JP2002154306A - Radial tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radial tire for a motorcycle with improved stability when traveling straight and when turning. SOLUTION: This tire for the motorcycle is provided with a carcass and a belt layer. The carcass is formed of a carcass ply with the radial arrangement with a carcass cord of the organic fiber tilted at 70-90 degree in relation to the tire equator, and the belt layer is formed by spirally winding a small width and long size strip ply formed of one belt cord formed by coating a twisted aromatic polyamide cord of the aromatic polyamide fiber with the topping rubber, or parallel plural belt cords by tilting there at a small angle in relation to the tire equator. A constant load elongation of the belt cord in belt end region is set larger than a constant load elongation of the belt cord in the tire equator region.

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, which is capable of improving a straight running stability and a cornering stability.

[0002]

2. Description of the Related Art In radial tires for motorcycles,
For example, Japanese Patent Application Laid-Open No. 5-92702 discloses a method for enhancing the haze effect in the tread portion and improving durability and wear resistance.
Japanese Unexamined Patent Publication No. 6-55906 proposes a belt layer in which a belt cord is spirally wound substantially parallel to the tire circumferential direction, and the belt cord used in such a belt layer is a belt layer. In order to increase the rigidity of steel cords, steel cords and aromatic polyamide cords are being used instead of conventional nylon and polyester cords.

[0003] By the way, a motorcycle is different from a four-wheeled vehicle such as a passenger car and a truck in that the cross section of the tread surface in the tire axial direction is rounded, that is, the tread radius of curvature is increased, in order to incline the entire vehicle at the time of turning. By making it smaller than other categories of tires, for example, by setting the tread edge to a height position of about half the tire cross-section height,
Even in a turning state in which the vehicle is tilted, a ground contact surface exists so that a smooth turning can be performed while maintaining the grip on the road surface.

[0004] Further, at the time of turning, the frictional force generated on the area where the road surface comes into contact with the tire at the time of inclination, that is, the frictional force generated on the ground contact surface at the time of turning makes the vehicle turn against the centrifugal force applied to the vehicle. Is not flat and smooth, and the uneven road surface gives a disturbance to the tire when turning.

At this time, the steel cord as described above,
In a motorcycle tire using an aromatic polyamide cord as a belt cord, the rigidity near the end of the belt that touches the ground when the vehicle is tilted becomes too high, cannot absorb the disturbance, and the tire jumps up. It was found that the ground could not be secured, the vehicle could not withstand the centrifugal force, and the vehicle could wander or fall.

In order to solve such a problem, a belt ply made of an aromatic polyamide cord at an angle in the tire circumferential direction is combined with a belt ply made of a low elastic cord made of nylon or the like parallel to the tire circumferential direction. A motorcycle radial tire using a belt layer has been proposed.

[0007]

However, in such a proposal, the structure of the belt layer is complicated, the productivity is reduced, the cost is increased, and the cord ply is angled in the tire circumferential direction. And the ply of cords parallel to the tire circumferential direction are arranged in parallel, so that the change in the cord angle of the angled cords that occurs during tire molding causes the cords to be arranged in parallel to the tire circumferential direction with the angle and code density. Disturbance is likely to occur.

The present invention focuses on the elongation of the belt cord, and as a result of various developments, has found that the above problem can be solved by increasing the constant load elongation at the belt end in the belt layer. Accordingly, it is an object of the present invention to provide a radial tire for a motorcycle which can improve the straight running stability and the turning stability.

[0009]

According to the first aspect of the present invention, the tread width, which is the distance between the tread edges in the tire axial direction, forms the maximum width of the tire, and the bead core of the bead portion passes from the tread portion through the sidewall portion. A toroidal carcass that folds around, and a belt layer that is disposed inside the tread portion and radially outside the carcass and has a width in the tire axial direction of 0.5 to 1.1 times the tread width. A motorcycle tire comprising a carcass,
A carcass cord made of organic fibers is made of a radially arranged carcass ply inclined at an angle of 70 to 90 ° with respect to the tire equator, and the belt layer is topped with an aromatic polyamide cord formed by twisting aromatic polyamide fibers. A belt formed by spirally winding a single belt cord covered with rubber or a narrow and long belt-like ply consisting of a plurality of belt cords arranged in parallel at a small angle with respect to the tire equator. It is characterized in that the constant load elongation of the belt cord in the end region is larger than the constant load elongation of the belt cord in the tire equator region.

[0010] Here, the constant load elongation refers to the elongation of the cord under a load condition measured by a method specified in JIS standard L1017 and determined by the material and thickness of the cord.

[0011] According to the first aspect of the present invention, by increasing the constant load elongation of the belt cord in the belt end region to be larger than that in the tire equatorial region, the belt layer is formed near the tire equatorial plane. The constant load elongation rigidity in the tire equator area where the highest circumferential rigidity is required during straight running is reduced, and at the belt end area where the vehicle is in contact with the ground due to the inclination of the vehicle during turning, it is caused by road surface disturbance. In order to prevent the stability of the vehicle from deteriorating, the constant load elongation of the belt cord in that region is increased to facilitate the absorption of disturbance.

Further, the constant load elongation of the belt cord is minimized on the equatorial plane of the tire and gradually increases toward the belt end, so that the belt cord has a constant load elongation within the belt layer. This eliminates sudden changes in the vehicle, reducing the instability that the driver experiences.

Further, according to the third aspect of the present invention, the constant load elongation Ee at the belt end is changed by a ratio (Ee−Eq) / Eq, which is a constant load elongation change ratio, to the constant load elongation Eq of the tire equatorial plane. 20% or more and 100% or less, disturbance in the belt end region is efficiently prevented, and excessive constant load elongation is prevented from decreasing, thereby maintaining the belt function.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a tire meridian section in a standard state in which a motorcycle radial tire (hereinafter referred to as motorcycle tire 1) according to the present invention is assembled on a regular rim R and filled with a regular internal pressure. In this specification, “regular rim” is a standard rim defined by JATMA, TRA
"Measuring Rim" specified in ETRTO or "Design Rim" specified in ETRTO, and "regular internal pressure" is the maximum air pressure specified in JATMA, TR
Table of A "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION
PRESSURES "or" INFLATION PRESSURE "specified by ETRTO.

The motorcycle tire 1 has a tread portion 2, a sidewall portion 3 extending radially inward from both ends of the tread portion 2, and a bead portion 4 located at an inner end of the sidewall portion 3 in the tire radial direction. And tire equatorial plane C
A radial distance HF from the point T on the upper tread surface to the tread edge E, a tread edge height HE which is a radial distance from the bead base line BL which is the diameter of the regular rim R to the tread edge E, Of the ratio HE / HF is 0.8 ≦ H
It is set in the range of E / HF ≦ 1.2. This allows
The distance HF from the point T on the tire equatorial plane to the tread edge E is approximately the middle of the tire section height H, which is the radial distance from the point T to the bead base line BL. Will be done. The tire axial distance WT between the tread edges E, E forms the maximum width WT of the tire.

The tire 1 for a motorcycle includes the tread 2
A carcass 6 having a winding portion 6b extending from the inside to the outside in the tire axial direction and extending from the carcass 6 to the bead core 5 of the bead portion 4 through the sidewall portion 3 to the bead core 5 of the bead portion 4; A belt layer 7 disposed inside and radially outward of the carcass 6, and in the present embodiment, a bead having a triangular cross-section extending outward in the tire radial direction of the bead core 5 between the main body 6 a and the winding portion 6 b. Apex 8 is arranged.

The carcass 6 comprises one or more carcass plies having a radially arranged carcass cord inclined at an angle of 70 to 90 degrees with respect to the tire equatorial plane C, and in the present embodiment, one carcass ply, As the carcass cord, an organic fiber cord such as nylon, polyester, or aromatic polyamide fiber is used. Further, in the present embodiment, the winding height HC of the leading end of the winding portion 6b from the bead base line BL is not less than 0.3 times and not more than 1.2 times the tread edge height HE.

The belt layer 7 is composed of a belt ply formed by spirally winding a narrow and long belt-like ply 10, and the belt-like ply 10 is composed of one or a plurality of parallel belt cords. In the case shown in FIG. 2, two belt cords 11 and 11 are embedded in a topping rubber 12, and an aromatic polyamide cord in which aromatic polyamide fibers are twisted is used as the belt cord 11. The belt width WB, which is the distance between the outer edges F of the belt layer 7 in the tire axial direction, is 0.5 times or more and 1.1 times or less, preferably 0.7 to 0.7 times the tread width WT.
The range is 1.0 times.

The belt-like ply 10 extends from one outer edge F of the belt layer 7 located on one tread edge E side of the tread portion 2 to the outer edge F on the other tread edge E side beyond the tire equatorial plane C. The belt ply is formed by spirally winding the tire at a small angle of 5 ° or less with respect to the tire equatorial plane C. In winding the band-like ply 10,
Side edges that are adjacent to each other when the belt-shaped ply 10 is spirally wound can be wound while being wrapped with each other, butted, or separated from each other.

Further, the belt layer 7 can be formed as a plurality of layers in which two or more belt plies formed by spirally winding the belt-like ply 10, that is, two or more spirally wound bodies of the belt-like ply 10 are wound. Furthermore, the belt-like ply 10
Preferably, it is wound continuously and continuously from the one outer edge F to the other outer edge F over the tire equatorial plane C, but is discontinuous at the tire equatorial plane C from both outer edges F toward the tire equator, Alternatively, it may be discontinuous at a small number of positions, such as being wound on both sides from the tire equatorial plane C. When a plurality of layers are provided, it is preferable to displace the discontinuous portion in the tire axial direction.

Further, in the motorcycle tire 1 of the present invention, the constant load elongation of the belt cord 11 in the belt end region is made larger than the constant load elongation of the belt cord 11 in the tire equator region. Here, the tire equator region refers to a region having a width where the tire comes into contact with the vehicle when traveling straight, and the belt end region refers to a region having a width where the motorcycle tire 1 comes into contact with the maximum bank when the vehicle is in a maximum bank. The constant load elongation means the average value of the constant load elongation of the belt cord 11 in each region.

For this reason, preferably, as shown in FIG.
The constant load elongation of the belt cord 11 is minimized at the tire equatorial plane C, and is gradually increased toward the belt end F. Further, the constant load elongation change ratio, which is the ratio (Ee−Eq) / Eq of the constant load elongation Ee at the belt end F to the constant load elongation Eq of the belt cord at the tire equatorial plane C, is 20% or more and 100% or more. % Or less.

In FIG. 3, the abscissa indicates the position of the belt layer 7 in the tire axial direction, and the ordinate indicates the constant load elongation (%) of the belt cord at each position, and the constant load elongation on the tire equatorial plane C. Eq is 1.0%, which is the minimum value in the belt layer 7, and the constant load elongation Ee at the belt end F is 1.6%.
And shows the maximum value, and there is no rapid change in the meantime. In the case of FIG. 3, the constant load elongation change rate, which is the ratio (Ee−Eq) / Eq of the constant load elongation Ee at the belt end F to the constant load elongation Eq of the belt cord at the tire equatorial plane C is: 60%.

For this reason, for example, the belt cord 11
The aromatic polyamide fibers are twisted to form a plurality of strands 13 having a fineness of 840d to 1890d, preferably 2 or more and 6 or less with a low twist of 24 to 29 times per 10 cm of twist. Using the belt cord 11 obtained, for example, a belt layer having a constant load elongation distribution shown in FIG. 3 is obtained by the following steps.

The belt-shaped ply 10 using the belt cord 11 is spirally wound with a constant tension on a profile drum at a small angle with respect to the tire circumferential direction with the longitudinal axis of the belt cord 11 aligned with the surface direction of the drum. . The outer peripheral shape of this profile drum is such that the outer diameter at each position is smaller than the inner diameter at each corresponding position of the tire vulcanizing die, and the ratio of the drum outer diameter to the die inner diameter (die inner diameter / drum outer diameter). Is set to be smaller at the tread end so that the belt end F has a constant load elongation change in the molded tire as described above than the tire equatorial plane C.

The drum-shaped tubular body of the spirally wound belt-like ply 10 is moved onto the expanded carcass, and a rubber member such as tread rubber is bonded to form a raw tire.

By loading the green tire into a vulcanizing mold and vulcanizing and molding, the belt cord at each position is expanded at the ratio of the mold inner diameter / drum outer diameter at the time of vulcanizing molding. That is, during vulcanization, the belt cord is vulcanized in a stretched state under tension and molded as a tire. As a result,
The tire equatorial plane C is stretched more than the belt end F during molding, and the molded motorcycle tire 1 is shown in FIG.
The belt layer of the belt cord having a constant load elongation distribution shown in FIG. Such a process can be easily set and performed by those skilled in the art including setting of the characteristics of the belt cord.

Alternatively, the profile drum and the vulcanizing mold are formed in the same shape, and the tension applied to the cord when it is wound around the profile drum is applied to the tire equatorial plane after the belt cord is stretched at each position. It is also possible to obtain a belt layer having a constant load elongation distribution of the belt cord according to the present invention by winding the cord so that the cord has a maximum at the position and a minimum at the outer edge of the belt.

It should be noted that other production steps can be adopted, and since the aromatic polyamide fiber has a breaking elongation of about 5%, the elongation of the belt cord during running of the finished tire is kept within the above range. Set the load elongation rate and its change rate.

[0030]

EXAMPLE A tire having a tire size of 190 / 50R17 and having the structure shown in FIG. 1 was prototyped according to the specifications shown in Table 1 and its performance was tested. The test conditions are as follows. Test vehicle: Domestic motorcycle with a displacement of 1000 CC. Running path: Okayama test course at Sumitomo Rubber Industries, Ltd. Running conditions: Turning at a speed of 180 km / h and a radius of 150 m. Evaluation method: Sensory evaluation of the same test driver (out of 5 points. The higher the better.)

[0031]

[Table 1]

As a result of the test, the example of the present invention had better running performance than that of the comparative example.

[0033]

As described above, the radial tire for a motorcycle according to the present invention has a belt cord formed by twisting aromatic polyamide fibers, and has a constant load elongation at each position in the tire axial direction of the belt. On the basis of increasing toward the end, straight running stability and turning running stability could be improved.

[Brief description of the drawings]

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

FIG. 2 is a perspective view illustrating a belt-like ply.

FIG. 3 is a diagram showing a distribution of a constant load elongation of a belt cord in a belt layer.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 10 Belt ply 11 Belt cord 12 Topping rubber

Claims (3)

[Claims] 1. A toroidal carcass in which a tread width, which is a distance in the tire axial direction between tread edges, forms a maximum width of a tire, and a toroidal carcass is folded from a tread portion through a sidewall portion and around a bead core of a bead portion. A motorcycle tire having a belt layer that is disposed inside the portion and radially outside of the carcass and has a width in the tire axial direction of 0.5 to 1.1 times the tread width, and The carcass is made of a radially arranged carcass ply in which a carcass cord made of an organic fiber is inclined at an angle of 70 to 90 ° with respect to the tire equator, and the belt layer is formed by twisting aromatic polyamide fibers. One belt cord coated with a polyamide cord with topping rubber, or a narrow and long belt cord composed of multiple belt cords arranged in parallel The ply is formed by spirally winding the ply at a small angle with respect to the tire equator, and the constant load elongation of the belt cord in the belt end region is larger than the constant load elongation of the belt cord in the tire equator region. A radial tire for a motorcycle, comprising: 2. The radial tire for a motorcycle according to claim 1, wherein the constant load elongation of the belt cord is minimum at the tire equatorial plane and gradually increases toward the belt end. 3. The constant load elongation Ee at the belt end is a ratio (Ee−E) to the constant elongation Eq of the tire equatorial plane.
The radial tire for a motorcycle according to claim 1 or 2, wherein a constant load elongation change ratio of q) / Eq is 20% or more and 100% or less.