and a regular internal pressure of 250 kpa.
(0 cc), mounted on the rear wheel and traveled on a real vehicle. The limit performance of turning, the transient characteristics during turning, and the sidewall damage resistance were measured and compared with the tire of the comparative example. As the tires mounted on the front wheels, conventional tires having the specifications shown in Table 2 were used.

The turning performance was evaluated by the driver's sensory evaluation of the driving stability and the height of the limiting speed when the vehicle was running on a dry pavement and the turning was at the limit. The evaluation was performed using a 10-point method in which 5 points were determined as a passing reference level, and the higher the score, the better the performance.

The turning transient characteristic is as follows on a dry pavement road surface.
The transient characteristics when turning while increasing the speed from low to high were sensory evaluated by the driver. Evaluation is 5
Using a 10-point method in which the points were determined as acceptance criteria levels, the higher the score, the better the performance.

The damage resistance of the side wall is as follows.
After traveling on 00 km and on a dirt road surface of 200 km, cut flaws generated on the outer surface of the side wall portion were visually evaluated. In the table, ○ indicates that the maximum cut length is 2 mm or less,
Δ indicates that the maximum cut length is greater than 2 mm and less than 5 mm, and X indicates that the maximum cut length is 5 mm or more.

[0028]

[Table 1]

[0029]

[Table 2]

As shown in Table 1, in the tire of the example product, the stiffness near the tread edge is appropriately increased.
While improving the turning performance without the occurrence of stiffness, etc.,
Since the deformation at the sidewall portion occurs linearly with respect to the load, good turning transient characteristics can be obtained. In addition, damage due to curbs and the like hardly occurs, and durability can be improved.

[0031]

Since the present invention is configured as described above,
Especially while increasing the rigidity near the tread edge,
Transient turning characteristics can be improved by the linear deformation of the side wall portion according to the load, and the critical running performance of turning can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire showing one embodiment of the present invention.

FIG. 2 is an enlarged diagram showing a contour shape of an outer surface of the sidewall portion.

FIGS. 3A to 3D are diagrams illustrating other examples of the contour shape of the outer surface of the sidewall portion.

FIG. 4 is a diagram showing an example of a contour shape of an outer surface of a sidewall portion of a conventional tire.

[Explanation of symbols]

 2 Tread part 2S Tread surface 3 Side wall part 3S Outer surface of side wall part 4 Bead part 5 Bead core 6 Carcass K Straight line R Regular rim Rf Flange WT Tread width

Claims (2)

[Claims] The tread width, which is the distance between the edges Te of the tread portion in the tire axial direction, forms the maximum width of the tire, the tread surface has a convex arc shape, and the bead passes from the tread portion to the side wall portion. A motorcycle tire having a carcass turned around a bead core of a portion, wherein the tire has a regular rim assembled and filled with a normal internal pressure, and in a tire meridional section in a standard state, the outer surface of the bead portion has the regular shape. Separation point P that begins to separate from the rim flange
The outer surface of the sidewall portion from 1 to the edge Te of the tread portion has a maximum deviation amount in a direction orthogonal to the straight line having a length Ls connecting the separation point P1 and the edge Te of the tread portion. X is a substantially linear shape having a length of 0.05 times or less the length Ls. 2. The motorcycle tire according to claim 1, wherein the maximum displacement X is equal to or less than 0.02 times the length Ls.