JP2001121917A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the whole thickness of a tread while maintaining durability and improve rolling performance and noise resistance. SOLUTION: A band layer 9 is composed of a band ply 12 for which a strip ply 11 is spirally wound with band cords 10 in alignment. An overlapped area K where a plurality of band plies 12 are overlapped with each other in the radial direction is formed at least outer end of a belt layer 7. A falling portion 13 is formed between band cords 10E of one band ply 12E, neighboring each other inside/outside the overlapped area K, in which band cords 10F of the other band ply 12F falls. A cord-to-cord thickness TD in the overlapped area K is smaller than a total value Σs for the diameter S of the band cord 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having improved rolling performance and noise performance while maintaining required durability.

[0002]

2. Description of the Related Art A pneumatic radial tire has a structure in which a band layer b formed by spirally winding a band cord is provided outside a belt layer a as schematically shown in FIG. Are widely known. The band layer b improves the high-speed durability performance by increasing the binding force to the belt layer a, and also improves the steering stability by increasing the tread rigidity. Further, the vibration transmission characteristic changes due to the increase in the tread rigidity. In addition, there is an advantage that the peak of the vibration transmissivity shifts to a higher frequency side and a deviation from the peak of the vibration transmissibility of the vehicle is caused to reduce road noise.

[0003] On the other hand, in a tire, the tread rubber g is required to suppress cracks in the tread rubber g and maintain durability.
The thickness of the rubber gauge t1 at the bottom of the groove is minimum (usually 1.
(About 5 mm). Therefore, when the band layer b is formed, the total tread thickness t0 increases at least by the thickness t2 of the band layer b.

For example, in the band layer b, since a stronger binding force is required on the outer end side of the belt layer, a full band ply b1 that covers the entire belt layer a and an edge band ply that covers only the outer end of the belt layer b2 and a structure (F
+ E structure) is often used. However, even in such a structure, it is necessary to increase the rubber gauge thickness t3 corresponding to the thickness of the edge band ply b2 between the edge band plies b2, b2 in order to prevent deterioration of the ground pressure distribution. That is, even when the edge band ply b2 is partially arranged, an increase in the total tread thickness t0 is caused over the entire width.

[0005] As a result, in addition to increasing the weight of the tire,
There is a problem that the rolling performance is reduced.
Therefore, in order to solve this problem, it is important to keep the maximum thickness of the band layer, that is, the thickness of the band layer in a region where a plurality of band plies overlap, as small as possible.

A band layer having an effect equivalent to the F + E structure without using the edge band ply b2 has a structure in which the material of the band cord is different between the center of the tread and the side of the tread shoulder.
As described in Japanese Patent No. 34403 or the like, a structure has been proposed in which the spiral pitch of the band cord is different between the tread center side and the tread shoulder side. But the former structure is
The types of band cord materials increase and the process becomes complicated,
This leads to an increase in costs such as the necessity of adding a molding machine function. In addition, in the latter structure, in addition to the complexity of the process, the cord angle in the coarse spiral pitch portion becomes large, so that high-speed running performance may be deteriorated.

[0007] Therefore, the present invention is based on reducing the thickness in the overlapping area by dropping the band cord of the other band ply between the band cords of one overlapping band ply in the band layer to reduce the required durability. It is an object of the present invention to provide a pneumatic radial tire capable of suppressing the total thickness of the tread while maintaining the performance and improving the rolling performance and the noise performance.

[0008]

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,
A belt layer disposed inside the tread portion and outside the carcass, and a pneumatic radial tire including a band layer disposed outside the belt layer, wherein the band layer includes:
A band ply formed by spirally winding a narrow band ply in which one or more band cords are aligned in the tire circumferential direction, and a plurality of bands at least at the outer end of the belt layer. By forming overlapping regions in which the plies are overlapped in the radial direction and by equalizing the direction and the inclination angle of the band cord of each band ply in the overlapping region with respect to the tire circumferential direction, one of the adjacent band plies inside and outside is formed. By forming a recessed portion in which the band code of the other band ply falls between the band codes, the thickness TD between the cords sandwiching the band codes of all the band plies in the overlapping area is set to the thickness TD of each band code of each band ply. It is characterized in that it is smaller than the total value ΔS of the diameters S.

In the invention of claim 2, the inter-cord thickness TD is 0.55 to 0.90 times the total value ΔS.

[0010] In the invention according to claim 3, the band cord has an elongation of 10% or less when a load of 0.0236 g / dtex is applied.

According to the present invention, the belt layer has a belt camber amount BC, which is a radial distance between a tire equator point and an outer end point of the belt on the inner surface of the belt layer, with respect to the tire section height H. It is characterized in that the ratio BC / H is in the range of the following equation (1). BC / H ≦ 0.24-A × 0.23 (1) In the equation, A is the flatness of the tire.

According to a fifth aspect of the present invention, the belt layer has a stretch at the time of vulcanization of less than 3%.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a meridional section when a pneumatic radial tire 1 (hereinafter referred to as a tire 1) of the present invention is formed as a tire for a passenger car. The tire 1 has a tread portion 2 and a tire radial direction from both sides thereof. It has a pair of sidewall portions 3 extending inward, and a bead portion 4 located at an inner end of each sidewall portion 3.

The tire 1 has a toroidal carcass 6 extending between the bead portions 4, a belt layer 7 disposed inside the tread portion 2 and outside the carcass 6, and a belt layer 7. And a band layer 9 disposed further outside the.

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 bead base line BL is a bead bottom 4
S is a line in the tire axial direction passing through the outer end point in the tire axial direction of S, and serves as a criterion for selecting the rim diameter of the applicable rim.

The belt layer 7 is composed of two or more belt ply members 7 in which highly elastic belt cords are arranged at an angle of 10 ° to 35 ° with respect to the tire circumferential direction.
A, 7B. Each belt ply 7A, 7B
The belt cords are arranged in different directions so as to intersect with each other between the plies, thereby increasing the belt rigidity by the triangle structure of the cords, and reinforcing substantially the entire width of the tread portion 2 with a tag effect. 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 this embodiment, the inner belt ply 7A is formed to be slightly wider than the outer belt ply 7B, so that the concentration of stress acting on the outer end of the belt is reduced.

Next, the band layer 9 is formed of a narrow band-like ply 11 (FIG. 2) in which one or more band cords 10 are aligned.
The belt layer 7 is formed by spirally winding the belt layer 7 in the tire circumferential direction.
At least at the outer end of the band ply 1
2 are overlapped in the radial direction to form an overlapping area K.

Specifically, in this embodiment, the band layer 9 includes a full band ply 12F covering the entire width of the belt layer 7,
It has an edge band ply 12E covering the outer end of the belt layer 7, and has a so-called F + E structure in which the restraining force on the outer end side of the belt layer 7 is increased as compared with the central side (tire equator side). Therefore, in the band layer 9 of the present example, the full band ply 12F and the edge band ply 12E form an overlapping region K in which the two band plies 12 overlap in the radial direction. In this example, the case where the edge band ply 12E is disposed radially inside the full band ply 12F is illustrated, but the edge band ply 12E may be disposed radially outside.

The "outer end of the belt layer 7" includes a range of at least 15 mm inward in the tire axial direction from the outer end of the belt layer 7 corresponding to the outer end of the wide belt ply.

As shown in FIG. 2, the band-like ply 11
In this example, one or more band cords 10 are arranged in a narrow ribbon shape in which a parallel cord body in which a plurality of band cords 10 are aligned is covered with topping rubber. At this time, the number of band cords 10 in the band-like ply 11 is preferably about 5 to 15, and if it is too small, the ply forming efficiency is reduced. And the function as the band layer 9 cannot be sufficiently exhibited. The cord angle of the band cord with respect to the tire circumferential direction is generally 5 ° or less.

The band-like ply 11 is formed by spirally winding the side edges 11e against each other to form a full band ply 12F and an edge band ply 12E in which the band cords 10 are arranged at a substantially constant pitch P. Form. The band cord 10 is made of nylon,
Organic fiber cords such as polyester, rayon and aromatic polyamide can be used. In this example, the case where the same band cord 10 is used for both the full band ply 12F and the edge band ply 12E is illustrated.
For convenience, the band code of the full band ply 12F is 10F, and the band code of the edge band ply 12E is 1
It may be distinguished as 0E.

In the present application, the band layer 9 is formed as shown in FIG.
As shown in FIG. 5, one band ply 12 (in this example, an edge band ply 12E) adjacent to the inside and outside of the overlapping area K is located between the band codes 10E and 10E of the other band ply 12 (in this example, the full band ply 12F). The band cord 10F of FIG.

Here, the "falling" means that the radial inner edge point of the upper band cord 10F exceeds the outer edge line EL connecting the radial outer edge points of the lower band cord 10E,
It means to go inward in the radial direction. For that purpose, it is necessary to make the direction and inclination angle of the band cord 10E with respect to the tire circumferential direction uniform with the direction and inclination angle of the band cord 10F with respect to the tire circumferential direction. Further, the pitch P between the band codes 10E and 10E
E and the pitch PF between the band codes 10F and 10F are equal to each other as in this example, or one is an integer (N) times the other, that is, PE = PF or P
It is necessary that E = N × PF or PF = N × PF.

By forming the recess 13 in this manner, the thickness TD between the cords sandwiching the band cords 10 of all the band plies 12 in the overlapping area K is formed.
Is the diameter S of each band cord 10 of each band ply 12.
Can be reduced to a value smaller than the total value ΔS.
That is, it is possible to reduce the thickness of the band layer 9 in the overlapping region K, which is the maximum thickness, and to keep the total thickness of the tread low while securing the minimum necessary rubber gauge thickness at the groove bottom of the tread rubber. It becomes possible. As a result, the rolling performance can be improved while maintaining the durability.

It is to be noted that the thickness TD between the cords is equal to the sum value ΣS
At the time described above, the total thickness of the tread increases and the rolling performance is impaired. When the thickness TD between cords is 0.5 times the total value ΔS, the band layer 9 has a substantially single-layer structure. At this time, since the cord density is limited in order to secure the cord interval between the band cords 10F and 10E, the band layer 9 improves the high-speed durability performance, the steering stability, and the functions described above. Road noise cannot be sufficiently reduced. From such a viewpoint, the inter-cord thickness TD is 0.5 of the total value ΣS.
Preferably, it is 5 to 0.90 times.

In order for the band layer 9 to effectively function as the F + E structure, as shown in FIG. 1, the width WE of the overlapping region K in the tire axial direction and the width of the full band ply 12F from the tire equator C are determined. The ratio WE / WF to WF is 1 /
It is preferred to be in the range of 12 to 8/12. If the ratio WE / WF is less than 1/12, the binding force on the outer end side becomes insufficient and the functions of the band layer 9 such as noise reduction cannot be effectively exhibited. If it exceeds 8/12, the rolling performance tends to decrease.

At the inner end of the edge band ply in the tire axial direction, a rigid step is generated, and a circumferential groove is usually arranged near the rigid step in many cases. As a result, cracks at the groove bottom have been remarkably generated, and the width of the edge band ply (corresponding to the width WE of the overlapping area K) has been regulated or the use of the edge band ply has to be abandoned. Was. However, in the present application, the rigid step at the inner end point of the edge band ply 12E is reduced by the formation of the recessed portion 13. As a result, the generation of cracks is further suppressed, and advantages such as the adoption of the edge band ply and the setting of the width are possible regardless of the position of the circumferential groove.

Next, the band layer 9 having the depression 13 can be formed by using a stretch of a tire in a vulcanization mold at the time of vulcanization molding.

Specifically, the stretch at the time of vulcanization molding, which is usually about 3%, is set to be 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. I do. In any case, at the time of vulcanization molding, the tightening effect of the upper band cord 10F acts strongly between the lower band cords 10E and 10E, thereby causing the lower part of the upper band cord 10F with respect to the lower band cord 10E ( The depression 13 is formed by relative movement (inward in the radial direction).

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 can be preferably employed. That is, the band cord 10 having an elongation of 10% or less when a load of 0.0236 g / dtex is applied is used. Thereby, the formation of the recess 13 is made possible while 3
%, The necessary restraining force by the band layer 9 can be secured, and the above-mentioned functions of the band layer 9 (improvement of high-speed durability performance, improvement of steering stability, reduction of road noise, etc.) can be effectively exhibited. .

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.

In particular, the band cord 10 having an elongation of 5% or less.
In the case of the stretch of less than 3%, a larger depression 13 can be formed and the binding force is further increased, so that the function of the band layer 9 is further improved. In addition, the uniformity can be further improved due to the decrease in stretch. An aromatic polyamide fiber cord is suitable as the band cord 10 having an elongation of 5% or less, and a nylon fiber cord is preferable as the band cord 10 having an elongation of 5 to 10%.

In the formation of the recess 13, when the band cord itself is thick, or when the cord density R (the number of cords per 1 cm width of the ply) is high, the relative movement of the band cord in the radial direction is caused. It is disadvantageous because it tends to be hindered. Therefore, the diameter S of the band cord 10 is preferably 0.9 mm or less, and the cord density R is preferably 13 cords / cm or less.

Further, the product S × R of the diameter S of the band code 10 and the code density R is an index of the band code occupation ratio in the band ply, and the smaller the value of the product S × R, the relative band code is. It is easy to move and is also advantageous for uniformity. Therefore, the product S × R is preferably set to 8.0 or less.

Further, as described above, the ratio BC / H of the belt camber amount BC of the belt layer 7 to the tire section height H is used because the depression 13 is formed by using the stretch during vulcanization molding. However, a tire having an excessively large diameter, that is, a tire having a small radius of curvature, has a problem that the difference in stretch between the center of the tread and the side of the tread shoulder becomes too large, making the production difficult and significantly impairing the uniformity.

For this purpose, it is necessary to control the ratio BC / H within the range of the following equation (1). BC / H ≦ 0.24-A × 0.23 (1) In the formula, A is a flattening rate of the tire.
= 0.60. The belt camber amount BC is
As shown in FIG. 1, the distance in the radial direction between the tire equator point and the outer end point of the belt on the inner surface of the belt layer 7 is meant.

The belt camber amount BC, the tire section height H, and the flatness A are values measured in a state where the tire is assembled on a regular rim and filled with a regular internal pressure. Standard rim specified by JATMA,
It is a rim of the size specified by "Design Rim" specified by TRA or "Measuring Rim" specified by ETRTO. "Normal internal pressure" refers to the maximum air pressure specified by JATMA, and the TRA table "TIRE LOAD LIMITS AT VARIOUS CO
Maximum value described in "LD INFLATION PRESSURES" or ET
This is "INFLATION PRESSURE" defined by RTO, and is 180 KPa for tires for passenger cars.

[0041]

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

The test method is as follows. (1) Rolling performance: Using a rolling resistance tester, test tires were mounted on a rim (15 × 6.5JJ) and an internal pressure (230 kP).
a) The rolling resistance when running at a load (4.0 kN) and at a speed (80 km / h) was measured, and was indicated by an index when Comparative Example 1 (conventional tire) was set to 100. The larger the index, the better.

(2) Durability: After running the test tire 100 km on the drum at a speed of 60 km / h under a rim (15 × 6.5 JJ), an internal pressure (200 kPa) and a load (5.5 kN). The occurrence of cracks at the bottom of the groove was visually inspected.

(3) Road noise performance: The test tire was subjected to a rim (15 × 6.5 JJ) and 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.

(4) Uniformity: JASO C
Rim (15 x 6.5 JJ), internal pressure (200 kP) in accordance with 607 "Test Method for Uniformity of Automotive Tires"
a), RFV is measured under the conditions of load (4.0 kN) and rotation speed (60 rpm), and the primary value of RFV at that time is
It was indicated by an index when Comparative Example 1 (conventional tire) was set to 100. The larger the index, the better.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

As described above, the pneumatic tire of the present invention has the following features.
In the band layer, the band code of one band ply overlaps with the band code of the other band ply, thereby reducing the thickness in the overlapping region.
Therefore, the total thickness of the tread can be kept low while maintaining the required durability, and the rolling performance and the noise performance can be improved.

[Brief description of the drawings]

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

FIG. 2 is a perspective view illustrating a band-like ply used for a band layer.

FIG. 3 is a cross-sectional view showing a recessed portion of a band cord.

FIG. 4 is a cross-sectional view of a tread portion illustrating a conventional technique.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 9 Band layer 10, 10F, 10E Band cord 11 Band ply 12, 12F, 12E Band ply 13 Falling part K Overlap area

Claims (5)

[Claims] 1. A carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, a belt layer disposed inside the tread portion and outside the carcass, and a band disposed outside the belt layer. A band formed by spirally winding a narrow band-like ply in which one or more band cords are aligned in a tire circumferential direction. At least at the outer end of the belt layer, a plurality of band plies are radially overlapped to form an overlapping region, and the band code of each band ply in the overlapping region with respect to the tire circumferential direction and By adjusting the inclination angle, the band cords of one band ply adjacent to each other inside and outside fall between the band cords of the other band ply. By non-sagging portion is formed, the inter-cord thickness TD sandwiching the band cord of all band ply in the overlap region, the diameter S of each band cord of the band ply
A pneumatic radial tire characterized by being smaller than the total value ΔS of the pneumatic radial tires. 2. The inter-cord thickness TD is equal to the sum value ΣS
2. The pneumatic radial tire according to claim 1, wherein the ratio is 0.55 to 0.90 times of the following. 3. The band code is 0.0236 g / d.
3. The pneumatic radial tire according to claim 1, wherein an elongation percentage when a load of tex is applied is 10% or less. 4. The belt layer according to claim 1, wherein a ratio BC / H of a belt camber amount BC, which is a radial distance between a tire equatorial point and an outer end point of the belt on the inner surface of the belt layer, to a tire cross-sectional height H is: The pneumatic radial tire according to claim 1, 2 or 3, wherein the value falls within the range of the following equation (1). BC / H ≦ 0.24-A × 0.23 (1) In the equation, A is the flatness of the tire. 5. The belt layer has a stretch of 3 during vulcanization.
%. The pneumatic radial tire according to claim 3, wherein