JPH0466305A - Pneumatic, radial tire for passenger car - Google Patents

Abstract

PURPOSE:To enhance durability of a tire in high speed running and prevent rust generation, in a steel-belt reinforcing layer by using an unstranded polyamide monofilament having a flat section as a reinforcing cord for a fiber-cord reinforcing layer, which covers the tread surface side of both ends of the steel- belt reinforcing layer in the tread part. CONSTITUTION:Steel-belt reinforcing double layers 5 consisting of steel cords are arranged between a tread 1 and a carcass 3. In addition, on both ends of the steel-belt reinforcing layer 5, fiber-cord reinforcing layers 6 are arranged on the right and left sides in such a manner that the layers 6 cover the respective tread surface sides. In addition, each fiber-cord reinforcing layer 6 is constituted by an unstranded, polyamide monofilament having the flat section, which is wound in such a manner that it covers at the same time both the end of a steel-belt reinforcing layer 5mu on the tread surface side and the end of a steel-belt reinforcing layer 5d on the lower side. At this time, the direction of the major diameter of the flat section is aligned with the direction of the plane of the fiber-cord reinforcing layer 6, while the direction of the cord is determined within a range of 0 deg. to 1 deg. with respect to the circumferential direction of the tire.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a pneumatic radial tire for passenger cars, and more particularly to a steel belt reinforcement that improves high-speed durability and further reduces the problem of rusting in the steel belt reinforcement layer. The present invention relates to a pneumatic radial tire for passenger cars having a layer.

[Prior art]

Generally, high-performance pneumatic radial tires for passenger cars have a steel belt reinforcing layer made of steel cords with significantly higher strength and modulus than other fibers, with the cord directions crossing each other. Two layers are arranged so as to increase the speed, thereby improving high-speed durability and handling stability. Furthermore, in order to improve performance for high-speed running, polyamide fiber cords are arranged on the tread side of both ends of the two steel belt reinforcing layers so as to be substantially Oo in the circumferential direction of the tire. A reinforcing layer is arranged, and the hoop effect of this fiber cord reinforcing layer suppresses lifting of both ends of the steel belt reinforcing layer due to centrifugal force, thereby preventing separation at the edge portion.

However, in order to satisfy the high-speed durability of VR standard high-speed tires that have recently been adopted in various countries, the above configuration lacks the hoop effect of the fiber cord reinforcing layer, so multiple fiber cord reinforcing layers are required. Attempts are being made to cover the area in layers. However, when multiple layers are used, the thickness of the fiber cord reinforcing layer increases, which increases heat generation, and there is a limit to improving high-speed durability. Moreover, this also resulted in the disadvantage of increasing the weight of the tire. To make matters worse, since the cords that make up the fiber cord reinforcing layer are made up of a large number of small-diameter multifilaments twisted together, if trauma to the tread reaches the fiber cord reinforcing layer, Due to the capillary action of the fiber cord, moisture and impurities are sucked into the cord and diffused inside, which causes rust and separation at the ends of the steel belt reinforcing layer.

[Problem to be solved by the invention]

The purpose of the present invention is to solve the above-mentioned problems of pneumatic radial tires that have a steel belt reinforcing layer and cover both ends with fiber cord reinforcing layers, and to improve high-speed durability due to the hoop effect of the fiber cord reinforcing layer. To provide a pneumatic radial tire for a passenger car which solves the problem of rusting of a steel belt reinforcing layer while improving its properties.

[Means to solve the problem]

A pneumatic radial tire for a passenger car according to the present invention that achieves the above object has a tread portion made of two steel cords.
The steel belt reinforcing layers are arranged so that the cord directions cross each other, and the tread sides of both ends of the steel belt reinforcing layers are each covered with a single fiber cord reinforcing layer made of untwisted polyamide monofilament with a flat cross section. ,
The major diameter direction of the flat cross section of the polyamide monofilament is along the plane direction of the fiber cord reinforcing layer, and the cord direction is within the range of 0° to 1° with respect to the tire circumferential direction. .

The above-mentioned untwisted polyamide monofilaments have higher modulus than conventional multifilament fiber cords, so they are arranged at an angle of 0° to 1° with respect to the tire circumferential direction in the fiber cord reinforcing layer. Then, the end portion of the steel belt reinforcing layer can be restrained with a high hoop effect.

In addition, in the fiber cord reinforcing layer, the untwisted polyamide monofilament is arranged so that the long axis direction of its flat cross section is along the in-plane direction of the fiber cord reinforcing layer, which is equivalent to increasing the number of ends. In addition, compared to conventional circular cross-section cords, the maximum value of bending strain can be reduced and fatigue resistance can be improved.

Furthermore, unlike twisted cords, polyamide monofilament does not have a capillary phenomenon, so it does not cause rust to the steel belt reinforcing layer.

A fiber cord reinforcing layer made of untwisted polyamide monofilaments with a flat cross section, which has this effect, is made by stretching one or several polyamide monofilaments in a spiral shape endlessly around the steel cord reinforcing layer. It is best to construct it by winding it.

With such a configuration, there is no step-like splice portion formed in the fiber cord reinforcing layer, and the uniformity of the tire can be improved.

The lower limit of the dimension C (width) in the tire width direction of this fiber cord reinforcing layer is preferably at least 20 mm, and the upper limit is preferably 30% of the total width of the steel cord reinforcing layer.

The present invention will be explained below with reference to embodiments shown in the drawings.

In the pneumatic radial tires for passenger cars shown in FIGS. 1 and 2, ▪ is a tread, and 2 is a sidewall extending on both sides of the trend. Reference numeral 3 designates a carcass consisting of one or two layers provided inside the tire, each layer of which is made of fiber cords, each forming an angle of 70 to 90 with respect to the circumferential direction of the tire. This car
The waste 3 is wound around the bead core 4 at both ends so as to be folded back from the inside to the outside of the tire.

A two-layer steel belt reinforcing layer 5 made of steel cord is arranged between the tread l and the carcass 3, and a fiber cord reinforcing layer 6 is placed on each end of the steel belt reinforcing layer 5 so as to cover the tread side. are placed on the left and right. The two layers of steel belt reinforcements F5d and 5u are arranged so that their cord directions are opposite to each other at an angle of 15° to 30° with respect to the tire circumferential direction, and intersect with each other. Of these two steel belt reinforcement layers,
It is preferable that the steel belt reinforcing layer 5u on the tread side is configured to be narrower by at least 5n+m at both ends than the steel belt reinforcing layer 5d on the lower side.

The fiber cord reinforcing layer 6 arranged separately on both sides is wound so as to simultaneously cover the end of the steel heald reinforcing layer 5u on the tread side and the end of the steel heald reinforcing layer fi5d on the lower side, and each has a flat cross section. It is constructed by winding untwisted polyamide monofilament in an endless spiral while gradually shifting the pitch. Moreover, when wound in this manner, the major axis direction of the flat cross section is aligned with the surface direction of the fiber cord reinforcing layer 6,
In addition, the cord direction is set within a range of 0° to 1° with respect to the tire circumferential direction. These left and right fiber cord reinforcing layers 6 are each made of only a single layer, and the steel belt reinforcing layer 5
It is designed to cover the edges of the

Since the polyamide monofilament used in the present invention is untwisted and only one large diameter piece constitutes the tire cord, it has higher modulus characteristics than conventional twisted cord. In other words, conventional twisted coats provide cord convergence and fatigue resistance by twisting together a large number of small-diameter multifilaments, but conversely, the twisting reduces the modulus. I try to let them do it.

However, in the case of monofilament, since it consists of only one large-diameter fiber, twisting is not necessary to give it convergence, and it is not twisted, it can exhibit a higher modulus than a twisted cord. be.

In addition, fatigue resistance decreases due to non-twisting, but in the present invention, the cross-sectional shape of the monofilament is flattened, and the major axis direction of the flattened cross section is aligned with the surface direction of the fiber cord reinforcing layer. Therefore, the maximum value of bending strain is reduced by zjs, thereby compensating for the decrease in fatigue resistance and aiming to improve it.

The reason why the decrease in fatigue resistance can be compensated for as described above can be explained as follows from FIG.

In FIG. 3, the cords constituting the fiber cord reinforcing layer 6 are composed of cords 60 with a flat cross-section (indicated by solid lines) having the same cross-sectional area, and cords 60'' with a circular cross-section (indicated by chain lines). Now, if these two types of cords undergo the same out-of-plane bending deformation around the neutral axis N, the bending strain ε generated in each cord is expressed by the following 2. Ru.

ε=ε, +zk However, ε. is the strain Z at the neutral axis of bending Z is the distance k from the neutral axis of bending is the change in curvature From this bending strain 2, the bending strain ε is maximum at the top of the cord that is farthest from the neutral axis N of bending. .

As is clear from FIG. 3, the code 6o of the flat cross section is
Since the maximum distance Za is smaller than the maximum distance zb of the circular cross-section cord 60' (Za < Zb), the maximum value of the bending strain is calculated as the circular cross-section cord 60'.
It can be made smaller than that of . Therefore, by arranging the untwisted monofilament with a flat cross section as described above, the fatigue resistance can be supplemented and even improved. In order to make such an effect more noticeable, the aspect ratio R (-major axis/minor axis) should be 1.5 or more,
More preferably, it is 2.0 or more.

The polyamide constituting the monofilament is not particularly limited, but polyhexamethylene adipamide (nylon 66), polyepsilon caprolactam (nylon 6
) etc. are preferably used.

In the present invention, the fiber cord reinforcing layer covering the ends of the two-layer steel belt reinforcing layer is composed of polyamide monofilament having a high modulus as described above. It can exhibit a higher hoop effect than that of the reinforcing layer, and exhibits high high-speed durability. The cord angle at this time is 1″′
If it is larger than this, it will be difficult to obtain the same good high-speed durability unless the width of the fiber cord reinforcement layer is widened, which will result in an increase in weight. turn into.

In addition, the fiber cord reinforcing layer is made of polyamide monofilaments with a flat cross section arranged in such a way that the long axis direction is along the surface direction of the reinforcing layer, which substantially increases the number of ends (cord density per unit width). It is possible to obtain the same effects as those described above, and it is possible to increase the in-plane rigidity of the tread.

The number of ends of such flat cross-section polyamide monofilament varies depending on the type of tire, but the cord spacing W (W in Fig. 3) is 0.1 to 2.0 cm,
More preferably 0°2 to 1. A range of Onm is preferable from the viewpoint of improving durability.

Furthermore, as described above in Figure 3, with flat cross-section polyamide monofilament, the distance from the neutral axis of bending to the outer surface of the cord can be smaller than that with circular cross-section cords, so when using circular cross-section cords, In comparison, the bending stiffness can be reduced without reducing the tensile stiffness, so the ride comfort can be improved.

In addition, in the present invention, the polyamide monofilament used in the fiber cord reinforcing layer weighs 2.25g/2.25g/in the state when used in a green tire after being treated with an adhesive.
dThe elongation rate under load is 6.5% or less and 150℃
It is desirable that the dry heat shrinkage rate is 4.5% or less. By suppressing the elongation rate after adhesive treatment to 6.5% or less, the initial modulus of the reinforcing cord used in the fiber cord reinforcing layer can be increased, and the high-speed durability of the radial tire can be further improved. . Further, by controlling the dry heat shrinkage rate to 4.5% or less, it is possible to suppress a decrease in durability at the end portion due to cord shrinkage during vulcanization molding.

〔Example〕

Three types of nylon 66 monofilaments with a thickness of 3000D and an aspect ratio R of 1 (circular) and 2.3 were spun. Next, these nylon 66 monofilaments were subjected to heat treatment temperature and treatment tension ()Is as shown in the table.
: heat cent tension, NL: normalized tension) and 2.25 g/
4 having an elongation rate at d and a dry heat shrinkage rate at 150°C.
We have manufactured various types of tire cords. As the adhesive at this time, RFL, a mixture of redulucin/formalin initial fasteners and rubber latex, was used.

Each of these adhesive-treated cords is wound six times on the tread side of both ends of the two-layer steel belt reinforcing layer, as shown in Figure 1, so that the cord angle with respect to the tire circumferential direction is 0.
By forming a fiber cord reinforcing layer embedded in unvulcanized rubber with a width of 45 mm and 4.5 turns of spiral winding at an angle of 3°, the number of 30 pieces is 15 cm, and the tire size is 205150R1585V. Four types of pneumatic radial tires were manufactured, consisting of Examples 1, 2.3 and Comparative Examples. Both tires are 2
The cord angles of the steel belt reinforcing layers of the layers with respect to the tire circumferential direction were each 25 degrees, and they were arranged in a mutually intersecting relationship.

On the other hand, according to the conventional method, nylon 66 multifilament was twisted to a thickness of 840D/2. Number of twists: 46/10c
m S / 46 times / 10 cm Z twisted cord was made, and it was treated with adhesive under the conditions shown in the table, and the elongation rate at 2.25 g/d and dry heat at 150°C as shown in the table were obtained. A tire cord with a shrinkage rate was manufactured. Next, this adhesive-treated cord was wound once on the tread side of both ends of the two-layer steel belt reinforcing layer each having the same structure as in Example 1 described above, so that the cord angle with respect to the tire circumferential direction was 0. 4. In a spiral shape so that the angle is 3°.
Wrap 5 times, 50 pieces 15cm in length to match the torque denier of the fiber cord reinforcing layer of Example 1 etc.
By forming a fiber cord reinforcing layer embedded in unvulcanized rubber with a diameter of 45 mm, the tire size was reduced to 2.
A pneumatic radial tire of Conventional Example 1 having a size of 05150R1585V was manufactured.

Similarly, using the same cord as in Conventional Example 1, the number of windings on the tread side at both ends of the two-layer steel heald reinforcement layer was changed to a width of 4.
The tire size is 20 when wrapped 9 times within 5mm.
A pneumatic radial tire of Conventional Example 2 having a size of 5150R1585V was manufactured.

The high-speed durability of the above six types of tires was measured using the following indoor high-speed durability test method, and the results shown in the table were obtained.

<Indoor high-speed durability test method> Measurement was performed under the following conditions in accordance with the certified extended destructive test of JIS high-speed performance test. Rim 15X5'72. Load 455kg,
The air pressure is 3.0 kg/cm2, the initial speed is 170 k+n/hr, and the speed is 10 k/hr every 10 minutes.
The speed was increased by m/hr until the tire broke, and the high-speed durability was evaluated based on the speed at which the tire broke. The measurement results were expressed as an index, with the tire according to the conventional example being 100. A larger index means better quality.

(Blank below this page) From the table above, it can be seen that the tires according to Examples 1 and 2.3 of the present invention are superior in high-speed durability compared to the tire according to Conventional Example 1.2. In addition, a comparative example tire in which the fiber cord reinforcing layer was composed of circular cross-section monofilament,
The high-speed durability is inferior to that of Conventional Example 2.

(Effects of the Invention) As described above, the pneumatic radial tire for passenger cars of the present invention includes two steel belt reinforcing layers on the tread portion and one fiber cord reinforcing layer on each end of the tread side. By using untwisted flat cross-section polyamide monofilament for the reinforcing cord of the fiber cord reinforcing layer, high-speed durability can be improved.In addition, since it is made of monofilament, it has a moisture absorption and diffusion effect due to capillary action. This eliminates the problem of rusting of the steel heald reinforcing layer.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional perspective view of a main part of a pneumatic radial tire for a passenger car according to an embodiment of the present invention, and FIG. 2 is a developed view of the main part showing only the carcass and reinforcing layer of the same radial tire. FIG. 3 is an explanatory diagram schematically showing the relationship between the cords of the steel belt reinforcing layer and the cords of the fiber cord reinforcing layer. 1... Tread, 3... Carcass, 5.5u, 5d
...Steel belt reinforcement layer, 6...Fiber cord reinforcement layer.

Claims (1)

[Claims] Two steel belt reinforcing layers made of steel cords are arranged in the tread portion so that the cord directions cross each other, and the tread sides of both ends of the steel belt reinforcing layers are each made of a single layer made of untwisted polyamide monofilament with a flat cross section. Covered with a single fiber cord reinforcing layer, the major axis direction of the flat cross section of the polyamide monofilament is aligned with the surface direction of the fiber cord reinforcing layer, and the cord direction is set within a range of 0° to 1° with respect to the tire circumferential direction. Pneumatic radial tires for passenger cars.