JP2002059715A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire improved in stability and controllability by increasing rigidity of a side wall part of a tire without spoiling rolling resistance and durable longevity and without complicating a manufacturing method. SOLUTION: A circumferential direction cord reinforcing layer 8 formed in specified width in the diametrical direction by spirally winding one to a plural number of inextensional fiber cords in the tire circumferential direction around a belt type body buried in covered rubber is arranged at least at one point of a region toward the outside in the diametrical direction of the bead part from the inside in the diametrical direction of an end part in the axial direction of the belt layer on the pneumatic radial tire furnished with a carcass layer, a side wall part, the belt layer, the tread part, an inner liner, a bead filler, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having improved steering stability by increasing side rigidity without impairing rolling resistance and durability life.

[0002]

2. Description of the Related Art Durable life, wear resistance, braking performance, steering stability, ride comfort,
A wide variety of performances such as in-vehicle noise and fuel efficiency have been demanded, and in recent years there has been an increasing demand for higher multiplex compatibility. Above all, there is an increasing demand for improving the steering stability without impairing the various performances of the tire, and various ideas have been proposed so far.

[0003] In a tire side portion having only carcass cords and thin sidewall rubbers arranged in the radial direction as main components, the bending rigidity particularly in the side wall surface is small, and is therefore affected by the side rigidity of the tire. It has been difficult to improve the steering stability of a tire without sacrificing other tire performances such as rolling resistance and durability life.

Here, in order to directly increase the rigidity of the tire side portion, there has been proposed a measure of adhering a fiber reinforcing member having a conventional twisted cord weaving structure adjacent to the carcass layer of the side portion. In such a case, the fiber reinforcing member cannot form and follow the large elongation deformation of the side portion in the vulcanization process, making it difficult to manufacture by the conventional manufacturing method, and the flexibility of the sidewall in the product tire is extremely high. Such measures have not been put to practical use because they are likely to be lost and the original characteristics of radial tires are likely to be lost.

Therefore, conventionally, as a countermeasure against the above-mentioned problem, a high elasticity and low heat shrinkage cord is used for a cord for a carcass ply to increase the rigidity of the tire side portion and to reduce the heat shrinkage during vulcanization. Many proposals have been made to stabilize the side shape. In recent years, various types of organic fiber reinforced belt layers have been combined with steel cord belt layers that are common in radial tires for passenger cars, and further, the physical properties of the rubber coating that reinforces these layers have been changed to improve steering stability. Attempts to improve have been proposed.

[0006]

The use of a cord having high elasticity and low heat shrinkage as a carcass cord as in the above-mentioned prior art requires a tensile force in the tire radial direction which coincides with the cord direction by increasing the cord modulus. Although the rigidity can be effectively increased, the in-plane bending rigidity and the circumferential rigidity of the tire perpendicular to the radial direction cannot be directly increased. Although the heat shrinkage deformation of the tire after vulcanization is certainly reduced by the cord, the internal pressure filling due to the variation in the number of cords inserted during production (the number of cords arranged per fixed width) and the variation in the thickness of the side members Unevenness on the tire side could not be suppressed, and in any case, a sufficient effect could not be obtained. Further, in the case of the conventional measures described above in which the steel cord belt layer is used in combination with an organic fiber reinforcing belt layer using an organic fiber cord such as nylon or polyester, or the physical properties of the rubber covering these belt reinforcing layers are changed. It is possible to improve the steering stability of the tire due to the frictional force in the ground contact surface of the surface part, but if an input that forcibly directly deforms the tire side during vehicle running such as slalom running is received Did not achieve the effect of improving steering stability.

Furthermore, in recent years, reduction in rolling resistance of tires has been demanded in order to reduce fuel consumption of vehicles, and the thickness of tire carcass layers has been increasingly reduced in order to reduce tire weight. It has become difficult to deal with conventional measures alone.

In view of the above circumstances, an object of the present invention is to reduce the rigidity of a tire sidewall without impairing rolling resistance, riding comfort, durability, and the inherent characteristics of a radial tire, and without complicating the manufacturing method. And to provide a pneumatic radial tire with improved tire handling stability.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive studies especially on the relationship between the rigidity of the sidewall portion of the tire and the steering stability of the tire, and have obtained the following findings. As a result, the present invention has been completed.

As a result of examining the relationship between the steering stability and the sidewall rigidity, it was found that not only the lateral spring coefficient but also the torsional spring coefficient in the tire rotation direction greatly affected the steering stability.

Therefore, if the torsional rigidity in the rotational direction can be increased while maintaining the vertical spring coefficient, it is possible to improve the steering stability while maintaining good ride comfort and rolling resistance, and one or more non-extendable ones are required. A belt-shaped body in which a conductive fiber cord is embedded in a covering rubber is spirally wound in the circumferential direction of the tire to form a circumferential cord reinforcing layer having a constant radial width. When it was arranged in a region from the inside in the direction to the outside in the radial direction of the bead portion, it was found that the above object could be achieved, and the present invention was completed.

The present invention is based on the above findings of the present inventors, and means for solving the above-mentioned problems are in the following inventions (1) to (8).

(1) A carcass layer composed of at least one radial carcass ply which is continuous in a toroidal shape between a pair of bead cores and whose both ends can wind up the bead core from the inside to the outside of the tire, and a side region of the carcass layer A side wall portion arranged on the outer side in the tire axial direction to form a side surface portion, a belt layer including at least two belt plies arranged on the outer side in the tire radial direction of the crown region of the carcass layer; A tread portion that is arranged outside the tire radial direction to form a ground contact portion; an inner liner that is arranged on the inner surface of the carcass layer of the tire to form a security film; and a carcass layer main body that extends from the one bead core to the other bead core. Bead filter disposed between a portion and a winding portion wound up by the bead core. In a pneumatic radial tire provided with one or more non-extensible fiber cords, a band in which one or more non-extensible fiber cords are embedded in a covering rubber is spirally wound in the tire circumferential direction to have a constant radial width. Wherein the circumferential cord reinforcing layer formed in the air is disposed in at least one portion of a region extending from a radially inner side of an axial end portion of the belt layer to a radially outer side of the bead portion. Included radial tire.

(2) The pneumatic radial tire according to the above (1), wherein the circumferential cord reinforcing layer is disposed adjacent to an inner side or an outer side of the carcass layer body in the axial direction.

(3) The pneumatic radial tire according to the above (1) or (2), wherein the circumferential cord reinforcing layer is disposed around a maximum width of a side region of the tire.

(4) The above (1) or (1) wherein the circumferential cord reinforcing layer is disposed in a region from a maximum width portion of a side region of the tire to a radial inside of an axial end of the belt layer. The pneumatic radial tire according to 2).

(5) The above (1) or (2), wherein the circumferential cord reinforcing layer is disposed in a region from a maximum width portion of a side region of the tire to a radial outside of the bead portion.
The pneumatic radial tire according to 1.

(6) The radial width (L) of the circumferential cord reinforcing layer is in the range of 7 to 40% of the section height (SH) in a cross section including the rotation axis of the tire. The pneumatic radial tire according to any one of (1) to (5).

(7) The radial width (L) of the circumferential cord reinforcing layer is in a range of 30 to 40% of a section height (SH) in a cross section including a rotation axis of the tire. )
The pneumatic radial tire according to any one of (1) to (5).

(8) The pneumatic radial tire according to any one of (1) to (7), wherein the non-extensible fibers of the circumferential cord reinforcing layer are polyamide, polyimide, or polyester fibers.

(9) The pneumatic radial tire according to any one of the above (1) to (8), wherein the cord driving density of the circumferential cord reinforcing layer is 3 to 20 per 10 mm width of the reinforcing layer. .

In the pneumatic radial tire according to the present invention, the circumferential cord reinforcing layer is provided at at least one position in a region from a radial inside of an axial end of the belt layer to a radial outside of a bead portion. ing. Therefore, since the carcass layer of the present tire is reinforced in the radial direction by the carcass cord and also reinforced in the circumferential direction of the tire by the circumferential cord reinforcing layer, the in-plane bending rigidity of the side portion is reduced. Dramatically higher, steering stability of the tire is improved. Moreover, since the out-of-plane bending stiffness is maintained flexibly, it is possible to favorably follow the large vertical deflection of the side portion due to the vertical load during running of the tire, thereby lowering the riding comfort and rolling resistance of the tire. There is no.

In the conventional method of extending the hard bead filler rubber to the upper part of the shoulder, or in the method of sticking a hard rubber sheet from the upper part of the bead filler rubber to the upper part of the shoulder, the ride comfort and rolling resistance of the tire decrease. However, by attaching the circumferential cord reinforcing layer as a side reinforcing member layer as described above, it is possible to solve such a problem that the riding comfort and the rolling resistance are reduced.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a pneumatic radial tire according to the present invention is shown in a half sectional view of a tire shown in FIGS. 1 and 2, and a belt-like shape in which a fiber cord of FIG. 3 is embedded in a covering rubber. This will be described in detail with reference to the figure of the body.

According to the present invention, a carcass layer 2 comprising at least one radial carcass ply, which is continuous in a toroidal shape across a pair of bead cores 1 and whose both ends can wind up the bead core from the inside to the outside of the tire, A side wall portion 3 disposed outside the side region in the tire axial direction to form a side surface portion, and a belt layer 4 including at least two belt plies disposed outside the crown region of the carcass layer in the tire radial direction. A tread portion 5 disposed outside the belt layer in the tire radial direction to form a ground contact portion; an inner liner 6 disposed on the tire inner surface of the carcass layer to form a security film; Disposed between the carcass layer main body portion extending to the bead core and the winding portion wound up by the bead core In a pneumatic radial tire provided with a bead filler 7, one or more non-extensible fiber cords are spirally wound around the belt-shaped body embedded in the covering rubber in the tire circumferential direction to have a constant width. A circumferential cord reinforcing layer (8 or 8 ') formed in a radial width is provided at at least one position in a region from a radial inside of an axial end portion of the belt layer to a radial outside of the bead portion. It is a pneumatic radial tire characterized by being performed.

The circumferential cord reinforcing layer of the present invention is a belt-shaped body in which one or a plurality of non-extensible fiber cords are embedded in a covering rubber as shown in FIG. 2. In the latter half of the molding step, the tire is spirally wound in the tire circumferential direction to form a fixed radial width on the side portion of the tire. The number of fiber cords buried in the covering rubber may be plural, but it is necessary that the fiber cords be in close contact with the curved surface of the side portion.

The circumferential cord reinforcing layer (8 or 8 ')
As shown in FIG. 1 or FIG. 2, the axial direction of the main body of the carcass layer is provided at least in one region from the radial inner side of the axial end portion of the belt layer to the radial outer side of the bead portion. Arranged adjacent to the inner side or outer side enhances the rigidity of the side portion and improves the steering stability of the tire without lowering the bending fatigue resistance and the riding comfort and rolling resistance of the side portion of the tire. Above is advantageous for implementation.

The same effect can be obtained by arranging the circumferential cord reinforcing layer anywhere in the region from the radial inner side of the axial end of the belt layer to the radial outer side of the bead portion. However, it is preferable that the bead filler 7 is disposed in a region where deformation of the coating rubber between the cords of the carcass ply during rolling of the tire is large, that is, in a region from the vicinity of 30% from the tip of the radial height of the bead filler 7 to the buttress area. This is effective to reinforce the rigidity of the side portion and improve the maneuverability of the tire.

The location of the circumferential cord reinforcing layer at the side of the tire where the bending deflection is greatest, that is, near the maximum width of the side of the tire is the center for increasing the side rigidity. More effective in improving performance.

When the circumferential cord reinforcing layer is disposed in a region from the maximum width portion of the side region of the tire to the radially inner side of the axial end of the belt layer, at the portion that is most deformed when rolling the tire. Therefore, the side rigidity is remarkably improved, and the rigidity can be improved with a minimum amount of reinforcing material.
It is effective for flat tires of series 0 or less to increase side rigidity and improve steering performance.

However, in the case of a tire of 60 series or more, the deformation at the time of rolling the tire becomes too large in the region from the maximum width portion of the side region to the radially inner side of the axial end of the belt layer, For tires of 60 series or more, it is better to dispose the circumferential cord reinforcing layer in a region extending from a maximum width portion of a side region to a radially outer side of the bead portion, because there is a possibility of causing a decrease in tire durability. This is advantageous for securing the durability life and increasing the side rigidity and improving the steering performance.

The radial width (L) of the circumferential cord reinforcing layer is preferably in the range of 7 to 40% of the section height (SH) in a cross section including the rotation axis of the tire, and 30 to 40%. More preferably, it is in the range of 40%. The width (L) of the circumferential cord reinforcement layer is determined by the section height (S
If H) is less than 7%, the effect of enhancing the side rigidity of the tire is too small to be small, and if it is more than 40%, the riding comfort and rolling resistance of the tire may be deteriorated.

Examples of the non-extensible fibers of the circumferential cord reinforcing layer include high-strength, high-strength, low-creep organic and metal or glass fibers commonly used for reinforcing tire carcass and belts. All can be used. Among them, polyamide fibers such as nylon 6, nylon 66, Kevlar,
Polyester fibers and polyimide fibers such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are lightweight, high-strength, high-rigidity, and have good adhesion to the covering rubber. It is suitably used for conductive fibers.

The cord density of the circumferential cord reinforcing layer is preferably 3 to 20 per 10 mm width of the reinforcing layer. The driving density of the cord is 10 mm
If the number is less than two per unit, the opening of rubber in the circumferential direction between the ply cords of the carcass layer cannot be suppressed, while if the number exceeds 20 per 10 mm of the reinforcing layer width, there is a concern that ride comfort and rolling resistance may decrease. is there.

In the above-mentioned compounding, if the adhesiveness with the rubber after vulcanization is sufficient, the fiber may not be subjected to an adhesive treatment in advance, but if the adhesion is insufficient, the fiber cord for the tire and the rubber may be used. The filament fibers may be subjected to a dipping and heat-setting treatment in the same manner as in the case of increasing the adhesive strength with the filament fibers.

[0036]

EXAMPLES Next, in order to further clarify the effects of the present invention, specific description will be made based on examples and comparative examples.

In Examples 1 to 5, two 1 × 2 twisted cords of 1500 denier polyester fiber shown in the upper row of Table 1 were used as the circumferential cord reinforcing layer.
A belt-shaped body embedded in the covering rubber is spirally wound in the tire circumferential direction, and a circumferential cord reinforcing layer formed to have a constant radial width is adjacent to an outer side in the axial direction of a maximum width portion of the belt layer. Arranged and pointed. The arrangement of each circumferential direction cord reinforcing layer, the number of driving layers, the radial width, and the L / SH are shown in the middle row of the table. Comparative Example 1 is a conventional example having no circumferential cord reinforcing layer, and Comparative Example 2 uses a steel wire.

As shown in FIG. 1, the circumferential cord reinforcing layer is disposed adjacent to the outside of the carcass layer around the maximum width of the tire in the side region of the carcass of the pneumatic radial tire of size 215 / 60R16. . The carcass layer used was a single-layer carcass layer composed of a polyethylene terephthalate (PET) cord having a double twist of 1500 denier. Comparative Example 2 has a wire inserted as a circumferential cord reinforcing layer,
As Comparative Example 1, a conventional pneumatic radial tire not using the fiber reinforcing member layer was also manufactured.

With respect to the pneumatic radial tire manufactured under the above conditions, a test of steering stability and rolling resistance was performed as follows.

<Steering stability> The test tires were assembled on a standard rim (6.5 J × 16), mounted on a test vehicle (Toyota Mark II), and traveled straight and changed lanes at a speed of 40 to 120 km / h. Car driving under the conditions of
Driving stability was evaluated by the feeling (feeling) of the test driver. The evaluation was scored on a scale of 10 points as a perfect score, and the score was expressed as an index with Comparative Example 1 being 100. The higher the index, the better the steering stability.

<Rolling Resistance> The rolling resistance was measured using SA.
According to EJ1269, internal pressure 200KPa, load 4
Measured at 50 kgf and 80 km / h, and
It was indicated by an index as 00. The higher the index, the higher the rolling resistance.

<Drum Durability> In a room adjusted to 25 ° C. ± 2 ° C., the test tire was adjusted to the maximum air pressure according to the JIS standard, left for 24 hours, and the air pressure was readjusted.
The tire was loaded with 1.5 times the maximum load capacity in the applied size prilating in the ATMA YEAR BOOK (2000 edition) and was run at a speed of 60 km / h on a drum having a diameter of about 1.7 m. 10,000k without breakdown
m was completed.

The results obtained are also shown in the lower part of Table 1.

[0044]

[Table 1]

In this way, one or a plurality of non-extensible fiber cords are helically wound in the circumferential direction of the tire in a circumferential direction formed by wrapping the belt-shaped body embedded in the covering rubber. The pneumatic radial tire of the present invention, wherein the cord reinforcing layer is disposed in a region from a radially inner side of the axial end portion of the belt layer to a radially outer side of the bead portion,
It was found that the steering stability was improved without lowering the rolling resistance. In Example 4, in which the width of the circumferential direction cord reinforcing layer was large, the steering stability was remarkably improved, but the rolling resistance was slightly reduced.

[0046]

As described above, in the pneumatic radial tire of the present invention, one or a plurality of non-extensible fiber cords are spirally wound in the circumferential direction of the tire in which the band-shaped body is embedded in the covering rubber. The circumferential cord reinforcing layer formed to have a constant radial width by being wound is disposed at at least one position in a region from the radial inside of the axial end of the belt layer to the radial outside of the bead portion. Thereby, the rigidity of the sidewall portion of the tire is increased and the steering stability is improved without impairing the rolling resistance, the durability life, and the inherent characteristics of the radial tire, and without complicating the manufacturing method.

[Brief description of the drawings]

FIG. 1 is a half sectional view of a pneumatic radial tire according to one embodiment of the present invention.

FIG. 2 is a half sectional view of a pneumatic tire according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view of a belt-like body in which a plurality of non-extensible fiber cords of the present invention are embedded in a covering rubber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead wire 2 Carcass layer 3 Side wall part 4 Belt layer 5 Tread part 6 Inner liner 7 Bead filler 8, 8 'Circumferential cord reinforcing layer SH Section height L Width of circumferential cord reinforcing layer Wmax Maximum width position of side part

Claims (9)

[Claims] 1. A carcass layer formed of at least one radial carcass ply, which is continuous in a toroidal shape over a pair of bead cores and has both ends rolled up from the inside to the outside of the tire, and a tire in a side region of the carcass layer A side wall portion that is disposed axially outward to form a side surface portion, a belt layer including at least two belt plies disposed radially outward of a crown region of the carcass layer in a tire region, A tread portion that is arranged on the tire radial outside to form a ground contact portion; an inner liner that is arranged on the tire inner surface of the carcass layer to form a security film; and a carcass layer main body portion that extends from the one bead core to the other bead core. And a bead filler disposed between a winding portion wound up by the bead core and The one or more non-extensible fiber cords are spirally wound in the circumferential direction of the tire to form a belt having a fixed radial width. Wherein the formed circumferential cord reinforcing layer is disposed in at least one portion of a region from a radially inner side of an axial end portion of the belt layer to a radially outer side of the bead portion. tire. 2. The pneumatic radial tire according to claim 1, wherein the circumferential cord reinforcing layer is disposed adjacent to an inner side or an outer side in the axial direction of a main body of the carcass layer. 3. The pneumatic radial tire according to claim 1, wherein the circumferential cord reinforcing layer is disposed around a maximum width portion of a side region of the tire. 4. The tire according to claim 1, wherein the circumferential cord reinforcing layer is provided in a region from a maximum width portion of a side region of the tire to a radial inside of an axial end portion of the belt layer. Pneumatic radial tire. 5. The pneumatic radial tire according to claim 1, wherein the circumferential cord reinforcing layer is disposed in a region from a maximum width portion of a side region of the tire to a radially outer side of the bead portion. . 6. The radial width (L) of the circumferential cord reinforcing layer is in a range of 7 to 40% of a section height (SH) in a cross section including a rotation axis of the tire. 5
The pneumatic radial tire according to any one of the above items. 7. The radial width (L) of the circumferential cord reinforcing layer is in a range of 30 to 40% of a section height (SH) in a cross section including a rotation axis of the tire. 6. The pneumatic radial tire according to any one of items 5 to 5. 8. The pneumatic radial tire according to claim 1, wherein the non-extensible fibers of the circumferential cord reinforcing layer are polyamide, polyimide, or polyester fibers. 9. The pneumatic radial tire according to claim 1, wherein a cord driving density of the circumferential cord reinforcing layer is 3 to 20 cords per 10 mm width of the reinforcing layer.