JP3260465B2 - Pneumatic radial tire - Google Patents

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, and more particularly, to reduction and control of road noise in an extremely low frequency range of around 40 Hz as well as reduction of road noise in a low frequency range of 100 to 315 Hz. The present invention relates to a pneumatic radial tire suitable for a passenger car, which can ensure stability.

[0002]

2. Description of the Related Art When a passenger car travels at high speed on a rough road surface having a rough surface with a large coefficient of friction, the vibration transmitted from the tires into the vehicle interior causes a low frequency range of 100 to 315 Hz (hereinafter referred to as a low frequency range road). (Called "noise"). Recent demands for noise reduction include not only such low-frequency road noise, but also extremely low-frequency road noise around 40 Hz (hereinafter referred to as extremely low-frequency road noise), which has not conventionally been considered a problem. ) Is also required to be reduced.

[0003] Regarding the former low frequency band road noise,
JP-A-1-34162 proposes that the primary natural frequency of a tire can be reduced by reducing it so as not to match the cavity frequency of the vehicle interior. And
Since this primary natural frequency is inversely proportional to the square root of the weight of the tread portion and proportional to the square root of the vertical spring constant of the sidewall portion, if the vertical spring constant of the sidewall portion is reduced, the low-frequency load can be reduced. Noise reduction can be realized.

[0004] However, when the vertical spring constant of the side wall portion is reduced in this way, there is a problem that the extremely low frequency band road noise increases and the steering stability decreases. Therefore, at present, a practical solution for achieving the above three at the same time has not been obtained.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic radial that not only reduces road noise in a low frequency range but also reduces road noise in an extremely low frequency range and ensures steering stability. To provide tires.

[0006]

In order to achieve the above object, the present invention is to dispose bead fillers on the outer periphery of left and right bead cores, mount both ends of a carcass layer on these bead cores, and In a pneumatic radial tire having a bead filler reinforcing layer disposed along the JIS-A hardness of 70,
To 95, the total cross-sectional area A (mm ² ) of the bead filler, the radial height hF (mm) of the bead filler from the bead base, and the tire of the bead filler reinforcing layer from the bead base. Radial height hR
(Mm) is the tire radial height hF (mm) or the tire section height SH (mm) of the bead filler, respectively.
2.0 ≦ A / hF ≦ 3.0 (mm) 0.25 ≦ hF / SH ≦ 0.5 0.5 ≦ hR / hF ≦ 1.0 It is.

The inventors of the present invention have studied the factors that cause the generation of extremely low frequency band road noise. As a result, the extremely low frequency band road noise is closely related to the torsion of the sidewall portion in the tire circumferential direction. It has been found that the greater the tire circumferential rigidity, the more advantageous the reduction. It is well known that the tire steering stability contributes more to the tire circumferential rigidity than to the tire lateral rigidity. The present invention
From both of these findings, the hardness of the bead filler is set to a specific size, a reinforcing layer such as a fiber cord or a steel cord is arranged along the bead filler, and the sizes of the bead filler and the reinforcing layer are adjusted. By adjusting the above relationship, the tire circumferential rigidity is improved while suppressing an increase in the vertical spring constant of the sidewall portion.
With this configuration, low-frequency road noise can be reduced, and extremely low-frequency road noise can be reduced and steering stability can be ensured.

Hereinafter, the present invention will be described with reference to embodiments shown in the drawings. FIG. 1 is a pneumatic radial tire showing one embodiment of the present invention. In the figure, 1 is a tread part,
Reference numeral 2 denotes a sidewall portion, 3 denotes a bead portion, and 6 denotes a bead core. The carcass layers 4 and 4 ′ are provided in two inner and outer layers, respectively, at a cord angle of 70 ° to 90 ° with respect to the tire circumferential direction. The outer carcass layer 4 ′ is folded back so as to wrap the bead filler 7 from the outside.
Has both end portions 4 ′ e wound down to the heel portion of the bead portion 3 outside the folded end portion 4 e of the inner carcass layer 4.

A bead filler reinforcing layer 8 is arranged between both ends 4e and 4'e of the inner carcass layer 4 and the outer carcass layer 4 'along the bead filler 7. Also,
On the outer peripheral side of the tread portion of the outer carcass layer 4 ′, two belt layers 5 are provided so as to intersect with each other at a cord angle of 10 to 30 ° with respect to the tire circumferential direction. A cover that covers each end of the shoulder,
A belt cover layer 9 with a cover covering the whole is arranged.

In the above structure, the bead filler 7
It is made of rubber having an IS-A hardness of 70 to 90. In addition, the ratio A / hF of the total cross-sectional area A (mm ² ) to the tire radial height hF (mm) of the bead filler 7 from the bead base B to the tire radial height h is 3.0 (mm) or less, and the tire radial height is HF (mm) to the tire section height SH (m
m), the bead filler 7 is made as thin and thin as possible to reduce the vertical spring constant of the side wall portion and reduce low frequency road noise by making the size 0.25 times or more of m). I have. However, when the bead filler 7 too elongated too thin, even if provided with the bead filler reinforcing layer 8 which will be described later, so it can not be secured the steering stability, the tire radial height hF of the total cross-sectional area A (mm ²⁾ The lower limit of the ratio to (mm) is 2.0 (mm)
(2.0 ≦ A / hF) and tire height hF in the radial direction.
(Mm) is 0.0.
5 (mm) (hF / SH ≦ 0.5)
There is .

On the other hand, if the vertical spring constant of the side wall portion is simply reduced, road noise in an extremely low frequency range is deteriorated, and steering stability is also reduced. As described above, the reduction of road noise in the extremely low frequency range and the assurance of steering stability are possible by increasing the rigidity in the circumferential direction of the tire, and therefore, the radial height hF (m) of the bead filler 7 along the bead filler 7.
The bead filler reinforcing layer 8 having a height of 0.5 times or more of m) is disposed. However, if the height hR of the bead filler reinforcing layer 8 from the bead base B in the tire radial direction is too large, the effect of reducing the vertical spring constant of the sidewall portion is impaired. Is set to a height (1.0 times) equivalent to the tire radial height hF of the bead filler 7.

In the present invention, the cord reinforcing material constituting the bead filler reinforcing layer is not particularly limited, but preferably, an organic fiber cord such as steel cord, nylon, or aramid is used.

[0013]

【Example】

Example 1 A tire size of 215 / 65R15 96S, a tire structure of FIG. 1, and a bead filler reinforcing layer of 1 × 5 (0.25)
The ratio A / hF of the total cross-sectional area A to the tire radial height hF of the bead filler, and the ratio hF / of the tire radial height hF of the bead filler to the tire cross-sectional height SH are made in common. SH, a ratio hR / hF of a tire radial height hR of the bead filler reinforcing layer to a tire radial height hF of the bead filler, and a JIS-A hardness Hs of the bead filler, as shown in Table 1, respectively. Pneumatic radial tires of Invention Tires 1 to 3 and Comparative Tires 2 to 5 were produced.

The tire 1 of the present invention has the same structure as the comparative tire 1 except that no bead filler reinforcing layer is provided.
Was made. With respect to these eight types of tires, low-frequency road noise, extremely low-frequency road noise, and steering stability were evaluated by the following methods, and the results are shown in Table 1.

Road noise in low frequency range and extremely low frequency range : 2
A test tire filled with air pressure of 00 kPa (2.0 kgf / mm ² ) is assembled on a rim of 15 × 61 / 2JJ, mounted on a vehicle with a displacement of 4500 cc, and runs on a rough road surface at a speed of 50 km / h. 100 ~
When listening to road noise in the 315 Hz band on the side of the driving window,
The feeling was evaluated by five panelists and evaluated by the 10-point method, and the average value was shown. The higher the score, the lower the road noise.

The extremely low frequency road noise means that the road surface in the low frequency road noise is extremely low frequency (40 Hz).
The evaluation was performed in the same manner except that the patch (paved road) was easily evaluated. Steering stability: The assembled rim road noise test method and the same rim, the test tire was filled with the same air pressure is mounted on the same vehicle, steering stability when traveling on a slalom test path pylon is erected at 30m intervals The sex was evaluated by a 10-point method based on a feeling by five panelists,
The average was displayed. The higher the score, the better the steering stability.

[0017] From Table 1, the tires 1 to 3 of the present invention all reduce or reduce the low frequency band road noise as compared with the comparative tire 1, and equal or reduce the extremely low frequency band road noise, and have the same or improved steering stability. Let me. On the other hand, it can be seen that the comparative tires 2 to 5 are inferior in the extremely low frequency band road noise, the low frequency band road noise reduction effect, or the steering stability as compared with the comparative tire 1 and are incompatible.

Example 2 In the tire 1 of the present invention of Example 1, the ratio A / h of the total cross-sectional area A to the height hF of the bead filler in the tire radial direction is shown.
F only, 1.5 (mm), 2.0 (mm), 3.0
(Mm) and 3.5 (mm), four types of tires were manufactured, and the low frequency band road noise of these tires was evaluated. The result is shown in FIG. 2 for the present tire 1 (A / hF =
2.5 mm).

FIG. 2 shows that even when hF / SH satisfies the requirements of the present invention, when A / hF exceeds 3.0 (mm), the road surface noise increases due to an increase in the vertical spring constant of the side wall. It turns out that is worse. Example 3 In the tire 1 of the present invention of Example 1, the tire section height S
Four types of tires were manufactured in which only the ratio hF / SH of the height hF of the bead filler to the tire in the radial direction of the tire was changed to 0.22, 0.25, 0.5 and 0.55. The frequency band road noise was evaluated. FIG. 3 shows the result of the present invention tire 1 ((hF / SH = 0.35)).
The results are shown together with the results. From FIG. 3, even if A / hF satisfies the requirements of the present invention, if hF / SH is less than 0.25,
Extremely low frequency road noise is deteriorated due to a decrease in the vertical spring constant of the sidewall portion.

[0020]

According to the present invention, the bead filler has a specific hardness, a bead filler reinforcing layer is arranged along the bead filler, and the cross-sectional area and height of the bead filler and the bead filler reinforcing layer are further increased. The height of the tires can be adjusted so as to satisfy a specific relationship, thereby improving the circumferential rigidity of the tire while reducing the vertical spring constant of the sidewall, and reducing the low-frequency road noise. It is possible to reduce the extremely low frequency band road noise and at the same time secure the steering stability and achieve both.

[Brief description of the drawings]

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

FIG. 2 is a graph showing the relationship between A / hF indicating the size of a bead filler and low frequency band road noise.

FIG. 3 is a graph showing a relationship between hF / SH indicating a size of a bead filler and an extremely low frequency band road noise.

[Explanation of symbols]

2 Sidewall portion 4, 4 'Carcass layer 6 Bead core 7 Bead filler 8 Bead filler reinforcing layer hF Bead filler height in tire radial direction hR Bead filler reinforcing layer in tire radial direction SH Tire section height B Bead base

Continuation of the front page (56) References JP-A-58-149805 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 15/00-15/06

Claims (1)

(57) [Claims] 1. A pneumatic radial in which bead fillers are arranged on the outer periphery of left and right bead cores, both ends of a carcass layer are mounted on these bead cores, and a bead filler reinforcing layer is arranged along the bead fillers. In the tire, the JIS-A hardness of the bead filler is set in a range of 70 to 95, and the total cross-sectional area A (mm
² ), the tire radial height hF (mm) of the bead filler from the bead base, and the tire radial height hR (mm) of the bead filler reinforcing layer from the bead base.
With respect to the tire radial height hF (mm) or the tire cross-sectional height SH (mm) of the bead filler, respectively: 2.0 ≦ A / hF ≦ 3.0 (mm) 0.25 ≦ hF / SH a pneumatic radial tire having a relationship ≦ 0.5 0.5 ≦ hR / hF ≦ 1.0.