JP2001180221A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lighten a tire while ensuring the comfort in riding and improve the steering stability. SOLUTION: A belt layer 7 includes the ply 20 using a monofilament cord 10, and the ply 21 using a multifilament cord 11. The monofilament cord 10 has an approximately circular cross section of 0.09-0.30 mm2, and is provided with the spiral or waveform pattern. In the case of the spiral pattern, a patterning pitch PA is 14-50 mm, and a patterning height HA is 0.002-0.02 times of the patterning pitch PA. In the case of the waveform pattern, the patterning pitch PB is 5-50 mm, and the patterning height HB is 0.002-0.05 times of the patterning pitch PB.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention can achieve a reduction in tire weight and an improvement in steering stability while ensuring ride comfort by using a monofilament belt ply and a multifilament belt ply for a belt layer. It relates to a pneumatic radial tire.

[0002]

2. Description of the Related Art As a belt cord for a pneumatic radial tire, a multifilament cord in which a plurality of thin steel filaments are twisted with each other has been widely used.

On the other hand, in recent years, it has been proposed to form a belt cord with a single monofilament of steel. This monofilament cord can increase the ratio of cord stiffness to cord strength compared to conventional multi-filament cords, thus increasing belt stiffness while keeping cord usage low, reducing weight and maneuvering. There is an advantage that stability can be improved at the same time.

[0004]

On the other hand, since the monofilament cord has a high cord rigidity as described above, the ride comfort is remarkably reduced, and it is difficult to improve running performance in a well-balanced manner. there were.

Accordingly, the present invention is based on the fact that a belt layer is formed of a belt ply of a monofilament cord and a belt ply of a multifilament cord. It is intended to provide a pneumatic radial tire that can achieve the following.

[0006]

In order to achieve the above object, a first invention of the present application is directed to a carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a carcass inside the tread portion and at a carcass portion. A pneumatic radial tire having a belt layer composed of two or more belt plies disposed on the outside of the pneumatic radial tire, wherein the belt plies are a monofilament belt ply using a steel monofilament cord, and a plurality of steel plies. And a multi-filament belt ply using a multi-filament cord in which filaments are twisted, wherein the monofilament cord has a cross-sectional area of 0.09 to 0.3.
0 mm ² , forming a substantially circular cross section, and in addition, spiral or wavy shaping is performed in the longitudinal direction, and in the case of spiral shaping, the shaping pitch PA
Is set to 14 to 50 mm, and the shaping height HA is set to 0.002 to 0.02 times the shaping pitch PA. In the case of corrugated shaping, the shaping pitch PB is set to 5 to 50 m.
m, and the molding height HB is set at 0.
002 to 0.05 times.

In the pneumatic radial tire according to the second aspect of the present invention, the monofilament cord has a sectional area of 0.0
9 to 0.30 mm ² , forming a horizontally long flat cross section, and a flattening rate of 0.65 to 0.9, which is a ratio Dh / Dw of the minor axis Dh in the minor axis direction to the major axis Dw in the major axis direction in the oblong flat section.
5, and a spiral or corrugated pattern is formed in the longitudinal direction. In the case of a spiral pattern, the patterning pitch PA is 14 to 50 mm, and the patterning height HA is set to the patterning pitch PA. 0.002-0.
In the case of corrugated shaping, the shaping pitch PB is 5 to 50 mm, and the shaping height HB is 0.002 to 0.05 times the shaping pitch PB.

In the pneumatic radial tires according to the first and second aspects of the present invention, it is preferable that the monofilament belt ply be disposed radially outermost in the belt layer.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show meridional sections when the pneumatic radial tire 1 (hereinafter referred to as tire 1) of the present application is formed as a heavy-duty tire such as a tire for a passenger car, a tire for a small truck, and a truck / bus, respectively. ing.

1 to 3, a tire 1 includes a tread portion 2, sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and a bead portion 4 located at an inner end of each sidewall portion 3. It has. A carcass 6 is bridged between the bead portions 4 and 4 on the tire 1, and a belt layer 7 is wound around the carcass 6 in the radial direction outside of the carcass 6 and inside the tread portion 2.

The carcass 6 has a main body 6A extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3, and a folded portion 6B connected to both ends thereof and folded around the bead core 5. . A bead apex rubber 8 made of a hard rubber that extends radially outward from the bead core 5 in a tapered shape is disposed between the main body 6A and the folded portion 6B, and is reinforced from the bead portion 4 to the sidewall portion 3. I have.

The carcass 6 is formed from one or more carcass plies in which carcass cords are arranged at an angle of 75 ° to 90 ° with respect to the tire circumferential direction. The carcass cords include nylon, rayon, polyester, and fragrance. A cord obtained by twisting a plurality of filaments made of an organic fiber such as an aromatic polyamide or steel or the like can be suitably used.

Next, as shown in FIGS. 1 to 4, the belt layer 7 is a monofilament belt ply 20 in which steel monofilament cords 10 are arranged at an angle of, for example, 15 to 30 degrees with respect to the tire circumferential direction. And a multifilament belt ply 21 in which a multifilament cord 11 formed by twisting a plurality of steel filaments 11a is arranged at an angle of, for example, 15 to 70 degrees with respect to the tire circumferential direction.

In this embodiment, the belt layer 7 is formed of one of the monofilament belt plies 20 and the multifilament belt plies 21 in the passenger car tire shown in FIG.
In the tire for a small truck shown in FIG. 2, one of the monofilament belt plies 20 and the two of the multifilament belt plies 21
In the heavy duty tire shown in FIG. 3, each of the monofilament belt plies 20 and the multifilament belt plies 21 is illustrated as an example.

As described above, by mixing the monofilament belt ply 20 and the multifilament belt ply 21, the characteristics of the monofilament cord 10, that is, the cord rigidity and the belt rigidity are increased while keeping the cord usage low, and the weight is reduced. This makes it possible to secure the necessary ride comfort and improve the running performance in a well-balanced manner while taking advantage of the fact that the improvement in driving stability can be achieved at the same time. Furthermore, since the movement of the tire near the outer end of the belt layer 7 can be suppressed by increasing the belt rigidity, an effect of reducing the noise in the vehicle (road noise) can be expected.

This effect is obtained by disposing the monofilament belt ply 20 on the outermost side in the radial direction.
It is more effective.

Here, the multifilament cord 11 used for the multifilament belt ply 21 is not particularly limited, and the twist structure and the thickness of the filament 11a are taken into consideration in consideration of the belt rigidity of the monofilament belt ply 20 and the like. Are appropriately set. That is, in this example, a 1 × 5 bundle twist structure in which five filaments 11a are twisted is illustrated.
5 (A) to (C), 1 × 2, 1 × 3, 1 × 4
Or a layer-twisted structure in which one or more sheaths are formed around a core.

The monofilament belt ply 20
The monofilament cord 10 used in the present invention may have a substantially circular cross-section or a horizontally long flat cross-section. In each case, the cross-sectional area S is 0.09 to 0.30 mm ^2.
It is necessary to

When the sectional area S is less than 0.09 mm ² ,
The characteristics of the monofilament cord 10 are not exhibited, and the rigidity of the cord is insufficient, and the cornering power becomes too small, so that it is difficult to secure the steering stability. 0.30m
If m ² is exceeded, the cord stiffness becomes excessive, so that the ride comfort cannot be ensured even by using the multifilament belt ply 21. In addition, there is also a problem that the durability of the cord is drastically deteriorated such that the cord per cord becomes too thick and the residual stress increases.

Therefore, the cross-sectional area S is 0.09-0.
A range of 25 mm ² is preferred. In this example, the product S × N of the cross-sectional area S and the number of cords N (number of wires / 5 cm) is used.
Is less than 0.85 times the value S × N of the multi-filament belt ply 21, the amount of steel is reduced, and the belt material is greatly reduced in weight.

In the monofilament cord 10,
By applying a spiral or wavy shape, elongation characteristics in the longitudinal direction can be imparted, and thereby, durability against repeated compression deformation can be improved.

More specifically, the monofilament cord 10A having a substantially circular cross section can be spirally or corrugated in the longitudinal direction.

As shown in FIG. 5, the helical molding may be performed in a normal spiral shape having no bent portion and smoothly continuous, or as shown in FIG. 6, a substantially polygonal shape in a front view. Bent part 15A and straight part 15B
And a spiral shape alternately turned over.

When such a spiral molding is performed, the longitudinal molding pitch PA is 14 to 50 mm, and the molding height HA is 0.002 to 0.005 of the molding pitch PA.
Preferably, it is 0.02 times.

As shown in FIG. 7, the shape of the corrugated shape was smoothly continuous without having a bent portion.
For example, a normal wave shape such as a sine curve, or FIG.
As shown in the figure, a wave shape such as a zigzag shape in which a wave shape curved portion 16A and a straight portion 16B are alternately turned back can be adopted. Further, as shown in FIG. 9, in addition to the molding of the one side F1, it is also possible to perform the molding of the other side F2. At this time, the molding of the one side F1 and the molding of the other side F2 are formed in a perpendicular direction as illustrated. Preferably, but not necessarily.

When such a corrugated mold is formed, the mold pitch PB in the longitudinal direction is 5 to 50 mm, and the mold height HB is 0.002 to 0 .0 of the mold pitch PB.
It is preferably set to 05 times. When the other side F2 is provided with a mold, similarly, the mold pitch PB2 in the mold of the other side F2 is 5 to 50 mm, and the mold height HB2 is 0.002 of the mold pitch PB2.
Preferably it is 0.05 times.

When the molding pitches PA, PB, PB2 are each greater than 50 mm, and when the molding heights HA, H
B and HB2 are less than 0.002 × PA and 0.002 ×, respectively.
When it is less than PB and less than 0.002 × PB2, the elongation characteristics of the monofilament cord 10A become insufficient. Conversely, when the molding pitch PA is less than 14 mm, or when the molding pitches PB and PB2 are each less than 5 mm, the deformation of the monofilament in the tire during running increases, and the durability of the cord deteriorates.

The molding heights HA, HB, HB2 are larger than 0.02 × PA, larger than 0.05 × PB, respectively.
When it is larger than 0.05 × PB2, the damage caused by the molding applied to the monofilament is increased, and the strength and the fatigue property are easily reduced.

Next, as the monofilament cord 10, as shown in FIG. 10, a monofilament cord 10B having a horizontally long flat cross section can be suitably used.

In such a case, the ratio of the minor axis Dh in the minor axis direction to the major axis Dw in the major axis direction, Dh / Dw, having an aspect ratio of 0.65 to 0.95 is used. The shaft is arranged in the thickness direction of the belt ply 20.

As described above, the monofilament cord 10
When B has a horizontally long flat cross-sectional shape, and its short axis is arranged in the thickness direction of the ply, the deformation in the tire axial direction is substantially the same as increasing the number of cords driven. For example, the in-plane rigidity of the belt layer 7 is greatly increased. As a result, compared to the monofilament cord 10A having the circular cross section, the steering stability can be further improved by further increasing the cornering power.
Moreover, in the tire radial direction, the bending rigidity (out-of-plane rigidity) inward and outward in the radial direction of the belt layer 7 is suppressed to be low, for example, the flattening makes it easy to bend and becomes flexible.
This makes it possible to minimize the reduction in ride comfort.

When the flattening ratio Dh / Dw exceeds 0.95, the above-mentioned effect is substantially at the same level as that of the monofilament cord 10A having the circular cross section. The strength is likely to be reduced.

In the monofilament cord 10B having a horizontally long flat cross section, a spiral or corrugated pattern can be similarly formed in the longitudinal direction.

As shown in FIG. 10, the helical molding may be a normal helical shape smoothly continuous without any bent portion, or a substantially polygonal shape in a front view as shown in FIG. Bent part 15A and straight part 15
A spiral shape in which B is alternately turned can be employed.

When applying such a spiral mold,
As in the case of the monofilament 10A having the circular cross section, the molding pitch PA in the longitudinal direction is 14 to 50 mm, and the molding height HA is 0.002 to 0.002 of the molding pitch PA.
Preferably, it is 0.02 times.

In addition, as shown in FIG. 12, the corrugation can be formed in a normal wave shape such as a sine curve shape which is smoothly continuous without having a bent portion, or as shown in FIG.
As shown in the figure, a wave shape such as a zigzag shape in which a wave shape curved portion 16A and a straight portion 16B are alternately turned back can be adopted, and both are applied in the short axis direction. Further, as shown in FIG. 14, in addition to the molding in the short axis direction, the molding in the long axis direction can be performed.

When such a corrugated mold is formed, the mold pitch PB in the longitudinal direction is 5 to 50 mm, and the mold height HB is 0.002 to 0.
It is preferably set to 05 times. When the molding is performed in the major axis direction, the molding pitch PB2 in the major axis direction is set to 5 to 50 mm, and the molding height HB2 is set to 0.002 to 0.
It is preferably set to 05 times.

When the molding pitches PA, PB, PB2 are each greater than 50 mm, and when the molding heights HA, H
B and HB2 are less than 0.002 × PA and 0.002 ×, respectively.
When it is less than PB and less than 0.002 × PB2, the elongation characteristics of the monofilament cord 10A become insufficient. Conversely, when the molding pitch PA is less than 14 mm, or when the molding pitches PB and PB2 are each less than 5 mm, the deformation of the monofilament in the tire during running increases, and the durability of the cord deteriorates.

The molding heights HA, HB, HB2 are larger than 0.02 × PA, larger than 0.05 × PB, respectively.
When it is larger than 0.05 × PB2, the damage caused by the molding applied to the monofilament is increased, and the strength and the fatigue property are easily reduced.

In the tire 1, outside the belt layer 7,
A band layer (not shown) that prevents the lifting and enhances high-speed durability can be provided. This band layer
For example, it is a so-called endless band ply in which a nylon textile cord is spirally wound at an angle of 0 to 5 ° with respect to the tire circumferential direction, and covers at least the outer end of the belt layer 7.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Tire size 205/65 having the structure of FIG.
According to the specifications of Tables 1 and 2, the R15 passenger car tire is shown in FIG.
Tire size 205 / 85R16 117 with the structure of
/ 115L light truck tires and 11R22.5 heavy load tires having the structure shown in FIG. 3 were prototyped according to the specifications in Table 3, and the tire weight, durability, steering stability, The riding comfort was tested, and the results are shown in Tables 1, 2, and 3, respectively.
The test is as follows.

(1) Tire Weight The weight per tire is measured and is indicated by an index with the conventional example of each size being 100. The smaller the index, the lighter the index.

(2) Durability For passenger car tires, the rim (15 × 6JJ) and internal pressure (20
0kPa), attached to all the wheels of a passenger car (3000cc), and a figure-8 course consisting of two circles of 14m in diameter
After turning the figure eight times repeatedly, the tire is disassembled and the number of cut portions of the belt cord is counted, and the number is indicated by an index with the conventional example being 100. The smaller the index, the better the number of cut points. For light truck tires, the rim (16 × 6K) and internal pressure (600 kPa) are attached to all wheels of the light truck, and for heavy load tires, the rim (22.5
× 8.25), attached to all the wheels of the truck at an internal pressure (800 kPa), and after traveling about 20,000 km on a bad road, the tire was disassembled and the number of cuts of the belt cord in the outermost belt ply was counted. Is represented by an index with the conventional example as 100. The smaller the index, the better the number of cut points.

(3) Driving stability The passenger car, light truck, or truck is used to drive on a dry asphalt road on a tire test course, and the characteristics relating to steering wheel responsiveness, rigidity, grip, and the like are evaluated by a ten-point method based on a sensory evaluation by a driver. Was evaluated. The larger the value, the better the steering stability.

(4) Ride Comfort Using the above-mentioned passenger car, light truck, or truck, a rugged feeling and pushing up on a stepped road on a dry asphalt road, a Berjaso road (cobblestone road surface), a Bitzmann road (a road surface covered with pebbles), and the like. The sensory evaluation of the driver regarding damping was performed, and the evaluation was made according to the 10-point method. The larger the value, the better the ride comfort.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

As described above, according to the present invention, the belt layer is formed by the belt ply of the monofilament cord and the belt ply of the multifilament cord. It is possible to achieve improved stability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view when an embodiment of the present invention is formed as a passenger car tire.

FIG. 2 is a cross-sectional view when an embodiment of the present invention is formed as a light truck tire.

FIG. 3 is a cross-sectional view when an example of the present invention is formed as a heavy duty tire.

FIG. 4 is a sectional view showing a belt layer.

FIG. 5 is a diagram showing an example of spiral molding of a monofilament cord having a circular cross section.

FIG. 6 is a diagram showing another example of the spiral molding.

FIG. 7 is a diagram showing an example of corrugated molding of a monofilament cord having a circular cross section.

FIG. 8 is a diagram showing another example of the waveform shaping.

FIG. 9 is a diagram showing still another example of the waveform shaping.

FIG. 10 is a diagram showing an example of spiral molding of a monofilament cord having a horizontally long flat cross section.

FIG. 11 is a diagram showing another example of the spiral molding.

FIG. 12 is a diagram showing an example of corrugation of a monofilament cord having a horizontally long flat cross section.

FIG. 13 is a diagram showing another example of the waveform shaping.

FIG. 14 is a diagram showing still another example of the waveform shaping.

FIGS. 15A to 15C are cross-sectional views showing other examples of the multifilament cord.

[Explanation of symbols]

 Reference Signs List 2 tread part 3 side wall part 4 bead part 5 bead core 6 carcass 7 belt layer 10, 10A, 10B monofilament cord 11 multifilament cord 11a filament 20 monofilament belt ply 21 multifilament belt ply

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazumi Yamazaki 3-6-9, Wakihama-cho, Chuo-ku, Kobe City, Hyogo Prefecture Within Sumitomo Rubber Industries, Ltd. (72) Inventor Takushi Kusumoto 3 Wakihama-cho, Chuo-ku, Kobe City, Hyogo Prefecture 6-6-9 Sumitomo Rubber Industries Co., Ltd. F-term (reference) 3B153 AA24 BB01 BB05 BB13 BB20 CC52 FF16 GG40

Claims (4)

[Claims] 1. A carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a belt layer including two or more belt plies disposed inside the tread portion and outside the carcass. A pneumatic radial tire, wherein the belt ply comprises at least a monofilament belt ply using a steel monofilament cord and a multifilament belt ply using a multifilament cord obtained by twisting a plurality of steel filaments. The monofilament cord has a cross-sectional area of 0.09 to
It is 0.30 mm ² , has a substantially circular cross section, and is spirally or corrugated in the longitudinal direction. In the case of spiral molding, the molding pitch PA is set to 1
4 to 50 mm, and the molding height HA is 0.002 to 0.02 times the molding pitch PA. In the case of corrugated molding, the molding pitch PB is 5 to 50 mm and the molding height HB is A pneumatic radial tire characterized in that the pitch PB is 0.002 to 0.05 times. 2. The pneumatic radial tire according to claim 1, wherein the belt layer has a monofilament belt ply disposed radially outermost. 3. A carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a belt layer including two or more belt plies disposed inside the tread portion and outside the carcass. A pneumatic radial tire, wherein the belt ply comprises at least a monofilament belt ply using a steel monofilament cord and a multifilament belt ply using a multifilament cord obtained by twisting a plurality of steel filaments. The monofilament cord has a cross-sectional area of 0.09 to
0.30 mm ² , forming a horizontally elongated flat cross section, and the minor axis direction minor axis Dh and the major axis major axis Dw of the horizontal elongated planar section.
And a flattening ratio of 0.65 to 0.95, which is a ratio of Dh / Dw, is formed in a spiral or wavy shape in the longitudinal direction. In the case of a spiral shaping, the shaping is performed. 1 pitch PA
4 to 50 mm, and the molding height HA is 0.002 to 0.02 times the molding pitch PA. In the case of corrugated molding, the molding pitch PB is 5 to 50 mm and the molding height HB is A pneumatic radial tire characterized in that the pitch PB is 0.002 to 0.05 times. 4. The pneumatic radial tire according to claim 3, wherein the belt layer has a monofilament belt ply disposed radially outermost.