JP2001171314A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a pneumatic radial tire in road noise performance. SOLUTION: The end portion YS of a band layer 9 is provided with an edge band ply 11A forming a different level D having the increased number of plies compared with the center portion YC. A shoulder region TS is provided on a crown region TC via a folded point P in the border line T of the belt ply 7A having the maximum width of a belt layer 7. The point P is positioned within a range of 15 mm inside and outside in the tire axial direction of the difference D. An angle α is made 3 deg.-11 deg. which is formed of the normals of the region TC at the point P and the region TS.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic radial tire with improved road noise performance.

[0002]

2. Description of the Related Art In a pneumatic radial tire, band cords are arranged in the tire circumferential direction outside a belt layer a as schematically shown in FIGS. 7A to 7C. The one provided with the band layer b is widely known.

As the band layer b, a structure using one edge band ply b1 that covers only the outer end portion of the belt layer a (sometimes referred to as 1E structure) and two edge band plies b1 are overlapped. A structure (sometimes referred to as 2E structure) or a structure in which one edge band ply b1 and a full band ply b2 covering the entire belt layer a are overlapped (sometimes referred to as an E + F structure) are generally used. .

The band layer b not only improves the high-speed durability performance by increasing the restraining force on the belt layer a, but also changes the vibration transmission characteristics due to the increase in tread rigidity, and reduces the peak of the vibration transmission rate to a higher frequency. It has the advantage of improving the road noise performance by causing a deviation from the peak of the vehicle's vibration transmissibility such as shifting to the side.

However, with the recent improvement in quietness of vehicles, there is a strong demand for further reduction of noise caused by tires, especially road noise.

Accordingly, the present invention is to provide a belt layer having a bending point at which each region bends between the crown region and the shoulder region of the belt layer in combination with the band layer. It is an object of the present invention to provide a pneumatic radial tire capable of further improving vibration transmission characteristics of a tire, reducing the input of vibration to the tire itself, and further improving road noise performance by a synergistic effect of these.

[0007]

In order to achieve the above object, according to the present invention, there is provided a carcass extending from a tread portion to a sidewall portion to a bead core of a bead portion,
1 arranged inside the tread portion and outside the carcass
A pneumatic radial tire including a belt layer including at least one belt ply and a band layer disposed outside the belt layer, wherein the band layer has an angle of 5 degrees or less with respect to the tire circumferential direction. It consists of a band ply that is tilted and a band cord made of an organic fiber cord is aligned,
In addition to providing a small width edge band ply at the end portion to form a step by increasing the number of band plies as compared to the center portion including the tire equator, at the tire meridian section of the maximum width belt ply of the belt layer The outer contour line is a crown region having a radius of curvature R1 from 300 mm to 面 mm where the tread surface extending outward from the tire equator is convex, or a radius of curvature R1 from 凹 700 mm to -∞mm concave and the tire axial direction. A shoulder region provided on the outside via a bending point, and the bending point is located within a range of 15 mm inside and outside the step in the tire axial direction, and the crown region at the bending point And the normal to the contour of the shoulder region is formed at an angle α of 3 ° to 11 °.

According to the second aspect of the present invention, the ratio R of the radius of curvature R2a of the contour of the shoulder region to the radius of curvature R1a of the contour of the crown region at the bending point.
2a / R1a is set to 0 to 0.40.

According to the third aspect of the present invention, the ratio R2a /
R1a is characterized by being 0.16 to 0.30.

According to a fourth aspect of the present invention, the band cord has an elongation of 10% or less when a load of 0.0236 g / dtex is applied.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a meridional section in a standard state in which a pneumatic radial tire 1 (hereinafter referred to as a tire 1) of the present invention is formed as a flat tire for a passenger car, and is mounted on a regular rim and filled with a regular internal pressure. I have.

The "regular rim" is a rim defined for each tire in a standard system including the standard on which the tire is based. For example, a standard rim for JATMA and a "Design Rim" for TRA Or ETRTO
Then it means "Measuring Rim". The “regular internal pressure” is an air pressure determined for each tire according to the above standard.
Then "TIRE LOADLIMITS AT VARIOUS COLD INFLAT
ION PRESSURES ", maximum value for ETRTO
It is "INFLATION PRESSURE", and is 180 (kPa) when the tire is for a passenger car.

In the figure, a tire 1 has a tread 2
And a pair of sidewall portions 3 extending inward in the tire radial direction from both sides thereof, and a bead portion 4 located at an inner end of each sidewall portion 3. The tire 1 also includes a toroidal carcass 6 extending between the bead portions 4 and 4, a belt layer 7 disposed inside the tread portion 2 and outside the carcass 6, and further outside the belt layer 7. And a band layer 9 disposed on the substrate.

The tread portion 2 has a rib type, rib lug type or block which divides the tread surface 2S into a plurality of rows of ribs J or blocks K by at least two vertical main grooves M extending along the tire circumferential direction. A tread pattern of the type is formed.

The carcass 6 is formed of one or more carcass plies 6A in which carcass cords are arranged at an angle of 75 ° to 90 ° with respect to the tire circumferential direction, in this example, one carcass ply 6A. As the carcass cord, an organic fiber cord such as nylon, polyester, rayon, or aromatic polyamide is preferably employed, but a steel cord may be employed according to the size, category, or requirement of the tire.

The carcass 6 is locked on both sides of 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 by being turned around from the bead core 5 from inside to outside. It has a folded portion 6b to be formed. A bead apex rubber 8 extending from the bead core 5 to the outside in the tire radial direction in a tapered shape is disposed between the main body 6a and the folded portion 6b. In this example, the turn-back portion 6b is formed at a bead base line B at the outer end in the radial direction.
The height from L is higher than the height of the radially outer end of the bead apex rubber 8 to form a so-called high turn-up structure, which cooperates with the bead apex rubber 8 to reinforce the bead portion 4 and reduce the tire lateral rigidity. Is increasing. When the carcass 6 is formed by a plurality of plies, it is preferable that at least one ply has a high turn-up structure.

The belt layer 7 includes one or more belt cords 7U, 7 in which highly elastic belt cords are arranged at an angle of 10 ° to 35 ° with respect to the tire circumferential direction.
L. The belt plies 7U and 7L are arranged in different directions so that the belt cords cross each other between the plies, thereby increasing the belt rigidity by the triangle structure of the cords, and having the tag width substantially equal to the entire width of the tread portion 2. And reinforce. As the belt cord, a steel cord or a highly elastic fiber cord having a strength close to that of steel, such as an aromatic polyamide fiber or an aromatic polyester fiber, is preferably used.

In the present embodiment, the inner belt ply 7L is formed to be slightly wider than the outer belt ply 7U in order to reduce the concentration of stress acting on the outer end of the belt. Is the belt ply 7A having the maximum width.

Next, the band layer 9 is inclined at an angle of not more than 5 degrees with respect to the tire circumferential direction, and the band ply 11 in which the band cord 10 made of an organic fiber cord is aligned.
Consists of

The band layer 9 is formed of a small-width edge band ply 11 that forms a step D by increasing the number of band plies 11 as compared with the central portion YC including the tire equator C.
A is provided in the end portion YS. That is, the band layer 9 corresponds to FIG.
As schematically shown in (A) to (C), the 1E structure using one of the edge band plies 11A, the 2E structure in which two of the edge band plies 11A are overlapped, or one of the edge band plies 11A An E + F structure or the like in which the belt layer 7 and the full band ply 11B covering the entire belt layer 7 overlap may be employed.

In any case, the edge band ply 11
At the inner end in the tire axial direction of A, a step D is formed in which the number of band plies 11 increases as compared with the central portion YC.
When the step D is located below the groove bottom of the vertical main groove M, crack damage tends to occur at the groove bottom due to stress concentration. Therefore, for durability, the distance L1 between the step D and the bottom edge of the groove in the tire axial direction should be 5 mm or more, and more preferably 10 mm.
It is preferable to secure the above.

FIGS. 1 and 3 show a band layer 9 having an E + F structure.
In this example, the band ply 11 is formed by spirally winding a narrow band ply 12 (shown in FIG. 6) in which one or more band cords 10 are arranged in the tire circumferential direction. It is formed by doing.

The band-like ply 12 has a band cord 10
Is formed into a small ribbon with the parallel cords covered with topping rubber. At this time, the number of band cords 10 in the band ply 12 is preferably about 5 to 15,
If the amount is too small, the efficiency of forming the ply decreases, and if it is too large, the cord angle of the band cord becomes excessively large and the binding force is reduced, so that the function as the band layer 9 cannot be sufficiently exhibited.

The band-like ply 12 is formed into a band ply 11 in which the band cords 10 are arranged at a substantially constant pitch P by spirally winding the side edges 12e against each other. As the band cord 10, an organic fiber cord such as nylon, polyester, rayon, or aromatic polyamide can be used.

In the present application, as shown in FIG. 3, in the tire standard state, the outer contour line T in the meridian section of the belt ply 7A having the maximum width is a crown area TC extending from the tire equator C and the tire area. A shoulder region TS is provided on the outside in the axial direction via a bending point P, and the bending point P is located within a range of 15 mm inside and outside the step D in the tire axial direction. Have one.

At this time, similarly to the conventional tire, the belt layer 7 needs to appropriately reinforce the tread portion 2 with a hoop effect, and therefore, the tread surface 2S becomes convex outward. In the case of a normal tire, the radius of curvature R1 of the crown region TC on the contour line T is from 300 mm to ∞.
mm range. For example, in the case of a super-flat tire having a concave tread surface 2S, the curvature radius R1 is -70.
The range is 0 mm to -∞ mm. The curvature radius R1 of ∞ mm and -∞ mm means a straight line.

It is not necessary that the entire crown region TC be formed by the curve having the radius of curvature R1. However, the radius of curvature R1 of the range described above may be at least 60% or more around the tire equator C. have. The main portion can be formed by a single arc or two or more arcs, and the radius of curvature R1 of each arc is set in the above range.

As described above, the belt layer 7 is bent with the bending point P between the crown region TC and the shoulder region TS, and the shoulder region TS is strongly restrained by the band layer 9 having a larger number of sheets. Have been.

Accordingly, the circumferential rigidity of the belt layer 7 is greatly increased, and the vibration transmission characteristic changes in a direction in which the peak of the vibration transmission coefficient of the tire shifts to a higher frequency side. The gap between them is even greater. In addition, since the ground pressure on the shoulder region TS side is reduced due to the bending of the belt layer 7, of the vibration input received from the road surface, the input itself to the outer end portion of the belt that easily transmits the vibration is reduced. As a result, the road noise performance can be effectively improved by these synergistic effects.

Here, in order to exhibit the effect of improving the road noise performance, as shown schematically in FIG. 4, a normal line to the contour line T of the crown region TC at the bending point P, and a shoulder region TS Is required to be in a range of 3 ° to 11 °. If it is less than 3 °, the above-mentioned improvement effect is not exhibited. Conversely, if it exceeds 11 °, the deformation stress of the belt layer 7 is concentrated at the bending point P, so that the durability is reduced. Therefore, preferably, the angle α is in the range of 5 ° to 9 °.

In order to improve the circumferential rigidity of the belt layer 7, the shoulder region TS with respect to the curvature radius R1a of the contour line T of the crown region TC at the bending point P is set.
The ratio R2a / R1a of the radius of curvature R2a of the contour line T
It is also important to set it to 0.40. That is, this ratio R2a
As the value of / R1a is smaller, the rigidity in the circumferential direction tends to increase. Therefore, if it exceeds 0.4, the effect of improving the road noise performance cannot be sufficiently exhibited. However, on the other hand, as the ratio R2a / R1a approaches 0, the ground pressure increases on the shoulder side, so that the vibration input at the outer end of the belt increases, and similarly, the effect of improving the road noise performance cannot be sufficiently exhibited. . Therefore, preferably, R2a /
R1a ranges from 0.16 to 0.30.

In order for the bending of the belt layer 7 to function effectively, it is desirable that the bending point P is not located below the groove bottom of the vertical main groove M. In particular, the bending point P and the groove bottom edge Is preferably 10 mm or more in the tire axial direction. Furthermore, the rib J or the block K above the bending point P
Preferably, no circumferential siping is provided.

Next, the belt layer 7 having the bending point P
Can be formed by utilizing the stretch of a tire in a vulcanization mold at the time of vulcanization molding.

That is, in the band layer 9, since the number of the band plies 11 is different between the center portion YC and the end portion YS, the restraining force exerted on the belt layer 7 is also different. Therefore, the belt layer 7 on the side of the central portion YC, which has a weak binding force, moves largely outward in the radial direction as compared with the side of the end portion YS, and as a result, it is bent.

At this time, the stretch at the time of vulcanization molding, which is usually about 3%, is set larger than the conventional one, for example, 5% or more, or a cord material having a lower elongation than the conventional one is used as the band cord. is necessary. In any case, at the time of vulcanization molding, the stretch amount (movement amount in the radial direction) of the belt layer 7 can be largely different between the central portion YC and the end portion YS, and the belt layer 7 can be bent. Becomes

Therefore, the bending point P is formed in the vicinity of the step D, that is, within a range of 15 mm inside and outside the step D in the tire axial direction. When the position of the bending point P and the position of the step D coincide with each other, a rigid step may be generated. Therefore, it is preferable that the distance L3 between the bending point P and the step D be 5 mm or more.

In the means for setting the stretch to be large as described above, the deformation of the belt layer 7 and the like during vulcanization molding increases and the partial rubber flow also increases, so that the uniformity (uniformity) of the tire is reduced. This tends to cause a drop, which is disadvantageous to, for example, vibration characteristics.

Therefore, a means using a low elongation band cord 10 is preferable. At this time, a band cord having an elongation of 10% or less when a load of 0.0236 g / dtex is applied is used. Accordingly, the required binding force of the band layer 9 can be secured even in a stretch of about 3% while enabling the formation of a bend, and the above-described functions of the band layer 9 (improvement of high-speed durability performance, reduction of road noise, etc.) Can be effectively demonstrated.

The elongation of the conventional nylon band cord is about 14%. The elongation is JIS L10
This is a value measured according to No.17.

The band layer 9 is formed at the end portion YS of the belt layer 7.
In order to supplement and improve the rigidity on the side, the distance L4 of the step D from the outer end 7E of the belt ply 7A is set to be 1/12 to 3/12 times the ply width BW of the belt ply 7A, and further 1 / It is preferably 12 to 2/12 times.

The band layer 9 does not need to be interposed in the entire region from the step D to the outer end 7E, as shown in FIGS. 5A and 5B.
As shown in (1), one or both of the full band ply 11B and the edge band ply 11A may be terminated in the region. This can be expected to improve the rolling resistance. However, in order to obtain the necessary binding force by the band layer 9, it is preferable to secure the width W1 of the maximum layer portion where the number of plies of the band layer 9 is maximum to be 10 mm or more.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment, but may be modified in various forms.

[0043]

EXAMPLE A tire having a tire size of 195 / 60R15 and having a structure shown in FIG. 1 was prototyped based on the specifications in Tables 1 to 3, and the durability, road noise performance, and rolling performance of each test tire were tested. And compared. The test method is as follows.

(1) Durability: A test tire was driven on a drum at a speed of 100 km / h under a rim (15 × 6.5 JJ), an internal pressure (200 kPa) and a load (8.3 kN).
The separation of the belt layer after traveling for 200 km was visually inspected and confirmed, and the result was regarded as defective.

(2) Road noise performance: The test tire was mounted on a rim (15 × 6.5 JJ) at an internal pressure (210 kPa).
The vehicle was mounted on all wheels for passenger cars (1600 cc, FF vehicle), and was run on a smooth road surface at a speed of 50 km / h. The higher the value, the lower the noise level and the better.

(3) Rolling performance: Using a rolling resistance tester, test tires were mounted on a rim (15 × 6.5 JJ), an internal pressure (230 kPa), a load (4.0 kN), and a speed (80 kN).
m / h), the rolling resistance was measured, and the result was expressed as an index when Comparative Example 1 (conventional tire) was set to 100. The larger the index, the better.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

[0050]

As described above, the pneumatic tire of the present invention has the following features.
Combined with the band layer, the belt region forms a bending point between the crown region and the shoulder region of the belt layer where the belt region bends each other, thereby increasing the circumferential rigidity of the belt layer and further changing the vibration transmission characteristics of the tire. At the same time, the input of vibration to the tire itself is reduced, and the road noise performance can be further improved by the synergistic action of these.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention.

FIGS. 2A to 2C are diagrams schematically illustrating a structure of a band layer that can be suitably used in the present application.

FIG. 3 is an enlarged sectional view showing a belt layer together with a band layer.

FIG. 4 is a diagram illustrating a contour line of a belt layer.

FIGS. 5A and 5B are cross-sectional views showing another embodiment of the band layer.

FIG. 6 is a perspective view illustrating a band-like ply used for a band layer.

FIG. 7 is a schematic sectional view of a band layer for explaining a conventional technique.

[Explanation of symbols]

 2 Tread part 2S Tread surface 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 7A Maximum width belt ply 9 Band layer 10 Band cord 11 Band ply 11A Edge band ply C Tire equator D Step P Bending point T Contour Line TC Crown area TS Shoulder area YC Central part YS End part

Claims (4)

[Claims] 1. A carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, a belt layer including at least one belt ply disposed inside the tread portion and outside the carcass, and A pneumatic radial tire having a band layer disposed outside a layer, wherein the band layer is inclined at an angle of 5 degrees or less with respect to a tire circumferential direction and a band cord made of an organic fiber cord is aligned. A narrow edge band ply that forms a step by increasing the number of band plies as compared with a central portion including the tire equator at the end portion, and a belt ply having a maximum width of the belt layer. The outer contour line of the tire meridian section has a radius of curvature R1 extending from the tire equator and having a tread surface convex outward from 300 mm to ∞mm, or The tire has a crown region having a concave radius of curvature R1 of -700 mm to -∞ mm, and a shoulder region provided outside the tire axial direction via a bending point. 1 in and out in the axial direction
5 mm, and an angle α formed by a normal to the contour of the crown region at the bending point and a normal to the contour of the shoulder region is 3 ° to 11 °. Pneumatic radial tires. 2. The ratio R2a / R1a of the radius of curvature R2a of the contour of the shoulder region to the radius of curvature R1a of the contour of the crown region at the bending point is 0 to 0.4.
The pneumatic radial tire according to claim 1, wherein the tire is set to 0. 3. The ratio R2a / R1a is 0.16 to 0.3.
The pneumatic radial tire according to claim 2, wherein the tire is set to 0. 4. The band cord has a capacity of 0.0236 g / d.
4. The pneumatic radial tire according to claim 1, wherein an elongation percentage when a load of tex is applied is 10% or less.