JP3105631B2 - Pneumatic radial tires for motorcycles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire for a motorcycle, and more particularly to a pneumatic radial tire for a motorcycle having a directional inclined lug groove on a tread tread surface.

[0002]

2. Description of the Related Art Conventionally, a pneumatic radial tire for a motorcycle used on public roads, as shown in FIG. 3A, is 65% of the maximum width TW of the peripheral tread at the center of the tire 70 in the red width direction. It has been common to use the area SW up to this point. For this reason, the branch groove 76 shown in Japanese Patent Application No. 3-35237, more specifically, the branch groove 76 branched from the inclined lug groove 74 of the tread tread surface 72 in consideration of the fine drainage is also arranged in this area SW. I was

[0003]

However, due to the recent improvement in the performance of the motorcycle and the improvement of the riding technique of general riders, the area S of the tread tread 72 during running is reduced.
An area RW exceeding W has come to be used. For this reason, as shown by the imaginary line in FIG.
It has become necessary to provide a branch groove 78 to improve drainage of the region RW.

On the other hand, as shown in FIG. 3 (B), the belt structure of the pneumatic radial tire 70 for a motorcycle has a first belt ply 82 in which a belt layer 80 has a wide width, and a width smaller than the first belt ply 82. Second belt ply 84
It is composed of

[0005] This is the side end 8 of the first belt ply 82.
This is because if the 2B and the side end 84B of the second belt ply 84 are overlapped, the stress at the belt end is increased, causing a belt end separation failure.

The central region of the tread width where the first belt ply 82 and the second belt ply 84 overlap is generally up to 65% of the maximum width TW of the peripheral tread, that is, the region SW. Therefore, the first belt ply 8
A region RW where only the first belt ply 82 is formed occurs near both ends 82B of the second belt ply 2.

The cord 82 of the first belt ply 82
A is an angle θ of 10 ° to 30 ° in one direction with respect to the equator S
1 and the cord 84 of the second belt ply 84
A crosses the cord 82A of the first belt ply 82,
It is inclined at an angle θ2 of 10 ° to 30 ° symmetrically to the cord 82A of the first belt ply 82 with respect to the equator S.

Therefore, in the right region RW of FIG. 3A, the direction of the inclined lug groove 74 and the first belt ply 82
The direction of the cord 82A is the same as that of FIG.
In the left region RW of (A), the direction of the branch groove 78 and
The direction of the cord 82A of the first belt ply 82 is the same direction. Therefore, in these areas RW, the code 82
The movement in the direction of contact and separation between the points A causes an expanding force to act on the bottoms of the inclined lug grooves 74 and the branch grooves 78, so that cracks are easily generated and the life of the tire is shortened.

By the way, in the inclined lug groove, by gradually increasing the width from the center of the tread to the side of the tread and gradually reducing the depth of the groove, it is difficult for the groove bottom crack to occur on the side of the tread. Can be a trend,
In the branch groove, the tread side portion is similarly shallower in depth than the tread center portion, but the width is smaller than the width of the inclined lug groove. Is smaller than the curvature of the groove bottom, and accordingly, the groove bottom crack tends to occur more easily than the inclined lug groove.

In view of the above facts, the present invention provides a pneumatic radial for motorcycles capable of preventing the occurrence of cracks at the inclined lug grooves and branch grooves provided in a region exceeding 65% of the maximum width of the peripheral tread. The purpose is to get a tire.

[0011]

In the pneumatic radial tire for a motorcycle according to the first aspect of the present invention, at least one or more belt layers having a region where cords intersect at least between adjacent layers are formed on a tread tread surface. A pneumatic radial tire for a motorcycle, comprising: a directional inclined lug groove; and a branch groove branched in a reverse inclination direction from the inclined lug groove in a region exceeding 65% from the center of the peripheral tread width, An area where at least a pair of belt layers intersects each other in the belt layer exceeds the area where the branch groove exists.

[0012]

In the pneumatic radial tire for a motorcycle according to the present invention, the region where at least one pair of belt layers intersects with each other in the belt layer exceeds the region where the branch groove exists, so that the region where the branch groove exists is limited. There is no case where the cords at both ends of the belt layer do not intersect. Therefore, in this region, the expanding force acting on the groove bottom of the inclined lug groove and the branch groove is:
Since the size of the belt layer becomes extremely small due to the interlaced belt layers, it is possible to prevent the generation of cracks at the groove bottoms of the inclined lug grooves and the branch grooves.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a pneumatic radial tire for a motorcycle according to the present invention will be described with reference to FIGS.

As shown in FIG. 2, the pneumatic radial tire 10 for a motorcycle has a nylon cord of 1260 d / 2 inclined from the inside to the outside with respect to the bead core 14 on the rim 12 at an angle of 90 ° with respect to the equator S. The carcass layer 16 is folded back, and a belt layer 20 is disposed radially outward of the carcass layer 16 in the tread 18, that is, in the crown area.

The belt layer 20 has a first radially inner portion.
The first belt ply 22 and the second belt ply 24 are made of nylon and have a cord of 1890 d / 2.

As shown in FIG. 1B, the cord 22A of the first belt ply 22 is positioned with respect to the equator S in FIG.
To the left at an angle α1 of 10 ° to 30 °,
The cord 24A of the second belt ply 24 intersects with the cord 22A of the first belt ply 22, and is symmetrical with the cord 22A of the first belt ply 22 by 10 ° with respect to the equator S.
It is inclined at an angle α2 of ３０30 °.

As shown in FIG. 2, the tread 18 extends along the carcass contour at substantially the same thickness from the center of the crown portion to the side end position 18A which forms the maximum width of the tire around the outer periphery of the crown 16A of the carcass layer 16. .

As shown in FIG. 1A, the tread 18
A plurality of pairs of directional inclined lug grooves 27 are formed alternately extending from the tread central region near the tire equator S to the left and right tread side edges. The pair of inclined lug grooves 27 on the left and right are formed in a V-shape deviated by a half pitch with respect to the tire equator S when viewed from the rear in the rotational direction in the mounting posture to the vehicle, Angle σ1 within the range of 30 ° to 70 °
Are formed alternately.

The tread portion defined by the inclined lug grooves 27 which are alternately adjacent to each other in the circumferential direction of the tire is paired on the left and right, and a plurality of directional inclined lug grooves 29 each extending from the vicinity of the center of the tread to the side edge of the tread. Is inclined lug groove 27
Is extended along.

In a region RW exceeding 65% from the center of the peripheral tread width TW of the inclined lug groove 27, a branch groove 28 extending from the tread side edge toward the center region is branched. The angle σ2 formed by the extending direction of the branch groove 28 with respect to the tire equator S is substantially equal in the direction intersecting with the angle σ1 formed by the inclined lug groove 27 with the tire equator S.

As shown in FIG. 1B, a central region SW of the tread width where the first belt ply 22 and the second belt ply 24 overlap each other exceeds the region where the branch groove 28 exists. That is, the first belt ply 22 and the second belt ply 2
4 are stacked on each other in a region where the branch groove 28 exists.

Next, the operation of this embodiment will be described. In the pneumatic radial tire 10 for a motorcycle according to the present embodiment, a region SW where the cord 22A of the first belt ply 22 and the cord 24A of the second belt ply 24 of the belt layer 20 cross each other is as follows:
Since the position of the branch groove 28 is beyond the region where the branch groove 28 is present, the position of the branch groove 28 is a region where the cords at both end portions of the belt layer 20 do not intersect,
That is, the area does not include only the first belt ply 22.

Therefore, the expanding force acting on the groove bottoms of the inclined lug grooves 27 and 29 and the branch groove 28 existing in the area SW is extremely small due to the intersecting first belt ply 22 and second belt ply 24. In addition, the generation of cracks at the bottom of the inclined lug grooves 27 and 29 and the branch grooves 28 can be prevented.

In this embodiment, the first belt ply 2
2 and the both ends of the second belt ply 24 were shifted. For this reason, it is possible to prevent the belt end stress from increasing at the side end of the belt layer 20, and to prevent the occurrence of belt end separation.

In this embodiment, the belt layer 20 is formed of the first layer.
Although the case of a pair of the belt ply 22 and the first belt ply 24 has been described, the number of the belt layers may be more than one. (Test Example) The tire of the embodiment shown in FIGS. 1A and 1B and the tire of the conventional example shown in FIGS. 3A and 3B were prototyped according to the specifications in Table 1. The size of each tire is MCR
120 / 60R17), a tire durability test was performed by the following method.

A drum having an outer diameter of 1.2 m and an inner pressure of 2.25 kg
The vehicle is driven at a speed of 50 km / H at a speed of 50 km / cm ² until a crack occurs at the bottom of the groove.

The maximum value of the strain at the bottom of the inclined lug grooves and branch grooves of each tire was measured. The results are shown in Table 1.

[0028]

[Table 1]

From the test results shown in Table 1, it was found that the tire of the present invention was particularly superior to the conventional tire.

[0030]

Since the pneumatic radial tire for a motorcycle according to the present invention has the above-described structure, generation of cracks at the inclined lug grooves and the branch grooves formed in the region exceeding 65% of the maximum width of the peripheral tread is prevented. It has an excellent effect that it can be prevented.

[Brief description of the drawings]

1A is a plan view showing a tread tread structure of a pneumatic radial tire for a motorcycle according to an embodiment of the present invention, and FIG. 1B is a pneumatic radial for a motorcycle according to an embodiment of the present invention. It is a top view showing the belt structure of a tire.

FIG. 2 is a sectional view showing an upper half of a pneumatic radial tire for a motorcycle according to one embodiment of the present invention.

FIG. 3A is a plan view showing a tread tread structure of a conventional pneumatic radial tire for a motorcycle,
(B) is a plan view showing a belt structure of a conventional pneumatic radial tire for a motorcycle.

[Explanation of symbols]

 Reference Signs List 10 Pneumatic radial tire for motorcycle 18 Tread 20 Belt layer 22 First belt ply 22A cord 24 Second belt ply 24A cord 27 Inclined lug groove 28 Branch groove 29 Inclined lug groove

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification symbol FI B60C 11/117 B60C 11/08 A (58) Investigated field (Int.Cl. ⁷ , DB name) B60C 9/00-9 / 20 B60C 11/04-11/08 B60C 11/117

Claims (1)

(57) [Claims] 1. A pair of belt layers having at least a region where cords intersect at least between adjacent layers, a directional inclined lug groove formed on a tread tread surface, and a region exceeding 65% from the center of the peripheral tread width. A pneumatic radial tire for a motorcycle, comprising: a branch groove branched in a reverse inclination direction from the inclined lug groove, wherein an area where at least one pair of belt layers of the belt layers intersects each other. A pneumatic radial tire for a motorcycle, wherein the pneumatic radial tire extends beyond a region where a branch groove exists.