JPH0353122B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to radial tires, and more particularly to improvements in radial tires having blocks separated by grooves on at least both sides of the tread. Nowadays, with the development of automobile-only road networks, the performance of vehicles has increased significantly, and radial tires have the great structural advantage of being able to significantly improve road surface strength and tire rigidity. However, as mentioned above, radial tires have high rigidity, so the ground contact pressure on both sides of the tread part, that is, the shoulder part, tends to be higher than the ground contact pressure in the center part. The disadvantage is that it wears out. In addition, in the case of front tires, which are subject to extra load due to load transfer during cornering and braking, wear on the outer tread side (shoulder) of the vehicle is significant due to the alignment of the steering wheel and vehicle. In general, it was necessary to change the position of tires every 10,000 to 20,000 km. However, if this position is swapped between the left and right tires of the vehicle, the direction of rotation of the tires will be reversed and the direction of wear will be reversed, increasing tire noise while driving. Currently, it is only possible to exchange. The above-mentioned tendency is particularly noticeable in radial tires in which blocks separated by grooves are arranged on both sides of the tread portion for the purpose of improving drainage performance, which is one of the important performance requirements for tires. The present invention was developed as a result of experiments and studies to solve the above-mentioned problems. Therefore, an object of the present invention is to prevent uneven wear (step wear, shoulder wear) on the tread by devising the tread structure of the blocks arranged at least on both sides of the tread, thereby increasing the running life and preventing noise. Another object of the present invention is to provide a radial tire that allows freedom in tire replacement positions and improves running stability on wet roads. That is, the present invention provides a radial tire having blocks separated by grooves on both sides of the tread portion, in which a plurality of straight kerfs are arranged in parallel to each other on the tread surface of the block, independent of the grooves, and The angle of the straight kerf with respect to the tire circumferential direction is 80° to 90°, the distance e between the end of the straight kerf and the groove is 2 mm to 6 mm, and the arrangement interval t of the straight kerf is 3 mm to 10 mm. The gist of the invention is a radial tire characterized in that the ratio tmin/tmax of the minimum interval tmin to the maximum interval tmax is 0.5 to 1.0. Hereinafter, the present invention will be explained in detail by way of examples with reference to the drawings. 1 and 2 show a radial tire according to an embodiment of the present invention, FIG. 1 is an explanatory plan view of the main part, and FIG. 2 is an enlarged explanatory view of the main part in cross section taken along the arrows in FIG. 1. In the figure, G indicates a radial tire according to an embodiment of the present invention, which includes a pair of left and right bead portions (not shown), a pair of left and right sidewall portions (not shown) connected to the bead portions, and a pair of left and right sidewall portions (not shown) connected to the bead portions. It consists of a treaded part 10 located between the parts,
A carcass layer 1 having a cord angle between the bead portions with respect to the tire circumferential direction of about 90° or 70° to 80°.
Two belt layers 2 are disposed on the carcass layer 1 in the tread portion 10 and intersect with each other at cord angles of 15° to 35° with respect to the tire circumferential direction. 10
grooves 1 in the tire circumferential direction and in the tire meridian direction.
A large number of blocks 20 divided by 1 are provided. In the present invention, at least on both sides of the tread portion 10, that is, on the tread surface of each block 20 of the shoulder portion 10s, a plurality of straight kerfs 21 are provided independent of the grooves 11 and parallel to the tire circumferential direction at an angle of 80° to 90°. It is located in To explain more specifically, in this embodiment, as shown in the figure, the blocks 20 are arranged over the entire surface of the tread portion 10, but this is at least on both sides of the tread portion 10, that is, on both the left and right shoulder portions 10s. If the blocks 20 separated by the grooves 11 are provided, the drainage performance of the tire can be improved, and wet road running stability such as steering stability and braking performance when running on a wet road can be improved. The above-mentioned arrangement interval t of the straight calf 21 is 3 mm ~
It needs to be 10mm. This is because if the distance t is less than 3 mm, the rigidity of the block 20 will be insufficient and the steering stability will be reduced. Furthermore, if the interval t exceeds 10 mm, the effect of arranging the straight kerfs 21, that is, the effect of subdividing the tread surface of the block 20 by the straight kerfs 21 (details will be described later), will not be sufficiently exhibited, and the so-called shoulder This is because wear and step wear become significant. Furthermore, if the distance t exceeds 10 mm, the noise will increase significantly, especially when the tires rotate in reverse, and the freedom of tire changing positions will be hindered. Furthermore, the above-mentioned arrangement interval t of the straight curves 21
The intervals between blocks or within the same block do not necessarily have to be the same, but the value of the ratio tmin/tmax of the minimum interval tmin to the maximum interval tmax must be set within the range of 0.5 to 1.0. It is preferable to set it within the range of 0.8 to 1.0. If the spacing between the straight kerfs 21 is within the range mentioned above, the block 20 will not experience partial step wear and increase noise, and even if the tires are replaced on the left or right side of the vehicle and used in reverse rotation. Increase in noise can be significantly suppressed. Note that the width s of the straight kerf 21 is preferably 0.6 mm to 1.2 mm. Further, the above-mentioned straight cuff 21 is formed by a groove 11 surrounding the block 20 in which it is disposed, as described above.
The distance e between the end 21a of the straight cuff 21 and the groove 11, (the distance between the end 21a and the groove 11 on the extension line in the angular direction of the straight cuff 21) ) is preferably 2 mm to 6 mm. This is because if e is less than 2 mm, abnormal wear will occur between the groove 11 and the end 21a of the straight kerf 21, and if e exceeds 6 mm, the effect of subdivision due to the arrangement of the straight kerf 21, This is because the effect of improving step wear and shoulder wear is not sufficiently exhibited. Furthermore, the depth d of this straight kerf 21 is equal to the depth d of the groove 11.
Assuming that the depth is D, it is desirable that the ratio d/D be within the range of 0.3 to 1.0. This is d/D
If it is less than 0.3, the effect of subdivision by arranging the straight kerf 21, that is, the effect of improving step wear and shoulder wear, will not be sufficiently exhibited, and d/D
This is because if it exceeds 1.0, the rigidity of the block 20 will be lowered more than necessary, which is not desirable. In addition, the depth d of the straight curve 21 is set so that d/D is 0.3 to 1.0.
If it is set within this range, it will contribute to improving drainage performance and can also significantly improve the above-mentioned wet road running performance. Furthermore, the straight cuff 21 is arranged parallel to the tire circumferential direction at an angle of 80° to 90° as described above. If running stability during road running is reduced and the straight kerfs 21 are not arranged in parallel, multiple straight kerfs 21
This is because unnecessary movement occurs on the tread surface of the block 20 which has been subdivided by this, which is undesirable as it may cause local step wear or cracks in the rubber of the block 20 from the kerf end 21a. In this embodiment, the angle θ of the straight cuff 21 with respect to the tire circumferential direction is set to 90°. Furthermore, in the present invention, the cuff 21 disposed on the tread of the block 20 is formed in a straight shape because if the cuff 21 is formed in a straight shape, the drainage path can be shortened and good wet road running performance can be obtained. The calf end 21 is caused by local step wear that tends to occur in this bent part or abnormal deformation of the bent part.
This is because it is possible to prevent cracks from being induced in the rubber of the block 20 from a. The straight curve 21 having the above structure is not only provided on both sides of the tread portion 10, that is, the block 20 of the shoulder portion 10s, but also provided with a circumferentially continuous rib on the block at the center of the tread portion or at the center of the tread portion, as shown in FIG. It is even more preferable to provide the rib with a straight cuff 21 having the above structure in terms of movement characteristics in a wet path. Next, the effects of the present invention will be explained using experimental examples. First, the specifications of the example tires of the present invention used in each experiment are as shown in Table 1.

【table】

[Table] And the block shape of the comparative tire is the first.
This tire is the same as the tire of the present invention shown in FIG. 2 and does not have a straight kerf. Experimental Example 1 In this experiment, the example tire of the present invention and the comparative example tire with the specifications shown in Table 1 were respectively mounted on the left front wheel of a vehicle, and after traveling 10,000 km on a 100% paved road, the tires shown in Figure 1 were The wear condition of the k-k section was examined. As a result, the results shown in FIGS. 3 and 4 were obtained. FIG. 3 is a partially enlarged sectional view of the section corresponding to k-k in FIG. 1 of the comparative example tire after the above-mentioned experiment, and FIG. 4 is a partially enlarged sectional view of the section corresponding to k-k in FIG. It is a partially enlarged sectional view of the section. As is clear from a comparison between FIG. 3 (comparative example tire) and FIG. 4 (example tire), it can be seen that the example tire has extremely small step wear compared to the comparative example tire. Experimental Example 2 In this experiment, the example tire of the present invention and the comparative example tire with the specifications shown in Table 1 were used at 0 to 100 km/
Indoor noise measurements were conducted in the following three cases within the hr range. (1) New tires (2) After driving 1000 km, the same rotation direction as while driving (driving conditions are the same as in experiment (1)) (3) After driving 1000 km, in the opposite rotation direction as while driving (driving conditions are the same as in experiment (1)) ) As a result, the measurement results shown in FIGS. 5 and 6 were obtained. FIG. 5 is a diagram showing the results of each indoor noise measurement of the comparative tire, and FIG. 6 is a diagram showing the results of each indoor noise measurement of the tire of the present example. In each figure, the vertical axis shows the sound pressure level (dB), and the horizontal axis shows the traveling speed (Km/hr), and the solid line in the figure is the above-mentioned line.
The measurement results for the tire in (1), the dashed-dotted line indicate the measurement results for the tire in (2) above, and the broken lines indicate the measurement results for the tire in (3) above. As is clear from Figure 5, compared to when the tire was new, the noise of the comparative example tire increased significantly after traveling 10,000 km.Especially when the tire was rotated in the opposite direction after traveling 10,000 km, the noise suddenly increased, and the noise on both sides of the vehicle It can be seen that when the tire position is changed, the noise increases significantly. On the other hand, as is clear from FIG. 6, the sound pressure level of the tire according to the embodiment of the present invention increased less after each run than when the tire was new, and even when the tire position was changed between the left and right positions of the vehicle. It can be seen that the increase in noise is extremely small. Experimental Example 3 In this experiment, the longitudinal load was measured at the area corresponding to E in Figure 1, that is, the center of the tread area, and the area corresponding to Figure 1 F, that is, the shoulder area, of the example tire of the present invention and the comparative example tire with the specifications shown in Table 1. The ground pressure against was measured. As a result, the measurement results shown in FIG. 7 were obtained. In Fig. 7, the vertical axis shows the vertical load, and the horizontal axis shows the ground pressure. The solid line E in the figure is the measurement result of the area corresponding to Fig. 1 E of the tire of this example, and the solid line F is the result of the measurement of the tire of this example. In addition, the broken line shows the measurement result of the part corresponding to FIG. 1E of the comparative example tire, and the broken line shows the measurement result of the part corresponding to FIG. 1 F of the comparative example tire. As is clear from FIG. 7, the comparative example tire is
A large difference occurs between the ground contact pressure at the center of the tread and the ground pressure at the shoulder near the normal longitudinal load, but in this example tire, the ground pressure at the center of the tread and the ground pressure at the shoulder differ near the normal longitudinal load. It can be seen that there is almost no difference between the two. Experimental Example 4 In this experiment, the wear of each block at the corresponding parts A, B, C, and D in Figure 1 was measured for the Example tire of the present invention and the Comparative example tire with the specifications shown in Table 1. . As a result, the measurement results shown in FIG. 8 were obtained. Figure 8 shows the above tires installed on the vehicle and 100
These are the results of measuring the wear of each of the above-mentioned parts after driving on a paved road for 4,500 km, 13,000 km, and 22,000 km. As is clear from FIG. 8, the wear of the areas corresponding to A and D in FIG. It can be seen that the performance is superior to that of the comparative tire. FIG. 9 is a diagram showing the estimated minimum running life of each tire, that is, the estimated running life at the fastest-wearing part, by replacing the above-mentioned experimental results with the relationship between running distance and wear. In Figure 9, the vertical axis shows the wear and the horizontal axis shows the mileage. In the figure, the ▲ mark is the comparative example tire installed on the left side of the front wheel of the vehicle, and the ● mark is the actual example tire installed on the left side of the front wheel of the vehicle. The example tire, the △ mark indicates the comparative example tire mounted on the right side of the front wheel of the vehicle, and the ◯ mark indicates the present example tire mounted on the right side of the front wheel of the vehicle. As is clear from FIG. 9, it can be seen that the tire life of this example tire can be extended by about 70% than that of the comparative example tire. Experimental Example 5 In this experiment, the angle θ of the straight kerf arranged in the example tire of the present invention with the specifications shown in Table 1 with respect to the tire circumferential direction was set to 90°, 80°, 60°, 30°, and 0.
The wet road motion characteristics were measured when the temperature was set at . The measurement results were as shown in Table 2. Each value shown in Table 2 is expressed as an index based on the maximum speed at which a circle with a radius of 30 m can be drawn on a wet road surface when each of the above tires is mounted on a vehicle, with the measured value of the comparative example tire being set as 100. Therefore, the larger the value, the higher the maximum speed, that is, the higher the grip level of the tire tread, and the better the running stability when running on wet roads.

[Table] As is clear from Table 2, the example tire of the present invention, that is, the tire with the straight kerf arranged at an angle of 80° to 90° with respect to the tire circumferential direction, is different from the comparative tire without the kerf and the straight tire. It can be seen that even when the shaped kerf is arranged, the motion characteristics, that is, the running stability on a wet road are superior compared to tires where the arrangement angle θ with respect to the tire circumferential direction is other than 80° to 90°. As described above, the present invention provides a radial tire having blocks separated by grooves at least on both sides of the tread portion, in which a plurality of straight kerfs are provided on the tread surface of the block in a circumferential direction of the tire, independent of the grooves. They are arranged parallel to each other at an angle of 80° to 90°, and the distance e between the end of the straight kerf and the groove is
from 2mm to 6mm, and the arrangement interval t of the straight kerf from 3mm to
10mm, the ratio tmin/tmax of the minimum interval tmin and maximum interval tmax is set to 0.5 to 1.0, which prevents uneven wear (step wear, shoulder wear) on the tread part, increases running life, prevents noise, and It is possible to freely change the tire changing position, and it is also possible to improve running stability on wet roads.

[Brief explanation of drawings]

1 and 2 show a radial tire according to an embodiment of the present invention, FIG. 1 is an explanatory plan view of the main part, FIG. 2 is an enlarged explanatory view of the main part in cross section taken from FIG. Figures 4 and 4 are partially enlarged cross-sectional views in the circumferential direction of the comparative example tire and the example tire after running 10,000 km, and Figures 5 and 6 show the indoor noise measurement results of the comparative example tire and the example tire. 7 is a diagram showing the ground contact pressure measurement results of the comparative example tire and the present example tire, and FIG. 8 is a diagram showing the block wear measurement results of the comparative example tire and the present example tire,
FIG. 9 is a diagram showing estimated running life. 10...tread portion, 11...groove, 20...block, 21...straight kerf.

Claims (1)

[Claims] 1. In a radial tire having blocks separated by grooves at least on both sides of the tread portion, a plurality of straight kerfs are arranged in parallel to each other on the tread surface of the block, independent of the grooves, and each of the straight kerfs is Angle from 80° to the tire circumferential direction
90°, the distance e between the end of the straight kerf and the groove is 2 mm to 6 mm, and the arrangement interval t of the straight kerf is 3 mm to 3 mm.
Within the range of 10mm, its minimum spacing tmin and maximum spacing
A radial tire characterized by having a ratio of tmin/tmax to tmax of 0.5 to 1.0.