JPH0234403A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To enhance the comfort of passenger, road grasping force, and revolving characteristic of a tire for motorcycle formed in spiral radial structure by furnishing a belt with cords extending in the circumferential direction, and setting the number of driven-in cords a certain number of times as large at the side end of belt as in the other parts. CONSTITUTION:A tire 11 includes a carcass 15 having radially oriented cords 13 in toroidal form between a pair of beads 12, a belt 16 extending in the circumferential direction outside the crown part 15a of the carcass 15, and tread 17 covering this belt 16. The belt 16 is equipped with a belt layer 16A having cord stretching circumferentially. This belt layer 16A is formed from the central part 16a with the equator E as center and a pair of side ends 16b continued from the sides of this central part. The number of driven-in cords for the belt layer 16A shall be 1.4-2.4 times as large at the side end part 16b as in the central part 16a.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pneumatic radial tire, and particularly to a pneumatic radial tire for a two-wheeled vehicle that is mounted on a two-wheeled vehicle and runs at high speed on a good road.

(Prior Art) Generally, in a two-wheeled vehicle, the running characteristics of the vehicle during running are largely influenced by the performance of the tires mounted on the vehicle.

Therefore, it is important to match the performance characteristics of the tire with the driving characteristics of the vehicle.

Conventional pneumatic radial tires for two-wheeled vehicles, for example, have a radial structure in which the cords of the carcass are arranged in the radial direction, and the cord 2 of the belt l is placed around the tire circumference on the outside of the carcass, as shown in Figure 4. There is a pneumatic radial tire with a so-called monospiral radial structure that is wound spirally in the direction of the tire. Due to the characteristics of the belt, such a pneumatic radial tire can maintain sufficient strength in the circumferential direction of the tire while reducing the cross-sectional bending rigidity of the tire tread. For this reason, it has good shock absorption properties due to uneven road surfaces, etc.
Ride comfort is good.

However, due to these characteristics, there is a problem in that the road grip force is reduced due to the weakness of the tread portion during turning, and the turning performance is not sufficient.

Conventionally, the problem with tires with such a spiral radial structure was that it was thought that it was not possible to change the performance of the tire to match the driving performance of the vehicle by changing the structure of the belt.

Therefore, the present invention provides a pneumatic radial tire for two-wheeled vehicles that has a spiral radial structure that maintains sufficient riding comfort, has sufficient road gripping force, and has sufficient turning performance to match the driving performance of the vehicle. The purpose is to provide tires.

(Means for Solving the Problem) The present inventors have focused on the difference in the usage range of the tread portion of the tire tread and the difference in required performance of the tire when a two-wheeled vehicle is traveling straight and when turning, and has developed various I did a lot of research. That is, as shown in FIG. 2.3, two-wheeled vehicle tires 5
The tread portion that contacts the road surface 7 changes greatly from the center portion 6a of the tread 6 to the side edge portions 6b when the vehicle is traveling straight and when the vehicle is turning at a large bank angle θ. on the other hand,
In tires for two-wheeled vehicles, emphasis is placed on ride comfort and straight-line running stability when driving in a straight line, and emphasis is placed on turning stability, road grip, etc. when turning, and the required performance differs between the two. Therefore, in order to make each part of the tread meet the required performance for each driving situation, we can change the belt's rigidity distribution by changing the number of belt cords and changing the bending rigidity of each part of the tread. I found out what I can do.

In addition, the boundary between the ground contact surface during straight running and when turning changes depending on the shape of the tread crown, but it is located approximately 174 tread width from the tread center E, so-called 1st layer 4.
It was found that it is near point P.

The present inventors further conducted various studies and arrived at the present invention.

That is, the pneumatic radial tire according to the present invention includes a carcass having cords arranged in a toroidal manner and substantially radially between a pair of beads, and a belt extending substantially circumferentially outside the crown portion of the carcass. , a pneumatic radial tire comprising: a tread covering the outside of the belt; Consisting of a pair of side ends, the number of cords at the side ends is 1.4 times the number of cords at the center.
It is characterized by being 2.4 to 2.4 times larger. Also,
Preferably, the belt has a cord extending spirally in the circumferential direction. Further, it is preferable that the center portion of the belt has a width that is approximately 1/2 of the tread width centered on the center of the tread.

Here, the number of cords inserted refers to the number of cords per certain length in the direction perpendicular to the cord direction of the cord.

Further, it is preferable that the number of strokes of the cord at the side ends is about 1.4 to 2.4 times greater than the number of cords at the center, more preferably 1.8 to 2.0 times. .

Here, the reason why the ratio is 1.4 to 2.4 is that if it is less than 1.4, the bending rigidity of the side edge is too small and the effect of the present invention is not sufficient, and if it exceeds 2.4, the bending rigidity of the side edge is too small. This is because the number of cords inserted in each section becomes too large, causing the cords to come into contact with each other.

Further, as shown in FIG. 4, the belt is preferably a so-called monospiral belt in which one cord is spirally wound in one or two layers in the circumferential direction of the tire. Alternatively, a plurality of strands may be wound around each other.

The belt cord member is preferably a tire cord such as steel cord, aromatic polyamide fiber, polyamide fiber (nylon, nylon 66, etc.), polyester fiber, polyvinylon fiber, or the like.

(Function) In the pneumatic radial tire of the present invention, the belt has a cord extending substantially in the circumferential direction, and the number of strokes of the cord at the side ends of the belt is a specific times the number of cords at the center. Due to its large size, it is installed on two-wheeled vehicles, and when driving straight, the number of hits in the center of the tread is small (the part with low bending rigidity makes contact with the ground. Therefore, even on uneven roads, the impact is small and the riding comfort is good, and straight-line stability is achieved. Also, when turning, the vehicle should have a large bank angle θ.
The tires touch the ground at the side edges of the tread, where the number of strokes is greater than the center, and where the bending rigidity is greater. Therefore, the road surface grip is excellent and the turning stability is good.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing an embodiment of a pneumatic radial tire according to the present invention, and the tire size is 170/60VR1.
It is 8. In FIG. 1, 11 is a pneumatic radial tire, and the pneumatic radial tire 11 is arranged between a pair of beads 12 in a toroidal shape and at a cord angle of approximately 90'' with respect to the radial direction, that is, the circumferential direction. The carcass 15 has a rubber-coated nylon cord 13.The cord angle of the nylon cord 13 is 90'~
It may be 70'. Nylon cord 13 has a cord thickness of 1
260 d/2 and the cord diameter is 0.61 m. The pneumatic radial tire 11 also includes a belt 1 extending substantially circumferentially outside the crown portion 15a of the carcass 15.
6 and a tread 17 covering the outside of the belt 16. Width Wl of tread 17? is 200mm. The belt 16 is made of a Kevlar cord made of aromatic polyamide fiber with a cord thickness of 1500 d/2 and a cord diameter of 0.63 ma+, which is arranged approximately in the tire circumferential direction from one tread end 17a to the other tread end 17b, that is, in the circumferential direction. The belt layer 16A is spirally wound in one layer at an angle O'C. The belt layer 16A consists of a central portion 16a centered on the tire equatorial plane E and a pair of side end portions 16b continuous on both sides of the central portion 16a, and the width W of the central portion 16a is the width W6 of the tread 17. 100m at 1/2 of
m and the width W0 of the side end portion 16b. is 50m, and the central part 1
6a and the side end portion 16b are connected at a so-called 1/4 point P. The number of cords in the center portion 16a of the belt layer 16A is 6/10, and the number of cords in the side end portions 16b is 1.
If the number of strokes in the center portion 16a is an index of 100 in the case of 2/10 holes, the number of strokes in the side end portions 16b is an index of 200. Therefore, the bending rigidity of the side end portions 16b is greater than that of the central portion 16a, resulting in excellent stability during turning and a large road grip force. On the other hand, the central portion 16a has a small bending rigidity and is less susceptible to impact on uneven road surfaces, providing good riding comfort. 18 is a rim.

Other than the above, this is a normal pneumatic radial tire, and the details will be omitted.

Next, four types of test tires (test example, comparative example 3) were prepared, and the effects of the present invention were confirmed.

The test tire sample was the same as the above-mentioned example shown in FIG. , are both equal to the number of implants in the central portion 16a of the embodiment,
Both indexes are 100. In the tire of Comparative Example 2, the number of cords in the center portion 16a and the side end portions 16b of the belt is equal to the number of cords in the belt in the example described above, and both are equal to the number of cords in the side end portion 16b of the example, and both have an index of 200. belongs to. In the tire of Comparative Example 3, the number of cords in the side end portions 16b of the belt is half the number of cords in the center portion 16a, which is smaller than the number of cords in the center portion 16a, and has an index of 50.

Tests were conducted on straight-line stability, turning stability, road grip, and ride comfort. In these tests, the test tires were mounted on a two-wheeled vehicle with a displacement of 750 cc, the test coat was run at a predetermined speed by a test driver, and comparisons were made through an actual vehicle feeling test in relation to the running characteristics of the vehicle. For straight-line stability, we compared the possibility of stable driving based on feeling, such as how well the vehicle stabilizes when external force is applied in the lateral direction while driving in a straight line. Turning stability was compared based on feeling, such as the so-called lean-in to take a large bank angle when turning a curve, the smoothness of the start-up, and the stability when external forces are applied. Road grip was compared based on feel, including braking force and driving force when driving straight, especially road grip when turning, camber thrust, and steering response to cornering force. Ride comfort was compared based on shock absorption and ride comfort when driving on uneven roads. These test results were compared with the evaluation result of the tire of Comparative Example 1 as 100, and are shown in the following table as an index. The larger the value, the better.

As shown in the table above, the test results show that, compared to Comparative Examples 1 to 3, the example sufficiently maintained ride comfort and showed superior results in straight-line stability, turning stability, and road grip. Ta.

(Effects) As explained above, according to the present invention, in a tire with a spiral radial structure, ride comfort performance is sufficiently maintained, road gripping force is sufficient, and turning performance is sufficient, which improves vehicle driving performance. A pneumatic radial tire for a two-wheeled vehicle can be provided.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing an embodiment of a pneumatic radial tire according to the present invention. FIG. 2.3 is a conceptual cross-sectional view showing the contact state of the tread portion of the two-wheeled vehicle tire when traveling straight and when turning, respectively. FIG. 4 is a perspective view of the belt. 11...Pneumatic radial tire, 12...
...Bead, 15...Carcass, 16...Belt, 16A...Belt layer, 16a...Center, 16b... Side edge, 17...Tread. Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) A carcass having cords arranged toroidally and substantially radially between a pair of beads, a belt extending substantially circumferentially outside the crown portion of the carcass, and a tread covering the outside of the belt. A pneumatic radial tire comprising: a belt comprising at least one belt layer having a cord extending substantially in the circumferential direction; A pneumatic radial tire characterized in that the number of cords at the side ends is 1.4 to 2.4 times greater than the number of cords at the center. (2) The pneumatic radial tire according to claim (1), wherein the belt has a cord extending spirally in the circumferential direction. (3) Claim (1) or (3) wherein the central portion of the belt has a width of approximately 1/2 of the tread width centered at the center of the tread.
2) The pneumatic radial tire described.