JPH10100614A - Low noise tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire suppressing its noise low. SOLUTION: In a tread pattern formed repeating the same pattern, pitch variation is applied using n-kinds (n>=3) of pitch length Pi so as to have the whole pitch number Nt of 30-90 on the periphery of a tire. The ratio of maximum pitch length Pn to minimum pitch length P1 is 1.3-1.6, and the ratio of the number Ni of each pitch length Pi to Nt/n is 0.6 or more. When the number of combinations pipj of different kinds of pitches on the periphery out of kinds of connection of circumferentially adjacent pitches is made Kij, (Kij+Kji)/ Nt<=17% and (Kij+Kji)/(Ni+Nj)<=40% are satisfied, and when the number of minimum pitch length P1 is made N1 and the number of combinations P1P1 of circumferentially adjacent minimum pitch length on the periphery is made K11, 10%<=K11/Nt<=30% and 35%<=K11/N1<=65% are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire having a tread pattern formed by repeatedly arranging the same pattern on the circumference to reduce noise.

Here, the term used in the present specification will be described. "Pitch variation" is a method of reducing tire noise (pattern noise) based on frequency modulation theory and the like, and is a minimum unit constituting a pattern. By making the circumferential length (pitch) of the pattern of two or more types and arranging them appropriately continuously on the circumference of the tire tread, when arranged at one type of pitch, it concentrates on a certain frequency. This is a technique for reducing tire noise (pattern noise) by dispersing the peak of a large sound pressure level generated by the above operation into many sideband waves having lower sound pressure levels.

[0003]

2. Description of the Related Art A pneumatic tire provided with a tread pattern formed by repeatedly arranging the same pattern on the circumference,
Since noise of a specific frequency is generated by the frequency of the repetition, it is required to reduce noise (pattern noise). Pitch variations are known as a technique for reducing tire noise (pattern noise) and have been put to practical use. As a pitch variation method, a method of randomly arranging several types of pitch lengths using a random number table or the like, and a method of arranging several types of pitch lengths evenly on the circumference have been attempted. However, there is a problem in that noise is generated when the antennas are arranged randomly, and when the antennas are arranged relatively evenly on the periphery, noise of a new frequency (pattern noise) is generated. In addition, if the maximum pitch length and the minimum pitch length are unevenly arranged on the circumference, there is a problem that the tread weight becomes uneven on the circumference, thereby deteriorating the uniformity and causing abnormal wear.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a tire which solves the above-mentioned disadvantages of the prior art and suppresses the tire noise (pattern noise).

[0005]

Means for Solving the Problems To achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire having a tread pattern formed by repeatedly arranging the same pattern on the periphery. (1) The tread pattern has n kinds (n is 3 or more) of pitch lengths Pi (i = 1, 2).
.. N), the pitch variation is given on the circumference of the tire, and the tire has a total pitch number Nt of 30 to 90 pieces,
(2) The ratio between the maximum pitch length Pn and the minimum pitch length P1 is 1.3 to 1.6, and the number Ni of each pitch length Pi (i = 1,
..N) and Nt / n are not less than 0.6, and (3)
Among the types of connection of adjacent pitches on the circumference, (i ≠ j, i, j =
When the number on the circumference of (1,... N) is Kij, (K
ij + Kji) / Nt ≦ 17% and (Kij + Kji)
/ (Ni + Nj) ≦ 40%, (4) The number of minimum pitch lengths P1 is N1, and the number of combinations P1P1 of the minimum pitch lengths adjacent in the circumferential direction on the circumference is K1.
10% ≦ K11 / Nt ≦ 30% and 35% when 1
<K11 / N1 ≦ 65% is adopted.

In the present invention, since the number Ni of each pitch length is set to be 0.6 times or more the value obtained by dividing the total number Nt by the pitch type n, the arrangement may be biased toward a specific pitch length. As a result, neither uniformity nor abnormal wear occurs.

[0007] Further, since the upper limit is set on the arrangement ratio of specific different pitches adjacent in the circumferential direction, noise of a specific frequency generated from the specific different pitch is not generated, and a large sound pressure level is not generated. The peak can be spread over many sidebands at lower sound pressure levels. Since the range of the ratio of the minimum pitches adjacent to each other in the circumferential direction is defined, the sound has an appropriate fluctuation in sound quality and is easy to hear.

Here, the ratio of the maximum pitch length Pn to the minimum pitch length P1 is set to 1.3 to 1.6 because the effect of pitch variation is small at 1.3 or less, and the sound pressure level is reduced to a sideband wave. It cannot be sufficiently dispersed, and if it is 1.6 or more, the sound quality fluctuates too much and the sound becomes hard to hear, and the difference between the maximum pitch length and the minimum pitch length is too large to make the appearance worse or abnormal. It is not preferable because it causes abrasion. Preferably, when the ratio of the maximum pitch length Pn to the minimum pitch length P1 is 1.42 to 1.48, the dispersion effect and the sound quality improvement effect can be balanced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The tire according to the embodiment of the present invention and the tire according to the prior art will be described. The size of each tire is 225 / 60R16. The tread pattern is such that 66 caramel blocks are arranged in four rows on the circumference in the tire axial direction. As shown in Table 1, four types of pitch lengths are used, the longest pitch length P4 and the shortest pitch length P1.
Is set to 1.46, and P2 and P3 in the middle are set to equal ratios. These tires have exactly the same structure except for the pitch arrangement.

[0010]

[Table 1]

The pitches P1 to P4 in Table 1 were arranged on the circumference of the tread in the following combinations. The numbers are
It is shown corresponding to P1 to P4. ("Conventional example" 21
23231131213133131342131342
3144322121211314212111231
1134421112244), (“Example 1” 21
2323114111413141134211342
3134432122111411314212111231
11334421112244), (“Example 2” 22
232311311111311134211342
333443221111211314212111231
11344421112244). Table 2 shows the results of analysis based on the method of the present invention for combinations of different pitches and combinations of minimum pitches according to this arrangement.

[0012]

[Table 2]

According to Table 2, in the conventional tire, the number of combinations of the minimum pitch is out of the range of the present invention, and the number of combinations (12, 21) and (13, 31) among the combinations of It can be seen that it is outside the scope of the invention.

Next, in order to confirm the effect of the present invention, these tires were mounted on a 7J × 16 rim with an internal pressure of 2.2 kgf / c.
assembled in m ^2, and is attached to the European 4WD passenger car of 4000cc, was tested under the conditions of 2 passengers. The noise was evaluated by a sensory test at a position 7.5 m away from the vehicle when the vehicle meandered at a speed of 55 km / h on a straight road. As a result of the evaluation, the tire of Example 1 was evaluated to be +2 points superior to the conventional tire, and the tire of Example 2 was evaluated to be +1 points superior to the conventional tire. Here, it is a score that clearly shows the difference from +2 points,
One point is a score that half of the general public can point out the difference. At the same time, evaluation by db (A) was also performed.
All tires were about 68.9 db (A), and the difference in sound pressure itself could not be clearly detected. Furthermore, running feeling was evaluated by running at high speed including a curve, and all of the tires of the examples showed a better feeling than the tires of the conventional example.

[0015]

As described above, according to the present invention, it is possible to provide a tire having a low noise level and a good running feeling.

Claims (1)

[Claims] 1. A pneumatic tire having a tread pattern formed by repeatedly arranging the same pattern on the circumference, (1) the tread pattern has n kinds (n is 3 or more) of pitch lengths Pi (I = 1,... N), pitch variation is given, and 30 to 9
0 total pitch number Nt, (2) maximum pitch length P
The ratio between n and the minimum pitch length P1 is 1.3 to 1.6, and the ratio between the number Ni (i = 1,... n) of each pitch length Pi and Nt / n is 0.6 or more, (3) Among the types of connection of pitches adjacent in the circumferential direction, when the number of combinations PiPj of different pitches on the circumference of (iｎj, i, j = 1,... N) is Kij. , (Kij + Kji) / Nt ≦ 17% and (Kij + Kj)
i) / (Ni + Nj) ≦ 40%, (4) When the number of the minimum pitch lengths P1 is N1, and the number on the circumference of the combination P1P1 of the minimum pitch lengths adjacent in the circumferential direction is K11. 10% ≦ K11 / Nt ≦ 30% and 35% ≦ K11 / N1
A low-noise tire characterized by satisfying ≦ 65%.