JPH08216608A - Tire for motorcycle - Google Patents

Abstract

PURPOSE: To provide a tire for motorcycle which can reduce its weight while utilizing its excellent riding comfortableness and maintaining stability in high speed running and turn. CONSTITUTION: A tire for motorcycle is provided with a carcass 6 having a bias structure in which a periphery of a bead core 5 in a bead section 4 is folded back through a side wall section 3 from a tread section 2 and a plurality of carcass plies 6A to 6C which are arranged in topping rubber by tilting cord in a scope of angles of 25 to 60 degrees for an equator of the tire are overlapped and a braker layer 7 made of braker ply which is embedded in the topping rubber by tilting the cord in the same scope of angles as those of the carcass 6. The topping rubber of the carcass plies 6A to 6C is made of a rubber component which contains short fibers having 5 to 30 weight parts for 100 weight parts of rubber component and carbon black whose iodine absorption rate in 30 to 60 weight parts is 35 to 80mg/g. The short fibers are oriented along the longitudinal direction of the carcass cord.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire for a motorcycle, which can make use of the excellent riding comfort of a bias structure tire and reduce the tire weight while maintaining high-speed running stability and turning stability.

[0002]

2. Description of the Related Art A motorcycle produces a cornering force due to a tire slip angle and a camber thrust due to a camber angle at the time of turning to overcome a centrifugal force to make a turn.

Therefore, in a motorcycle tire, the tread surface is formed outward with a small radius of curvature, and the tread width, which is the axial distance between the edges of the tread portion, forms the maximum tire width. It has a completely different structure from the tires for automobiles.

[0004] Such a motorcycle tire can be mainly classified into a bias ply tire, a belted bias tire, a radial ply tire, etc. depending on the carcass structure. In particular, the bias structure motorcycle tire is a tire having a radial structure. Compared with, the carcass can be easily expanded and contracted locally, resulting in excellent riding comfort, and because the tire side parts can be appropriately reinforced, the stability is high when the vehicle is tilted. Is high.

[0005]

However, a tire having such a bias structure has a smaller cornering force due to the local shrinkage of the tread contact surface than a radial ply tire having a tough belt layer in the tread portion. Poor steering stability when turning, and low high-speed durability.

[0006] From such an actual condition, in the tire for the motorcycle having the bias structure, the amount of the material used is increased so that the tire strength can be maintained at about 2 to 4 times the standard value, especially by using a large diameter cord for the carcass cord. However, there is a problem that the weight of the tire becomes large.

The present invention has been devised in view of the above problems, in which the topping rubber of the carcass ply contains short fibers and carbon black whose iodine adsorption rate is regulated, and the short fibers are used as a carcass. A tire for a motorcycle, which is basically oriented along the longitudinal direction of the cord, and which utilizes the excellent riding comfort of a tire having a bias structure and can reduce the tire weight while maintaining steering stability and high-speed durability. It is an object.

[0008]

According to the present invention, the tread width, which is the distance between the tread portion edges in the tire axial direction, has the maximum tire width, and the tread surface in the meridional section of the tire has an outwardly convex arc shape. A curved motorcycle tire, which is folded back around the bead core of the bead portion from the tread portion through the sidewall portion, and the cords are arranged in the topping rubber at an angle range of 25 to 60 degrees with respect to the tire equator. A carcass of a bias structure in which a plurality of the carcass plies are stacked in a direction in which the cords intersect with each other, the carcass is arranged radially outside and inside the tread portion, and the cords are inclined in the same angle range as the carcass. And a breaker layer made of breaker plies embedded in a topping rubber. The rubber is composed of a rubber composition containing 5 to 30 parts by weight of short fibers and 30 to 60 parts by weight of carbon black having an iodine adsorption rate of 35 to 80 mg / g based on 100 parts by weight of the rubber component. A motorcycle tire, characterized in that the short fibers are oriented along the longitudinal direction of the carcass cord.

The breaker ply topping rubber has a short fiber content of 5 to 30 parts by weight and an iodine adsorption rate of 35 to 8 parts by weight of 30 to 60 parts by weight per 100 parts by weight of the rubber component.
The short fiber may be composed of a rubber composition containing 0 mg / g of carbon black, and the short fiber may be oriented along the longitudinal direction of the breaker cord. As the short fiber, nylon short fiber is preferable.

[0010]

In the motorcycle tire of the present invention, the topping rubber of the carcass ply has the short fibers oriented along the longitudinal direction of the carcass cord. As a result, the elasticity of the ply along the longitudinal direction of the carcass cord can be increased, resulting in an increase in lateral bending rigidity of the car cast red portion and a greater cornering force when a tire is given a slip angle than the conventional steering stability during turning. Improve.

Further, at the overlapping surface of the overlapping carcass plies, the short fibers themselves can be crossed with each other, so that the rigidity of the carcass ply can be increased, high-speed durability can be improved, and particularly, the carcass cord can have a smaller diameter than before. The cord can be used, and the total number of denier cords used for the carcass can be reduced. As a result, the tire weight can be reduced.

As a result of enhancing only the longitudinal rigidity of the carcass cord, the short fiber expands and contracts in a so-called pantograph shape as in the case of the carcass cord, and it is possible to easily locally deform the carcass at the ground contact portion of the tread as in the conventional case. It is possible to maintain excellent riding comfort performance as compared with a radial structure tire.

By using carbon black having an iodine adsorption amount of 30 to 85 mg / g as the carbon black, the ply topping rubber reinforcement can be enhanced and the tire strength can be improved. In the present invention, by orienting the short fibers in the direction of the carcass cord, it is possible to increase the elastic modulus in the direction along the cord, the hardness of the entire rubber, and the amount of carbon black that enhances heat buildup within the regulation range. Thus, the weight can be reduced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The motorcycle tire 1 of the present invention includes sidewall portions 3 extending inward in the radial direction from both ends of the tread portion 2, and a bead portion 4 continuous to the inside in the radial direction of the sidewall portion 3, and the tread portion. Edge E,
The tread width TW, which is the distance in the tire axial direction between E, forms the tire maximum width, and the tread surface 2A in the tire meridional section is curved by a combination of a single or a plurality of arcs that are convex outward.

The motorcycle tire 1 further includes a carcass 6 that passes from the tread portion 2 through the sidewall portion and folds back around the bead core 5 of the bead portion 4, and inside the tread portion 2 and radially outward of the carcass 6. Breaker layer 7 arranged
In this example, a bead apex 8 made of hard rubber is provided on the outer side in the radial direction of the bead core 5 and extends outward in the tire radial direction between the main body portion 6a and the folded-back portion 6b of the carcass 6. The bead portion 4 may be provided with an appropriate reinforcing member such as a chafer. $ The carcass 6 has a cord of 25 to 60 with respect to the tire equator.
Within the angle range of degrees, in this example, a plurality of carcass plies 6A, 6B, 6C, which are inclined in the topping rubber at an angle α of 25 °, in this example, are stacked in a direction in which the cords intersect each other. Form a bias structure.

The cord of each of the above-mentioned ply splies uses nylon in this example, but other than this, organic fiber cords such as rayon, polyester, aromatic polyamide, etc. can be appropriately used and are reinforced by short fibers described later. As a result, for example, when the nominal dimension of the tire cross-section exceeds 120, the conventional 2 / 1890d nylon cord is used, but the small diameter cord of 2 / 12260d or less is driven, for example, 31 to 39 per 5 cm. The number of tires can be used, the amount of material used for the carcass cord can be reduced, and the weight of the tire can be reduced.

Next, the carcass plies 6A, 6B, 6
C can terminate stress concentration at the turn-back end by terminating the turn-back part 6b at different height positions from the bead base line BL such as heights h1, h2, and h3. The folding height h1 of the carcass ply 6A located closest to the inner side of the tire is 0.5 times or more the tire cross-section height, which is about 0.6 times in this example.

The breaker layer 7 is arranged radially outside of the carcass 6 and inside the tread portion, and has a cord in the same angular range as that of the carcass, preferably 35-60.
At least 1 embedded in topping rubber tilted at
Sheet, in this example, two breaker plies 7A and 7B whose cords intersect with each other, protects the carcass against the impact from the road surface, and the carcass 6 is directly damaged by the tread.
Can be reached.

The breaker plies 7A and 7B employ nylon cords for their cords, like the carcass, but other than these, organic fiber cords such as rayon, polyester, aromatic polyamide and the like can be used as appropriate, which is preferable. Is preferably the same cord material and cord fineness as the carcass cord. It should be noted that the number of driving is 5 cm, 31
Approximately 39 pieces.

In the breaker layer 7, the breaker width BW, which is the distance in the tire axial direction between the outermost ends in the tire axial direction, is preferably about 0.8 to 0.95 times the tread width TW. In the breaker ply 7A, it is desirable to arrange the breaker cords in such a direction as to intersect the carcass cords of the outermost carcass ply 6C of the carcass ply in the angle range.

Next, in this example, the carcass ply 6A,
The 6C topping rubber and the breaker ply 7A topping rubber each use a rubber composition containing short fibers and carbon black.

The short fibers used in this embodiment are nylon short fibers, but in addition to these, organic fibers such as polyester, aramid, rayon and vinylon, as well as inorganic materials such as metal fibers, whiskers, boron and glass fibers. These may be used alone or in combination of two or more, and more preferably, the short fibers may be surface-treated in order to improve the adhesiveness with the rubber component.

The short fibers have a diameter d of 0.3 to 0.5.
μm, the length 1 is 300 to 500 μm, and therefore the diameter-length ratio (l / d) is an extremely thin and short fiber body of about 1000, and the topping rubber of the carcass ply and breaker ply are both Rubber component of short fiber of 10
It is necessary to contain 5 to 30 parts by weight with respect to 0 parts by weight.

If the amount of the short fibers is less than 5 parts by weight with respect to 100 parts by weight of the rubber component, the elastic modulus in the direction along the longitudinal direction of the cord cannot be increased even if the short fibers are oriented, While it cannot be expected to improve steering stability, if the amount exceeds 30 parts by weight, calendering tends to be difficult, and due to the large amount of short fibers, the topping rubber impairs the adhesion to the tire cords and increases the ply durability. This is because the deterioration is caused, and from this viewpoint, it is more preferable to add 15 to 25 parts by weight.

Next, examples of the carbon black include HAF, FEF, GPF and the like which are commercially available from Showa Cabot Co., Mitsubishi Chemical Co., Ltd., Tokai Carbon Co., etc., and have an iodine adsorption amount of 35 to 80 mg / g. By using these, the rubber reinforcing property is enhanced and the rubber heat generation property is reduced while contributing to the improvement of the tire strength.

The amount of iodine adsorbed on the carbon black is 3
If it is less than 5 mg / g, the rubber-reinforcing property is low, and the strength and cut resistance are both inferior. On the contrary, if it exceeds 80 mg / g, the heat generation is high and the rolling resistance is deteriorated. Such iodine adsorption amount is
For example, it is measured according to the measuring method described on page 438 of "Carbon Black Handbook".

The amount of carbon black added is 30 to 60 parts by weight, preferably 40 to 50 parts by weight, based on 100 parts by weight of the rubber component. When the content of the carbon black is less than 30 parts by weight, the effect of reinforcing the rubber is poor, and when it exceeds 60 parts by weight, the heat generation property of the rubber is high and the rolling resistance is large.

In the present invention, by orienting the short fibers in the longitudinal direction of the carcass cords and breaker cords, the cord direction can be made to have a high elastic modulus, and the amount of carbon black that enhances the hardness and heat buildup of the entire rubber can be reduced. You can.

Examples of the rubber composition of the topping rubber for such carcass ply and breaker ply include those shown in Tables A to D.

[0030]

[Table 1]

The short fibers are oriented along the longitudinal direction of the cord in each ply. It should be noted that "to orient the short fibers along the longitudinal direction of the cord" means that 70% or more of the short fibers contained in the ply are oriented at an angle of ± 15 ° with respect to the longitudinal direction of the cord. Defined as being

The orientation of such short fibers is carried out by kneading a rubber composition containing the above short fibers by an ordinary method such as an extruder or a calender, and extruding it, and topping it onto each cord of carcass and breaker. It can be done easily.

The short fibers can increase the elastic modulus in the longitudinal direction of the carcass cord of the carcass 6 without impairing the riding comfort of the tire having the bias structure, thereby improving the steering stability and the surface of the overlapping carcass plies. As described above, the short fibers intersect with each other to increase the carcass rigidity and the high-speed durability as described above.

As a result of the short fibers being oriented in the carcass ply, they effectively reinforce the sidewalls and beads of the tire as well, especially at the portion where the main body 6a of the carcass 6 and the folded-back portion 6b are in contact with each other. In addition, it is possible to prevent the so-called sensation of being soaked at the time of high-speed turning, such as obtaining a multi-intersection portion of short fibers.

In this example, the topping rubber of the breaker ply 7A is also shown to contain short fibers, but it goes without saying that the breaker ply may be a topping rubber containing no short fibers. The present invention can be modified into various modes such as using four or more plies.

[0036]

[Examples] Tires (Examples 1 to 7) having a tire size of 140 / 70-17 and having the configurations and specifications shown in FIG. , Tested for its performance. A conventional tire (conventional example) in which the rubber composition E containing no short fiber was used as a topping rubber for carcass ply and breaker ply and a tire having a configuration outside the present invention (comparative examples 1 to 4) were also tested. The performance was compared. In addition,
The tread rubber of the tread portion 2 of the tire used for the test,
Table 2 shows each rubber composition constituting the sidewall rubber of the sidewall portion and the bead apex.

[0037]

[Table 2]

The test conditions are as follows. B) Steering stability, riding comfort, and feeling of being worn. Each trial tire is mounted on the rear wheel of the actual vehicle, and a 110 / 70-17 size standard product (cross belt) is mounted on the front, and judgment is made based on the driver's feeling. At the same time, the index was evaluated with the conventional example being 100. In each case, the larger the value, the better.

B) High-speed durability The high-speed durability was tested in accordance with the high-speed durability test specified in Section 5.3 of JISK6366-1982, and the judgment was made based on the total running distance until the tire was damaged.
It is displayed with the index. The larger the value, the better.

C) Tire Strength The tire strength was tested in accordance with the tire strength test specified in Section 4.2.1 of JISK6366-1982, and the tire was expressed as an index with the breaking energy of the conventional example being 100. The larger the value, the better.

D) Tire weight The weight per tire is shown as an index with the conventional example being 100. The smaller the value, the lighter the weight of the tire. The test results are shown in Table 3.

[0042]

[Table 3]

As a result of the test, the tires of Examples 1 to 4 have various running performances and tire strengths equal to or higher than those of the conventional examples and Comparative Examples 1 to 6, while the tire weight is light. It was confirmed that it could be transformed. The reduction of the tire weight of each tire of the example is based on the fact that the topping rubber is a short fiber and the reinforcement of carbon black enables the reduction of the cord diameter in the carcass and breaker layers, and the total denier of the carcass is reduced. In particular, it was confirmed that the cord fineness of Examples 3 and 4 or less, and that the number of cords to be impressed was 31 to 39 per 5 cm.

[0044]

As described above, the motorcycle tire of the present invention makes use of the excellent riding comfort of the bias structure tire, and reduces the weight of the tire while maintaining high-speed running stability and turning stability. sell.

[Brief description of drawings]

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

FIG. 2 is a developed plan view showing an arrangement of a carcass and breaker layers.

[Explanation of symbols]

 2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 6A, 6B, 6C carcass ply 7 breaker layer 7A breaker ply C tire equator E tread edge

Claims (3)

[Claims] 1. A motorcycle tire in which the tread width, which is the distance between the tread edge edges in the tire axial direction, is the maximum tire width, and the tread surface in the tire meridian section is curved in an outwardly convex arc shape. A plurality of carcass plies arranged in a topping rubber by folding back around the bead core of the bead portion from the tread portion through the sidewall portion and inclining the cord in an angle range of 25 to 60 degrees with respect to the tire equator. A carcass having a bias structure in which cords are superposed in a direction intersecting with each other, and a breaker which is arranged radially outside and inside the tread portion of the carcass and in which the cords are inclined in the same angle range as that of the carcass and embedded in a topping rubber. And a breaker layer made of ply, and the topping rubber of the carcass ply has a rubber component 10
5 to 30 parts by weight of short fibers and 0 to 30 parts by weight
A motorcycle comprising a rubber composition containing 60 parts by weight of carbon black having an iodine adsorption rate of 35 to 80 mg / g, wherein the short fibers are oriented along the longitudinal direction of the carcass cord. Tires. 2. The breaker ply topping rubber comprises:
With respect to 100 parts by weight of the rubber component, 5 to 30 parts by weight of the short fibers and 30 to 60 parts by weight of the iodine adsorption rate are 35 to 80 m.
The tire for a motorcycle according to claim 1, comprising a rubber composition containing g / g of carbon black, and the short fibers being oriented along the longitudinal direction of the breaker cord. 3. The motorcycle tire according to claim 1, wherein the short fibers are made of nylon short fibers.