JP2003200709A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of reducing the outside noise generated from the tire while keeping the driving stability and the comfort. <P>SOLUTION: The pneumatic radial tire has a carcass with the radial ply formed by the inner carcass ply and the outer carcass ply. The outer carcass ply hangs down along the outer surface of a bead apex in the axial direction of the tire and ends between the bead core and a stand-up part of the inner carcass ply. The bead part has a chafer and a filler, and the denier number d1P of the carcass strips of the inner carcass ply and the denier number d2P of the carcass strips of the outer carcass ply satisfy following expression (1): 0.4≤d1P/d2P≤0.8. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire capable of reducing external noise generated from a tire while maintaining steering stability and ride comfort. 2. Description of the Related Art In recent years, there has been a demand for reduction of outside (passing) noise generated from tires during running, and regulations have been becoming stricter legally. Conventionally, in order to reduce the noise generated from tires, the occurrence of sound and vibration has been suppressed by reducing the rigidity of the carcass by using a thin thread for the carcass cord constituting the carcass. [0004] However, when a fine thread is used as a carcass cord, there is a problem that the steering rigidity is reduced due to the decrease in tire rigidity as described above. As described above, suppression of noise outside the vehicle and securing of steering stability have a trade-off relationship. [0005] The inventor has conducted research and experiments in order to achieve both suppression of noise outside the vehicle and securing of steering stability. As a result, the carcass is formed by two carcass plies. A carcass cord of a thick thread is used for one of the two carcass plies, and a carcass cord of a thin thread is used for the other ply. In addition, there is a range in which noise outside the vehicle can be reduced without impairing steering stability by regulating the relative ratio of the thickness of both carcass cords. Was found. The present invention is based on the fact that a carcass is formed by a carcass ply using a carcass cord of a fine thread and a carcass ply using a carcass cord of a thick thread, while maintaining steering stability and riding comfort. It aims to provide a pneumatic radial tire that can reduce outside noise. [0007] The invention according to claim 1 is a pneumatic radial tire, in which a carcass ply is folded from a tread portion through a sidewall portion and around a bead core of a bead portion. And a radially arranged carcass formed by an outer carcass ply extending at least in the vicinity of the bead core from the tread portion through the sidewall portion outside the carcass ply therein, and the inner and outer carcass plies include: Both are made of carcass cords using organic fibers, and the carcass ply inside hangs down from the tread portion through the sidewall portion and along the inner surface of the bead apex in the tire axial direction, and the tire shaft around the bead core of the bead portion. Turn back from inside to outside and stand outside the bead apex The outer carcass ply has a rising portion, and the outer carcass ply passes through the sidewall portion from the tread portion, hangs down along the tire axial direction outer surface of the bead apex, and has the bead core and the rising portion of the inner carcass ply. And between the bead portion, a synthetic or natural fiber is knitted in a net shape, and on the outer side of the bead portion in the tire axial direction, from the outer surface of the rising portion of the inner carcass ply, A chafer extending inward in the tire axial direction along the bottom surface and rising along the inner wall surface of the bead portion, and made of synthetic or natural fiber, is arranged around the bead core 5 between the inner carcass ply and the bead core. And the carcass cord of the inner carcass ply has a denier d1P and the carcass cord of the outer carcass ply has a denier of d1P. A pneumatic radial tire characterized by satisfying the following formula (1) and the Le number D2P. 0.4 ≦ d1P / d2P ≦ 0.8 (1) In the carcass, the carcass cord of the outer carcass ply is preferably 1500 denier or more. The inner carcass ply has a so-called 1-1 structure in which the outer carcass ply passes outside the bead core in the tire axial direction as shown in FIG. The inner carcass ply can be formed as a so-called low turn-up in which the winding end terminates inward in the tire radial direction from the tip of the rim flange, and the so-called terminating end terminates outward in the tire radial direction from the tip of the bead apex. It may be formed as a high turn-up. Since the carcass of the radial arrangement is provided, it has better ground contact and less occurrence of noise outside the vehicle than the tire of the bias arrangement. The inner and outer carcass plies have different denier numbers d1P and d2P of the respective carcass cords constituting them, and regulate the ratio d1P / d2P as follows. 0.4 ≦ d1P / d2P ≦ 0.8 (1) As a result, the noise outside the vehicle can be reduced without lowering the steering stability and ride comfort. If the ratio d1P / d2P is less than 0.4, the rigidity of the tire is reduced, and the steering stability is reduced. Also d1P /
When the ratio of d2P is in the range exceeding 0.8, when the denier numbers of both carcass cords are both large and approach one, that is, when the yarn is thick, the noise outside the vehicle cannot be suppressed,
Also, when the denier number of both carcass cords is small and approaches 1, that is, when the carcass cord is a fine thread, the rigidity of the tire is reduced and steering stability is impaired. As described above, the ratio d1P / d2P must be restricted to a limited range in order to achieve both steering stability and noise suppression. When the outer carcass cord is 1500 denier or more, the steering stability is further improved. An embodiment of the present invention will be described below with reference to the drawings. 1 to 3, the pneumatic radial tire 1 includes a carcass 10 formed by an inner carcass ply 11 and an outer carcass ply 12. The carcass ply 11 in the tread portion 2
Through the sidewall portion 3 and along the inner surface of the triangular bead apex 8 in the tire axial direction, and bends around the bead core 5 of the bead portion 4 from the inner side to the outer side in the tire axial direction. 8 is formed. In this embodiment, the leading end 11a of the rising portion is located radially inward of the flange outer end P of the regular rim J to which the bead portion 4 is fitted. The outer carcass ply 12 is disposed outside the inner carcass ply 11, hangs down from the tread portion 2 through the sidewall portion 3 along the outer surface of the bead apex 8, and has a bead core of the bead portion 4. 5
In the vicinity, between the bead core 5 and the folded portion of the carcass ply 11 therein, and as shown in FIG. 1, without reaching the bottom surface of the bead core 5, the rising of the inner carcass ply 11 is performed. Terminating between the parts. Thus, the carcass 10 is formed as a so-called 1-1 LTU structure. Both the inner carcass ply 11 and the outer carcass ply 12 are provided with carcass cords 13 and 14 made of organic fibers such as nylon, polyester, rayon, and aromatic polyamide fibers 70 to 9 with respect to the tire equator C.
A sheet body is formed by covering an interdigital fabric inclined at an angle of 0 degrees with a topping rubber 15. Of which
Between the outer carcass plies 11 and 12, the carcass cords 13 and 14 are arranged in a direction crossing each other. The carcass cords 13 and 14 have a denier of 1500 d or less and 600 d or more, preferably 1 d.
000d or more. In addition, the number of carcass cords 13, 14 to be driven per unit length is substantially the same between the inner and outer carcass plies 11, 12. Here, the inner and outer carcass plies 11, 1
2, the denier number d1P of the carcass cord 13 of the inner carcass ply 11 and the denier number d2P of the carcass cord 14 of the outer carcass ply 12 are made different from each other, as shown in FIG. 2 and the following equation (1). Outside carcass ply 11
Is larger than the denier number d2P of the cord of the carcass ply 12, and the ratio d1P /
d2P is set at a ratio of 0.4 ≦ d1P / d2P ≦ 0.8 (1). Table 1 shows an example of the structure and characteristics of two carcass cords having different denier numbers d1P and d2P, that is, a thick yarn and a thin yarn. The steering stability can be further improved by setting the carcass cord of the outer carcass ply 11 to 1500 denier or more. [Table 1] In the tread portion 2, the carcass 1
0 in the radial direction outside and inside the tread portion 2
7 are arranged. In the present embodiment, the belt layer 17 comprises two belt plies in which a belt cord made of an organic fiber cord or a steel cord such as nylon, rayon, polyester, or aromatic polyamide or the like is inclined with respect to the tire equator C and arranged in parallel. The belt cords are arranged in a direction intersecting each other and are formed by overlapping with each other so as to exert a tag effect, thereby increasing the rigidity of the tread portion 2. The tread portion 2 is provided with a band layer 19 made of a ply in which a band cord is buried, radially outside the belt layer 17 to prevent lifting of the belt layer 17 due to centrifugal force during tire running. I have. In the present embodiment, the bead apex 8 made of hard rubber rises from the bead core 5 outward in the tire radial direction, and the chafer 21 and the filler 22 which reinforce the bead 4 are provided in the present embodiment. And The chafer 21 is formed by knitting synthetic or natural fibers into a net shape, and has one end attached to the outer surface of the outer carcass ply 12 outside the bead portion 4 in the tire axial direction, and along the bottom surface 4a of the bead portion 4. And rises inward in the tire axial direction and rises along the inner wall surface of the bead portion 4. Therefore, the chafers 21 are formed on the outer side of the bead portion in the tire axial direction from the outer surface of the rising portion of the inner carcass ply by the bead portion. Extends inward in the tire axial direction along the bottom surface of the tire and rises along the inner wall surface of the bead portion. The filler 22 is provided with synthetic or natural fibers, and is disposed between the carcass ply 11 and the bead core 5 so as to surround the bead core 5. Such a chafer 21 and a filler 22 are provided.
Intervening helps to increase the vertical and horizontal rigidity of the bead portion 4. The bead portions may be formed without providing chafers and fillers. As described above, the pneumatic radial tire of the present invention has a so-called 1-1 carcass. [Specific Example] 1) Test 1 A tire (1-1 LTU) having a tire size of 215 / 65R15 and having the structure shown in FIG. 1 was manufactured by changing the denier number ratio d1P / d2P and each tire was manufactured. The exterior noise of the vehicle was investigated. The noise outside the vehicle is a car standard JASO Z 10
The overall noise was measured during steady running at a speed of 60 km / h at a speed of 60 km / h. The test results are shown in the graph of FIG. As a result of the test, it was confirmed that the noise outside the vehicle was reduced when the ratio d1P / d2P was 1.2 or more. 2) Test 2 Tires having the same size and the same carcass structure as those of Test 1 were prototyped according to the specifications shown in Table 2 (Examples 1 to 3), and their performance was tested. Further, a tire having a conventional configuration (conventional example) and a tire having a configuration other than the present application (Comparative Example 1,
A test was also conducted for 2), and the performance was compared. In the test, each test tire was tested for 15 × 6 1/2 −
The vehicle was mounted on a 4.5-liter FR car via a JJ rim, and the vehicle was run under an internal tire pressure of 2.0 kgf / cm2. The test procedure is as follows. A) Running at a speed of 60 km / h in substantially the same manner as in the outside noise test 1),
The overall noise was measured, and the noise reduction (dBA) was displayed based on the conventional example. B) Road noise Each reduction amount (dBA) of the overall noise on a rough asphalt road at a speed of 50 km / h compared to the conventional example as 0.
Was displayed. (C) Driving stability and ride comfort In the tests of the above (a) and (b), the judgment was made based on the feeling of a single passenger. In Table 2, ○ indicates good, Δ indicates slightly defective, and × indicates defective. [Table 2] As a result of the test, the example of the embodiment is a conventional example,
It was confirmed that noise could be reduced while maintaining steering stability and riding comfort as compared with the comparative example. As described above, the pneumatic radial tire of the present invention having the above-described structure can reduce noise generated from the tire during traveling while maintaining steering stability and riding comfort. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a right half sectional view of a tire showing one embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating the configuration of the carcass. FIG. 3 is a graph showing a relationship between a denier ratio of a carcass cord and noise outside the vehicle. [Description of Signs] 2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 10, 10A Carcass ply 12, inside carcass 11, 11A Carcass ply 13, 12 outside carcass ply 13, 14 Carcass cord

Claims (1)

Claims: 1. A carcass ply inside a tread portion, which passes through a sidewall portion and turns around a bead core of a bead portion, and at least passes through a sidewall portion from a tread portion to a sidewall outside the carcass ply inside the carcass ply. A carcass ply having a radial arrangement formed by an outer carcass ply extending near the bead core, wherein the inner and outer carcass plies are both made of a carcass cord using organic fibers, and the inner carcass ply is A rising portion that hangs down from the tread portion through the sidewall portion and along the inner surface of the bead apex in the tire axial direction, turns around the bead core of the bead portion from the inside in the tire axial direction to the outside, and rises outside the bead apex. And the outside carcass ply is from the tread Passing through the sidewall portion, hanging down along the tire axial direction outer surface of the bead apex and terminating between the bead core and the rising portion of the inner carcass ply, a synthetic or natural fiber is formed in the bead portion. It is knitted in a net shape, and extends from the outer surface of the rising portion of the inner carcass ply in the tire axial direction outside of the bead portion to the inward in the tire axial direction along the bottom surface of the bead portion and to the inner wall surface of the bead portion. Along with a chafah standing up along with a carcass ply of synthetic or natural fibers,
A filler arranged between the bead core and the bead core 5 is provided, and the denier number d1P of the carcass cord of the inner carcass ply and the denier number d2P of the carcass cord of the outer carcass ply are as follows (1). A pneumatic radial tire that satisfies the formula. 0.4 ≦ d1P / d2P ≦ 0.8 (1)