JPH0455102A - Radial tire - Google Patents

Abstract

PURPOSE:To closely improve the riding comfortableness and wandering performance by using a total aromatic polyester fiber cord as a carcass cord, forming the carcass by two carcass plys which are arranged at a specified angle and inclined in the opposite directions, and arranging a belt cord at a specified angle. CONSTITUTION:A carcass 7 is formed by two, inner and outer carcass plys 7a, 7b where carcass cords are arranged at an angle from 65 deg. to 88 deg. to the equator of a tire. The respective carcass cords are inclined in the opposite directions to the equator of the tire so as to improve the lateral rigidity of the tire and increase the camber thrust. By adopting a total aromatic polyester fiber cord as a carcass cord, high vibration damping efficiency and shock absorptivity are attained so as to improve the riding comfortableness and remarkably improve the wandering performance. A belt layer 9 is of a three-layer structure comprising the first, second and third belt plys 11,12,13, and a tread portion 5 is reinforced by providing a hoop effect extending over the total width thereof. As the first belt ply 11 is formed by arranging a belt cord at an angle from 40 deg. to 70 deg. to the equator of the tire, the wandering performance and the riding comfortableness are remarkably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radial tire that can improve riding comfort and wandering properties with a simple structure, and can be particularly suitably used for heavy-load vehicles.

[Conventional technology]

With improved road networks and higher performance vehicles, tires for heavy-duty vehicles such as trucks and buses are desired to have high high-speed running performance, and tires with a radial structure have been widely used in recent years.

However, radial tires for heavy-duty vehicles have conventionally formed a carcass using two carcass plies with steel carcass cords arranged almost perpendicular to the tire equator, resulting in insufficient tire lateral rigidity. As a result, as shown in FIG. 5, for example, when driving on a sloped road surface S, the camber thrust F generated in the slope direction becomes small, inducing tire drift toward the valley side.

In addition, since the carcass is tightly tightened with a strong belt layer, the in-plane rigidity of the tread and the longitudinal rigidity of the tire are extremely high, resulting in poor ride comfort. When the driver crosses a section diagonally, the reaction force received from the stepped section increases, which not only impairs the vehicle's ability to pass over the step but also causes the tire to deviate from the steering direction.

On the other hand, with the bias tire A1, when running on the slope, the tread surface follows the slope, as shown by the dashed line in the figure, so that the outer diameter of the tire on the mountain side becomes smaller than that on the valley side. Due to this difference in the displacement distance of the tread surface between the mountain side and the valley side, a camber torque T around the Z axis that directs the tire toward the mountain side is generated. On the other hand, in the radial tire A2, due to the high tire longitudinal rigidity and tread rigidity, the outer diameter of the tire is almost uniform, with undulations occurring on the tread surface on the valley side, thereby reducing camber torque and increasing the tread strength for gripping the handle. Increasing the steering holding force, etc. will reduce the wandering property to 1] along with the tire flow toward the valley side and the reaction force from the stepped portion. Therefore, in order to improve the riding comfort and wandering properties of such radial tires, conventional efforts have been made to increase the belt cord angle and to reduce tread rigidity by using soft tread rubber. There is.

[Problem to be solved by the invention]

However, increasing the belt cord angle leads to a decrease in the hoop effect, which impairs tire running performance.
On the other hand, the use of soft rubber causes many disadvantages, such as reduced wear life and poor durability.

In view of this situation, the inventors of the present invention have conducted extensive research in order to improve ride comfort and wandering properties without causing the above-mentioned disadvantages.

As a result, the carcass was constructed using two carcass plies with a cord angle relative to the tire equator of 65 to 88 degrees, which is smaller than that of conventional tires, and each carcass ply was arranged so that the carcass cords intersected between the braais. I devised a plan to do so. The purpose of this is to improve the tire's lateral rigidity and to transfer part of the drag effect to the carcass.This makes it possible to increase the belt cord angle while increasing camber thrust while maintaining running performance. ,
It is possible to moderate the tread rigidity and measure the increase in camber torque and the direction of ride comfort.

However, in order to adopt such a tire structure,
The premise is to use a new tire cord with low mass and high strength as the carcass cord. In other words, when conventional steel cords are used, as the number of carcass plies increases, the tire weight increases significantly, reducing running performance and fuel efficiency, and when nylon cords or polyester cords are used, the strength of the cords themselves decreases. It is inferior to the horn, and it is difficult to obtain satisfactory carcass strength. In addition, fully aromatic polyamide fibers, so-called para-aramid fibers (PPTA), which are known as high-performance organic fibers, have high strength and can provide the required carcass strength, but they have poor bending fatigue resistance and are difficult to resist when the tire is repeatedly deformed. It is difficult to use it as a carcass cord, as it causes breakage and damage to the carcass cord.

Therefore, the present inventor further investigated the characteristics of various organic fiber cords. As a result, as a tire cord, a new wholly aromatic polyester fiber cord has approximately the same tensile strength, tensile modulus, and elongation at break as the wholly aromatic polyamide fiber cord, and maintains satisfactory carcass strength. It was found that the tire structure has excellent flexural resistance and bending fatigue resistance and improves carcass durability, and it has been found that it is possible to achieve the above tire structure.

At the same time, it has been found that the wholly aromatic polyester fiber cord itself has superior vibration damping properties and shock absorbing properties compared to other tire cord materials, and the wholly aromatic polyester fiber cord has at least It has been found that by simply using it as a carcass cord, it is possible to effectively absorb and reduce the impact from the road surface, and that it is possible to improve riding comfort and wandering performance.

That is, the present invention is based on the use of a new wholly aromatic polyester fiber as a tire cord at least as a carcass cord. The aim is to provide radial tires that can improve performance.

[Means to solve the problem]

In order to achieve the above object, the radial tire of the present invention has the following features:
A carcass consisting of one or more carcass plies using a carcass cord that passes from the tread part through the sidewall part and is locked at both ends by folding back around the bead core of the bead part, and a carcass cord arranged radially outside the carcass and inside the tread part. The carcass cord includes a belt layer consisting of two or more belt plies using a belt cord, and the carcass cord uses a wholly aromatic polyester fiber cord.

The carcass is preferably formed of two carcass plies with the carcass cord at an angle of 65° or more and 88° or less with respect to the tire equator and tilted in the opposite direction with respect to the tire equator. A steel cord or a wholly aromatic polyester fiber is used as the belt layer, and the belt cord is attached to the belt layer at an angle of 40° to the tire equator.
It is preferable to include at least one belt ply arranged at an angle greater than or equal to 700 degrees.

[Effect]

The radial tire constructed in this manner uses a wholly aromatic polyester fiber cord at least as the carcass cord.

Fully aromatic polyester fibers are rigid, high-performance organic fibers that have a molecular structure shown in formula (1), for example, by ester bonding (-0-Co-) an aromatic compound having a benzene ring and a ring in which multiple benzene rings are condensed. It is a fiber known as a so-called polyarylate fiber.

As shown in Table 1, this material has high tensile strength, tensile modulus, and low elongation at break that are almost the same as fully aromatic polyamide fibers, so-called para-aramid fibers (PPAT), which are known as other high-performance organic fibers. Therefore, sufficient carcass strength can be maintained without increasing the number of carcass plies. In addition, this product has bending fatigue resistance, that is, it has been tested for 1500 bending tests at a bending angle of 130 degrees and a number of bends of 10,000 times.
As shown in Table 2, the strength retention rate for short fibers of d/1.80t/m is 51% for wholly aromatic polyamide fibers.
%, whereas that for fully aromatic polyester fibers is extremely high at 97%. Therefore, it is possible to prevent damage to the carcass cord from breaking during repeated deformation of the tire, thereby increasing the durability of the carcass and extending its service life.

Moreover, as shown in Figures 3 and 4, fully aromatic polyester fibers have superior vibration damping and shock absorbing properties compared to other tire cord materials, absorbing and mitigating shocks from the road surface and improving riding comfort. and wandering properties.

In addition, by using such a new wholly aromatic polyester fiber cord, the carcass cord can be positioned at an angle of 65 to 88 degrees to the tire equator without increasing tire weight or decreasing durability. On the other hand, it is possible to adopt a carcass structure consisting of two carcass plies tilted in the opposite direction, and while increasing the tire lateral rigidity, it is possible to burden the carcass with a part of the hoop effect. Therefore, it is possible to increase the belt cord angle while maintaining running performance, and in this case, tread rigidity can be moderately reduced, camber torque can be increased, and riding comfort and wandering properties can be further improved. Note that even when a conventional belt cord angle is adopted, the longitudinal stiffness of the tire can be reduced and the camber thrust can be improved. [Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

In the figure, a radial tire 1 includes a pair of bead portions 3 through which a bead core 2 passes, a sidewall portion 4 that is continuous with each bead portion 3 and extends outward in the tire radial direction, and a tread portion 5 that connects the outer ends of the sidewall portions 4. I can do it.

In addition, between the bead portions 3 and 3, a toroidal main body portion 7A extending from the first hered portion 5 through the sidewall portion 4 to the bead portion 3 has a toroidal body portion 7A that is folded around the bead core 2 from the inside of the tire to the outside. A car with a folded part 7B formed thereon/
The J cloth is placed on the rack, and a belt layer 9 is wrapped around the outside of the carcass 7.

The carcass 7 has a carcass cord at an angle of 65° or more and 88° or less with respect to the tire equator, more preferably 7
An angle of 0° or more and 88° or less, more preferably 75°
It is formed from two inner and outer carcass plies 7a, 7) arranged at an angle of more than 86 degrees and less than 86 degrees, and the folded end of the inner carcass ply 7a connects the folded end of the outer carcass ply 7b. By covering and extending radially outward, stress concentrations acting on the ends are dispersed. Also carcass ply 7
a and 7b form a cross-ply structure in which each carcass cord intersects with each other by inclining oppositely to the tire equator. Therefore, the carcass 7 can improve the tire lateral stiffness compared to conventional radial tires, and by increasing the camber thrust, it can prevent the tire from flowing sideways when driving on a slope, for example. The load can be placed on the carcass 7, and the hoop tightening function of the belt layer 9 can be reduced. This makes it possible to increase the belt cord angle while maintaining the overall hoop effect, moderately reducing tread rigidity without reducing running performance,
Can increase camber torque.

In the present invention, a wholly aromatic polyester fiber cord is employed as the carcass cord.

The wholly aromatic polyester fiber is a rigid, high-performance organic fiber having a molecular structure shown in formula (1), which is obtained by ester-condensing an aromatic compound having a benzene ring and a ring in which a plurality of benzene rings are condensed as described above. It is a new fiber material for tire cord, known as so-called polyarylate fiber.

As shown in Table 1, this fiber has approximately the same tensile strength, tensile modulus, and elongation at break as the wholly aromatic polyamide fiber, and can maintain the required sufficient carcass strength.

Furthermore, since it has high bending fatigue resistance, it can prevent cord breakage due to repeated deformation of the tire, and can exhibit sufficient durability for use. Moreover, as shown in Figures 3 and 4 above, this product has extremely high vibration damping and shock absorption properties, so it can effectively absorb and alleviate the shock received from the road surface, improving riding comfort. At the same time, it is possible to improve the ability to pass over bumps on the road surface, and to greatly improve wandering performance.

The belt layer 9 also includes first, second, and third belt plies 11 arranged in order from the carcass 7 toward the tread surface S.
．． In this example, consisting of 12.13, it has a three-layer structure. Also second
The belt ply 12 is formed to have a ply width in the axial direction of the tire compared to each of the other belt plies 11.13, and has a width BW of the belt layer 9, that is, the second By setting the brie width of the belt ply 12 to 0.80 times or more and 0.99 times or less of the tread width TW, the belt layer 9 reinforces the tread portion 5 with a hoop effect over almost the entire tread portion 11. do.

In addition to steel cords, wholly aromatic polyester fiber cords can be suitably used as belt cords.In particular, when wholly aromatic polyester fiber cords are used, their excellent vibration damping and shock absorbing properties improve riding comfort and ease of use. Ring performance can be further improved.

The first belt ply 11 arranges the belt cords at an angle of 40' or more and 70 degrees or less, more preferably 40 to 60 degrees, with respect to the tire equator, while the second
The third belt plies 12, 13 are arranged at an angle of 10 degrees or more and 30 degrees or less, for example, about 19 degrees, and in a direction in which the plies intersect with each other, similar to conventional tires. Therefore, the belt layer 9 reduces the rigidity of the first belt ply 11 by inclining it at a relatively deep angle, thereby reducing the in-plane rigidity of the tread. As a result, when the vehicle runs on a slope, the tread surface S is caused to follow the slope, and a camber torque is generated due to the tire outer diameter difference at a portion of each shoulder that occurs at that time.

As for the belt layer 9, the cord angle of the first belt ply may be set to 10 or more and 30 degrees or less like the other plies, or the belt layer may be formed using two belt plies. .

In addition, in the radial tire 1 of this embodiment, the fully aromatic polyester fiber cord used as the carcass cord itself has excellent vibration damping and shock absorbing properties, and has an impact mitigation and absorption effect from the road surface. The effect of improving camber thrust due to the increase in tire lateral rigidity by intersecting the carcass cords, and the l-
Wandering performance and riding comfort are greatly improved due to the reduction in L-rad in-plane rigidity and the resulting improvement in camber torque.

However, in the present invention, the wandering properties and the like can be improved simply by using a wholly aromatic polyester fiber cord as at least the carcass cord, an example of which is shown in FIG. 2 below.

In FIG. 2, the carcass 7 is formed from one carcass ply 7a in which carcass cords made of wholly aromatic polyester fiber cords are arranged at approximately 90 degrees to the tire equator, and on the outside in the radial direction, steel cords or A belt layer 9 consisting of two or more belt cords made of wholly aromatic polyester fiber cords, in this example first, second, and third belt plies 21, 22, and 23, is wound. Note that in this example, the first belt ply 21 is
The belt cord should be at least 40 degrees and 70 degrees from the tire equator.
'The second and third belt plies 22 and 23 are arranged at the following angles and the belt cords are arranged at 10 degrees with respect to the tire equator.
The belt cords are arranged at an angle of ~30° and are oriented in different directions so that each belt cord intersects between the plies.

〔Concrete example〕

We prototyped tires with tire sizes 10.0OR20, 1, and 4PR based on the tire structure shown in Figure 2 and specifications shown in Table 3, and tested the ride comfort and wandering properties of the prototype tires by driving on actual vehicles. In addition to evaluating the feeling, we measured the strength retention rate of each cord after running.

The driving conditions are the above tires on a 2.2D car with an internal pressure of 9.0.
It was installed under ~9.5 KSC and was run at a running speed of 80 to 100 km/h in an empty state until the wear life was completed. As shown in the table, by using fully aromatic polyester fiber cord as the carcass cord, it is possible to improve ride comfort and wandering performance compared to conventional tires, and even after driving, the carcass cord has almost the same level of stability as steel cord. You can see that the cord can hold its strength and maintain its durability. In addition, tires of the same size and structure as shown in FIG. 1 were prototyped based on the specifications shown in Table 4, and the ride comfort and wandering properties of the tires were compared through similar actual vehicle running tests.

As shown in the same table, by forming the carcass with two carcass plies using fully aromatic polyester fiber cords and making the carcass cords at least 65° and no more than 88°, the longitudinal stiffness of the tire can be relaxed and the camber can be reduced. - The thrust can be improved and the performance can be further improved. Furthermore, by setting the cord angle of at least one belt ply of the belt layer to 40° or more and 70' or less, preferably about 500, it is possible to reduce the in-plane rigidity of the tread and improve the camber torque.

〔Effect of the invention〕

In the radial tire of the present invention, as at least the carcass cord is made of a wholly aromatic polyester fiber cord, wandering performance and riding comfort can be improved. In addition, by using fully aromatic polyester fiber cords, the carcass cord angle was reduced.
It is now possible to adopt a cross-ply structure of layers, and the cord angle of at least one belt ply is 40 ~
When it is set to 700, the camber thrust and camber torque can be increased, and the tire longitudinal rigidity and tread in-plane rigidity can be relaxed, and the above-mentioned performance can be further improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, FIG. 2 is a sectional view showing another embodiment of the present invention, FIG. 3 is a diagram showing the vibration damping properties of wholly aromatic polyester fibers, and FIG. FIG. 4 is a diagram showing the impact absorption properties of wholly aromatic polyester fibers, and FIG. 5 is a diagram illustrating the prior art. 2.--Bead core, 3.--Bead portion, 4
,...-, side wall section, 5,,-,-,
Tread portion, 7-... Carcass, 7a, 7b-
...-Carcass ply, 9-...Belt layer, 11.12.13.21.22.23...Belt ply.

Claims (1)

[Scope of Claims] 1. A carcass consisting of one or more carcass plies using a carcass cord that passes from the tread portion through the sidewall portion and is locked at both ends by being folded back around the bead core of the bead portion, and the radial direction of the carcass A radial tire comprising a belt layer consisting of two or more belt plies using belt cords arranged on the outside and inside the tread part, and the carcass cords are made of wholly aromatic polyester fiber cords. 2. The carcass is comprised of two carcass plies in which the carcass cord is tilted at an angle of 65 degrees or more and 88 degrees or less with respect to the tire equator and opposite to the tire equator. radial tires. 3. Claim 1, wherein the belt layer includes at least one belt ply in which belt cords are arranged at an angle of 40 degrees or more and 70 degrees or less with respect to the tire equator.
and the radial tire according to 2.