JPH1053007A - Radial tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a cornering force effectively and enhance the revolving performance while the comfortableness during straight running is well maintained by heightening the rigidity of a radial tire to an appropriate degree while the grounding area of the shoulder part is secured satisfactorily. SOLUTION: A radial tire concerned is composed of a carcass having a cord angle of 70-90deg., a band layer 7 formed by winding cords spirally in the tire circumferential direction, and a reinforcement layer consisting of a pair of reinforcing pieces 9A having a cord angle of 10-35deg. furnished between the layer 7 and carcass or on the onside of the layer 7 and only in the shoulder part. A central region YP is set between inner points P and P where the perpendicular line passing the inner ends J2 of the reinforcing pieces 9A and perpendicular thereto intersects the tread part 2S, while an outer region YQ is set between an outer point Q, where the perpendicular line passing the outer ends J1 of the reinforcing pieces 9A intersects the tread part 2S, and the inner point P adjoining thereto, and therein the ratio Sr/Cr is made ranging 1.10 to 1.30, where Cr is the radius of curvature of the central region YP and Sr is the radius of curvature of the outer region YQ, wherein the width of each reinforcing piece 9A is made 0.15-0.35 times as large as the tread width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention increases the rigidity and the ground contact area of a shoulder portion, and effectively exerts a high cornering force and the like, thereby improving the turning performance while maintaining the riding comfort when traveling straight. The present invention relates to a motorcycle radial tire that can be improved in width.

[0002]

2. Description of the Related Art With the improvement of the expressway network and the performance of vehicles in recent years, a shift to a radial structure which is excellent in high-speed running performance is being attempted even for motorcycle tires.

[0003] Such a tire having a radial structure has a strong belt layer on the outside of a radially arranged carcass. In recent years, in order to improve riding comfort in a radial tire, a cord is formed between plies as a belt layer. Japanese Patent Publication No. 3-8961 and the like have proposed a parallel cord ply in which a cord is spirally wound substantially parallel to the tire equator, instead of the conventional cross cord ply cross-arranged as described above.

[0004] The parallel cord ply is provided with flexibility such as a reduced bending rigidity of the tread portion inward in the radial direction as compared with the cross cord ply, so that the contact property can be improved and the riding comfort can be improved. It is said that. However, because of the flexibility, the camber thrust and the cornering force generated at the time of turning are both too small, and a so-called stiffness phenomenon occurs particularly at the time of turning in a large vehicle, which tends to impair steering stability.

[0005]

SUMMARY OF THE INVENTION Accordingly, Japanese Patent Application Laid-Open No. Hei.
Japanese Patent Application Publication No. 1003 discloses that, with the aim of improving the steering stability at the time of turning while maintaining the riding comfort when traveling straight, the outer side of the belt layer made of the parallel cord ply and the shoulder portion are provided at 20 to 45 degrees. It is disclosed that a reinforcing layer in which organic fiber cords are arranged at an angle is provided to appropriately increase the rigidity of a shoulder portion.

However, in the case where the reinforcing layer is provided on a tire having a generally single-arc-shaped tread profile which has been conventionally used, a contact area at a shoulder portion which contacts the ground at the time of turning is small, and the shoulder portion has a small contact area. Due to the high rigidity, the road following ability is impaired, so that a cornering force or the like is not effectively exerted and the gripping force is insufficient, and there is a problem that a satisfactory effect of improving turning performance cannot be obtained.

Therefore, the invention according to claim 1 of the present invention is to provide, in addition to providing a reinforcing layer on each shoulder portion, making the radius of curvature of the outer region of the tread surface larger by a predetermined ratio than the radius of curvature of the central region. Basically, a radial tire for motorcycles that can sufficiently improve the turning performance while maintaining the riding comfort when traveling straight by ensuring a sufficient ground contact area at the shoulder part and effectively exhibiting a high cornering force The purpose is to provide.

Another object of the present invention is to provide a radial tire for a motorcycle capable of suppressing damage such as cord loose from an outer end of a reinforcing layer and improving durability.

According to a third aspect of the present invention, there is provided a radial tire for a motorcycle capable of exhibiting a rigidity improving effect by a reinforcing layer almost to the limit of a turning limit, and performing stable and safe turning without causing a feeling of being stiff. It is an object.

[0010]

In order to achieve the above-mentioned object, according to the present invention, the invention according to the first aspect of the present invention is directed to a method in which a bead portion is turned around a bead core of a bead portion from a tread portion to a side wall portion and a carcass. A carcass in which cords are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction, and a band layer arranged radially outside the carcass and inside the tread portion and spirally winding the band cord in the tire circumferential direction. A radial tire for a motorcycle having a tread surface in an arc shape, wherein a reinforcing cord is provided between the band layer and the carcass or radially outside of the band layer and only at the shoulder portion, with respect to the tire circumferential direction. ~ 35
While providing a reinforcing layer consisting of a pair of reinforcing pieces arranged at an angle of degree, the inner point P where a perpendicular perpendicular to the reinforcing piece passes through the inner end point of the reinforcing piece in the tire axial direction and intersects the tread surface, In a central region between P and an outer region between an outer point Q where a perpendicular passing through the outer end point of each of the reinforcing pieces intersects the tread surface and the inner point P adjacent thereto, the center is located at the tire equatorial plane. The ratio Sr / Cr of the radius of curvature Cr forming the central region to the radius of curvature Sr forming the outer region is 1.10 to 10.
1.30, and the center region and the outer region are smoothly connected, and the reinforcing piece width HW of the reinforcing piece in the tire axial direction is 0.15 to 0.35 times the tread width TW. It was a thing.

According to a second aspect of the present invention, each reinforcing piece is formed from a single layer of reinforcing ply, and the outer end point of the reinforcing piece is located inward of the outer end point of the band layer in the tire axial direction. It is a characteristic.

Further, according to a third aspect of the present invention, the width B of the band layer
W is 0.7 to 1.0 times the tread width TW, and the distance ZW along the band layer between the outer end point of the reinforcing piece and the outer end point of the band layer is 0.06 times or less of the tread width TW. It is characterized by that.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a radial tire 1 for a motorcycle (hereinafter referred to as a tire 1) has a tread surface 2.
A tread portion 2 in which S smoothly curves in an arc shape, sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and bead portions 4 located at radially inner ends of the respective sidewall portions 3 in the tire radial direction. With tread ends E1, E
The tread width TW, which is the distance between the tires 1 in the axial direction of the tire, is formed to be the maximum width of the tire.

The tire 1 also includes a carcass 6 bridged between the bead portions 4, a band layer 7 disposed radially outside the carcass 6 and inside the tread portion 2, and a band layer 7. A reinforcing layer 9 is provided between the carcass 6 and the outer side of the band layer 7 in the radial direction.

The carcass 6 has, at a main body portion extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3, a folded portion for turning around the bead core 5 from the inside in the tire axial direction to the outside. A space between the main body portion and the folded portion is filled with a bead apex rubber 8 having a triangular cross section and extending outward from the bead core 5 in the tire radial direction.

The carcass 6 has one or more carcass cords 10 in which carcass cords 10 are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction.
6B, the height H1 of the folded portion of one carcass ply from the bead base line L is set to the tread end E
By adopting a high turn-up configuration in which the height H2 is up to about 0.6 to 0.9 times the height H2, the tire lateral rigidity is increased together with the bead apex rubber 8.

The band layer 7 comprises at least one band ply 7A spirally wound at an angle of 5 degrees or less with respect to the circumferential direction of the tire, in this example, one band ply 7A. In the present example, is formed into a strip-shaped and long narrow ply 12 in which one or a plurality thereof are aligned and spirally wound. The narrow ply 12 is
As shown in FIG. 2, for example, the band cord 11 has a flat rectangular cross-sectional shape in which two band cords 11 are embedded in topping rubber, and the distance N from the side surface 12S to the center of the outermost band cord 11 is represented by a pitch between cords Pi. Is set to approximately 1/2.

The band ply 7A of this embodiment is formed by continuously winding the narrow ply 12 from one tread end E1 to the other tread end E1 while the side surfaces 12S are in contact with each other. For example, two small width plies 12 are used, and each small width ply 12 is
It can also be wound from the vicinity to the tread ends E1 on both sides, or from the tread ends E1 on both sides to the tire equator C. When winding the small width ply 12, the vicinity of the side surface 12S may be overlapped and wound to prevent the cord from loosening.

The band layer 7 preferably has a band width BW in the tire axial direction of 0.7 to 1.0 times the tread width TW, whereby the tag effect can be obtained over substantially the entire width of the tread. To enhance the shape retention of a tread profile, which will be described later, and increase the contact area at the shoulder portion during turning.

The reinforcing layer 9 has a shoulder portion S of the tread.
H comprises only a pair of left and right reinforcing pieces 9A, which are provided only at H, and are provided at symmetrical positions about the tire equator C, respectively.
Each reinforcing piece 9A is formed of one or more (one layer) reinforcing plies in which the reinforcing cords 13 are arranged at an angle of 10 to 35 degrees with respect to the tire circumferential direction. In this example, the reinforcing layer 9 is formed radially outside the band layer 7, but may be arranged between the band layer 7 and the carcass 6.

Accordingly, in the shoulder portion SH where the reinforcing pieces 9A are arranged, the reinforcing cords 13 form a truss structure in cooperation with the radially arranged carcass cords 10 and the band cords 11 extending in the tire circumferential direction. Moderately improve rigidity. On the other hand, the reinforcing piece 9 that contacts the ground when traveling straight ahead
A portion between A and 9A is provided with flexibility such as a reduction in bending rigidity inward in the radial direction by the band cord 11, so that riding comfort is enhanced and straight running performance can be improved.

When the cord angle of the reinforcing cord 13 is about 25 degrees, the cornering force based on the truss structure becomes maximum. Therefore, when the cord angle of the reinforcing cord 13 is less than 10 degrees and greater than 35 degrees, any However, the effect of increasing the cornering force is not sufficiently achieved.
In addition, when the cord angle is less than 10 degrees, the length of the ply material for the reinforcing piece 9A used in forming a green tire becomes excessively long, resulting in inferior handleability, and the joining between the winding start end and the winding end end of this ply material. The part becomes long and the moldability deteriorates. Therefore, the upper limit of the cord angle is preferably set to 30 degrees or less, and the lower limit is preferably set to 20 degrees or more.

Each of the reinforcing pieces 9A has a reinforcing piece width HW in the tire axial direction of 0.15 to 0.3 of the tread width TW.
When the width is smaller than 0.15 TW, the width of the region where the rigidity is increased in the shoulder portion SH becomes too small, and the cornering force becomes insufficient, so that the turning performance cannot be improved. In addition, when it is larger than 0.35 TW, the reinforcing piece 9A also affects the rigidity of the vehicle while traveling straight, and the riding comfort is impaired. Therefore, the upper limit of the reinforcing piece width HW is
Preferably, it is 0.25 TW.

The reinforcing layer 9 is preferably formed of one (one layer) reinforcing ply. This is because, even when two or more reinforcing plies are formed, the effect of improving the turning performance hardly increases, and adverse effects such as an increase in weight and an increase in cost are caused.

The outer end point J1 of the reinforcing piece 9A in the tire axial direction.
Is preferably located inward in the tire axial direction from the outer end point K1 of the band layer 7 in the tire axial direction. This is because the cut surface of each reinforcing cord 13 is located at the outer end point J1 of the reinforcing piece 9A. If the outer end point J1 protrudes outward from the outer end point K1 of the band layer 7, the reinforcing cord A large load is applied to the cut surface of No. 13, and damage such as cord loose occurs early from the cut surface, which is inferior in adhesiveness to rubber, and the durability is impaired. Since the band layer 7 is spirally wound, the cut surface of the cord is hardly formed at the outer end point K1 and hardly damaged. However, if the outer end points J1 and K1 are too close, stress concentrates. The durability tends to decrease. Therefore, in order to surely prevent this, it is preferable that the distance ZW between the outer end points J1 and K1 along the band layer 7 is 3 mm or more.

The reinforcing piece 9A preferably has the distance ZW of 0.06 times or less of the tread width TW and improves the rigidity together with the band layer 7 up to the limit of the tread end E1, which is a turning limit. In traveling at the turning limit, the driver can be stably and safely turned without incurring a feeling of being stiff.

In order to achieve both straight running performance and turning performance, the width WP in the tire axial direction between the inner end points J2 and J2 of the reinforcing piece 9A is set to be 0.30 to 0.60 of the tread width TW.
Preferably, the width WQ between the outer end points J1 and J1 of the reinforcing piece 9A is 0.70 to 1.0 times the tread width TW. When the width WP is larger than 0.6 TW and the width WQ
Is smaller than 0.7 TW, the cornering force generated in the shoulder portion SH is small, and the turning performance is reduced. When the width WP is smaller than 0.30 TW, the stiffness is increased due to the influence of the reinforcing piece 9A even when traveling straight, and the riding comfort is deteriorated. When the width WQ is larger than 1.0 TW, the outside of the reinforcing piece 9A The end point J1 is a side wall portion 3 with a large bend.
, The cord loose tends to occur at the outer end point J1. Therefore, the upper limit of the width WP is 0.50 TW,
The lower limit is preferably set to 0.35 TW.

In the tire 1, the profile of the tread surface 2S is specified in order to effectively generate a cornering force by the reinforcing layer 9 and to surely improve the turning performance.

That is, as shown in FIG. 4, the tread surface 2S extends between the inner points P, P passing through the inner end point J2 of the reinforcing piece 9A and a perpendicular line perpendicular to the reinforcing piece 9A intersects the tread surface 2S. A central area YP and an outer end point J of the reinforcing piece 9A
1 is divided into an outer region YQ between the outer point Q intersecting the tread surface 2S and the inner point P adjacent thereto, and a radius of curvature Cr forming the central region YP, and the outer region YQ And the ratio Sr / Cr to the radius of curvature Sr is 1.10.
It is regulated to 1.30.

Here, the radius of curvature Cr forming the central region YP is defined by the inner points P, P and a straight line PP between the inner points.
Is defined as the radius of curvature of a single arc 20 passing through three points with the midpoint Pn at which the perpendicular bisector of the line intersects the tread surface 2S.
Similarly, the radius of curvature Sr forming the outer region YQ is defined by the inner point P, the outer point Q, and the midpoint Qn at which the perpendicular bisector of the straight line PQ between the inner and outer points intersects the tread surface 2S. Is defined as the radius of curvature of the single arc 21 passing through the three points.

Therefore, according to the above definition, the central area YP itself and the outer area YQ itself are connected to the single arc 2.
It is not necessary to form them at 0 and 21, and they may be formed by a curve in which a plurality of circular arcs are smoothly connected, a curve in which the curvature is continuously changed, or the like. When such a curve is used, the curvature is set to gradually increase outward in the tire axial direction. However, preferably, the central area YP and the outer area YQ are in contact with each other in the single circular arc 20,
21 is preferable.

As described above, the curvature radius ratio Sr / Cr is set to 1.
Since the radius of curvature Sr of the outer region YQ is set to 10 to 1.30, the contact area in the outer region YQ where the effect of increasing the rigidity by the reinforcing layer 9 is large can be sufficiently secured, and a higher cornering force can be obtained. It is possible to generate it.

When the ratio Sr / Cr is less than 1.10, the contact area during turning is insufficient, and the turning performance is not improved. In the process of shifting to, handling characteristics such as the steering wheel become lighter in the middle, and the stability is impaired. On the other hand, when the ratio Sr / Cr exceeds 1.30, the steering wheel becomes heavier when shifting from straight running to turning running, and the stability is impaired. Therefore, it is preferable that the ratio Sr / Cr has a lower limit of 1.15 or more and an upper limit of 1.25 or less.

The carcass cord 10, band cord 11, and reinforcing cord 13 are organic fiber cords such as nylon, polyester, rayon, and aromatic polyamide.
Steel fiber cord, glass fiber cord and the like can be used. However, it is preferable to use an organic fiber cord for weight reduction and the like. In order to obtain higher cornering force and high-speed durability, the band cord 1
1. The reinforcing cord 13 is preferably an aromatic polyamide fiber cord.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire having the structure shown in FIG.
5R17 tires were prototyped based on the specifications in Table 1, and each trial tire was rim 17 × MT5.50, internal pressure 2.
Under the condition of 9 kgf / cm ^2, the motorcycle (750cc,
Four cycles), the vehicle was mounted on the rear wheel, the vehicle was driven on a dry pavement road, and straight-running stability, critical speed during turning, and transient characteristics during turning were compared by a sensory evaluation by a driver. As the tires mounted on the front wheels, conventional tires having the specifications shown in Table 2 were used. The evaluation was performed using a five-point method, and the larger the score, the better the performance.

FIGS. 5A to 5C show Comparative Example Product 2,
3 shows the arrangement positions of the band layer and the reinforcing layer used for the tires of Example 3 and Examples 5 and 6.

Each test tire was mounted on a rim 17 × MT5.5.
0, internal pressure 2.5 kgf / cm ² , load 335 kg, speed 6
An endurance test was performed by running on a drum under the condition of 0 km / h, and the tire after the completion of 13000 km was disassembled to check for tire damage. In the table, * 1 indicates "no damage" and * 2 indicates "cord loose occurs at the outer end point of the reinforcing piece."

[0038]

[Table 1]

[0039]

[Table 2]

As shown in Table 1, the radius of curvature ratio Sr / C
In the tire of the example product in which r was set to 1.10 to 1.30,
Since the ground contact area is sufficiently ensured, the effect of the reinforcing layer is effectively exhibited, and the cornering force can be greatly increased to improve the turning performance.

[0041]

As described above, in the tire of the present invention, in addition to providing the reinforcing layer on each shoulder portion, the radius of curvature of the outer region of the tread surface is made larger than the radius of curvature of the central region by a predetermined ratio. By ensuring a sufficient contact area at the section and generating a high cornering force, the turning performance can be greatly improved while maintaining the riding comfort when traveling straight.

[Brief description of the drawings]

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

FIG. 2 is a perspective view illustrating a narrow ply.

FIG. 3 is a schematic diagram showing a cord arrangement of a carcass, a band layer, and a reinforcing layer.

FIG. 4 is a diagram showing a profile of a tread surface.

5 (a) to 5 (c) are diagrams schematically illustrating arrangement positions of a band layer and a reinforcing layer of a tire used in the performance test of Table 1. FIG.

[Explanation of symbols]

 2 Tread portion 2S Tread surface 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 7 Band layer 9 Reinforcement layer 9A Reinforcement piece 10 Carcass cord 11 Band cord 13 Reinforcement cord J1 Outer end point of reinforcement piece J2 Inner end point of reinforcement piece K1 Band layer Outer end point of SH Shoulder part YP Central area YQ Outer area

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B60C 9/22 B60C 9/22 A

Claims (3)

[Claims] 1. A carcass which is folded around a bead core of a bead portion from a tread portion to a sidewall portion and has carcass cords arranged at an angle of 70 to 90 degrees with respect to a tire circumferential direction, and a radius of the carcass A radial tire for a motorcycle having a band layer spirally wound in the tire circumferential direction with a band cord disposed outside in the direction and inside the tread portion, and having a tread surface in an arc shape, wherein the band layer and the carcass And a reinforcing layer consisting of a pair of reinforcing pieces in which reinforcing cords are arranged at an angle of 10 to 35 degrees with respect to the tire circumferential direction, and only at the shoulder portion in the radial direction of the band layer and at the shoulder portion. A central region between the inner points P, P at which a perpendicular line perpendicular to the reinforcing piece passes through the inner end point in the tire axial direction and intersects the tread surface; At an outer region between an outer point Q at which a perpendicular passing through the end point intersects the tread surface and the inner point P adjacent thereto, a radius of curvature Cr having a center on the tire equatorial plane and forming the central region, The ratio Sr / Cr to the radius of curvature Sr forming the region is set to 1.10 to 1.30,
Moreover, the center region and the outer region are smoothly connected, and the width HW of the reinforcing pieces in the tire axial direction of the reinforcing pieces is 0.15 to 0.35 times the tread width TW. Radial tire. 2. The method according to claim 1, wherein each of the reinforcing pieces comprises a single layer of reinforcing ply, and the outer end point of the reinforcing piece is located inward in the tire axial direction from an outer end point of the band layer in the tire axial direction. The radial tire for a motorcycle according to claim 1. 3. The band width B of the band layer in the tire axial direction.
W is 0.7 to 1.0 times the tread width TW, and the distance ZW along the band layer between the outer end point of the reinforcing piece and the outer end point of the adjacent band layer is the tread width TW. 3. The method according to claim 2, wherein the value is 0.06 times or less.
The radial tire for a motorcycle according to the description.