JP2000198315A - Tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve rim assembling performance and to reduce off-specification products. SOLUTION: This tire attached to motorcycles of a displacement of 100 cc or less comprises a carcass 6 stretching from a tread part 2 via a sidewall part 3 to bead cores 5 of toes of bead 4. The carcass 6 consists of one carcass ply 6A integrally having a main body part 6a extended between a pair of bead cores 5, and folded back parts 6b joined to both ends of the main body part 6a and folded back around the bead cores 5 from the inside to the outside in a tire axial direction. An overlapping part 7 wherein the folded back parts 6b are mutually overlapped in a tire radial direction at the tread part 2 is formed by extending the folded back parts 6b from the bead cores 5 via the sidewall part 3 to the tread part 2. The bead cores 5 are formed by wrappingly laminating belt plies wherein two parallel steel cords are coated with topping rubber, not less than two and not more than three times in the tire radial direction. A wire diameter (d) of the steel cords is from 0.9 to 1.3 mm and a parallel pitch (p) being the distance between centers of the steel cords is from 1.3 to 1.7 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an engine having a displacement of 100 c.
The present invention relates to a motorcycle tire mounted on a motorcycle such as a motor-equipped bicycle below.

[0002]

2. Description of the Related Art Motorcycles having a displacement of 100 cc or less, such as motorcycles used for motor-driven bicycles and cubs, which are frequently used for delivery of goods or outside business trips, etc. As for tires, not only tire strength is required, but also there are many opportunities to change tires without using special tools at bicycle shops in town, so motorcycle tires with larger displacements A bead structure that is easier to assemble than a rim is desired.

[0003] From such a viewpoint, in this type of tire, a bead core arranged in a bead portion is formed into a single steel cord having a circular cross section having a diameter of about 1 mm and a thickness of about 0.2 mm. Is formed by spirally winding a material covered with the above topping rubber. For example, as shown in FIG. 4, the bead core c is formed by winding steel cords b in three rows in the tire axial direction and three rows in the tire radial direction (3 × 3 structure), or as shown in FIG. It was common to have two rows in the tire axial direction and three rows in the tire radial direction (2 × 3 structure).

However, in the 3 × 3 structure shown in FIG. 4, there is a problem that the rigidity of the bead portion a becomes too high, and the rim assembling work cannot be performed satisfactorily unless a special tool such as a tire lever is used. Was. Also, 2 × 3 shown in FIG.
With the structure, the required rigidity of the bead portion a at the time of traveling can be obtained, and the rim assembling workability without a special tool is also good, but it is difficult to stabilize the winding position when winding up the steel cord b, In addition, due to the pressure during vulcanization at the time of tire molding, the steel cords arranged in the tire axial direction move close to each other due to the decrease in the wire diameter of the steel cord, and as a result, the width BW of the bead portion a Is apt to cause defective production, for example, smaller than expected finished dimensions.

The present invention has been devised in view of the above-mentioned situation, and it is possible to obtain a stable bead portion width while improving the rim assembling property without using a special tool, thereby improving productivity. It is an object of the present invention to provide a motorcycle tire that can be improved.

[0006]

In order to achieve the above object, the present invention provides a toroidal carcass extending from a tread portion to a side wall portion to a bead core of a bead portion and having a displacement of 100 cc or less. A motorcycle tire mounted on a motorcycle, wherein the carcass extends over a pair of the bead cores,
It consists of a single carcass ply that is connected to both ends of the main body and has a folded portion that is folded around the bead core from the inside in the tire axial direction to the outside, and the folded portion passes through the sidewall portion from the bead core. By extending to the tread portion, the folded portion forms an overlapping portion in the tread portion which overlaps in the tire radial direction, and the bead core is a tire in which a belt-shaped ply in which two parallel steel cords are covered with topping rubber is used. The steel cord is formed by being wound in two or more rounds and three or less rounds in a radial direction, and a wire diameter d of the steel cord is 0.9 to 1.3 mm and a distance between the centers of the steel cords. Pitch p is 1.3 ~
It was 1.7 mm.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a motorcycle tire 1 (hereinafter referred to as a tire 1) includes a tread portion 2 having a tread surface 2a smoothly curved in an arc shape, and a sidewall portion 3 extending inward in the tire radial direction from both ends thereof.
And a bead portion 4 located at a radially inner end of each sidewall portion 3 in the tire radial direction.
It is mounted on the following motorcycle, preferably a motorbike.

The tire 1 has a toroidal carcass 6 extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3.

The carcass 6 includes a main body 6a extending between the pair of bead cores 5, 5, and a main body 6a.
Is formed from a single carcass ply 6A integrally having a folded portion 6b which is folded back from the inside to the outside in the tire axial direction around the bead core 5 and connected to both ends of the bead core 5. The carcass ply 6A has a bias structure in which, for example, carcass cords made of organic fibers are arranged at an angle of 25 to 70 degrees with respect to the tire equator C, and the organic fiber cords include nylon and polyester cords. It is preferably adopted. The cord fineness is 2 / 940dt
An ex fine thread is preferred.

The folded portions 6b, 6b on both sides of the carcass ply 6A extend from the bead core 5 to the tread portion 2 through the sidewall portion 3, so that the folded portions 6b are radially arranged in the tread portion 2 in the tire radial direction. Overlapping overlapping portions 7 can be formed. For this reason, in each side wall part 3, the carcass ply 6A overlaps in two layers, and the carcass cords intersect, thereby exhibiting appropriate rigidity and flexibility.

In the carcass ply 6A, the width RW of the overlapping portion 7 in the tire axial direction is, for example, 50 to 90%, preferably 60%, of the tire width SW which is the maximum width of the tire excluding marks, patterns, and the like. In this example, the value is set to about 63%. In such an overlapping portion 7, since the carcass ply 6A overlaps in three layers in the tread portion 2, the strength and durability of the tire can be sufficiently ensured.

The carcass 6 is a bead apex rubber 8 having a triangular cross section extending from the bead core 5 to the outside in the tire radial direction between the main body 6a and the folded portion 6b.
Is filled. Since the bead apex rubber 8 is made of a hard rubber as compared with, for example, the sidewall rubber disposed on the sidewall portion 3, the bending rigidity of the bead portion 4 can be increased. The bead apex rubber 8 is made of, for example, a relatively soft carcass ply 6.
The same rubber material as the topping rubber of A may be used.

The bead core 5 is a tape-shaped band-like ply 1 in which two parallel steel cords 9 and 9 are covered with a topping rubber G, as schematically shown in FIG.
0 is wound over two or more rounds and three or less rounds in the tire radial direction to form as shown in FIG. If the number of windings of the belt-like ply 10 is less than two turns, sufficient rigidity of the bead portion 4 cannot be obtained, and if it is more than three turns, the rigidity of the bead portion 4 is excessively increased and the rim assemblability deteriorates. Further, when three or more steel cords 9 are arranged in parallel, it becomes difficult to secure a large parallel pitch of the steel cords 9 with respect to the wire diameter as described later, and the width BW of the bead portion 4 tends to vary. Become.

In such a band-like ply 10, the winding position of the steel cord 9 is more stable because the interval between the steel cords 9 in the tire axial direction is uniform in advance, as compared with the case where one cord is spirally wound. In addition, it helps to reduce the variation in the width of the bead portion 4 after molding. In the present embodiment, the belt-shaped ply 10 has a horizontally long shape in a cross section orthogonal to the longitudinal direction thereof. Specifically, the width PW in the tire axial direction is 3.6 mm, and the thickness T is 1.45 mm. An example is shown below. By limiting the configuration of the bead core in this way, a bead portion 4 having a stable finished width can be obtained, and productivity can be improved.

The steel cord 9 has a wire diameter d of 0.9 to 1.3 mm and a parallel pitch p, which is the distance between the centers of the steel cords 9, of 1.3 to 1.7 mm. is necessary. That is, the steel cord 9
When the wire diameter d is less than 0.9 mm, 2 × 2 to 2 ×
In the bead core 5 having the three structures, the bead rigidity tends to decrease relatively. On the other hand, when the wire diameter d exceeds 1.3 mm, the rigidity of the bead portion 4 is excessively increased, and the rim assembly without a special tool is performed. Tend to be difficult.

When the parallel pitch p, which is the distance between the centers j and j of the steel cords 9 in the belt-like ply 10, is less than 1.3 mm, the parallel steel cords 9
Since the amount of the topping rubber G interposed between the steel cords 9 is reduced, the steel cords can easily approach each other during vulcanization in combination with the small diameter of the steel cords 9, and the bead portion 4
Tends to lead to manufacturing failures where the width of
On the other hand, when the parallel pitch p exceeds 1.7 mm, the rigidity of the bead core 5 decreases, and the steel cords 9, 9 arranged in parallel tend to approach the carcass ply, which tends to cause a break in the cords.

The width PW of the belt-like ply 10 is as follows.
, The width of the finished bead portion 4 is BW, the thickness of the carcass ply 6A is t, the inner diameter of the bead core 5 is φ, and the outer diameter of a cylindrical tire molding former around which the carcass ply is wound at the time of tire molding is D. In this case, it is preferable to obtain the value by the following equation (1). PW = {BW− (2t · φ / D)} × α (1) α: Adjustment coefficient and a variable of 0.95 to 1.05

Note that the bead core 5 is
May be formed in an annular shape by a bead core forming apparatus, or a belt-shaped plastic 10a may be directly wound around a predetermined position in the axial direction of the carcass ply 6A wound on the cylindrical former. 6A may be formed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The tire having the structure shown in FIG.
A 174P tire was prototyped based on the specifications in Table 1 (Examples, Comparative Examples 1 to 3), and a test of assembling each test tire with a rim of 17 × 1.40 was performed.
The rim assembly was performed by the test operator using only hands without using any special tool such as a tire lever, and the rim assembly was evaluated by the operator's feeling. The higher the score, the easier it is to assemble the rim. In addition, 100 test tires were manufactured, and the finished width of the bead portion at that time was measured to determine the defect occurrence rate. Table 1 shows the test results.

[0020]

[Table 1]

As shown in Table 1, in the tire of the embodiment,
It was confirmed that the rim was easy to assemble and the defect occurrence rate was significantly reduced.

[0022]

As described above, in the motorcycle tire according to the present invention, the bead width can be obtained stably while the rim assemblability without a special tool is improved, and the productivity is also improved. Can.

[Brief description of the drawings]

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

FIG. 2 is an enlarged partial sectional view showing a bead portion.

FIG. 3 is a cross-sectional view of the belt-like ply.

FIG. 4 is an enlarged partial sectional view showing a bead portion of a conventional motorcycle tire.

FIG. 5 is an enlarged partial cross-sectional view showing a bead portion of a conventional motorcycle tire.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 6a Body part 6b Folded part 7 Overlapping part 9 Steel cord 10 Strip ply

Claims (1)

[Claims] A motorcycle tire mounted on a motorcycle having a toroidal carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion and having a displacement of 100 cc or less. A single carcass ply integrally having a main body extending over a pair of the bead cores and a folded portion connected to both ends of the main body and bent around the bead core from inside to outside in the tire axial direction. And, the folded portion extends from the bead core to the tread portion via the sidewall portion to the tread portion, thereby forming an overlapping portion where the folded portions overlap in the tire radial direction in the tread portion, and the bead cores are arranged in parallel. A belt-like ply with two steel cords covered with topping rubber is placed in the tire radial direction. The steel cord is formed by being wound in two or more rounds and three or less rounds, and a wire pitch d of the steel cord is 0.9 to 1.3 mm, and a parallel pitch p which is a distance between the centers of the steel cords. A motorcycle tire having a thickness of 1.3 to 1.7 mm.