JP2005035391A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire eliminating discomfort caused by changes with time of noise due to a tread pattern, and excellent in its development efficiency. <P>SOLUTION: In the pneumatic tire, a pattern structuring element line 6 made by arranging pattern structuring elements 5a to 5e having a several kinds of pitch lengths in a tire circumferential direction is provided in a tread pattern. When an arrangement of the pattern structuring element according to sinusoidal waves that forms one peak and one trough by the number n of total pitches in the pattern structuring element is made to be a primary harmonic arrangement, the pattern structuring element line 6 is composed of four segments 7A to 7D made by arranging the pattern structuring elements 5a to 5e according to each of 5th order, 7th order, 9th order, and 11th order arrangements. At that time, the number n of the total pitches is preferably distributed to each segment so as to make four segments 7A to 7D have generally same energy. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire, and particularly to a pneumatic tire excellent in noise performance due to a tread pattern.

  In a pneumatic tire having a plurality of vertical grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction on the tread surface and having a block surrounded by the vertical grooves and the horizontal grooves, the pneumatic tire is caused by a tire tread pattern at the time of ground contact In order to reduce noise, a so-called variable pitch arrangement type tread pattern that arranges multiple types of blocks with different circumferential pitch lengths on the tire circumference is adopted, and the frequency of pattern noise (pitch noise) generated during vehicle running The noise level is reduced by decentralization.

  For example, Patent Document 1 discloses that a tread is divided into harmonic segments, and a pitch arrangement that follows a sine wave, that is, a harmonic arrangement is introduced into each segment. More specifically, it is disclosed that the size of each segment is divided so as to correspond to each term of 1/4, 1/5, 1/6, 1/7, and 1/8 of the harmonic sequence.

  Further, in Patent Document 2, in such a harmonized pneumatic tire, in order to reduce vibration or bead noise due to the periodicity of pitch arrangement, the arrangement of blocks is substantially related to the tire equator and / or longitudinal grooves. It is disclosed to provide an upper mirror symmetry periodicity.

  By the way, in the examination of tire noise, it is not sufficient to capture only the noise level (sound pressure), and it is necessary to consider the sound quality characteristics. Based on this knowledge, various arrangements of desktop simulation methods and mathematical methods (genetic algorithms, chaos functions, etc.) were introduced for the pitch arrangement, which is the order of pitches used on the tire circumference. Thus, a method for determining a pitch arrangement configuration having excellent sound quality characteristics has been proposed, and the sound quality characteristics of pitch noise have been improved (see, for example, Patent Documents 3 and 4).

However, in determining the number of variable pitches of the tread pattern, each pitch length, and pitch arrangement configuration, they also affect the wear performance and uniformity performance of the tire, so improvements are made within the allowable range. Things are necessary.
JP 54-115801 A JP 2000-85317 A Japanese Patent Laid-Open No. 11-20411 JP 2001-130224 A

  In recent years, approaches to designing quiet tread pattern configurations have become theoretical, and many optimizations are performed by desktop arithmetic processing that combines desktop simulation and mathematical techniques, but each tread pattern (size) is examined. In the case where such a method is used while checking other performances, it is not realistic in terms of man-hours and efficiency, and it is difficult to easily determine an excellent pitch arrangement configuration in a short time.

  The present invention has been made in view of the above points, eliminates discomfort due to temporal fluctuations in noise caused by the tread pattern, and can further determine the determined pitch arrangement configuration uniformly in a short time. The object is to provide a pneumatic tire with excellent development efficiency.

  The present inventor has studied a method for defining an arrangement by a harmonic function for a pattern pitch arrangement configuration applied for the purpose of reducing tread pattern noise. A combination of harmonic function sequences having the order) was found, and the present invention was completed.

  That is, the pneumatic tire of the present invention is a pneumatic tire provided with a tread pattern having a pattern component row in which pattern components having a plurality of types of pitch lengths are arranged in the tire circumferential direction. When the arrangement of pattern constituent elements following a sine wave forming one peak and valley with the total number of pitches is a primary harmonic arrangement, the pattern constituent element rows are each of the fifth, seventh, ninth and eleventh orders. It is composed of four segments formed by arranging the pattern constituent elements according to a harmonic arrangement.

  Here, the harmonic arrangement means an arrangement in which pattern constituent elements are arranged so that their circumferential lengths (that is, pitch lengths) change sinusoidally in the tire circumferential direction.

  In the pneumatic tire of the present invention, it is preferable that the total number of pitches of the pattern constituent elements is distributed to each segment so that the four segments have substantially the same energy.

  In the pneumatic tire of the present invention, discomfort due to the temporal variation in noise caused by the tread pattern can be reduced by the arrangement configuration of the pattern arrangement elements described above. In addition, since it is not necessary to determine the arrangement configuration by a complicated desktop arithmetic processing combining a desktop simulation and a mathematical method for each tread pattern, an excellent pitch arrangement configuration can be easily determined in a short time. Excellent development efficiency.

  Hereinafter, the present invention will be described in more detail with reference to the drawings.

  FIG. 1 is a plan view showing a tread pattern of a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is a schematic side view of the tire.

  The tire includes a plurality of longitudinal grooves 1 extending in the circumferential direction on the tread, specifically six longitudinal grooves 1. Of the six rows of land portions defined by the vertical grooves 1 or the tread ends 2, each of the two rows of land portions at both ends is divided into a plurality of blocks by lateral grooves 3 arranged at intervals in the tire circumferential direction. 4 is formed. A pattern component 5 is formed by the block 4 and one lateral groove 3 adjacent thereto, and a block row 6 that is a pattern component row is formed by arranging the pattern components 5 in the tire circumferential direction. .

  For each block row 6, the pattern component 5 has five variable pitch lengths. That is, one block row 6 is configured by arranging five types of pattern constituent elements 5a to 5e which are different only in the pitch length which is the circumferential length and have other shapes in common. The ratio of the pitch length, that is, the ratio between the maximum value and the minimum value of the pitch length is not particularly limited, but is preferably the maximum value / minimum value = 1.1 to 1.7. The variable pitch length is not limited to five types as long as it is a plurality of types, and may be three types or seven types, for example.

  In the present embodiment, the pattern components 5a to 5e are arranged in the tire circumferential direction according to the following arrangement configuration.

  That is, when the array of the pattern constituent elements 5 following a sine wave that forms one peak and valley with the total number of pitches of the pattern constituent elements 5 is defined as a primary harmonic array, the block array 6 that is the pattern constituent elements is: It consists of four segments 7A, 7B, 7C, and 7D in which pattern components 5a to 5e are arranged according to the fifth, seventh, ninth, and eleventh harmonic arrangements (see FIG. 2). More specifically, when the number of pattern pitches per tire is n, the harmonic arrangement of the pattern components 5 that forms a sine wave having one peak and a valley with the n pattern components 5 is as follows. Defined as primary. And when defined in this way, the block row 6 is divided into four segments 7A, 7B, 7C, and 7D in the tire circumferential direction. The segment 7A has a fifth order harmonic array, the segment 7B has a seventh order harmonic array, The pattern components 5a to 5e are arranged in accordance with the 9th order harmonic arrangement in 7C and the 11th order harmonic arrangement in the segment 7D, respectively, and these four segments 7A to 7D are connected in the tire circumferential direction. It has a pitch arrangement configuration.

  Further, when the segments 7A to 7D are coupled, the segments are arranged so as not to cause a sudden pitch variable change between the segments of the coupling portion, that is, to prevent the pitch lengths of the adjacent pattern components from abruptly changing. The phase is adjusted within and combined.

  Furthermore, when dividing into four segments 7A, 7B, 7C, 7D, the total number of pitches of the pattern component 5 so that each segment has substantially the same energy, that is, the energy of each segment can be made uniform. n is allocated to each segment 7A-7D. More specifically, each segment is distributed so as to have an energy of 25% ± α%, assuming that the energy for one round of the tire is 100%. Here, α = 0 is preferable, but since the actual number of pitches is a discrete value, α ≦ 5 may be satisfied.

  FIG. 3 and FIG. 4 are diagrams showing an example of a pitch arrangement configuration including such four segments 7A to 7B. In the arrangement example of FIG. 3, the fifth order segment 7A, the seventh order segment 7B, the ninth order segment 7C, and the eleventh order segment 7D are combined in this order. In the arrangement example of FIG. The ninth-order segment 7C, the seventh-order segment 7B, and the eleventh-order segment 7D are combined in this order.

  In order to make the energy of the segments 7A to 7D uniform as described above, the number of pitches of each segment may be set as follows. Here, n is the total number of pitches of the pattern constituent elements.

5th order segment 7A = 5n / 32 (pieces)
7th order segment 7B = 7n / 32 (pieces)
9th segment 7C = 9n / 32 (pieces)
11th-order segment 7D = 11n / 32 (pieces)
In addition, since the number of pitches must be an integer, when each of the above values is not an integer, it is adjusted to be rounded up or down to an integer by rounding off or the like and the total is n.

  The number of pitches of the segments 7A to 7D is determined as follows.

First, generally, the energy of the wave increases as the frequency of the low frequency wave increases, and the energy ratio is proportional to the reciprocal of the frequency. 7th order: 9th order: 11th order = 1/5: 1/7: 1/9: 1/11. From this, the energy ratio of one cycle of each order is 1/49 in the 7th order, 1/81, 11 in the 9th order, assuming that the case of the 5th order is (1/5) / 5 = 1/25. Next, it becomes 1/121. Therefore, the ratio of the periods (cycles) required to have the same energy is the inverse ratio, that is, 5th: 7th: 9th: 11th = 25: 49: 81: 121. The number of pitches required to constitute one period of each order is n / 5 for the 5th order, n / 7 for the 7th order, n / 9 for the 9th order, and n / 11 for the 11th order. As shown in Table 1, the ratio of the number of pitches required to have the same energy is 5th: 7th: 9th: 11th = 5: 7: 9: 11. Therefore, the number of pitches that can equalize the energy of the segments of each order is the number described above (see Table 1).

  For example, when the total number of pitches of the pattern component 5 is n = 60 (pieces), as shown in Table 1, there are 9.375 fifth-order segments, 13.125 seventh-order segments, and ninth-order segments. Since the number of segments is 16.875 and the number of 11th-order segments is 20.625, they are rounded to 9, 13, 17, and 21, respectively. If distributed, the energy of each segment can be made uniform.

  When the energy ratio of each of the actual segments allocated in this way is obtained, the number of pitches in the fifth-order segment is 9, so the actual period is 9 ÷ (60/5) = 0.75. . Similarly, the actual period of each order is 13 ÷ (60/7) = 1.52 for the 7th order segment, 17 ÷ (60/9) = 2.55 for the 9th order segment, and 11th order segment. 21 ÷ (60/11) = 3.85. By multiplying these periods by the energy ratio of each order for one period, and calculating the energy ratio of each segment with the energy for one lap of the tire as 100%, as shown in Table 1, 24 for the fifth order segment. .1%, 24.9% for the 7th segment, 25.3% for the 9th segment, and 25.6% for the 11th segment, all within the range of 25% ± 5% . Therefore, it can be seen that the energy is made uniform by allocating to the number of pitches.

  The total number of pitches n of the pattern constituent elements is not particularly limited, but is usually set within a range of 20 to 80.

  The pitch arrangement configuration described above is excellent in sound quality characteristics resulting from pattern pitch noise. The sound quality characteristic caused by the pattern pitch noise here is mainly dispersed by the variable pitch length, and shows an uncomfortable feeling when the noise in the pitch noise frequency band generated depending on the tire rotation speed varies with time. Therefore, with the pitch arrangement configuration described above, this sound quality characteristic can be improved and uncomfortable feeling can be reduced.

  In the above, the significance of setting the minimum order of the harmonic frequencies included in the pitch arrangement configuration to the fifth order, that is, 1/5 of the number of pitches n, depends on human auditory characteristics and is smaller than 30 cycles (30 Hz) per second. The frequency is usually not in the audible range, but is because it can be detected as a beat sound when the noise level of a predetermined frequency varies in the above cycle. That is, when the minimum order is third order, if the rotational speed of the tire is about 10 times / second, a frequency of about 30 Hz is detected, which is detected as a beat sound and gives a sense of temporal variation in noise. . On the contrary, the reason why the maximum order of the harmonic frequencies included in the pitch arrangement configuration is 11th is to prevent a sudden change between pitch variables in the entire pitch arrangement.

  Further, the harmonic frequencies included in the pitch arrangement configuration are set to 1/5, 1/7, 1/9, and 1/11 of the number of pitches n, that is, the orders of the harmonic arrangement are 5th, 7th, and 9th. The significance of the 11th order is to eliminate the alternating resonance characteristics of the pitch arrangement of each segment and to obtain excellent sound quality characteristics.

  Also, by making the energy of each segment uniform as described above, the level of sound generated by each segment can be made uniform, and the sense of sound fluctuation can be reduced more effectively.

  In addition, by adopting the above pitch arrangement configuration, it is possible to avoid uneven distribution of blocks with a large pitch length or blocks with a small pitch length on a part of the tire circumference. On the other hand, changes in tire wear performance and uniformity performance can be kept at an acceptable level.

  In the above-described embodiment, the four block rows 6 are provided with the total number of the pattern components 5 and the arrangement of the pattern components 5 being the same, with only the phases being different. However, the total number of pattern constituent elements 5 in the tire circumferential direction is the same, and the arrangement of the pattern constituent elements 5 can be varied (for example, the order of coupling of the fifth, seventh, ninth, and eleventh orders is changed).

  Moreover, the pattern component row | line | column which takes the above-mentioned pitch arrangement structure is not limited to the block row | line | column 6 comprised from the above blocks 4, As long as it has the repeating unit of the same pattern, it will be in addition to a block row | line | column. Can also be applied.

  In the pneumatic tire for a passenger car having the tread pattern shown in FIG. 1 (tire size: 195 / 65R15), the pitch arrangement configuration shown in FIG. Example 7 was a tire in which the pattern constituent elements 5a to 5e were arranged according to (7th order → 9th order → 11th order). Similarly, Example 2 is a tire in which the pattern components 5a to 5e are arranged according to the pitch arrangement configuration shown in FIG. 4 (the order of the composite waveform: 5th order → 9th order → 7th order → 11th order). Further, the tire in which the pattern components 5a to 5e are arranged according to the pitch arrangement configuration (third order harmonic arrangement) shown in FIG. 5A is a comparative example 1, and the pitch arrangement configuration shown in FIG. The tire in which the pattern components 5a to 5e are arranged according to the extracted excellent arrangement configuration) is compared with the tire arrangement in which the pattern components 5a to 5e are arranged according to the comparative example 2, and the pitch arrangement configuration (worst arrangement configuration extracted by random number generation) shown in FIG. The tire in which was arranged as Comparative Example 3.

  About each tire of Example 1, 2 and Comparative Examples 1-3, the noise characteristic was evaluated by desktop simulation. In the desktop simulation, the tread pattern arranged according to the pitch arrangement configuration is scanned by the ground shape based on the method described in Japanese Patent Application Laid-Open No. 2003-136926 to create a fluctuation line, and an artificial line is obtained from the obtained fluctuation line. Sound was generated, and the sound quality characteristics were evaluated by calculating the sound quality evaluation indexes of loudness, sharpness, and tonality using a commercially available sound quality analysis tool. As shown in Table 2, the result is an index display in which Comparative Example 1 is set to 100, and a smaller numerical value means better sound quality performance. In addition, FFT in a table | surface is Fast Fourier transformation and shows the noise characteristic in all the waveform levels of a frequency analysis.

  Further, for each of the obtained tires, an actual vehicle sensory evaluation was performed to evaluate the noise fluctuation. In the actual vehicle sensory evaluation, each tire is mounted on a sedan-type passenger car, and the sense of fluctuation of the vehicle interior noise when driving at a constant speed (40 km / h) on a road surface with road surface characteristics that make the tire pattern noise clear is sensory. evaluated. The result is an index display in which Comparative Example 1 is set to 100, and the larger the numerical value, the smaller the sound fluctuation and the better.

表２に示すように、実施例１，２のタイヤでは、机上シミュレーション結果における音質特性に優れ、また、実車官能評価でも音の変動感による不快感が低減されていた。しかも、摩耗性を損なうものではなかった。 Further, the wear properties of the obtained tires were evaluated. For the wearability, each tire was mounted on a sedan type passenger car, traveled on a general road at a specified air pressure, and the amount of wear after traveling 10,000 km was evaluated. The result is an index display in which Comparative Example 1 is set to 100, and the larger the value, the smaller the amount of wear and the better.

As shown in Table 2, the tires of Examples 1 and 2 were excellent in sound quality characteristics in the desktop simulation results, and the discomfort due to the sense of sound fluctuation was reduced even in the actual vehicle sensory evaluation. In addition, the wearability was not impaired.

It is a partial top view of the tread pattern of the tire which concerns on one Embodiment of this invention. It is a side schematic diagram of the tire. FIG. 3 is a diagram illustrating a pitch arrangement configuration of the first embodiment. It is a figure which shows the pitch arrangement | sequence structure of Example 2. FIG. (A) is a figure which shows the pitch arrangement structure of the comparative example 1, (b) is a figure which shows the pitch arrangement structure of the comparative example 2, (c) is a figure which shows the pitch arrangement structure of the comparative example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vertical groove 2 ... Tread edge 3 ... Horizontal groove 4 ... Block 5, 5a-5e ... Pattern component 6 ... Block row (pattern component row)
7A: Segment of fifth order harmonic array 7B: Segment of seventh order harmonic array 7C: Segment of ninth order harmonic array 7D: Segment of 11th order harmonic array

Claims (2)

A pneumatic tire comprising a tread pattern with a pattern component row in which pattern components having a plurality of types of pitch lengths are arranged in the tire circumferential direction,
When the arrangement of the pattern constituent elements following a sine wave that forms one peak and valley with the total number of pitches of the pattern constituent elements is a primary harmonic array, the pattern constituent element rows are the fifth, seventh, and ninth orders. And a pneumatic tire characterized in that it is composed of four segments in which the pattern constituent elements are arranged in accordance with the 11th order harmonic arrangement.   The pneumatic tire according to claim 1, wherein the total number of pitches of the pattern constituent elements is distributed to each segment so that the four segments have substantially the same energy.

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