JPH08276704A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE: To attain good uniformity, excellent cornering ability and high-speed durability by disposing an inclined belt layer and a circumferential belt layer in order on the outer periphery of the crown part of a carcass, and forming the inclined belt layer out of a particular cord. CONSTITUTION: An inclined belt layer 6 disposed on the outer periphery of the crown part of a carcass 3 together with a peripheral belt layer 7 in a radial tire is formed by jointing and arranging a band-shaped element where one or plural cords are covered with rubber in a zigzag form in the tire peripheral direction. The cord of the inclined belt layer 6 is an organic fiber cord consisting of polyethlene naphthalate, and twist coefficient Nt expressed by Nt=T×(0.139×DT/2×1/ρ)<1/2> ×10<-3> where T: count of twist (turn/10cm), DT: overall denier and ρ: specific gravity, is set within 0.10 to 0.50. Tangent loss, tanδ is set at 0.3 (max.), and cord diameter is set at 0.85mm (max.).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having good uniformity and excellent cornering property and high-speed durability, and more particularly to a passenger car tire and a light truck tire.

[0002]

2. Description of the Related Art At the present time when energy saving is called for, in automobiles, studies are being made to improve fuel efficiency by reducing weight, and accordingly, tires are also being reduced in weight. The demand is increasing year by year, and this tendency is particularly remarkable in pneumatic tires for passenger cars. Therefore, attempts have been made to change the cords used for tires from steel cords to organic fiber cords, but at present they have not reached the level of satisfying various tire performances.

Further, in the pneumatic tire, at least two inclined belt layers are laminated on the outer periphery of the crown portion of the carcass so that their steel cords cross each other.
It is common to have so-called cross belts.

However, the inclined belt layer is formed by obliquely cutting a cord rubber cloth into a predetermined width in accordance with the arrangement angle of the cord, and in this inclined belt layer, the cut portion of the cord is an end. Inevitably occurs in the department. This is not desirable from the viewpoint of durability and the like, because separation tends to occur at the end portion of the belt layer.

In order to prevent the cord from being cut at the end portion of the inclined belt layer, a belt-shaped body having one or a plurality of cords covered with rubber is continuously arranged in a zigzag pattern in the circumferential direction. And by arranging the bent portion of the zigzag-arranged strip at the widthwise end position of the inclined belt layer,
It is useful to form an inclined belt layer, which is disclosed in Japanese Utility Model Publication No. 48-96259 and Japanese Unexamined Patent Publication No. 4-274904.
And Japanese Patent Laid-Open No. 5-319017.

[0006]

In the tires described in these publications, although there is no cord cutting portion at the end of the inclined belt layer, for example, as shown in FIG. 3, a linear step 11 ( (Shown by a thick line) inevitably occurs, and in addition, a zigzag step 12 may also occur depending on the winding method. The zigzag step 12 is generated by the arrangement in which the strips intersect and overlap with each other, and the cords are constrained to each other, which has the advantage of improving the shear rigidity of the belt. The step 11 in the shape of
There was no particular advantage, but rather a major drawback was that it worsened the uniformity of the tire. This is a fatal drawback for a radial tire, and it was necessary to develop means for reducing the linear step 11. Further, from the viewpoint of weight reduction, it is desirable to use an organic fiber cord for the cord of the inclined belt layer, but a clear technique for applying the organic fiber cord to the cord of the inclined belt layer is disclosed. No literature found.

Therefore, an object of the present invention is to use an organic fiber cord made of polyethylene naphthalate for the cord of the inclined belt layer, and to optimize the structure, coefficient, tangent loss and cord diameter of this organic fiber cord. In view of the above, it is an object of the present invention to provide a pneumatic tire having good uniformity, excellent cornering properties and high-speed durability, in particular, a pneumatic tire for passenger cars and a pneumatic tire for small trucks.

[0008]

In order to achieve the above object, the present invention provides an inclined belt layer, a circumferential belt layer, on the outer circumference of a crown portion of a carcass that forms a toroidal shape across at least a pair of bead cores. And a pneumatic radial tire in which treads are sequentially arranged, the inclined belt layer is a belt-shaped body formed by coating one or more cords with a rubber, and the belts are continuously arranged in a zigzag shape in the tire circumferential direction, And,
It is formed by arranging the bent portion of this zigzag-arranged strip at the widthwise end position of the inclined belt layer, and the cord of the inclined belt layer is an organic fiber cord made of polyethylene naphthalate. Have this cord, the more number T (number / 10cm), the total denier D
Let _{T be} the specific gravity and ρ be the equation: N _t = T × (0.139 ×
D _T / 2 × 1 / ρ) ^1/2 × 10 ⁻³ , the coefficient N _t is more in the range of 0.10 to 0.50, and the tangent loss ta is
n δ is in the range of 0.3 or less under the conditions of initial tension of 1 kgf / piece, strain amplitude of 0.1%, frequency of 20 Hz, and ambient temperature of 25 ° C., and cord diameter of 0.85 mm or less. , The circumferential belt layer comprises at least one layer,
A pneumatic radial tire, which is located on an inclined belt layer, in which cords are spirally wound and arranged substantially in parallel to a tire equatorial plane.

When the belt covers the entire circumference of the tire with a predetermined width of the inclined belt layer as one set, the inclined belt layer is two sets, and the cord of the circumferential belt layer is polyethylene terephthalate ( It is more preferable that the organic fiber cord is made of PET), polyethylene naphthalate (PEN), or nylon, and that the bulk elastic modulus of the covering rubber of the inclined belt layer is 200 kgf / mm ² .

Here, the twisted structure means one thread or two threads.
It means that more than one book is added and twist is added (from the bottom), and two or more pieces are drawn and multiplied by the opposite (from the top). The total denier D _T is the product of the yarn denier and the number of twists.

FIG. 1 shows a widthwise cross section of a typical pneumatic tire for passenger cars according to the present invention. In the figure, 1 is a pneumatic tire, 2 is a bead core, 3 is a carcass, 4 is a crown portion of the carcass, and 6 is a carcass. Is an inclined belt layer, 7 is a circumferential belt layer, 9 is a widthwise edge of the inclined belt layer, and 10 is a tread. The pneumatic tire 1 includes an inclined belt layer 6, a circumferential belt layer 7, and an outer circumference of a crown portion 4 of a carcass 3 having a toroidal shape extending over at least a pair of bead cores 2.
And the tread 10 are sequentially arranged.

As shown in FIG. 3, the inclined belt layer 6 has a thickness of 1
A strip-shaped body 8 formed by coating a book or a plurality of cords with rubber,
It is formed by continuously arranging in a zigzag pattern in the tire circumferential direction 5 and arranging the bent portions 8a of the zigzag-arranged strips 8 at the width direction ends 9a and 9b of the inclined belt layer.
For example, as shown in FIG. 4 or FIG. 5, the inclined belt layer 6 includes a belt-shaped body 8 at a predetermined inclination angle from one widthwise end 9a or 9b toward the other widthwise end 9b or 9a. After winding, it is bent at this width direction end 9b or 9a (bending angle α), and then wound from the other width direction end 9b or 9a toward one width direction end 9a or 9b to be arranged in a zigzag shape. Then, this is repeatedly formed, and specifically, per N (integer) revolutions of the tire, a total of M (integer) bends are alternately performed at the width direction ends 9a and 9b, so that the tire is first wound. The inclined belt layer 6 is formed by determining the circumferential pitch for shifting the strip-shaped body to the front or rear such that the strip-shaped body and the strip-shaped body to be wound next are arranged at a predetermined interval. In FIG. 5, starting from position 13,
The width direction end 9 of the inclined belt layer 6 during N times of tire rotation.
It shows a state in which the belt-shaped body has reached the adjacent position 14 of the starting point 13 after bending a total of M times at a and 9b. By this method, without creating a gap between adjacent strips,
It becomes possible to arrange the strips at an almost desired inclination angle. The inclined belt layer 6 obtained by this method has zigzag steps 12 as shown in FIG. That is, in the inclined belt layer 6 shown in FIG. 3, the cords are constrained to each other by the belt-shaped bodies 8 intersecting and overlapping each other. Therefore, as compared with the inclined belt layer shown in FIG. The rigidity can be improved.

The cord of the inclined belt layer 6 is made of PEN.
It is an organic fiber cord made of and has a twisted structure. The twist coefficient N _t of the cord of the inclined belt layer 6 is 0.1.
The range is from 0 to 0.50. If it is less than 0.10, the code tends to come apart and workability tends to deteriorate,
Further, in order to secure the rigidity of the cord, it is necessary to set it to 0.50 or less.

Tangent loss tan δ of the cord of the inclined belt layer 6
Is an initial tension of 1 kgf / piece, strain amplitude 0.1%, frequency 20
The range is 0.3 or less under the conditions of Hz and ambient temperature of 25 ° C. Since the organic fiber cord has a large work loss and is apt to generate heat, it is apt to generate heat and melt during high-speed traveling, which may eventually lead to a tire burst. This is because it must be within the following range. In addition, the covering rubber of the inclined belt layer 6 preferably has a bulk modulus of 200 kgf / mm ² or more when it is necessary to further suppress the local movement of the cord.

In order to reduce the linear step 11 of the inclined belt layer 6, the cord diameter of the inclined belt layer 6 is 0.85.
The range is less than or equal to mm.

In the case of tires for passenger cars, the number of layers of the inclined belt layer 6 is preferably a small number from the viewpoint of weight reduction, while on the other hand,
In the case of a light truck tire, the tire internal pressure is often almost twice as high as that of a passenger car tire. Therefore, from the viewpoint of maintaining strength, as shown in FIG.
Although it is preferable to use sets, the number of sets of the inclined belt layers can be increased as necessary in both cases. The inclination angle of the cord of the inclined belt layer 6 is preferably in the range of 15 ° to 45 ° with respect to the equatorial plane of the tire, and is preferably 15 ° to 30 ° considering the ease of production.

The circumferential belt layer 7 is composed of at least one layer, is located on the inclined belt layer 6, and the cords are spirally wound to be arranged substantially parallel to the equatorial plane of the tire.

The number of circumferential belt layers 7 is preferably about 1 to 2 from the viewpoint of weight reduction. Further, when it is necessary to effectively suppress the protrusion of the crown center portion during high-speed traveling, the circumferential belt layer preferably has two layers in the crown center portion and one layer in the remaining crown portion. When it is necessary to effectively suppress the belt edge separation, the circumferential belt layer 7 has a crown edge portion of 2 mm.
It is preferable that the layer and the remaining crown portion are made into one layer, which can be appropriately selected according to the application. The cord of the circumferential belt layer 7 is preferably an organic fiber cord made of PET, PEN, or nylon, which is excellent in compression fatigue resistance. Further, the tangent loss tan δ of the cord is preferably 0.3 or less for the same reason as the cord of the inclined belt layer.

The carcass 3 has a PET cord as its ply cord.
It is preferable to use an organic fiber cord such as the above, and to arrange the cord at an angle of 70 to 90 ° with respect to the equatorial plane of the tire.

[0020]

In the pneumatic tire of the present invention, the stepped circumferential belt layer 7 is placed on the tilted belt layer 6 and the diameter of the cord of the tilted belt layer 6 is reduced so that the tilted belt layer 6 is stepped. Can be most easily and substantially reduced, thus improving the uniformity of the tire.

Further, the widthwise end portions 9a of the inclined belt layer 6 are
Unlike the conventional sheet-shaped inclined belt layer, the cord is not cut at 9b, so that the separation at the belt end is reduced, and thus the high-speed durability is improved. Further, an organic fiber cord made of PEN is used for the cord of the inclined belt layer 6, and in particular, by making the coefficient of the organic fiber cord within an appropriate range, it is possible to reduce the weight of the tire and enhance the rigidity of the cord. Therefore, the cornering power is increased and the cornering property is improved.

In addition, by setting the tangent loss of the cord of the inclined belt layer 6 within the range of 0.3 or less under a predetermined condition, it is possible to prevent the cord from melting due to self-heating. Further, particularly in the case of a small truck tire, by providing the inclined belt layers 6 in two sets, a tire strength sufficient to withstand the high internal pressure of the tire can be obtained.
If the bulk elastic modulus of the covering rubber of the inclined belt layer 6 is too low, the cord is likely to move, local buckling of the cord is likely to occur, and the cord may be broken. Furthermore, by using an organic fiber cord made of PET, PEN, or nylon having good compression fatigue resistance for the cord of the circumferential belt layer 7, the compression fracture due to the belt buckling deformation that tends to occur during severe cornering. Can be suppressed.

[0023]

EXAMPLES Specific examples of passenger car tires and light truck tires according to the present invention will now be described with reference to the drawings. (1) Tires for passenger cars The pneumatic tires used in Examples 1 to 6 have a cross section in the width direction shown in FIG. 1 and have a tire size of 195 / 65R14.
The inclined belt layer 6, the circumferential belt layer 7, and the tread 10 are sequentially arranged on the outer circumference of the crown portion 4 of the carcass 3 that forms a toroidal shape across the pair of bead cores 2. Inclined belt layer 6 and circumferential belt layer 7
Are both one set, and the material, the structure, the coefficient, the tangent loss, the cord angle, the cord diameter, and the presence / absence of the circumferential belt layer 7 of the cord of the inclined belt layer 6, the cord, the material, the structure Are summarized in Table 1.
The volume modulus of the coating rubber of the inclined belt layer, Examples 1 to 5 is 280 kgf / mm ^2, Example 6 was 180 kgf / mm ^2. The inclined belt layer 6 has a planar shape shown in FIG.
As shown in FIG. 5, M = 9 and N = 4, that is, a value close to the circumferential pitch f = 9/4 was formed. The circumferential belt layer 7 is formed by helically winding the cords and arranged the cords at an angle of approximately 0 ° with respect to the tire equatorial plane. The circumferential belt layer 7 has a width of 130 mm and the inclined belt layer 6 is formed. Has a width of 140 mm.

[0024]

[Table 1]

The pneumatic tires used in Comparative Examples 1 and 2 did not have a circumferential belt layer, and the pneumatic tires used in Comparative Examples 3 to 7 had the widthwise cross section shown in FIG. At least one of the coefficient, the tangent loss, and the cord diameter of the inclined belt layer is out of the appropriate range. The bulk elastic modulus of the covering rubber of the inclined belt layer is 280 kg in each case.
It was f / mm ² .

The pneumatic tire used in Conventional Example 1 extends at an angle of ± 22 ° with respect to the tire equatorial plane 5 and has two layers in which a plurality of steel cords having a cord structure of 1 × 5 × 0.23 are arranged. The inclined belt layers 6 are cross-laminated and the circumferential belt layers 7 are not provided.

(2) Tires for light trucks The pneumatic tires used in Examples 7 to 9 have a cross section in the width direction shown in FIG. 2 and have a tire size of 195 / 85R16.
12PR, and the inclined belt layer 6, the circumferential belt layer 7, and the tread 10 are sequentially arranged on the outer circumference of the crown portion 4 of the carcass 3 that forms a toroidal shape across the pair of bead cores 2. The inclined belt layer 6 has two sets, and the circumferential belt layer 7 has one set. The cord of the inclined belt layer 6 has a material, a structure, a coefficient, a tangent loss, a cord angle, a cord diameter, and a circumferential belt layer 7. Presence, code,
The materials and structures are summarized in Table 2.
The bulk elastic modulus of the covering rubber of the inclined belt layer was 320 kgf / mm ² . The inclined belt layer 6 has a plane shape shown in FIG. 3, and according to the place shown in FIG. 5, M =
9 and N = 4, that is, a value close to the circumferential pitch f = 9/4. The circumferential belt layer 7 is formed by spirally winding the cords and arranging the cords at an angle of approximately 0 ° with respect to the tire equatorial plane. The width of the circumferential belt layer 7 is 100 mm, and the inclined belt layer 6 is formed. Width of the upper layer is 110
mm and the lower layer was 125 mm.

[0028]

[Table 2]

The pneumatic tire used in Comparative Example 8 does not have a circumferential belt layer, and the pneumatic tires used in Comparative Examples 9 to 11 have a cross section in the width direction shown in FIG. At least one of the coefficient, the tangent loss, and the cord diameter of the belt layer is out of the proper range. The bulk elastic modulus of the covering rubber of the inclined belt layer is 320
It was set to kgf / mm ² .

The pneumatic tire used in Conventional Example 2 extends at an angle of 52 ° with respect to the tire equatorial plane 5 and has one layer of a plurality of steel cords arranged with a cord structure of 1 × 3 × 0.30. A tilted belt layer 6 consisting of a total of three layers of two cross-laminated layers in which a plurality of steel cords having a cord structure of 1 + 6 × 0.28 is arranged, is arranged at an angle of ± 17 ° with respect to the tire equatorial plane 5. However, the circumferential belt layer 7 is not provided.

(Test Method) With respect to each of the above-mentioned test tires, tests for evaluating uniformity, cornering property, and high-speed durability were separately conducted for a passenger car tire and a light truck tire. The tire weight of passenger car tires was also measured.

(1) Uniformity test A tire filled with a specified internal pressure is pressed onto a drum with a specified load, and the drum is rotated so that the tire rotates 60 times per minute. The unbalance amount of the force in the direction and the longitudinal direction was measured to evaluate the uniformity. The test results of passenger car tires and light truck tires are shown in Tables 3 and 4, respectively. In addition, the numerical values of uniformity in Table 3 are the same as those of the conventional example 1.
Is shown as an index ratio, and the numerical value of uniformity in Table 4 is shown as an index ratio with Conventional Example 2 as 100. In any case, the smaller the value, the better.

(2) Cornering test The cornering property was evaluated by determining the cornering power. For measuring cornering power, the outer diameter is 3
Set a test tire adjusted to the maximum internal pressure specified in JATMA or JIS on a drum of 000 mm, and apply a load specified in JATMA or JIS to the tire from the above tire size and internal pressure, and then 30 km / h At a speed of 30 minutes for preliminary running, readjusting the internal pressure to the above without load, and applying a load for preliminary running again, and a maximum slip angle of 8 degrees (deg.) On the drum at the same speed.
The positive and negative are continuously applied. The cornering force (CF) at each positive and negative angle is measured, and the formula: CP (kgf / deg.) = [CF (1 deg.) + CF (2 deg.) / 2
The cornering power (CP value) was calculated by + CF (3deg.) / 3 + CF (4deg.) / 4] / 4. The test results of passenger car tires and light truck tires are shown in Tables 3 and 4, respectively. The cornering values in Table 3 are shown as an index ratio with Conventional Example 1 as 100, and the cornering values in Table 4 are those in Conventional Example 2
Is shown as an index ratio with 100 being set, and in each case,
The higher the number, the better.

(3) High-speed durability test The high-speed durability was measured according to the US standard FMVSS No. The test was performed by the step speed method according to the test method of 109, that is, the test was performed every 30 minutes at increasing speed until failure, and the speed (km / h) at the time of failure was measured and evaluated. The test results of passenger car tires and light truck tires are shown in Tables 3 and 4, respectively. The numerical values of high-speed durability in Table 3 are shown as index ratios with the value of Conventional Example 1 being 100, and the numerical values of high-speed durability in Table 4 are with index ratio of Conventional Example 2 being 100. Is shown,
In any case, the larger the number, the better. Also,
At this time, it is also investigated whether or not the code is melted. If it is melted, "Yes" is given, and if it is not melted, "No" is given in Table 3 and Table 4, respectively. There is.

[0035]

[Table 3]

[0036]

[Table 4]

From the test results shown in Table 3, the passenger car tires of Examples 1 to 6 are significantly lighter than the passenger car tires of Conventional Example 1, and further, uniformity, cornering property and high speed are achieved. The overall durability performance was equal to or higher than that of Conventional Example 1. In addition, from the test results of Table 4, the small truck tires of Examples 7 to 9 are superior to the small truck tire of Conventional Example 2 in terms of uniformity, cornering property, and high-speed durability.

[0038]

According to the present invention, it is possible to provide a pneumatic tire for passenger cars and a pneumatic tire for small trucks, which have good uniformity, excellent cornering property, and high-speed durability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in the width direction of a typical pneumatic tire for passenger cars according to the present invention.

FIG. 2 is a widthwise sectional view of a typical pneumatic tire for a light truck according to the present invention.

FIG. 3 is a plan view showing a part of an inclined belt layer for showing a linear step 11.

FIG. 4 is a diagram showing a method for forming an inclined belt layer.

FIG. 5 is a diagram showing a method of forming an inclined belt layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead core 3 Carcass 4 Carcass crown portion 5 Tire circumferential direction 6 Tilt belt layer 7 Circumferential belt layer 8 Band-like body 9 Width end of tilt belt layer 10 Tread 11 Linear step 12 Zigzag step 13 Starting point 14 Adjacent position of the starting point 13 15 Cord of the inclined belt layer 6

Claims (4)

[Claims] 1. A pneumatic radial tire in which an inclined belt layer, a circumferential belt layer, and a tread are sequentially arranged on the outer circumference of a toroidal carcass crown portion that straddles at least a pair of bead cores. The inclined belt layer is formed by continuously arranging a band-shaped body formed by coating one or more cords with rubber in a zigzag shape in the tire circumferential direction, and bending the bent portion of the zigzag-arranged belt-shaped body into the inclined belt layer. The cord of the inclined belt layer is an organic fiber cord made of polyethylene naphthalate and has a twisted structure, and the cord of the cord has a twist number T (number of times). / 10 cm), the total denier is D _T , and the specific gravity is ρ, the formula: N _t = T × (0.139 × D _T / 2 × 1 / ρ) ^1/2
The coefficient N _t represented by × 10 ⁻³ is 0.10 to 0.
The tangent loss tan δ is within the range of 50 and the initial tension is 1 kgf.
/ Book, strain amplitude 0.1%, frequency 20Hz, ambient temperature 2
Under the condition of 5 ° C., the range is 0.3 or less, and the cord diameter is 0.85 mm or less. The circumferential belt layer is composed of at least one layer and is located on the inclined belt layer. A pneumatic radial tire, which is obtained by spirally winding and arranging in a manner substantially parallel to the equatorial plane of the tire. 2. The pneumatic radial tire according to claim 1, wherein two sets of inclined belt layers are provided when one set includes a belt-shaped body covering the entire circumference of the tire with a predetermined width of the inclined belt layer. 3. The pneumatic radial tire according to claim 1, wherein the cord of the circumferential belt layer is an organic fiber cord made of polyethylene terephthalate, polyethylene naphthalate, or nylon. 4. The pneumatic radial tire according to claim 1, wherein the volumetric elastic modulus of the rubber covered with the inclined belt layer is 200 kgf / mm ² or more.