Patent Publication Number: US-2022234390-A1

Title: Tire

Description:
TECHNICAL FIELD 
     The present invention relates to a tire. 
     Priority is claimed on Japanese Patent Application No. 2019-108372, filed on Jun. 11, 2019, the content of which is incorporated herein by reference. 
     BACKGROUND ART 
     In the related art, for example, as shown in Patent Document 1 below, a tire is known, in which a plurality of buffer recessed portions compression-deformable in a tire radial direction are arranged in a tire circumferential direction on an outer surface of a buttress portion connected to an end portion of the tread surface portion in a tire width direction over the entire area in the tire circumferential direction, and a valley line portion extending in the tire circumferential direction and a ridge line portion extending from the valley line portion in the tire circumferential direction are formed in a central portion of the buffer recessed portion in the tire radial direction. In this tire, when vibration is input from a road surface through the tread surface portion during traveling, the input vibration can be damped by deforming the buffer recessed portion in the tire radial direction. 
     CITATION LIST 
     Patent Document 
     [Patent Document 1] 
     Japanese Unexamined Patent Application, First Publication No. 2019-1277 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the tire of the related art, a buttress portion is repeatedly bent along a valley line portion and a ridge line portion due to input vibration from a road surface, and thus, an outer surface of the buttress portion may have cracks extending in the tire circumferential direction through a central portion of the buffer recessed portion in the tire radial direction. 
     The present invention is made in view of the above-mentioned circumstances, and an object thereof is to provide a tire capable of attenuating vibration input from the road surface through the tread surface portion during traveling, and preventing cracks extending in the tire circumferential direction from occurring on the outer surface of the buttress portion. 
     Solution to Problem 
     According to an aspect of the present invention, there is provided a tire including a plurality of buffer recessed portions compression-deformable in a tire radial direction that are arranged in a tire circumferential direction over an entire area in the tire circumferential direction on an outer surface of a buttress portion connected to an end portion of a tread surface portion in a tire width direction, in which in a plan view of the buttress portion, an opening peripheral edge of the buffer recessed portion has a hexagonal shape including six side portions, and the buffer recessed portions adjacent to each other in the tire circumferential direction are arranged such that one of the six side portions of one of the buffer recessed portions faces one of the six side portions of the other of the buffer recessed portions in the tire circumferential direction. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to attenuate vibration input from a road surface through a tread surface portion during traveling and prevent cracks extending in a tire circumferential direction from occurring on an outer surface of a buttress portion. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view of a tire according to an embodiment of the present invention along a tire width direction. 
         FIG. 2  is a developed view of a tread surface portion and a buttress portion of the tire shown in  FIG. 1 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a tire  1  according to an embodiment of the present invention will be described with reference to  FIGS. 1 and 2 . 
     The tire  1  includes a tread section  15  located at an outer end portion in a tire radial direction, a pair of sidewall portions  16  extending inward in the tire radial direction from both end portions of the tread section  15  in a tire width direction, a pair of buttress portions  12  that connects the tread section  15  and the sidewall portions  16  to each other, and a bead portion  17  connected to an inner end portion of the sidewall portion  16  in the tire radial direction. A bead core  17   a  is embedded in the bead portion  17 . A belt  18  is embedded in the tread section  15 . In the tread section  15 , an outer peripheral surface facing the outer side in the tire radial direction is a tread surface portion  11 . A carcass ply  19  is integrally embedded in the tread section  15 , the buttress portions  12 , the sidewall portions  16 , and the bead portions  17 . 
     The carcass ply  19  is folded around the bead core  17   a.    
     An explicit portion (not shown) is formed on the outer surface of the tire  1  such that a mounting direction of the tire  1  in the tire width direction with respect to the vehicle can be specified. This explicit portion is formed on the outer surface of, for example, the sidewall portion  16  of the tire  1 . 
     Here, the tread surface portion  11  refers to the ground contact surface of the tread section  15  in a state where a regular internal pressure and a regular load are applied to the tire  1 . The buttress portion  12  has an outer surface that is connected to an outer end portion of the tread surface portion  11  in the tire width direction, and does not come into contact with a smooth road surface when the tire  1  is rotated in a state where the regular internal pressure and regular load are applied to the tire  1 . 
     The regular internal pressure is an air pressure corresponding to a maximum load capacity in Year Book 2008 version of Japan Automobile Tire Association (JATMA), and the regular load is a load corresponding to a maximum load capacity when a single wheel of Year Book 2008 version of JATMA is applied. In countries other than Japan, the regular internal pressure is an air pressure corresponding to a maximum load (maximum load capacity) of a single wheel described in a standard described later, and the regular load is a maximum load (maximum load capacity) of a single wheel in an applicable size described in the standard described later. The standards are set by industrial standards that are valid in an area where the tire is produced or used. For example, in the United States, the standard is “The Tire and Rim Association Inc.&#39;s Year Book”, and in Europe, the standard is “The European Tire and Rim Technical Organization&#39;s Standards Manual”. 
     Outer main grooves  21  and  22 , inner main grooves  23  and  24 , an outer resonator  25 , and an inner resonator  26  are formed on the tread surface portion  11 . 
     In  FIG. 2 , two-dot chain lines extending in the tire circumferential direction indicates an outer end edge of the tread surface portion  11  in the tire width direction. 
     The outer main grooves  21  and  22  extend continuously in the tire circumferential direction. Two outer main grooves  21  and  22  are formed in an outer tread surface portion  11  a of the tread surface portion  11  located on an outer side of the vehicle along the tire width direction with respect to a tire equatorial portion CL at intervals in the tire width direction. 
     The inner main grooves  23  and  24  extend continuously in the tire circumferential direction. Two inner main grooves  23  and  24  are formed in an inner tread surface portion  11   b  of the tread surface portion  11  located on inner side of the vehicle along the tire width direction with respect to the tire equatorial portion CL at intervals in the tire width direction. 
     A central land portion  27  extends continuously in the tire circumferential direction, which is partitioned by the outer main groove  22  of the two outer main grooves  21  and  22  located on the inner side in the tire width direction, and the inner main groove  24  of the two inner main grooves  23  and  24  located on the inner side in the tire width direction. A central portion of the central land portion  27  in the tire width direction is located on the tire equatorial portion CL. 
     A plurality of the outer resonators  25  and a plurality of the inner resonators  26  are each formed in the tire circumferential direction on an outer land portion  28  partitioned by the two outer main grooves  21  and  22  and an inner land portion  29  partitioned by the two inner main grooves  23  and  24 . 
     The outer resonator  25  includes a first vertical groove  31  which extends in the tire circumferential direction, and a first branch groove  32  and a second branch groove  33  which have an inner volume smaller than that of the first vertical groove  31 , extend in the tire width direction in directions opposite to each other from both end portions of the first vertical groove  31  in the tire circumferential direction, and are each opened to the two outer main grooves  21  and  22 . 
     The inner resonator  26  includes a second vertical groove  36  which extends in the tire circumferential direction, and a third branch groove  37  and a fourth branch groove  38  which have an inner volume smaller than that of the second vertical groove  36 , extends in the tire width direction in directions opposite to each other from both end portions of the second vertical groove  36  in the tire circumferential direction, and are each opened to the two inner main grooves  23  and  24 . 
     The outer resonators  25  and the inner resonators  26  are formed on the tread surface portion  11 . Accordingly, during traveling, a portion of air flowing between the outer main grooves  21  and  22  and the inner main grooves  23  and  24  and the road surface is introduced into the first vertical groove  31  and the second vertical groove  36  through the first branch groove  32  or the second branch groove  33  and the third branch groove  37  or the fourth branch groove  38 . 
     As a result, it possible to attenuate vibration of the air flowing between the outer main grooves  21  and  22  and the inner main grooves  23  and  24  and the road surface, and it is possible to suppress occurrence of air column resonance. 
     Further, in the present embodiment, a plurality of buffer recessed portions  40  compression-deformable in the tire radial direction are arranged on an outer surface of the buttress portion  12  along the tire circumferential direction over the entire area in the tire circumferential direction. 
     The buffer recessed portion  40  is provided in the buttress portion  12  on the inner side of the vehicle in the pair of buttress portions  12 . The buffer recessed portion  40  may be provided in the buttress portion  12  on the outer side of the vehicle in the pair of buttress portions  12 , or may be provided in both of the pair of buttress portions  12 . 
     In a plan view of the buttress portion  12 , an opening peripheral edge of the buffer recessed portion  40  has a hexagonal shape including two first side portions (opposite side portions)  41 , four second side portions  42 , two first corner portions  43 , and four second corner portions  44 . 
     Hereinafter, a centroid of this hexagonal shape is referred to as a center O of the buffer recessed portion  40 . 
     The first side portions  41  are located at both ends of the buffer recessed portion  40  in the tire circumferential direction and extend in the tire radial direction. The buffer recessed portions  40  adjacent to each other in the tire circumferential direction are arranged such that the first side portions  41  thereof face each other in the tire circumferential direction. 
     The second side portion  42  is longer than the first side portion  41 . As a result, in a plan view of the buttress portion  12 , in the two first side portions  41  and the four second side portions  42  included in the opening peripheral edge of the buffer recessed portion  40 , a length of the first side portion  41  facing another buffer recessed portion  40  in the tire circumferential direction is shorter than a length of the second side portion  42 . 
     The second side portions  42  extend from both ends of the first side portion  41  in a direction in which the second side portions are separated from each other in the tire radial direction toward the central portion of the buffer recessed portion  40  in the tire circumferential direction. A size of the buffer recessed portion  40  in the tire radial direction increases from both end portions in the tire circumferential direction toward the central portion in the tire circumferential direction. The buffer recessed portion  40  is formed in a horizontally long shape in which the size in the tire circumferential direction is larger than the size in the tire radial direction. In the four second side portions  42 , in a plan view of the buttress portion  12 , the pair of second side portions  42  facing each other across the center O of the buffer recessed portion  40  in a direction inclined with respect to both directions in the tire radial direction and the tire circumferential direction is parallel to each other. 
     The first corner portion  43  is defined by two second side portions  42  connected around the center O of the buffer recessed portion  40 , and is located at the central portion of the buffer recessed portion  40  in the tire circumferential direction. The second corner portion  44  is defined by the first side portion  41  and the second side portion  42  which are continuous around the center O of the buffer recessed portion  40 , and an angle of the second corner portion  44  is smaller than that of the first corner portion  43 . 
     From the above, in a plan view of the buttress portion  12 , the buffer recessed portion  40  has a hexagonal shape including the first side portions  41  extending in the tire radial direction at both end portions in the tire circumferential direction and the first corner portions  43  which point outward in the tire radial direction at the central portion in the tire circumferential direction. 
     In a plan view of the buttress portion  12 , a gap in the tire circumferential direction between the buffer recessed portions  40  adjacent to each other in the tire circumferential direction is smaller than a minimum value of a distance between the center O of the buffer recessed portion  40  and the opening peripheral edge of the buffer recessed portion  40 . In the shown example, in the opening peripheral edge of the buffer recessed portion  40 , a portion where a distance from the center O of the buffer recessed portion  40  is the smallest in a plan view is the first corner portion  43 . 
     In a plan view of the buttress portion  12 , the buffer recessed portion  40  has a symmetrical shape with respect to both of a first reference line L 1  which passes through the central portion of the buffer recessed portion  40  in the tire circumferential direction and extends in the tire radial direction and a second reference line L 2  which passes through the central portion of the buffer recessed portion  40  in the tire radial direction and extends in the tire circumferential direction. The first reference line L 1  and the second reference line L 2  intersect at the center O of the buffer recessed portion  40 . 
     In a plan view of the buttress portion  12 , the buffer recessed portion  40  may have a symmetrical shape with respect to any one of the first reference line L 1  and the second reference line L 2  or the buffer recessed portion  40  may have an unsymmetrical shape with respect to both of the first reference line L 1  and the second reference line L 2 . 
     An inner surface of the buffer recessed portion  40  includes a bottom surface  45  facing in the tire width direction, and a side surface  46  which rises from an outer peripheral edge of the bottom surface  45  and is connected to the opening peripheral edge of the buffer recessed portion  40 . In a plan view of the buttress portion  12 , the bottom surface  45  and the side surface  46  are arranged coaxially with the center O of the buffer recessed portion  40 . 
     The buffer recessed portion  40  may be formed in a cone shape having no bottom surface  45 , or the centers of the bottom surface  45  and the side surface  46  may be displaced from the center O of the buffer recessed portion  40  in a plan view of the buttress portion  12 . 
     In a plan view of the buttress portion  12 , a distance a 1  between the first side portion  41  of the opening peripheral edge of the buffer recessed portion  40  and the outer peripheral edge of the bottom surface  45  in the tire circumferential direction is larger than a distance a 2  between the center O of the buffer recessed portion  40  and the outer peripheral edge of the bottom surface  45  in the tire circumferential direction. The distance a 1  may be set to the distance a 2  or less. 
     In a plan view of the buttress portion  12 , a distance b 1  between the first corner portion  43  of the opening peripheral edge of the buffer recessed portion  40  and the outer peripheral edge of the bottom surface  45  in the tire radial direction is larger than a distance b 2  between the center O of the buffer recessed portion  40  and the outer peripheral edge of the bottom surface  45  in the tire radial direction. The distance b 1  may be set to the distance b 2  or less. 
     In a plan view of the buttress portion  12 , the distance al between the first side portion  41  and the outer peripheral edge of the bottom surface  45  in the tire circumferential direction is larger than the distance b 1  between the first corner portion  43  and the outer peripheral edge of the bottom surface  45  in the tire radial direction. The distance a 1  may be set to the distance b 1  or less. 
     In a plan view of the buttress portion  12 , the bottom surface  45  of the buffer recessed portion  40  has a hexagonal shape arranged in the same direction as the opening peripheral edge of the buffer recessed portion  40 . The side surface  46  of the buffer recessed portion  40  includes six partitioned surfaces  46   b  connected via valley line portions  46   a  around the center O of the buffer recessed portion  40  in a plan view of the buttress portion  12 . Each valley line portion  46   a  connects the first corner portion  43  or the second corner portion  44  facing each other in a plan view of the buttress portion  12  to one corner portion forming the outer peripheral edge of the bottom surface  45 . The partitioned surface  46   b  connects the first side portion  41  or the second side portion  42  to one line portion forming the outer peripheral edge of the bottom surface  45 . 
     From the above, the buffer recessed portion  40  has a hexagonal frustum shape. 
     Three or more buffer recessed portion rows A each formed of the plurality of buffer recessed portions  40  arranged along the tire circumferential direction are formed on the outer surface of the buttress portion  12 . In the shown example, three buffer recessed portion rows A are formed on the outer surface of the buttress portion  12 . In addition, less than three buffer recessed portion rows A may be formed on the outer surface of the buttress portion  12 . 
     In one buffer recessed portion row A, the center O of each buffer recessed portion  40  is located at the same position in the tire radial direction. 
     The buffer recessed portion rows A adjacent to each other in the tire radial direction are arranged so as to be offset in the tire circumferential direction by less than a size of the buffer recessed portion  40  in the tire circumferential direction. In the shown example, the buffer recessed portion rows A adjacent to each other in the tire radial direction are arranged so as to be offset in the tire circumferential direction by half the size of the buffer recessed portion  40  in the tire circumferential direction. 
     The buffer recessed portion rows A adjacent to each other in the tire radial direction are arranged so as to be offset in the tire radial direction by less than a size of the buffer recessed portion  40  in the tire radial direction. In the shown example, the buffer recessed portion rows A adjacent to each other in the tire radial direction are arranged so as to be offset by more than half the size of the buffer recessed portion  40  in the tire radial direction. 
     Moreover, in the buffer recessed portion rows A adjacent to each other in the tire radial direction, an inner end portion of the buffer recessed portion  40  in the tire radial direction located on the outer side in the tire radial direction is located on the inner side in the tire radial direction from an outer end portion in the tire radial direction of the buffer recessed portion  40  located on the inner side in the tire radial direction. That is, in the buffer recessed portion rows A adjacent to each other in the tire radial direction, the first corner portion  43  of the buffer recessed portion  40  of one buffer recessed portion row A is arranged so as to bite into the tire radial direction and mesh with each other in the tire circumferential direction with respect to a band-shaped arrangement region of the other buffer recessed portion row A that extends continuously over the entire area in the tire circumferential direction. 
     The buffer recessed portions  40  adjacent to each other in the tire radial direction are arranged such that one of the second side portions  42  of the buffer recessed portions  40  faces parallel to each other. A gap between the second side portions  42  is equivalent to the gap between the buffer recessed portions  40  in the tire circumferential direction adjacent to each other in the tire circumferential direction. 
     When the size of the buffer recessed portion row A in the tire radial direction is represented by H, the size of the buffer recessed portion row A in the tire circumferential direction at the central portion in the tire radial direction is represented by S, an opening area of the buffer recessed portion  40  is represented by X, a total inner volume of the plurality of buffer recessed portions  40  is represented by V, a depth of the buffer recessed portion  40  is represented by D, and the number of buffer recessed portions  40  is represented by N, 0.4≤X/(H·S)≤1.3, 150≤(N·X)/(H·S)≤600, and H·S·D/2≤V are satisfied. 
     As described above, according to the tire  1  of the present embodiment, since the plurality of buffer recessed portions  40  are formed on the outer surface of the buttress portion  12 , when vibration is input from the road surface through the tread surface portion  11  during traveling, it is possible to attenuate the input vibration by deforming the buffer recessed portions  40  in the tire radial direction. 
     In particular, in a plan view of the buttress portion  12 , the opening peripheral edge of the buffer recessed portion  40  has a hexagonal shape, and the buffer recessed portions  40  adjacent to each other in the tire circumferential direction are arranged such that the first side portions  41  thereof face each other in the tire circumferential direction. As a result, in a plan view, the first side portion  41 , the second side portion  42 , and the hexagonal diagonal lines formed by the side portions  41  and  42  do not coincide with a line extending along the tire circumferential direction. Accordingly, it is possible to make it difficult for the buffer recessed portion  40  to have a line portion that coincides with the line extending in the tire circumferential direction, that is, a folding line portion that is repeatedly bent by the input vibration from the road surface, and it is possible to suppress formation of cracks extending in the tire circumferential direction in the buffer recessed portion row A. 
     Since the buffer recessed portion  40  is formed in a horizontally long shape, the buffer recessed portion  40  can be easily deformed in the tire radial direction at the time of vibration input. 
     In a plan view of the buttress portion  12 , in the two first side portions  41  and the four second side portions  42  included in the opening peripheral edge of the buffer recessed portion  40 , the length of the first side portion  41  facing another buffer recessed portion  40  in the tire circumferential direction is shorter than the length of the second side portion  42 . Accordingly, the buffer recessed portion  40  can be easily deformed in the tire radial direction at the time of vibration input. 
     In a plan view of the buttress portion  12 , the distance a 1  between the first side portion  41  of the opening peripheral edge of the buffer recessed portion  40  and the outer peripheral edge of the bottom surface  45  in the tire circumferential direction is larger than the distance a 2  between the center O of the buffer recessed portion  40  and the outer peripheral edge of the bottom surface  45  in the tire circumferential direction. Accordingly, the portions of the side surface  46  located on both sides sandwiching the bottom surface  45  in the tire circumferential direction can be easily deformed at the time of vibration input. 
     In a plan view of the buttress portion  12 , the distance b 1  between the first corner portion  43  of the opening peripheral edge of the buffer recessed portion  40  and the outer peripheral edge of the bottom surface  45  in the tire radial direction is larger than the distance b 2  between the center O of the buffer recessed portion  40  and the outer peripheral edge of the bottom surface  45  in the tire radial direction. Accordingly, the portions of the side surface  46  located on both sides sandwiching the bottom surface  45  in the tire radial direction are likely to be deformed in the tire radial direction around the outer peripheral edge of the bottom surface  45 , and the buffer recessed portion  40  can be easily deformed in the tire radial direction at the time of vibration input. 
     In a plan view of the buttress portion  12 , the gap in the tire circumferential direction between the buffer recessed portions  40  adjacent to each other in the tire circumferential direction is smaller than the minimum value of the distance between the center O of the buffer recessed portion  40  and the opening peripheral edge of the buffer recessed portion  40 . Accordingly, it is possible to prevent the distance between the buffer recessed portions  40  adjacent to each other in the tire circumferential direction from becoming long, and it is possible to reliably attenuate the input vibration. 
     Since three or more buffer recessed portion rows A are formed on the outer surface of the buttress portion  12 , vibration input from the road surface via the tread surface portion  11  can be reliably attenuated during traveling. 
     In a plan view of the buttress portion  12 , the buffer recessed portion  40  having a hexagonal shape exhibits a symmetrical shape with respect to both the first reference line L 1  and the second reference line L 2 . Accordingly, from the buffer recessed portion  40 , it is possible to remove the line portion that coincides with the line extending in the tire circumferential direction, including the diagonal line, and reliably suppresses occurrence of cracks extending in the tire circumferential direction in the buffer recessed portion row A. 
     In a plan view of the buttress portion  12 , the buffer recessed portion  40  has the above-mentioned symmetrical shape. Accordingly, it is possible to stabilize a shape when the buffer recessed portion  40  is deformed in the tire radial direction at the time of vibration input and stably exhibit damping performance. 
     A technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from a scope of the present invention defined in the claims. 
     The buffer recessed portion  40  may be formed in a vertically long shape in which the size in the tire circumferential direction is shorter than the size in the tire radial direction, and the size of the buffer recessed portion  40  in the tire circumferential direction may be equal to the size of the buffer recessed portion  40  in the tire radial direction. 
     In the above embodiment, in a plan view of the buttress portion  12 , the buffer recessed portion  40  has a hexagonal shape in which the bottom surface  45  of the buffer recessed portion  40  is arranged in the same orientation as the opening peripheral edge of the buffer recessed portion  40 . However, the bottom surface  45  of the buffer recessed portion  40  may be arranged in a different orientation as the opening peripheral edge of the buffer recessed portion  40  and the shape of the bottom surface  45  in a plan view may be different from the shape of the opening peripheral edge of the buffer recessed portion  40  in a plan view. 
     In the above embodiment, the side surface  46  of the buffer recessed portion  40  is configured to include the valley line portion  46   a  and the partitioned surface  46   b.  However, for example, the side surface  46  may be configured to have a smooth peripheral surface that continuously extends around the center O of the buffer recessed portion  40 . 
     The tread pattern formed on the tread surface portion  11  is not limited to the above embodiment, and may be appropriately changed. 
     In addition, it is possible to replace the components in the above-described embodiment with well-known components as appropriate without departing from the scope of the present invention defined in the claims, and the above-described embodiments and modifications may be appropriately combined. 
     In the present invention, since the plurality of buffer recessed portions are formed on the outer surface of the buttress portion, when vibration is input from the road surface through the tread surface portion during traveling, it is possible to attenuate the input vibration by deforming the buffer recessed portions in the tire radial direction. 
     In particular, in a plan view of the buttress portion, the opening peripheral edge of the buffer recessed portion has a hexagonal shape including six side portions, and the buffer recessed portions adjacent to each other in the tire circumferential direction are arranged such that one of the six side portions of one of the buffer recessed portions faces one of the six side portions of the other of the buffer recessed portions in the tire circumferential direction. As a result, in a plan view, the six side portions and the hexagonal diagonal line formed by the side portions do not coincide with the line extending along the tire circumferential direction. Accordingly, it is possible to make it difficult for the buffer recessed portion to have a line portion that coincides with the line extending in the tire circumferential direction, that is, a folding line portion that is repeatedly bent by the input vibration from the road surface, and it is possible to suppress formation of cracks extending in the tire circumferential direction in the buffer recessed portion row each formed of the plurality of buffer recessed portions arranged in the tire circumferential direction. 
     Here, the buffer recessed portion may be formed in a horizontally long shape in which the size in the tire circumferential direction is larger than the size in the tire radial direction. 
     In this case, since the buffer recessed portion is formed in a horizontally long shape, the buffer recessed portion can be easily deformed in the tire radial direction at the time of vibration input. 
     Further, in the six side portions, the length of the facing side portion facing the other buffer recessed portion in the tire circumferential direction may be shorter than the lengths of other side portions. 
     In this case, in the six side portions, since the length of the facing side portion facing the other buffer recessed portion in the tire circumferential direction is shorter than the lengths of other side portions, the buffer recessed portion can be easily deformed in the tire radial direction at the time of vibration input. 
     Further, the inner surface of the buffer recessed portion may include the bottom surface facing in the tire width direction, and the side surface which rises from an outer peripheral edge of the bottom surface and is connected to the opening peripheral edge of the buffer recessed portion, and in a plan view of the buttress portion, the distance between the opening peripheral edge of the buffer recessed portion and the outer peripheral edge of the bottom surface in the tire circumferential direction may be larger than the distance between the center of the bottom surface and the outer peripheral edge of the bottom surface in the tire circumferential direction. 
     In this case, in a plan view of the buttress portion, the distance between the opening peripheral edge of the buffer recessed portion and the outer peripheral edge of the bottom surface in the tire circumferential direction may be larger than the distance between the center of the bottom surface and the outer peripheral edge of the bottom surface in the tire circumferential direction. Accordingly, the portions of the side surface located on both sides sandwiching the bottom surface in the tire circumferential direction can be easily deformed at the time of vibration input. 
     Further, the inner surface of the buffer recessed portion may include the bottom surface facing in the tire width direction, and the side surface which rises from the outer peripheral edge of the bottom surface and is connected to the opening peripheral edge of the buffer recessed portion, and in a plan view of the buttress portion, the distance between the opening peripheral edge of the buffer recessed portion and the outer peripheral edge of the bottom surface in the tire radial direction may be larger than the distance between the center of the bottom surface and the outer peripheral edge of the bottom surface in the tire radial direction. 
     In this case, in a plan view of the buttress portion, the distance between the opening peripheral edge of the buffer recessed portion and the outer peripheral edge of the bottom surface in the tire radial direction may be larger than the distance between the center of the bottom surface and the outer peripheral edge of the bottom surface in the tire radial direction. Accordingly, the portions of the side surface located on both sides sandwiching the bottom surface in the tire radial direction are likely to be deformed in the tire radial direction around the outer peripheral edge of the bottom surface, and the buffer recessed portion can be easily deformed in the tire radial direction at the time of vibration input. 
     Further, in a plan view of the buttress portion, the gap in the tire circumferential direction between the buffer recessed portions adjacent to each other in the tire circumferential direction may be smaller than the minimum value of the distance between the center of the buffer recessed portion and the opening peripheral edge of the buffer recessed portion. 
     In this case, in a plan view of the buttress portion, the gap in the tire circumferential direction between the buffer recessed portions adjacent to each other in the tire circumferential direction may be smaller than the minimum value of the distance between the center of the buffer recessed portion and the opening peripheral edge of the buffer recessed portion. Accordingly, it is possible to prevent the distance between the buffer recessed portions adjacent to each other in the tire circumferential direction from becoming long, and it is possible to reliably attenuate the input vibration. 
     Further, three or more buffer recessed portion rows each formed of the plurality of buffer recessed portions arranged along the tire circumferential direction may be formed on the outer surface of the buttress portion. 
     In this case, since three or more buffer recessed portion rows are formed on the outer surface of the buttress portion, the vibration input from the road surface through the tread surface portion can be reliably attenuated during traveling. 
     Further, in a plan view of the buttress portion, the buffer recessed portion may have a symmetrical shape with respect to both of the first reference line which passes through the central portion of the buffer recessed portion in the tire circumferential direction and extends in the tire radial direction and the second reference line which passes through the central portion of the buffer recessed portion in the tire radial direction and extends in the tire circumferential direction. 
     In this case, in a plan view of the buttress portion, the buffer recessed portion having a hexagonal shape exhibits a symmetrical shape with respect to both the first reference line and the second reference line. Accordingly, from the buffer recessed portion, it is possible to remove the line portion that coincides with the line extending in the tire circumferential direction, including the diagonal line, and reliably suppresses occurrence of cracks extending in the tire circumferential direction in the buffer recessed portion row. 
     In a plan view of the buttress portion, the buffer recessed portion has the above-mentioned symmetrical shape. Accordingly, it is possible to stabilize a shape when the buffer recessed portion is deformed in the tire radial direction at the time of vibration input and stably exhibit damping performance. 
     INDUSTRIAL APPLICABILITY 
     By applying a tire of the present invention to a relevant field, it is possible to attenuate vibration input from a road surface through a tread surface portion during traveling and prevent cracks extending in a tire circumferential direction from occurring on an outer surface of a buttress portion. 
     REFERENCE SIGNS LIST 
       1 : Tire 
       11 : tread surface portion 
       12 : Buttress portion 
       40 : Buffer recessed portion 
       41 : First side portion (opposite side portion) 
       42 : Second side portion (another side portion) 
       45 : Bottom surface 
       46 : Side surface 
     A: Buffer recessed portion row 
     L 1  : First reference line 
     L 2 : Second reference line 
     O: Center of buffer recessed portion (center of bottom surface)