JPS6323923B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a radial tire for automobiles, and more specifically, to improve the uniformity of the tire (hereinafter referred to as uniformity) without impairing the tire's high-speed durability, the present invention relates to a radial tire for automobiles that has an improved structure, particularly in the belt portion, in order to improve the uniformity of the tire (hereinafter referred to as uniformity) without impairing the high-speed durability of the tire. It concerns radial tires. Conventionally, as shown in Fig. 1a and b, a fiber cord layer typically made of rayon, nylon, polyester, etc. is arranged at approximately 90 degrees to the tire equatorial plane.
That is, the carcass layer 1 is secured to a pair of bead wires at both ends, and in the area corresponding to the ground contact area, the angle between the cap lead T and the carcass layer 1 is approximately 10° to 30° with respect to the equatorial plane. In an automobile radial tire having metal cord layers, that is, belt layers 2 and 3 arranged in the .degree. direction, in order to improve high-speed durability, there is a layer between each of the belt layers 2 and 3 and the cap tread rubber. An edge cover 4 made of a heat-shrinkable cord layer having an angle of approximately 0° with respect to the circumferential direction of the tire is arranged so as to cover both ends of each of the belt layers 2 and 3. (Refer to Japanese Unexamined Patent Publication No. 14805/1983) However, although the original purpose of improving the high-speed durability of automobile radial tires can be achieved by arranging the edge cover 4 in the structure as described above, there are problems in the manufacturing process. As shown in Figure 2, there is one overlapping part S (hereinafter referred to as splice part) of the edge cover 4 described above at both ends of the belt layers 2 and 3, and this splice part S is different from other parts. Since the rigidity is greater than that of the tire, it has a negative effect on the uniformity of the tire, and as a result, it has the disadvantage of deteriorating the comfort, that is, the ride comfort, which is an important characteristic of the tire along with high-speed durability. . Conventionally, in order to eliminate the above-mentioned drawbacks, the splice portion S of the edge cover 4 has been unifyd by reducing the amount of splice, or eliminating it altogether, or narrowing the width of the edge cover 4 itself. Attempts have been made to reduce the negative impact on the omitty, but all of these methods still have problems, such as deterioration of high-speed durability, which is the original purpose of arranging the edge cover 4. The purpose of the present invention is to solve the above-mentioned problems and to provide an excellent automobile that improves the uniformity of the tires without impairing their high-speed durability and improves the livability, that is, the ride comfort. Our goal is to provide radial tires for A radial tire for automobiles according to the present invention that achieves the above object has two or more splice portions of the edge cover described above at each end of the belt layer, and furthermore, the splice portions of the edge cover are arranged substantially evenly in the circumferential direction of the tire. This feature is characterized by the fact that it is set at intervals. Next, in order to facilitate understanding of the present invention described above, the circumstances leading to the present invention will be briefly explained. As a result of repeated various tests, the inventors of the present invention discovered the following effects. That is, contrary to the conventional means described above which attempts to minimize the influence of the splice part of the edge cover, the number of splice parts is increased without changing the amount of the splice part, and the effect is substantially reduced in the tire circumferential direction. It has been found that uniformity can be greatly improved compared to conventional products by distributing the materials at equal intervals, since areas of high rigidity are not concentrated locally. RFV (maximum value of variation in force in the tire radial direction) is the most closely related to ride comfort among uniformity characteristics.
Since the change in rigidity of the lateral edge along the circumferential direction of the tire on the contact surface has the greatest influence, when the tread of the tire touches the ground, the edge cover is placed at a location that roughly corresponds to this edge. Improvements in the law
It has a great effect on improving uniformity. As mentioned above, it has been found that uniformity can be improved by increasing the number of splices in the edge cover and properly arranging the splices. If the number of splices is increased, the heat-shrinkable cord that makes up the edge cover will not be continuous for one full circumference of the tire, resulting in a decrease in circumferential tensile force, which will reduce the webbing at both ends of the steel belt that occurs during high-speed rotation. It is no longer possible to prevent the rising tendency, and the edge cover cannot have much of an effect on high-speed durability, which is the original purpose of inserting the edge cover. Therefore, in order to eliminate the above-mentioned drawbacks, the inventors of the present invention have proposed that the heat-shrinkable cord layer constituting the edge cover is substantially continuous around the tire, and that the splice portion of the edge cover is connected to each of the belt layers. Two or more splices are provided at the end, and the splices are substantially equally spaced in the circumferential direction of the tire.
In other words, they have invented a radial tire for automobiles in which the splice portion is point symmetrical with respect to the axis of rotation of the tire. DESCRIPTION OF THE PREFERRED EMBODIMENTS The above-mentioned radial tire for automobiles according to the present invention will be explained in detail by way of examples with reference to the drawings. FIG. 3 is an explanatory diagram of a main part of a radial tire for an automobile according to a first embodiment of the present invention, and FIG. 4 is an explanatory diagram of a main part of a radial tire for an automobile according to a second embodiment of the present invention. First, the first embodiment shown in FIG. 3 will be described. In the figure, 2 and 3 indicate steel belt layers, and 4 and 5 indicate edge covers. In this example, two edge covers 4 are provided at both ends of each belt on the front and back sides of the tire.
5 are arranged one on top of the other, each edge cover 4,
It has one splice part for every 5. The edge covers 4 and 5 have widths of W ₁ and W ₂ , respectively, and each edge cover 4 and 5 is provided with one splice portion, and the splice amount is preferably 5 mm or more. The positions of the splice parts of the edge covers 4' and 5' on the front side of the tire are arranged at approximately equal intervals in the circumferential direction of the tire, so in this embodiment, they are arranged at points symmetrical with respect to the rotation axis of the tire. Ru. In addition, the edge covers 4'' and 5'' on the back side of the tire have similar splice parts and the arrangement of the splice parts, and the positional relationship of the splice parts of the front and back edge covers is as follows.
The splice portions of the front edge covers 4', 5' and the splice portions on the back side are arranged at approximately equal intervals on the circumference of the tire. In this embodiment, since two edge covers 4 and 5 are substantially arranged at both ends of the belt layer, the high speed is improved compared to a tire having a conventional structure in which substantially one edge cover is arranged. will improve. The purpose of the present invention is to increase the number of splices of the edge cover without reducing high-speed durability as described above.
Further, even if the width of the edge cover is different between the 4th layer and the 5th layer as in this embodiment, no problem arises in the effects of the present invention. Next, a second embodiment shown in FIG. 4 will be described. In the figure, 2 and 3 are steel belt layers, and 4', 5' and 4'', 5'' are edge covers. In this embodiment, the edge covers 4', 5' and 4'', 5'' are arranged in two directions in the circumferential direction.
Each edge cover has one splice part, and it has the same effect as the first embodiment described above in that it increases the number of edge cover splices in the tire as a whole. do. In this embodiment, it is possible to ensure high-speed durability almost equivalent to that of a tire with a conventional structure in which the width of the edge cover is (W ₁ + W ₂ ). Even if the thickness of the cord is different between the 4th layer and the 5th layer, and even if the width of the edge cover is different between the 4th layer and the 5th layer as shown in the figure, no problem will arise in the effects of the present invention. Edge covers 4', 5' and 4'' in this case,
5″ each has one splice part,
The splice amount is preferably 5 mm or more. The splice parts of the edge covers 4' and 5' on the front side of the tire are arranged at approximately equal intervals in the circumferential direction of the tire, so the splice parts of the edge cover 4' and edge cover 5' are located at a point with respect to the rotational axis of the tire. placed in symmetrical positions. In addition, the edge covers 4'' and 5'' on the back side of the tire have similar splice parts and splice parts, and in terms of the positional relationship between the splice parts of the front and back edge covers, the splices of the front edge covers 4' and 5' The splice portion and the splice portion on the back side are arranged at approximately equal intervals on the circumference of the tire. In each of the above-mentioned embodiments, the outer edge of the edge cover is located outside the outer edge of the steel belt layer, but the outer edge of the edge cover is located on the second steel belt layer (3 in the figure). ), the effect of the present invention can be achieved even if the relative positional relationship between the edge cover and the steel belt layer is not maintained as shown in the figures of this embodiment. Of course, this will not cause any inconvenience. Furthermore, in terms of tire uniformity,
As mentioned above, with RFV, if all splices on the front and back sides of the tire are arranged at approximately equal intervals, that is, symmetrically with respect to the axis of rotation of the tire, the improvement effect will be significant. LFV (maximum value of lateral force variation) is greater than when the splice arrangement order on the front and back sides is arbitrary, even when the total splice parts are arranged at approximately equal intervals in the circumferential direction of the tire. As mentioned above, the improvement effect is greater when they are arranged at approximately equal intervals on the circumference of the tire, or in other words, arranged alternately. This is improved with RFV as long as the splices on the front and back of the tire are oriented in the same direction and the total number of splices are approximately the same spacing apart, whereas LFV is Since the splices face in the opposite direction, if the front and back splices are arranged alternately along the circumferential direction of the tire, the lateral force generated when the splices pass through the tire tread will be directed in opposite directions one after another. This is because the opposite forces cancel each other out, and the LFV, that is, the lateral force fluctuation, is improved. Next, regarding the experimental results comparing the high-speed durability and uniformity of the conventional radial tire for automobiles and the radial tire for automobiles of the present invention,
This will be explained with reference to FIGS. 5a to 5d and Table 1 below. The test results for high-speed durability shown in Table 1 are shown as the average value of two tires, and the test results for uniformity are shown as the average value of 20 tires. 205/60HR15 was used as the test tire. High-speed durability test method: load 510Kg, air pressure 2.2
Kg/ ^cm2 , speed of 81km/h for 2 hours, then 2
Cool for an hour. After that, load 510Kg, air pressure 2.2
This is done by resetting the vehicle to Kg/cm ² and driving from 121 Km/h to 8 Km/h in 30 minute increments until it breaks down. Uniformity test method is automotive standard
Based on JASO607-74. In addition, as a heat-shrinkable edge cover, a nylon cord layer with a width of 50 mm, 840d/2, and an angle of 0° was used in Comparative Example 2 shown in Figure 5 b, and a nylon cord layer with a width of 50 mm in Comparative Example 3 shown in Figure 5 c. , 1260d/2, angle of 0° is used, and in the case of the embodiment of the present invention shown in FIG. An edge cover was placed above the belt layer as shown. Note that no edge cover was provided in Comparative Example 1 shown in FIG. 5a.

[Table] As is clear from Table 1 above, Comparative Examples 2 and 3
It can be seen that in the tire with the conventional structure shown in , when each edge cover is arranged in the conventional structure described above, the high-speed durability improves, but the uniformity deteriorates in inverse proportion to this. In contrast, it is clear that the tire of the present invention has significantly improved uniformity without impairing high-speed durability. The uniformity values shown in Table 1 are the average values of the 20 test tires as mentioned above.
Comparative example 2 with edge cover arranged in conventional structure,
It can be seen that the tire of the present invention is excellent in RFV not only when compared with tire No. 3 but also when compared with Comparative Example 1 in which no edge cover is provided. As explained above, according to the present invention, it is possible to ensure high-speed durability equal to or greater than that of tires manufactured with a conventional structure, and the uniformity has a greater width than tires manufactured with a conventional structure. Improvements can be made, and tires with excellent uniformity, ie, ride comfort, can be obtained without compromising high-speed durability, ie, safety.

[Brief explanation of the drawing]

Figure 1a is a cross-sectional view of a conventional automobile radial tire with edge covers arranged at both ends of the belt, Figure 1b is an enlarged plan view of the same essential parts, and Figure 2 is an explanatory diagram showing the spliced state of the edge cover. ,
3 and 4 show embodiments of the present invention, FIG. 3 is an explanatory diagram of the main parts of a radial tire for automobiles according to the first embodiment of the present invention, and FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of main parts of a radial tire for automobiles according to an example. In addition, FIGS. 5a to 5d are explanatory diagrams of main parts of each tire used in an experiment to compare high-speed durability and uniformity between a conventional tire and a tire according to the present invention, where a is Comparative Example 1 and b is Comparative Example 2. ,
c shows the tire of Comparative Example 3, and d shows the tire of the present invention. 1... Carcass layer, 2, 3... Belt layer, 4, 5...
Edge cover.

Claims (1)

[Claims] 1. A tread, a pair of beads, a carcass layer extending from one of the beads to the other, and a belt layer disposed between the carcass layer and the tread in a direction of approximately 10° to 30° with respect to the equatorial plane of the tire. and an edge cover made of a heat-shrinkable cord layer provided to cover both ends of the belt layer and arranged at approximately 0° with respect to the circumferential direction of the tire, wherein the edge cover overlaps. A radial tire for an automobile, characterized in that two or more edge covers are provided at each end of a belt layer, and the overlapping portions of the edge covers are arranged at substantially equal intervals in the circumferential direction of the tire.