JP3515499B2 - Radial tires for motorcycles - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a radial tire for a motorcycle having improved durability.

[0002]

2. Description of the Related Art Tires for motorcycles have stable running performance,
70 to 90 with respect to the tire equatorial plane due to grip performance, etc.
A radial type carcass having a carcass cord of organic fibers arranged at an angle of ° and a belt layer using an organic fiber cord or a metal cord on the outer side in the tire radial direction has been widely used in recent years. .

The belt cord of the belt layer has a high modulus cord and imparts a necessary effect to the radial tire, and is arranged at a relatively small angle with respect to the tire equatorial plane.

On the other hand, a motorcycle is different from a four-wheeled vehicle in that the vehicle body is tilted in the direction of the turning center when turning, and cornering force is generated to turn the vehicle. Therefore, the tread surface is the tread surface of a tire for a four-wheeled vehicle. In comparison, the tread width, which has a large curvature and is the length in the tire axial direction between the tread edges, is set to be considerably larger than the normal carcass maximum width, and therefore the tread width becomes the maximum width of the tire. Note that the tread edge is configured to be located at a height that is approximately ½ of the tire cross-sectional height.

For this reason, the deformation of the belt layer is larger than that of the tire for a four-wheeled vehicle under traveling conditions in which the center of contact with the ground greatly moves during straight running and when the vehicle turns, and left and right cornering are repeated. As described above, due to the fact that a belt cord having a relatively high modulus is used as the belt cord of the belt layer which gives the tire effect as a radial tire, the adhesion between the belt cord and the rubber in the belt layer is broken. The belt end is peeled off (BEL) because it often occurs near the end of the belt cord.
It is called.

In order to prevent this belt end separation, Japanese Unexamined Patent Publication No. 5-246210 discloses a motorcycle radial having a belt having no cord end formed by spirally winding a belt-shaped cord layer in the tire circumferential direction. A tire has been proposed, and this tire has been put into practical use.

However, although it is required that the driving performance of the motorcycle be improved and the steering stability performance be further improved, the belt cord is not parallel to the tire equatorial plane even though the proposed belt layer has no cord end. Since the in-plane bending rigidity of the belt ply is low and the drag force in the tire axial direction is small, the steering stability performance cannot be improved.

It has also been proposed to provide a reinforcing layer on the outer side of the sidewall portion to increase the rigidity of the sidewall portion to compensate for the insufficient rigidity of the belt layer.

[0009]

However, in this structure, the entire sidewall portion loses elasticity due to the reinforcing layer, the handling performance, and hence the steering stability, cannot be greatly improved, and the riding comfort is poor.

As described above, as a result of the examination, regarding steering stability, two or more belt plies having belt cords tilted at a constant angle with respect to the tire equatorial plane are arranged so that the cords cross each other. Turned out to be excellent.

The present inventor, as a result of earnest research to solve the above-mentioned belt end separation in the belt structure having the above structure,
By disposing the belt ply of the tire inclined at a relatively large angle between the two belt plies having the cord inclined at a small angle with respect to the tire equatorial plane and the carcass, the concentration of strain at the belt cord end can be effectively performed. The inventors have completed the present invention, finding that they can be prevented and the problems can be solved.

An object of the present invention is to provide a radial tire for a motorcycle, which has high steering stability and improved durability.

[0013]

The invention according to claim 1 is
A radial tire for a motorcycle in which the tread length, which is the distance between the edges of the tread portion, is the maximum width of the tire, and the main body portion extends from the tread portion through the sidewall portion to the bead portion and is connected to the main body portion. A carcass using one or more carcass plies having a carcass cord that has a winding part that folds back around the bead core of the bead part and that is inclined at an angle of 70 to 90 ° with respect to the tire equatorial plane,
A belt layer disposed inside the tread portion and radially outside the carcass, and a bead apex extending from the bead core to the tire radial outside and between the main body portion and the winding portion of the carcass, and the belt. The layer is composed of a ply in which a large number of belt cords are arranged in parallel and is sequentially arranged outward from the carcass in the tire radial direction, and a second belt ply,
A third belt ply and three belt plies are provided, and the belt cords of the respective belt plies intersect with the cords of the adjacent belt plies with their directions of inclination with respect to the tire equatorial plane reversed, and also with respect to the tire equatorial plane. The angle is within the following range, and the first belt ply: 30 to 50 ° The second belt ply: 15 to 30 ° The third belt ply: 15 to 30 ° The inclination angle of the first belt ply is the same as that of the second belt ply. The belt cord should be larger than 5 ° relative to the inclination angle and the belt cord ply measured in the tire axial direction.
The belt width is such that the belt width of the first belt ply <the second belt ply.
Rye belt width <3rd belt ply belt width relationship
A radial tire for a motorcycle, characterized by having .

In such a radial tire for a motorcycle, the second belt ply and the third belt ply having the cords inclined at 15 to 30 ° with respect to the tire equator plane are arranged so that the cords cross each other. The in-plane bending rigidity of the belt layer is improved, and high steering stability performance can be exhibited.

Since the first belt ply having the cord inclined at 30 to 50 ° with respect to the equatorial plane of the tire is arranged between the second belt ply and the carcass, the carcass having the cord having an angle of 70 to 90 °. And the shearing force generated between the second belt ply and the second belt ply can be relaxed.

Radial tires for motorcycles are the third
Rut ply on its lower surface, from the ply edge to the lower surface
Spreading in contact 5 to 15% of the width BW3 of the third belt ply
It is also possible to dispose a rubber layer having a length of 3 to 7,000 N for the belt cord of the first belt ply.
/, Low modulus cords in mm ^2, the second belt ply, and a belt cord of the third belt ply, also, the belt of the first belt ply modulus is formed by 8000 N / mm ² or more high modulus cords The cords are nylon cords, and aromatic polyamide cords can also be used as the belt cords of the second belt ply and the third belt ply.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a radial tire for a motorcycle (hereinafter referred to as a tire) 1 is shown in a normal state in which a regular rim R is assembled into a rim and a regular internal pressure is filled. Here, the "regular rim" is a rim that is defined for each tire in the standard system including the standard on which the tire is based. For example, in the case of JATMA, the standard rim and TRA.
If so, "Design Rim", or if ETRTO, then "Design Rim"
In addition, "regular internal pressure" is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. "TIRE LOAD LIMITS AT VAR
Maximum value stated in "IOUS COLD INFLATION PRESSURES", ET
If it is RTO, it will be "INFLATION PRESSURE".

The tire 1 includes a tread portion 2, sidewall portions 3 extending inward in the tire radial direction from tread ends E1 and E2 at both ends thereof, and a bead located at an inner end of the sidewall portion 3 in the tire radial direction. A tread width W, which is the length in the tire axial direction between the tread ends E1 and E2, is the maximum width j of the tire, and the bead portion 4 has a plurality of metal parts. A bead core 5 in which wires are bundled is arranged. The tire axial width between the tread ends E1 and E forms the maximum tire width.

The body portion 6A extending from the tread portion 2 through the side wall portion 3 to the bead portion 4 is provided with a folded-back portion 6B for winding the bead core 5 from the inner side toward the outer side in the tire axial direction. A carcass 6 locked by means of a hard rubber is disposed between the main body 6A and the folded-back portion 6B, and has a substantially triangular cross-sectional shape from the bead core 5 outward in the tire radial direction. A bead apex 9 is arranged.

The carcass 6 comprises at least one carcass ply in which carcass cords a having a carcass cord a having an inclination angle α of 70 to 90 ° with respect to the tire equatorial plane C are arranged in parallel. In the present embodiment, Carcass 6
Three carcass plies 6 sequentially arranged from the tire bore side
a, 6b, 6c. The inclination angle α may be the same or different for each carcass ply within the above range, but if it is less than 70 °, the performance as a radial tire is difficult to be exhibited.

Further, in this embodiment, each carcass ply 6a,
6b, for each carcass cord a tire equatorial plane C of 6c, inclined oblique angle α1 of approximately 80 ° as shown in FIG. 3,
The carcass cords a of the carcass plies 6a, 6b and 6c which are inclined by α2 and α3 (α1 = α2 = α3≈80 °) and which are adjacent to each other intersect each other. Therefore, as shown in FIG. 3, the carcass ply 6a and the carcass cord a of the carcass ply 6c have the tire equatorial plane C as the vertical axis.
Is oriented, for example, to the right when viewed from the outside in the tire radial direction, and the carcass cord a of the carcass ply 6b is oriented to the left. Further, in the present specification, the inclination angle of the cord with respect to the tire equatorial plane C means an angle on the side forming an acute angle with respect to the tire equatorial plane C regardless of the direction.

Further, each carcass ply 6a, 6b, 6c is
Height ha of the winding-up ends Pa, Pb, Pc of the folded-back portion 6B from the bead baseline BL in the tire radial direction ha,
hb and hc are set to ha>hb> hc, whereby the carcass plies 6a and 6b, which are on the outer side in the tire axial direction in each folded-back portion 6B, are adjacent to each other on the inner side.
By covering the winding ends Pb and Pc of the b and 6c and increasing the tire radial height ha of the folded-back portion of the outer carcass ply 6a beyond the maximum width position of the carcass 6 which is largely deformed during traveling ( However, the tread edge E1,
(Below the height of E2), the strain caused by the deformation of the sidewall rubber layer when the tire is deformed is minimized to concentrate on the carcass ply winding-up ends Pa, Pb, Pc, and the adhesive breakage starting from the carcass cord end is prevented. It suppresses and prevents excessive increase in sidewall rigidity.

The carcass cord a is nylon, rayon,
Organic fiber cords such as polyester and aromatic polyamide are preferably used. In this example, a nylon cord is used.

A belt layer 7 is arranged inside the tread portion 2 and outside the carcass 6 in the radial direction.
Each of the belt plies 7a, 7b is composed of a first belt ply 7a, a second belt ply 7b, and a third belt ply 7c, which are sequentially arranged outward from the carcass 6 in the tire radial direction.
7c uses a ply in which belt cords b arranged in parallel are embedded in topping rubber.

As shown in FIG. 3 together with the carcass cord a, the belt cord b has a relatively small inclination angle β with respect to the equatorial plane C of the tire as compared with the carcass cord a, so that the belt cord b has a circumferential rigidity. It is increased and exhibits the hoop effect as a belt layer required for a radial tire.

The inclination angle β1 of the belt cord of the first belt ply 7a with respect to the tire equatorial plane C of each belt cord b
Is 30 ° or more and 50 ° or less, and the inclination angles β2 and β3 of the second and third belt plies 7b and 7c are 15 ° or more and 3 or more.
It is set to 0 ° or less. That is, 30 ° ≦ β1 ≦ 50 ° 15 ° ≦ β2 ≦ 30 ° 15 ° ≦ β3 ≦ 30 °

When the belt cord angle of the second and third belt plies exceeds 30 °, the rigidity in the circumferential direction is low and the hoop effect required for the radial tire is insufficient, while it is less than 15 ° on the above-mentioned surface. Decrease inward bending rigidity. Therefore, the inclination angles β2 and β3 are larger than 15 ° and 30 °.
It is set to a smaller value, preferably in the range of 15 ° to 20 °. Further, by arranging the belt cords b of the second and third belt plies 7b and 7c so as to cross each other, these two second plies
The in-plane bending rigidity is increased by the composite stack of the third belt plies 7b and 7c, and high steering stability performance can be obtained.

The belt cord b of the first belt ply 7a has an inclination angle β1 with respect to the tire equatorial plane C of 30 °.
It is set within the range of 50 ° or less and more than 5 ° in comparison with the inclination angles β2, β3 of the second and third belt plies 7b, 7c, preferably 15 ° or more. .

With this setting, the first belt ply 7a
Between the carcass cord a of the carcass ply 6c having the inclination angle α (70 ° to 90 °) and the belt cord b having the inclination angle β2 (15 ° to 30 °) of the second belt ply 7b. It can be oriented in the intermediate angle range.

Such an orientation is such that the carcass cord a of the outermost carcass ply 6c has an inclination angle α of 70 ° to 90 ° and extends substantially in the tire axial direction, as described above.
The belt cord b of the second belt ply 7b has an inclination angle β2.
Is 15 ° to 30 ° and extends substantially in the equatorial plane direction of the tire. Therefore, when the tire is repeatedly deformed, the carcass ply 6c and the second belt ply 7b ply have different deformation directions. The shear strain generated can be suppressed and reduced, and the cause of the adhesive failure between the cord and the rubber in each ply caused by this shear strain can be reduced.

By inserting the first belt ply 7a in this manner, this shear strain can be suppressed.
The belt cord of the first belt ply is preferably 35 °
It is set in the range of up to 45 °.

Further, in this example shown in FIG. 3, the belt cord b of the first belt ply 7a and the third belt ply 7c are used.
The belt cord b of the second belt ply 7b is, when viewed from the outside in the tire radial direction, rising to the left.
It will be placed to the right.

Incidentally, in the case shown in FIG. 3, the belt cord b of the second belt ply 7b is oriented to the right upward like the carcass cord a of the carcass ply 6c of the outermost layer. 4A, the inclination angle γ1 of the bisector X1 between the belt cord b and the carcass cord a is defined by the carcass ply 6
Carcass cord a with an inclination angle α of c (70 ° to 90 °)
And the inclination angle β of the second and third belt plies 7b, 7c
When calculated from 2, β3 (15 ° to 30 °), 30 ° to 4
On the other hand, when the belt cord b of the second belt ply 7b is oriented to the upper left, the angle of FIG.
As shown in (B), the inclination angle γ2 of the bisector X2 is 2
It will be about 7.5 ° to 42.5 °.

As described above, the belt cord b of the first belt ply 7a and the inclination angle β2 of the second belt ply 7b are set so as to have an angle difference of 5 ° or more, preferably 15 ° or more. The belt cord b of the first belt ply 7a can be oriented between the belt cord b of the second belt ply 7b and the carcass cord a of the outermost carcass ply 6c to suppress shear strain.

The rigidity of the first belt ply is
3500-7000N / mm lower than the 3rd belt ply
It is preferable to use a ^2- modulus cord in order to reduce shear strain. More preferably, a cord having a smaller modulus than the carcass cord is used. Nylon cords are preferable because they are preferably highly adhesive to rubber.

The belt cord b of the second and third belt plies 7b and 7c is an organic fiber cord of nylon, polyester or the like, and 8000 N / mm for increasing the belt rigidity.
^It is preferred to use more than one cord, for example an aromatic polyamide cord. A steel cord may be used to further increase the belt rigidity.

[0037] Also, the width of the first belt ply 7a (tire axial direction length: hereinafter the same) BW1, the second belt ply 7
The width BW2 of b and the width BW3 of the third belt ply 7c are B
It is set to W1 <BW2 <BW3. Due to this relationship
By covering the edge BP1 of the first belt ply 7a with the second belt ply 7b and the edge BP2 of the second belt ply 7b with the third belt ply 7c, damage originating from the belt end is prevented.

Further, as shown in FIG. 2, the sidewall rubber 3 enters a wedge shape between the edge BP2 of the second belt ply 7b, which is likely to be a starting point of damage, and the carcass, thereby suppressing strain concentration at the edge BP2. To do.

Further, between the second belt ply 7b and the third belt ply 7c in the vicinity of the second belt ply edge BP2, the lower surface of the third belt ply 7c is contacted , and as shown in FIG.
Ply of the third belt ply 7c as specified in FIG.
The rubber layer 8 extending from the edge BP3 is arranged. The length of the rubber portion 8 in the tire axial direction is about 5 to 15% of the width BW3 of the third belt ply 7c. This allows
The shearing between the second belt ply 7b and the third belt ply 7c is suppressed, and the concentration of strain on the second belt ply edge BP2 is prevented. Further, the edge BP3 of the third belt ply 7c is set in a state of floating in the tread rubber 2 to suppress the concentration of strain due to the force from the outside of the tread.

[0040]

SPECIFIC EXAMPLE For tires having a tire size of 180 / 60R16, tires having the specifications shown in Table 1 were prototyped and subjected to an indoor drum test and an actual vehicle test. For the indoor durability test, the tire was assembled on a regular rim, the internal pressure was filled to 200.0 kPa, and 150% of the standard maximum load was applied, and the speed was 65 km.
/ H and run until damage occurs, and set the distance to 1 in Comparative Example 1
It is represented by an index of 00. The standard is JATMA.
According to the standard. The actual vehicle test is on the test course
The sensory evaluation results are represented by an index with Comparative Example 1 as 100.

[0041]

[Table 1]

[0042]

INDUSTRIAL APPLICABILITY As described above, the radial tire for a motorcycle according to the present invention can effectively prevent the concentration of strain at the belt cord end, has high steering stability, and has improved durability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating one embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the vicinity of the belt end portion.

FIG. 3 is a cross-sectional view illustrating the directions and inclination angles of the cords of the belt ply and the carcass ply.

4A and 4B are diagrams illustrating a belt cord of a first belt ply.

[Explanation of symbols]

2 tread section 3 Side wall part 4 bead part 5 bead core 6 carcass 7 Belt layer 8 rubber layers

Claims (4)

(57) [Claims] 1. A radial tire for a motorcycle, wherein the tread length, which is the distance between the edges of the tread portion, has the maximum width of the tire, and the main body portion extends from the tread portion through the sidewall portion to the bead portion. One or more carcass plies having a carcass cord connected to the main body part and folded around the bead core of the bead part, and having a carcass cord inclined at an angle of 70 to 90 ° with respect to the tire equatorial plane. Carcass, a belt layer disposed inside the tread portion and radially outside the carcass, and a bead apex extending from the bead core to the tire radial outside and between the main body portion and the winding portion of the carcass. The belt layer is composed of plies in which a large number of belt cords are arranged in parallel, and is sequentially arranged from the carcass outward in the tire radial direction. The first belt ply, the second belt ply, and the third belt ply have three belt plies, and the belt cord of each belt ply has a direction opposite to the cord of the adjacent belt ply and the tire equatorial plane. with inclined to intersect with each other, with a range of less than the inclination angle with respect to the tire equatorial plane, the first belt ply: 30 to 50 ° the second belt ply: 15 to 30 ° third belt ply: 15 to 30 ° No. The belt measured in the tire axial direction of each belt ply is larger than the inclination angle of the belt cord of the second belt ply by more than 5 °.
The width of the first belt ply <the second belt ply
The belt width of <the belt width of the third belt ply
Radial tire for a motorcycle, characterized in that that. 2. The third belt ply has a ply on the lower surface thereof.
Width of the third belt ply extending from the edge to the lower surface
The radial tire for a motorcycle according to claim 1, wherein a rubber layer having a length of 5 to 15% of BW3 is arranged . 3. The belt cord of the first belt ply,
The low modulus cord having a modulus of 3500 to 7000 N / mm ² , the belt cords of the second belt ply and the third belt ply are high modulus cords having a modulus of 8000 N / mm ² or more.
Alternatively, the radial tire for a motorcycle according to claim 2. 4. The belt cord of the first belt ply comprises a nylon cord, and the second belt ply and the third belt ply.
The radial tire for a motorcycle according to claim 3, wherein an aromatic polyamide cord is used as the belt cord of the belt ply.