JP6752698B2 - Pneumatic tires - Google Patents

Description

Embodiments of the present invention relate to pneumatic tires.

As the noise of the tire, there is a hitting sound of hitting the road surface when the tread part touches the ground. When the tire is stepped on or kicked out, if the timing at which the contact shape and the tread pattern when the tire touches the road surface is constant, the peak of the striking sound is conspicuous. For example, if the pitch length of the tread pattern is constant in the tire circumferential direction, the peak of pitch noise becomes high. Tire noise also includes air column resonance due to the air column formed between the main groove provided in the tread and the road surface, and the frequency of pitch noise and air column resonance at a specific speed. The noise level increases when the frequencies match.

Conventionally, tires that employ a pitch variation in a tread pattern in order to reduce pitch noise have been known (see Patent Documents 1 to 3). However, in the conventional pitch variable arrangement, the types of pitch lengths (that is, the number of variables) in the tire circumferential direction are usually set to 3 types or 5 types, and the effect of lowering the peak of pitch noise cannot be said to be sufficient. It was.

Japanese Patent No. 5614515 Japanese Unexamined Patent Publication No. 2014-221573 Japanese Unexamined Patent Publication No. 2000-043507

In view of the above points, it is an object of the present invention to provide a pneumatic tire capable of lowering the peak of pitch noise by dispersing the frequency and thereby reducing the noise level.

The pneumatic tire according to the embodiment of the present invention has a tire tread portion formed by a plurality of main grooves extending in the tire circumferential direction, a plurality of lateral grooves extending in a direction intersecting the main grooves, and a main groove and a lateral groove. In a pneumatic tire comprising a plurality of land rows having a plurality of portions arranged in the tire circumferential direction, at least one land row comprises a land portion and a lateral groove adjacent to the land portion in the tire circumferential direction. The tire circumferential length of the element is the pitch length, the pitch number which is the number of the elements for one round of the tire is N, and the type k of the pitch length in the tire circumferential direction is N / 4 or more and N or less. P _m-1 / P _m <1.050 and 1.60 ≤ P ₁ /, where P ₁ , P ₂ , ..., P _k are set in order from the largest pitch length, and m is an integer of _{2 to k.} It satisfies the relationship of P _k <2.00.

In one embodiment, it is preferable that the upper limit of the pitch length ratio of the elements adjacent to the at least one land row in the tire circumferential direction is less than 1.71.

Further, in a plurality of land rows provided in the tire tread portion, the type k of the pitch length in the tire circumferential direction is N / 4 or more and N or less, and P _m-1 / P _m <1.050, Moreover, it is preferable to satisfy the relationship of 1.60 ≦ P ₁ / P _k <2.00.

According to the present embodiment, the frequency of the pitch noise is dispersed to lower the peak, and the noise level can be reduced. Further, by lowering the peak of the pitch noise, it is possible to reduce the noise level when the frequency of the pitch noise and the frequency of the air column resonance match.

Development view of the tread pattern of the pneumatic tire according to the embodiment Partial enlarged view of the tread pattern Graph showing the frequency analysis result of area fluctuation

In order to further reduce the peak of pitch noise with respect to the conventional pitch variable arrangement, it is effective to disperse the frequency of pitch noise, and for that, the variable number (that is, the type of pitch length) is conventionally used. It is effective to increase the variable ratio (that is, the ratio of the maximum pitch length to the minimum pitch length). At that time, if the variable ratio is too large, the nth-order component and the second-order component of the noise pitch match and a large noise is generated. Therefore, it is advantageous to increase the variable number while setting a large variable ratio in a range where the nth-order component and the second-order component of the noise pitch do not match in order to reduce the noise level. This embodiment is made based on such knowledge, and the noise level can be further reduced as compared with the conventional pitch variable arrangement.

Hereinafter, this embodiment will be described with reference to the drawings.

FIG. 1 is a developed view showing a tread pattern for one round of the tire with respect to the tread portion of the pneumatic tire according to the embodiment, and FIG. 2 is a partially enlarged view thereof. As shown in FIGS. 1 and 2, on the surface of the tread portion 10 made of tread rubber (that is, the surface that comes into contact with the road surface during traveling), a plurality of main grooves 12 extending in the tire circumferential direction CD intersect with the main grooves 12. A plurality of lateral grooves 14 extending in the direction of the tire and a plurality of land portion rows 18 formed by arranging a plurality of land portions 16 formed by the main groove 12 and the lateral grooves 14 in the tire circumferential direction CD are provided.

In this example, four main grooves 12 are formed at intervals in the tire width direction WD. A pair of left and right center main grooves 12A and 12A located at the center of the tire width direction WD with the tire equator CL in between, and a pair of left and right shoulder main grooves 12B and 12B arranged on both sides thereof. Each of the four main grooves 12 is a straight groove parallel to the tire circumferential direction CD.

In this example, the lateral groove 14 is a groove extending in a direction intersecting the main groove 12 and crossing each land row 18. Therefore, the land portion 16 is formed as a block divided by the lateral groove 14 in the tire circumferential direction CD. The lateral groove 14 does not necessarily have to be parallel to the tire width direction WD as long as it is a groove extending in the tire width direction WD, and may be a groove extending in the tire width direction WD while being inclined.

In the tread portion 10, five land rows 18 are formed by a main groove 12 in the WD in the tire width direction. A center land row 18C sandwiched between a pair of center main grooves 12A and 12A, and a pair of left and right shoulder land rows 18S and 18S located outside the WD in the tire width direction of the pair of shoulder main grooves 12B and 12B, respectively. A pair of left and right mediate land rows 18M and 18M sandwiched between the center main groove 12A and the shoulder main groove 12B. Each land section 18 is formed as a block row in which a large number of lateral grooves 14 are provided at intervals in the tire circumferential direction CD, so that a plurality of blocks, the land portion 16, are arranged in the tire circumferential direction CD. ing.

In the present embodiment, in the above five land rows 18, a land row having a pitch variable arrangement is formed by giving a plurality of different pitch lengths P to the repeating element 20 composed of the land portion 16 and the lateral groove 14. Has been done.

Specifically, in each land row 18, the type (that is, the number of variables) k of the pitch length P in the tire circumferential direction CD is set to N / 4 or more and N or less, where N is the number of pitches for one tire lap. (N / 4 ≦ k ≦ N). When the type k of the pitch length P is N / 4 or more, the frequency of the pitch noise is dispersed and the effect of reducing the noise level can be enhanced. The type k of the pitch length P is preferably as many as possible from the viewpoint of the noise level reduction effect, and therefore is preferably N / 2 or more, and more preferably the pitch length P is changed by all the elements 20, that is, k. = N.

Here, as shown in FIG. 2, the pitch length P is the tire circumferential length of the element 20 including the land portion 16 and the lateral groove 14 adjacent to the land portion 16 on the tire circumferential direction CD. The element 20 is a repeating unit (1 pitch) that constitutes the land row 18, and each land row 18 is formed by arranging elements 20 having a plurality of types of pitch lengths P in the tire circumferential direction CD.

The number of pitches N for one lap of the tire is the number of the elements 20 for one lap of the tire, and is the number of elements arranged over the entire circumference of the tire circumferential direction CD in each land row 18. The number of pitches N is not particularly limited, and may be, for example, 30 to 100, or 40 to 80. In the example shown in FIGS. 1 and 2, the number of pitches N is the same value in the five land rows 18, and N = 56.

In the example shown in FIGS. 1 and 2, the pitch length P is changed for all the elements 20 in the tire circumferential direction CD, that is, k = N is set. As shown by taking the left shoulder land row 18S as an example in FIG. 2, the pitch lengths Pa ₁ , Pa ₂ , Pa ₃ , ..., Pa _N-1 and Pa _N of each element 20 in the tire circumferential direction CD are All are set to different pitch lengths.

In the present embodiment, when the type of pitch length P is k and the pitch length P is P ₁ , P ₂ , ..., P _{k in} order from the largest pitch length P in the above five land rows 18, P The relationship of _m-1 / P _m <1.050 and 1.60 ≦ P ₁ / P _k <2.00 is established (where m is an integer of 2 to _k ).

By setting the variable ratio P ₁ / P _k , which is the ratio of the maximum pitch length P ₁ to the minimum pitch length P _k, to less than 2.00 in this way, the nth-order component and the second-order component of the noise pitch are combined. Therefore, it is possible to suppress the generation of loud noise. Further, by setting the variable ratio P ₁ / P _k to 1.60 or more, it is possible to promote the dispersion of the pitch noise frequency. The variable ratio P ₁ / P _k is preferably 1.80 or more, more preferably 1.90 or more, and preferably 1.98 or less.

Further, by setting the maximum value of the pitch length ratio P _m-1 / P _m to be smaller than 1.050, the effect of dispersing the pitch noise frequency in combination with the above-mentioned variable number and variable ratio setting can be obtained. Can be enhanced. That is, under the condition that the variable number is increased and the variable ratio is set high as described above, setting the maximum value of P _m-1 / P _m to be small means that the minimum pitch length P _{k is the} maximum. This means that there is no extreme variation in the pitch length increment up to the pitch length P ₁ , and the pitch noise frequency can be widely and evenly dispersed to enhance the effect of reducing the pitch noise peak. .. The maximum value of _{P m-1} / P _m is 1.040 or less _{(i.e., P m-1 / P m} ≦ 1.040) is preferably, also 1.010 or more _{(i.e., P m-1} / _P It is preferable that _m ≧ 1.010).

In the present embodiment, the upper limit (that is, the maximum value) of the pitch length ratio of the element 20 adjacent to the tire circumferential CD is preferably less than 1.71. That is, the pitch length of the pitch length is greater element 20A of the two elements 20 adjacent to each other in the tire circumferential direction CD as _{P L,} the pitch length of the pitch length is smaller element 20B as _{P S,} with P L / _{P S} it is preferable upper limit of the pitch length ratio expressed is less than _{1.71 (P L / P S <} 1.71). By defining the upper limit of the pitch length ratio P _{L /} P _S of the thus element 20 adjacent in the tire circumferential direction CD, it is possible to suppress uneven wear due to the rigidity of the land portion 16 is rapidly changed. The upper limit is less than 1.34 of _{P L} / P _{S (i.e., P L / P S <1.34} ) and more preferred from the viewpoint of uneven wear resistance is.

The arrangement (that is, the arrangement) of the elements 20 having a pitch length P of a plurality of types k is not particularly limited. For example, when k = N, the pitch lengths P may be arranged so as to gradually increase in the tire circumferential direction CD. Alternatively, the elements 20 having a pitch length P of a plurality of types k are divided into three groups of large, medium, and small in order from the one having the largest pitch length P, and the elements belonging to the large pitch length group and the elements belonging to the small pitch length group. And may be selected from each group and arranged in the tire circumferential direction CD so as not to be adjacent to each other. Thus, while suppressing decrease the pitch length ratio P _{L /} P _S elements 20 adjacent to each other, can be arranged in the tire circumferential direction CD.

As an example, in the example (k = N) shown in FIG. 1, from the above-mentioned large pitch length group, medium pitch length group, and small pitch length group, in the tire circumferential direction CD, large, medium, small, medium, large, medium, A plurality of elements are assigned in the order of small, medium, large, medium, small, and medium, and arranged so that the pitch length changes smoothly in the tire circumferential direction CD. That is, in one lap of the tire, a group of a plurality of elements belonging to the large pitch length group is provided at three locations on the lap, and a group of a plurality of elements belonging to the medium pitch length group is interposed between each group. , It is an array with a group of multiple elements belonging to the small pitch length group.

According to the present embodiment, as described above, the pitch noise frequency is increased by setting the variable number large while setting the variable ratio large in the range where the nth-order component and the second-order component of the noise pitch do not match. The peak can be lowered by dispersing. Further, by lowering the peak of the pitch noise, it is possible to suppress an increase in the noise level even if the frequency of the pitch noise and the frequency of the air column resonance match. Therefore, the noise level can be effectively reduced as compared with the conventional case.

FIG. 3 is a graph showing the results of frequency analysis of area fluctuations of a 56-pitch variable array, which is an example of the present embodiment, and an equi-pitch array and a 3-pitch variable array as comparative examples. The analysis is performed in accordance with the method described in Japanese Patent Application Laid-Open No. 2003-136926, and the contact pattern of the tire with respect to the road surface is scanned along the circumferential direction of the tread pattern to acquire the variation data of the contact area, and the variation data is obtained. The data of the area fluctuation level with respect to the frequency was acquired by performing the frequency analysis based on. The tire size was 265 / 65R17 and the speed was 80km / h. The tire pattern had a pitch length of 29.1 to 57.68 mm in 0.52 mm increments for the 56 pitch variable arrangement. In the 3-pitch variable arrangement, the pitch lengths were 36.77 mm, 43.77 mm, and 50.33 mm. In the equal pitch arrangement, the pitch length was set to 43.39 mm, which was constant.

As shown in FIG. 3, the frequency of the pitch noise can be dispersed and the maximum level can be reduced by using the 56-pitch variable arrangement as compared with the equi-pitch arrangement and the 3-pitch variable arrangement. Here, in the equi-pitch arrangement, the peak of the primary component near 500 Hz and the peak of the secondary component near 1 kHz are completely separated. On the other hand, in the 56-pitch variable arrangement, the maximum level is reduced by dispersing each of these peaks, and in the present embodiment, the overlap of the dispersed primary component and secondary component is suppressed. , The increase in noise level due to the combination of the two was suppressed. As described above, according to the present embodiment, the noise level is remarkably reduced by increasing the variable number while setting the variable ratio large in the range where the nth-order component and the second-order component of the noise pitch do not match. be able to.

In the above embodiment, the type k of the pitch length P in the tire circumferential direction CD is set to N / 4 or more and N or less in the entire plurality of land rows 18 provided in the tread portion 10, and P _m-1 /. A pitch variable arrangement was adopted so as to satisfy the relationship of P _m <1.050 and 1.60 ≦ P ₁ / P _k <2.00. However, such a pitch variable arrangement may be adopted in at least one land row 18 provided in the tread portion 10. For example, the pitch variable arrangement may be adopted only for the shoulder land row where noise pitch is likely to be a problem, and the conventional three or five types of pitch variable arrangement or equal pitch arrangement may be adopted for the other land rows. ..

In the above embodiment, the same pitch variable arrangement is adopted for the entire plurality of land rows 18. That is, the arrangement order (arrangement pattern) of each element 20 having a plurality of types k of pitch length P in the tire circumferential direction CD is the same arrangement order in all the land rows 18. However, different arrangement orders may be adopted depending on the land row 18, that is, in at least one land row among the plurality of land rows 18, the arrangement of the elements 20 having a pitch length P of a plurality of types k is another. It may be different from the land row of. For example, the pitch variable arrangement may be different from each other by setting the arrangement order in the circumferential direction for each land row 18 while the type of the pitch length P itself is the same for all the land rows 18. By adopting a pitch variable arrangement that differs depending on the land row 18, the pitch noise frequency can be randomly dispersed because each land row 18 is grounded at different timings, and the noise level is more effective. Can be reduced.

In the above embodiment, as shown in FIG. 2, the phase of the element 20 in the tire circumferential direction CD is shifted for each of the plurality of land rows 18. As an example, FIG. 2 shows the phase difference α between the shoulder land row 18S on the right side and the mediate land row 18M adjacent thereto. By shifting the phase in this way, the land portion 16 of each land portion row 18 is grounded at different timings, so that the frequency of the pitch noise can be further dispersed and the noise level can be reduced. It is not necessary that the phases are shifted in all of the plurality of land examples 18, and in at least one of the plurality of land rows 18, the phase of the element 20 in the tire circumferential direction CD is other. It may be set differently from the land row 18.

In the above embodiment, the number of pitches N is set to be the same for the entire plurality of land rows 18, but the number of pitches may differ depending on the land rows 18. That is, at least one of the plurality of land rows 18 may have a different number of pitches from the other land rows 18. Thereby, the frequency of noise determined by the number of pitches can be dispersed.

In the above embodiment, the lateral groove 14 is provided so as to cross each land row 18, but the lateral groove 14 is not necessarily limited to the one provided across the land row 18, and is a factor that generates pitch noise. If so, it may be a groove that does not completely cross the land row 18 but terminates in the middle. Therefore, the land portion 16 does not have to be a block completely divided by the lateral groove 14, and may be connected at a part in the tire width direction.

The tire size was 265 / 65R17, and pneumatic tires having the tread patterns shown in FIGS. In Examples 1 to 5, the type (variable number) k of the pitch length P in each land row, the maximum value of the variable ratio P ₁ / P _k , P _m-1 / P _m , and P _L / P _S. The maximum value is as shown in Table 1, and the basic tread pattern is the same.

Specifically, Example 1 is a variable having 56 types of pitch lengths P in which a minimum pitch length of 29.10 mm and a maximum pitch length of 57.68 mm are evenly divided (in 0.52 mm increments) with a pitch number N = 56. It is an array, that is, an example in which the pitch length is changed for all the elements in the tire circumferential direction (the array is as shown in FIG. 1). In Examples 2 to 4, the minimum pitch length and the maximum pitch length are changed with respect to Example 1 (the average value of both is the same as in Example 1), and the pitch length type k is shown in Table 1. As in the case of the first embodiment, the setting of each pitch length was changed, and the minimum pitch length and the maximum pitch length were evenly divided. In the fifth embodiment, the order of the elements is changed with respect to the first embodiment.

Specifically, in Examples 1 to 4, from the above-mentioned large pitch length group, medium pitch length group, and small pitch length group, in the tire circumferential direction CD, large, medium, small, medium, large, medium, small, medium, A plurality of elements are assigned in the order of large, medium, small, and medium, and arranged so that the pitch length changes smoothly in the tire circumferential direction CD. In the fifth embodiment, from the above-mentioned large pitch length group, medium pitch length group, and small pitch length group, a plurality of elements are each in the order of large, medium, small, large, medium, small, large, medium, and small in the tire circumferential direction CD. Are assigned and arranged so that the pitch length changes abruptly in the tire circumferential direction CD.

The basic tread patterns of Comparative Examples 1 to 3 are the same as those of the examples. In Comparative Example 1, the pitch length is 43.39 mm and the pitch arrangement is equal, and in Comparative Example 2, the pitch length is 32.84 mm. A 3-pitch variable arrangement of 43.78 mm and 54.73 mm was used, and in Comparative Example 3, a 5-pitch variable arrangement of pitch lengths = 32.84 mm, 38.31 mm, 43.78 mm, 49.26 mm, and 54.73 mm was used.

Each of the produced tires was assembled on a rim of 17 × 8.0 J at an air pressure of 193 kPa and mounted on a test vehicle to evaluate noise performance and uneven wear resistance. The evaluation method is as follows.

-Noise performance: The overall value (OAL) when traveling on a noise measurement course at a speed of 80 km / h was measured, and an index evaluation was performed using Comparative Example 1 as a reference (100). The larger the index, the smaller the noise and the better the noise performance.

-Uneven wear resistance: The toe heel wear amount after traveling a specified distance in an actual vehicle was measured and index-evaluated using Comparative Example 1 as a reference (100). The larger the index, the smaller the toe heel wear amount and the uneven wear resistance. Shows good.

結果は、表１に示す通りであり、実施例１〜５であると、等ピッチ配列の比較例１に対してはもちろんのこと、３ピッチバリアブル配列の比較例２及び５ピッチバリアブル配列の比較例３に対しても、ノイズ性能が改善されていた。また、Ｐ_Ｌ／Ｐ_Ｓの最大値を小さく設定した実施例１〜４では、実施例５に対して耐偏摩耗性も改善された。

The results are as shown in Table 1, and in Examples 1 to 5, not only the comparison example 1 of the equi-pitch arrangement but also the comparison example 2 of the 3-pitch variable arrangement and the comparison of the 5-pitch variable arrangement. The noise performance was also improved with respect to Example 3. In Examples 1 to 4 was set to a small maximum value of P L _/ P _S, it is improved uneven wear resistance for Examples 5.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

10 ... Tread part, 12 ... Main groove, 14 ... Horizontal groove, 16 ... Land part, 18 ... Land part row, 20 ... Element, P ... Pitch length

Claims (6)

In the tire tread portion, a plurality of main grooves extending in the tire circumferential direction, a plurality of lateral grooves extending in a direction intersecting the main groove, and a plurality of land portions formed by the main groove and the lateral groove are arranged in the tire circumferential direction. In pneumatic tires with treads and
At least one land row is the number of the elements for one tire circumference, with the tire circumference length of the element consisting of the land portion and the lateral groove adjacent to the land portion in the tire circumferential direction as the pitch length. The number of pitches is N, the type k of the pitch length in the tire circumferential direction is N / 4 or more and N or less, and P ₁ , P ₂ , ..., P _k are set in order from the largest pitch length, and m is 2. A pneumatic tire satisfying the relationship of P _m-1 / P _m <1.050 and 1.60 ≤ P ₁ / P _k <2.00 as an integer of ~ _k . The pneumatic tire according to claim 1, wherein the at least one land row has an upper limit of the pitch length ratio of the elements adjacent to the tire circumferential direction to be less than 1.71. In a plurality of land rows provided in the tire tread portion, the type k of the pitch length in the tire circumferential direction is N / 4 or more and N or less, and P _m-1 / P _m <1.050 and The pneumatic tire according to claim 1 or 2, which satisfies the relationship of 1.60 ≦ P ₁ / P _k <2.00. The pneumatic tire according to claim 3, wherein at least one of the plurality of land rows has an arrangement of the elements having a plurality of types of pitch lengths different from that of the other land rows. The pneumatic tire according to claim 3 or 4, wherein at least one of the plurality of land rows has a phase of the element in the tire circumferential direction different from that of the other land rows. The pneumatic tire according to any one of claims 3 to 5, wherein at least one of the plurality of land rows has a pitch number different from that of the other land rows.

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