JP2002059705A - Radial tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radial tire for a motorcycle improved in durability. SOLUTION: The radial tire for the motorcycle has a carcass, a belt layer and a bead apex, the belt layer is furnished with three belt plies of a first belt ply, a second belt ply and a third belt ply to be sequentially arranged outward in the tire radial direction from the carcass, belt cords of the belt plies cross with each other by conversely inclining directions of the belt plies adjacent to each other against the cords and a tire equatorial surface, an inclination against the tire equatorial surface is specified in a following range, and the inclination of the first belt ply exceeds 5 deg. in comparison with the inclination of the belt cord of the second belt ply. First belt ply: 30-50 deg. Second belt ply: 15-30 deg. Third belt ply: 15-30 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire for a motorcycle having improved durability.

[0002]

2. Description of the Related Art Motorcycle tires have a stable running performance,
From grip performance, etc., 70-90 with respect to the tire equatorial plane
In recent years, a radial type having a carcass having carcass cords 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 frequently used. .

[0003] The belt cord of the belt layer is provided with a high modulus cord in order to provide a required hoop effect to the radial tire, and is arranged at a relatively small angle with respect to the tire equatorial plane.

[0004] On the other hand, unlike a four-wheeled vehicle, a motorcycle inclines by turning the vehicle body in the direction of the turning center during turning to generate a cornering force and turn. Therefore, the tread surface is formed on the tread surface of a tire for a four-wheeled vehicle. Since the tread width, which has a larger curvature and the length in the tire axial direction between the tread edges, is usually set to be much larger than the maximum width of the carcass, the tread width becomes the maximum width of the tire. In addition, the tread edge is configured to be located at a height of about 1/2 of the tire section height.

[0005] For this reason, under straight running conditions and when the vehicle is turning, the center of contact greatly moves, and under running conditions in which left and right cornering are repeated, the deformation movement of the belt layer is larger than that of a tire for a four-wheeled vehicle. As a result, the bonding between the belt cord and the rubber in the belt layer is broken due to the relatively high modulus used as the belt cord of the belt layer that gives the tag effect as a radial tire. Belt edge (BEL)
is called.

In order to prevent the belt end peeling, Japanese Patent Application Laid-Open No. 5-246210 discloses a radial for a motorcycle having a belt having no cord end formed by spirally winding a belt-like cord layer in a tire circumferential direction. A tire has been proposed and this tire has been put to practical use.

[0007] However, it is required to further improve the steering stability as well as the running performance of the motorcycle. However, although the proposed belt layer has no cord end, the belt cord is parallel to the tire equatorial plane. , The in-plane bending rigidity of the belt ply is low, and the drag in the tire axial direction is small, so that the steering stability performance cannot be improved.

[0008] Further, there has been proposed a structure in which a reinforcing layer is provided outside the side wall portion to increase the rigidity of the side wall portion and compensate for insufficient rigidity of the belt layer.

[0009]

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

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

The inventor of the present invention has conducted intensive studies on the belt structure having the above-described structure in order to solve the belt edge peeling.
By arranging the belt ply of the tire inclined at a relatively large angle between the two belt plies having cords inclined at a small angle with respect to the tire equatorial plane and the carcass, the concentration of strain at the end of the belt cord is effectively performed. It has been found that the above problems can be solved and the above problems can be solved, and the present invention has been completed.

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

[0013]

According to the first aspect of the present invention,
A motorcycle radial tire in which the tread length, which is the distance between the edges of the tread portion, is the maximum width of the tire, wherein 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 having one or more carcass plies having a carcass cord having a winding portion which is turned around a bead core of a bead portion and 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 outward of the carcass, and a bead apex extending radially outward from the bead core in a tire radial direction and between a main body portion and a winding portion of the carcass; The layer comprises a first belt ply having a plurality of belt cords arranged in parallel and sequentially arranged radially outward from the carcass in the tire radial direction, and a second belt ply.
A third belt ply and three belt plies, wherein the belt cords of the respective belt plies cross each other by inclining the cords of the adjacent belt plies with respect to the tire equatorial plane in opposite directions, and at the same time, the inclination with respect to the tire equatorial plane. The angle is set in the following range, and the inclination angle of the first belt ply is larger than the inclination angle of the belt cord of the second belt ply by more than 5 °. It is a radial tire. First belt ply: 30 to 50 ° Second belt ply: 15 to 30 ° Third belt ply: 15 to 30 °

Such a radial tire for a motorcycle has a structure in which a second belt ply and a third belt ply having a cord inclined at 15 to 30 ° with respect to the tire equatorial plane are arranged such that the cords cross each other. In addition, 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 a 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 a cord having an angle of 70 to 90 ° is provided. And the shear force generated between the second belt ply and the second belt ply can be reduced.

In the radial tire for a motorcycle, the belt width of each of the belt plies measured in the tire axial direction is equal to a first width.
Belt ply <second belt ply <third belt ply, the belt code of the first belt ply may be
The second belt ply and the belt cord of the third belt ply have a modulus of 8000 N / mm ^{2 and} a low modulus cord having a modulus of 3500-7000 N / mm 2.
^The belt cord of the first belt ply may be formed of a nylon cord, and the belt cord of the second belt ply and the third belt ply may be formed of an aromatic polyamide cord. You can also.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a motorcycle radial tire (hereinafter referred to as a tire) 1 is illustrated in a normal state in which a rim is assembled to a normal rim R and a normal internal pressure is charged. Here, the “regular rim” is a rim defined for each tire in a standard system including a standard based on a tire. For example, in JATMA, a standard rim, TRA
"Design Rim" for ERTTO
Measuring Rim ". The" normal internal pressure "is the air pressure specified for each tire in the standard system including the standard on which the tire is based. "TIRE LOAD LIMITS AT VAR
IOUS COLD INFLATION PRESSURES "maximum value, ET
For RTO, use "INFLATION PRESSURE".

The tire 1 has a tread portion 2, a sidewall portion 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. And a tread width W, which is the length in the tire axial direction between the tread ends E1 and E2, is formed to be the maximum width j of the tire. The bead core 5 which bundled the wires is arranged. The length in the tire axial direction between the tread ends E1 and E forms a tire maximum width.

Further, the bead core 5 is provided with a folded portion 6B which is wound up from the inside in the tire axial direction to the outside by the bead core 5 on the main body 6A extending from the tread portion 2 through the sidewall portion 3 to the bead portion 4. The carcass 6 is disposed between the main body portion 6A and the folded portion 6B, and has a substantially triangular cross-section from the bead core 5 outward in the tire radial direction, and is made of hard rubber. Bead apex 9 is arranged.

The carcass 6 is composed of at least one carcass ply in which carcass cords a forming an inclination angle α of 70 to 90 ° with respect to the tire equatorial plane C are arranged in parallel. Carcass 6
Three carcass plies 6 arranged sequentially from the tire bore side
a, 6b and 6c. Note that the inclination angle α can 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 hardly exhibited.

In this embodiment, each carcass ply 6a,
Each of the carcass cords 6b and 6c has an inclination angle α of about 80 ° with respect to the tire equatorial plane C, as shown in FIG. 3, where the inclination angles α1, α2, α3 (α1 = α2 = α3 ≒ 80 °).
And the adjacent carcass plies 6a, 6b, 6
The carcass cord a of c crosses each other. For this reason, as shown in FIG.
The carcass cords a of the carcass ply 6a and the carcass ply 6c are oriented, for example, to the right as 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 formed by 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.

Each carcass ply 6a, 6b, 6c
Tire radial height ha from the bead base line BL of each of the winding ends Pa, Pb, and Pc of the folded portion 6B,
hb and hc are defined as ha>hb> hc, so that the carcass plies 6a and 6b which are located on the outer side in the tire axial direction at each folded portion 6B are adjacent to the carcass plies 6 which are located on the inner side.
By covering the winding ends Pb and Pc of the carcass ply 6a and the turning-up portion of the outer carcass ply 6a, the height ha in the tire radial direction is increased beyond the maximum width position of the carcass 6 where deformation during running is large. However, tread edge E1,
Below the height of E2), the concentration of the strain due to the deformation of the sidewall rubber layer when the tire is deformed on the carcass ply winding ends Pa, Pb, Pc is reduced as much as possible, and the adhesive failure starting from the carcass cord end is reduced. Suppression and excessive increase in sidewall rigidity are prevented.

The carcass cord a is made of 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.
A first belt ply 7a, a second belt ply 7b, and a third belt ply 7c are sequentially arranged outward from the carcass 6 in the tire radial direction, and each belt ply 7a, 7b,
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 tire equatorial plane C as compared with the carcass cord a, thereby increasing circumferential rigidity. Increases and exerts a tag 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 not less than 30 ° and not more than 50 °, and the inclination angles β2 and β3 of the second and third belt plies 7b and 7c are not less than 15 ° and 3 °.
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 small, and the hoop effect required for the radial tire is insufficient. Decreases internal bending stiffness. For this reason, the inclination angles β2 and β3 are larger than 15 ° and 30 °.
Smaller, 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 in an intersecting manner, the two second
The in-plane bending rigidity is increased by the composite overlap 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 °.
The angle difference is set so as to have an angle difference larger than 5 ° compared to the inclination angles β2 and β3 of the second and third belt plies 7b and 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 an intermediate angle range.

As described above, 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 tire equatorial plane direction. When the tire is repeatedly deformed, the direction of deformation differs between each carcass ply 6c and the second belt ply 7b ply. The generated shear strain can be suppressed and reduced, and the cause of the adhesive failure between the cord and the rubber in each ply caused by the shear strain can be reduced.

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

Further, in this embodiment shown in FIG. 3, the belt cord b of the first belt ply 7a and the third belt ply 7c
The belt cord b of the second belt ply 7b is ascending left as viewed from the outside in the tire radial direction.
It is arranged upward to the right.

In the case shown in FIG. 3, the belt cord b of the second belt ply 7b is oriented to the upper right like the carcass cord a of the outermost carcass ply 6c. 4 (A), the inclination angle γ1 of the bisector X1 between the belt cord b and the carcass cord a is determined by the carcass ply 6
carcass cord a having an inclination angle α of c (70 ° to 90 °)
And the inclination angle β of the second and third belt plies 7b and 7c.
2, β3 (15 ° -30 °), 30 ° -4
7.5 °, on the other hand, when the belt cord b of the second belt ply 7b is oriented to the upper left, FIG.
As shown in (B), the inclination angle γ2 of the bisector X2 is 2
It is about 7.5-42.5 °.

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

The rigidity of the first belt ply is
3500-7000 N / mm lower than the third belt ply
It is preferable to use a ^2- modulus cord in order to reduce shear strain. More preferably, a cord with a modulus smaller than the carcass cord is used. Nylon cords are preferred because they have good adhesion to rubber.

The belt cords b of the second and third belt plies 7b and 7c include organic fiber cords such as nylon and polyester, and 8000 N / mm to increase belt rigidity.
^It is preferred to use more than one cord, for example, an aromatic polyamide cord. In order to further increase the belt rigidity, a steel cord can be used.

In the present embodiment, the width BW1 of the first belt ply 7a (the length in the tire axial direction: the same applies hereinafter), the width BW2 of the second belt ply 7b, and the width B of the third belt ply 7c
W3 is set so that BW1 <BW2 <BW3. Due to this relationship, the edge BP1 of the first belt ply 7a is
Covering with the belt ply 7b and covering the edge BP2 of the second belt ply 7b with the third belt ply 7c prevents damage from the belt end as a starting point.

Further, as shown in FIG. 2, the side wall 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 the concentration of strain at the edge BP2. I do.

A rubber layer 8 extending in contact with the lower surface of the third belt ply 7c is disposed between the second belt ply 7b and the third belt ply 7c near the second belt ply edge BP2. The length of the rubber portion 8 in the tire axial direction is 5 to 15% of the width BW3 of the third belt ply 7c.
Degree. Thereby, the second belt ply 7b and the third belt ply 7b
The shear between the belt plies 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 in a state of floating in the tread rubber 2, thereby suppressing the concentration of strain due to a force from outside the tread.

[0040]

[Specific Example] With respect to a tire having a tire size of 180 / 60R16, a tire having the specifications shown in Table 1 was prototyped, and an indoor drum test and an actual vehicle test were performed. In the indoor durability test, the tire was assembled on a regular rim, the inner pressure was filled to 200.0 kPa, 150% of the standard maximum load was applied, and the speed was 65 km.
/ H until the vehicle is damaged and the distance is set to 1 in Comparative Example 1.
The index is set to 00. The standard is JATMA
According to the standard. The actual car test is performed on the test course
The results of the sensory evaluation are represented by an index with Comparative Example 1 being 100.

[0041]

[Table 1]

[0042]

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

[Brief description of the 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 an end of the belt.

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

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

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 8 Rubber layer

Claims (4)

[Claims] 1. A radial tire for a motorcycle in which a length between treads, which is a distance between edges of a tread portion, is a maximum width of the tire, a main body portion extending from a tread portion to a bead portion through a sidewall portion, and One or more carcass plies having a carcass cord having a winding portion connected to the main body portion and turned around a bead core of the bead portion and inclined at an angle of 70 to 90 ° with respect to the tire equatorial plane are used. A carcass, a belt layer disposed inside the tread portion and radially outward of the carcass, and a bead apex extending radially outward from the bead core in a tire radial direction and between the main body portion and the winding portion of the carcass. The belt layer is composed of plies in which a number of belt cords are arranged in parallel, and is sequentially arranged radially outward from the carcass in the tire radial direction. A first belt ply, a second belt ply, and a third belt ply, wherein the belt cords of the respective belt plies are opposite to the cords of the adjacent belt plies with respect to the tire equatorial plane. While they are inclined and intersect with each other, the inclination angle with respect to the tire equatorial plane is set in the following range, and the inclination angle of the first belt ply is 5 ° as compared with the inclination angle of the belt cord of the second belt ply. Radial tires for motorcycles, characterized by being oversized. First belt ply: 30 to 50 ° Second belt ply: 15 to 30 ° Third belt ply: 15 to 30 ° 2. The belt width of each of the belt plies measured in the tire axial direction has a relation of a belt width of a first belt ply <a belt width of a second belt ply <a belt width of a third belt ply. The radial tire for a motorcycle according to claim 1, wherein 3. The belt cord of the first belt ply,
Modulus low modulus cord 3500~7000N / mm ^2, claim 1 second belt ply and belt cords of the third belt ply, it is that the modulus is characterized in that it consists of 8000 N / mm ² or more high modulus cords
A radial tire for a motorcycle according to claim 2. 4. The belt cord of the first belt ply is made of nylon cord, and the second belt ply and the third belt ply are made of nylon cord.
The radial tire for a motorcycle according to claim 3, wherein an aromatic polyamide cord is used as a belt cord of the belt ply.