JPH04254205A - Pneumatic radial tire for two-wheeler - Google Patents

Abstract

PURPOSE:To improve wet performance without losing maneuvering stability on the dry road by forming two kind oblique grooves on a tread so as to make a pair respectively of the right and the left grooves, and forming a trifurcate and a hooked branches respectively in the oblique grooves. CONSTITUTION:Plural number of two kind oblique grooves 24 are formed on a tread 14 of a radial tire so as to separate mutually at the equator S of the tire, to cross respectively the equator of the tire, to extend alternately from the central area of the tread to the right and left tread side edges, and to make a pair of the right and left grooves. Meanwhile, the second oblique grooves 26 are formed between mutually adjacent first oblique grooves 24 so as to extend respectively and alternately from the central area of the tread to the right and left tread side edges, and to make a pair of the right and left grooves in the central area of the tread by sandwiching the first oblique grooves 24. Furthermore, a trifurcate branch 28 is formed in the first oblique groove 24 so as to extend from the tread side edges to the central area side of the tread while facing the second oblique grooves 26. Further, a hooked branch 30 is formed in the second oblique groove 26 between the first oblique grooves 24 so as to extend from the central area side of the tread to the tread side edges.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a pneumatic radial tire for two-wheeled vehicles having a belt consisting of a belt layer of organic fiber cords wound spirally substantially parallel to the tire equator over almost the tread width of the tire, particularly relates to a tire that has improved wet performance without impairing steering stability on dry roads.

0002

[Background Art] With the development of expressway networks and improvements in vehicle performance in recent years, similar to four-wheel vehicle tires, organic A so-called belt comprising a carcass consisting of carcass plies of fiber cords, and between the carcass and the tread rubber a belt consisting of belt layers of cords uniformly arranged at a small angle to the tire equator. Various pneumatic radial tires for motorcycles having a radial structure have been proposed.

[0003] In this radial tire,
It is known that the belt tightens the carcass from the circumferential direction and suppresses the movement of the tread, so it generates little heat and exhibits good wear resistance, grip performance, and high-speed performance.

Furthermore, recently, unlike the conventional belt structure, a belt consisting of a belt layer in which organic fiber cords are spirally wound substantially parallel to the tire equator between the carcass and tread rubber has been disposed. Pneumatic radial tires for motorcycles are being proposed that further suppress the radial outward extrusion of the tire tread during driving, have excellent high-speed performance, and have reduced tire weight.

[0005] Note that spirally winding the cord of the belt layer over a range of approximately 70% to 110% of the tread width not only sufficiently suppresses the protrusion of the tread, but also improves the rigidity of the tire casing. This is to maintain a constant increase rate of camber thrust with respect to the camber angle as a nearly uniform tread. As with radial tires, it is customary to provide grooves that extend parallel to the tire equator.

[0006]

[Problems to be Solved by the Invention] However, in a radial tire for two-wheeled vehicles in which the cords of the belt layer are spirally wound substantially parallel to the tire equator, it is difficult to arrange the cords in the extending direction of the cords and on the tread surface. Since the grooves almost coincide with those of the grooves, during tire molding, the protrusions on the inner surface of the mold that correspond to the grooves push the cords that make up the belt, which are located radially inside the tire with respect to the groove bottom, in the width direction of the tire. There are problems such as a decrease in the steering stability of the tire due to the fact that the belt layer cannot be arranged uniformly in the width direction and radial direction of the tire, such as so-called "cord opening".

Furthermore, when a camber angle is applied to turn the vehicle, the contact area between the tread and the road surface shifts from the center area of the tread toward its side edges. There was a problem in that wet performance deteriorated due to impaired drainage performance.

[0008] The present invention was made in view of these problems, and an object of the present invention is to provide a pneumatic radial tire for two-wheeled vehicles that has improved wet performance without impairing steering stability on dry roads. do.

[0009]

[Means for Solving the Problem] In order to achieve this object, in the present invention, a pair of sidewalls and a tread are connected in a toroidal manner, and each of these parts is arranged at an angle of 75° to 90° with respect to the tire equatorial plane. The tire is reinforced with a carcass consisting of at least one carcass ply of organic fiber cords arranged at a certain angle within a range, and both ends of the carcass ply are embedded around a bead core embedded in the radially inner ends of both sidewalls. Wind it up toward the outside in the direction of the rotational axis,
Between the tread rubber and the carcass, there is approximately 7 of the tread width.
A pneumatic radial tire for two-wheeled vehicles equipped with a belt having at least one belt layer made of an organic fiber cord wound spirally substantially parallel to the tire equator over a range of 0% to 110%, the tread of which is A plurality of first diagonal grooves are spaced apart from each other on the tire equator and extend alternately from the center region of the tread to the left and right side edges of the tread across the tire equator, forming pairs on the left and right; The second diagonal grooves each extend from the tread center region to the tread side edge between the first diagonal grooves and form a pair on the left and right through the first diagonal groove in the tread center region, and the first diagonal groove is It has a three-pronged branch extending from the tread side edge side to the tread center area side facing the second diagonal groove, and the second diagonal groove has a branch diagonal groove of one of the paired first diagonal grooves and the other first diagonal groove. It has a hook-shaped branch extending from the tread center region side to the tread side edge side between the diagonal groove and the tread groove.

0010

[Operation] While the extending direction of the first and second diagonal grooves, as well as the three-pronged branch and the hook-shaped branch related to the diagonal grooves, intersects the cord wound spirally substantially parallel to the tire equator. The herringbone-shaped land section divided by these diagonal grooves and branches maintains the spirally wound cords arranged uniformly in the width direction and radial direction of the tire, thereby reliably preventing problems caused by the cords opening. This ensures good handling stability.

In addition, the first and second diagonal grooves, as well as the three-pronged branch and the hook-shaped branch related to these diagonal grooves, extend alternately from the tread center region to the left and right tread side edges, respectively, straddling the tire equator. Therefore, even if the tread contact area shifts from the center area to either the left or right tread side edge as the vehicle turns, the ratio of the groove to the contact area can be maintained almost constant, regardless of changes in the camber angle. Demonstrates the specified drainage performance.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1(a) is a cross-sectional view showing a half of the pneumatic radial tire for two-wheeled vehicles according to the present invention with respect to the equator S. Arranged by angle, e.g.
The carcass 12 is comprised of at least one carcass ply of organic fiber cord such as nylon or polyester. The carcass 12 reinforces the toroidally connected Toledo 14 and the sidewalls 16, and its both ends are rolled up toward the outside in the tire rotational axis direction around a bead core 18 buried near the radially inner ends of both sidewalls 16. It is being

Between the tread rubber forming the tread 14 and the carcass 12, a suitable organic fiber cord is inserted substantially parallel to the tire equator S from 70% to 110% of the tread width w.
A belt 20 is provided having at least one belt layer spirally wound over a range of . Note that the reference numeral 22 is a rubber filler, and its function is similar to that of known tires.

The treads 14, shown partially enlarged in FIG. 1(b), extend alternately across the tire equator S from the tread center region to the left and right tread side edges, and are spaced apart from each other on the tire equator. A large number of first diagonal grooves 24 are formed in pairs on the left and right.
Equipped with. The first diagonal grooves 24 that form a pair on the left and right form an "inverted V" shape that is shifted by half a pitch on the tire equator S when viewed from the front in the direction of rotation when mounted on a vehicle, and are each 30 mm apart from the tire equator S. Constant angle θ1 within the range of ° ~ 50 °
Alternately cross each other.

This means that if the intersection angle θ1 of the first diagonal groove 24 with respect to the tire equator S, that is, the angle between the diagonal groove 24 and the tire equator S, is made smaller than 30°, the groove formed on the inner surface of the mold during tire molding will be These protrusions tend to cause problems such as cord opening in the spirally wound cord that is located inside the tire radial direction with respect to the groove bottom of the diagonal grooves 24 and constitutes the belt 20. If the intersection angle θ2 with the tire equator S is larger than 50°, the tire width direction component of the diagonal grooves 24 increases, so that the first diagonal grooves 24
This is because the drainage performance deteriorates rapidly.

Furthermore, the reason why the first diagonal grooves 24 extend alternately from the center region of the tread to the left and right tread side edges across the tire equator is that even when the center region of the tread makes contact with the ground, the first diagonal grooves 24 extend across the tire equator. This is to ensure sufficient drainage performance by maintaining the ratio of the diagonal groove portion to the ground contact area including the groove portion to a certain value or more. Therefore, the length K of the overlapping portion in the tire width direction in the tread center region of the first diagonal grooves 24 extending to the left and right tread side edges is set to 10% to 30% of the tread width W of the tire 10,
In addition, the distance L between the left and right first diagonal grooves 24 on the tire equator is set to 2% to 3% of the tire circumference or 30% of the tread width W.
% to 40%.

The reason why the length K in the tire width direction of the overlapping portion of the first diagonal grooves 24 is set to 10% to 30% of the tread width W of the tire 10 is because if the length K is less than 10%, the first diagonal grooves As a result, the ratio of the diagonal groove portion to the ground contact area including the groove portion becomes too small, making it difficult to expect desired drainage performance.If the length K is made larger than 30%, the drainage performance of the tire becomes advantageous, This is because the rigidity of the land portion defined by the oblique grooves 24 is locally reduced, and the durability performance of the tire is reduced.

Similarly, the left and right first
If the distance L between the diagonal grooves 24 is made smaller than 20% of the circumference or 30% of the tread width W, the ratio of the groove to the ground contact area can be increased, but as a result, the rigidity of the land part near the tire equator becomes too small. A decrease in tire durability performance is unavoidable, and the gap L should be reduced to 3% of the circumference or the tread width W.
If it is larger than 40%, although the rigidity of the land portion near the tire equator can be increased, the ratio of the groove portion to the ground contact area becomes small, and the drainage performance deteriorates.

[0019] The tire of the present invention also has features to ensure sufficient water drainage performance even when the contact area of the tread deviates from the center area toward the side edges due to changes in the camber angle caused by the turning motion of the two-wheeled vehicle. In the tread portion defined by the first diagonal grooves 24 adjacent to each other in the tire circumferential direction,
A plurality of second diagonal grooves 26 are formed in pairs on the left and right through the first diagonal grooves 24 in the tread central region, and extend substantially along the first diagonal grooves 26. make it exist

[0020] In a tire in which the second diagonal grooves 26 are disposed between the first diagonal grooves adjacent to each other in the circumferential direction of the tire,
As the tread contact area shifts outward from the central area in the tire width direction, the overlapping portion of the first diagonal groove 24 in the tread central area decreases, while the land area defined by the first and second diagonal grooves decreases. As the area increases, wet performance deteriorates.

Accordingly, in the present invention, each of the first diagonal grooves 24 is provided with a three-pronged branch 28 that faces the second diagonal groove 26 and extends from the tread side edge side to the central region side thereof. Each of the second diagonal grooves 26 also has a hook shape extending from the tread center region side to the tread side edge side between the three-pronged branch 28 of one of the pair of first diagonal grooves and the other first diagonal groove. A branch 30 is provided. The angle θ2 formed by the respective extending directions of the three-pronged branch 28 and the hook-shaped branch 30 with respect to the tire equator S
and θ3 are approximately equal to the angle θ1 that the first oblique groove 24 makes with the tire equator S.

In this way, the first diagonal groove 24 forms a three-pronged branch 28.
In addition, since the second diagonal grooves 26 each include the hook-shaped branches 30, even if the tread contact area shifts outward in the tire width direction as the vehicle turns, these three-pronged branches and hook-shaped branches can be removed. Since the branch maintains the ratio of the groove to the contact area above a certain value, wet performance does not deteriorate. Moreover, by providing these branches, the rigidity of the land section divided by the first and second diagonal grooves, three-pronged branch, and hook-shaped branch can be made almost uniform, resulting in stable steering on dry roads. Sexuality will also improve.

It is also conceivable that the hook-shaped branch of the second diagonal groove 26 is arranged on the side edge of the tread, and the three-pronged branch of the first diagonal groove 24 is arranged on the side of the central region of the tread. However, in that case, the rigidity of the land section defined by the first diagonal groove section that straddles the tire equator S and the three-pronged branch located in the center area of the tread decreases, and the steering stability and durability performance of the tire decreases. Therefore, it is preferable to provide a three-pronged branch and a hook-shaped branch as in the embodiments described above.

◎Comparative Example In order to investigate the handling stability of the tire according to the present invention on wet and dry roads, the tire according to the present invention and the tire shown in FIG. 2(a) were tested.
A comparative test was conducted using the sample tires having the tread patterns shown in FIGS. 3(a) and 3(b), and the results shown below were obtained. The tires used in the comparison test were all MCR 160/60 R1 in size.
7, and the carcass consists of a cord made of 66 nylon with a thickness of 1260 d/2, which is arranged substantially at 9
A belt consisting of a single layer of carcass plies arranged at an angle of 0°, and a belt consisting of a single layer of a cord made of aromatic polyamide fiber with a thickness of 1500 d/2 spirally wound approximately parallel to the tire equator. It is.

Furthermore, the groove width of the first diagonal groove is 6 mm at the center of the tread crown, the groove depth is 6 mm, the length K of the overlapping part is 19% of the tread width W, and the angle θ1 with the tire equator is 38°. , the gap L on the tire equator is 2.7% of the tire circumference or 34% of the tread width, the three-pronged groove width is 7mm, the groove depth is 3mm, and the angle θ with the tire equator.
2 is 38 degrees, the groove width of the second oblique groove is 6 mm, and the groove depth is 5.
5mm, hook-shaped branch groove width 6mm, groove depth 5.5m
m, and the angle θ3 formed with the tire equator is 38°.

◎Test Tire: Invention Tire A tire having a tread pattern shown in FIG. 1(b). - Comparative Tire 1 A tire with a tread pattern shown in Figure 2. - Comparison Tire 2 A tire with a tread pattern shown in Figure 3. - Comparative Tire 3 A tire with a tread pattern shown in Figure 4. - Comparative Tire 4 A tire with a tread pattern shown in Figure 5.

◎Test method - Wet road surface: Tires were mounted on an actual vehicle, and a straight slalom test was conducted on a test road with a water depth of 3 mm, and an index evaluation was performed by a feeling test.・Dry road surface: Tires were mounted on an actual vehicle, a straight slalom test was conducted on a dry test road, and the index was evaluated using a feeling test.

◎Test results Here, CA indicates the camber angle, for example, CA
=40° or more means that the camber angle is inclined from 40° to the maximum angle. In addition, CA = 0° to 40° for dry road handling stability and index 100 for wet road handling stability mean a substantially straight line with a width of 6 mm and a groove depth of 6 mm extending parallel to the tire equator in the center area of the tread. This is based on a feeling test of tires with grooves of
This is based on a feeling test of a tire having the tread pattern shown in .

As is clear from this table, it can be seen that according to the tire of the present invention, it is possible to improve the steering stability performance on a wet road surface while improving the steering stability performance on a dry road surface.

Thus, according to the present invention, it is possible to provide a pneumatic radial tire for two-wheeled vehicles that has improved steering stability on both dry and wet road surfaces.

[Brief explanation of the drawing]

FIG. 1 (a) is a cross-sectional view showing half of a pneumatic radial tire for two-wheeled vehicles according to the present invention, and (b) is an enlarged view of a part of the tread of the tire shown in (a). FIG.

FIG. 2 is an enlarged view of a part of the tread of comparative tire 1. FIG.

FIG. 3 is an enlarged view of a part of the tread of comparative tire 2. FIG.

FIG. 4 is an enlarged view of a part of the tread of comparative tire 3. FIG.

FIG. 5 is an enlarged view showing a part of the tread of the comparative tire 4. FIG.

[Explanation of symbols]

10 Tires 12 Carcass 14 Tread 16 Sidewall 18 Bead core 20 Belt 22 Comb filler 24 First diagonal groove 26 Second diagonal groove 28 Three-pronged branch 30 Hook-shaped branch

Claims (1)

[Claims] Claim 1: At least one carcass of organic fiber cords, in which a pair of sidewalls and a tread are connected in a toroidal manner, and each of these parts is arranged at a constant angle within a range of 75° to 90° with respect to the tire equatorial plane. The carcass is reinforced with a carcass made of ply, and both ends of the carcass ply are wound outward in the tire rotational axis direction around a bead core embedded in the radially inner ends of both sidewalls, and between the tread rubber and the carcass, Approximately 70% of tread width
A pneumatic radial tire for two-wheeled vehicles equipped with a belt comprising at least one belt layer made of an organic fiber cord wound spirally substantially parallel to the tire equator over a range of 110%, the tread of which is , a plurality of first diagonal grooves that are spaced apart from each other on the tire equator and extend alternately from the center region of the tread to the left and right side edges of the tread across the tire equator, forming pairs on the left and right; and first diagonal grooves that are adjacent to each other; A second diagonal groove is provided between the diagonal grooves, each extending from the tread center region to the tread side edge, and forming a pair on the left and right with the first diagonal groove in between in the tread center region, and the first diagonal groove has a first diagonal groove. The second diagonal groove has a three-pronged branch extending from the tread side edge side to the tread center area side facing the two diagonal grooves, and the second diagonal groove has a trifurcated branch of one of the paired first diagonal grooves and the other first diagonal groove. A pneumatic radial tire for a two-wheeled vehicle, comprising a hook-shaped branch extending from the tread center region side to the tread side edge side between the tread center area and the tread side edge.