JPS59145605A - Radial tire - Google Patents

Abstract

PURPOSE:To prevent unbalanced abrasion of a tread part by arranging, on a tread of blocks divided by means of grooves provided at least on both sides of the tread part, the plural number of straight kerfs, independent of said grooves, at a predetermined angle with the circumferential direction of a tire. CONSTITUTION:The tread part 10 of a radial tire G is provided with many blocks 20 divided by means of each groove 11 in the circumferential direction and the meridian direction of the tire. The plural number of straight kerfs 21 are arranged in parallel with each other at an angle of 80 deg.-90 deg. with the circumferential direction of the tire independently of said grooves 11, on the tread of each block 20 of both sides of the tread part 10, that is, shoulder parts 10s. At this time, an interval (t) for arranging the straight kerfs 21 is preferably set within 3mm.-10mm. while the bradth (s) of each kerf 21 is preferably set within 0.6mm.-1.2mm.. Thus, unbalanced abrasion of the tread part 10 can be prevented and not only draining of the tire but also stability of traveling on the damp road can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radial tire, and more particularly to an improvement in a radial tire having blocks separated by grooves on at least both sides of the tread portion.

Nowadays, with the development of automobile-only road networks, the performance of vehicles is increasing 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, that is, part of the shoulders, tends to be higher than the ground pressure in the center. 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 of the vehicle,
Due to the relationship between the steering wheels and the alignment of the vehicle, the wear of the outer tread side portion (part of the shoulder) of the vehicle is significant, and it is generally necessary to replace the position of the tire every 10,000 to 20,000 miles.

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.

In particular, the above-mentioned tendency is 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 reduce uneven wear (step wear) of the tread by devising a non-locking tread structure disposed on at least both sides of the tread.

To provide a radial tire capable of increasing running life, preventing noise, freeing tire replacement positions by preventing wear and shoulder wear, and improving running stability on wet roads.

That is, the present invention provides a radial tire having blocks separated by grooves on at least both sides of the tread portion, in which a plurality of straight kerfs are provided on the tread surface of the block, independent of the grooves, at an angle of 80° to the circumferential direction of the tire. 90°
A radial tire characterized by being arranged in parallel with
This is the summary.

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 number 8 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 arrows It is.

In the figure, G is 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 bead portions (not shown). It consists of a tread part 10 located between the sidewall parts, and a Φ tatami carcass layer 1 having a cord angle of about 90'' or 70° to 80° with respect to the tire circumferential direction is mounted between the bead parts, Further, two belt layers 2 are disposed on the carcass layer 1 in the trend part 10 and intersect with each other at cord angles of 15° to 35° with respect to the tire circumferential direction. 4 grooves 1 in the tire meridian direction
A large number of blocks 20 are provided which are divided by 1.

Further, in the present invention, a plurality of straight kerfs 21 are provided on the tread surface of each block 20 of at least the both side lug shoulder portions 10s of the tread portion 10, independently of the grooves 11.
are arranged parallel to the tire circumferential direction at an angle of 80° to 90°.

To explain more specifically, in this embodiment, as shown in the figure, blocks 20 are formed over the entire surface of the tread portion 10.
However, this means that the grooves 1 are arranged at least on both sides of the tread portion 10, that is, on both the left and right sides.
If the blocks 20 divided by 1 are provided, 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 curves 21 is 3 mm to 10 mm.
It is desirable to do so. This is not preferable because if the distance t is less than 3 mm, the rigidity of the block 20 will be insufficient and the steering stability will deteriorate. Furthermore, if the interval t exceeds lQ'im, 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 undesirable as wear and step wear become significant. Furthermore, the interval t.

If it exceeds 10 degrees, the increase in noise will be significant, especially when the tire rotates in reverse, which will impede the freedom of tire replacement positions, which is not preferable.

Furthermore, the arrangement interval t of the straight curves 21 described above does not necessarily have to be the same between each block or within the same block, but the value of the ratio 'mln/l max between the minimum interval tmin and the maximum interval tmax' 0.5
It is preferable to set within the range of ~1.0, and more preferably within the range of 0.8 to 10.

If the spacing between the straight kerfs 210 is within the above-mentioned range, the noise will not increase due to partial step wear on the block 20, and in the evening, the ears can be exchanged at the left and right positions of the vehicle and used in reverse rotation. It is also possible to significantly suppress the increase in noise.

The width S of the straight kerf 21 is preferably 0.6 wIL to 1.2 wIL.

The above-mentioned straight kerf 21 still needs to be arranged independently of the groove 11 surrounding the block 2o in which it is arranged as described above, but the end 21a of this straight kerf 21
The distance Me between the groove 11 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 curve 21) is
It is desirable to set it as 2 dragon - 6n. This means that e is 21n1
If it is less than 1L, abnormal wear will occur between the groove 11 and the end 2Ia of the straight kerf 21, which is undesirable.If e exceeds 6 L, the effect of subdivision due to the arrangement of the straight kerf 21 will be reduced. In other words, the effect of improving step wear and shoulder wear is not sufficiently exhibited.

Further, it is desirable that the depth d of the straight kerf 21 is such that the ratio d/D is within the range of 0.3 to 1.0, where D is the depth of the groove 11. This is because if d/D is less than 0.3, the effect of segmentation by the straight calf 21, that is, the improvement effect of step wear and shoulder wear, will not be sufficiently exhibited, and if d/D is less than J 1 This is because if it exceeds .0, the rigidity of the block 2o will be lowered more than necessary, which is not desirable. In addition, the depth d of the straight kerf 2IO is d/
If D is set in the range of 0.3 to 1.0, it will contribute to the improvement of drainage performance, and the above-mentioned wet road running performance can also be greatly improved.

Furthermore, the reason why the straight cuff 21 is arranged parallel to the tire circumferential direction at an angle of 80° to 90° as described above is that if the straight cuff 21 has an angle θ of 80° with respect to the tire circumferential direction, then If the running stability during running on a wet road is reduced and the straight kerfs 21 are not yet arranged in parallel, the block 20 is subdivided by a plurality of straight kerfs 21.
This is because there is a risk that excessive movement will occur on the tread surface, causing local step wear and cracks in the rubber of the block 20 from the kerf end 21a, which is undesirable. 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 distance can be shortened and good wet road running performance can be obtained. This is because it is possible to prevent the occurrence of local step wear that is likely to occur in this bent portion, and the occurrence of cranking from the calf end portion 21a to the rubber of the block 2o due to abnormal deformation of the bent portion.

The straight cuff 21 having the above structure is not only provided in the block 2o of the both side lug shoulder portions 10s of the tread portion 1o, but also continuous in the circumferential direction at the block at the center of the tread portion or at the center of the tread portion as shown in FIG. It is more preferable to provide a rib and provide the straight cuff 21 of the above configuration on the rib in terms of movement characteristics in a wet path.

Next, the present invention will be explained in detail using experimental examples. - First, the specifications of the example tires of the present invention used in each experiment are as shown in Table 1.

(Margins below this page) Table 1 □□ The comparative tire has the same block shape as the tire of the present invention shown in FIGS. 1 and 2, and does not have a straight kerf.

Experimental Example 1 In this experiment, an example tire of the present invention and a comparative example tire with the specifications shown in Table 1 were installed on the left side of the front wheel of a vehicle, and after driving for 10,000 hours on a 100% paved road, wX
The wear condition of the part shown in Fig. 1 was examined. As a result, the results shown in FIGS. 3 and 4 were obtained.

Figure 3 shows the first comparison tire after the above experiment.
4 is a partially enlarged sectional view of the corresponding part of the tire shown in FIG. 1 after the above-described experiment.

Figure 3 (comparative tire) and Figure 4 (example tire)
As is clear from the comparison, it can be seen that the tire of this example has significantly less step wear than the tire of the comparative example.

Experimental Example 2 In this experiment, indoor noise measurements were carried out on the Example tire of the present invention and the Comparative example tire having the specifications shown in Table 1 in the following three cases in the range of 0 to 100 IGn/hr.

(11 New tires (2) After driving 10,000 km, the same rotational direction as while driving (driving conditions are the same as in experiment (1)) (After driving 3110,000 km, the rotational direction is opposite to that 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 both figures, the vertical axis represents the sound pressure level (dB), and the horizontal axis represents the traveling speed (KIII/hr).
;The solid line in the figure is the measurement result of the tire in (1) above, the dashed line is the measurement result of the tire in (2) above,
The broken lines indicate the measurement results for the tire in (3) above.

As is clear from Figure 5, the noise of the comparative example tire increased significantly after traveling for 10,000 km compared to when the tire was new, and especially when the tire was rotated in the reverse direction after traveling for 10,000 km, the noise suddenly increased. It can be seen that the noise increases significantly when the tire positions are changed between the left and right positions of the vehicle.

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 increases less after each run than when the tire was new, and the tire position was changed between the left and right positions of the vehicle. However, it can be seen that the increase in noise is extremely small.

Experimental Example 3 In this experiment, we examined the longitudinal characteristics of the example tire of the present invention and the comparative example tire having the specifications shown in Table 1, in the area corresponding to E in FIG. The ground pressure against the load 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 contact pressure.
The measurement result of the relevant part, solid line F is Fig. 1 F of this example tire.
The broken line [F] shows the measurement result of the corresponding part in Fig. 1 E of the comparative example tire, and the broken line [F] shows the measurement result of the corresponding part of Fig. 1 F of the comparative example tire. ε As is clear from FIG. 7, in the comparison tire, there is a large difference between the ground contact pressure at the center of the tread and the ground contact pressure at a part of the shoulder near the normal longitudinal load, but the tire of this example It can be seen that there is almost no difference between the ground pressure at the center of the tread section and the ground pressure at the shoulder section near the load.

Experimental Example 4 In this experiment, A, B, and C in FIG.
, D of each block was measured.

As a result, the measurement results shown in FIG. 8 were obtained.

Figure 8 shows the above tires installed on the vehicle, and the tires were driven on 100 inch paved roads at 4,500 Km, 13,000 Km, and 220 Km.
These are the results of measuring the wear of each of the above-mentioned parts after traveling for 00 km.

As is clear from FIG. 8, the wear of the parts A and D in FIG. It can be seen that the wear resistance 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 Fig. 9, the vertical axis shows the wear, and the horizontal axis shows the mileage. In the figure, the mark "mu" indicates a comparative example tire installed on the left side of the front wheel of the vehicle, and the mark . Example tires, Δ marks indicate comparative tires mounted on the right side of the front wheel of a vehicle, and ○ marks indicate tires of the present example mounted on the right side of the front wheel of a vehicle.

As is clear from FIG. 9, it can be seen that the tire of this example can have a longer lifespan of approximately 70 inches than the comparative tire.

Experimental Example 5 In this experiment, the angle θ of the straight kerf with respect to the tire circumferential direction, which was arranged on the tire according to the invention having the specifications shown in Table 1, was 90'', 80', and 60°.

The wet road motion characteristics were measured at 30° and 0°.
.

The measurement results were as shown in Table 2.

In Table 2, the maximum speed at which a circle with a radius of 39 m can be drawn on a wet road surface with each of the above tires mounted on a vehicle is expressed as an index, with the measured value of the comparative example tire 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 2 As is clear from Table 2, the example tire of the present invention, that is, the tire in which the straight kerf is arranged at an angle of 80" to 90" with respect to the tire circumferential direction, is different from the comparative example tire in which no kerf is arranged and It can be seen that even when a straight cuff is arranged, the dynamic characteristics and running stability on a wet road are excellent compared to tires whose 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 a block divided into grooves at least on both sides of a trend portion, in which a plurality of straight kerfs are provided on the tread surface of the block in the circumferential direction of the tire, independent of the grooves. against 8
Since they are arranged parallel to each other at 90" to 0", it is possible to prevent uneven wear (step wear, shoulder wear) on the trend part, increase running life, prevent noise, and make it possible to free up the tire replacement position. Furthermore, running stability on wet roads can be improved.

[Brief explanation of the drawing]

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.
Figure II '-II arrow cross-sectional enlarged explanatory view of main parts, Figures 3 and 4 are 1oooo of the comparative example tire and the present example tire.
Partially enlarged sectional view in the circumferential direction after running Kll+, No. 5
6 and 6 are diagrams showing the indoor noise measurement results of the comparative example tire and the present example tire, FIG. 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 the comparative example FIG. 9 is a diagram showing the block wear measurement results of the tire and the tire of this example, and FIG. 9 is a diagram showing the estimated running life. 10...Tread portion% 11...Groove, 20...
・Block, 21... Straight calf. Agent Patent attorney Shin Ogawa − Patent attorney Ken Noguchi Patent attorney Kazuhiko Saishita Figure 5 Traveling speed (km/hr) Figure 7

Claims (1)

Scope of Claims: A radial tire having blocks separated by grooves on at least both sides of the tread portion, in which a plurality of straight kerfs are provided on the tread surface of the blocks, independent of the grooves, at an angle of 80° with respect to the tire circumferential direction. A flat tire characterized by being arranged in parallel at ~90°.