JPH05320423A - Pneumatic low-noise tire - Google Patents

Abstract

PURPOSE:To provide a pneumatic low-noise tire capable of simultaneously reducing load noise and noise caused by passing vehicles without detriment to control stability. CONSTITUTION:The tread rubber of this tire simultaneously satisfies the relationships: Hs<=12XM100+29 and 45<=Hs<=75 wherein Hs is the JIS hardness of the rubber at 25 deg.C, and M100 is the stress of the rubber at 100% elongation and at 25 deg.C, the unit of the M100 being MN/m<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for an automobile using a tread rubber which significantly lowers a noise level, and particularly to running of an automobile without limiting the tread pattern and / or the tire structure. Accordingly, the present invention relates to a low-noise pneumatic tire in which vehicle interior noise (mainly road noise) generated from the tire and passing noise outside the vehicle are simultaneously reduced.

[0002]

2. Description of the Related Art Conventionally, a lot of improvement techniques have been proposed as noise generated from a tire while a vehicle is running makes a passenger uncomfortable and impairs habitability. The noise of the tires to be improved is roughly classified into so-called pattern noise, which is mainly caused by the pattern provided on the tread, and so-called road noise, which is caused by the bump input on the tire tread due to the unevenness of the road surface.

Regarding the pattern noise among the above noises, by disposing various grooves provided on the tread or devising the shape, the frequencies showing at least a high peak value among the frequency components of the noise are dispersed, and all the frequencies of the noise are dispersed. A pattern noise reduction technique is known in which the decibel value dB (A) over the band is leveled and the generation of a specific frequency exhibiting an unpleasant high peak is suppressed.

A technique for reducing road noise is disclosed in, for example, Japanese Patent Laid-Open No. 61-231038, and this disclosed technique proposes a tread rubber for tires having excellent wear resistance and damping characteristics. In addition to other road noise reduction technology, with the aim of simultaneously improving steering stability,
JP-A-1-16850 proposes a pneumatic radial tire in which the hardness of the tread rubber and the constitution of the belt layer are combined.
There is No. 6 publication.

[0005]

Although the above pattern noise reduction technology has certainly contributed to noise improvement, it is a major social problem for vehicles that are required to be greatly improved with the remarkable increase in traffic volume today. There has been a limit to seeking a means for further reducing the passing noise to a desired degree only by operating the tire pattern. This is because it is practically impossible to further reduce noise while maintaining various performances required for tire patterns such as slip resistance, steering stability, and wear resistance at a certain level. It's nothing but a problem.

Among the above disclosed techniques, Japanese Patent Laid-Open No. 61-2310
No. 38 publication improves the damping characteristics of the tread rubber by lowering the hardness and the dynamic elastic modulus of the tread rubber and making the value of the loss tangent relatively large, which causes road noise that is a problem as vehicle interior noise. Could be improved. However, as described above, it is impossible to improve the exterior noise, that is, the passing noise, which is required to be urgently improved as a social problem, and there is a problem that the passing noise is deteriorated.

Further, the above disclosed technology is disclosed in Japanese Patent Laid-Open No. 16850/1989.
No. 6 publication can improve the vehicle interior noise (road noise) by lowering the hardness of the cap tread rubber and specifying the configuration of the belt layer, but it is impossible to improve the passing noise like the above-mentioned disclosed technique. Yes, there was a problem that this worsens in some cases. This will be described in detail later, but if the hardness of the tread rubber is lowered, including the technique of JP-A-61-231038, the modulus (or stress) at the time of 100% elongation at the time of large deformation of the rubber is also lowered. This is because the decrease in modulus (or stress) acts to increase the level of passing noise. At the same time, the disclosed technique has a problem in that it limits the structure and shape of the tire, resulting in narrowing the degree of freedom in design.

Therefore, the object of the present invention is to freely select the shape and structure including the tread pattern of the tire, to secure desirable performances such as good vehicle steering stability, and to prevent road noise and passage. The object of the present invention is to propose a low noise pneumatic tire equipped with a tread rubber capable of simultaneously reducing noise and sufficiently responding to strong social demands for improvement.

[0009]

In order to solve the above problems at the same time, in the low noise pneumatic tire of the present invention, the rubber composing the tread has a JIS hardness at 25 ° C of Hs, and its rubber hardness is 25 °. The stress under 100% elongation in C is M _100, and the unit of this M ₁₀₀ is MN / m ²
When (MN is meganewton), the following equations, Hs ≦ 12 × M ₁₀₀ +29, 45 ≦ Hs ≦ 75, are simultaneously satisfied.

In a preferred embodiment of the present invention said Hs
And the above M ₁₀₀ can be a tread rubber that satisfies the following equation: Hs ≧ 20 × M ₁₀₀ −15.

Hereinafter, a compounding example of the tread rubber used in the tire of the present invention will be described more specifically with reference to FIG. 1 and Table 1. Fig. 1 shows J at the vertical axis of 25 ° C.
Hs of IS hardness and stress M ₁₀₀ (MN / m ² ) at 100% elongation at 25 ° C. on the horizontal axis, the Hs and M ₁₀₀ of the compounding example tread rubber according to the present invention shown in Table 1 below.
It is the figure which plotted the value of (MN / m < ² >), and the numerical value of illustration is the formulation example No. of Table 1. Corresponds to the value of.

In FIG. 1, the tread rubber used in the low-noise tire of the present invention has a JIS hardness Hs of Hs = 75 ° indicated by h ₁ and a straight line parallel to the abscissa and Hs = h ₂ indicated by h _2.
A straight line H indicated by L ₁ is a value within a region surrounded by a 45 ° straight line and the relationship between the Hs value and the M ₁₀₀ value.
It is desirable to fit in the area on the right side of FIG. 1 from s = 12 × M ₁₀₀ +29 (portion shown by a part of the diagonal line in the figure). The value of the Hs and M ₁₀₀ are intended to include points on each straight line of the three. Also, the constant 29 is the extension of the straight line L ₁ is H
It is the value at the point of intersection with the s-axis.

In a further preferred embodiment, the relationship between the value of Hs and the value of M _{100 in} the above area shown in FIG. 1 is limited to a straight line Hs = 20 × M ₁₀₀ −15 indicated by L ₂ , and this straight line It is preferable to fit in the area on the left side of FIG. Even in this case, the above two values include points on the straight line. The constant − (minus) 15 is the value of the intersection of the virtual extension line of the vertical axis Hs in FIG. 1 and the straight line L ₂ .

Table 1 shows the compounding examples of the tread rubber used in the low noise pneumatic tire of the present invention. 1 to No. 7, the tread rubber in the above region of the present invention is, for example, as shown in Table 1, solution-polymerized SBR.
It is obtained by blending a rubber mainly composed of synthetic rubber such as the above with a crosslinking agent in a larger amount than usual, for example, sulfur shown in Table 1. The values of the compounding agents in Table 1 are parts by weight based on 100 parts by weight of rubber. In addition, Table 1 also shows compounding examples of the tread rubbers of the conventional example and the comparative example.

Hs and M shown in Table 1₁₀₀Each value is
According to the measuring method according to JIS-K6301, Hs is 2
The hardness measured by JIS A in an atmosphere of 5 ° C.
R, M ₁₀₀Is a dumbbell-shaped No. 3 test piece in an atmosphere of 25 ° C
The stress at 100% elongation is measured using
/ M²It is represented by. MN is Mega Newton
Is. The same applies to the above.

[0016]

[Table 1]

Formulation No. of Table 1 1 to No. Each rubber shown in 7 is a rubber used for the tread of the low noise pneumatic tire of the present invention. These tread rubbers are provided on a radial carcass of 1 ply or more and on the outer peripheral side of the carcass, and a reinforcing steel cord or It is suitable for use in a pneumatic radial tire having two or more belt layers made of other reinforcing organic fiber cords and a tread arranged further on the outer peripheral side of the belt layers. Furthermore, when using the tread rubber of the present invention, the thickness of the product tire is 60% or more of the groove depth having the maximum groove depth among the grooves provided in the tire tread, and the tread rubber is used as a tire radius. It is desirable to arrange it outside in the direction. The low noise pneumatic tire of the present invention is not limited to the carcass having the radial structure but can be used for the bias structure.

[0018]

First of all, road noise is caused by the tire tread acting as if it hits the road surface, and the vibration noise of the tread portion and the vibration noise of the sidewall portion generated at this time are given. Next, the vibration of the tread portion becomes an exciting force having a specific frequency on the vehicle body through the sidewall portion, and this force causes noise that resonates with a specific portion of the vehicle and emits a sound. Therefore, although a small amount of this road noise is generated even on a smooth road surface, due to the mechanism, the noise level is rather high when traveling on an uneven road surface, which is serious.

The reduction of the road noise can be improved by adopting a pattern in which the compressive rigidity of the tread portion defined by the groove provided in the tread is reduced in terms of the pattern from the mechanism of its generation. However, this means is not desirable because it causes uneven wear resistance and lower steering stability. In the present invention, the hardness Hs of the tread rubber at 25 ° C. is within a certain range, that is, 45 ° ≦ Hs ≦ 75.
By making it as small as °, it is possible to absorb a considerable amount of vibration energy applied to the tread portion, and on the other hand, it is possible to improve road noise. Where Hs is 4
If it is less than 5 °, the steering stability of the vehicle is significantly deteriorated and it is not practical, and if it exceeds 75 °, the absorption and relaxation of vibration energy that generates road noise is insufficient and the object of the present invention cannot be achieved. Occurs.

Although the road noise can be reduced by lowering the hardness of rubber as described above, according to the prior art,
At the same time, the stress at the time of 100% elongation of this rubber also decreases, and this decrease in stress simultaneously increases the sound pressure level of passing noise or the energy of sound, and cannot achieve the main object of the present invention. The reason is as follows

The main energy of passing noise is that each groove for patterns provided on the tread is grounded, and when the grounded state is separated, the tread rubber is crushed in the direction of the force received by the tread in the grounded state and each groove is Generated by so-called air pumping action, in which the air in each groove is once compressed and then released as a result of a series of actions that reduce their volume and restore the volume of those grooves when released from the grounded state. To do. The degree to which each groove is crushed is greater as the hardness of the rubber is lower.Therefore, the level of the passing noise of the tire using the low-hardness tread rubber becomes higher. is there.

In the present invention, for example, solution polymerization SBR
By blending a rubber mainly composed of a synthetic rubber, etc., and a crosslinking agent in a larger amount than usual, for example, sulfur, the tread rubber has the same hardness as the JIS hardness Hsc of the conventional tread rubber. It solved the problem of the antinomy by using a tread rubber having a stress at 100% elongation M ₁₀₀ c or more similar stress M ₁₀₀ to the pneumatic tire. That is, in the conventional tread rubber,
In the range of 5 ≦ Hs ≦ 75, at most 12 × M
_{The range of 100} + 29 <Hsc ≦ 12 × M ₁₀₀ c + 40 is achievable, and the simultaneous reduction of both the level of road noise and the level of passing noise, which is the object of the present invention, cannot be achieved.

The Hs is (12 × M₁₀₀Over +29)
Sufficient suppression of road noise with tread rubber in different areas
This is not preferable because the following problem occurs. Also the preferred implementation
As an example, Hs ≧ 20 × M₁₀₀-15 is preferable
The reason is that Hs <20 × M ₁₀₀-15 area tread
Rubber makes the rubber brittle, and the tread is
It is not desirable because it may cause rubber chipping.
It

[0024]

[Example] Formulation No. shown in Table 1 1 to No. Tread rubbers up to 7 were used for pneumatic radial tires for passenger cars of size 175 / 70R13. There are two belt layers, which are steel cord reinforcement. Carcass uses polyester cord as its reinforcement cord 2
It is a radial carcass of ply. The tire of the example is N
o. 1 to No. Seven types of tires up to 7 were prepared.
In addition, tire No. Are shown in Table 1.

In order to confirm the levels of road noise and passing noise of the tires of the respective examples, the tire N of the conventional example is used.
o. No. 8 and Comparative Example tire No. 9 to No. Three types of tires up to 11 were prepared. The tires of the conventional example and the comparative example are No. 1 shown in Table 1 above. 8 to No. Using the tread rubber of the compounding example of No. 11, except for these tread rubbers, the other tires were the same as the tires of the examples. No. in Table 1 Was adapted to. Incidentally, the JIS hardness of the tread rubber of Table 1 in the conventional example and Comparative Examples Hs, the stress at 100% elongation shown by M _100. 2 is a graph in which the values of JIS hardness Hs and stress M ₁₀₀ (MN / m ² ) at 100% elongation of the tread rubbers shown in Table 1 of these conventional examples and comparative examples are additionally plotted in FIG. Indicates. The numerical values shown in FIG. Corresponds to.

The tires of the above-mentioned respective examples, the tires of the conventional examples and the tires of the respective comparative examples were used as test tires, and these tires were used for all front-wheel drive passenger cars having an air pressure of 2.0 kgf / cm ² and a displacement of 1.5 liters. It was attached to a wheel and road noise and passing noise were measured and evaluated by the following test methods. For these noises, the dB (A) value of the sound pressure level was used.

First, the road noise is 60k on the test vehicle.
The vehicle was run on a rough uneven road surface provided on a test course at a constant speed of m / h, and the noise in the vehicle at that time was picked up and measured by a microphone installed near the driver's window side ear. Passing noise was measured by performing a test according to the actual vehicle coasting test method defined by JASO C606. Table 2 shows these measured noise levels dB (A). In Table 2, the value of the tire noise dB (A) of the conventional example is set to 0 (zero) as a reference, and the noise dB (A) values of the other test tires describe the difference from this reference value, + (plus) ) Indicates an increase in noise amount, and- (minus) indicates a decrease in noise amount. In addition, Table 2 shows the Hs and M ₁₀₀ of each rubber in duplicate for reference.

[0028]

[Table 2]

As is clear from Table 2, the tires of the respective examples were compared with those of the conventional example in No. It can be seen that the passing noise is remarkably improved except for the tire of No. 5. In addition, No. The tire of No. 5 has significantly improved road noise while maintaining the sound pressure level of passing noise equal to that of the tire of the conventional example, and this tire sufficiently meets the demand for reducing road noise without sacrificing passing noise. It is a tire to get. Incidentally, No. The tire No. 1 is a tire having a significantly improved passing noise without sacrificing the sound pressure level of road noise. On the other hand, tire No. 10 and No. No. 11 is a tire that cannot be put to practical use because the sound pressure level of the passing noise is greatly increased although the road noise is greatly reduced, and the tire is not practically used.

[0030]

According to the present invention, it is possible to reduce road noise and passing noise at the same time and sufficiently meet strong social demands for improvement. At the same time, the shape and structure including the tread pattern of the tire can be freely set. It is possible to provide a low-noise pneumatic tire that can be selected as described above and that can ensure good vehicle steering stability.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between the JIS hardness of a tread rubber of a low noise pneumatic tire according to the present invention and a stress at 100% elongation.

FIG. 2 is a diagram in which values of similar hardness and similar stress of a conventional tire and a comparative tire are added to FIG.

[Explanation of symbols]

L ₁ straight line, Hs = 12 × M ₁₀₀ +29 L ₂ straight line, Hs = 20 × M ₁₀₀ −15 h ₁ straight line, Hs = 75 h ₂ straight line, Hs = 45

Claims (2)

[Claims] 1. The rubber constituting the tread is at 25 °
The JIS hardness and Hs in C, and the stress under 100% elongation at the 25 ° C and M _100, the M ₁₀₀
When the unit of MN / m ² (MN is meganewton) is satisfied, the following expressions, Hs ≦ 12 × M ₁₀₀ +29, 45 ≦ Hs ≦ 75, are satisfied at the same time. 2. The pneumatic tire according to claim 1, wherein the Hs and the M ₁₀₀ satisfy the following equation: Hs ≧ 20 × M ₁₀₀ −15.