JPH05604A - Radial tire for motorcycle - Google Patents

Abstract

PURPOSE:To enhance turning stability during travel at high speed, and prevent generation of vibration of a car body. CONSTITUTION:A radial tire for motorcycle is provided with a carcass 6 extending from a tread part 2 through a side wall part 3 and returning around the bead core 5 of a bead part 4, and a belt layer 7 arranged outside the carcass 6. The belt layer 7 is formed by a belt ply in which composite cords 11 obtained by twisting together a high elastic filament 20 made of organic fiber and a low elastic filament 21 made of organic fiber are helically wound substantially parallel to the equatorial plane of the tire.

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 can improve cornering stability during high-speed running and prevent vehicle vibration.

[0002]

2. Description of the Related Art In recent years, with the development of highway networks,
Even motorcycles often run at high speed.

Such radial tires for motorcycles have conventionally been designed and manufactured on the basis of radial tires for four-wheeled vehicles, so that they can follow the turning performance and straight running performance peculiar to motorcycles. However, the steering stability is poor especially at high speeds.

The reason therefor is that the belt layer a conventionally provided to reinforce the tread portion has its cord b tilted by 15 to 30 ° with respect to the tire equator, as shown in FIG. Will be distributed. In the belt layer a in which the cord b is inclined in this way, for example, as shown in FIG. 11, a band d in which the cord b extends in the longitudinal direction is cut according to the inclination angle α of the cord b of the belt layer a, The parallelepiped block e is formed, and the edges f, f of the block e are formed.
A ply formed in a belt shape by butting and connecting the plies was used.

In the belt layer a thus formed, the abutting portions f, f pass obliquely with respect to the tire rotation direction, so that the abutting portions move from one tread end to the other tread end during traveling. However, since they do not land at the same time, the handling operation becomes unstable, which hinders straightness and the handling performance is poor even when turning, and these effects are particularly significant when driving at high speeds. And the problem of steering wheel shimmy (wobble) is likely to occur.

On the other hand, the belt cord of the belt layer is made of an aromatic polyamide to reduce the weight and enhance the hoop effect to improve the durability.

[0007]

However, the one using the aromatic polyamide has a smaller specific gravity than steel and can reduce the weight of the tire, but has a problem that the uniformity tends to decrease and the pattern noise is high.
Especially significant increase in noise in 10~12KH _Z.
The present invention is based on using a belt ply in which a composite cord obtained by twisting a belt layer with a high-elasticity filament and a low-elasticity filament is spirally wound, and has high-speed durability and steering stability without increasing pattern noise. It is an object of the present invention to provide a radial tire for a motorcycle, which is capable of improving and preventing vibration and saving energy.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a tread portion extends to a position forming the maximum width of a tire and extends from both ends thereof inward in a radial direction, and a side wall portion in a radial direction. A toroidal carcass that has bead portions located at both ends, and has both ends of a cord that extends through the tread portion and the side wall portion and is substantially parallel to the radial direction of the tire is folded around the bead core in the bead portion. , A belt layer arranged inside the tread portion and outside in the radial direction of the carcass is provided, while the belt layer is a composite cord in which a high elastic filament made of an organic fiber and a low elastic filament made of an organic fiber are twisted together. A motorcycle using at least one belt ply formed by a spiral winding arrangement substantially parallel to the equatorial plane of the tire. It is a radial tire use.

[0009]

The composite cord in which the belt layer is formed by twisting the high elastic filaments and the low elastic filaments can have the low elastic region below the inflection point and the high elastic region above the inflection point. Therefore, the elasticity corresponding to the elongation of the belt cord (about 3%) during the tire vulcanization process is higher than that formed by only the high elasticity cord when vulcanizing in the tire vulcanizing mold.
The inner pressure inside the raw tire can press the outer peripheral surface of the tire against the inner surface of the vulcanization mold along with the elongation of the composite cord, which facilitates the vulcanization molding of the tire while using the high elastic filament and the spiral winding of the composite cord to form the belt layer. Together with the formation, the tire accuracy is also improved. Therefore, noise can be reduced by improving the finishing accuracy of the tire.

When the tire is rotated at a high speed with high deformation,
Since the composite cord of the belt ply exhibits high elasticity, the hoop effect of the belt layer is improved, so-called lifting of the belt layer is prevented, and the occurrence of standing waves is suppressed, thereby improving the high-speed durability of the tire. However, vibration is suppressed and steering stability is improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the figure, a radial tire 1 for a motorcycle has a tread portion 2 extending to a position having the maximum width of the tire with an arch-shaped cross-sectional profile with the equator of the tire as a central vertex, and from both ends of the tread portion 2 inward in the tire radial direction. The sidewall portion 3 and the bead portion 4 located in the tire radial direction of the sidewall portion 3 are provided.
Is formed such that the length between the edges E1 and E2 of the is equal to the maximum width. Further, in the radial tire 1 for a motorcycle, a body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead portion 4 is provided with a winding portion 6b for winding up the bead core 5 from the inner side in the tire axial direction to the outer side. A carcass 6 and a belt layer 7 disposed inside the tread portion 2 and outside the carcass 6 in the radial direction.
Starting from the outside in the tire radial direction, a bead apex 9 extending between the body portion 6a of the carcass 6 and the body portion 6a and extending between the body portion 6a and the belt layer 7 is raised.

The carcass 5 is composed of at least one carcass ply having a radial array of carcass cords inclined at an angle of 70 to 90 degrees with respect to the tire equator C, and in this embodiment, one carcass ply. Is an organic fiber cord such as nylon, rayon, polyester or aromatic polyamide.

The winding portion 6a measures the winding height Ht from the bead bottom surface 15 by measuring the edges E1 and E of the tread portion 2.
Tread edge height H, which is the height from the bead bottom surface 15 of 2
It is set to 1.0 times or more and 1.2 times or less than s.

The winding height Ht is the tread edge height Hs.
If it is less than 1.0 times, the bending stress acting on the bead portion 4 cannot be absorbed and the rigidity of the bead portion 4 is insufficient, so that the durability is lowered, while if it exceeds 1.2 times, the tread shoulder portion SH is exceeded. The rigidity of the vehicle is increased, and the riding comfort during turning is reduced.

Further, in the present embodiment, the end portion of the winding portion 6b has an overlapping portion 16 overlapping both side portions of the belt layer 7. By providing such an overlapping portion 16, the movement of the carcass due to the deformation of the tire can be prevented, peeling of the end portion of the carcass 6 is prevented, and the durability of the tire is improved. The overlapping length L of the overlapping portion 15 is 10 mm or more and 20 mm or less. When the length L is less than 10 mm, the carcass 6 is displaced, and when the length L is 20 mm or more, the cost becomes high.

As shown in FIG. 2, the belt layer 7 has a high elastic filament 20 ... And a low elastic filament 21.
A composite cord 11 formed by twisting and is used.

The high elastic filament 20 is made of aromatic polyamide fiber, wholly aromatic polyester fiber, and strength of 15 g / d.
The above-mentioned polyvinyl alcohol fiber or carbon fiber having an elastic modulus of 1000 kg / mm ² , preferably 150
It is a fiber with a high elastic modulus exceeding 0 kg / mm ² . Further, the thickness is a relatively thin diameter of about 1000 to 3000 denier.

Further, as the low elastic filament 21,
Nylon fiber, polyester fiber, vinylon fiber, etc. having an elastic modulus of 1000 kg / mm ² or less, preferably 700
Those of less than kg / mm ² are used.

One or a plurality of such high-elasticity filaments 20 are simultaneously ply-twisted, and one or a plurality of low-elasticity filaments 21 ply-twisted in the same direction.
The composite cord 11 is formed by twisting and in the opposite direction. When using a plurality of high-elasticity filaments 20 and low-elasticity filaments 21,
Each one may be ply-twisted, or plural plies may be combined and ply-twisted. The composite coat 11 is shown in FIG.
As shown in FIG. 1, one of each of the high-elasticity filament 20 and the low-elasticity filament 21 may be twisted together, or one may be one and the other may be plural, or both may be twisted together. Thus, the composite cord 11 can be formed.

When a tensile force is applied to the composite cord 11 as described above, as shown in FIG. By stretching, the initial twist pitch P1 of the composite cord 11
Increases to the pitch P2 due to extension. This extension, as schematically shown in FIGS. 4 to 5 for the high-elasticity filament 20, causes the high-elasticity filament 20A, which was coiled in the initial state, to become the straight filament 20B by a predetermined extension. Therefore, from such a state, the original high elastic modulus of the high elastic filament 20 is exhibited. In this way, by winding the high-elasticity filament 20 in a spiral shape in advance, a low-elasticity region in which the elongation is relatively large between the spiral state of FIG. 4 and the straight state of FIG. 5,
It is clear from the state of FIG. 5 that a high elasticity region having a small elongation can be provided by further applying a load, and the straight state shown in FIG. 5 forms an inflection point of the elongation-stress curve. To do.

In the composite cord 11, the inflection point V is thus set so as to be located within the range of 3% or less of the elongation. The composite cord 11 is a twisted body of the high-elasticity filament 20 and the low-elasticity filament 21. Therefore, as shown in FIG. 3, the high-elasticity filament 20 and the low-elasticity filament 21 have a twist even when a load is applied. Therefore, the inflection point V is not remarkable as compared with the schematic cases of FIGS. The stress-elongation curve of the composite cord 11 is illustrated in FIG. In the figure, the curve a
Is a nylon 6.6 840d low elasticity filament 2
1 and curve b shows the elongation curve of the high elastic filament 20 made of 1000 d of aromatic polyamide. A curve c shows the case of the composite cord 11 in which one of these high-elasticity filaments 20 and two of the low-elasticity filaments 21 are twisted together. The curve c is located between the curve a and the curve b, and the inflection point V is in the range of elongation of 3%. In the composite cord 11, the inflection point V is 0 extension.
In this state, the tangent line S1 tangent to the curve and the tangent line S2 drawn to the curve c at the break point are defined as the intersections of the vertical lines passing through the intersections X.

The composite cord 11 has a high elastic region from the inflection point V to the break point and an inflection point V from the origin at which the elongation is zero.
And a ratio EH / EL of the elastic modulus EH in the high elastic region, which is the slope of the tangent line S2, and the elastic modulus EL in the low elastic region, which is the slope of the tangent line S1, is 4 to 8 It has a range. In such a composite cord 11, the thickness, number, and elastic modulus of high-elasticity filaments, the thickness, number, and elastic modulus of low-elasticity filaments are appropriately selected, and by adjusting the twisting conditions such as the filament angle, as shown in FIG. As shown in, the composite cord 11 that can satisfy the above range can be formed. In addition, the composite cord 11, the highly elastic filament 20,
It can also be adjusted by selecting the stretching process applied to the low-elasticity filament 21.

Since the inflection point V exists in the range of elongation of 3% or less, when the raw tire is mounted on the vulcanization mold and the raw tire is filled with the internal pressure during tire production, the internal pressure is increased. By means of the belt layer 7, the composite cord 11
By swelling due to the expansion of and the outer peripheral surface is pressed against the inner surface of the mold, the groove shape formed in the mold can be engraved on the tread portion 2. The swelling of the green tire due to the filling with the internal pressure is performed by the expansion of the composite cord 11 in the low elasticity region. Therefore, the inflection point V is set to be greater than 0 and the elongation is 3%.
The following range, preferably 1-3%, more preferably 1.
It is set in the range of 5 to 3%. The required elongation of the composite cord 11 in the mold due to the internal pressure filling is preferably located near the inflection point V. This makes it possible to suppress the inflation of the molded tire and the expansion of the tire due to the centrifugal force acting at the time of high-speed rotation, in the high elasticity region.
Therefore, the elastic modulus EH in the high elastic region and the elastic modulus E in the low elastic region are
The ratio EH / EL with L is set to 4-8. When it is 4 or less, the above-mentioned suppressing effect is poor, and when it exceeds 8, it is unnecessary from the viewpoint of tire balance.

In the present embodiment, the belt layer 7 is formed by forming a strip-shaped and long narrow width ply 10 using the composite cord 11 and then spirally winding the small width ply 10 around the carcass 6. Is forming.

As shown in FIG. 7, one narrow ply 10 or a plurality of narrow plies 10, two in this embodiment, a composite cord 11 is embedded in a topping rubber 12.

In this embodiment, the narrow ply 10 has a flat rectangular shape, and the distance N from the side edge 10a to the center of the composite cord 11 near the side edge 10a is the belt cords 11, 11.
The pitch P is set to 1/2 or less.

In the present embodiment, the narrow ply 10 is, as shown in FIG. 8, one of the tread ends E1 and E2 shown in FIG.
As shown by the arrows in FIG. 8, the tire equator C is defined as points F1 and F2 that are located radially outside the neighboring carcass 6.
The ply pieces 7a and 7b are formed by inclining toward the tire equator C at a small angle with respect to the tire equator C as the end point G, and spirally winding the ply pieces 7a and 7b in reverse. In this embodiment, when the small width ply 10 is wound, the adjacent side edges 10a and 10a are wrapped and wrapped as shown in FIG. Therefore, it is possible to prevent looseness of the small width ply 10 at the starting point, and it is possible to prevent peeling of the small width ply 10 at the edge of the belt layer 7 to which a large force acts during running.

As in this embodiment, the inclination angles are opposite to each other.
When the two ply pieces 7a and 7b are formed, it becomes possible to wind the two narrow width plies 10 and 10 on the carcass 6 at the same time.
7b can be formed.

Further, since the ply pieces 7a and 7b are wound around both end edges F1 and F2 of the belt layer 7, the winding start point of the narrow width ply 10 can be firmly fixed, and the winding end point is the belt layer. Since it is not located at the edge of 7,
It is possible to prevent the belt layer 7 from coming loose from the winding end. On the other hand, the other ply pieces 7a and 7b are
The narrow plies 10 may be wound in the same direction,
Further, the belt layer 7 can also be formed by winding one small width ply 10 starting from one end edge of the belt layer 7 and ending at the other end edge.

The width dimension of the belt layer 7 in the axial direction of the tire is set to 0.7 times or more and 1.0 times or less of the tread width WT which is the distance between the edges E1 and E2 of the tread portion 2. preferable.

The bead apex 9 is formed of a relatively soft rubber having a JISA hardness of 50 to 65 degrees, and the terminal end K of the rubber separates 0.25 times the tread width WT from the tire equator C 1 /. It is located inside the four points P and outside the ⅛ point Q that separates 0.125 times the tread width WT from the tire equator C.

If the rubber hardness is 50 degrees or less, the rigidity of the bead portion 4 and the side wall portion 3 becomes insufficient, and the bead portion 4
In the case where the waist is broken, steering stability is poor when going straight or turning, while when it exceeds 65 degrees, the rigidity is high and the handleability is deteriorated.

Also, the end K of the bead apex 9 is 1 as described above.
When it is located outside the / 4 point P, rigidity reinforcement of the tread portion 2 is incomplete, weave is likely to occur at high speed straight ahead, and cornering when turning with a camber angle. Power is insufficient and grip is reduced. On the contrary, when the terminal end K is located on the tire equator side from the 1/8 point, the rigidity of the central portion of the tread in the vicinity of the tire equator C becomes excessive, cornering power increases, and high-speed running performance deteriorates.

(Specific example) Tire size 170/60 VR
For 17 tires, tires having the configuration shown in FIG. 1 and having the specifications (specific examples 1, 2, 3) shown in Table 1 were prototyped and tested. For comparison, conventional tires (Comparative Examples 1 and 2) were also tested. The test conditions are as follows.

1) High-speed straight running stability and high-speed turning stability A trial tire was mounted on the rear wheel of the motorcycle, and the motorcycle was tested on a test road for 200 to 270 km /
The vehicle was run in Hr and evaluated by the feeling of the test driver. The numerical values in the table are shown as indices with Comparative Example 1 being 100. The larger the value, the better.

In the test, the tire size was 120 / 70R / 17 for the front wheels in both the specific example and the comparative example, and the belt layer was equipped with a tire having the structure shown in FIG. did.

[0037]

[Table 1]

[0038]

[Table 2]

As a result of the test, it was found that the specific example is superior to the comparative example in each test item.

[0040]

As described above, in the radial tire for a motorcycle according to the present invention, each of the above-mentioned components is organically integrated, the grip at the time of turning can be improved, the high-speed turning performance can be improved, and the noise can be reduced. .

[Brief description of drawings]

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

FIG. 2 is a front view illustrating a composite cord.

FIG. 3 is a front view showing the extended state.

FIG. 4 is an early stage of a high modulus filament.

FIG. 5 is a stretched state of a front view schematically showing the state.

FIG. 6 is a diagram showing an example of an elongation curve of a cord.

FIG. 7 is a perspective view showing an example of a small width ply forming a belt ply.

FIG. 8 is a cross-sectional view showing winding of a narrow ply.

FIG. 9 is a cross-sectional view showing winding of a narrow ply.

FIG. 10 is a plan view showing a conventional belt ply.

FIG. 11 is a plan view showing a conventional belt ply.

[Explanation of symbols]

2 tread section 3 Side wall part 4 bead section 5 bead core 6 carcass 6A main body 6B winding section 7 Belt layer 10 narrow ply 11 composite code 12 topping rubber 20 High elasticity filament 21 Low elasticity filament C tire equator E1, E2 edge K termination

Claims (2)

[Claims] 1. A sidewall portion extending to a position where a tread portion has a maximum tire width and extending radially inward from both ends thereof, and a bead portion positioned at both radial ends of the sidewall portion. And a toroidal carcass in which both ends of a cord that extends substantially parallel to the tire radial direction through the tread portion and the side wall portion are folded back around the bead core in the bead portion, and the inside of the tread portion and the radius of the carcass. While providing a belt layer disposed on the outside in the direction, the belt layer is a composite cord in which a highly elastic filament made of an organic fiber and a low elastic filament made of an organic fiber are twisted together and is substantially parallel to the equatorial plane of the tire. A radial tire for a motorcycle, comprising at least one belt ply formed in a spiral winding arrangement. 2. The composite cord has a low elastic region whose stress-elongation curve extends from the origin to an inflection point and a high elastic region exceeding the inflection point, and the inflection point has an elongation of 3% or less. Elastic modulus EH in the high elastic range and elastic modulus EL in the low elastic range
The radial tire for a two-wheeled vehicle according to claim 1, wherein the ratio EH / EL is 4 to 8.