JP2665931B2 - Pneumatic tire - Google Patents

Description

Description: TECHNICAL FIELD [0001] The present invention relates to a tire having a plurality of tread design elements having different pitch lengths arranged on a tread surface, and a noise generated by the tread design elements as the tire rolls. The present invention relates to a pneumatic tire with reduced (pattern noise).

(Prior art)

Conventionally, in order to reduce the pattern noise, various measures have been taken to disperse the pattern noise in a wide frequency band around the pitch frequency (frequency determined by the number of rotations of the tire × the number of tread design elements) to make the noise inconspicuous. This is called a variable pitch arrangement method, in which several types of tread design elements (that is, pitches) having different pitch lengths are appropriately arranged in the circumferential direction of the tire, and when each tread design element comes into contact with the ground contact surface. This is a method of changing the time interval between pulse noises or vibrations generated at the same time so that noises do not concentrate on a specific frequency, and is based on a frequency modulation theory used in wireless engineering and the like. However, it has not yet been possible to sufficiently reduce the pattern noise.

Then, the present inventor studied to reduce the pattern noise, and as a result, it was found that the pulsation of the sound pressure level could not be overlooked as a factor that deteriorated the tire noise feeling. In other words, although the sound pressure level averaged over a certain period of time is the same as in the conventional noise measurement method, the sound pressure sensation may be superior or inferior to the human sense of hearing. Investigation of the cause revealed that the difference was between a sound pressure level that greatly pulsated and a sound pressure level that did not pulsate in a low frequency band of about 10 Hz or less. In order to quantitatively observe the pulsation of the sound pressure level, that is, the pulsation which is one of the factors of the noise, the noise recorded at a high speed is reproduced at a low speed and the temporal change of the sound pressure level is measured. It is possible by outputting.
For example, a method according to the JASO C606-73 tire noise test method, that is, a tire is mounted on a steel drum having a diameter of 3000 mm.
Roll at 50km / h (air pressure, rim size, load is JATMA
OA value (overall value of noise passing through a band-pass filter of 100 to 2000 Hz)
Can be evaluated by the fluctuation width within one rotation of the tire.

On the other hand, in the conventional theory of tread design element arrangement for sound pressure level, it is assumed that one sine wave is generated from one tread design element, and the same time as the arrangement order of tread design elements is arranged on one circumference of the tire. In general, sine wave trains generated at intervals are Fourier-series expanded to simulate dispersion on the frequency axis. In particular, there are many theoretical analyzes in the case of regularly sine wave arrangement from a tread resin element having a short circumferential length, that is, a pitch length, to a long tread design element, and also to a short tread design element. Researches and contrivances have been made (for example, see “Techniques for automobile tires”, Vol. 28, No. 1, 1974, see JP-A-54-115801). But,
In these considerations, the pulsation of the sound pressure level described above is not discussed because the magnitude of vibration generated from each tread design element is assumed to be constant.

The inventors of the present invention have paid attention to the fact that when the circumferential length of a tread design element is large, the vibration level generated from the element increases, and tried theoretical calculations under the following assumptions. That is, the vibration generated from each tread design element undergoes Fourier series expansion on the assumption that it is a sine wave having a large amplitude in proportion to the circumferential length of the tread design element. As a result, FIGS. 8 (a) and (b) and FIGS. 9 (a) and (b)
As shown in FIG. 8, if it is assumed that a sine wave of an equal size is generated from each tread design element by the conventional calculation method, no vibration is exhibited in a low frequency band as shown in FIG. Assuming that a sine wave having an amplitude commensurate with the pitch length of the element is generated, as shown in FIG. 9 (b), the peak of the amplitude in a low frequency band corresponding to the special cycle number of the tread design element array is obtained. Can be seen. In particular, when the tread design element arrangement is a regular arrangement, the peak in this low frequency band becomes remarkable, thereby increasing the pulsation of the sound pressure level and deteriorating the noise feeling.

8 (a) and 9 (a) are explanatory diagrams each showing a pitch arrangement (tread design element arrangement). 2 indicates a vibration waveform. 8 (b) and 9 (b) are diagrams showing the relationship between the order and the amplitude corresponding to the order when Fourier analysis is performed. 8 (a) and 9 (a), the pitch length of pitch A = 31.7 mm, the pitch length of pitch B = 27.5 mm, the pitch length of pitch C = 24.5 mm, the pitch group E ₁ = CCCCCC, the pitch group
E ₂ = BBBBBBBB, pitch group E ₃ = AAAAAAA, pitch group E ₄ = BBB
B, pitch group E ₅ = CCCCCC, pitch group E ₆ = BBB, pitch group E ₇
= AAAAAA, pitch group E ₈ = BBBBBBB, pitch group E ₉ = CCCCCCC
CC, pitch group E ₁₀ = BBBB, pitch group E ₁₁ = AAAAA, and pitch group E ₁₂ = BBBB. The pitch arrangement shown in FIG.
This is the same as the pitch arrangement in FIG. Here, “pitch” generally means the minimum unit of the repeating pattern, which is a tire tread design that is configured as a repeating pattern that is continuous in the circumferential direction. The “pitch group” means a portion of the pitch in which the same pitch is continuously arranged.

[Object of the invention]

The present invention is intended to reduce the pulsation of the sound pressure level by improving the configuration and arrangement of the pitch, and the product of the length of each pitch and the number of the pitches appearing on the tire circumference is specified. Accordingly, an object of the present invention is to provide a pneumatic tire in which pattern noise is reduced to improve the comfort and comfort of a vehicle.

[Configuration of the invention]

Therefore, the present invention is the conjunction constitute one round of the tread surface in 3-8 different pitches having different lengths, the length of the pitch of the i th kind of types of these pitches and P _i the total number of pitches appears in one round tire and N _i, each pitch type allocations _{α i α i = (p i} × N i) / tires and the entire circumference, and the number of types of pitches lengths NP In the case, (1) the horizontal axis is the pitch length and the vertical axis is α _i , and α of the longest pitch is (1 / NP) × 0.2 to (1 / NP)
And the minimum pitch length α is (1 / NP) ~
(1 / NP) × 1.8, and connect these α to L
An L 'line is formed, and α _i exists within a range obtained by increasing or decreasing α by ± 10% with respect to the LL' line, or (2) the horizontal axis is the pitch length and the vertical axis is α _i The above (1)
Is the longest pitch and the shortest pitch α for the LL 'line determined in
The α of the shortest pitch next to the longest pitch and the longest pitch next to the shortest pitch is 4 to 30% smaller than that determined by the LL ′ line.
% By connecting the determined by increasing alpha 'is formed and the polygonal line ll' polyline ll pneumatic, characterized in that alpha _i is present in a range obtained by increasing or decreasing ± 10% of alpha against The gist is a tire.

 Hereinafter, the configuration of the present invention will be described in detail.

The present inventor has made various calculations on the above-described pulsation of noise, that is, low frequency components in an arrangement in which the pitch size changes regularly. As a result, it was found that the total number of pitches appearing on the circumference of each pitch was one important factor. As shown in FIGS. 1 (a) and (b), FIGS. 2 (a) and (b), FIGS. 3 (a) and (b), and FIGS. Length 48mm, 44mm, 40
Using five types of pitches of mm, 36 mm and 32 mm, the total number N _i of each pitch appearing on the circumference was calculated as shown in Table 1 below.

As a result, since the regularity of the arrangement is two periods for one round of the tire, a secondary peak appears when Fourier series is developed, and this peak becomes smaller as the intermediate pitch increases. On the other hand, looking at the appearance of a peak near the pitch frequency (near the order of the total pitch number), when the shortest and longest pitches are increased, the components near the center of the pitch frequency are reduced, and peaks appear on both sides. However, when the intermediate pitch is increased, a peak occurs near the center of the pitch frequency. From the above, it is considered that there is an appropriate value in the number distribution of each pitch that minimizes the pitch noise. Moreover, from the characteristics of Fourier series expansion, it is considered that not the arrangement of the number of pitches but the time ratio occupied by each pitch, that is, the ratio of pitch length × pitch number is important.

From the above logical background, the present inventor considers that the smaller the ratio of the length to the entire circumference of each pitch is, the larger the ratio is, and that the ratio of the shortest and longest pitches is smaller than other pitches, the lower It was concluded that both the component related to pulsation and the component related to the pitch frequency were improved in a well-balanced manner.
The present invention has been made based on such findings.

(1) In the present invention, one round of the tread surface is configured with 3 to 8 types of pitches having different lengths.

The greater the number of types of pitches, the more advantageous in reducing noise, but the greater the number of pitches, the higher the cost of mold production. Therefore, three to eight types are taken into account in consideration of this balance.

(2) Further, in the present invention, the total number of said pitch appears in one round tire with the length of the pitch of the i th kind of types of these pitches and P _i and N _i, of each pitch type The component ratio α _i is defined as α _i = (p _i × N _i ) / tire circumference,
When NP is the number of pitch length types, one of the following or one of the following is used.

Assuming that the horizontal axis is the pitch length and the vertical axis is α _i , the length α of the longest pitch is defined as (1 / NP) × 0.2 to (1 / NP), and α of the shortest pitch is (1 / NP) to (1 / NP)
X is set between 1.8 and these α are connected to form the LL 'line, and α _i exists within the range obtained by increasing or decreasing α by ± 10% with respect to the LL' line.

FIG. 5 shows the relationship between the pitch length and α _i . In FIG. 5, m is the upper line (10% α is larger than LL ′), n is the lower line (10% α is smaller than LL ′), P ₁ is the longest pitch length,
_np is the shortest pitch length, alpha ₁ is the longest pitch length of the alpha value, alpha
_np is the α value of the length of the shortest pitch. In FIG. 5, α _i exists in the hatched portion 1.

The larger the pitch, the larger the vibration emitted from each pitch. Therefore, the component emitted from the large pitch becomes stronger in the frequency dispersion of noise. That is, α _i
If the values are equalized, the component on the low frequency side corresponding to a large pitch becomes strong, so that the frequency dispersion is biased, and as a result, the peak of noise increases. Therefore, by reducing the α of the large pitch and increasing the α of the small pitch, the frequency dispersion becomes uniform for the first time, and the noise peak becomes the minimum value. The distribution of each pitch of α is 0 to 80% larger than the equal distribution (1 / NP) at the shortest pitch length P _np (between (1 / NP) and (1 / NP) × 1.8), and the longest pitch length 0 to 80 than the uniform distribution (1 / NP) in the P ₁
% (Between (1 / NP) × 0.2 and (1 / NP)). If it is out of this range, on the other hand, components having small pitches become too large, and a uniform frequency distribution cannot be obtained.

With the horizontal axis being the pitch length and the vertical axis being α _i , the longest pitch and the shortest pitch α for the LL ′ line defined above
Is 4 to 30% smaller than that determined by the LL ′ line, and α of the shortest pitch next to the longest pitch and the next longest pitch after the shortest pitch is 4 to 30% smaller than that determined by the LL ′ line.
% By connecting the determined by increasing alpha 'is formed and the polygonal line ll' polyline ll be alpha _i is present in a range obtained by increasing or decreasing ± 10% of the alpha respect.

FIG. 6 shows the relationship between the pitch length and α _i . In FIG. 6, g is the upper polygonal line (10% α is larger than ll ′), h is the lower polygonal line (10% α is smaller than ll ′), P ₁ is the longest pitch length, and P _np is This is the shortest pitch length, and LL 'is the LL' line in FIG. In FIG. 6, α _i exists in the hatched portion 1.

In the sixth view, next to the long pitch length P _np-1 of P ₂ ~ shortest pitch next shortest pitch length of the longest pitch, ll 'is LL' 4 to 30% than the larger. Longest pitch length
For P ₁ and the shortest pitch length P _np , ll ′ is 4 to 3 more than LL ′.
0% smaller.

In consideration of the pulsation of low frequency, if α of the longest pitch length P ₁ and the shortest pitch length P _np is reduced, the change in the level of the vibration emitted from each pitch is relatively reduced, and the pulsation is improved. However, if α of P ₁ and P _np is too small, the maximum / minimum ratio of the pitch becomes substantially small, and the pitch noise worsens. For this reason, for P ₁ and P _np , ll ′ is made 4 to 30% smaller than LL ′. Also,
For pitches other than P ₁ and P _np , the pitch is increased by 4 to 30% by the amount corresponding to the reduction of P ₁ and P _np .

(3) Next, a specific example of the method of calculating the pitch distribution in the present invention will be described below.

First, as with the conventional pitch design method, the maximum pitch length /
The ratio β of the minimum pitch length and the total pitch number N are determined.
To improve the tire noise, it is better to increase both N and β, but it is desirable to select from β = 1.3 to 1.8 and N = 40 to 90 from other characteristics of the noise. Suppose N = 57, β = 1.54
Choose

Next, the length of each pitch is determined from the outer diameter of the tire and N and β. Here, when a calculation is made for a tire having an outer diameter D of 600 mm, this is converted into an integer from D × π ÷ N = 33.07, and the length of the intermediate pitch is set to 33 mm.

Next, the number of pitch types is determined. The number of types is 3 to 8 types as described above. Here, there are five types.

When designing five types of pitch lengths with β = 1.54 and intermediate pitch length = 33 mm, the difference between the longest to middle and middle to shortest pitches is k, and (33 + k) / (33−k) = β = 1.54 to k = 7, get the longest 40, the shortest 26. The remaining three types should be filled in appropriately, and eventually 40, 36, 3
Choose a pitch length of 3, 29, 26mm.

As a reference for pitch distribution, the distribution ratio α _i of each pitch is firstly determined because there are five types of pitches.
Based on (1/5) = 0.2, the reference distribution, that is, the MM 'line to which each pitch should be distributed equally as shown in FIG. 7, is determined.

Next, as shown in FIG. 7, an intersection C1 between the middle between the longest pitch length and the shortest pitch length and the MM 'line, and A1 or E1, the LL' line that increases the distribution as the pitch becomes shorter, Determine. Point A1 is on a vertical line with a minimum pitch length of 26 mm, 13.5% higher than the equal distribution α = 0.2, and is given by α = 0.227. When the LL 'line is determined in the case of the longest pitch length of 40 mm, it is on the vertical line of the longest pitch length of 40 mm, and the equal distribution α = 0.
12.5% lower than 2, obtained by connecting the E1 and C1 points given by α = 0.175.

In this way, the LL 'line is determined by increasing or decreasing the α at the shortest or longest pitch by 0% to 80% from the equal distribution, but when the slope is down to the left (decreasing at the shortest pitch, decreasing at the longest pitch) Increase), the influence of the longer pitch is too large, and a large peak is generated on the frequency side of the pitch frequency. On the other hand, if the inclination is more than 80%, the influence of the shorter pitch is too strong, and a large peak is generated on the high frequency side of the pitch frequency.

When the LL 'line is determined in this manner, a second reference distribution is obtained from the intersection of each pitch length and the LL' line. As shown in FIG. 5, if A, B, C, D, and E are set in order from the shortest one, the value of α is determined as A1, B1, C1, D1, and E1 as follows ( α _i is the second reference allocation). If there is a deviation of more than 10% from the second reference distribution, there is no noise reduction effect.

α _i A1 0.227 B1 0.218 C1 0.200 D1 0.190 E1 0.175 Next, paying attention to low frequencies, the ratio of the longest and shortest pitches is reduced, and the ratio of the intermediate pitches is increased. At the longest pitch, E1 = 0.175 from 14.75% reduced to E2 = 0.15, at the shortest pitch A1 = 0.227 to 9.7% reduced from A2 = 0.205, and
The intermediate pitch was increased by 12.5% from C1 = 0.200 to C2 = 0.225.

In this way, the pulsation at low frequencies can be improved by decreasing the minimum pitch by 4% to 30% from the second reference distribution and increasing the intermediate pitch by 4% to 30%. If it is less than 4%, the effect of improving pulsation cannot be substantially obtained, and if it exceeds 30%, dispersion at the pitch frequency becomes insufficient.

The remaining two pitches are designed so as to take the middle between the increase and decrease values on both sides. That is, in pitch B, pitch A is reduced by 9.7% and pitch C is increased by 12.5%, so that there is no change. In pitch D, pitch C is reduced by 12.5%.
Since the pitch E is 14.3% decreased, the pitch distribution α _i is determined as follows (α _i ′ is α _i).
Adjustment value). If the total sum of α _i does not reach 1.0, each α _i is adjusted in proportion.

α _i α _i ′ A2 0.205 0.2054 B2 0.218 0.2184 C2 0.225 0.2255 D2 0.200 0.2004 E2 0.150 0.1503 Total 0.998 1.0000 Using α _i ′ determined above, the number of each pitch can be obtained as follows.

N _i = perimeter × α _i / pitch length P _i Therefore, the pitch length, α _i , N _i , and N _i ′ (integralization of N _i ) are as follows. As a result, the number distribution of each pitch is determined based on the total pitch number slightly larger than the total pitch number 57 provisionally initially determined. Pitch length _{(mm) α i N i N} i 'A 26 0.2054 14.9 15 B 29 0.2184 14.2 14 C 33 0.2255 12.9 13 D 36 0.2004 10.5 10 E 40 0.1503 7.1 7 wherein the adjustment of the pitch. That is, in the number distribution of each pitch determined above, Σ (P _i × N _i ) / π
= 593.6, which does not match the tire circumference (600mm) (593.6 <600), so the pitch length is adjusted in proportion.
Since 600 ÷ 593.6 = 1.0108, the final pitch length is obtained by multiplying this by the respective pitch lengths tentatively determined initially. The values are shown below. P _i ′ is obtained by adjusting the pitch length P _i . Pitch Pitch length (mm) P _i ′ α _i A 26 26.3 0.2092 B 29 29.3 0.2175 C 33 33.4 0.2303 D 36 36.4 0.1930 E 40 40.4 0.1500 Examples are shown below.

Example A steel radial tire (external tire, comparative tire) having an outer diameter of 600 mm and a tire size of 165SR13 was evaluated for noise pulsation width (dB) and noise feeling. Table 2 shows the results.

Evaluation method of noise pulsation width: A method according to the JASO C606-73 tire noise test method, that is, a tire is driven at 50 km / h on a steel drum having a diameter of 3000 mm.
(The air pressure, rim size, and load are JATMA standard conditions), and the pulsation was evaluated based on the fluctuation range of the OA value (overall value of noise passing through a bandpass filter of 100 to 2000 Hz) within one rotation of the tire. .

As can be seen from Table 2, the comparative tire 1 has a large distribution of the shortest and longest pitches, and therefore has high dispersion of pitch noise and low-order pulsation, and is not practical. In the comparative tire 2, the larger the pitch is, the more the distribution is. In the comparative tire 3, the distribution of each pitch is almost equally divided, and α = 0.2 ± 10%. Therefore, the dispersion of pitch noise is relatively good, the low-order pulsation is improved, and the tire is practically usable. In the tire 1 of the present invention, the shorter the pitch, the more the distribution, the more the distribution is 25% than the equal distribution at the A pitch, the less 25% than the equal distribution at the E pitch, and the smaller the distribution from the A to the E pitch. Therefore, both the dispersion and the pulsation of the pitch noise are further improved as compared with the comparative tire 3. The tire 2 of the present invention has a distribution that is 13% larger than the equal distribution at the A pitch and 13% smaller than the equal distribution at the E pitch,
Furthermore, the ratio of C pitch is increased by 13%, and the ratio of A, E pitch is
0-14% reduced and allocated. For this reason, pitch noise is kept relatively good, and pulsation is most significantly improved.

〔The invention's effect〕

As described above, in the tire noise in which the pitch stiffness increases according to the pitch length and the pitch vibration generated from each pitch fluctuates with the pitch size, the pitch arrangement method determines the distribution ratio of each pitch. Is an important problem.In the present invention, the distribution of pitch noise and the improvement of pulsation can be improved by equally dividing each pitch distribution or distributing more pitches for shorter pitches or reducing the distribution of longest and shortest pitches. It becomes possible to measure.

[Brief description of the drawings]

FIGS. 1 (a) and (b), FIGS. 2 (a) and (b), FIGS. 3 (a) and (b), and FIGS. 4 (a) and (b) each show a pitch arrangement, It is explanatory drawing which showed the relationship between the order when Fourier analysis was performed, and the amplitude corresponding to the order. Figure 5, Figure 6, and 7 is an explanatory diagram showing the relationship between the composition ratio alpha _i of the pitch length and pitch, respectively. 8 (a) and 9 (a) are explanatory diagrams each showing a pitch arrangement, and FIGS. 8 (b) and 9 (b) respectively correspond to the order and the order when Fourier analysis is performed. FIG. 5 is an explanatory diagram showing a relationship between the amplitude and the amplitude. 1 ... shaded area, 2 ... vibration waveform.

Continuation of the front page (56) References JP-A-61-200006 (JP, A) JP-A-1-4501 (JP, A) JP-A-63-13410 (JP, A) JP-A-62-155106 (JP, A) JP-A-60-139504 (JP, A) JP-A-60-88606 (JP, A) JP-A-60-88605 (JP, A) JP-A-60-82408 (JP, A) 54-115801 (JP, A) JP-A-63-22703 (JP, A) JP-B-58-2844 (JP, B2) JP-B-3-23366 (JP, B2)

Claims (1)

(57) [Claims] [Claim 1] constitute one round of the tread surface in 3-8 different pitches having different lengths, is the pitch with the length of the pitch of the i th kind of types of these pitches and P _i the total number of occurrences in one round tire and N _i, and each pitch type allocations _{α i α i = (p i} × N i) / tire entire circumference,
In the case of the NP and the number of kinds of pitch length, (1) as the pitch length Toshikatsu ordinate the horizontal axis alpha _i, the longest pitch length of the alpha (1 / NP) × 0.2 to (1 / NP ) And the shortest pitch length α is (1 / NP)-(1 / NP) x 1.8
Between these α, forming the LL 'line by connecting these α,
Α _i exists within the range obtained by increasing or decreasing α by ± 10% with respect to the LL ′ line, or (2) the horizontal axis is the pitch length and the vertical axis is α _i , The α of the longest pitch and the shortest pitch is 4 to 30% smaller than that determined by the LL ′ line for the determined LL ′ line, and α of the shortest pitch next to the longest pitch and the longest pitch next to the shortest pitch is LL ′
The line α is determined by connecting α between 4% and 30% larger than that determined by the line to form a polygonal line ll ′, and α _i is within a range obtained by increasing or decreasing α by ± 10% with respect to the polygonal line ll ′. A pneumatic tire characterized by being present.