JPS63166605A - Radial tire for heavy vehicle - Google Patents

Abstract

PURPOSE:To restrain exfoliation between plies and rubber exfoliation of a belt layer, in the captioned tire for bus and so forth, by forming a continuous recession groove in the tire circumferential direction between the specific part on the buttress part surface and the curve change point of a side wall part. CONSTITUTION:The intersection P2 of a hypothetical arc 7 in the tire rotational axis direction which passes the groove bottom 8a of a tread groove and is parallel the surface of a tread part 5 and the surface of a buttress part 6 is found out. And between this point P2 and the curve change point Fl of a side wall part, a recession groove 9 which is continuous in the tire circumferential direction and whose groove bottom 9a is in the shape of the concentric circle with the surface of the buttress part 6 is formed. Also, the depth of this recession groove 9 is set less than approximately 5 mm, and the length L at approximately 5 to 30 mm. By this constitution, temperature rise and stress concentration of rubber, at the both ends of the belt layer 4 is reduced and eased, and exfoliation between plies and rubber exfoliation of the belt layer can be restrained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention reduces and alleviates heat generation and stress concentration in radial tires for trunks and buses used under extreme usage conditions such as high loads and high internal pressures. , relates to a so-called radial tire for heavy vehicles in which inter-ply and/or rubber peeling at both ends of the belt layer is reduced.

[Prior art]

Tires for trucks, buses or construction vehicles are used for heavy loads,
This type of tire is used under extreme conditions such as high internal pressure, and combined with the large rubber wall thickness of the tread, this type of tire has a high heat storage effect, and as a result, the tire generates a lot of heat.
Inter-ply peeling and/or rubber peeling occurs frequently at both ends of the belt layer where stress concentration is severe. Conventionally, in order to solve this problem, the thickness of the tread part has been reduced, the temperature rise of the rubber at both ends of the belt layer has been suppressed by using rubber that generates less heat in the shoulder part, and the temperature rise of the rubber at both ends of the belt layer has been suppressed. Attempts have been made to alleviate the stress concentration or to strengthen the defect of poor adhesion between the steel cord and rubber at both ends of the belt layer by covering the belt layer with a fiber cord layer, but a sufficient effect cannot necessarily be expected.

[Problems to be solved]

The present invention simultaneously reduces and alleviates the temperature rise and stress concentration of the rubber near both ends of the belt layer, even under extreme usage conditions such as high loads, high internal pressures, and driving on rough roads, thereby preventing peeling between the plies of bell) 11. , rubber! ! The purpose of this invention is to propose a radial tire for heavy vehicles that effectively suppresses 11 separation.

[Technical means]

The present invention will be described with reference to FIG. 1, which shows the right half of a sectional view of a radial tire l, which is an embodiment of the present invention.A radial tire 1 is secured by folding both ends around a pair of left and right bead cores 2. carcass 3 and this carcass 3
A belt layer 4 made of a non-stretchable cord is arranged on the outside of the crown part of the belt, and a tread part 5 is arranged on the outside of the belt layer 4.
and a buntless portion 6 having a center of curvature on the outside of the tire between the tread end TE and the tire maximum width position WE, and a groove of a tread groove 8 formed on the surface of the tread portion 5. An imaginary arc 7 passing through the bottom 8a in the direction of the tire rotational axis parallel to the tread surface and the buttress portion 6
This radial tire for a heavy vehicle is characterized in that a concave groove 9 continuous in the tire circumferential direction is formed between an intersection point P2 with the surface and a sidewall change point P1.

In the present invention, a concave groove 9 that continues in the tire circumferential direction is formed at a predetermined position of the buttress portion 6. According to the inventor's research so far, the peeling of the belt layer 4 often occurs at the end P3 of the third layer, and this is because the stress concentration and temperature rise are particularly significant at the end P3. As shown in FIG. 2, the temperature rise at the end P3 increases approximately in proportion to the distance jljll from the end P3 to the tread surface. In other words, Figure 2 shows a tire with a 10.00R20 rib pattern running at 80kse/h on an indoor durability drum.
Then, the temperature change at the end P3 when the tire is driven under 100% load according to the JIS standard until the tire temperature becomes constant is calculated by the distance 1111.
As shown in the relationship with , it can be seen that as 11 increases, the temperature increases. Further, FIG. 3 shows the shortest distance I12 from the intersection P5 of the carcass 3 and a line drawn perpendicularly to the tire rotation axis direction from the end P4 of the second layer to the surface of the buff stress 6, and the temperature at the end P3 of the third layer. 12
It can be seen that the temperature at the end P3 increases as the temperature increases. The tires had a 10r 0OR20 rip pattern and the running conditions were the same as in Figure 2.

Furthermore, FIG. 4 shows the relationship between the temperature of the end portion P3 and the tire durability performance in the indoor durability test, and it can be seen that the higher the temperature, the lower the durability.

Here, the vertical axis is a load of 140% of the JIS standard, and a speed of 80 km/h to 2
It shows the time (minutes) of the final step when running until failure as a step for each time.

From the test results, it is found that if the length of the paths 11j1 and 72 is reduced, the temperature rise can be alleviated and the durability can be improved, but a decrease in the distance z1 causes the end portion of the belt layer 4 to be exposed at the end of wear of the tread portion 5. On the other hand, a decrease in the distance 12 is a decrease in the tread radius of curvature or a radius of curvature R1 of the buff tress portion 6.
However, the former adversely affects the tire life, while the latter is undesirable because it increases strain in the buttress portion 6 and promotes stress concentration at the end P3.

The present invention solves the above problem by forming the groove 9 in the buttress portion 6.

Here, the groove 9 needs to be located inside the intersection point P2 between the virtual arc 7 in the direction of the tire rotation axis and the surface of the buttress portion 6. The reason for this is that if the groove 9 is located on the tread portion 5 side, At the end of wear, the concave grooves 9 are exposed on the ground contact surface, which adversely affects the wear life of the tread portion. On the other hand, unless the groove 9 is located radially outward from the sidewall inflection point P1, there is no effect of suppressing the temperature rise at both ends P3 of the third layer of the belt layer 4.

Next, the groove 9 needs to be continuous in the circumferential direction of the tire, and it is preferable that the depth D is 5 m or less and the length is within the range of 5 to 30 m. In particular, the bottom surface of the groove 9 9a preferably has a circular shape concentric with the buff dress portion 6 in order to alleviate distortion. Further, in the present invention, it is also possible to form a plurality of grooves extending in the circumferential direction of the tire in the buttress portion 6. In the present invention, the carcass 3 is preferably made of a highly elastic cord such as steel cord or aramid, but it is also possible to use a machined fiber cord such as nylon, polyester, or rayon.
It is a radial structure arranged below ``, preferably below 5@.

The belt layer 4 is preferably made of four layers of steel cord, and the second layer of the carcass 3 is the widest, and the first layer and the third layer have approximately the same width. Note that the belt layer 4 can also have a composite structure of a ply of organic fiber cord such as aramid and a ply of steel cord.

〔Effect of the invention〕

As described above, in the present invention, since grooves extending in the tire circumferential direction are formed at predetermined positions of the buttress portion, the temperature rise at both ends of the third layer of the belt layer can be suppressed, and stress concentration at the both ends can be alleviated. Therefore, ply peeling and rubber peeling of the belt layer can be effectively reduced.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the tire of the present invention, and Figs. 2 and 3 show the temperature and distance at the end of the third layer of the belt layer! 1.12, and FIG. 4 is a diagram showing the relationship between the temperature of the end portion and durability. 1-tire, 2-bead core, 3-carcass, 4-belt layer, 5-tread section, 6--
-Buttress portion, 7.-Virtual line, 8-Tread groove, 9-Concave groove. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Tadashi Naemura jllllllj II4 Sendanma (9)

Claims (3)

[Claims] (1) A carcass that is secured by folding both ends around a pair of left and right bead cores, a belt layer made of a non-stretchable cord placed outside the crown portion of this carcass, and a tread portion placed outside the belt layer. and a buttress portion having a center of curvature on the outside of the tire between the tread end TE and the tire maximum width position WE, and the tread surface passing through the groove bottom of the tread groove formed on the tread surface. for a heavy vehicle, characterized in that a concave groove continuous in the tire circumferential direction is formed between an intersection point P2 of the buttress portion surface and an imaginary circular arc parallel to the tire rotation axis direction and the sidewall portion inflection point P1. radial tire. (2) The radial tire according to claim 1, wherein the bottom surface of the groove has a concentric circular shape with the surface of the buttress portion. (3) The tread end side of the bottom surface of the groove is formed into a circular shape concentric with the surface of the buttress portion, and the maximum width position side is formed with a larger radius of curvature than the tread end side. Radial tires listed in section.