JP3193496B2 - Pneumatic 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 tire having a variable pitch tread pattern, and more particularly, to a pneumatic tire having improved sound quality of pattern noise.

[0002]

2. Description of the Related Art Hitherto, in order to reduce noise caused by a tread pattern of a pneumatic tire, various measures have been taken to disperse the noise in a frequency band as wide as possible. This is called a variable pitch arrangement method based on the frequency modulation theory, in which several types of pitches having different lengths are randomly arranged in the tire circumferential direction, and pulse noise or vibration generated when the elements of each pitch touch the ground. Is variable so that noise is not concentrated on a specific frequency.

As described above, in the above-described variable pitch arrangement method, it was possible to reduce noise (sound pressure level) as a whole. However, even if the sound pressure level dispersed based on the frequency modulation theory is the same on the sound pressure measuring device, the human auditory feeling (ie, sound quality) is obtained.
In some cases, superiority and inferiority occurred.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the sound pressure level by the variable pitch arrangement method.
It is still another object of the present invention to provide a pneumatic tire having a comfortable sound quality for human hearing.

[0005]

In order to achieve the above object, a pneumatic tire according to the present invention is provided with a plurality of pitch rows in which a plurality of pitches having different lengths are arranged in a variable manner in a tire circumferential direction on a tread surface. In a pneumatic tire having a tread pattern, the pitch per tire of the pitch train is subjected to Fourier analysis using a rectangular wave train given at regular intervals according to the arrangement order as a raw function,
Amplitude A for each order HM obtained from this Fourier analysis
M is ^{expressed as follows} : C ₁ in the formula AM = HM ^−C1 × C ₂ is 0.1;
The maximum amplitude value obtained by setting C ₂ to 1.2 and C ₁ to 1
0.0, which as well as to be distributed between the minimum amplitude value obtained for C ₂ as 0.8, characterized in that said base point of each pitch sequence is dispersed at different positions on the circumference of the tire It is.

The inventor of the present invention has investigated the cause of discomfort as the sound quality despite the fact that the sound pressure level has been reduced due to the dispersion of the frequency. As a result, the fluctuation in the sound quality (frequency of sound) was moderate. It has been found that the noise perception to human hearing is improved by giving to the human. That is, a single wavelength (single sound quality) generated by one of the pitch elements constituting the tread pattern is changed with an appropriate fluctuation, and a component in which the timbre changes slowly in a long cycle is allowed. It has been found that it is better to increase the number as much as possible and to reduce the components in which the timbre frequently changes in a short cycle.

In view of the above, when a plurality of types of pitches arranged per one round of the tires in each pitch array as described above are subjected to Fourier analysis using a rectangular wave array arranged at equal time intervals in accordance with the arrangement order as an original function, the amplitude AM of degree (frequency) for each HM, by the amplitude distribution of the frequency inversely proportional type which are distributed between the maximum amplitude value and the minimum amplitude value obtained from the equation AM = HM ^-C1 × C _2, pattern noise Therefore, the unpleasant sound quality caused by the sound is reduced.

Further, in addition to making the plurality of types of pitches in one pitch row an amplitude distribution of a frequency inverse proportion type, by dispersing the base points of each pitch row to different positions on the tire circumference, their pitches can be adjusted. This prevents the occurrence of vibration during rolling of the tire, thereby improving ride comfort. In the present invention, the “pitch” means a minimum unit of a repeated pattern in which a tread design constituting a tread pattern is continuous in a tire circumferential direction. In the case of a block pattern, the length between adjacent blocks; in the case of a rib pattern, the length of the valley-to-valley (or between the ridges) of the zigzag grooves extending in the tire circumferential direction; Correspond to each other.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a developed view showing a tread pattern of a pneumatic tire according to an embodiment of the present invention. In FIG. 1, a tread 1 is provided with a plurality of main grooves 2 extending in a tire circumferential direction and a plurality of sub-grooves 3 extending in a tire width direction, and these main grooves 2 and the sub-grooves 3 form a plurality of blocks. 4 are divided and formed to form four block rows 4a to 4d in the tire circumferential direction. Each of the block rows 4a to 4d has a variable pitch arrangement in which 3 to 8 types of pitches having different pitch intervals P are randomly arranged in the tire circumferential direction. These block rows 4a
4D, the arrangement order of the blocks 4 having a plurality of different pitches is set so as to satisfy the Fourier series expansion described later. Also, as shown in FIG.
Base row of blocks 4a~4d is arranged to distribute the one round length tire position G ₁ ~G ₄ which substantially divided into four equal parts. When there are G rows of pitch rows such as block rows in the tire contact area, the base points of these rows are set to the tire 1.
The perimeter is distributed at an arbitrary position where the perimeter is approximately equal to G.

The block arrangement in the block rows 4a to 4d constituting the tread pattern of the present invention is such that the amplitude AM for each order (frequency) HM obtained by Fourier analysis is of a frequency inverse proportional type as shown in FIG. It has an amplitude distribution. In the Fourier analysis, for example, assuming that the block rows 4a to 4d are configured by randomly arranging four different pitches of pitch intervals A, B, C, and D, the respective pitches are equally-timed according to the arrangement order. A rectangular wave train as shown in FIG. 3 may be arranged at intervals, and this rectangular wave train may be used as an original function.

[0011] Then, the amplitude distribution of the frequency inversely proportional type, its amplitude AM is, in relation AM = HM ^-C1 × C _2, provided by inserting the _{C 1 = 0.1, C 2 =} 1.2 Maximum amplitude value curve X, C ₁ = 10.0, C ₂ = 0.8
To be distributed between the minimum amplitude value curve Y provided. As described above, in the variable pitch tread pattern, a large amplitude AM is distributed in a region where the order HM is small, and a small amplitude AM is distributed in a region where the order HM is large.
Is distributed, it has an inversely proportional amplitude distribution with respect to a frequency proportional to the order HM, so that many components whose sound quality changes slowly over a long period are unpleasant. The sound quality is reduced, and the noise sensation is improved.

The above-described maximum amplitude value curve X and minimum amplitude value curve Y indicate limits for reducing an unpleasant sound quality by forming an inversely proportional amplitude distribution with respect to frequency. As the defined range becomes narrower, the effect of reducing unpleasant sound quality is improved. Therefore, more desirably, the maximum amplitude value curve X is C ₁ = 0.3, C ₂
= 1.2, and the minimum amplitude value curve Y is preferably given by C ₁ = 2.0 and C ₂ = 0.8.

Although each of the block rows 4a to 4d has a periodicity such that a plurality of types of pitches have a frequency inverse proportional amplitude distribution, their base points are dispersed at different positions on the tire circumference. Therefore, it is possible to prevent the occurrence of vibration during rolling of the tire due to their periodicity, and to improve ride comfort. Next, a method of designing a pitch arrangement order that satisfies the above relationship will be described.

As a simple method, an arbitrary arrangement order is designed and it is confirmed whether or not the arrangement order has an inverse frequency type amplitude distribution, so that a pitch row which is a component of the tread pattern of the present invention can be selectively selected. Can be obtained. However, such a method is inefficient in the design work. Therefore, the arrangement order of pitches can be efficiently designed by using a part or all of a random number sequence obtained by converting an inverse Fourier synthesized waveform that satisfies the above relationship into a discrete value. That is, a desired amplitude reduction degree is given, a random number array having a frequency inverse proportional amplitude distribution is obtained, and the order of the array can be set according to the random number array.

In the above-described method of setting the arrangement order based on the random number array having the frequency inverse proportional amplitude distribution, there are N pitches on the tire circumference in one pitch row, and the pitch intervals P _{1 to} P _N are M Assume that they have different lengths L _{1 to} L _M. Then, the degree K at which the amplitude decreases with the frequency is set to a parameter C ₁ = 0.
1 to 10.0, C ₂ = 0.8 to 1.2. Here, i is an order consisting of an arbitrary integer.

[0016]

[Number 1] _{^{K = i -C1 × C 2 ···}} (1) Next, i = 1 to N, sequentially and repeatedly executes the following calculation -. A fixed value of 0 to 1 or an arbitrary random number α is determined. Substituting α and K into the following equations (2) and (3), A _i , B
_Ask for _i .

[0017]

(Equation 2)

[0018]

(Equation 3)

Substituting A _i and B _i into the following equation (4),
Find R _i .

(Equation 4)

R _i and L _k (k = 1 to M) are compared, and L _{k ′} closest to R _i is selected, and this is set as a pitch interval P _i of the i-th pitch. That is, P _i = L _{k ′} . i is incremented by one and ~ is repeated. By the above calculations, the arrangement order can be designed for N pitches in one pitch row.

By varying the random number α variously, another arrangement can be obtained for the same amplitude reduction degree K. This makes it possible to obtain a large number of arrays having a frequency inverse proportional amplitude distribution. In addition, in many arrangements, if a frequency dispersion based on the same frequency modulation theory (variable pitch arrangement method) as in the prior art is selected, not only unpleasant sound quality but also noise as a whole can be reduced. However, it is suitable.

After designing the pitch arrangement order in the tire circumferential direction in one pitch row as described above, the base point of each pitch row is dispersed at different positions on the tire circumference to design the tread pattern of the present invention. be able to.

[0023]

EXAMPLES In order to provide a block pattern composed of four block rows with a tire size of 175 / 70R14, three types of steel radial tires having various types of block pitches and arrangement orders as described below were manufactured. . In the block row of one row of the tire of the present invention , the pitch interval is A = 22.0
mm, B = 25.0 mm, C = 28.0 mm, D = 3
2.0mm, E = 36.0mm
-E were arranged in the following order on the tire circumference, and the base points of each block row were evenly distributed on the tire circumference.

ECBEDCDDCD CCDCDCDCBCB ABCEDCBCBBB BCCDCBCBBB CABBBCBCCB BCCBBAADBB BAABBBBAAB A square wave sequence in which the above arrangement sequence is arranged at equal time intervals is shown in Fig. 5. The result of Fourier analysis using this as an original function is shown in Fig. 6. The amplitude distribution of the Fourier analysis result is
It falls between the maximum amplitude value curve X (AM = HM− ^0.3 × 1.2) and the minimum amplitude value curve Y (AM = HM− ² × 0.8). The kind and arrangement order of the pitch intervals in the block row of one comparative tire were the same as those of the tire of the present invention, and the base point of each block row was set at the same position on the tire circumference. The pitch interval in one block row of the conventional tire is A = 21.3.
mm, B = 24.2 mm, C = 27.1 mm, D = 3
0.9 mm and E = 34.8 mm.
-E were arranged in the following order on the tire circumference, and the base point of each block row was set at the same position on the tire circumference.

ECBDDCAEAD DBDDDDDBBB CAADACAAAEA AABBAACDDDD AAAEDCBABD ECACBDEECE ADDAEDBCBB A rectangular wave train in which the above arrangement sequence is arranged at equal time intervals is shown in Fig. 7. The result of Fourier analysis using this as an original function is shown in Fig. 8. The amplitude distribution of the Fourier analysis result is
It greatly deviates from the maximum amplitude value curve X (AM = HM− ^0.3 × 1.2).

With respect to these three types of tires, the maximum amplitude value, vehicle interior noise, sound quality sensation and ride comfort in the conventional frequency dispersion theory were evaluated by the following method, and the results are shown in Table 1. Maximum amplitude value in the conventional frequency dispersion theory: A trigonometric wave train of the pitch of a block train per tire circle was used as an original function, and this original function was subjected to Fourier analysis to obtain the maximum amplitude value. In addition, according to the conventional frequency dispersion theory, it is considered that the larger the value is, the worse the noise performance is.

In-vehicle noise: Test tires with air pressure of 200 KP
Installed in a 1800cc passenger car as a
The overall sound pressure level at the center of the vehicle when traveling at 0 km / h was measured. Sound quality sensation: In the above vehicle interior noise test, ten test drivers evaluated the sound sensation of tire noise.

Ride comfort: In the above vehicle interior noise test, 1
Riding comfort against vibration was evaluated by zero test drivers. As is clear from Table 1, although the tire of the present invention has the same level of the maximum amplitude value and the in-vehicle noise in the conventional frequency dispersion theory as the conventional tire, the tire of the test driver can obtain good results in the sense of sound quality. Was completed. In other words, it has become clear that it is important for the noise performance of the tire to reduce not only the sound pressure level but also the sound quality. Moreover, in the tire of the present invention, since the base points of the block rows are dispersed on the circumference of the tire, not only the sound quality but also the riding comfort have been improved.

[0029]

As described above, according to the present invention, a pneumatic tire having a tread pattern in which a plurality of pitch rows in which a plurality of pitches having different lengths are arranged in a variable manner in a tire circumferential direction on a tread surface is provided. In the above, Fourier analysis is performed using a rectangular wave train provided by arranging the pitches per tire circumference of the pitch train at equal time intervals in accordance with the arrangement order as an original function, and an amplitude AM for each order HM obtained from the Fourier analysis is obtained. the minimum is determined C ₁ 0.1 in the formula AM = ^HM-C1 × C _2, and the maximum amplitude value determined for C ₂ as 1.2, the C ₁ 10.0, a C ₂ as 0.8 amplitude Values, and by forming an inversely proportional amplitude distribution with respect to frequency, in addition to reducing the sound pressure level by the variable pitch arrangement method, it further reduces human hearing. It is possible to comfortably the sound quality sense of that. In addition, even when the pitch trains have periodicity as described above, the ride comfort against vibration can be improved by dispersing the base points of the pitch trains at different positions on the tire circumference. .

[Brief description of the drawings]

FIG. 1 is a developed view showing a tread pattern of a pneumatic tire according to an embodiment of the present invention.

FIG. 2 is a tire side view showing a base point of each block row dispersed on the tire circumference.

FIG. 3 is a diagram showing an original function obtained by arranging pitch intervals of blocks arranged on one circumference of a tire at equal time intervals according to an arrangement order.

FIG. 4 is a diagram showing a result of Fourier analysis of the original function shown in FIG. 2;

FIG. 5 is a diagram showing an original function obtained by arranging pitch intervals of blocks arranged on one circumference of the tire according to the present invention at equal time intervals according to an arrangement order.

FIG. 6 is a diagram showing a result of Fourier analysis of the original function shown in FIG. 5;

FIG. 7 is a diagram showing an original function obtained by arranging pitch intervals of blocks arranged on one circumference of a conventional tire at equal time intervals according to an arrangement order.

8 is a diagram showing a result of Fourier analysis of the original function shown in FIG. 7;

[Description of sign]

 4 blocks 4a to 4d Block train HM order AM amplitude X maximum amplitude value curve Y minimum amplitude value curve

Claims (1)

(57) [Claims] 1. A pneumatic tire having a tread pattern provided with a plurality of pitch rows in which a plurality of types of pitches having different lengths are arranged in a variable manner in a tire circumferential direction on a tread surface. Pitch
Fourier analysis is performed using square wave trains arranged at equal time intervals in accordance with the arrangement order as original functions, and the amplitude AM for each order HM obtained from the Fourier analysis is expressed by the equation AM =
Between C ₁ and 0.1 in ^HM-C1 × C _2, and the maximum amplitude value determined for C ₂ as 1.2, the C ₁ 10.0, and the minimum amplitude value obtained for C ₂ as 0.8 And the base points of the pitch rows are dispersed at different positions on the tire circumference.