JPH09300909A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a vibrating characteristic, particularly load noise in a low frequency area, without causing cost increase and tire weight increase. SOLUTION: A pneumatic radial tire is provided with a radial carcass 1 formed of cord plies toroidally arranged between a pair of bead parts, and a reinforcing belt part is provided along the periphery of a crown part of the radial carcass 1. The radius of curvature R1 of a carcass line 1a with the center of curvature on the inside in a tire maximum width position A, in a no-load self-supported position of standard internal pressure of 0.3Kg/cm<2> at the time of being assembled to a normal rim is to be 10-25mm, and the radius of curvature R2 of the carcass line 1a positioned in a buttress part area B near the width end of a maximum width belt in the belt part is to be infinity from 150mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of vibration characteristics, particularly road noise in a low frequency range, in a pneumatic radial tire suitable for passenger cars and the like.

[0002]

2. Description of the Related Art Road noise is mainly 80 to 160 Hz.
Noise in the low frequency region in the vicinity and noise in the high frequency region above 200 Hz are known. One of the causes of occurrence is that tires pick up disturbances on the road surface while driving a passenger car or the like. By the way, conventionally, to significantly improve this road noise, increase the rubber thickness of the tread,
Various modifications have been made to the tire structure, such as increasing the cross-sectional width of the tire.

[0003]

However, when the tire structure is changed by increasing the rubber thickness of the tread or enlarging the sectional width of the tire, not only the cost is increased but also the weight of the tire is increased. At the same time, the rolling resistance deteriorates. Further, once the shape of the mold profile is determined, it is often difficult to improve road noise, particularly low-frequency road noise, with the tire structure.

An object of the present invention is to provide a pneumatic radial tire having improved vibration characteristics, particularly road noise in a low frequency range, without increasing costs and increasing tire weight. A further object of the present invention is to provide a pneumatic tire having improved road noise in the high frequency region as well as road noise in the low frequency region.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has adopted a carcass shape in a sidewall portion of a tire having a cross-sectional structure that is more easily bent than a conventional tire. We obtained the knowledge that road noise performance, especially road noise performance in low frequency region, can be improved.

That is, the invention of claim 1 is provided with a radial carcass consisting of cord plies arranged in a toroidal shape between a pair of bead portions, and a reinforcing belt portion is provided along the periphery of the crown portion of the radial carcass. In the pneumatic radial tire, at the tire maximum width position A, the radius of curvature R ₁ of the carcass line with the center of curvature as the inner side is configured by a small radius that makes the tire sectional primary rigidity low. It is a featured pneumatic radial tire. Here, the small radius which makes the tire cross-section primary rigidity low rigidity means that the carcass shape in the sidewall portion of the tire adopts a cross-sectional structure that is more easily bent than a conventional tire, and specifically, As described in claim 2, a standard internal pressure of 0.3 when mounted on a regular rim.
This can be achieved by setting the radius of curvature R ₁ of claim 1 in an unloaded self-supporting posture of Kg / cm ² to a small radius within the range of 10 to 25 mm from the conventional large radius of 40 to 50 mm.

As a result, the carcass tension at the tire maximum width position A becomes lower than in the conventional case, the primary rigidity of the tire cross section becomes low, and the low frequency region, particularly 80 to 160H.
Road noise in z and its vicinity can be reduced. If the radius of curvature R ₁ exceeds 25 mm, the effect of improving road noise in the low frequency region cannot be sufficiently obtained. If R ₁ is less than 10 mm, the primary rigidity of the tire cross section becomes too low, which is not preferable in terms of tire durability and steering stability.

Further, in the tire of the present invention, the carcass tension at the tire maximum width position A is low, so that the carcass tension is relatively high near the buttress portion region B near the width end of the maximum width belt. The secondary rigidity of the tire cross section becomes higher, and the high frequency region, especially around 200 Hz or higher, of which around 250 Hz to 400 Hz, and further 250 H
It is possible to reduce road noise of z to 315 Hz. In particular, when the radius of curvature R ₂ located in the buttress portion region B near the width end of the maximum width belt and having the center of curvature inside is 150 mm to infinity (that is, a straight line) as in the invention of claim 3. , The same radius of curvature R ₂ to R ₁
Unlike the radius of curvature of 40 to 50 mm which is almost the same as or about 100 mm at the maximum, the above-mentioned high frequency region,
In particular, the effect of reducing the road noise at 250 to 315 Hz is remarkable. According to the invention of claim 3, the curvature is located in the buttress portion region B in the vicinity of the width end of the maximum width belt of the belt portion in an unloaded self-supporting posture with a standard internal pressure of 0.3 kg / cm ² when mounted on a regular rim. The pneumatic radial tire according to claim 1 or 2, wherein the radius of curvature R ₂ with the center inside is 150 mm to infinity. When the radius of curvature R ₂ is less than 150 mm, the secondary rigidity of the tire cross section is almost the same as that of the conventional tire, and the road noise in the high frequency region is not sufficiently improved.

It is desirable that the carcass shape having the radius of curvature R ₂ be continuous with the carcass shape having the radius of curvature R ₁ to form a carcass line. By doing so, the road noise in the high frequency region can be simultaneously improved together with the road noise in the low frequency region. However, the present invention is not limited to this, and the carcass shape having the radius of curvature R _{2 is changed to} the carcass shape having the radius of curvature R ₁ under the condition of being located in the buttress portion region B near the width end of the maximum width belt. There is no problem even if the carcass line is formed discontinuously.

In the present invention, the "tire maximum width position A" is used.
Means that the maximum tire width is used as a reference for the radius of curvature R ₁ , but the present invention is not limited to this and may be used as a reference for the radius of curvature R ₁ including the area in the vicinity thereof. Further, in the present invention, the specific dimensions of the radius of curvature R ₁ and the radius of curvature R ₂ are specified based on an unloaded self-supporting posture with a standard internal pressure of 0.3 Kg / cm ² when assembled to a regular rim. Needless to say, in other cases, the numerical value fluctuates according to the other criteria.

[0011]

1 is a schematic half sectional view showing an embodiment of a pneumatic radial tire according to the present invention. In the figure, 1 is a radial carcass consisting of cord plies arranged in a toroidal shape between a pair of bead portions 2, 3
Is a reinforcing belt portion arranged along the circumference of the crown portion of the radial carcass 1. 4 is a tread portion, 5 is a bead core, and in the present embodiment, both end portions in the tire width direction of the radial carcass 1 are respectively folded around the bead core 5 from the tire inner side toward the tire outer side.

In the tire of the present embodiment, at the tire maximum width position A, the radius of curvature R ₁ of the carcass line 1a having the center of curvature as the inner side is constituted by a small radius which makes the tire sectional primary rigidity low. . Specifically, the radius of curvature R ₁ of the carcass line 1a in an unloaded self-supporting posture with a standard internal pressure of 0.3 kg / cm ² when assembled to the regular rim is 1
It has a small radius within the range of 0 to 25 mm.

Further, the tire of this embodiment has a buttress in the vicinity of the width end 6 of the maximum width belt 3a in the reinforcing belt portion 3 in the unloaded self-supporting posture with the standard internal pressure of 0.3 Kg / cm ² when mounted on the regular rim. The radius of curvature R ₂ located in the partial region B and having the center of curvature inside is 150 mm
~ Infinite.

In the tire of this embodiment, since the carcass tension at the tire maximum width position A is lower than that of the conventional tire, the primary rigidity of the tire cross section becomes low, and the low frequency region, particularly 80 to 160 Hz and its vicinity. Road noise in the area can be reduced. In the high frequency region, especially 250
The effect of reducing road noise at ˜315 Hz also appears prominently.

FIG. 2 is a schematic half sectional view showing an example of a conventional tire. As shown in the figure, the conventional tire has a standard internal pressure of 0.3 kg / cm ² when mounted on a regular rim.
In the unloaded self-supporting posture, the radius of curvature R ₁ of the carcass line 1a with the center of curvature inside is 40 to 50 mm, and the radius of curvature R ₂ with the center of curvature inside is about 40 to 50 mm. Has become. The reference numerals in the figure are the same as those shown in the above embodiment.

[0016]

Example: The radius of curvature R ₁ is 25 mm, the radius of curvature R is
Tire size 195 / 65R15 with _{2 set} to 150mm
A radial tire for a passenger car of 91H shown in FIG. 1 was prototyped, road noise was measured, and the improvement effect of the road noise was tested. Further, the radius of curvature R ₁ is 10 mm, the radius of curvature R _{2 is}
Is also infinite (indicated by a straight line) and the same size tire is also tested. The radius of curvature R ₁ and the radius of curvature R ₂
Both are based on an unloaded self-supporting posture with a standard internal pressure of 0.3 kg / cm ² when assembled on a regular rim. For comparison, a passenger car radial tire of FIG. 2 having a radius of curvature R ₁ of 55 mm and a radius of curvature R ₂ of 60 mm and having the same size as that of the above-described embodiment was similarly manufactured, and road noise was similarly measured. . Further, a tire having a radius of curvature R ₁ of 30 mm and a radius of curvature R ₂ of 100 mm was also tested.

FIG. 3 is a graph showing measurement results of road noise from low frequency to high frequency. The horizontal axis represents the vibration region (Hz), and the vertical axis represents the vibration intensity (dB (A)).

As shown in FIG. 3, in the low frequency region, particularly 63-
180Hz range, especially high vibration intensity range 8
It is recognized that the road noise is reduced over the range of 0 to 160 Hz as compared with the conventional tire.
Moreover, it is recognized that the road noise is reduced in the high frequency region, particularly in the range of 230 to 800 Hz, particularly in the range of 250 to 315 Hz where the vibration intensity is large, as compared with the conventional tire.

Next, a feeling evaluation test was conducted on each of the tires of the above-mentioned examples and comparative examples. Table 1 shows the results. In addition, the same test condition was applied to each tire in air pressure 2.
0Kg / cm ² , rim 15 × 6JJ, mounted on a normal passenger car, with 2 passengers in the front seat, test speed 60km / h
The actual vehicle was run, and 10 points were given as a perfect score, and the test was repeated twice, and the average score of 2 people was given to evaluate the overall score. Also, in the road noise feeling test, the noise that is perceived by the human ear as a go sound is a noise in the low frequency range of 80 to 160 Hz, and the noise that is perceived by the human ear as a gar sound is a high frequency of 250 to 315 Hz. This is the noise of the area.

[0020]

[Table 1]

From Table 1, it can be seen that the tire of this embodiment has an effect of reducing road noise in both the low frequency region and the high frequency region as compared with the conventional tire.

[0022]

Industrial Applicability The present invention is provided with a radial carcass comprising cord plies arranged in a toroidal shape between a pair of bead portions, and a pneumatic belt having a reinforcing belt portion along the circumference of the crown portion of the radial carcass. In the radial tire, at the tire maximum width position A, the radius of curvature R ₁ of the carcass line having the center of curvature as the inner side is a pneumatic radial tire configured by a small radius having low primary rigidity in tire cross section. Therefore, it is possible to improve vibration characteristics, particularly road noise in a low frequency region, without increasing costs and increasing tire weight as in the conventional case.

In particular, in a no-load self-standing posture with a standard internal pressure of 0.3 kg / cm ² when mounted on a regular rim, the radius of curvature R _{1 at the} carcass line is 10 to 25.
mm, maximum width of the belt portion, located in the buttress portion region B near the width end of the belt, the radius of curvature R ₂ is 150 mm
In the case of a tire that is infinite, the road noise is improved in the low frequency range of 80 to 160 Hz, and at the same time,
Particularly, the road noise of 250 to 315 Hz can be improved at the same time.

[Brief description of drawings]

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

FIG. 2 is a schematic half sectional view showing an example of a conventional tire.

FIG. 3 is a graph showing measurement results of road noise from low frequencies to high frequencies.

[Explanation of symbols]

 1 Radial carcass 1a Carcass line 2 Bead part 3 Reinforcement belt part 3a Maximum width belt 4 Tread part 5 Bead core 6 Width edge A Tire maximum width position B Buttress area

Claims (3)

[Claims] 1. A pneumatic radial tire having a radial carcass consisting of cord plies arranged in a toroidal shape between a pair of bead parts, and a reinforcing belt part along the circumference of the crown part of the radial carcass. At the tire maximum width position A, the radius of curvature R ₁ of the carcass line having the center of curvature as the inner side is constituted by a small radius which makes the tire section primary rigidity low rigidity. . 2. The pneumatic radial tire according to claim ₁ , wherein the radius of curvature R ₁ of claim ₁ is ₁₀ to 25 mm in an unloaded self-standing posture with a standard internal pressure of 0.3 Kg / cm ² when mounted on a regular rim. . 3. The center of curvature, which is located in the buttress portion region B near the width end of the maximum width belt in the belt portion, in the unloaded self-supporting posture with the standard internal pressure of 0.3 kg / cm ² when mounted on the regular rim. Inside radius of curvature R ₂
Is 150 mm to infinity, The pneumatic radial tire according to claim 1 or 2.