JPH0429562B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a low-noise tire having a rib pattern including zigzag main grooves, in which tire noise can be reduced by selecting pitch elements of the zigzag main grooves. Tires with a rib pattern, which are mainly used as tires for trucks, buses, and light trucks that run on good roads, have excellent handling stability and high-speed durability. Unlike lug patterns designed primarily for use on paved roads, it is relatively advantageous in reducing noise caused by rolling. However, in recent years, regulations regarding automobile noise have become stricter, and it is desired to reduce tire noise as well as engine noise, intake and exhaust system noise, and cooling fan noise. Here, the noise caused by tires can be roughly classified according to its generation mechanism as follows. (1) Pattern noise This noise is caused by the pattern groove deforming when it comes into contact with the ground, and the air inside the groove being compressed and exhausted, causing the surrounding air to vibrate.The noise mainly has a frequency that matches the frequency of pattern pitches. A loud noise occurs. (2) Elastic vibration noise Due to road irregularities and tire non-uniformity (changes in tread rubber thickness and pattern), periodic impacts occur between the tire and the road surface when the tire rotates, causing the tread and case to vibrate. This causes compressional waves in the outside air and generates noise. (3) Sliding and squeaking noises Sliding noises caused by the movement of the tread within the tire's contact surface, as well as squeaks caused by partial slipping caused by deformation of the treads before and after contact with the ground. In general, tire noise is independent of the type of pattern, and the faster the vehicle speed, the higher the noise.
Most of the noise is caused by (1) and (2) above, and at normal operating speeds of 80 km/h or less,
It has been found that both contribute almost equally. Therefore, in reducing noise, even if only one of the causes (1) and (2) is eliminated, the noise prevention effect is not sufficient, and the important performance of the tire must be There is no point in causing inferior results in terms of high-speed stability, maneuverability, wear resistance, etc. Conventionally, the first method to suppress this type of noise is to disperse the frequency of the noise into a wide frequency band to make the noise less noticeable and to prevent the noise from increasing due to resonance with various parts of the vehicle. A well-known variable pitch method is an improved arrangement of pitch elements, which is the basis of the repeating tread design. This method involves arranging several types of pitch elements, usually three types, with different pitch lengths in appropriate combinations in the circumferential direction of the tire, and temporally suppressing the pattern noise or vibration that occurs while the tire is rolling. This is a method to prevent noise from concentrating on a certain frequency by changing the frequency, and is based on the so-called frequency modulation theory. The second method is to reduce the tread radius of curvature of the tread contact surface to reduce impact noise with the road surface, reduce elastic vibration noise, and reduce noise by making it easier to discharge air in the groove. This is a method such as letting All of the above noise reduction methods are recognized to be quite effective, but on the other hand, the first method, which is based on frequency modulation theory, uses pitch elements that have excellent noise dispersion. Even if an array can be assembled, for example, if the ratio of the length of the pitch element with the longest pitch to the length of the pitch element with the shortest pitch is large, the difference in pattern rigidity for each pitch element will become large. This is difficult to avoid, and not only does this adversely affect the vibration characteristics when the tire rolls, promoting elastic vibration noise, but the tread wear does not progress evenly, resulting in a tire with a very poor appearance due to wear, which significantly shortens the tire's lifespan. This may cause a decrease in the temperature. In addition, in the second method of reducing the tread radius of curvature, the ground contact pressure at the tread crown increases, causing premature wear of the crown, which significantly shortens the life of the tire. This results in a very uneconomical tire. Regarding the variable pitch method, for example, Japanese Patent Publication No. 51-41723 discloses that two sets of pitch elements each consisting of a plurality of components and having different average lengths are pitch arranged according to the rules of a pseudo-random binary signal. This disclosure discloses a pitch arrangement method for a tread pattern. In addition, Japanese Patent Publication No. 58-22364 regulates the length ratio of the maximum pitch element to the minimum pitch element arranged on one rib to be 1.20 to 1.60,
Moreover, it discloses a tire that includes three or more different numbers of pitch elements, and has a repeating mode number of 2 to 12 in which the pitch elements are combined with a certain regularity, and the former Japanese Patent Publication No. 51-41723. It is said to be superior in terms of noise reduction compared to other products. However, the above proposals all concern pitch elements in each groove, and are based on the premise that the same pitch element is provided in all of the plurality of main grooves. The present invention was completed as a result of various research into reducing noise in rib pattern tires with zigzag main grooves. The present invention was completed by discovering that the noise could be reduced by specifying the ratio of the noise. Therefore, an object of the present invention is to provide a low-noise tire that can effectively reduce pattern noise. The present invention provides a tire having a rib pattern in which a plurality of main grooves extending in the circumferential direction of the tire are provided on the tire tread surface, and the main grooves include at least two zigzag-shaped main grooves. Multiple types _{of doglegs} whose pitch lengths Si _, which are lengths of A first type of zigzag main groove Gy in which pitch elements that can be bent are arranged in a variable pitch, and a pitch length Tj larger than the maximum pitch length Sy of pitch elements in the first type of main groove Gy.
and the pitch lengths Tj are different from each other, and from the minimum length T ₁ to the maximum length Tz T ₁ <...Tj _-1 <Tj...<
There are two types of pitch elements: a second type of main groove Gz in which plural types of pitch elements are bent in a dogleg shape and the pitch length Tj is increased sequentially in relation to Tz, and the pitch length of each pitch element is The pitch ratio Si/Si _-1 = Pi, Tj/Tj _-1 = Qj are both 1.05 or more and 1.25 or less, and the minimum pitch length T ₁ of the main groove Gz and the maximum pitch length of the main groove Gy A low-noise tire in which the pitch ratio T ₁ /Sy=R of the pitch length Sy is smaller than 1.3, and the difference between the maximum value and the minimum value of the pitch ratios Pi, Qj, and R is 0.15 or less. be. In this way, in rib pattern tires,
It has two types of main grooves, and in these two types of zigzag main grooves, the pitch ratio of each pitch element is
By setting Pi and Qj within predetermined ranges, determining the range of the pitch element pitch length ratio R between the two types of main grooves, and setting the difference between the pitch ratios Pi, Qj, and R, the pitch length can be adjusted. In addition to increasing the white noise, it also reduces the difference in the longest and shortest pitch lengths between each groove, reduces the difference in pitch element rigidity, and equalizes the pattern rigidity. As a result, the vibration characteristics during tire rolling can be improved while maintaining the motion characteristics, and the noise characteristics as well as the elastic vibration sound can be made into a white nozzle. Furthermore, since the pattern rigidity can be made uniform, wear is made uniform and high-speed durability is maintained. An embodiment of the present invention will be described below based on the drawings. In Figs. 1 and 2, a low noise tire A of the present invention is shown.
The tread portion 1 has a rib pattern including two types of zigzag main grooves extending in the circumferential direction of the tread surface, and includes two types of zigzag first and second main grooves. A first main groove Gy and a second main groove Gz are arranged on both sides, and the two main grooves
Gy and Gz form zigzag grooves consisting of pitch elements that bend in multiple types of doglegs. In addition to the two main grooves Gy and Gz, there is also a straight main groove that extends in a straight line in the circumferential direction on the tire equator C.
Ga is attached to improve drainage performance. Further, the tread portion 1 forms a tire base together with the sidewall portion and the bead portion, and a casing 5 and a belt layer 6 are interposed in the tire base to increase its rigidity. In this embodiment, the first main groove Gy has a pitch length, which is the length in the tire circumferential direction, as shown in FIG.
Si consists of three types of pitch elements whose pitch lengths are different from each other and whose pitch lengths increase sequentially from the minimum length S ₁ to the maximum length S ₃ in the relationship S ₁ <S ₂ <S ₃ . Further, the second main groove Gz is formed by three types of pitch elements whose pitch lengths are different from each other, with the pitch length Tj increasing sequentially in the relationship of minimum length T ₁ < T ₂ < T ₃ . It is formed by Also, in the main grooves Gy and Gz, the pitch lengths S ₁ to _{S 3} ,
The pitch elements T ₁ to _{T 3} are arranged based on a so-called variable pitch, in which the order is scattered so that the arrangement is not constant. In the present invention, when the first main groove Gy is formed by y pitch elements and the other main groove Gz is formed by z pitch elements, in one main groove Gy,
The pitch length Si increases sequentially from the minimum length S ₁ to the maximum length Sy according to the relationship S ₁ < Si _-1 < Si...Sy. In the second main groove Gz, the pitch length Tj is
Pitch length of pitch element of first main groove Gy
The pitch length Tj is larger than Si, and the pitch length Tj is increased sequentially from the maximum length T ₁ to the maximum length Tz in the relationship of T ₁ <...Ti _-1 <Tj...Tz. In addition, the two main grooves Gy and Gz have pitch lengths Si and Tj of adjacent pitch elements having the pitch ratios Si/Si _-1 = Pj Tj/Ti _-1 = Qj both of 1.05 or more and 1.2. It is as follows. Further, between the first main groove Gy and the second main groove Gz, there is a pitch element with a minimum pitch length T ₁ of the main groove Gz and a pitch element with a maximum pitch length Sy of the main groove Gy. The ratio T ₁ /Sy=R is set to be smaller than 1.3. Note that it is larger than 1. Moreover, the difference between the maximum value and the minimum value among the pitch ratios Pi, Qj, and R is set to 0.15 or less. This reduces the difference in the longest and shortest pitch lengths, reduces the difference in rigidity of the pitch elements, equalizes pattern rigidity, improves vibration characteristics during tire rolling, and reduces elastic vibration noise and noise characteristics. It has been found that it can be turned into white noise. Furthermore, since the pattern rigidity can be made uniform, wear is made uniform, the appearance after wear is not impaired, and a decrease in tire life is suppressed. Furthermore, the pitch length changes between the two grooves, which increases the white noise of the noise, and the pitch ratio is different between each groove, and the pitch ratios Pi, Qj, and R are kept within a predetermined range. Therefore, differences in pattern rigidity between each groove are reduced, reducing noise without impairing tire characteristics. Note that the first main groove Gy and the second main groove Gz are similar to the third main groove Gy.
As shown in the figure, a plurality of strips may be provided on both sides of the tire equator. Note that pneumatic tires include all vehicle pneumatic tires having bias, radial, and semi-radial structures. In addition, the total number of pitch elements per revolution of the first main groove Gy and the second main groove Gz, that is, the number of pitches.
N ₁ and N ₂ exclude the range of |N ₁ /N ₂ −M|<0.05. Here, M is an arbitrary integer. For example, when N ₁ =MN ₂ , the M-order harmonics of N ₂ pitches match the first-order harmonics component of N ₁ pitches. For example, in Figure 5, N ₂ = 50 pitches and N ₁ = 60 pitches.
This shows the peak level of the first-order component of N 1 when changing it up to ~140. When _{N 1 =} 100 pitch, the second-order component of N ₂ and the first-order component of N ₁ overlap and reach a peak. This shows that there are places where the pitch noise becomes extremely high and the pitch noise becomes extremely bad, and it is necessary to exclude places where the pitch element arrangement meets the above conditions. This can also be determined from the following equation, which is a condition for synchronization by computer simulation. The formula is derived from a Fourier series that expresses a periodic function as a sum of trigonometric functions, and each pitch length is
It is expressed as a pulse train, and the synchronization conditions can be found by performing harmonics analysis using this equation. H _o = Co _N 〓 ^K=1 An E ⁱ 2nπ/lXk H _o = nth harmonics component Co: Normalization constant An: Pulse weighting constant l: Length of one circumference of the tire Xk: k-th pulse position N : Number of pulses n: Integer From the above equation, the noise becomes high when the harmonics first-order component (H ₁ ) has a pitch number of N, and when the harmonics second-order component (H ₂ ) has a pitch of 2N. Therefore, when applying to the above example, it is understood that it is better to exclude the range in which the ratio N ₁ /N ₂ of N ₁ and N ₂ is an integer n (=the above-mentioned M). Furthermore, by excluding the 0.05 range, synchronization can be reduced. Below, the results of noise measurements are shown in FIGS. 6 and 7 for Example A shown in FIG. 3 of the present invention, Example B shown in FIG. 2, and a comparative example based on the prior art shown in FIG. As shown in FIG. The main specifications of the tires used in this test are shown in Table 1.
The test conditions are as follows. As shown in Table 1, the comparative example product has pitch elements of three different pitch lengths, that is, four pitch elements of the same configuration consisting of pattern constituent units.
A book seed groove G... is provided in the tread portion. Tire size: 7.00-15 8PR, internal pressure: 3.25Kgf/cm ² or 2.40Kgf/cm ² , load: 530 f/tire, sound collection microphone directly beside the tire, 100cm apart from the center of the tire width, on the ground contact surface. The tire was installed at a height of 25 cm and measured while driving the tire by rotating a drum in an anechoic chamber (conforms to the tire noise test method specified in JASO C606). The product of the present invention exhibits excellent noise reduction effects. Furthermore, comparative tests were conducted on tire performance, such as wear resistance, handling stability, and high-speed durability. The test results are shown in Table 2. The values in the table are expressed as an index, with the comparative example product set as 100.
For any characteristic value, a larger value indicates better quality.

〔Effect of the invention〕

Thus, the present invention can effectively reduce tire noise without impairing tire performance.

【table】 [Brief explanation of drawings]

Fig. 1 is an axial cross-sectional view of a tire showing one embodiment of the present invention, Fig. 2 is a developed plan view showing an enlarged tread pattern of the tire, and Fig. 3 is an enlarged view of a tread pattern of another embodiment. FIG. 4 is a developed plan view showing the pattern of the comparative tire; FIG.
The figure is a graph showing the relationship between pitch number and noise level, Figures 6 and 7 are graphs showing the relationship between noise frequency and sound pressure level, and Figure 8 is a graph showing the relationship between speed and noise level. Gy...Main groove, Gz...Main groove, Si, Tj...Pitch length.

Claims (1)

[Scope of Claims] 1. A tire having a rib pattern in which a plurality of main grooves extending in the circumferential direction of the tire are provided on the tire tread surface, and the main grooves include at least two zigzag-shaped main grooves, wherein the main grooves are: The pitch length Si, which is the length in the circumferential direction, is different from each other, and from the minimum length S ₁ to the maximum length Sy, S ₁ <...Si _-1 <
A first type of zigzag main groove Gy in which plural types of pitch elements bent in a dogleg shape are arranged in a variable pitch, increasing the pitch length Si sequentially according to the relationship Si...<Sy; and the first type of main groove Gy. have a pitch length Tj larger than the maximum pitch length Sy of the pitch element in the groove Gy, and the pitch lengths Tj are different from each other;
From the minimum length T ₁ to the maximum length Tz T ₁ <...Tj _-1 <Tj
There are two types of pitch elements, each of which is bent in a dogleg shape and whose pitch length Tj is increased sequentially according to the relationship of <Tz, and the second type of main groove Gz is arranged in a variable pitch. The pitch ratio of the pitch lengths Si/Si _-1 = Pi, Tj/Tj _-1 = Qj are both 1.05 or more and 1.25 or less, and the minimum pitch length T ₁ of the main groove Gz and the main groove Gy The pitch ratio of the maximum pitch length Sy is T ₁ /Sy=
A low-noise tire in which R is smaller than 1.3 and the difference between the maximum and minimum pitch ratios Pi, Qj, and R is 0.15 or less.