JPH06262914A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To reconcile the reduction of not only low-frequency region load noise but also very-low-frequency region load noise with ensuring maneuvering stability. CONSTITUTION:The JIS-A hardness of a bead filler 7 is made 70-95. Also the total cross section area A (mm<2>) of the bead filler 7 and the tire radius direction height hF (mm) and hR (mm) of the bead filler 7 and a bead filler reinforcing layer 8 from a bead base respectively are made to satisfy the relations of A/hF <=3.0 (mm), hF/SH >=0.25, and 0.5 >=hR/hF >=1.0 to the hF (mm) or tire cross section height SH (mm).

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 not only reduction of road noise in a low frequency range of 100 to 315 Hz but also reduction and operation of road noise in an extremely low frequency range of around 40 Hz. The present invention relates to a pneumatic radial tire suitable for passenger cars, which is capable of both ensuring stability.

[0002]

2. Description of the Related Art When a passenger car travels at a high speed on a road surface having a rough surface and a large friction coefficient, vibrations transmitted from tires to the interior of the vehicle cause a low frequency range of 100 to 315 Hz (hereinafter referred to as a low frequency range load). It produces an unpleasant noise called "go". Recent demands for noise reduction are not limited to such low-frequency road noise, and road noise in the extremely low-frequency region around 40 Hz (hereinafter referred to as extremely low-frequency road noise), which has not been a problem in the past. That is also required to reduce.

Regarding the former low frequency road noise,
JP-A-1-34162 proposes that the primary natural frequency of a tire can be reduced by reducing it so that it does not match the cavity frequency in the vehicle interior. And
This primary natural frequency is inversely proportional to the square root of the weight of the tread, and is also proportional to the square root of the vertical spring constant of the sidewall. Noise reduction can be achieved.

However, when the vertical spring constant of the sidewall portion is reduced in this way, there is a problem that extremely low frequency band road noise increases and steering stability deteriorates. Therefore, in the present situation, a practical solution that simultaneously achieves the above three factors has not been obtained.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is not only to reduce low-frequency region road noise, but also to reduce the extremely low-frequency region road noise and to ensure steering stability. To provide tires.

[0006]

Means for Solving the Problems The present invention to achieve the above object is to arrange a bead filler on the outer periphery of left and right bead cores, mount both end portions of a carcass layer on these bead cores, and to the bead filler. In a pneumatic radial tire in which a bead filler reinforcing layer is arranged alongside, JIS-A hardness of the bead filler is 70
The total cross-sectional area A (mm ² ) of the bead filler, the tire radial height hF (mm) from the bead base of the bead filler, and the tire from the bead base of the bead filler reinforcing layer. Radial height hR
(Mm) is the tire radial height hF (mm) or tire cross-section height SH (mm) of the bead filler, respectively.
On the other hand, A / hF ≦ 3.0 (mm) hF / SH ≧ 0.25 0.5 ≦ hR / hF ≦ 1.0.

[0007] As a result of research on the generation factor of the extremely low frequency band road noise, the present inventors have found that the extremely low frequency band road noise is closely related to the torsion of the sidewall portion in the tire circumferential direction, It was found that the larger the tire circumferential rigidity, the more advantageous the reduction. Further, it is well known that the tire stability in the tire circumferential direction contributes to the steering stability of the tire more than the rigidity in the tire lateral direction. The present invention is
From both such findings, the hardness of the bead filler is set to a specific size, and a reinforcing layer such as a fiber cord or a steel cord is arranged along the bead filler, and the size of the bead filler and the reinforcing layer is determined. By adjusting to 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, it is possible to reduce low-frequency road noise, reduce extremely low-frequency road noise, and ensure steering stability.

The present invention will be described below with reference to the 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 portion,
2 is a sidewall portion, 3 is a bead portion, and 6 is a bead core. The carcass layers 4 and 4 ′ are provided inside and outside two layers at a cord angle of 70 ° to 90 ° with respect to the tire circumferential direction, and the inner carcass layer 4 has both ends 4 e around the bead core 6 inside the tire. Is folded back so as to wrap the bead filler 7 from the outside to the outside carcass layer 4 ′.
Has both end portions 4'e thereof wound down to the heel portion of the bead portion 3 outside the folded-back end portion 4e of the inner carcass layer 4.

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

In the above structure, the bead filler 7 is J
It is made of rubber having an IS-A hardness of 70 to 90. Further, the ratio A / hF of the total cross-sectional area A (mm ² ) to the tire radial height hF (mm) from the bead base B of the bead filler 7 is set to 3.0 (mm) or less, and the tire radial height HF (mm) is the tire cross-section height SH (m
m) is 0.25 times or more, so that the bead filler 7 is as thin as possible and elongated to reduce the vertical spring constant of the sidewall portion and reduce the low frequency road noise. ing. However, if the bead filler 7 is too thin and long and thin, the steering stability cannot be ensured even if the bead filler reinforcing layer 8 described later is provided. Therefore, the tire radial height hF of the total cross-sectional area A (mm ² ). It is preferable that the lower limit of the ratio to (mm) is 2.0 (mm) and the upper limit of the ratio of the tire radial height hF (mm) to the tire cross-sectional height SH is 0.5 (mm).

On the other hand, if the vertical spring constant of the sidewall is simply lowered, the extremely low frequency band road noise is deteriorated and the steering stability is also lowered. As described above, since it is possible to reduce the road noise in the extremely low frequency range and to secure the driving stability by increasing the rigidity in the tire circumferential direction, the radial height hF (m of the bead filler 7 along the bead filler 7 can be reduced.
The bead filler reinforcing layer 8 having a height of 0.5 times or more of m) is arranged. However, if the height hR of the bead filler reinforcing layer 8 from the bead base B in the tire radial direction becomes too large, the effect of reducing the vertical spring constant of the sidewall portion is impaired, so the upper limit of the height hR in the tire radial direction is increased. Is the 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 Tire size is 215 / 65R15 96S, tire structure is FIG. 1, bead filler reinforcing layer is 1 × 5 (0.25)
Common to the tire radial direction height hF of the bead filler A / hF, the ratio of the bead filler tire radial height hF to the tire cross sectional height SH hF / SH, the ratio hR / hF of the tire radial height hR of the bead filler reinforcing layer to the tire radial height hF of the bead filler, and the 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 manufactured.

Further, in the tire 1 of the present invention, a comparative tire 1 having the same structure except that the bead filler reinforcing layer is not provided.
Was produced. 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 ) was mounted on a rim of 15 × 6 1/2 JJ, mounted on a vehicle with a displacement of 4500 cc, and run on a rough road surface at a speed of 50 km / h. 100 in the passenger compartment when
When listening to road noise in the 315 Hz range on the side of the driver's window,
The feeling was evaluated by the 10-point method by the feeling of 5 panelists, and the average value was shown. The higher the score, the lower the road noise.

In addition, the extremely low frequency range road noise is such that the road surface is extremely low frequency range (40 Hz) in the low frequency range road noise.
The same evaluation was performed except that the patch (pavement restoration road) which was easy to evaluate was used. Steering stability : Assembled on the same rim as the road noise test method, mounted test tires filled with the same air pressure on the same vehicle, and steered when running on a slalom test road where pylons were set up at 30m intervals. The sex is evaluated by the 10-point method by the feeling of 5 panelists,
The average value is displayed. The higher the score, the better the steering stability.

[0017] From Table 1, all of the tires 1 to 3 of the present invention have the same or reduced extremely low frequency range road noise while reducing the low frequency range road noise as compared with the comparative tire 1, and have the same or improved steering stability. I am letting you. On the other hand, it is understood that the comparative tires 2 to 5 are incompatible with each other, as compared with the comparative tire 1, either the extremely low frequency band road noise, the low frequency band road noise reduction effect, or the steering stability deteriorates.

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 tire radial height hF of the bead filler was determined.
Only F (1.5 (mm), 2.0 (mm), 3.0)
(Mm) and 3.5 (mm) changed four types of tires were manufactured, and the low frequency road noise of these tires was evaluated. The results are shown in FIG. 2 showing the tire 1 of the present invention (A / hF =
2.5 mm).

From FIG. 2, even if hF / SH satisfies the requirements of the present invention, if A / hF exceeds 3.0 (mm), the longitudinal spring constant of the sidewall portion increases, and the road noise in the low frequency range increases. It turns out that is worse. Example 3 In the tire 1 of the present invention of Example 1, the tire cross-section height S
Four types of tires were prepared in which only the ratio hF / SH of the radial height hF of the bead filler to H was changed to 0.22, 0.25, 0.5, and 0.55, and the extremely low values of these tires were produced. The frequency range road noise was evaluated. The results are shown in FIG. 3 showing the tire 1 of the present invention ((hF / SH = 0.35).
The results are shown together with. From FIG. 3, even if A / hF satisfies the regulation of the present invention, if hF / SH becomes less than 0.25,
Extremely low frequency road noise deteriorates 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, the 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 provided. By adjusting the heights of the tires so that they satisfy specific relationships, it becomes possible to improve the circumferential rigidity of the tire while reducing the vertical spring constant of the sidewalls, thus reducing road noise at low frequencies. While reducing, it is possible to reduce road noise in the extremely low frequency range and at the same time secure driving stability and achieve both.

[Brief description of 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 road noise.

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

[Explanation of symbols]

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

Claims (1)

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