JPS5822364B2 - pneumatic tires - Google Patents

Description

[Detailed Description of the Invention] Tire pattern noise is caused by the air contained in the pattern within the tire tread being compressed when the tire makes contact with the ground and expanded when the tire recovers from the ground. It is a sound that comes as waves.

Generally, two methods can be considered for reducing pattern noise.

One method is to reduce the sensory noise experienced by humans by frequency modulation, and the other method is to reduce the energy source of pattern noise itself.

As a result of theoretical analysis and repeated experiments of these methods, the present invention has found that by suitably combining these methods, it is possible to provide a pneumatic tire with extremely low pattern noise. The feature is that the plurality of pitch elements arranged on at least one rib of the tread pattern are arranged in a sine or random arrangement, and the ratio of the maximum pitch element length to the minimum pitch element length is 1. .20≦h≦
1.60, and the number of modes M is 2≦M≦12
, the angle θ of at least one groove with the tire circumferential direction is 20°≦θ≦90°, and the tire pattern has a shape in which the number of different pitch elements is 3 or more. It is in.

The present invention will be explained below first from the aspect of reducing pattern noise by frequency modulation.

Tire tread patterns are usually designed using a method called pitch variation, as shown in FIG. 1, in which the pitch element length Li is varied in two to three or more types.

Note that ■ in the same figure shows a rib type, ■ in the same figure shows a block type, Ll, L2, and L3 show pitch element lengths L1NL2NL3, and 1 shows a groove (group).

However, in the past, the methods of changing the pitch element length L and allocating it were designed based on trial and error, intuition, and economical compromises, so tire designers were unable to change the pitch element length using simulators or test patterns. We have been researching this using hand-carved tires, etc., but in reality, it is difficult to obtain the optimal pinch element length change and its allocation method, and the best results cannot be guaranteed.

Also, Japanese Patent Application Laid-Open No. 1983-204 filed before the filing date of the present invention
The invention of No. 02 uses two types of pattern components (pitch), and the pitch arrangement method is performed according to the rules of a series of pseudo-random binary signals, and modulates the frequency (pitch) to reduce noise. However, even with this method, the noise reduction cannot be said to be sufficient.

Based on this technical background, the present inventor focused on the already known frequency modulation theory (FM theory) described below in designing a tire tread pattern, analyzed this theory, and conducted experiments. As a result, the present invention has been completed.

Amplitude I.

, angular frequency ω. If the carrier wave of
) dt ) or V(t) = Ioexp(j (ωot +K foS
(t) dt )) Here, the signal wave S (t) has a period of 2π/p and a phase θn1 amplitude In as 5(t)=ΣI n cos (upt+θn)n=1
If it happens, then V[)=Ioexp['(j ((7).

t +f6”InXIKIn cos(npt+θn)
)dt)), 1 =■oeXpCj(ωot+Σβn sin (npt
n=1 +θn))] = I□e J(')o 1e jΣβn sin (
npt+θn)n=i Here, β−Δω/n psΔω=KIn is a constant determined by the system, and Δω and In are the frequency shift and modulation index for each component of the modulated wave, respectively.

Therefore, V(t) = I(,e JωOtπΣ Jr(In)e
j (rnptn = 1 r = -■ -1-ron) . . . ■ Here, Jr (In) is a Be5sel function.

In the tire-related industry, the above theory is used only when n = 1, that is, when a single sine wave is input, and this is explained in the magazine "Expressways and “Automobile” in 1970, /166 “
This is also disclosed in literature such as Research on Tire Noise 29, but these do not mention anything about the handling of higher-order components of n.

In other words, the frequency modulation generates a sound (pure tone) with a single frequency when the pitch element lengths are equal,
By varying the length of the element, the sound produced is dispersed into a number of frequencies of lower levels.

If part or most of the sound generated is mixed with the surrounding sounds, or if the sound is difficult to hear due to the characteristics of human hearing, reduce the noise intuitively. .

Generally, a tire tread pattern is formed on the tread surface during vulcanization by a tread pattern carved into a metal mold called a mold.

At this time, when manufacturing the mold, it is difficult to change the length of all the pitch elements over the entire circumference of the mold, and the pitch elements must be combined in a certain regularity (this is called a mode).

The mode described later in the present invention refers to the tire (or mold)
The entire circumference is considered to be one period, and the period has a length obtained by dividing this period by a natural number.

From the above, in order to modulate the frequency according to the present invention, it is necessary to divide the entire circumference of the tire (mold) pattern into several modes in addition to changing the pitch element length, and to allocate within the modes. Since the experiment will be conducted after including the following, the experimental results and their discussion are presented below.

<A> The maximum and minimum pitch element lengths were determined by comparing the two, and the results of an experiment are shown in Figure 2.

In the figure, the vertical axis shows the sound pressure level, the horizontal axis shows the frequency, and the parameter is the maximum/minimum pitch element ratio.

Naturally, h=1.0 indicates equality.

Dispersion of the fundamental frequency clearly occurs as h increases.

In SAE paper 690520, this ratio is 1.
It is stated that there is no frequency dispersion effect unless it is 5 or more, but as is clear from the figure, in this experiment h = 1.2
However, it was confirmed that it was sufficiently effective.

<Explanation> Figure 3 shows the results of experiments conducted by changing the number of turns within the entire circumference of the tire (mold), that is, the number of modes M.

In the figure, the vertical axis represents the sound pressure level, and the horizontal axis represents the frequency.

In this experiment, the maximum/minimum pitch element ratio h=1.50
In this case, the number of modes M was varied from 3 to 12, and as is clear from the figure, it was confirmed that the sound pressure level becomes flat as the number of modes decreases.

The arrangement of pitch elements in each mode used in this experiment is a relatively simple sine wave arrangement as shown in Figure 4A, but the pitch elements themselves within that mode can be freely replaced as shown in Figure 4B. Even if it is, it will just be a collection of sine waves whose period is that mode (F□urie
r series expansion).

Fourier here. The idea of Fourier transform regarding series expansion is that ``any periodic function can be expressed as a sum of trigonometric functions2'' (see Figure 20).
As explained for the r series.

Note that in FIGS. 4A and 4B, the vertical axis represents the pitch element length, and the horizontal axis represents the circumference.

<C> Figure 5 a1b, c shows the phase of the high frequency component in the mode, that is, 1
The phase of the next high frequency and the second high frequency is 0°, 90°”180°
This is a shifted waveform, with the vertical axis representing the pitch element length and the horizontal axis representing the circumference.

The measurement results are shown in FIG. 6, in which the vertical axis represents the sound pressure level and the horizontal axis represents the frequency.

This figure shows that a change in phase results in a shift in the frequency of the response sound pressure level! It turns out that it appears.

From the above, a collection of modes around the entire circumference of the tire (mold) is inevitable, as shown in Figure 7.
S・・・・・・・・・'5 Cn or a collection of modes including the condition C1=Cj for at least two hJs (Cn: pitch in the n-th mode) (how elements are allocated).

As a document that adds theoretical consideration to pitch variations to tire pattern design, the above-mentioned SAE pap
er 690520, but when considering the actual tire pattern mold processing method, it is meaningless unless the idea of the mode described above, which is the present invention, is introduced.

However, the gist of the present invention is completely different from that of the above-mentioned document.

Next, the present invention will be explained from the aspect of reducing pattern noise J noise due to energy reduction.

Prior to this explanation, we tested the 700-134PR tires using a chassis dynamometer under JIS conditions (D4202).
Noise measurements were carried out in accordance with 319).

This tire is hand carved with a pitch height of A1 and a groove width of B.

Table 1 below shows groove depth C as three factors and each level 4.3.3.
The experimental plan was set up as follows.

The results of this experimental design are shown in Table 2 below.

The same table shows the contribution rate for each factor, and P-1 (fundamental frequency level) in the same table is the frequency obtained by multiplying the total number of pitch elements around the tire by the number of tire rotations, and the bandwidth is 6 times that frequency. Refers to the sound pressure level within %.

Further, in the same table, A indicates the pitch height, B indicates the groove width, and C indicates the groove depth, as shown in the grooves of the tread pattern in FIG. 8.

From this table, it can be seen that the pitch height A makes the largest contribution to both the noise magnitude dB(A) and P-1 (fundamental frequency level), followed by the groove depth C.

In addition, at the same time as this experimental plan, we used a statistical method generally known as multivariate analysis to calculate the multiple regression equation (tire rotation speed 8 Hz) as an equation in dB (obtained for the case of A input P-1). Ta.

YdB(A)-67, 37-1-1, 22A+o, o4
cv'? - σ - 0,03A"・・・・・・・・・■ CiR However, 2N CiR; Tire circumference (mold) N; Total number of pitches The concept of total number of pitches is at least one tire as shown in Figure 9. In the groove, the minimum repeating pattern component (pitch) that is substantially expanded or contracted in the circumferential direction is counted as one pitch.

1 in FIG. 9 indicates the block type, 1 indicates the groove, and 2 indicates the size or small groove.

As is clear from the contribution rate of the coating 2, the pitch height factor dominates other factors as a tire (mold) design factor.

In other words, tire pattern noise depends only on pitch height.

Therefore, by using formula (■), when suppressing tire noise below a certain level, if a (= C1R/2N) and C (groove depth) are determined by the design conditions (size, type, etc.), the pitch height A is inevitably determined.

In other words, the present invention utilizes this experimental formula (■) to evaluate tire characteristics other than noise (drivability, stability, wear, wet skid,
It has become possible to keep the noise level of various tires below the automobile noise regulation value while fully satisfying the traction force, etc.).

As shown in FIG. 10, the equation (2) increases with the pitch height. In other words, the noise increases as the tire approaches a tire with a lug pattern or a single tire pattern.

Therefore, it is clear that the pitch variation described above is particularly effective for lug-type patterns and block-type patterns.

Equation 0 is P-1 (fundamental frequency) as shown in FIG.

number level), that is, the noise of the pitch element itself.

When we partially differentiate Equation 0 with respect to A, we get that the slope of the noise level with respect to the pitch height is 2d.
B/! The former pitch variation is effective for K and below.

This A (pitch height) - 9m7IL is made dimensionless. Tanθ-K Tanθ=,,=o, 428 ,°, 23° in θ becomes.

However, θ is the angle formed with the tire circumferential direction (direction perpendicular to the meridian).

In order to confirm the effects in the above experiments and theory, 16
5 SR13 tie key 2 mouths 2 types (both types have circumference (C1R
) = 195 L2mm, total pitch -mN) -72
).

(a) Pitch variation Tire (invention) maximum/
Minimum pitch element ratio h=1.30 mode number
M=6 Pitch height A=5.0 Groove depth C=8.0 mtn Angle θ-20, 3° (B) Equal pitch Tire maximum/minimum pitch element ratio h=1.0 Pitch height A= 9.0 mm Groove depth C=8. Omvt Angle θ = 33.6° Figure 12 shows a comparison graph of the noise levels of (a) and (b) tires.
dB (A paper.

This agrees well with the result of Eq. Figure 13 is (a),
(b) Show a comparison graph of tire frequency analysis; (b)
Dispersion of the tire's fundamental frequency is clearly observed.

From the above experiments, it is necessary to take the following values for the ratio of maximum and minimum pitch element lengths h1 mode number M1 pitch height A (angle θ with the tire circumferential direction).

(1) The larger the ratio of the maximum and minimum pitch element lengths, the greater the effect of frequency dispersion due to pitch variations, but if abnormal tire wear etc. are taken into account, it should be 1.2<h<1.6. There is a need.

That is, when h(+, 2), the frequency dispersion effect is small, and h
This is because when it is >1.6, abnormal wear occurs.

In addition, unless there are three or more different pitch elements,
That is, in the case of two elements, the maximum and minimum pitch elements are adjacent to each other, so the movement of the minimum pitch increases and polygonal wear (a type of abnormal wear) occurs.

In comparison, if there are three or more different pitch numbers, the possibility that the maximum and minimum pitch elements will be adjacent to each other is reduced or can be eliminated.

(2) The smaller the mode number M is, the higher the flatness of the frequency dispersion is, but it is necessary to set it to 2≦M≦12 in consideration of the mold processing method.

That is, when M>12, the flatness of frequency dispersion disappears,
This is because mold processing becomes complicated when M<2.

(3) If the pitch height A is 9 mm or less, the absolute value of the fundamental frequency level will be low, so it is unnecessary to adopt pitch variation, and the effect of pitch variation can be expected by the partial differential coefficient shown by the empirical formula ■ is 2.0~1.5dB,
In other words, the effect of pitch variation is exhibited when the angle θ formed with the tire circumferential direction is 20 to 90 degrees.

Next, the tire according to the present invention and Japanese Patent Application Laid-Open No. 50-2040
The comparative test results of the tire according to the invention No. 2 will be explained.

The tire shown in FIG. 14 is a tire according to the present invention, which has four reeds, the number of different pitch elements is sinusoidal, the mode is 2, and the maximum/minimum pitch element ratio is 1.4.
5. The angle is 90° in the circumferential direction.

What is shown in FIG. 15 is a tire according to the invention of Japanese Patent Application Laid-Open No. 50-20402.

The tire size for both is 155SR13.

The test conditions and test results are as shown in Table 3 and Figures 16-18.

In the figures, I indicates the present invention, and ■ indicates the tire according to the invention of Japanese Patent Application Laid-Open No. 50-20402.

According to the above test results, the tire according to the present invention was
It can be clearly seen that the frequency modulation effect is greater than that of the tire according to the invention of No. 20402.

That is, although the minimum sound pressure level in the vicinity of the fundamental frequency does not change, the maximum sound pressure level is lower in the tire according to the present invention, and the fluctuation itself in the sound pressure level is small.

As described above, the present invention has a tire pattern shape in which a plurality of pitch elements are arranged according to a sine or a random arrangement thereof, and the number of different pitch elements is three or more, and the ratio of the maximum and minimum pitch element lengths, the mode By combining the five elements of number and pitch height, that is, the angle formed with the tire circumferential direction, tire pattern noise can be reduced by modulating the frequency (sound pitch) and reducing energy (sound intensity). This is a synergistically favorable effect, and unlike conventional tire tread pattern design, it is not a matter of trial and error or a compromise between intuition and economy. It is a pitch array arranged according to the rules of a series of pseudo-random binary signals such as the one shown in the figure, and noise is not reduced simply by modulating the frequency (pitch), but by theoretical analysis and experiment. Since this is done based on the results obtained, a very accurate pattern with low pattern noise can be obtained.

In addition, in the present invention, especially for molds where the entire circumference of the mold is divided into several parts, such as a so-called segment mold, by making one mold correspond to one division of the mold, mold processing, cost, common use, etc. can be further improved. The value increases.

[Brief explanation of the drawing]

Figure 1 ■ and ■ are pattern diagrams with pitch variations, Figure 2 is a graph of frequency analysis results when changing the ratio of maximum pitch element length/minimum pitch element length, and Figure 3 is the number of modes. Graph of frequency analysis results when changing M, Figure 4 A and B are tires (molds)
■The pitch element length allocation within the mode is shown in Figures 5a and 5b. C is a graph of the waveform in which the phase of the harmonic component in one mode of the tire (mold) is shifted by 0°, 90°, and 180°, and Fig. 6 is a graph showing the frequency analysis results for Fig. 5 1 b% C. , Figure 7 is a graph showing how to allocate tire (mold) modes, Figure 8 is an explanatory diagram showing tread pattern grooves (groups), Figure 9 ■ and ■ are 1
An explanatory diagram showing the concept of pitch, Figures 10 and 11 are graphs showing the noise level and fundamental frequency level with respect to pitch height A with groove depth C as a parameter.
Figures 2 and 13 are examples of the present invention and comparative example (7) 1.
A graph showing the noise level and frequency analysis results of 65SR13 tires, FIG. 14 is a pitch arrangement diagram of a tire according to the present invention, and FIG. 15 is a pitch arrangement diagram of a tire according to the invention of JP-A-50-20402. , Figure 16 shows the speed 50
Graphical diagram showing the frequency analysis results of the tire according to the present invention and the tire according to the invention of JP-A-50-20402 at k111/H (tire rotation speed 8 Hz), No. 17
The diagram shows: - Speed 100kIn/H (tire rotation speed 15.
Tire according to the present invention and Japanese Patent Application Laid-open No. 1973
= A graph showing the frequency analysis results of the tire according to the invention of No. 20402, Figures 18 and 19 are graphs showing the frequency analysis results of the tire according to the present invention and the patent application at a speed of 50 Ian/H and a speed of 100 Ian/H, respectively. FIG. 20 is a graph diagram showing the result of frequency analysis near the fundamental frequency with the tire according to the invention of No. 50-20402, and FIG. 20 is an explanatory diagram showing an example of a periodic function.

Claims (1)

[Claims] 1. The plurality of pitch elements arranged on at least one rib of the tread pattern are arranged according to a sine or a random arrangement thereof, and the ratio of the maximum pitch element length to the minimum pitch element length is 1.20≦
h≦1.60, and the number of modes M is 2≦M≦
12, the angle θ of at least one groove with the tire circumferential direction is 20°≦θ≦90°, and the number of different pitch elements is 3 or more. Features pneumatic tires.