JPH04215502A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve controllability with low noises in a pneumatic radial tire for a passenger car by locating a carcass winding-up part radially inside the tread of the tire and overaying it on a largest width belt ply with a predeter mined width while specifying a ratio of carcass height to bead A-peck height. CONSTITUTION:In a flat tire having 0.70 or less of ratio H/W of tire section height H to tire width W, a carcass 6 consisting of 1 ply of an organic fiber cord is wound up from the inside to the outside around a bead core 5 so that the tip 6B is located radially inside a tread 2. Then, the tread overlaps the tip such that a distance BC between the largest width belt ply 7A of a belt 7 formed of aromatic polyamide and the outside end PB is 0.1-0.4 times the ratio of the belt ply 7A to the width BW1. Also, ratio HA/HC of bead A-peck height HA to carcass height HC is specified to 0.45-0.80.

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 that can reduce the weight of the tire, and particularly to a pneumatic radial tire that can be suitably used for passenger cars.

0002

[Background Art] In recent years, as vehicles have become more sophisticated and high-performance,
Tires are becoming larger and have a lower profile. In order for such tires to exhibit the required performance, steel cords are used in the belt layer to increase the hoop effect, especially in the shoulder area.

On the other hand, there is also a demand for lighter tires due to fuel efficiency regulations, etc., and together with the increase in the size of tires, it is difficult to reduce the weight of belts using steel cords. Therefore, it may be possible to reduce the weight by using an aromatic polyamide cord in the belt.

0004

[Problems to be Solved by the Invention] However, although aromatic polyamide cords have the same tensile strength as steel cords, they are inferior in compression and flexibility, resulting in decreased tire handling stability and increased tire noise. do.

An object of the present invention is to provide a pneumatic radial tire that can reduce tire weight while reducing deterioration in various performances such as tire noise and handling stability.

[0006]

[Means for Solving the Problems] The present invention has a main body part extending from the tread part through the sidewall part to the bead core of the bead part, and is provided with a winding part that is wound around the bead core from the inside to the outside of the tire. A carcass consisting of one carcass ply using organic fiber cords arranged substantially in the radial direction, and two carcass plies using aromatic polyamide cords arranged on the outside of the carcass in the tire radial direction and inside the tread part. A belt consisting of a belt ply extends outward in the tire radial direction from the bead core between the main body part and the winding part, and has a JISA hardness of 75.
The rolled-up portion of the carcass has a tapered triangular bead apex made of rubber material with an angle of 95 degrees or more and 95 degrees or less. The distance in the tire axial direction (BC ) and the width (BW1) of the maximum width belt ply in the tire axial direction BC/
BW1 is 01 or more and 04 or less, and the bead apex height (HA) is the distance in the tire radial direction from the bead baseline to the tire radial tip of the bead apex, and to the carcass center in the tire equatorial plane. This is a pneumatic radial tire in which the ratio HA/HC to the carcass height (HC), which is the distance in the tire radial direction, is 0.45 or more and 0.80 or less.

[0007]

[Operation] By using a belt made of aromatic polyamide cord, the weight of the tire can be reduced. As a result, the bending rigidity of the belt decreases, resulting in an increase in tire noise and a decrease in steering stability.
The layers increase the tension applied to the belt, increasing the belt's substantial bending stiffness. In addition, by rolling up the carcass end until it is positioned inside the belt in the tire radial direction, the rigidity of the sidewall part is increased and the JIS
By setting the bead apex made of a rubber composition with A hardness of 75 degrees or more at a height of 45 to 80% of the carcass height, the lack of rigidity caused by using a single carcass ply is compensated for.

Furthermore, when a band layer in which organic fiber cords made of composite fibers are arranged substantially parallel to the circumferential direction of the tire is arranged on the outer side of the belt in the tire radial direction, the durability and performance at high speeds are further improved. It is possible to improve steering stability and grip performance.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross section of a pneumatic radial tire 1 including the tire shaft in a normal condition, mounted on a normal rim R and filled with normal internal air pressure.

The tire 1 is formed as a flat tire with a ratio H/W of tire width W and tire cross-sectional height H of 0.70 or less.

[0012] The tire 1 has a main body part 6A extending from the tread part 2 through the sidewall part 3 to the bead core 5 of the bead part 4, and a rolled-up part 6B that is wound around the bead core 5 from the inside to the outside of the tire. A carcass 6 is provided. Further, the carcass 6 is made of one carcass ply using organic fiber cords such as nylon, polyester, aromatic polyamide, etc. arranged substantially in the radial direction. The outer end of the passing belt 7 in the tire axial direction extends inward and terminates on the inner side of the belt 7 in the tire radial direction.

The belt 7 is made up of two belt plies 7A and 7B made of aromatic polyamide cord, and in this example, the belt ply 7A located on the inside in the radial direction of the tire is made wider than the belt ply 7B on the outside in the radial direction of the tire. It is set. Note that they can be reversed or set to the same width. The cords of the belt plies 7A and 7B are arranged to cross each other and are inclined at an angle of 5 to 40 degrees with respect to the tire circumferential direction.

Further, in the tire 1, the distance BC in the tire axial direction from the tire axial direction outer end PB of the maximum width belt ply, in this example, the inner belt ply 7A to the tip PC of the carcass winding part 6B, and the width belt The ratio BC/BW1 of the ply 7A to the width BW1 in the tire axial direction is set to 0.1 or more and 0.4 or less. If it is less than 0.1, it will be difficult to improve the lateral stiffness of the tire and maintain steering stability, and if it is more than 0.4, the weight of the tire will increase and the tension of the belt will decrease, making the tire stiffer. Noise increases.

More preferably, the distance BC is at least 10% of the width BW2 in the tire axial direction of the overlapping area of the two belt plies 7A and 7B, that is, the width BW2 of the belt ply 7B between the two belt plies 7A and 7B, and 40%
% or less.

As described above, by using the belt 7 made of aromatic polyamide cord, the weight of the tire can be reduced. This reduces the belt's bending rigidity, resulting in an increase in tire noise and a decrease in steering stability. By using a single carcass ply and increasing the tension applied to the belt, the effective bending rigidity of the belt is increased. There is.

Further, in the tire 1, a tapered triangular bead apex 8 is provided on the outside of the bead core 5 in the tire radial direction, extending radially outward between the main body portion 6A and the winding portion 6B. The bead apex 8 is JISA
It is formed from a rubber composition with a hardness of 75 degrees or more and 95 degrees or less. If the angle is less than 75 degrees, the lateral rigidity of the bead portion 4 will be insufficient and the steering stability will deteriorate. Furthermore, bead baseline B
The bead apex height HA is the distance in the tire radial direction from L to the tip P8 of the bead apex 8, and the radial distance from the bead baseline BL to the center of the thickness of the carcass 6 on the equatorial plane CO. A certain carcass height H
The ratio HA/HC with C is set to 0.45 or more and 0.80 or less. If it is less than 0.45, the lateral rigidity of the bead portion will be insufficient and the steering stability will deteriorate. If it exceeds 0.80, the tire weight cannot be reduced, and the ride comfort performance deteriorates.

As mentioned above, the carcass winding section 6B
By winding the upper end of the belt to the inside of the tire in the radial direction, the rigidity of the sidewall part is increased, and the bead apex 8, which is made of a rubber composition with a JISA hardness of 75 degrees or higher, is rolled up to a carcass height of HC of 45 degrees.
By setting the height to ~80%, the lack of rigidity caused by using only one carcass ply can be compensated for.

Furthermore, in this example, the tread 2 consists of a cap layer 2A made of rubber with excellent wear resistance and grip properties on the outside of the tire radius, and a base layer 2B made of rubber with a small loss tangent. In addition to improving the tire's grip performance, it also aims to reduce fuel consumption.

In this embodiment, a band layer 10 is disposed on the outer side of the belt 7 in the tire radial direction in order to further increase the rigidity of the belt. In this example, the band layer 10 is made of a ply formed by continuously winding a ribbon made of 5 to 12 organic fiber cords arranged in parallel in a spiral shape. As a result, the cords within the band layer 10 are arranged substantially parallel to the circumferential direction of the tire. Also, the strength of the band layer cord when stretched by 3% is 25 g/d.
and the elongation rate is 8% when applying a tensile force of 6 g/d.
It is as follows. This characteristic makes it possible to grow the outer diameter appropriately when the tire is vulcanized, and to obtain a strong hoop effect and high bending rigidity of the belt when the tire is filled with air and running. Such cords are made of organic composite fibers made by twisting low-modulus filaments such as nylon with high-modulus filaments such as aromatic polyamide fibers, fully aromatic polyester fibers, or polyvinyl alcohol fibers with a strength of 15 g/d or more. It can be obtained by using fiber cord.

Furthermore, when the band layer 10 in which the organic fiber cords made of composite fibers are arranged substantially parallel to the tire circumferential direction is arranged on the outer side of the belt 7 in the tire radial direction, durability is improved. It is possible to improve performance, steering stability at high speeds, and grip performance.

(Specific Example) Tires with a tire size of 225/50R16 were prepared according to the specifications shown in Table 1, and the results of various performance evaluations are also shown in the table.

[0023]

[Table 1]

[0024] The tire weight of the present product was lighter than that of a conventional tire having a steel cord belt, and the various performances were able to be maintained almost the same.

[0025]

As described above, the pneumatic radial tire of the present invention can reduce tire weight while suppressing increase in tire noise and decrease in steering stability due to decrease in belt bending rigidity.

[Brief explanation of the drawing]

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

[Explanation of symbols]

1 Tires 2 Tread 3 Sidewall part 4 Bead part 5 Bead core 6 Carcass 7 Belt 8 Bead Apex

Claims (1)

[Claims] Claim 1: A main body section extending from the tread section through the sidewall section to the bead core of the bead section is provided with a winding section that is wound around the bead core from the inside to the outside of the tire and arranged substantially in the radial direction. A carcass consisting of one carcass ply using an organic fiber cord made of organic fibers, and a belt consisting of two belt plies using an aromatic polyamide cord and arranged on the outside in the tire radial direction and inside the tread part of the carcass, A tapered triangular bead apex extending outward in the tire radial direction from the bead core between the main body part and the winding part and made of a rubber material with a JISA hardness of 75 degrees or more and 95 degrees or less, and is attached to a regular rim. , in a cross section including the tire shaft in a normal state filled with the normal internal pressure, the rolled up part of the carcass is located from the sidewall part to the axially outer end of the belt to the inner side of the tread part in the tire radial direction, and at the maximum The ratio BC/BW1 of the distance in the tire axial direction from the tire axial direction outer end of the belt ply with the width to the tire axial direction width (BC) to the tire axial direction width of the belt ply with the maximum width (BW1) is 0. 1 or more and 0
．． 4 or less, and the bead apex height (HA), which is the distance in the tire radial direction from the bead baseline to the tire radial tip of the bead apex, and the tire radial direction distance from the tire radial direction to the carcass center in the tire equatorial plane. The ratio HA/HC to the carcass height (HC), which is the distance, is 0.
A pneumatic radial tire with a rating of 45 or higher and 0.80 or lower.