JPH0495506A - Radial tire - Google Patents

Abstract

PURPOSE:To prevent degradation in durability of a tire due to the growth and development of cracks by dividing reinforcing elements into bundles, each of which consists of several reinforcing elements, providing gaps between the adjacent reinforcing elements in each divided bundle, and providing wider distribution spacings between the bundles. CONSTITUTION:The belt 2 of a radial tire 1 is generally used as a rubber- sheathed layer, in which reinforcing elements made of steel filaments 3 arranged in parallel and diagonally to the equatorial face of the tire, are buried. In this case, with the above belt 2, in a conventional example shown in the upper column (a) in Figure, the arrangement of steel monofilaments 3 in the rubber- sheathed layer is set so that they are equally (s) spaced. On the other hand, in a specific example shown in the lower column (b), in the longitudinal cross section of the reinforcing elements, the steel monofilaments 3 are divided into bundles 4, each of which consists of, for example, two monofilaments. Further, distribution spacings deltaA are provided between the respective bundles 4, and the adjacent monofilaments 3 in the bundle 4 are arranged in parallel with gaps (g) provided in some places.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a radial tire, and particularly to a radial tire whose durability is improved by improving the belt that serves to reinforce the tread.

(Prior Art) The heald of a radial tire is generally used as a rubberized layer in which reinforcing elements of steel cords or steel filaments are embedded, usually at equal intervals, in parallel arrays diagonal to the tire's equatorial plane.

In contrast, reinforcing strips in which steel wires are juxtaposed in contact along the entire length of mutually adjacent wires, in particular bound to each other with wrapping wires or bonded with adhesive, are particularly suitable for use in belt reinforcing layers of vehicle rubber tires. Kaisho 63-2
It is disclosed in Japanese Patent No. 40402.

(Problem to be Solved by the Invention) In conventional belts in which the reinforcing elements are arranged in parallel at equal intervals, healds are not easily achieved regardless of whether or not adjacent wires are arranged in contact with each other along the entire length. The rubber facing the end of each reinforcing element at the width end of the belt is pecked every time the tire deforms when it touches the ground, so it first develops fine ranks, which eventually grow across the adjacent reinforcing elements, and then the belt The crack propagation speed is extremely fast, as it connects between the laminated layers and rapidly expands, resulting in so-called belt separation, and this determines the durability of radial tires.

It is important to suppress the growth of the crank mentioned above.
For this purpose, it is of course advantageous to have a wide spacing between adjacent reinforcing elements, but on the other hand, in order to simplify the reinforcing means required in addition to the strong demand for lighter tires, it is necessary to reduce the wire diameter of the reinforcing elements. As a result, in order to maintain the same tire strength, there is no choice but to increase the number of reinforcing elements, and the spacing between the reinforcing elements becomes narrower, which is incompatible with suppressing crack growth. However, the above publication does not mention anything about this point.

Therefore, in order to prevent deterioration of tire durability due to the subsequent growth of fine ranks that occur in the rubber at the width end of the heald facing the end of the reinforcing elements, it is necessary to By dividing each bundle into bundles and arranging adjacent reinforcing elements within the bundle so that they contact each other, a wide spacing between the bundles is ensured, thereby slowing down the growth of rubber fractures in the dispersed spacing between the bundles. The method is valid.

However, in this case, there is a disadvantage in fretting due to the penetration of rubber between adjacent reinforcing elements that come into contact with each other in the inner part of the tire, and furthermore, there is a disadvantage in fretting due to the fact that the reinforcing elements come into contact with each other due to the fact that moisture is absorbed from cuts made in the tread while the tire is running. Another problem faced by this type of reinforcing member is that it may penetrate through the area and cause rusting of the reinforcing element. It is an object of the present invention to provide a radial tire having the following characteristics.

[Means to solve the problem] The above object is accurately achieved by the configuration summarized below.

In radial tires, which are equipped with a belt used to reinforce the tire tread as a rubberized layer of reinforcing elements made of steel monofilaments arranged diagonally parallel to the tire's equatorial plane, individual reinforcements occupying the rubber bow layer. At least the majority of the elements are divided into bundles of up to several reinforcing elements, and within the bundles of each division, the reinforcing elements adjacent to each other are separated from each other except for partial mutual contact areas along the length and distributed throughout the east and outside. A radial tire, characterized in that, separated by spaced gaps, said bundle consists of a juxtaposed arrangement of reinforcing elements with a distributed spacing between adjacent reinforcing elements wider than the maximum spacing of said gaps.

The above purpose is met whether the bundle is made up of the same number of reinforcing elements or, conversely, if it is made up of several different reinforcing elements. Depending on the total number of reinforcing elements in a layer, there may be some reinforcing elements that are surplus to the bundle division, so reinforcing elements that protrude from the bundle division may be made up of a different number of reinforcing elements. As with bundles, it is possible to arrange them so that they are approximately evenly distributed over the entire circumference of the tire.

In the present invention, in order to prepare the rubberized layer of the steel monofilament reinforcing element to be applied to the belt, the belt is first produced by means of calendering rolls, in particular modified from comb-tooth rolls.

The comb-shaped rolls thereby serve to combine the steel monofilaments with a rubber sheet by means of calender rolls in a juxtaposed arrangement in which the steel monofilaments are divided into bundles of several, for example two, bundles.

The comb-shaped roll has a plurality of circumferential grooves for arranging the reinforcing elements in parallel, and this circumferential groove has a groove width wider than the total outer diameter of the number of reinforcing elements arranged in parallel. The thickness of the collar-like comb teeth extending between the adjacent bundles corresponds to the dispersion interval between the bundles.

If necessary, the comb-shaped rolls are moved slightly back and forth in a direction perpendicular to the unwinding direction of the reinforcing elements, so that there is no gap between adjacent reinforcing elements in the segmented bundle 6 when they come into contact with each other until the next contact occurs. Reinforcement element 9
gives rise to a slightly meandering juxtaposed arrangement.

When the Peltodorito produced in this way is used for belt reinforcement, the width of the treat is cut diagonally according to the required inclination of the reinforcing element with respect to the equatorial plane of the tire, and then the width edges of the Toledo are rejoined at the ears. It is made into a rubber strip, wound together with a liner into a raw fabric coil, and used for the tire building process.

(Function) As mentioned above, the process of rubber destruction at the width end of the belt of a radial tire causes repeated pecks in the rubber facing the end of the reinforcing element each time the tire deforms. Apart from the initial stage in which fine racks develop and grow along the surface of the reinforcing elements, when the reinforcing elements are arranged in parallel at regular intervals according to conventional techniques, they quickly grow across adjacent reinforcing elements. However, in the present invention, there is a problem in that the laminated layers of the belt are immediately connected to each other, leading to rapid expansion and progressing to heald separation. When this happens, the dispersion interval between the reinforcing elements and the bundle is much wider than when they are arranged at equal intervals, so the growth of cracks after the initial stage between adjacent reinforcing elements is separated by this dispersion interval. As a result, crack propagation between the heald stacks, which would then rapidly develop into belt separation, is effectively suppressed.

Here, only a small number of the reinforcing elements among the total number of reinforcing elements between the rubberized layers can be made into a bundle, and the reinforcing elements adjacent to the bundle may be distributed almost evenly over the entire circumference of the tire. Since the spacing between the reinforcing elements is wider than the spacing between the reinforcing elements when they are arranged at regular intervals according to the conventional technique, the propagation of cracks between the laminated layers of the healds, which occurs in the case of heald separation, is suppressed. However, the effect may not be significant in some cases, so the reinforcing elements covering at least half of the entire circumference are targeted when dividing the bundle. By doing this, the effect will be significant.

Although the gaps between the reinforcing elements adjacent to each other within the bundles of each section mentioned above go against the intention of increasing the above-mentioned dispersion spacing, they are at least partially designed to ensure the benefits of rubber penetration into these gaps. This requires physical contact.

In order to limit the number of reinforcing elements in a bundle to within a few, it is advantageous that the more reinforcing elements there are, the wider the dispersion interval can be. However, since crack propagation within the bundle is disadvantageous, it is necessary to make it into several bundles at most.

(Example) Example 1 The tread reinforcing belt 2 of a passenger car radial tire l of size 185/70R14 whose cross section is shown in FIG. Various arrangements of reinforcing elements when using treats are illustrated in FIGS. 2 to 6, in which 3 is a steel monofilament and 4 is a bundle thereof.

In the tread reinforcing belt 2, in the conventional examples shown in Figures 2 to 6 (a), the steel monofilaments 3 are arranged at equal intervals S in the rubberized layer, whereas in the lower part of each figure, the steel monofilaments 3 are arranged at equal intervals S. (b), (c) and (d) respectively show three locations A separated in the longitudinal direction of the reinforcing element for the examples of this invention.
, B and C, the steel monofilaments 3 are made into bundles 4 with 4 wires, 2 and 3 wires alternately, and 2 wires each, with a dispersion interval δ between the bundles 4, and Adjacent monofilaments 3 are arranged side by side with gaps g separating them here and there.

Attachments A, B, and C show the cross-sectional positions for the spacings δ and δ', and the size depends on the gap g in that cross section, but for any cross section, it is wider than the maximum gap g. do.

The gap g can be increased or decreased along the length of the steel monofilament, but the maximum spacing may be determined by the degree of rubber penetration. Although a steel monofilament with a circular cross section is used here, a steel monofilament with any cross-sectional shape such as an elliptical cross section may be used.

Each test tire shown in Table 1 was manufactured using reinforcing elements with different filament diameters according to the above, and the internal pressure was 1.
, 9 kg f/cm 2 and a load of 455 kg, and after running at a speed of 80 km/h for 60 minutes, it was dissected and the length of the crack that occurred at the width end of the belt 2 was measured. The results are listed in Table 1.

In addition, for the conventional examples shown in the upper rows (a) of Figures 5 and 6,
Examples of dividing less than half of the total circumference into bundles are shown in Figures 5(b) to (d).
Figures 6(b) to (d) show examples of dividing into bundles with more than half of the total circumference.
) are shown respectively. Table 2 shows the results.

Note that the belt 2 on the upper side is made of two layers, and the reinforcing elements of each layer intersect with each other at an angle of 24 degrees to the tire equatorial plane, and the layer on the tread side is slightly narrower than the layer on the carcass side. It has become. The above-mentioned cracks that occur near the belt width ends occur only in the tread side layer, and therefore the measurement results are also only for the tread side layer.

Based on this fact, it is of course possible to apply the rubberized layer of the present invention only to the layer on the tread side.

Example 2 For the tread reinforcing belt 2 of a radial tire for trucks and buses of size li/70 R22,5 shown in Fig. 7, the test tire had an internal pressure of 7 and OOkg f/a.
m'', loaded on a drum testing machine under the conditions of 2,600 kg, and run at a speed of 60 kII/h for 100,000 minutes, then dissected it and measured the length of the crack that occurred near the width edge of the heald. are shown in Table 3.

In addition, in contrast to the conventional example shown in the upper rows (a) of Figures 10 and 11, Figure 10 (b) shows an example in which half of the ends of the entire circumference are divided into bundles.
~(d) shows an example in which more than half of the circumference is divided into bundles.
The results are shown in Figures (b) to (d), respectively, and Table 4 shows the results.

In addition, the belt 2 has four layers laminated on the upper side, and the reinforcing elements of each layer are 18 degrees left, 18 degrees left, 18 degrees right, and 18 degrees right from the tread side.
It is inclined at 50 degrees to the right with respect to the tire equatorial plane.

The cracks that occurred near the ends of the belt width described above occurred only in the second layer from the tread side, and therefore the measurement results were also for only that layer.

Based on this fact, it is of course possible to use the rubberized layer of the present invention only in the second layer from the tread side.

(Effects of the Invention) This invention effectively suppresses the growth of cracks in the belt reinforcing element, which is the cause of separation at the width end of the belt, which has been considered a weak point in tread reinforcement of radial tires.
This can be achieved in conjunction with prevention of disadvantageous fretting and prevention of moisture intrusion through tread cuts.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a test tire for a passenger car, Figures 2, 3, 4, 5, and 6 are comparison diagrams of reinforcing element arrangements, and Figure 7 is a cross-sectional view of a test tire for a truck and bus. The cross-sectional views of the test tires, FIGS. 8, 9, 10, and 11 are comparative views of the reinforcing element arrangement. 1... Tire 2... Tread reinforcing belt 3... Steel monofilament 4... Bundle δ... Dispersion interval g...
Clearance Figure 3 S Figure 4

Claims (1)

[Scope of Claims] 1. In a radial tire equipped with a belt used to reinforce the tread of the tire as a rubberized layer of reinforcing elements made of steel monofilaments arranged diagonally parallel to the equatorial plane of the tire, in the rubberized layer: At least a large portion of the individual reinforcing elements occupying a total area of 100 mL are divided into bundles of up to several reinforcing elements, and reinforcing elements adjacent to each other within the bundle of each division are partially located along the length and inside and outside the bundle. The bundle is separated by a gap (g) which is spaced apart from each other except for areas of dispersive mutual contact through the bundle, and the bundle has a wider dispersion spacing (g) between the reinforcing elements adjacent to it compared to the maximum spacing of the gap (g). A radial tire characterized in that it consists of a juxtaposed arrangement of reinforcing elements. 2. The radial tire according to claim 1, wherein the bundle consists of the same number of reinforcing elements. 3. The radial tire according to claim 1, wherein the bundle comprises different numbers of reinforcing elements.