JP2002096606A - Tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire which is light in weight and excels in handling stability, vibrational riding comfortability and road noise control performance. SOLUTION: Characteristics of this tire are that it possesses belt layers and belt-reinforcing layers arranged outside the belt layers in the radial direction of the tire, that cords embedded in the belt layers consist of polyester-type monofilament cords, and that the cords embedded in the belt-reinforcing layers consisting of polyester-type twisted cords.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire, and more particularly to a radial tire which is lightweight and has excellent road noise.

[0002]

2. Description of the Related Art Conventionally, a steel cord is generally used as a belt material of a pneumatic radial tire for a passenger car, and an aliphatic amide fiber cord is generally used as a belt reinforcing material.
However, in recent years, there has been a great demand for lighter weight and lower rolling resistance of tires as fuel economy of passenger cars has been reduced.
In view of this, the present inventor has achieved a tire weight reduction using a polyester monofilament for a belt layer in Japanese Patent Application Laid-Open No. 9-188106.

[0003]

However, although the steering stability and the vibration riding comfort have become about the same as those of the conventional steel belt tires due to the lightening technology, road noise, which is one of the riding noises, has been improved. Is one step short of steel belts, and the demand for tire weight reduction was achieved, but it turned out to be a drawback for mounting in low noise tire fields for luxury vehicles. Under such circumstances, an object of the present invention is to provide a tire that is lightweight and has excellent driving stability, vibration riding comfort, and road noise.

[0004]

As a result of intensive studies on the above problems, it has been found that noise can be reduced by making the cord of the tire belt reinforcing layer higher in modulus than conventional nylon. Therefore, if polyester or polyethylene naphthalate, which has a higher modulus than nylon, is used for the belt reinforcement layer, it is possible to reduce tire weight and reduce noise more than conventional tires with steel belt and nylon belt reinforcement layer. The present invention has been completed.

That is, the present invention provides: (1) a belt layer, and a belt reinforcing layer disposed radially outside the belt layer in a tire radial direction, and the cord embedded in the belt layer is made of a polyester monofilament cord. And a cord embedded in the belt reinforcing layer is made of a polyester twisted cord.

(2) The tire according to (1), wherein the polyester monofilament cord has a diameter of 0.4 mm or more and 1.2 mm or less, and the degree of orientation of its surface layer is smaller than that of its central part. (3) The tire according to (1) or (2), wherein the polyester constituting the polyester-based monofilament cord has a melt viscosity of 0.8 or more.

(4) The tire according to any one of (1) to (3), wherein the polyester resin constituting the polyester monofilament cord contains at least 85% by weight of polyethylene naphthalate and / or polyethylene terephthalate. (5) 2. The polyester monofilament cord.
The elongation under a load of 5 g / dtex (decitex) is 1.
The tire according to any one of (1) to (4), wherein the tire content is 8% or more and 5% or less. (6) The belt layer is a cross belt (1) to (5).
The tire according to any one of claims 1 to 4.

(7) The twist coefficient of the polyester twisted cord is from 0.15 to 0.60.
The tire according to any one of (6). (8) The polyester resin constituting the polyester twisted cord contains at least 90% by weight of polyethylene naphthalate and / or polyethylene terephthalate.
The tire according to any one of (1) to (7).

[0009]

Embodiments of the present invention will be described below. First, the structure of the tire to be the object of the present invention is as follows.
The structure is not particularly limited, and can be appropriately selected from known structures such as a radial tire and a bias tire. For example, a pair of left and right bead portions, a carcass portion disposed between the bead portions, a belt portion disposed outside the carcass portion in the tire radial direction, and a belt portion disposed outside the belt portion in the tire radial direction. A tread portion, a pair of sidewall portions disposed on the left and right sides of the tread, and an inner liner portion disposed inside the carcass portion may be provided, and each portion may be composed of a single layer. Multiple layers may be combined. Further, the tire of the present invention can be used by filling the inside thereof with a gas such as air or nitrogen.

The tire of the present invention is characterized in particular by the cord material of the belt layer and the belt reinforcing layer on the outer side in the tire radial direction. Here, the polyester monofilament cord used for the belt layer has a diameter of 0.4 mm or more,
The diameter is preferably 1.2 mm or less, and more preferably 0.5 mm or more and 0.9 mm or less. 0.4mm in diameter
In the following, it is not only difficult to secure sufficient bending and compression stiffness compared to steel cord, but also the number of shots per fixed width driven into the belt layer has a certain limit,
0.4 mm or more is preferable also in ensuring belt strength. On the other hand, if the thickness is larger than 1.2 mm, the thickness of the belt gauge is increased, which increases the weight of the tire and increases heat generation during running of the tire.

The polyester monofilament cord used for this belt is made of polyethylene terephthalate (PET), polyethylene naphthalate (PE).
N) is preferably used, but a monofilament cord containing 85% or more of polyethylene terephthalate or polyethylene naphthalate, or a monofilament cord obtained by mixing both polymers may be used.
In particular, in the case of polyethylene terephthalate, a high molecular weight polyethylene terephthalate having a melt viscosity of 0.8 or more is preferable in order to ensure fatigue resistance, and if the melt viscosity is less than 0.8, it is difficult to ensure the fatigue resistance of the cord. .

In order to further ensure sufficient fatigue,
It is necessary that the degree of molecular orientation of the surface layer constituting the monofilament cord is lower than or at least equal to the degree of orientation of the central part of the monofilament cord. If the surface orientation is larger than the central orientation, the monofilament surface layer is likely to be flagged when the monofilament is subjected to bending or compression input, and the fatigue property tends to decrease.

Further, since the strain is concentrated only on the surface layer of the filament, the fatigue resistance of the monofilament itself is reduced. From the above, it is preferable that the intrinsic viscosity of the polyester monofilament is 0.8 or more, and the molecular orientation of the monofilament surface layer is lower than the orientation inside the monofilament. The cross-sectional shape of the monofilament cord is not particularly limited, such as a circle, an ellipse, a rectangle, a square, and a polygon. However, a monofilament cord having a circular or slightly elliptical cross-section is advantageous in terms of production.

Such a monofilament cord is subjected to a normal bonding treatment to provide a belt intersecting layer similar to that of a steel cord belt. Due to the shortage, about 1.
It is preferable to use a monofilament cord having a volume of 5 times.

The total cord volume of the monofilament used for the belt is about 1.5 times that of the steel cord. However, since the specific gravity is much smaller than that of steel, the weight of the belt layer can be reduced by half, and although it depends on the structure of the tire, it is 7 times. The tire weight can be reduced by 10% to 10%. Also, the belt angle may be the same as that of a normal steel cord, but it is preferable to set the belt angle to be smaller by about 2 degrees with respect to the tire circumferential direction in order to obtain the same or better performance as a steel cord tire.

Generally, in the case of a steel belt, when the belt angle is reduced, the steering stability of the tire is improved, but there is a disadvantage that the riding comfort of the tire is reduced. However, in the case of the monofilament cord, even if the angle at which the cord is driven is reduced, the tire steering stability is improved, but the ride comfort is hardly affected by changing the belt angle.

The twisted cord used for the belt reinforcing layer may be a single component of polyethylene terephthalate or polyethylene naphthalate, or a twisted cord of polyethylene terephthalate or polyethylene naphthalate containing 90 mol or more of these components. The twist coefficient is preferably 0.15 or more and 0.60 or less. If the twist coefficient is less than 0.15, not only is it difficult to ensure fatigue, it is also difficult to keep the cross section of the cord in a circular shape, and there is a possibility that a problem of contact with the adjacent cord may occur. In addition, the twist coefficient is 0.
If it is greater than 60, the cord strength and modulus tend to decrease, so the twist coefficient is preferably 0.60 or less.

These monofilament cords and / or twisted cords are treated in the same heat and adhesive treatment steps as ordinary polyester tire cords, but the monofilament cord of the belt material is stretched under a load of 2.5 g / dtex. The degree is preferably 5% or less and 1.8% or more. 2.5g
If the elongation at the time of / dtex is large, the belt rigidity tends to decrease, and the tire steering stability tends to decrease. Therefore, it is more preferably 4% or less. The smaller the elongation, the better the tire steering stability. However, if the elongation is too small, the tire uniformity tends to deteriorate.
Below 2.8% or more. The twisted cord subjected to the adhesive treatment was wound on the belt layer at an angle of about 0 ° with respect to the circumferential direction of the tire to form a belt reinforcing layer.

[0019]

Embodiments of the present invention will be described below. In Examples, parts and% mean parts by weight and% by weight, respectively, unless otherwise specified. Various measurements were made according to the following methods.

(1) Twisting factor Twisting factor _NT = N × √ (0.139 × D / ρ) × 10 ^-3 However, N is the number of twists per 10 cm (T / 10c
m), D is の of code total denier, ρ is
Specific gravity (1.38 for polyester).

(2) Method of measuring IV (intrinsic viscosity) of polymer A raw yarn of polyester was sufficiently washed with water, and dried under reduced pressure was used as a sample. A predetermined amount of a sample is weighed, dissolved in a mixed solvent of parachlorophenol and tetrachloroethane (weight ratio: 3: 1), and Ubb placed in a thermostat at 30 ° C.
The flow time of the solvent and each concentration solution was measured by an elohde viscosity tube, and the relative viscosity η _r of each solution was measured. The specific viscosity η _sp is determined from the relative viscosity, and the
It was calculated using the equation of s.

(3) Intermediate elongation According to JISL L1017-1995, a cord subjected to dipping treatment at room temperature of 25 ° C. ± 2 ° C. is pulled at a constant speed by an autograph manufactured by Shimadzu Corporation at a constant speed until the cord is cut. The SS curve was determined. In addition, 2.5g
/ Dtex (decitex)) elongation under load is 2.25
g / dtex (decitex) x elongation (%) under load of code decitex.

(4) Drum Durability Test After adjusting the prototype tire to a maximum air pressure of JIS standard in a room at 25 ° C. ± 2 ° C., let it stand for 24 hours, readjust the air pressure, and adjust the tire to the maximum load of JIS standard of 2 A double load was applied to the tire, and the tire was run on a 1.7 m diameter drum at a speed of 60 km / hour, and the running distance until the occurrence of a failure was measured. 20,000km
Completed the tires with no failures up to.

(5) Steering stability The test tires were mounted on a passenger car with a displacement of 2000 cc and four test tires were mounted thereon, and two test drivers performed actual driving on a dry surface to improve steering wheel responsiveness and steering controllability. Comprehensive evaluation was made to evaluate the steering stability. The results were expressed by the following scores using the tire of Comparative Example 1 as a control. -Positive (minus) 1 and 2 are levels that are slightly better (or slightly worse) compared to controls.-Positive or negative 2 scores are levels at which the difference can be recognized by ordinary drivers.-Positive (minus) 3 and 4 are controls. It is much better (or worse), and there is a level difference that even ordinary drivers can fully recognize the difference.

(6) Road noise test A 195 / 60R15 test tire was subjected to an internal pressure of 2.0 kgf /
cm ^2, 4-wheel at the rim size 6J-14 to exhaust the amount sedan type of passenger car of 2000cc mounted, two people riding on a test course of road noise evaluation road, 60km / h
, And a sound collecting microphone was attached to the center of the backrest portion of the driver's seat, and the total sound pressure (decibels) at a frequency of 100 to 500 Hz was measured. This is shown by the number of decibels lower than the road noise value of the control tire of Comparative Example 1. The greater the decrease in decibels compared to the control tire, the lower the road noise.

Examples and Comparative Examples Each example and comparative example has a tire size of 195 / 60R1.
5 and the structure is as shown in FIG. That is, a bead portion 1 surrounding a pair of annular bead wires 6, a bead filler (bead reinforcing rubber portion) 9, a toroidal carcass ply 4 extending over both bead portions, and a tread located at a crown portion of the carcass ply. Part three,
A radial structure having the sidewall portion 2 of the carcass ply 4 and having a belt layer 5 inside the tread portion 3 and belt reinforcing layers 7 and 8 disposed outside the belt layer in the tire radial direction. Have. In this tire, the carcass ply cord is disposed at an angle of substantially 90 degrees with respect to the circumferential direction of the tire, and the number of hits is 50/5 cm, and has the same structure and pattern as a normal tire. ing. The structure of the belt and belt reinforcement layer
The results are shown in the following Comparative Examples and Examples.

COMPARATIVE EXAMPLE 1 A normal steel cord having a 1 × 3 structure with a strand diameter of 0.3 mm in a belt layer was used as a rubberized cloth having a number of driving of 32 per 5 cm width. It was stuck to the tire in the usual way so that it was 24 degrees. The number of belt layers is two, and the belts 1 and 2 have belt angles that intersect each other. The belt reinforcing layer is 66 nylon 1400 dtex / 2, and the number of twists is 23 × 2.
An ordinary belt reinforcing layer cord of 3T / 10 cm was wound by a usual method at a driving number of 50/5 cm so as to be almost 0 degree with respect to the tire circumferential direction. This tire was subjected to each test as Comparative Example 1, which had exactly the same structure and manufacturing method as those on a normal market.
Table 1 shows the obtained tires as controls.

Comparative Example 2 Instead of steel, a cord of 0.55 mm diameter polyester monofilament 3330 dtex was used for the belt layer. The number of cords to be driven was 48/5 cm, the belt angle was 22 degrees with respect to the tire circumferential direction, and two crossed layers were formed as in Comparative Example 1. The belt reinforcing layer is a 66 nylon cord exactly as in Comparative Example 1. The test results are shown in Table 1. From Table 1, both the tire steering stability and the vibration riding comfort were the same as Comparative Example 1, but the road noise was lower than that of the control.

Example 1 In Example 1, a belt structure similar to that of Comparative Example 2 was used, but a normal polyester (PET) tire cord of 1670 dtex / 2 was used as a belt reinforcing material, and the number of twists was 23 × 2.
A cord that has been twisted 3 times / 10 cm and subjected to a normal bonding treatment is applied with a normal method in a direction substantially equal to 0 in the tire circumferential direction.
It was wound at a driving number of 50 pieces / 5 cm so as to obtain a degree. The test results are shown in Table 1. From Table 1, since the polyester cord has a higher modulus than the nylon cord and the rigidity of the entire belt portion is improved, Comparative Example 1 or Comparative Example 2
At the same time as the tire steering stability is improved, Comparative Example 1,
Alternatively, the road noise was reduced as compared with Comparative Example 2.

Embodiment 2 In Embodiment 2, the belt cord is the same as in Embodiment 1, but
A belt obtained by using a polyethylene naphthalate (PEN) in place of the polyester cord of Example 1 and twisting with a number of twists of 23 × 23/10 cm and applying a normal bonding treatment to the belt reinforcing member by a normal method. It was wound at a driving number of 50 pieces / 5 cm so as to be almost 0 degree with respect to the circumferential direction. The test results are shown in Table 1. Example 1 from Table 1
The tire handling stability has been improved and the road noise has been reduced as compared with the polyester cord of the company.

Comparative Example 3 In Comparative Example 3, a polyester monofilament 1670 having a diameter of 0.39 mm was used instead of the belt material of Example 1.
dtex code was used. The number of cords to be driven was 48 / 5cm, and the belt angle was 2 with respect to the tire circumferential direction.
This is two times, as in Comparative Example 1.
The belt reinforcing layer was made of PET1670d similar to that of Example 1.
Table 1 shows the test results using tex / 2 at the same time. From Table 1, the rigidity was lower than that of Example 1, so that the tire performance was lower and the road noise was lower than the control.

COMPARATIVE EXAMPLE 4 In Comparative Example 4, the belt material of Example 1 was replaced with a diameter of 0.3 mm.
55 mm commercial polyester monofilament 334
A code of 0 dtex was used. The number of cords to be driven was 50/5 cm, the belt angle was 22 degrees with respect to the tire circumferential direction, and two crossed layers were formed as in Comparative Example 1.
The test results are shown in Table 1. From Table 1, this commercially available polyester monofilament cord has an IV of 0.75 and a polyester monofilament cord of 0.89 used in the present invention.
However, the arrangement of the monofilament surface was lower than the degree of orientation at the central portion of the monofilament, so that the fatigue resistance was poor, the drum durability level was low, and the level could not be put to practical use.

[0033]

[Table 1]

[0034]

As described above, the tire of the present invention
Since the cord embedded in the belt layer is made of a polyester monofilament cord, and the cord embedded in the belt reinforcing layer is made of a polyester twisted cord, the weight of the tire is reduced and, at the same time, the steering stability is improved. In addition, the road noise is reduced and the riding comfort is improved. From this, in recent years, it is possible to sufficiently cope with the demand for lighter tires and lower rolling resistance due to lower fuel consumption of passenger cars in recent years, and at the same time, it is particularly suitable for mounting in low noise tire fields for luxury cars.

[Brief description of the drawings]

FIG. 1 is a partially cutaway sectional view of a pneumatic tire showing an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead part 2 Side fall part 3 Tread part 4 Carcass ply 5 Belt layer 6 Annular bead wire 7 Belt reinforcement layer 8 Belt reinforcement layer 9 Bead filler

Claims (8)

[Claims] 1. A belt layer, and a belt reinforcing layer disposed radially outside of the belt layer in a tire radial direction, wherein a cord embedded in the belt layer is made of a polyester monofilament cord, and the belt is reinforced. A tire characterized in that the cord embedded in the layer comprises a polyester twisted cord. 2. The polyester monofilament cord according to claim 1, wherein the diameter of the polyester monofilament cord is 0.4 mm or more and 1.2 mm or less, and the degree of orientation of its surface layer is smaller than the degree of orientation of its central part. The described tire. 3. The tire according to claim 1, wherein the polyester constituting the polyester monofilament cord has an intrinsic viscosity of 0.8 or more. 4. The polyester resin constituting the polyester-based monofilament cord is made of polyethylene naphthalate and / or polyethylene terephthalate.
The tire according to any one of claims 1 to 3, wherein the content of the tire is not less than% by weight. 5. The polyester monofilament cord according to claim 1, wherein the elongation under a load of 2.5 g / dtex (decitex) is 1.8% or more and 5% or less. The tire described in the above. 6. The tire according to claim 1, wherein the belt layer is a cross belt. 7. The tire according to claim 1, wherein the twist coefficient of the polyester twist cord is 0.15 or more and 0.60 or less. 8. The polyester resin constituting the polyester twisted cord is polyethylene naphthalate and / or polyethylene naphthalate.
The tire according to any one of claims 1 to 7, comprising 90% by weight or more of polyethylene terephthalate.