JPH075002B2 - Pneumatic tire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic tire, and more specifically, to noise (pattern noise) generated by a tread design due to rolling of a tire, abnormal tire wear and abnormality. The present invention relates to a pneumatic tire capable of reducing noise without causing vibration.

[Conventional technology]

Conventionally, the pattern noise is distributed by using the variable pitch array method in which the design elements of the tread design are made into several different repeating (pitch) units and arranged in an appropriately randomized order in the circumferential direction. It was

This is based on the frequency modulation theory used in radio engineering, etc., and is a method that changes the time interval of pulsed vibration generated by each design element so that noise does not concentrate at a specific frequency. .

Further, in this method, it is said that the larger the ratio α of the longest to the shortest of the repeating pitch, the higher the effect of noise dispersion.

However, in the conventional valuable pitch array method, as shown in a typical example in FIG. 4, when the pitch is changed, the design element of the pitch is changed in a similar manner. If α is large,
The shortest repeating unit becomes too small, that is, the smallest design element becomes too small, causing abnormal wear and vibration, and the noise dispersion effect is also limited (α = 1.5 is practical. limit).

However, the market demand for noise improvement has been increasing more and more in recent years, and it is the actual situation that the above-mentioned conventional valuable pitch array method cannot sufficiently deal with the situation.

[Object of the Invention]

The object of the present invention is not only to arrange the tread design simply by the valuable pitch arrangement method, but also to pay attention to the specific rigidity of the pitch, so that noise can be generated without causing abnormal wear or vibration compared to conventional tires. An object of the present invention is to provide a pneumatic tire capable of enhancing the energy dispersion effect to reduce noise, improving the habitability of an automobile, and suppressing noise pollution.

[Structure of Invention]

That is, the present invention provides a tire circumferential direction repeating unit in the tire ground contact width of a tread design component composed of a main groove, an auxiliary groove, and a sipe on the tread surface, and a plurality of types of pitches having different pitch lengths are set in the tire circumferential direction. Is a pneumatic tire arranged in a valuable manner, the ratio β to the smallest design index Zpmin of the largest design index Zpmax of the design index Zp defined by the following formula, which is an index of the specific rigidity of each of these pitches.
= Zpmax / Zpmin is set to a value of 1.10 to 1.30, and the arrangement of the specific rigidity of the pitch in the tire circumferential direction is made variable independently of the pitch length.

Wp: Tire ground contact width under JIS standard conditions Pp: Tire circumferential length of each pitch Gmax: Maximum depth of main groove G _W : Groove width of main groove and auxiliary groove existing at each pitch G _D : At each pitch groove depth of the existing main groove and the auxiliary groove G _L: depth of sipes existing in each pitch: each present in the pitch main groove and the groove of the auxiliary groove length S _W: width S _D of the sipe existing in each pitch S _L : Length of sipes existing in each pitch i: Number of main grooves and auxiliary grooves included in each pitch j: Number of sipes included in each pitch That is, in the above formula, (Wp × Pp x Gma
x) represents the tread volume (volume including groove space) above the main groove bottom for each pitch p, while Σ (G _W × G _D × G _L ) and Σ (S The sum of ( _W × S _D × S _L ) represents the size of the space volume occupied by the main groove, the auxiliary groove, and the sipes existing in each pitch p. Therefore, it means that the specific rigidity per pitch decreases as the size of the space volume on the denominator side increases.
That is, the smaller the design index Zp, the smaller the specific rigidity per pitch.

However, as described above, the design of each pitch design element in the conventional valuable pitch array method is
As shown in the figure, main grooves, auxiliary grooves, sipes (thin cut grooves), etc. are designed so as to have a substantially similar shape from a long pitch to a short pitch. That is, in the short pitch compared to the long pitch, the groove width is relatively narrowed or the length of the sipe is shortened, so that the design index Zp of each pitch is a value that is approximately approximate to any pitch. , The ratio β of the largest design index Zpmax to the smallest design index Zpmin is in the range of 1.0 to 1.05. Therefore, the design specific rigidity in the tire circumferential direction does not change, and therefore stress concentrates on the minimum pitch, resulting in abnormal wear and vibration.

[Background of the invention]

In the conventional variable pitch array method, the design elements for each pitch are designed by designing the main groove, auxiliary groove, sipe (thin cut groove), etc. so that they have a similar shape from a long repetition pitch to a short repetition pitch. That is,
At a short pitch compared to a long pitch, the groove width is relatively narrowed and the length of the sipe is relatively shortened, and eventually the design index of each pitch, which will be described later, is a value that is close to any pitch and is the highest. A pitch with a design index,
The pitch ratio β having the lowest design index is 1.0 to
It is in the range of 1.05.

Here, the design index Zp of each pitch is defined as follows.

However, suffix p: each pitch.

i: each groove element included in the pitch p.

j: Each sipe element included in the pitch p.

W: Tire ground contact width under JIS standard conditions P: Pitch circumferential length suffix W: Width, D: Depth, L: Length G: Groove element S: Sipe element Gmax: Maximum main groove depth In the invention, the above-mentioned formula is of course the case where the center area of the tire ground contact width and the entire width of the shoulder area have the same pitch arrangement, but for example, when there are different pitch arrangements in the center area and the shoulder area. However, if the pitch arrangement in which a plurality of types of repeating units are arranged with the tire ground contact width as a unit can be grasped, the same effect can be obtained based on the calculation of the above formula.

The inventor of the present invention, in addition to the valuable pitch arrangement method, determines the design element of each pitch so as not to be proportional to the length of the pitch, and strengthens the nonuniformity of the specific rigidity of each pitch, which is effective for noise dispersion. Focusing on what is likely,
An experiment was conducted with the parameter β being the ratio of the maximum design index to the minimum design index of each pitch.

In the experiment, the maximum / shortest pitch ratio α was fixed at 1.3 on steel radial tires of 165 SR13 size, the depth, length and width of sipes were changed at various pitches, and the maximum design index Zp of each pitch was obtained. / Minimum ratio β from 1.0 to 1.4
I changed it to.

The noise was measured according to JASOC 606-73 "Tire noise test method".

As a result, as shown in FIG. 2, it was found that making the design index of each pitch nonuniform rather than uniform is advantageous for the low noise range.

That is, in the present invention, the design components of each pitch are not changed in a similar manner with a change in pitch, and the design shown in FIG. 2 is adopted. In the design shown in Fig. 2, the sipes provided at the maximum pitch P _A are
By not setting P _C , the design index Zp
In this case, Zp of the minimum pitch P _C is maximum and Zp of the maximum pitch P _A is minimum.

Further, as the value of β, 1.10 shows a clear effect, and the larger the value of β, the better.

However, if β is too large, that is, the difference between the pitch having the maximum specific rigidity and the pitch having the minimum specific rigidity is large, the tire wear form becomes abnormal, or the noise at the time of wear deteriorates. Inconvenience such as occurs, at most β =
The limit is 1.30. Therefore, it was found that β is good between 1.10 and 1.30, and preferably between 1.10 and 1.20.

Furthermore, when making a difference in the design index between pitches, a method of setting the design index in proportion to the size of the pitch length, a method of randomly changing the design index regardless of the pitch length, It was found to be effective in any case such as the method of changing the design index only to a specific pitch.

Next, the present inventor considers that if the design element with the shortest pitch becomes too small, problems of abnormal wear mode and deterioration of noise during wear occur, so that the design index of the minimum pitch is kept high and the specific rigidity of the design is kept high. We proceeded with a study on how to increase

That is, the pitch having the smallest design index was set as a pitch having no shortest pitch length, and rather, an experiment was conducted to give the highest design index in the shortest pitch.

The maximum / minimum ratio of the design index was fixed at β = 1.15, and the maximum / minimum ratio of the design index at the pitches other than the shortest pitch and the ratio βmin of the design index at the shortest pitch were changed together with the maximum / minimum ratio of the pitch length α. Was done.

As a result, as shown in FIG. 3, the ratio βmin is 1.15.
When the minimum value of the design index is given to the shortest pitch (circle in the figure), the noise is reduced according to the frequency modulation theory as α is increased. However, in this case, if α is increased, the element length of the shortest pitch becomes shorter, and the design index Zp becomes smaller, so the design specific rigidity becomes too low and abnormal wear and deterioration of noise due to wear become remarkable. , Can not be put to practical use. Therefore, the value of α could not be set to 1.3 or more.

On the other hand, when the ratio βmin is set to 0.90, the minimum value of the design index is given to pitches other than the shortest pitch, and the maximum value of the design index is given to the shortest pitch (marked with ● in the figure), the βmin is set to 1.15. Although the height of the curve is higher than that of the curve indicated by the circle, the practical value of α can be increased to 1.3.

Therefore, at βmin = 1.15 (circle) in FIG. 3, α−
Comparing the case of 1.4 and the case of α = 1.8 in βmin = 0.90 (mark ●), it can be seen that the noise reduction effect is greater in the case of βmin = 0.90.

By maximizing the design index of the shortest pitch in this way, the maximum / minimum ratio α of the pitch length is larger than the range that could not be put to practical use in the past (β = 1.0 and α = 1.5 is the limit). However, it becomes possible to further reduce noise. That is, in the present invention, βmin is 0.95
Below, it is desirable to set α to 1.3-
It can be increased to 1.8, preferably 1.5 to 165.

That is, it was found that when the specific rigidity at the shortest pitch is lower than the conventional value, the upper limit of α becomes lower than that of the conventional value.

[Explanation of Examples]

Hereinafter, the present invention will be specifically described by way of examples with reference to the drawings.

FIG. 1 is an explanatory plan view showing a main part of a pneumatic tire according to an embodiment of the present invention.

In the figure, E is a pneumatic tire according to an embodiment of the present invention. By arranging a tread design component Ea including a main groove 10, an auxiliary groove 20 and a sipe 30 on a tread surface T of the tire based on a valuable pitch arrangement method. It is configured.

And in the present invention, in particular, the design having the largest design index Zpmax among the design indices Zp represented by the equation (1) of the tread design component within each pitch P _A , P _B , P _C is the smallest design. Ratio β to the index Zpmin =
The value of Zpmax / Zpmax is set in the range of 1.10 to 1.30.

More specifically, FIG. 1 and the following Table 1 (a), 1st
It is as shown in Table (b).

In Table 1 (a) and Table 2 _{(a), G 1, G} 2, G 3, G 4, G 5, G 6: pitch P _A of FIG. 2 and FIG. 4, P _B, P _C
Auxiliary grooves respectively the main groove provided on the _{S 1, S 2, S 3} , S 4, S 5: the pitch P _A of FIG. 2 and FIG. 4, P _B, respectively provided in the P _C sipe (however, the pitch Sipe on P _C
S _2, S _3, S ₄ is not provided) W: groove width, D: depth, L: shows a groove length.

In Table 1 (b) and Table 2 (b), Indicates.

As described above, in the present embodiment, when the tire tread design is formed based on the valuable pitch arrangement method, the design index Zp of each pitch P _A , P _B , P _C is changed, and the design of the shortest pitch is given. By making the index higher than other pitches, the maximum / minimum ratio α of the pitch length can be increased, and the noise can be significantly reduced.

(Experimental Example) In this experimental example, conventional tires shown in Fig. 4, Table 2 (a), Table 2 (b), and Table 3, and Fig. 1, Table 1 (a), and Table 1 were used. (B), inventive tire (1) shown in Table 3, inventive tire (2) shown in Table 3, comparative example tire (1) shown in Table 3, comparative tire (2) shown in Table 3 ) Was used to examine the noise of a new tire, the noise of a tire after traveling 1000 km, and abnormal wear.

The conventional tires are specifically as shown in FIG. 4 and Tables 2 (a) and 2 (b) below.

As a result of the experiment, the experimental results shown in Table 3 were obtained.

From the experimental results shown on the right side of Table 3, (a) the tire (1) of the present invention has improved noise resistance because β = 1.27 and βmin is 0.87 even if α is as large as 1.63. There is no problem.

(B) Since the tire (2) of the present invention has β larger than that of the conventional tire to be 1.19, the noise resistance is improved.

(C) Since the comparative tire (1) has β as large as 1.39, it has problems in noise during wear and wear mode.

(D) In the comparative tire (2), when β = 1.0 (conventional), α was set to a large value of 1.55, so there was no improvement effect on noise during wear, and there was a problem in the form of wear.

If α exceeds 1.8, abnormal wear may occur, which is not preferable.

After all, it was found that by increasing α with a limit of 1.8, βmin smaller than 0.95, and increasing β with a limit of 1.3, the best noise performance and no other problems can be obtained. It was

〔The invention's effect〕

According to the present invention, the tread design (pattern) in the tire ground contact area is formed by arranging a plurality of types of pitches, which are the tread design elements, based on the variable pitch arranging method. The pitch design index is displayed as a specific formula, and its maximum design index Zmax and minimum design index Zpmi
The value of the ratio β (= Zpmax / Zpmin) with n is set in the range of 1.10 to 1.30 so that the design specific rigidity of each pitch can be varied, and the noise reduction effect can be achieved only by the above valuable pitch array method. It is possible to further improve the noise reduction effect without causing abnormal wear or vibration when the size is increased. Furthermore, the design index of the shortest pitch is maximized, and the ratio βmin to the maximum design index of pitches other than the shortest pitch of this design index is 0.95.
The maximum / minimum pitch ratio α is 1.3 / 1.
It is possible to increase the range up to 8 and further improve the noise reduction effect.

[Brief description of drawings]

FIG. 1 is an explanatory plan view showing a main part of a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is Zpmas / Zpmin, that is β
And FIG. 3 is a diagram showing the relationship between Pmax / Pmin, that is, α and the sound pressure level, and FIG. 4 is an explanatory plan view showing a main part of a conventional tire. is there. 10 …… Main groove, 20 …… Auxiliary groove, 30 …… Sipe.

Claims (1)

[Claims] 1. A tire circumferential direction includes a plurality of types of pitches, each of which has a pitch in a tire circumferential direction repeating unit in a tire ground contact width of a tread design component composed of a main groove, an auxiliary groove, and a sipe on a tread surface. Is a pneumatic tire arranged in a valuable manner, and is the largest design index of the design index Zp defined by the following formula, which is an index of the specific rigidity of each of these pitches.
The ratio of Zpamx to the smallest design index Zpmin β = Zp
A pneumatic tire in which max / Zpmin is set to a value of 1.10 to 1.30, and the arrangement of the specific rigidity of the pitch in the tire circumferential direction is made variable independently of the pitch length. Wp: Tire ground contact width under JIS standard conditions Pp: Tire circumferential length of each pitch Gmax: Maximum depth of main groove G _W : Groove width of main groove and auxiliary groove existing at each pitch G _D : At each pitch groove depth of the existing main groove and the auxiliary groove G _L: depth of sipes existing in each pitch: each present in the pitch main groove and the groove of the auxiliary groove length S _W: width S _D of the sipe existing in each pitch Length S _L : Length of sipes existing in each pitch i: Number of main grooves and auxiliary grooves included in each pitch j: Number of sipes included in each pitch