JP2554218B2 - Radial tires for motorcycles - Google Patents

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 capable of improving straight running stability and turning performance by lowering the rigidity of the tread portion in the central portion and increasing the tread shoulder portion.

[0002]

2. Description of the Related Art In recent years, with the improvement of highway networks, even motorcycles are required to have improved performance for high-speed running.

Such a motorcycle tire has been conventionally designed and manufactured based on a radial tire for a four-wheeled vehicle, so that it cannot follow the turning peculiar to the two-wheeled vehicle in which the vehicle body is tilted. , Inferior turning performance and durability. It also lacks stability when traveling straight ahead.

Conventionally, in a high-speed motorcycle tire, the tire tread portion is repeatedly deformed as the vehicle travels, so that the belt layer is prevented from moving outside the belt layer in order to prevent the peeling. A band layer made of aromatic polyamide was provided to increase the rigidity of the tread portion.

[0005]

However, when the reinforcing layer b is uniformly provided on the outer side of the belt layer a as shown in FIG. 10, the rigidity of the tread shoulder portion is increased and the vehicle leans like turning. The cornering power is increased when the vehicle is traveling as a result, so that the grip performance and stability when the vehicle is inclined are improved. However, the cornering power of the central part of the tread is also increased at the same time, and the straight running stability at the time of high speed running is reduced. Therefore, as a motorcycle tire capable of traveling at high speed, it is preferable to form a tread portion by giving a difference in rigidity to both parts, and in a low load region where the stress applied to the belt cord in straight running is lower than that in turning. By functioning as a low elasticity cord with high elongation and as a high elasticity cord during turning when high stress acts, it is possible to reduce cornering power when going straight and to exert high camber thrust during turning. It was found that straight running stability at high speed and turning performance can be improved at the same time. In addition, it has been found that the separation of the belt layer end can be prevented and the high speed running property can be further improved.

According to the present invention, the belt ply cord forming the belt layer is a composite cord composed of high-elasticity filaments and low-elasticity filaments, and at least one of the plies is formed as a folded ply.
An object of the present invention is to provide a radial tire for a motorcycle, which has excellent durability even when traveling at high speed, and which can improve straight running stability at high speed and turning stability at turning.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a sidewall from a tread portion having a cross-sectional shape that extends in an arc shape on both sides in the meridian direction from the equatorial plane of the tire and has a straight line width between the both ends that is the maximum width of the tire. Carcass consisting of one or more carcass plies having carcass cords made of organic fibers folded back around the bead core of the bead part and inclined at an angle of 70 ° to 90 ° with respect to the tire equator, and a tread part And a band layer disposed radially outside of the carcass, and the belt layer disposed radially outside of the carcass, the belt layer being disposed adjacent to the carcass. A belt ply and a second belt ply disposed outside the first belt ply, wherein the first belt ply is provided on both sides of the base adjacent to the carcass. Using a folded ply having a folded-back portion that wraps around both ends of the folded ply, the band layer extends from the tire equator over the inner end of the folded portion and is arranged substantially parallel to the tire equator. In addition, the belt layer and the band layer are radial tires for a motorcycle using a belt ply or a band ply made of 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.

[0008]

Since the tread portion is reinforced by the belt layer including the first and second belt plies and the band layer including the band ply, the rigidity of the tread portion is increased and the durability can be improved.

Further, since the first belt ply is a fold ply that wraps both ends of the second belt ply, in the tread portion, there is a difference in rigidity such that the cornering force is smaller in the central portion of the tread than in the tread shoulder portion. Exist. In addition, the belt cord adopts a composite cord that functions as a low elastic cord when traveling straight and as a high elastic cord when turning. Therefore, at high speeds,
While running stability is improved when going straight, at the time of turning when the tread shoulder section touches the ground, by improving both grip performance and running stability, driving stability is improved both when going straight and when turning, and Make it possible to continuously drive at high speed on the circuit. Also, since a band layer made of a band ply extending from the tire equator over the inner end of the folded portion is provided on the outside of the belt layer,
It is possible to prevent peeling of the end portion of the belt layer caused by repeated deformation of the tire during high-speed running, and further improve durability.

[0010]

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 includes a tread portion 2, a sidewall portion 3 extending from both ends thereof inward in the tire radial direction, and a bead portion 4 located at an inner end of the sidewall portion 3 in the tire radial direction. Also, the radial tire 1 for a motorcycle has a bead core 5 of a bead portion 4 passing through the tread portion 2 through the sidewall portion 3.
A carcass 6 that folds back from the inner side in the tire axial direction to the outer side, a belt layer 7 disposed inside the tread portion 2 and radially outside the carcass 6, and a band disposed outside the belt layer 7 in the radial direction. Layer 9 and bead core 5
The bead apex 10 having a triangular cross section is erected on the outer side in the radial direction of the tire.

The carcass 5 is composed of at least one carcass ply, and in the present embodiment, two carcass plies, each having a radial array of carcass cords inclined at an angle of 70 to 90 ° with respect to the tire equator C. Is an organic fiber cord such as nylon or aramid.

The belt layer 7 includes a first belt ply 11 arranged adjacent to the carcass 6 and a second belt ply 12 arranged outside the first belt ply 11.
And

The first belt ply 11 and the second belt ply 12 each have 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 with respect to the tire equator C in an amount of 15 to 30. The cords as the belt ply 11 are arranged side by side at an angle of .degree.

The first belt ply 11 is a carcass 6
The second belt ply 12 on both sides of the base 11A adjacent to the
The first belt ply 11 is formed as a fold ply in such a manner as to have the folded-back portions 11B that wrap around both end portions F, F and are folded back toward the tire equator C.

In the present embodiment, the second belt ply 12 has a distance L1 from the tire equator C at the end F thereof.
Is 0.35 times or more and 0.45 times the tread width TW, which is the distance between the tire axial end edges E1 and E2 of the tread portion 2.
The range is set to double or less. Also the first belt ply 1
In the present embodiment, the distance L2 between the inner end G, which is the end of the folded portion 11B facing the tire equator C, and the end F of the second belt ply 12, is the tread width TW.
The range is 0.20 times or more and 0.25 times or less.

By setting the length of the folded-back portion 11B as described above, the folded-back portion 11B is located inside the tire contact surface when the vehicle is running on a slope. The band layer 9 uses two inner and outer band plies 14 and 15. The inner band ply 14 is formed by winding a strip-shaped and long narrow width ply 20 around the belt layer 7 in this embodiment. Similarly to the inner band ply 14, the outer band ply 15 is formed by winding the small width ply 20 on the outer side of the inner band ply 14.

As shown in FIG. 3, the narrow width ply 20 is formed by embedding one or a plurality of parallel cords 21, two in this embodiment, in a topping rubber 22. A composite cord similar to the belt ply is used.

In the inner band ply 14, the small width ply 20 is folded back from the tire equator C to the one end E1 side.
A point that exceeds the inner end G of the folded portion 11B on the other end edge E2 side from the tire equator C from left to right in FIG. 1 with the starting point H1 on the circumferential surface of the folded portion 11B that exceeds the inner edge G of 1B. Is defined as the end point H2 and is wound substantially parallel to the tire equator C in a spiral shape. In this embodiment,
When the small width ply 20 is wound, as shown in FIG. 4, the small width ply 20 is wrapped around the opposing side edges 20a, 20a and wound to prevent the small width ply 20 from loosening.

The above-mentioned band ply 14 is the belt layer 7
The overlapping length L3 with the folded-back portion 11B is preferably 10 mm or more in order to prevent the folded-back portion 11B from being displaced.

The outer band ply 15 is formed by spirally winding the narrow width ply 20 from the other end edge E2 side as a starting point, that is, in a spiral opposite to that of the inner band ply 14. In addition, the outer band ply 15 has its width measured according to the inner band ply 14
The width of the inner band ply 14 is larger than that of the inner band ply 14, and both sides of the outer band ply 15 cover the starting point H1 and the ending point H2 of the inner band ply 14.

The inner band ply 14 and the outer band ply 15 are formed as a sheet body in which a plurality of band cords arranged in parallel are covered with a topping rubber in the same manner as the belt ply in place of the spiral winding of the narrow ply. You may.

When the small width ply 20 is wound and formed in the tire circumferential direction as in the present embodiment, a seam in a direction intersecting with the tire circumferential direction does not occur, so that the running stability during running is further enhanced. The traveling speed can be further increased.

As shown in FIG. 5, the composite cord 21 used for the belt layer and the band layer comprises a high elastic filament 30 ... And a low elastic filament 31.

The high elasticity filament 30 is made of aromatic polyamide fiber, wholly aromatic polyester fiber, and has a strength of 15 g / d.
The above-mentioned polyvinyl alcohol fiber or carbon fiber, etc., having an elastic modulus of 1000 kg / mm ² , preferably 150
Fibers with a high elastic modulus exceeding 0 kg / mm ² are used. Further, the thickness is a relatively thin diameter of about 1000 to 3000 denier.

Further, as the low elasticity filament 31, nylon fiber, polyester fiber, vinylon fiber, etc.,
Elastic modulus is 1000 kg / mm ² or less, preferably 700 kg /
mm ² or less is used.

One or a plurality of such high-elasticity filaments 30 are simultaneously twisted, and one or a plurality of low-elasticity filaments 11 twisted in the same direction.
The composite cord 21 is formed by twisting and in the opposite direction. When using a plurality of high elastic filaments 30 and low elastic filaments 31,
The ply-twisting may be carried out for each one, or the plural plies may be combined and ply-twisted. The composite cord 21 is shown in FIG.
As shown in FIG. 1, one of each of the high elastic filament 30 and the low elastic filament 31 may be twisted together, or one may be one and the other may be plural, or both may be twisted together. The composite cord 21 can also be formed by.

When a tensile force is applied to the composite cord 21 as described above, as shown in FIG. Further, the initial twist pitch P1 of the composite cord 21 due to the elongation.
Increases to the pitch P2 due to elongation. This extension, as schematically shown in FIGS. 7 and 8 for the high-elasticity filament 30, the high-elasticity filament 30A, which was coil-shaped in the initial state, becomes a straight filament 30B by a predetermined extension. Therefore, from such a state, the original high elastic modulus of the high elastic filament 30 is exhibited. In this way, by winding the high-elasticity filament 30 in a spiral shape in advance, a low-elasticity region in which the elongation is relatively large between the spiral state of FIG. 7 and the straight state of FIG. It is obvious that a high elastic region with a small elongation can be provided by further applying a load from the state of No. 8, and the straight state shown in FIG. 8 forms an inflection point of the elongation-stress curve. .

In the composite cord 21, the inflection point V is thus set so as to be located within the range of 7 to 11% of the elongation. The composite cord 21 is a twisted body of the high-elasticity filament 30 and the low-elasticity filament 31. Therefore, as shown in FIG. 6, the high-elasticity filament 30 and the low-elasticity filament 31 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 21 is illustrated in FIG. In the figure, curve a represents the low elasticity filament 31 of nylon 840d,
Curve b shows the elongation curve of the 1000 d high-elasticity filament 30 made of an aromatic polyamide. The curve c shows the case of the composite cord 21 in which one high elastic filament 30 and two low elastic filaments 31 are twisted. It can be seen that the curve c is located between the curve a and the curve b, and the inflection point V is in the range of 7 to 11%. In the composite code 21, the inflection point V
Is a tangent line S1 tangent to the curve in the state of zero elongation,
It is defined as an intersection with a vertical line passing through an intersection X where the tangent line S2 drawn on the curve c intersects at the break point.

The composite cord 21 has a high elasticity region from the inflection point V to the breaking point and an inflection point V from the origin at which the elongation is zero.
And a ratio EH / EL between the elastic modulus EH in the high elasticity region and the elastic modulus EL in the low elasticity region is set to 8 to 2.
The range is 0. In such a composite cord 21, 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, the composite cord 21 shown in FIG. As shown in, the composite cord 21 that can satisfy the above range can be formed. It can also be adjusted by selecting the stretching process applied to the composite cord 21, the high elastic filament 30, and the low elastic filament 31.

Since the inflection point V exists in the range of elongation of 7 to 11%, when a green tire is mounted on a vulcanization mold and an internal pressure is filled in the green tire during tire production, Due to the internal pressure, the band layer 9 becomes the composite cord 2
The groove shape formed in the mold can be engraved in the tread portion 2 by bulging by the extension of 1 and pressing the outer peripheral surface against the inner surface of the mold.

The swelling caused by filling the green tire with internal pressure is
The expansion is performed in the low elasticity region of the composite cord 21.
Therefore, the inflection point V is set in the range of elongation 7 to 11%. In addition, the required composite cord 2 in the mold by filling with internal pressure
The elongation of 1 is preferably located near the inflection point V.
As a result, it is 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, as shown in FIG. For this reason,
The ratio of the elastic modulus EH in the high elastic region to the elastic modulus EL in the low elastic region,
EH / EL is set to 8-20. When it is 8 or less, the suppressing effect is poor, and when it exceeds 20, it is unnecessary from the viewpoint of tire balance. By setting the ratio EH / EL to 8 to 20, swelling of the tire due to centrifugal force can be suppressed. As a result, vibration during high speed running is effectively reduced, peeling of the belt layer is prevented, and high speed durability is achieved. Further improve.

[0032]

Concrete Example Regarding a tire (Example) having a tire size of 170 / 60R17 and having the configuration shown in FIG.
A prototype was made according to the specifications shown in Table 1, and its performance was tested. For comparison, the belt layer and the band layer are shown in FIG.
The conventional structure shown in FIG. 0 was also tested to compare the performance of both. The test was conducted under the following conditions.

[0033]

[Table 1]

1) Grip characteristics A test tire was mounted on a motorcycle, and the motorcycle was tested on a test road at a speed of 260 km / H on a straight road and at a speed of 220 km / H on a curved road having a radius of curvature of 400 m. The vehicle was run and evaluated by the feeling of a test driver. The comparative example is shown by an index with 100, and the larger the value, the better.

2) High-speed stability during turning The stability during passing through the curved road in the test of the item 1) was evaluated by the driver's feeling. Comparative example 1
It is shown by an index of 00, and the larger the value, the better.

3) Peeling resistance of belt ply An internal pressure specified by JIS is applied to a test tire, and an internal durability test is used to apply an internal pressure specified by JIS and 1.5 times the maximum load to the sample tire. Moreover, the vehicle was run at a speed of 65 km / H, and the judgment was made based on the total running distance until peeling of the belt layer occurred.

4) High speed durability Using a drum tester, a JIS tire internal pressure and maximum load are applied to a sample tire, and high speed durability is achieved by increasing the initial speed from 200 km / H by 10 km / H every 20 minutes. A test was conducted, and the speed at which a crack was generated in the tread portion was judged. The speed is shown in Table 1, and the higher the speed value, the better.

As a result of the above test, 750 of the present invention was obtained.
It has been found that it is most suitable as a tire for large motorcycles of cc or more, and can withstand a speed of 280 km / H to 300 km / H.

(Straight stability at high speed) On a test course, an experienced test rider evaluated the feeling.

(Camber thrust) A camber angle was given to the tire and the camber thrust at that time was measured. The larger the value, the better.

[0041]

As described above, in the radial tire for a motorcycle of the present invention, the belt ply of the belt layer is the fold ply, and the band layer extending from the tire equator beyond the inner end of the folded portion is provided. In the belt layer structure, the number of the tread shoulder portions stacked is larger than that in the central portion of the tread portion, and therefore the central portion has a smaller cornering force than the tread shoulder portion. As a result, even when traveling at high speed, traveling stability is improved when traveling straight ahead,
Moreover, the turning performance is improved, and the high-speed traveling area can be increased. Moreover, since the belt layer having the above structure is provided, peeling of the belt layer is prevented and durability is improved.

[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 the configuration of each fold ply.

FIG. 3 is a perspective view illustrating a narrow ply.

FIG. 4 is a sectional view showing the winding.

FIG. 5 is a front view illustrating a composite cord.

FIG. 6 is a front view illustrating a composite cord.

FIG. 7 is a front view illustrating the elongation of the high-elasticity cord.

FIG. 8 is a front view illustrating the elongation of the high elasticity cord.

FIG. 9 is a diagram illustrating the elongation characteristics of a composite cord.

FIG. 10 is a diagram showing a conventional belt structure.

[Explanation of symbols]

 2 tread portion 3 sidewall portion 4 bead portion 5 bead core 6 carcass 7 belt layer 9 band layer 11 first belt ply 11A base portion 11B folded back portion 12 second belt ply 14 and 15 band ply 21 composite cord C tire equator G inside end

Continuation of the front page (56) Reference JP-A-2-106409 (JP, A) JP-A-61-166706 (JP, A) JP-A-3-16809 (JP, A) JP-A-2-106409 (JP , A) JP 53-136206 (JP, A) JP 64-52505 (JP, A) JP 1-190502 (JP, A) JP 2-6202 (JP, A) JP 1-247204 (JP, A) JP-A-63-287604 (JP, A) Actually opened 62-178201 (JP, U) Actually opened 61-147280 (JP, U) JP-B-3-76243 (JP, B2) JP-B 57-9965 (JP, B2) JP-B 3-76242 (JP, B2) JP-B 1-222721 (JP, Y2)

Claims (5)

(57) [Claims] 1. A bead core of a bead portion that extends from a tire equatorial plane to both sides in a meridian direction in an arc shape and has a cross-sectional shape in which a linear width between both ends is the maximum width of the tire and a sidewall portion through a tread portion. A carcass consisting of one or more carcass plies having carcass cords made of organic fibers which are folded around and inclined at an angle of 70 ° to 90 ° with respect to the tire equator, and inside the tread portion and radially outside the carcass. A belt layer disposed on the outer side in the radial direction of the belt layer, and the belt layer includes a first belt ply disposed adjacent to the carcass and the first belt ply. A second belt ply disposed outside the belt ply, wherein the first belt ply wraps both ends of the second belt ply on both sides of the base adjacent to the carcass. While using a fold ply having an inwardly folded back portion, the band layer extends from the tire equator beyond the inner end of the folded portion and is arranged substantially parallel to the tire equator, and the belt layer. The band layer is a radial tire for a motorcycle using a belt ply or a band ply made of 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. 2. The high elasticity filament is aromatic polyamide fiber, wholly aromatic polyester fiber or strength 15 g /
The radial tire for a motorcycle according to claim 1, wherein the radial tire is an organic fiber made of a polyvinyl alcohol fiber having a length of d or more. 3. The radial tire for a motorcycle according to claim 1, wherein the low-elasticity filament is nylon fiber, polyester fiber or vinylon fiber. 4. The composite cord is formed by twisting one or more under-twisted high-elasticity filaments and one or more under-twisted low-elasticity filaments in the same direction in opposite directions. The radial tire for motorcycles according to claim 1. 5. The composite cord has a low elasticity region whose stress-elongation curve extends from an origin to an inflection point, and a high elasticity region exceeding the inflection point, and the inflection point extends from 7 to 11 The radial tire for a motorcycle according to claim 1, wherein the ratio EH / EL of the elastic modulus EH in the high elastic region and the elastic modulus EL in the low elastic region is 8 to 20 in the range of%.