JP2000038009A - Pneumatic radial tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make applicable to a front wheel a radial tire having a belt layer cord substantially extending in a tire peripheral direction. SOLUTION: In a tire provided with a radial carcass 2 and a belt 3 formed by a belt layer cord extending substantially in a tire peripheral direction, the tire is formed by setting an elastic modulus of the belt layer cord to 300 to 4000 kgf/mm2, arrangement density in each layer of the belt layer cord to 12 to 35 codes/25 mm, arranging the belt layer cord in two layers or more in a central region of a belt width direction, setting a total number of the belt layer cords in this central region to 100 to 200, and that in each side part region to 30 to 90.

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 belt structure which is used as a tire for a front wheel to improve steering stability.

[0002]

2. Description of the Related Art A radial carcass comprising one or more carcass plies, and a belt layer cord spirally wound around the outer periphery of a crown portion of the carcass and extending substantially in the tire circumferential direction. Conventional pneumatic radial tires for motorcycles having a belt are exclusively used as rear wheel tires and exhibit excellent high-speed durability and high-speed stability.

[0003]

However, when such a pneumatic radial tire is used as it is as a tire for a front wheel, low steering stability is inevitable, and the longitudinal spring constant at the center of the tread is small. Due to the large ground contact area, the steering torque under low speed conditions increases, making it difficult to maneuver, and the tread rigidity at the time of applying the camber angle to the tire is small, generating sufficient camber thrust There is a problem that the turning performance is low because it cannot be performed.

[0004] The present invention is to solve such a problem of the conventional tire, the purpose of which is to
Air conditioning for motorcycles that is used as a front wheel tire to facilitate maneuvering under low-speed conditions and to increase camber thrust during cornering to improve cornering performance and achieve excellent steering stability. In providing radial tires.

[0005]

SUMMARY OF THE INVENTION A pneumatic radial tire for a motorcycle according to the present invention, which facilitates handling under low-speed conditions, includes a radial carcass comprising at least one carcass ply and a crown portion of the radial carcass. A belt made of, for example, a spirally arranged belt layer cord extending on the outer peripheral side and extending substantially in the tire circumferential direction, wherein the belt layer cord has an elastic modulus of 300 to 40.
00 kgf / mm ² , the arrangement density of the belt layer cords in each layer is 12 to 35 cords / 25 mm, and the belt layer cords are larger in the central area in the belt width direction than in other areas. The total number of belt layer cords in the central area is 100 to 200,
In each side area in the belt width direction, the number is 30 to 90.

Here, the central region in the belt width direction is defined as a region on both sides of the belt width center line which is 25% of the peripheral length of the belt.
Each side area means an inner area, and the side area means an area outside the central area.

According to this tire, since the number of belt layer cords extending to the central region increases, the vertical spring constant at the center of the tread increases, and the contact area decreases. Is also reduced, and the maneuverability is effectively improved. Here, if the number of extending belt layer cords is less than 100, it is difficult to sufficiently reduce the steering torque, and if it exceeds 200, the ride quality deteriorates.

Here, the number of codes in each side area is set to 3
By setting the number to 0 to 90, normal turning performance can be secured.

Further, the elastic modulus of the belt layer cord is set to 3
By setting the density of the belt layer cord to 00 to 4000 kgf / mm ² and the arrangement density of the belt layer cords to 12 to 35 cords / 25 mm, the effect of the belt in the normal range can be secured.

In the pneumatic radial tire for a motorcycle according to the present invention, the turning performance is improved. In particular, the belt layer cord is laminated and arranged in two or more layers in the side region in the belt width direction more than other regions. The tire differs from the tire in that the total number of belt layer cords in each side region is 70 to 200, and that in the central region in the belt width direction is 30 to 100.

[0011] In this tire, the large number of belt layer cords extending to the side region increases the rigidity of the tread side portion, thereby causing a large camber thrust in the tire having a camber angle. , High turning performance can be realized. Here, if the number of the belt layer cords is less than 70, the turning performance cannot be effectively increased, while if it exceeds 200, the riding comfort at the time of turning deteriorates.

Here, the number of codes in the central area is 30.
By setting the number to 100, an appropriate riding comfort can be secured.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view in the tire width direction showing one embodiment of a pneumatic radial tire for a motorcycle in which the number of belt layer cords is increased in a central region in the belt width direction.

In the drawing, reference numeral 1 denotes a pair of bead cores,
Reference numeral 2 denotes a radial carcass extending over the bead cores 1 and including one or more carcass plies. Here, the radial carcass 2 is formed of two carcass plies each composed of a cord extending at an angle within a range of 75 to 90 ° with respect to the tire circumferential direction, and the outer periphery of a crown portion of the radial carcass 2 is formed. Belt 3 on the side
And the tread 4 is further disposed on the outer peripheral side thereof.

The illustrated belt 3 is composed of two belt layers 3a and 3b located adjacent to the inside and outside in the tire radial direction. Each of these belt layers 3a, 3b can be formed, for example, by spirally winding one or a plurality of belt layer cords, whereby the belt layer cords substantially extend in the tire circumferential direction. Extend.

Here, the belt layer code is 300 to 40.
It has an elastic modulus of 00 kgf / mm ² , and its disposition density is 25 mm in each of the belt layers 3 a and 3 b.
12 to 35 lines per width.

Here, the belt layer 3a located on the inner peripheral side of the belt 3 is a wide belt layer having a long peripheral length, while the belt layer 3b located on the outer peripheral side is used.
Is located in the central region in the belt width direction, a narrow belt layer having a short peripheral length, and an arrangement area of the narrow belt layer,
That is, the central region is provided on both sides of the belt width center line c,
The wide belt layer is used as an inner region when 25% of the width W of the belt 3 is taken. The actual arrangement width of the outer peripheral side belt layer 3b can be smaller than the width W / 2 of the central area.

In this case, as described above, the belt layer has a two-layer laminated structure in the central region in the belt width direction, and has a single-layered belt layer structure in a lateral region outside the central region.
The total number of belt layer cords in the central area is 100 to 200
Book, more preferably 130 to 180, and 30 to 90, more preferably 50 to 8 in each side area.
Zero.

According to the tire configured as described above, the vertical spring constant in the tread center diagram is appropriately increased based on the selected total number of belt layer cords in the central region in the belt width direction, and the contact area is advantageously reduced. Therefore, the steering torque at low speed can be effectively reduced without deteriorating the riding comfort, and the maneuverability at low speed can be greatly improved.

FIG. 2 is a cross-sectional view in the tire width direction showing an embodiment of the other pneumatic radial tire for a motorcycle. In this embodiment, the outermost belt layer 3c of the two-layer belt 3 is shown. The tire has the same structure as that of the above-described tire in that the tire is laminated only on each side area in the belt width direction.

Here, the side area is located outside the center area.
The area of 25% of the belt width W is also referred to as the outer peripheral side belt layer 3.
It is also possible to make the actual arrangement width of c smaller. Further, here, the total number of belt layer cords in each side area is 70 to 200, more preferably 100 to 200.
160 and 30 to 10 in the central area
0, more preferably 60 to 90.

According to such a belt structure, the rigidity of the tread side portion is increased due to the total number of belt layer cords in the belt width direction side region, and the camber thrust when the camber angle is given to the tire is large. Therefore, excellent turning performance can be provided.

[0023]

EXAMPLES Example 1 The size of the front wheel tire was set to 120/70 ZR 17,
750 when the filling air pressure is 2.5 kgf / cm ² , the rear tire size is 180/55 ZR 17, and the filling air pressure is 2.9 kgf / cm ^2.
In the driving stability test with a cc actual vehicle, only the front tires had the belt structure shown in FIG. 1, the total number of belt layer cords in the central area was 148, and that in each side area was 46. The lightness of the handling at the time of low-speed handling was evaluated by feeling of the example, and the results shown in Table 1 were obtained.

In the comparative example in the table, as shown in FIG. 3, the belt is composed of one belt layer, and the arrangement density of the belt layer cords over the entire width of the belt is 30/25 mm.
It shows the case where the tire with the above is applied to the front wheel, and the larger the index value in the table, the better the result.

[0025]

[Table 1]

Example 2 Only the front tires had the belt structure shown in FIG. 2, and the above description was made except that the total number of belt layer cords in each side area was 100 and that in the central area was 74. For the same example as described above, the turning performance during actual vehicle running was evaluated by feeling, and the results shown in Table 2 were obtained. The comparative example here is the same as described above, and the evaluation method in the table is also the same as described above.

[0027]

[Table 2]

[0028]

As is apparent from the above embodiment, according to the present invention, the belt layer cord is laminated in two or more layers, particularly in the central region or the lateral region in the belt width direction. , By appropriately increasing the total number of belt layer cords in the central area or the side area from that of the other parts,
The maneuvering stability can be advantageously improved by improving the maneuverability of the vehicle in a low speed state, or by increasing the camber thrust at the time of turning to increase the turning performance.

[Brief description of the drawings]

FIG. 1 is a sectional view in the tire width direction showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view in the tire width direction showing another embodiment of the present invention.

FIG. 3 is a cross-sectional view in the tire width direction showing a comparative example tire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead core 2 Radial carcass 3 Belt 3a Inner peripheral belt layer 3b Outer peripheral belt layer 4 Tread

Claims (1)

[Claims] 1. A tire comprising: a radial carcass comprising one or more carcass plies; and a belt disposed on an outer peripheral side of a crown portion of the radial carcass and comprising a belt layer cord extending substantially in a tire circumferential direction. In the above, the elastic modulus of the belt layer cord is 300 to 4000 kgf / m.
m ² , the arrangement density of the belt layer cords in each layer is 12 to 35 cords / 25 mm, and the belt layer cords are divided into two or more layers in either the central area or the side area in the belt width direction. And in the central area, the total number of belt layer cords in the central area is 100 to 200, and that in each side area is 30 to 90, , In the layered arrangement in the side area, the number of layers of the belt layer cord in each side area 70 to 200,
A pneumatic radial tire for motorcycles having 30 to 100 tires in the central region.