JPH01285406A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To reduce pattern noise and to improve living condition and amenity by forming one round of a tread surface by plural kinds of pitches having different lengths, and making a specified combination of the products of the length of each pitch and the number of pitches appearing in one round of a tire. CONSTITUTION:At the time of forming one round of a read by three to eight kinds of pitches, wherein the pitch length is Pi, the total number of appearing pitches is Ni, the construction ration of the respective pitches is expressed by alphai=PiXNi, and the number of kinds of pitch lengths is expressed by NP, the longest pitch alpha is set within the range of (1/NP)X0.2-1/NP, and the shortest pitch alpha is set within (1/NP)-(1/NPX1.8), and alphai is set within the range of + or -10% with respect to a line LL' connecting both alpha as shown in the drawing. The longest and shortest pitches alpha are made smaller by 4-30% than that decided by LL'. The second rank pitch alpha is set larger by 4-30%, and set within the range of + or -10% with respect to a kinked line ll' connecting them. Thus, pattern noise can be reduced.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a tire in which tread design elements having a plurality of different pitch lengths are arranged on the tread surface, and which reduces the noise ( This invention relates to a pneumatic tire that reduces pattern noise.

[Prior art]

Conventionally, in order to reduce pattern noise, efforts have been made to make the noise less noticeable by dispersing the pattern noise into a wide frequency band around the pitch frequency (a frequency determined by the number of tire rotations x the number of tread design elements). This is called the barrier pull pitch arrangement method, in which tread design elements with different pitch lengths (i.e., pinches) are arranged appropriately in the circumferential direction of the tire, and each tread design element makes contact with the ground contact surface. This is a method to prevent noise from concentrating on a specific frequency by changing the time interval of the pulsed noise or vibration that occurs when the noise is generated, and is based on frequency modulation theory used in radio engineering. However, pattern noise has not yet been sufficiently reduced.

Therefore, as a result of research aimed at reducing pattern noise, the present inventor found that the pulsation of the sound pressure level cannot be overlooked as a factor that worsens the feeling of tire noise.

In other words, even though the sound pressure levels averaged over a certain period of time as in conventional noise measurement methods are the same, there may be differences in the perceived sound pressure in the human hearing room. , when we investigated the cause of this, we found that approximately 1
It has been found that there is a difference between a sound pressure level that pulsates significantly and a sound pressure level that does not pulsate in a low frequency band below 0 Hz. In order to quantitatively observe the pulsation of this sound pressure level, which is one of the causes of noise, the noise recorded at high speed is played back at low speed to observe the temporal changes in the sound pressure level. For example, it is possible by outputting 6
A method similar to ASOC606-73 tire noise test method, i.e., tires were transferred at 50 km/h on a steel drum with a diameter of 3000 mm (inflate pressure, rim size,
Load is JATMA standard condition), pulsation evaluation is OA value (
It can be evaluated based on the overall value of the noise that has passed through a band-pass filter of 100 to 2000 Hz) within one rotation of the tire.

On the other hand, in the conventional theory regarding the arrangement of tread design elements regarding sound pressure level, it is assumed that one sine wave is generated from one tread design element, and the time period in one tire rotation is the same as the arrangement order of the tread design elements. Generally, dispersion on the frequency axis is simulated by expanding a sine wave train that occurs at intervals into a Fourier series. In particular, a lot of theoretical analysis has been done regarding the regular sine wave arrangement of tread design elements with short circumferential length, that is, pitch length, from short tread design elements to long tread design elements, and then back to short tread design elements. Research and innovations are being carried out (for example, Automotive Technology Vol. 1.28, Nll,
1974 ``About Tire Noise'', Japanese Patent Publication No. 1974-
(See Publication No. 115801). However, in these considerations, the reason why the above-mentioned pulsating nature of the sound pressure level is not discussed is because the magnitude of vibration generated from each tread design element is assumed to be constant.

The present inventor focused on the fact that when the circumferential length of a tread design element is large, the vibration level generated from that element becomes large, and attempted theoretical calculations based on the following assumptions. That is, the vibration generated from each tread design element is expanded into a Fourier series 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, it is assumed that a sine wave of equal size is generated from each tread design element using the conventional calculation method, as shown in FIGS. 8(a), (b) and 9(a), (b). Then, as shown in Fig. 8(b), no vibration appears in the low frequency band, but if it is assumed that a sine wave with an amplitude commensurate with the pitch length of the tread design element is generated, as shown in Fig. 9(b). ), the amplitude peak is seen in a low frequency band corresponding to a particular number of cycles of the tread design element arrangement. In particular, when the tread design elements are arranged in a regular manner, the peak in this low frequency band becomes noticeable, which increases the pulsation of the sound pressure level and worsens the feeling of noise.

FIG. 8(a) and FIG. 9(a) are explanatory diagrams showing the pitch arrangement (tread design element arrangement), respectively. 2 shows a vibration waveform. Figures 8(b) and 9
Figure <b) is a relationship diagram between the order and the amplitude corresponding to the order when Fourier analysis is performed. 8th
In Figures (a) and 9(a), the pitch length of pitch A = 31.7 mm, and the pitch length of pitch B = 27.
5 + am, pitch length of pitch C = 24.5 mm
, pitch group E+ =CCCCCC, pitch group Ez =B
BBBBBBBB, pitch group E3 tiumaaaaaa, pinch group E.

=BBBB, pitch group Es　”　CCCCCC.

Pitch group E = BBB, pitch group E = AAAAAA,
Pitch group E@ =BBBBBBBB.

Pitch group E 9 = CCCCCCCCCC, pitch group E,. =BBBB, pitch group E r + = A A
A AA1 pitch group E, t = B B B B.

The pitch arrangement in FIG. 8(a) and the pitch arrangement in FIG. 9(a) are the same. Here, the term "pitch" refers to the smallest unit of a repeating pattern of a tire tread design that is generally continuous in the circumferential direction. Furthermore, the term "pitch group" refers to a portion of the pitches in which the same pitches are consecutively arranged.

[Purpose of the invention]

The present invention was made to reduce the pulsation of the sound pressure level by improving the structure and arrangement of pitches, and the product of the length of each pitch and the number of tires in which that pitch appears is made into a specific combination. The purpose of the present invention is to provide a pneumatic tire that reduces pattern noise and improves the comfort and comfort of automobiles.

[Structure of the invention]

Therefore, in the present invention, one circumference of the tread surface is made up of three to eight types of pitches having different lengths, and the length of the i-th type of pitch among these types of pitches is defined as P. Let Ni be the total number of pinches that appear in one tire lap,
The composition ratio αi of each pitch type is αm = (PtXNi)/
When the entire circumference of the tire is the entire circumference of the tire and NP is the number of pitch length types, (1) the horizontal axis is the pitch length and the vertical axis is α5, and the longest pitch length α is (1/NP) × 0 ．．
LL' (2) If the horizontal axis is the pitch length and the vertical axis is α5, The α of the longest pitch and the shortest pitch with respect to the LL' line defined in (1) is 4 to 30% smaller than that determined by the LL' line, and the next shortest pitch after the longest pitch and the second longest pitch after the shortest pitch α of pitch
is determined by 4 to 30% larger than that determined by the LL' line to form a polygonal line 11', and within the range obtained by increasing or decreasing α with respect to this polygonal line 11' by ±lO%. The gist of this invention is a pneumatic tire characterized by the presence of αi.

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

The present inventor attempted various calculations regarding the pulsation of the noise described above, that is, the low frequency components in an arrangement in which the pitch size changes regularly. As a result, it was found that one important factor was the total number of pitches appearing on the circumference of each pitch. Figure 1 (a), (b), Figure 2 (
As shown in FIGS. 3(a), (b), and 4(a), (b), the pitch length is 48.
mm, 44 mm, 40 am, 36
nu++.

Using five types of pitches of 32IllII+, the total number Ni in which each pinch appears on the same page was calculated by varying it as shown in Table 1 below.

(Margins below this page) As a result of Beniko, since the regularity of the arrangement is two cycles per tire rotation, a quadratic peak appears when expanded into a Fourier series, and this peak becomes smaller as the intermediate pitch increases. Become.

On the other hand, looking at the peaks that appear near the pinch frequency (near the order of the total pitch number), as the shortest and longest pitches are increased, the component near the center of the pitch frequency decreases, and peaks appear on both sides. However, when the intermediate pitch is increased, a peak occurs near the center of the pinch frequency.

From the above, it is considered that there is an appropriate value for the distribution of the number of pitches that minimizes pitch noise. Furthermore, from the characteristics of Fourier series expansion, it is considered that not the arrangement of the number of each pitch but the time ratio occupied by each pitch, that is, the ratio of pitch length x number of 1,000 pins is important.

Based on the above theoretical background, the present inventor believes that pitches whose ratio of length to the total circumferential length of each pitch is small has a large ratio, and if the ratio of the shortest and longest pitches is smaller than the others, the pitch is of low order. It was concluded that both the pulsation-related components and the pitch frequency-related components were improved in a well-balanced manner. The present invention has been made based on such knowledge.

(11) In the present invention, one circumference of the tread surface is composed of three to eight types of pitches having different lengths.

The greater the number of pitches, the more advantageous it is to reducing noise, but the greater the number of pitches, the higher the cost of mold production, so in consideration of this balance, three to eight pitches were selected.

(2) Furthermore, in the present invention, the length of the i-th type of pitch among these pitch types is P.

Let the total number of pitches that appear in one circumference of the tire be N□, and the composition ratio αi of each pitch type is α = = (
When P i ×N (positive)/entire circumference of the tire and NP is the number of types of pitch lengths, either of the following (■) or (■) is adopted.

■ The horizontal axis is the pitch length and the vertical axis is α.

Then, the longest pitch length α is (1/NP) x 0.2
〜(1/NP), and the shortest pitch length α is determined between (1/NP)〜(1/NP)×1.8.
These α are connected to form the LL' line, and this LL
' within the range obtained by increasing or decreasing α by ±10% with respect to the line.
i must exist.

FIG. 5 shows the relationship between pitch length and αi.

In Figure 5, m is the upper line (α is 10% larger than L L'), and n is the lower line (α is 10% smaller than L L').
, P is the longest pitch length, P□ is the shortest pitch length, αi is the α value of the longest pitch length, αi, , is the α value of the shortest pitch length. In FIG. 5, αi exists in the shaded area 1.

The vibrations emitted from each pitch are the larger the pitch. Therefore, in the frequency dispersion of noise, components emitted from large pitches become stronger. In other words, if α5 is made equal, the low frequency components corresponding to large pitches will become stronger, resulting in biased frequency dispersion.
As a result, the noise peak becomes larger. Therefore, by reducing α of the large pitch, α of the small pitch is
By increasing , the frequency dispersion becomes even and the noise peak becomes its minimum value. The distribution of each pitch of this α is equal distribution with the shortest pitch length P np (1/NP)
θ ~ 80% more combs than ((1/NP) ~ (1/NP)
xl, between 8) and the longest pitch length P, evenly distributed (1/
θ~80% less than ((1/NP)
×0.2 to (1/NP)). If it is outside this range, on the contrary, there will be too many small pitch components, making it impossible to obtain an even frequency distribution.

■ If the horizontal axis is the pitch length and the vertical axis is αi, then the longest pitch and the shortest pitch α are 4 to 30% smaller than those determined by the LL' line determined in (■) above, and the longest pitch is The next shortest pitch after the shortest pitch and the second longest pitch after the shortest pitch are determined by α being 4 to 30% larger than the one determined by the LL' line, and then the polygonal line E is connected.
l' and set α to ±1 for this polygonal line 11".
αi exists within the range obtained by increasing or decreasing by 0%.

FIG. 6 shows the relationship between pitch length and α5.

In Figure 6, C is 10% lower than the upper polygonal line (/Il').
α is larger), h is 6% of the lower fold (lO than i!/'
%α is small), Pi is the longest pitch length, P7 is the shortest pitch length, and LL' is the LL' line in FIG.

In FIG. 6, α3 exists in the shaded area 1.

In Figure 6, the length P of the next shortest pitch after the longest pitch
2 to length of the next longest pinch after the shortest pitch P, %l, -8
About 17!゛ is 4 to 30% larger than LL'. Regarding the longest pitch length P8 and the shortest pitch length P, 1
1' is 4 to 30% smaller than LL''.

Considering low frequency pulsation, the longest pitch length PI, the shortest pitch length P7. If α is made small, changes in the level of vibrations emitted from each pitch will be relatively small, and pulsation will be improved.

However, if α of P, , P, , is too small, the maximum/minimum pitch ratio becomes substantially small, and the pinch noise becomes worse. For this purpose, Ill' is made smaller than LL' by 4 to 30% for P and SP□. In addition, for pitches other than P3 and P1111, PIS
On the contrary, it is increased by 4 to 30% by the amount that pH 11 is reduced.

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

■ First, as with the conventional pitch design method, the maximum pitch length/
The minimum pitch length ratio β and the total pitch number N are determined.

To improve tire noise, the larger Niβ is, the better; however, considering other characteristics of noise, β = 1.3 to 1.8, N = 40.
It is desirable that the number is selected within the range of 90 to 90. If N=5
7. Choose β=1.54.

■ Next, determine the length of each pitch from the tire outer diameter and N1β. Here, when calculating for a tire with an outer diameter of 6001, this is converted into an integer from D×π10N=33.07, and the length of the intermediate pitch is set to 33 mm.

■ Next, decide on the number of pitch types. The number of types is 3 to 8 as described above.

Here, there are five types.

■ When designing 5 types of pitch lengths with β = 1.54 and intermediate pitch length = 33 mm, the maximum to intermediate and intermediate to
Letting k be the difference in the shortest pitch, (33+ k)/(33-
k) = β = 1° Get = 7 from 54, maximum 40,
Get the shortest score of 26. For the remaining three types, I filled in the gaps appropriately and ended up with 40.36.33.29.26 m.
Select a pitch length of m.

■ As a standard for pinch distribution, the distribution ratio α5 for each pitch is firstly calculated based on the fact that there are five types of pitches.
(115)=0.2 determines the standard distribution, that is, the MM' line on which each pinch should be equally distributed as shown in FIG.

■ Next, as shown in Figure 7, the intersection C1 between the midpoint between the longest pitch length and the shortest pitch length and the MM' line, and A1
Alternatively, an LL' line is determined based on El and the short pitch increases the distribution. Point A1 has the shortest pitch length of 26 mm
, which is 13.5% higher than the equal distribution α=0.2 and given by α−0,227. When determining the LL' line when the longest pitch length is 40 mm, it is on the vertical line of the longest pitch length of 40 mm, is 12.5% lower than equal distribution α = 0.2, and is given by α = 0.175. It is obtained by connecting the 81 points given by C1 to the C1 point.

■ In this way, the LL' line is determined by increasing or decreasing α at the shortest or longest pitch by 0% to 80% compared to equal distribution, but if the slope is downward to the left (decreasing at the shortest pitch, decreasing at the longest pitch) (increased), the influence of longer pitches is too great, and a large peak occurs on the low frequency side of the pitch frequency. On the other hand, if the slope is more than 80%, the influence of shorter pitches will be too strong and a large peak will occur on the high frequency side of the pitch frequency.

(2) Once the LL' line is determined in this way, a second reference distribution is obtained from the intersection of each pitch length and the LL' line. Fifth
As shown in the figure, A, B,
If C, D, E, Al, B1. Assuming C1, DI, and 81 points, the value of α is determined as follows (α5 is the second standard distribution). If there is a deviation of more than 10% from the second standard distribution, there will be no noise reduction effect.

! L A 1 0.227 81 0.218 C10,200 D 1 0.190 E 1 0.175 ■Next, paying attention to low frequencies, reduce the ratio of the longest and shortest pinches and increase the ratio of intermediate pitches. E 1 = 0.175 at the longest pitch, reduced by 14.3% to E 2
=0.15, A 1 =0.22 at the shortest pitch
A 2 = O by subtracting 9.7% from 7.

205, and the intermediate pitch is C1=0.200 to 12
．． It was increased by 5% to make C2=0.225.

[Phase] In this way, the shortest and longest pitches are 4% to 30%
Reduced from the second standard distribution, 4% to 30 at intermediate pitches
%, the pulsatility of low frequencies can be improved.

If it is less than 4%, the effect of improving pulsatility cannot be obtained substantially;
If it exceeds 0%, the dispersion at the pitch frequency will be insufficient.

- The remaining two types of pitches are designed to take the middle value between the increase and decrease values on both sides of each pitch. That is, at pitch B, pitch A is reduced by 9.7%, and pitch C is reduced by 12.5%.
Since it is an increase, there is no increase or decrease.Also, in pitch D, pitch C increases by 12.5% and pitch E decreases by 14.3%, so 5.
Assuming a 3% increase, each pitch distribution α positive was determined as follows (α 0° is the adjustment value of α direct). In addition, the total sum of α5 is 1
．． If it does not become 0, each αi is adjusted proportionally.

(Left space below the wooden page)! L-C A 2 0.205 0.205482 0
．． 218 0.2184C20,2250,22
55 D 2 0.200 0.2004 [Phase] The number of each pinch can be determined as follows using α8' determined in (2) above.

Ni=perimeter×αi/pitch length P1 Therefore, pitch length, αi, N4, Nu'(N
(conversion of i into an integer) is as follows. As a result, the number distribution of each pinch is determined to be a total number of pinches that is slightly larger than the total number of pitches, 57, which was initially tentatively determined.

(Left space on this page)
26 0.2054 14.9
15B 29 0.21B4 14
．． 2 14C330,225512,913 D 36 0.2004 10.5
10E 40 0.1503
7.1 70 Here, each pitch is adjusted. In other words, in the distribution of the number of pitches determined by 0 above, Σ(
P, XNi )/π=593.6, which does not match the tire circumference (600ms), so
<600), adjust the pitch length proportionally. 600
Since ÷593.6 = 1.0108, the final pitch length is obtained by multiplying each pitch length tentatively determined at the beginning. The values are shown below.

Pio is the adjusted pitch length P.

(Left space below this page) Directly under the control of Pitch-ku1j'I ヱL' Engineering LA
26 26.30.2092B 29
29.30.2175C3333,40,2303 D 36 36.40.1930E
40 40.40.1500 Examples are shown below.

A steel radial tire (inventive tire, comparison tire) with a diameter of 600 mm and a tire size of 165SR13 was evaluated for noise pulsation width (dB) and noise feeling. The results are shown in Table 2.

Tire noise test method: A method based on JASOC606-73 tire noise test method, in which the tire was transferred at 50 km/h on a steel drum with a diameter of 3000 mm (air pressure, rim size, and load were JATMA standard conditions), and pulsation was measured. was evaluated based on the variation range of the OA value (100 to 2000) (overall value of noise passing through a 1z band-pass filter) within one rotation of the tire.

(Margins below this page) As can be seen from Table 2, Comparative Tire 1 has a large distribution of shortest and longest pitches, so pinch noise dispersion and low-order pulsation are strong, making it unsuitable for practical use. Comparative tire 2 has a large pitch and a large number of grooves, so it is similarly unsuitable for practical use. In Comparative Tire 3, the distribution of each pitch is approximately equal and within the range of α-0.2 ± 10%, so the pinch noise is relatively well dispersed and low-order pulsation is also improved.
Durable in practical use.

The tire 1 of the present invention has a large distribution of short pitches, with A pitch being 25% more than equal distribution, E pitch being 25% less than equal distribution, and gradually decreasing from A to E pitch. Therefore, both pitch noise dispersion and pulsation properties are further improved compared to Comparative Tire 3.

The tire 2 of the present invention has a distribution that is 13% more than the equal distribution on the A pitch and 13% less than the equal distribution on the E pitch,
Furthermore, the proportion of C pitch is increased by 13%, and the proportion of A and E pitches is decreased by 10 to 14%. Therefore, pitch noise is kept relatively good, and pulsation is improved most significantly.

〔Effect of the invention〕

As explained above, in tire noise where the rigidity of the pitch increases with the length of the pitch and the pitch vibration generated from each pitch changes with the size of the pitch, the method of arranging the pitches is based on the distribution ratio of each pitch. is an important problem, and in the present invention, it is possible to improve pitch noise dispersion and pulsation by dividing each pitch into equal parts, by determining how many short pitches are distributed, or by reducing the distribution of the longest and shortest pitches. It becomes possible to measure.

[Brief explanation of the drawing]

Figure 1 (a), (b), Figure 2 (a), (b), Figure 3 (a), (b), and Figure 4 (a), (b)
are explanatory diagrams each showing the relationship between the pitch array, the order when Fourier analysis is performed, and the amplitude corresponding to the order. FIG. 5, FIG. 6, and FIG. 7 are explanatory diagrams showing the relationship between pitch length and pitch composition ratio αi, respectively. Figures 8(a) and 9(a) are explanatory diagrams showing the pitch arrangement, respectively, and Figures 8(b) and 9(b) respectively correspond to the order and its order when performing Fourier analysis. FIG. 1...Shaded area, 2...Vibration waveform. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] Three to eight types of pitches with different lengths constitute one circumference of the tread surface, and among these pitch types, the length of the i-th type of pitch is P_i, and this pitch appears in one circumference of the tire. When the total number is N_i, the composition ratio α_i of each pitch type is α_i = (P_i × N_i) / total tire circumference, and NP is the number of pitch length types, (1) the horizontal axis is the pitch length and The vertical axis is α_i, and the longest pitch length α is (1/NP) x 0.2 to (1
/NP) and set the shortest pitch length α to (
1/NP) to (1/NP) x 1.8, connect these α's to form the LL' line, and increase or decrease α by ±10% with respect to this LL' line. (2) If the horizontal axis is the pitch length and the vertical axis is α_i, the longest pitch and the shortest pitch α are LL' with respect to the LL' line defined in (1) above. 4 to 30% smaller than that determined by the line, and α of the next shortest pitch after the longest pitch and the next longest pitch after the shortest pitch is LL'
A polygonal line 11' is formed by connecting α determined by 4 to 30% larger than that determined by the line, and this polygonal line l
α within the range obtained by increasing or decreasing α by ±10% with respect to l'
A pneumatic tire characterized by the presence of __i.