JP2003320821A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve maneuvering stability, while securing excellent riding comfortableness. <P>SOLUTION: In an inner bead part 4i to be the inside of a vehicle in a mounting state, bead apex rubber 8i is made hard rubber having a height La1 of 20 to 60 mm and rubber hardness Ha1 of 70 to 90°. In an outer bead part 4o to be the outside of the vehicle, rubber hardness Ha2 of bead apex rubber 8o is made smaller than the rubber hardness Hal and the height La2 is made shorter than the La1. A bead reinforcing layer 10 of a reinforcing cord is provided at the outside of a tire shaft direction of the bead apex rubber 8o. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire in which steering stability is improved while ensuring excellent riding comfort by making the structures of the left and right bead portions different.

[0002]

2. Description of the Related Art In recent years, with the increase in output and performance of automobiles, it has been strongly desired that tires have high riding comfort as well as steering stability.

[0003] In pneumatic tires, it has been conventionally known that the lateral stability of the tire can be increased to improve the steering stability. Therefore, as shown schematically in Fig. 5 (A), the bead apex rubber a is used. Increasing the height h from the bead base line, increasing the rubber hardness of the bead apex rubber a, and / or forming a cord reinforcing layer b using a steel cord, an organic fiber cord or the like from the bead portion to the sidewall portion. Etc. are generally performed.

However, by such means as increasing the hardness and length of the bead apex rubber a and using the cord reinforcing layer b, the steering stability is improved but the tire longitudinal rigidity is increased, so that the riding comfort is increased. There is a problem of causing deterioration of sex.

Therefore, the present inventor has conducted research to enhance both the riding comfort and the steering stability. As a result, when the vehicle turns, a strong lateral force F acts on the tire outside the turning radius, and the tire is largely deformed.
As shown in FIG. 5B, it was found that a compressive stress acts on the inner bead portion c1 on the inner side of the vehicle and a tensile stress acts on the outer bead portion c2 on the outer side of the vehicle. Then, the bead portion c1 in the inside is reinforced with a hard rubber material having an excellent compression modulus, and the outer bead portion c1 is reinforced with a cord reinforcing layer having an excellent tensile modulus, so that an increase in tire longitudinal rigidity is minimized. It has been clarified that the lateral rigidity required during turning can be most effectively increased while suppressing to, and the steering stability can be greatly improved while ensuring excellent riding comfort.

That is, according to the present invention, the bead portion on the inside of the vehicle is reinforced in the compression direction by increasing the rubber hardness and height of the bead apex rubber or the clinch apex rubber, and the bead portion on the outside of the vehicle is reinforced by the reinforcing cord. Based on providing a bead reinforcing layer and reinforcing in the pulling direction,
While suppressing the increase in tire vertical rigidity to the minimum, the lateral rigidity required during turning can be most effectively increased, and a pneumatic tire that can greatly improve driving stability while ensuring excellent riding comfort It is intended to be provided.

[0007]

In order to achieve the above object, the invention of claim 1 is folded back around the bead core to the ply body portion from the tread portion to the side wall portion to the bead core of the bead portion. A pneumatic tire comprising a carcass having a carcass ply provided with a series of ply folded portions, and a bead apex rubber extending from the bead core to the tire radial direction between the ply body portion and the ply folded portion, When the tire is mounted on a vehicle, the bead apex rubber has a radial height La1 from the bead base line of 20 to 60 mm and a rubber hardness Ha1 in the inner bead portion of the vehicle.
(Durometer A hardness) is a hard rubber of 70 to 95 °, and at the outer bead portion on the outside of the vehicle, the rubber hardness Ha2 of the bead apex rubber is smaller than the rubber hardness Ha1 and from the bead baseline. The radial height La2 of the bead apex rubber is smaller than the radial height La1 and a bead reinforcing layer using a reinforcing cord extending radially inward and outward on the tire axially outer side of the bead apex rubber is provided. It has a feature.

According to the second aspect of the present invention, when the tire is mounted on a vehicle, the bead apex rubber is provided in the inner bead portion of the vehicle at a radial height La1 from the bead baseline of 10 to 24 mm, and Rubber hardness H
a1 is 70 to 95 ° hard rubber, and the rubber hardness Hb1 is 7 outside the ply folded-back portion in the tire axial direction.
The radial height Lb1 from the bead base line is 0 to 95 °, and the radial height Lb1 is 25 to 60 mm.
While the clinch apex rubber having a larger size is arranged, the rubber hardness Ha2 of the bead apex rubber is less than or equal to the rubber hardness Ha1 at the outer bead portion outside the vehicle, and the radial direction of the bead apex rubber from the bead baseline is set. The height La2 is equal to or less than the radial height La1, and the rubber hardness Hb2 is smaller than the rubber hardness Hb1 outside the ply folded-back portion in the tire axial direction, and the radial height Lb2 from the bead base line is the radius. It is characterized in that a clinch apex rubber having a height smaller than the direction height Lb1 is arranged, and a bead reinforcing layer using a reinforcing cord extending inward and outward in the radial direction outside the bead apex rubber is provided.

In the bead reinforcing layer, the reinforcing cords are arranged at an angle of 45 to 90 ° with respect to the tire circumferential direction, the width in the radial direction is set to 15 to 70 mm, and the inner end in the radial direction is on the side of the bead apex rubber. It is preferable to position it on one side.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below.
This will be described together with the illustrated example. 1 is a meridional sectional view showing a pneumatic tire of a first invention according to claim 1 of the present application, and FIG. 4 is a meridional sectional view showing a pneumatic tire of a second invention according to claim 2.

In FIG. 1, a pneumatic tire 1A of the first invention comprises a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, an inner portion of the tread portion 2 and the carcass. 6 and a belt layer 7 disposed on the outer side. In addition, a bead apex rubber 8 is provided in each bead portion 4 so as to stand outward from the bead core 5 in the radial direction of the tire.

The belt layer 7 has two or more, in this example, two belt plies 7A, 7 in which high elastic belt cords are arranged at an angle of, for example, 10 to 35 ° with respect to the tire circumferential direction.
It consists of B. The belt plies 7A and 7B are overlapped with each other so that the belt cords intersect each other with different inclination directions, thereby increasing the belt rigidity and making the tread portion 2 have a hoop effect. It is strongly reinforced. As the belt cord, a steel cord or a high modulus organic fiber cord comparable to the steel cord, such as an aromatic polyamide fiber, is preferably used.

In this example, the band layer 9 is provided outside the belt layer 7 for the purpose of enhancing the restraining force on the belt layer 7 and improving the high-speed durability.
The band layer 9 has a band cord spirally wound at an angle of, for example, 5 ° or less with respect to the tire circumferential direction, and extends at least to cover the outer end portion of the belt layer 7 in the tire axial direction.

The carcass 6 is formed by one or more carcass plies 6A in which carcass cords are arranged at an angle of 75 to 90 ° with respect to the tire circumferential direction, and in this example, one carcass ply 6A. The carcass ply 6A has the bead cores 5, 5
The bead core 5 is provided on both sides of the ply body 6a extending over the space.
A series of ply turn-back portions 6b that are turned around from inside to outside are provided. As the carcass cord, an organic fiber cord such as nylon, rayon or polyester is suitable, but a steel cord or the like may be appropriately used according to demand.

Next, the bead apex rubber 8 is
The ply body 6 of the carcass 6 has a triangular cross section.
It extends outward in the radial direction of the tire passing between a and the ply folded-back portion 6b.

In the first aspect of the present invention, when the tire is mounted on the vehicle, the bead apex rubber 8i is attached to the rubber hardness Ha1 (durometer A hardness) of the inner bead portion 4i as shown in FIGS. Is 70
The bead apex rubber 8i has a height La1 in the radial direction from the bead base line BL increased to a range of 20 to 60 mm, while being formed of hard rubber of ˜95 °.

The "bead baseline BL" means a tire axial direction line passing through a bead diameter position defined by a standard on which the tire is based.

On the other hand, in the outer bead portion 4o on the outer side of the vehicle, the rubber hardness Ha2 of the bead apex rubber 8o is changed to the rubber hardness H as shown in FIGS.
and the height L of the bead apex rubber 8o from the bead base line BL in the radial direction.
a2 is set to be smaller than the radial height La1. Moreover, the bead reinforcing layer 10 extending inward and outward in the radial direction is provided on the outer side in the tire axial direction of the bead apex rubber 8o.
Is formed.

In this example, the bead reinforcing layer 10 is provided along the outer surface of the ply folded-back portion 6b. However, the bead apex rubber 8o is formed along the outer surface of the bead apex rubber 8o. It is also possible to arrange it through between the 8o and the ply folded-back portion 6b.

The bead reinforcing layer 10 has one or more reinforcing cords arranged at an angle of 45 to 90 ° with respect to the tire circumferential direction and has a radial width K of 15 to 70 mm, one in this example. Formed of cord plies. The reinforcing cords include inorganic cords including steel cords, aromatic polyamide, PEN (polyethylene 2,
6 naphthalate), nylon, or an organic fiber cord containing a polyester cord can be adopted, but an organic fiber cord having a low bending rigidity can be preferably used from the viewpoint of riding comfort.

Further, in the present embodiment, the bead reinforcing layer 10 has its inner end e1 in the radial direction located laterally of the bead apex rubber, and extends radially outward from the inner end e1 beyond the bead apex rubber 8o. Has been extended to.

As described above, in the bead portion 4i in which the compressive stress strongly acts at the time of turning, the rubber hardness Ha1 and the height La1 of the bead apex rubber 8i are increased to the above range to strengthen the reinforcement in the compression direction. ing.

On the other hand, in the outer bead portion 4o where the tensile stress acts strongly during turning, the bead reinforcing layer 10 is provided to strengthen the reinforcement in the pulling direction.
The rubber hardness Ha2 and the height La2 of the bead apex rubber 8o are made smaller than the rubber hardness Ha1 and the height La1 to keep the compression rigidity and the bending rigidity low.

As a result, the lateral rigidity required during turning can be effectively increased while the increase in tire vertical rigidity is suppressed to a minimum, and the steering stability is greatly improved while ensuring excellent riding comfort. It becomes possible.

Here, the rubber hardness Ha1 of the bead apex rubber 8i inside the vehicle is less than 70 °, and the height L is
When a1 is less than 20 mm, reinforcement in the compression direction is insufficient, and therefore it is preferable that the rubber hardness Ha1 is 80 ° or more and the height La1 is 30 mm or more. However, when the rubber hardness Ha1 exceeds 95 ° and the height La1 exceeds 60 mm, not only the reinforcement effect in the compression direction is not expected to increase, but also the tire longitudinal rigidity becomes excessive. As a result, the ride comfort is unnecessarily reduced.

On the other hand, when the angle of the reinforcing cord of the bead reinforcing layer 10 is less than 45 ° and the width K is less than 15 mm, the reinforcement in the pulling direction is insufficient, and therefore the angle is 60 ° or more and the width is less than 60 °. More preferably, K is 30 mm or more. However, even if the width K exceeds 70 mm, the vertical rigidity of the tire does not increase so much, so the upper limit of the width K is set.

Further, the bead apex rubbers 8i, 8o
In the above, it is preferable to provide the rubber hardness difference Ha1−Ha2 of 5 ° or more and / or the height difference La1−La2 of 20 mm or more in order to further exert the effect of the present application.

Here, the inner bead portion 4i and the outer bead portion 4o are bead apex rubbers 8i, 8 in this example.
Other than the difference in the rubber hardness and height of o, and the presence or absence of the bead reinforcing layer 10, they are formed in the same configuration. However, depending on requirements, for example, the folding height of the ply folding portion 6b and the rubber hardness and height of the clinch apex rubber 11 can be made different.

Next, the pneumatic tire 1B of the second invention of the present application is illustrated in FIG. In FIG. 4, the pneumatic tire 1B has a bead apex rubber 8i having a height La1 of 10 to 24 mm and a rubber hardness Ha1 of 70 to 95 ° in the inner bead portion 4i, and the ply folded portion. Clinch apex rubber 11i having a rubber hardness Hb1 of 70 to 95 °, a radial height Lb1 from the bead base line BL of 25 to 60 mm, and a radius hardness greater than the radial height La1 is arranged on the outer side of the tire 6b in the axial direction. is doing.

On the other hand, in the outer bead portion 4o, the rubber hardness Ha2 of the bead apex rubber 8o is less than or equal to the rubber hardness Ha1 and the radial height La2 of the bead apex rubber 8o is less than or equal to the radial direction La1. In addition, a clinch having a rubber hardness Hb2 smaller than the rubber hardness Hb1 and a radial height Lb2 from the bead base line BL smaller than the radial height Lb1 on the tire axially outer side of the ply folded-back portion 6b. The apex rubber 11o is arranged.

Moreover, the bead apex rubber 8o
A bead reinforcing layer 10 similar to that of the first invention is provided on the outer side in the tire axial direction.

The clinch apex rubber 11
Reference numerals i and 11o denote rim displacement preventing rubber members, and in this example, they rise from the bead heel portion 4h along the rim flange and are joined to the sidewall rubber 3G at the radial outer edge line Q thereof.

As described above, in the second invention, at least the rubber hardness Hb1 and the height Lb1 of the clinch apex rubber 11i on the vehicle inner side are compared with the rubber hardness Hb2 and the height Lb2 of the clinch apex rubber 11o on the vehicle outer side. The bead portion 4i is raised and reinforced in the compression direction.

Therefore, as in the second aspect of the invention, the lateral rigidity required during turning can be effectively increased while the increase in tire longitudinal rigidity is suppressed to a minimum, and steering stability is ensured while ensuring excellent riding comfort. It is possible to significantly improve the property.

Here, the rubber hardness Ha1 of the bead apex rubber 8i inside the vehicle is less than 70 °, and the height L is L.
a1 is less than 10 mm, and the clinch apex rubber 11i has a rubber hardness Hb1 of less than 70 ° and a height Lb1.
Is less than 25 mm, reinforcement in the compression direction is insufficient. Therefore, in order to reinforce in the compression direction, the rubber hardnesses Ha1 and Hb1 are 80 ° or more, and the height La1 is 15 °.
It is preferable that mm or more and the height Lb1 be 25 mm or more. However, the rubber hardnesses Ha1 and Hb1 are 95 °.
When the height Lb1 exceeds 60, or when the height Lb1 exceeds 60, the tire longitudinal rigidity excessively increases, resulting in an unnecessary decrease in riding comfort.

On the other hand, in the bead reinforcing layer 10, the angle of the reinforcing cord is set in the range of 45 to 90 °, and further in the range of 60 to 90 ° in order to reinforce in the pulling direction, as in the first invention. Is preferable, and the width K is 15 to 70 mm.
The range is more preferably 30 to 70 mm.

The clinch apex rubber 11i,
In 11o, the rubber hardness difference Hb1-Hb2 is 5 ° or more, and / or the height difference Lb1-Lb2 is 10 m.
It is preferable to provide m or more in order to exert the effect of the present application more effectively.

Although a particularly preferred embodiment of the present invention has been described above in detail, the present invention is not limited to the illustrated embodiment and can be modified into various modes.

[0039]

EXAMPLE A passenger car tire having a tire size of 185 / 70R14 was prototyped according to the specifications shown in Table 1, and the steering stability and riding comfort of each sample tire were tested. The results are shown in Table 1.

(1) Steering stability: A test tire was mounted on four wheels of a passenger car (2000 cc) with a rim (5.5 J × 14) and an internal pressure (220 kPa), and was run on a dry asphalt test course. Steering wheel responsiveness, rigidity,
The characteristics relating to the grip and the like are indicated by an index with Comparative Example 1 being 100 by sensory evaluation of the driver. The larger the index, the better.

(2) Riding comfort: In the test run, the riding comfort was evaluated by sensory evaluation of the driver in Comparative Example 1.
Is shown as an index. The larger the index, the better.

[0042]

[Table 1]

[0043]

As described above, according to the present invention, the bead portion on the inside of the vehicle is reinforced in the compression direction by increasing the rubber hardness and height of the bead apex rubber and / or the clinch apex rubber, and is on the outside of the vehicle. Since the bead reinforcing layer of the reinforcing cord is provided to reinforce the bead portion in the pulling direction, it is possible to most effectively increase the lateral rigidity required during turning while suppressing the increase in tire vertical rigidity to the minimum. It is possible to greatly improve driving stability while ensuring excellent riding comfort.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a pneumatic tire of the first invention.

FIG. 2 is a partial sectional view showing an enlarged inner bead portion.

FIG. 3 is a partial sectional view showing an outer bead portion in an enlarged manner.

FIG. 4 is a cross-sectional view showing an embodiment of a pneumatic tire of the second invention.

5A and 5B are diagrams for explaining a conventional technique.

[Explanation of symbols]

2 tread section 3 Side wall part 4, 4i, 4o bead part 5 bead core 6 carcass 6A carcass ply 6a ply body 6b Ply turn-up part 8,8i, 8o Bead apex rubber 10 Bead reinforcement layer 11, 11i, 11o Clinch apex rubber BL bead baseline

Claims (3)

[Claims] 1. A carcass having a carcass ply in which a ply turn-back part that is turned around the bead core is provided in series in the ply body part from the tread part to the bead core of the bead part, and the ply body part. A pneumatic tire comprising a bead apex rubber extending from the bead core to the tire radial direction outward between the ply turn-up part and the ply turn-up part, wherein the bead apex at the inner bead part inside the vehicle when the tire is mounted on the vehicle. Radial height La1 from the bead base line is 20 to 60 m
m, and the rubber hardness Ha1 (durometer A hardness) is 70
The hardness of the bead apex rubber is smaller than that of the bead apex rubber at the outer bead portion on the outer side of the vehicle, and the height in the radial direction of the bead apex rubber from the bead baseline is high. A pneumatic tire characterized in that a length La2 is smaller than the radial height La1 and a bead reinforcing layer using a reinforcing cord extending inward and outward in the radial direction is provided outside the bead apex rubber in the tire axial direction. 2. A carcass having a carcass ply in which a ply turn-back portion that turns back around the bead core is provided in series in the ply body portion that extends from the tread portion to the bead core of the bead portion, and the ply body portion. A pneumatic tire comprising a bead apex rubber extending from the bead core to the tire radial direction outward between the ply turn-up part and the ply turn-up part, wherein the bead apex at the inner bead part inside the vehicle when the tire is mounted on the vehicle. Radial height La1 from the bead base line is 10 to 24 m
m and a rubber hardness Ha1 of 70 to 95 °, and at the tire axial direction outer side of the ply turnback portion,
A clinch apex rubber having a rubber hardness Hb1 of 70 to 95 ° and a radial height Lb1 from the bead base line of 25 to 60 mm and larger than the radial height La1 is arranged while the outer bead outside the vehicle is placed. In the section, the rubber hardness Ha2 of the bead apex rubber is equal to or less than the rubber hardness Ha1.
In addition, the radial height La2 of the bead apex rubber from the bead baseline is set to be equal to or less than the radial height La1, and the rubber hardness Hb2 is smaller than the rubber hardness Hb1 on the tire axial direction outer side of the ply turnback portion, and the bead. A clinch apex rubber having a radial height Lb2 from the baseline smaller than the radial height Lb1 is arranged, and bead reinforcement using a reinforcement cord extending radially inward and outward on the tire axially outer side of the bead apex rubber. A pneumatic tire having a layer. 3. The bead reinforcing layer is such that the reinforcing cords form an angle of 45 to 90 ° with respect to the tire circumferential direction, the radial width is 15 to 70 mm, and the radial inner end is on the side of the bead apex rubber. The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire is located on one side.