JP4589058B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire capable of reducing tire noise.

  In general, in a pneumatic tire, a plurality of circumferential grooves called main grooves extending in the tire circumferential direction are provided in a tread portion, and a running performance on a wet road surface, that is, wet performance is secured by a drainage effect of the grooves. However, when such a circumferential groove is provided, air is repeatedly discharged, compressed, and re-introduced through the circumferential groove that forms a columnar shape between the tread surface and the road surface during traveling, so that air columnar resonance noise, so-called Air pumping noise is generated, which is a major factor that adversely affects tire noise.

  Conventionally, in order to reduce such air columnar resonance noise, it has been practiced to suppress the generation of noise by bending or bending the circumferential groove in the tread width direction or reducing the groove volume. However, there is a problem that extreme bending and bending and extreme groove volume reduction cause a decrease in wet performance.

  In addition, by providing a partition that blocks the groove in the circumferential groove, or by providing soundproofing pieces that alternately protrude from the side wall of the circumferential groove in a zigzag manner, the flow of air in the groove is suppressed. Measures to reduce air columnar resonance noise (see Patent Documents 1 to 3) and the formation of wall portions that are continuous in the circumferential direction smaller than the groove depth in the circumferential groove, thereby suppressing the propagation of air into the groove. In addition, measures have been proposed to reduce air columnar resonance sound by dispersing frequency components of resonance sound (see Patent Documents 4 and 5). In these conventional technologies, it is pointed out that there is a contradiction between wet performance and noise performance, and it is an issue to make both performances compatible, but in order to meet recent demands for severe noise performance Needs further improvement.

Conventionally, projections protruding from the groove bottom that are effective for preventing stone biting are used to change the height of the projections and arrange them in a pattern in which irregularities are repeated along the tire circumferential direction, thereby reducing outside noise. There has also been proposed a measure (see Patent Document 6). In this prior art, since the protrusions are linearly arranged in a line along the tire circumferential direction, the tire noise suppression effect due to air columnar resonance may not be sufficient, and further improvement is required.
Japanese Patent Laid-Open No. 61-113504 JP-A-11-2117007 JP-A-5-169920 Japanese Patent Laid-Open No. 10-86611 JP-A-6-48124 JP 2002-211210 A

  The present invention has been made in view of the above points, and by exhibiting an excellent suppression effect on air columnar resonance noise by limiting the arrangement of protrusions protruding from the groove bottom effective for stone biting prevention effects. And it aims at providing the pneumatic tire which can aim at reduction of a tire noise, ensuring stone biting prevention performance and wet performance.

  The present inventor has scrutinized the relationship between the arrangement in the tire circumferential direction and the groove width direction of the protrusion protruding from the groove bottom of the circumferential groove effective for the stone biting prevention effect and the effect of suppressing the air column resonance noise. In the course of the course, it was found that the air columnar resonance noise was effectively suppressed by adopting a uniform barrier wall configuration for the groove width direction component and a non-uniform barrier wall configuration for the tire circumferential direction component, The present invention has been completed.

Engaging Ru pneumatic tire of the present invention is the pneumatic tire having a circumferential groove comprising a straight groove extending in the tire circumferential direction in a tread, side by side a plurality of projections in the tire circumferential direction in the groove bottom of the circumferential groove The plurality of protrusions are arranged such that the non-projection portions on the groove bottom surface are continuous in the tire circumferential direction, and are arranged in a state of alternately swinging left and right with respect to the center line in the width direction of the circumferential groove. In the circumferential groove, the protrusions arranged close to the left groove wall and the protrusions arranged close to the right groove wall are alternately arranged in the tire circumferential direction, and between the adjacent protrusions, the tire circumference no overlapping portions in the direction, and, in the groove width direction are arranged so as to have an overlapping portion, further, the plurality of protrusions, the standard deviation of the area change in the tire circumferential direction of the non-projecting portion α And, wherein the standard deviation of the area change in the groove width direction of the non-projecting portion as beta, characterized in that it is arranged so as to satisfy the (β / α) ≦ 15.

  Α is an area of a non-protrusion portion (that is, a groove portion where no protrusion is formed) on the groove bottom surface along a groove width direction line at predetermined intervals in the tire circumferential direction in a circumferential range corresponding to the tire contact length. Is a value obtained by calculating the standard deviation of the area of the calculated non-projection part, and is an index of the degree of protrusion dispersion in the tire circumferential direction (that is, the area occupancy of the projection part and the non-projection part) Is. Further, β is the area of the non-protrusion portion obtained on the groove bottom surface along the tire circumferential direction line at predetermined intervals in the groove width direction in the circumferential range corresponding to the tire contact length. Is a value obtained by calculating the standard deviation of the projection, and serves as an index of the degree of dispersion of the protrusions in the groove width direction. In order to suppress the air column resonance noise, the projections serving as blocking walls are uniformly dispersed (that is, β is small) in the groove width direction, and the projections serving as blocking walls are non-uniform in the tire circumferential direction. Dispersion (that is, α is large) is effective, and by setting β / α, which is the ratio of the two, to 15 or less, it is excellent for air column resonance noise, that is, noise due to air pumping action. Suppressing effect can be obtained. Here, the tire contact length is a measured value under the condition of applying the working air pressure and the load specified according to the tire size in JATMA (Japan Automobile Tire Association Standard), and the contact length is measured on the surface of the tire tread. Ink is applied to the surface of the mount and the tire is grounded and transferred on the road surface under the above conditions.

  Further, by uniformly dispersing the protrusions in the groove width direction, it is possible to secure a stone biting prevention effect. Further, the plurality of protrusions are arranged such that the non-protrusion portions on the groove bottom face are continuous in the tire circumferential direction. By arrange | positioning to, the drainage property of the circumferential groove | channel can also be ensured.

Further, the plurality of protrusions alternately swing left and right with respect to the center line in the width direction of the circumferential groove, and the adjacent protrusions do not have an overlapping portion in the tire circumferential direction and overlap in the groove width direction. Since the projections that serve as blocking walls are distributed relatively uniformly in the groove width direction, and the projections that serve as blocking walls are unevenly distributed in the tire circumferential direction, It becomes easy to set the β / α to 15 or less, so that it is possible to obtain an excellent suppression effect on the air column resonance noise, and also to ensure the stone biting prevention effect and the circumferential groove drainage.

  In the pneumatic tire of the present invention, the height of the protrusion from the groove bottom is preferably 20 to 50% of the depth of the circumferential groove. Such protrusions are preferably as high as possible from the viewpoint of noise performance, but if they are too high, wet performance will be impaired, so it is preferable to set the protrusion within the above range.

  Further, in the pneumatic tire of the present invention, the ratio of the area of all protrusions to the entire groove bottom surface of the circumferential groove is 20 to 30%, which improves the wet performance and the stone biting performance while enhancing the noise performance. It is preferable in securing.

  According to the present invention, as described above, by limiting the arrangement of the protrusions protruding from the groove bottom effective for the stone biting prevention effect, the air columnar resonance sound is secured while ensuring the stone biting prevention performance and the wet performance. The tire noise can be reduced by exhibiting an excellent suppressing effect on the tire.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a partial development view of a tread pattern of a pneumatic tire according to an embodiment of the present invention. Reference numeral 1 denotes a circumferential groove provided in the tread extending in the tire circumferential direction, reference numeral 2 denotes a lateral groove provided in the tire width direction, and reference numerals 3 and 4 denote ground contact ends of shoulder portions located on both sides of the tire. A plurality of circumferential grooves 1, four in this embodiment, are provided, and three ribs sandwiched between the circumferential grooves 1 are provided with lateral grooves 2 at predetermined intervals in the tire circumferential direction. A plurality of blocks 5 are formed.

  In the circumferential groove 1, a plurality of protrusions 6 are intermittently provided on the groove bottom side by side in the tire circumferential direction. As shown in FIG. 2, the protrusions 6 are arranged in a state of being alternately swung left and right with respect to the center line CL in the width direction of the circumferential groove 1. That is, in the circumferential groove 1, the projections 6 are alternately arranged in the tire circumferential direction with projections 6L arranged close to the left groove wall 11 and projections 6R arranged close to the right groove wall 12. It is formed so as to be arranged.

  Moreover, the protrusions 6 are arranged between the adjacent protrusions 6L and 6R so as not to overlap each other in the tire circumferential direction and to overlap each other in the groove width direction. That is, the adjacent protrusions 6L and 6R are arranged such that their shadows do not overlap when both 6L and 6R are projected onto a plane perpendicular to the groove width direction (a plane parallel to the tire circumferential direction). , 6R are arranged at a distance in the tire circumferential direction. Further, when the adjacent protrusions 6L and 6R are projected onto a plane perpendicular to the tire circumferential direction (a plane parallel to the groove width direction), they are arranged so that their shadows overlap (see FIG. 3).

  By arranging the plurality of protrusions 6 in this way, as shown in FIG. 2, the non-protrusion portion 7, which is a groove portion where the protrusion 6 is not provided, is formed on the tire bottom surface of the circumferential groove 1. It is continuous over the entire circumference in the circumferential direction, thereby ensuring drainage.

  In this embodiment, the protrusion 6 has a prismatic shape protruding from the bottom surface of the groove, and the horizontal cross section thereof is such that both ends 6a and 6b in the tire circumferential direction are parallel to the groove width direction and on both sides in the groove width direction. It has a hexagonal shape with apex angles 6c and 6d. Such a hexagonal shape is advantageous in terms of noise performance because the apex angles 6c and 6d on both sides in the groove width direction can suppress abrupt fluctuations in the area of the non-projection portion 7 in the groove width direction. In addition, the inclined surfaces on both sides of the projection 6 are advantageous in terms of drainage. The shape of the protrusion 6 is not limited to such a hexagonal shape, and may be, for example, a rectangular shape as shown in FIG. 6A, more specifically a rectangular shape that is long in the tire circumferential direction. 6 (b) may have a parallelogram shape in which the left and right sides are inclined with respect to the tire circumferential direction.

  As shown in FIG. 3, in the present embodiment, the height H of the protrusion 6 is set within a range of 20 to 50% of the depth D of the circumferential groove 1. When the height H of the protrusion 6 is less than 20% of the depth D of the circumferential groove 1, the effect of suppressing air columnar resonance noise is poor. Conversely, if it exceeds 50%, the wet performance will be impaired.

  Further, in the present embodiment, the ratio of the area of all the protrusions 6 occupying the entire groove bottom surface of the circumferential groove 1 (the total value of the areas of all the protrusions) is set within a range of 20 to 30%. . If the total arrangement area of the protrusions 6 is less than 20% of the entire groove bottom, it is difficult to ensure noise performance and stone biting performance, and if it exceeds 30%, it is difficult to ensure wet performance.

In the present embodiment, the plurality of protrusions 6 has a standard deviation of the area change in the tire circumferential direction of the non-projection part 7 as α, and a standard deviation of the area change in the groove width direction of the non-projection part 7. As β
(Β / α) ≦ 15 (1)
It is arranged to satisfy.

  Here, the standard deviation α is obtained as follows. That is, as shown in FIG. 4A, in the circumferential range corresponding to the tire contact length, the area of the non-projection portion 7 on the groove bottom surface along the groove width direction line L1 at every predetermined interval in the tire circumferential direction. Ask for. For example, the area of the non-projection part 7 is obtained by scanning along the groove width direction line L1 every 0.18 mm in the tire circumferential direction within a range of 160 mm corresponding to the contact length. Thereby, as shown to Fig.5 (a), the area fluctuation | variation of the non-protrusion part 7 in a tire peripheral direction is calculated | required. Next, using the area data for each predetermined interval in the tire circumferential direction of the non-protrusion portion 7 obtained in this way, each deviation is squared, and the variance is obtained by arithmetically averaging it, and the positive square root is calculated. By doing so, the standard deviation α is obtained.

  Also, the standard deviation β is obtained as follows. That is, as shown in FIG. 4B, the circumferential direction corresponding to the tire contact length along the tire circumferential direction line L2 at predetermined intervals in the groove width direction (the same interval as when the standard deviation α is obtained). The area of the non-projection part 7 on the groove bottom surface in the range is obtained. For example, the area of the non-protrusion portion 7 is obtained by scanning within the range of 160 mm corresponding to the contact length along the tire circumferential direction line L2 every 0.18 mm in the groove width direction. Thereby, as shown in FIG.5 (b), the area fluctuation | variation of the non-projection part 7 in a groove width direction is calculated | required. Then, using the area data for each predetermined interval in the groove width direction of the non-projection portion 7 obtained in this way, each deviation is squared, and the variance is obtained by arithmetically averaging the deviations, and the positive square root is calculated. As a result, the standard deviation β is obtained.

  The above formula (1) is obtained by analyzing the relationship between the degree of dispersion in the groove width direction and the tire circumferential direction of the protrusions and the effect of suppressing the air column resonance noise (air pumping phenomenon) for various protrusion arrangement configurations. It is a thing. The details are as follows.

  The above-described protrusion arrangement configuration (arrangement A) shown in FIG. 2, the protrusion arrangement arrangement (arrangement B) and (arrangement C) shown in FIG. 6, the protrusion arrangement arrangement (arrangement D), (arrangement E) shown in FIG. With respect to (Arrangement F), the standard deviations α and β were obtained and the radiated sound level was measured. At that time, each protrusion arrangement configuration was adjusted to have the same space volume in the groove (the groove width in the arrangement A was 17.5 mm, the groove depth was 16.5 mm, the protrusion height) The thickness was 6.6 mm). Further, the scanning interval for obtaining the standard deviations α and β was set to 0.18 mm. Further, as shown in FIG. 7A, the radiated sound level was measured for a section having a predetermined length of the circumferential groove by placing a sound source at one end and using the other end as an observation point. More specifically, pneumatic tires having a tire size: 11R22.5 14PR having respective protrusion arrangement configurations were respectively produced, and a prescribed load was applied to each tire and grounded on the road surface. And, while arranging a small speaker as a sound source on one end side of the circumferential groove in the grounding portion, a “probe microphone” manufactured by GRAS (microphone with a thin tip) is arranged on the other end side, A sound that was converted to white noise (artificial sound with a flat frequency characteristic of 60 Hz to 4 kHz) was emitted from the sound source, and the radiated sound was measured with a microphone, and the radiated sound level of the air column resonance frequency was observed by frequency analysis. In the case of the tire size described above, the air pressure and load specified by JATMA are 700 kPa and 2725 kg (single wheel use, maximum load capacity condition), respectively. Since the circumferential groove length at the portion was 160 mm, the above scanning was performed in this circumferential range. The distance between the sound source and the observation point was 190 mm.

  The result is as shown in FIG. 8, and there is a correlation between the radiated sound level and β / α (correlation coefficient R is about 0.92. For reference only, the correlation coefficient is 0. 48), it was found that the smaller this value, the lower the radiated sound level, that is, the better the effect of suppressing the air columnar resonance. In order to suppress the air column resonance noise, the projections that become the blocking walls are uniformly dispersed (that is, the standard deviation β is small) in the groove width direction, and the blocking walls in the tire circumferential direction. It means that it is effective that the protrusions are dispersed unevenly (that is, the standard deviation α is large). And it was found that by setting β / α to 15 or less, excellent noise performance can be exhibited in an actual tire. Β / α is more preferably set to 10 or less, and still more preferably 5 or less. The lower limit of β / α is not particularly limited, and therefore β / α is 0 or more.

  In the pneumatic tire according to the present embodiment described above, the protrusions 6 provided on the groove bottom of the circumferential groove 1 are alternately arranged in a staggered pattern on the left and right sides, and the groove width direction is relatively uniformly cut off. Since the projections 6 are arranged so as to be cut off unevenly, an excellent suppression effect on air columnar resonance can be exhibited. Further, since the protrusions 6 are uniformly dispersed in the groove width direction, it is possible to ensure a stone biting prevention effect. Furthermore, since the height of the projection 6 is relatively low and the non-projection portion 7 is continuous in the tire circumferential direction, the drainage performance of the circumferential groove 1 can be ensured. Therefore, tire noise can be effectively reduced while ensuring stone biting prevention performance and wet performance.

  In the above embodiment, the protrusions are provided for all of the plurality of circumferential grooves, but the present invention is not limited to the case where the protrusions are provided for all the circumferential grooves.

  A pneumatic tire having the tread pattern shown in FIG. 1 and a tire size: 11R22.5 14PR was produced (Example 1). The details of the circumferential groove and the protrusion arrangement configuration are as shown in Table 1 below (the tire contact length is 160 mm).

  In the tire of Example 1, the protrusion arrangement configuration was changed to that shown in FIG. Further, in the tire of Example 1, the protrusion arrangement configuration was changed to that shown in FIG. Further, in the tire of Example 1, the groove width was changed without providing the protrusions, and the tire of Comparative Example 2 was produced in the same manner as the others. In all the tires, the space volumes in the grooves were matched.

  About each obtained tire, the stone biting prevention performance, the wet performance, and the noise performance were measured. The measuring method is as follows.

-Stone biting prevention performance: Each tire was mounted on a large truck and traveled on an unpaved road surface to check for stone biting. The case where there was no stone bite was evaluated as “◯”, and the case where there was a stone bite was evaluated as “x”.

-Wet performance: Each tire was mounted on a large truck, and the wet braking performance was evaluated by measuring the slip distance when a wet road (ISO standard asphalt road surface with a water depth of 5 mm) entered at a speed of 40 km / h and braking suddenly. . The results are indicated by an index with Comparative Example 2 being 100, and the smaller the value, the better the wet performance.

-Noise performance: The noise level at a traveling speed of 60 km / h was measured by a table noise evaluation according to JASO C606, and the difference was obtained by using Comparative Example 2 as a control.

  The results are as shown in Table 1. With the tires of Example 1 and Example 2 according to the present invention, the noise can be greatly reduced without substantially impairing the wet performance. Biting prevention performance was also secured.

  The present invention can be effectively used to reduce tire noise in various pneumatic tires having a circumferential groove extending in the tire circumferential direction on the tread.

It is a partial development figure showing a tread pattern of a pneumatic tire concerning one embodiment of the present invention. It is a top view which shows the protrusion arrangement | positioning structure in the circumferential groove | channel of the tire of the embodiment. It is the III-III sectional view taken on the line of FIG. It is a figure for demonstrating the scanning method for calculating | requiring standard deviation (alpha) and (beta) in the protrusion arrangement | positioning structure of the embodiment, (a) shows the case where (alpha) is calculated | required and (b) shows the case where (beta) is calculated | required, respectively. (A) is a graph showing the area variation of the non-projection portion in the tire circumferential direction obtained by scanning in FIG. 4 (a), and (b) is a graph of the non-projection portion in the groove width direction obtained by scanning in FIG. 4 (b). It is a graph which shows an area fluctuation | variation. (A) And (b) is a top view which shows the protrusion arrangement structure which concerns on other embodiment. (A)-(c) is a top view which shows the protrusion arrangement structure which concerns on a comparative example. It is a graph which shows the relationship between (beta) / (alpha) and a radiated sound level.

Explanation of symbols

1 ... Circumferential groove 6 ... Protrusion 7 ... Non-protrusion part CL ... Center line in the width direction of the circumferential groove

Claims (4)

In a pneumatic tire having a circumferential groove composed of straight grooves extending in the tire circumferential direction on the tread,
A plurality of protrusions are arranged in the tire circumferential direction on the groove bottom of the circumferential groove, and the plurality of protrusions are arranged such that a non-projection portion on the groove bottom surface is continuous in the tire circumferential direction, and the circumferential groove In the circumferential groove, the protrusions arranged close to the left groove wall and the protrusions arranged close to the right groove wall Alternatingly arranged in the tire circumferential direction, and between adjacent protrusions, it has no overlapping part in the tire circumferential direction, and is arranged to have an overlapping part in the groove width direction ,
Further, in the plurality of protrusions, the standard deviation of the area change in the tire circumferential direction of the non-projection part is α, and the standard deviation of the area change in the groove width direction of the non-projection part is β (β / α ) Pneumatic tire characterized by being arranged to satisfy ≦ 15 . The pneumatic tire of claim 1, wherein a height from the groove bottom of the projections is 20 to 50% of the depth of the circumferential groove. 3. The pneumatic tire according to claim 1, wherein a ratio of an area of all projecting portions in the entire groove bottom surface is 20 to 30%. The protrusions claim 1-3, characterized in that both ends in the tire circumferential direction is parallel to the groove width direction, and a prismatic shape having a horizontal cross-section of hexagon having an apex angle on both sides of the groove width direction The pneumatic tire according to any one of the above.

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