Patent Publication Number: US-2020298626-A1

Title: Pneumatic tire

Description:
TECHNICAL FIELD 
     The present disclosure relates to a pneumatic tire. 
     BACKGROUND 
     In a pneumatic tire, it is required to reduce noise during vehicle running and improve quietness. To meet the requirement, various tires have been suggested in which vehicle exterior noise such as air column resonance sound (often observed in a range from about 800 to 1200 Hz in a passenger vehicle) generated from a circumferential main groove provided in a tread surface of a tire is reduced by a resonator (so-called Helmholtz resonator) comprising an air chamber portion and a narrowed neck portion (e.g., Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Patent Laid-Open No. 2015-171835 
     SUMMARY 
     Technical Problem 
     However, in general, Helmholtz resonator is provided in a land portion of a tread, a rigidity distribution of the land portion tends to be nonuniform, and uneven wear easily occurs in the tread. Consequently, it is desired that the uneven wear of the tread is suppressed while reducing air column resonance sound. 
     To solve such a problem, an object of the present disclosure is to provide a tire in which uneven wear in a tread can be suppressed while reducing air column resonance sound. 
     Solution to Problem 
     A tire of the present disclosure is a tire including, in a tread surface, a plurality of land portions partitioned by a circumferential main groove extending continuously in a tire circumferential direction on at least one side in a tire width direction, and comprising, in one of the land portions, a resonator including an auxiliary groove that terminates in the land portion, and at least one branch groove that communicates between the auxiliary groove and the circumferential main groove, wherein a hidden groove having an opening width in the tread surface that is smaller than a groove width of a groove bottom is provided in at least a part of the auxiliary groove. 
     Here, in the present description, “the tread surface” means an outer circumferential surface over an entire circumference of the tire, which comes in contact with a road surface when the tire assembled to a rim and filled with a predetermined internal pressure is rolled in a state of being loaded with a maximum load, and “a tread ground contact edge” means an edge of the tread surface in the tire width direction. 
     Furthermore, in the present description, “the opening width”, “the groove width” or the like refers to a width measured along a direction orthogonal to an extending direction of the groove in the following reference state. Hereinafter, it is considered that dimensions or the like of respective elements of the grooves or the like are measured in the reference state, unless otherwise mentioned. 
     Furthermore, in the present description, “the reference state” indicates a state where the tire is assembled to the rim, filled with the internal pressure and unloaded. 
     Note that the above “rim” indicates an approved rim (a measuring rim in Standards Manual of ETRTO, and a design rim in Year Book of TRA) in an applicable size described or to be described in future in an industrial standard effective in a district where the tire is produced and used, for example, JATMA Year Book of JATMA (the Japan Automobile Tyre Manufacturers Association) in Japan, Standards Manual of ETRTO (the European Tyre and Rim Technical Organization) in Europe, Year Book of TRA (the Tire and Rim Association, Inc.) in U.S. or the like (that is, the above “rim” also includes a size that can be included in the above industrial standard in future, in addition to the existing size. Examples of “the size to be described in future” include sizes described as “future developments” in 2013 edition of Standards Manual of ETRTO). However, it is considered that a rim having a size that is not described in the above industrial standard is a rim having a width corresponding to a bead width of the tire. Furthermore, “a predetermined internal pressure” refers to an air pressure (a maximum air pressure) corresponding to a maximum load capability of a single wheel in an applicable size and ply rating described in Year Book of JATMA described above, or the like. “The predetermined internal pressure” having a size that is not described in the above industrial standard refers to an air pressure (the maximum air pressure) corresponding to the maximum load capability prescribed for each vehicle to which the tire is mounted. Additionally, “the maximum load” refers to a load corresponding to the above maximum load capability. Note that air described herein can be replaced with an inert gas such as a nitrogen gas, or the like. 
     Note that in the present description, “at least a central portion of the auxiliary groove in an extending direction” described above refers to a portion of the auxiliary groove excluding an end portion thereof. 
     Note that in the present disclosure, “an extending length” described above refers to a length of a straight line or a curve drawn in an opening center of the auxiliary groove. 
     Advantageous Effect 
     According to the present disclosure, uneven wear in a tread can be suppressed while reducing air column resonance sound. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a partial developed view of a tread surface of a tire according to an embodiment of the present disclosure; 
         FIG. 2  is a partial enlarged view of the tread surface illustrated in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view along the a-a line illustrated in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view along the b-b line illustrated in  FIG. 2 ; 
         FIG. 5  is a cross-sectional view along the c-c line illustrated in FIG.  2 ; and 
         FIG. 6  is a cross-sectional view along the d-d line illustrated in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of a tire according to the present disclosure will be illustrated and described with reference to the drawings. 
       FIG. 1  is a partial developed view illustrating a tread surface  2  of a tire  1  according to the embodiment of the present disclosure. Although partially omitted from the drawing, the tire  1  of this embodiment comprises a carcass including a radial structure toroidally extending between bead portions, a belt disposed outside the carcass of a tread portion in a tire radial direction, and a tread rubber disposed outside the belt in the tire radial direction to form the tread surface  2 . 
     The tire  1  includes, in the tread surface  2 , a plurality of (in the present embodiment, five) land portions  4  partitioned by (in the present embodiment, four) circumferential main grooves  3  continuously extending in a tire circumferential direction on at least one side in a tire width direction, as illustrated in  FIG. 1 . More specifically, the tread surface  2  is formed with a central land portion  41  partitioned by two circumferential main grooves  31   a ,  31   b  adjacent to each other via a tire equator plane CL, an intermediate land portion  42   a  partitioned by two circumferential main grooves  31   a ,  32   a  extending in a tire half portion HA on one side of the tire equator plane CL (in  FIG. 1 , a paper surface left side), a shoulder land portion  43   a  partitioned by a ground contact edge TE of the tire half portion HA and the circumferential main groove  32   a  on a ground contact edge TE side, an intermediate land portion  42   b  partitioned by two circumferential main grooves  31   b ,  32   b  extending in a tire half portion HB on the other side of the tire equator plane CL (in  FIG. 1 , a paper surface right side), and a shoulder land portion  43   b  partitioned by a ground contact edge TE of the tire half portion HB and the circumferential main groove  32   b  on a ground contact edge TE side. 
     Note that each of the circumferential main grooves  31   a ,  31   b ,  32   a  and  32   b  in the tire  1  continuously extends linearly along the tire circumferential direction, but in another example, the circumferential main grooves  3  may have a zigzag-shaped or wavy-shaped extending form. Furthermore, each of the land portions  41 ,  42   a ,  42   b ,  43   a  and  43   b  in this example is a rib-shaped land portion extending continuously in the tire circumferential direction, but in another example, the land portions  4  may be block land portions or the like. 
     In the tire  1 , the land portion  4  is formed with a resonator (in an illustrated example, Helmholtz resonator)  5  including an auxiliary groove  51  that terminates in the land portion  4 , and at least one branch groove  52  (in the present embodiment, two branch grooves) that communicates between the auxiliary groove  51  and the circumferential main groove  3 . 
     More specifically, the resonator  5  of the present embodiment includes the auxiliary groove  51  formed in the intermediate land portion  42   a  of the tire half portion HA on one side, and includes the auxiliary groove  51  that terminates in the intermediate land portion  42   a , a first branch groove  52   a  that communicates between the auxiliary groove  51  and the circumferential main groove  32   a  on the tire ground contact edge TE side, and a second branch groove  52   b  that communicates between the auxiliary groove  51  and the circumferential main groove  31   a  on the tire equator plane CL side. Alternatively, the tire of the present disclosure may include a configuration where the resonator only includes one of the first branch groove or the second branch groove. That is, the resonator may be configured to communicate only with the circumferential main groove that partitions the land portion on one side in the tire width direction. Furthermore, the tire of the present disclosure may include a configuration where the resonator includes three, four or more branch grooves. 
     In the resonator  5 , the auxiliary groove  51  extends in the tire circumferential direction. That is, the auxiliary groove  51  has a shape having a length in the tire circumferential direction that is larger than a length in the tire width direction. 
     Furthermore, in the resonator  5 , the first branch groove  52   a  is provided adjacent to an end portion  51 Ea of the auxiliary groove  51  on one side (in  FIG. 1 , a paper surface upper side) in the tire circumferential direction, and the second branch groove  52   b  is provided adjacent to an end portion  51 Eb of the auxiliary groove  51  on the other side (in  FIG. 1 , a paper surface lower side) in the tire circumferential direction. That is, in this example, one end of the first branch groove  52   a  is opened in the circumferential main groove  32   a  on the ground contact edge TE side of the tire half portion HA, and the other end of the first branch groove  52   a  is opened in the end portion  51 Ea of the auxiliary groove  51  on one side in the tire circumferential direction. Furthermore, similarly, one end of the second branch groove  52   b  is opened in the circumferential main groove  31   a  on the tire equator plane CL side of the tire half portion HA, and the other end of the second branch groove  52   b  is opened in the end portion  51 Eb of the auxiliary groove  51  on the other side in the tire circumferential direction. Alternatively, in the tire of the present disclosure, the branch groove  52  may be provided in a portion other than a tire circumferential end portion of the auxiliary groove  51 , for example, adjacent to a central portion of the auxiliary groove  1  in the tire circumferential direction. 
     Additionally, in the resonator  5 , a groove volume of the auxiliary groove  51  is larger than a groove volume of each of the first branch groove  52   a  and the second branch groove  52   b  connected to the auxiliary groove  51 . Furthermore, an opening area of the auxiliary groove  51  to the tread surface  2  is larger than an opening area of each of the first branch groove  52   a  and the second branch groove  52   b , connected to the auxiliary groove  51 , to the tread surface  2 . 
     In addition,  FIG. 2  is a partial enlarged view of the tread surface  2  illustrated in  FIG. 1 , and illustrates the resonator  5  and a peripheral part of the resonator  5  in an enlarged manner. In the resonator  5 , a hidden groove  51 H having an opening width in the tread surface  2  that is smaller than a groove width of a groove bottom is provided in at least a part of the auxiliary groove  51 . The drawing illustrates a groove wall of the hidden groove  51 H with a broken line. In this embodiment, the hidden groove  51 H is provided only in the end portion  51 Ea of the auxiliary groove  51  on one side in the tire circumferential direction. The hidden groove  51 H extends along an extending direction of the auxiliary groove  51  from the end portion  51 Ea of the auxiliary groove  51  on the one side in the tire circumferential direction to a portion having a predetermined ratio to an extending length of the auxiliary groove  51 . 
     In this way, the auxiliary groove  51  in the tire  1  of the present embodiment comprises the hidden groove  51 H, and a revealed groove  51 G excluding the hidden groove  51 H. 
     Alternatively, in the tire of the present disclosure, the hidden groove may be provided in the whole auxiliary groove. That is, the auxiliary groove may only comprise the hidden groove. Furthermore, in the tire of the present disclosure, the hidden grooves may be provided in end portions of the auxiliary groove on both sides in the tire circumferential direction. Hereinafter, description will be made in detail as to the hidden groove  51 H and the revealed groove  51 G of the auxiliary groove  51  in the tire  1  of the present embodiment. 
       FIGS. 3 to 5  are cross-sectional views of the auxiliary groove  51 . That is,  FIG. 3  is a cross-sectional view along the a-a line of  FIG. 2 ,  FIG. 4  is a cross-sectional view along the b-b line of  FIG. 2 , and  FIG. 5  is a cross-sectional view along the c-c line of  FIG. 2 . More specifically,  FIG. 2  is a cross-sectional view of a plane of the revealed groove  51 G of the auxiliary groove  51  that is orthogonal to the extending direction of the auxiliary groove  51 , and  FIGS. 4, 5  are cross-sectional views of a plane of the hidden groove  51 H of the auxiliary groove  51  that is orthogonal to the extending direction of the auxiliary groove  51 . 
     As illustrated in  FIG. 3 , in the revealed groove  51 G of the auxiliary groove  51 , an opening width W 51  in the tread surface  2  is smaller than a groove depth D 51 , and larger than or equal to a groove width W 51 B in a groove bottom  51 B. 
     Furthermore, as illustrated in  FIGS. 4, 5 , in the hidden groove  51 H of the auxiliary groove  51 , an opening width W 51 H in the tread surface  2  is smaller than a groove depth D 51 H, and smaller than a groove width W 51 HB in a groove bottom  51 HB. 
     Additionally, the opening width W 51 H of the hidden groove  51 H in the tread surface  2  is smaller than the opening width W 51  of the revealed groove  51 G in the tread surface  2 . In addition, the groove depth D 51 H of the hidden groove  51 H is smaller on a revealed groove  51 G side than on a first branch groove  52   a  side. 
     Note that the hidden groove  51 H in the resonator  5  comprises an opening side portion  51 Ha having a groove width maintained on an inner side in the tire radial direction (a groove depth direction) in the same manner as in the opening width W 51 H in the tread surface  2 , and a groove bottom side portion  51 Hb having a groove width that is larger than the opening width W 51 H and continuous in the groove depth direction, in order from a tread surface  2  side in cross-sectional view of the plane that is orthogonal to the extending direction of the auxiliary groove  51  as illustrated in  FIGS. 4, 5 . 
     In the resonator  5 , the opening side portion  51 Ha of the hidden groove  51 H has a constant groove width, while the groove width of the groove bottom side portion  51 Hb of the hidden groove  51 H gradually increases to a vicinity of a middle of the groove bottom side portion  51 Hb in a region from the tread surface  2  side toward a groove bottom  51 HB side, and then gradually decreases or is maintained constant in a region from the vicinity of the middle of the groove bottom side portion  51 Hb to the groove bottom  51 HB. That is, the groove bottom side portion  51 Hb in this example has a deformed hexagonal shape in cross-sectional view of the plane that is orthogonal to the extending direction of the auxiliary groove  51 . 
     Alternatively, in the resonator of the present disclosure, the groove bottom side portion  51 Hb of the hidden groove  51 H may have, in cross-sectional view, a shape (e.g., a circular, elliptic or rhombic shape) in which the groove width gradually increases and gradually decreases from the tread surface  2  side toward a groove bottom  51 HB side, a shape (e.g., a quadrangular shape) in which the groove width is constant from the tread surface  2  side toward the groove bottom  51 HB side, a shape (e.g., a triangular or semicircular shape) in which the groove width always gradually increases from the tread surface  2  toward the groove bottom  51 Hb side, or the like. 
     Furthermore, the resonator of the present disclosure may include a configuration where the hidden groove  51 H does not include the opening side portion  51 Ha. That is, the hidden groove  51 H may have a configuration where the groove width gradually increases from the tread surface  2  side toward the groove bottom  51 HB side, and the opening width W 51 H in the tread surface  2  is therefore smaller than the groove width W 51 HB on the groove bottom  51 HB side. 
     Additionally,  FIG. 6  is a cross-sectional view along the d-d line of  FIG. 2 , and here illustrates a developed cross section along an opening center of the auxiliary groove  51 . The auxiliary groove  51  includes a groove deepest portion  51 Dp in which a groove depth in the auxiliary groove  51  is maximum, in at least the central portion of the auxiliary groove  51  in the extending direction. 
     In the resonator  5 , the groove deepest portion  51 Dp is provided adjacent to an end portion  51 Ga of the revealed groove  51 G of the auxiliary groove  51  on one side (a hidden groove  51 H side of the auxiliary groove  51 ) in the tire circumferential direction, and the groove depth D 51  of the auxiliary groove  51  locally increases in the groove deepest portion  51 Dp. Furthermore, in the resonator  5 , the groove depth D 51  of the auxiliary groove  51  in the revealed groove  51 G gradually increases from the groove deepest portion  51 Dp toward an end portion  51 Gb side of the revealed groove  51 G on the other side (a second branch groove  52   b  side) in the tire circumferential direction. In the resonator  5 , the groove deepest portion  51 Dp has a locally deepest groove depth; alternatively, the tire of the present disclosure may include a configuration where the groove depth of the auxiliary groove gradually increases from the end portions of the auxiliary groove on one side and the other side in the tire circumferential direction toward the central portion of the auxiliary groove in the extending direction, to form a groove deepest portion. In this case, it is considered that a portion having a groove depth in excess of twice an average depth of the auxiliary groove  51  is the groove deepest portion. 
     Furthermore, in the resonator  5 , the groove deepest portion  51 Dp is provided in the groove bottom of the revealed groove  51 G of the auxiliary groove  51 , but in another example, the groove deepest portion  51 Dp may be provided in a groove bottom of the hidden groove  51 H of the auxiliary groove  51  or provided in each of the groove bottoms of both the revealed groove  51 G and the hidden groove  51 H. 
     Additionally, in the resonator  5 , as illustrated in  FIG. 2 , the opening width W 51  of the revealed groove  51 G of the auxiliary groove  51  in the tread surface  2  gradually increases from one end  51 Ga of the revealed groove  51 G in the tire circumferential direction toward a maximum width position of the revealed groove  51 G, and gradually decreases from the maximum width position toward the other end  51 Gb of the revealed groove  51 G in the tire circumferential direction. 
     Alternatively, in the resonator of the present disclosure, in developed view of the tread surface  2 , the revealed groove  51 G may be formed in a shape in which the opening width of the revealed groove  51 G in the tread surface  2  is constant along an extending length of the revealed groove  51 G, a shape in which the opening width gradually increases or gradually decreases from one end toward the other end of the revealed groove  51 G, a shape in which the opening width repeats increasing and decreasing at a constant pitch, a shape in which the opening width irregularly increases and decreases, or the like. 
     Subsequently, operations and effects by the tire  1  according to this embodiment will be described. 
     As described above, in the tire  1 , the land portions  4  (in the present embodiment, the intermediate land portion  42   a ) is formed with the resonator  5  including the auxiliary groove  51  that terminates in the land portion  42   a , and at least one branch groove  52  that communicates between the auxiliary groove  51  and the circumferential main groove  3  (in the present embodiment, two branch grooves of the first branch groove  52   a  that communicates between the auxiliary groove  51  and the circumferential main groove  32   a , and the second branch groove  52   b  that communicates between the auxiliary groove  51  and the circumferential main groove  31   a ). Consequently, air column resonance sound generated in the circumferential main grooves  31   a ,  32   a  can be reduced by the resonator  5 . 
     Furthermore, in the tire  1 , the hidden groove  51 H having the opening width in the tread surface  2  that is smaller than the groove width of the groove bottom is provided in at least a part of the auxiliary groove  51 . In the hidden groove  51 H, the opening width W 51 H in the tread surface  2  is smaller than the groove width W 51 HB of the groove bottom  51 HB. Consequently, excessive decrease in rigidity of the land portion due to the resonator  5  provided in the tread surface  2  can be suppressed, and hence uneven wear in a tread can be suppressed. 
     Additionally, in the resonator  5  including this configuration, an air chamber volume can be sufficiently acquired on the groove bottom  51 HB side of the hidden groove  51 H, and hence the uneven wear in the tread can be suppressed while maintaining a frequency band of the resonator  5  in a range effective for the reduction of the air column resonance sound. Furthermore, in the tire  1  comprising the resonator  5 , it is hard to decrease rigidity of the land portion  4  formed with the resonator  5  (in the present embodiment, the intermediate land portion  4   a ), and hence steering stability in a cornering situation can improve. 
     Furthermore, in the tire  1 ,the hidden groove  51 H is provided with the opening side portion  51 Ha having the groove width maintained on the inner side in the tire radial direction (the groove depth direction) in the same manner as in the opening width W 51 H in the tread surface  2 . Consequently, the uneven wear in the tread around the resonator  5  can be more reliably suppressed. 
     Additionally, in the tire  1 ,the auxiliary groove  51  comprises the hidden groove  51 H, and the revealed groove  51 G excluding the hidden groove  51 H. According to this configuration, as compared with a configuration where the auxiliary groove  51  only comprises the hidden groove  51 H, a comparatively large groove volume of the auxiliary groove  1  can be acquired, and hence a drainage performance of the tire  1  can improve. Furthermore, a comparatively large opening area of the auxiliary groove  51  in the tread surface  2  can be acquired, and hence stone-trapping resistance or the like of the tire  1  can improve. 
     Note that in the tire of the present disclosure, the auxiliary groove  51  may only comprise the hidden groove  51 H. In this case, it is harder to decrease the rigidity of the land portion provided with the resonator  5 , and hence the uneven wear in the tread can be further reliably suppressed. 
     Furthermore, in the tire  1 ,the hidden groove  51 H is provided only in the end portion  51 Ea of the auxiliary groove  51  on one side in the tire circumferential direction. According to this configuration, during rolling of the loaded tire, the hidden groove  51 H functions as a pump (i.e., during the rolling of the loaded tire, the groove wall of the hidden groove  51 H collapses, to push air or water out of the auxiliary groove  1 ), and water that enters the auxiliary groove  51  can be efficiently discharged, so that the drainage performance of the tire  1  can improve. 
     Additionally, in the tire  1 , the hidden groove  51 H is provided only in the end portion  51 Ea of the auxiliary groove  51  on one side in the tire circumferential direction, and the branch groove  52  (in the present embodiment, the first branch groove  52   a ) is provided adjacent to the end portion  51 Ea of the auxiliary groove  51  on one side in the tire circumferential direction. In this configuration, opposite sides of the hidden groove  51  in the tire circumferential direction are opened in the tread surface  2 , and hence the groove wall of the hidden groove  51  is more appropriately easier to collapse. Consequently, a pump effect in the hidden groove  51  described above can be more suitably obtained, and the drainage performance of the tire  1  can further improve. 
     Note that in the tire of the present disclosure, the hidden groove  51 H may be provided in each of the end portion  51 Ea of the auxiliary groove  51  on one side in the tire circumferential direction and the end portion  51 Eb on the other side in the tire circumferential direction. In this case, it is easy to suitably maintain the rigidity of the land portion  4  formed with the resonator  5 , but it may be hard to sufficiently acquire the groove volume of the auxiliary groove  51 . Consequently, it is preferable that the hidden groove  51 H is provided only in either of the end portion  51 Ea of the auxiliary groove  51  on one side in the tire circumferential direction or the end portion  51 Eb on the other side in the tire circumferential direction. 
     Furthermore, in the tire  1 , the opening width W 51  of the revealed groove  51 G in the tread surface  2  gradually increases from one end of the revealed groove  51 G in the tire circumferential direction toward the maximum width position of the revealed groove  51 G, and gradually decreases from the maximum width position toward the other end of the revealed groove  51 G in the tire circumferential direction. In this case, during the rolling of the loaded tire, a groove width  51  of the central portion of the auxiliary groove  51  in the tire circumferential direction easily changes, and water that enters the auxiliary groove  51  can be efficiently discharged, so that the drainage performance can further improve. 
     Additionally, in the tire  1 ,the auxiliary groove  51  includes the groove deepest portion  51 Dp in which the groove depth D 51  in the auxiliary groove  51  is maximum, in at least the central portion of the auxiliary groove  51  in the extending direction. Thus, the groove deepest portion  51 Dp is provided, so that the groove volume of the auxiliary groove  51  can be easily acquired. Consequently, the drainage performance can further improve. 
     Note that in a case where the groove deepest portion  51 Dp is configured so that the depth of the auxiliary groove  51  locally increases in the groove deepest portion  51 Dp as in the tire  1  of the present embodiment, it is easier to maintain the rigidity of the land portion provided with the resonator  5  (in the present embodiment, the intermediate land portion  42   a ), and it is possible to more reliably suppress the uneven wear in the tread, as compared with a case where the groove deepest portion  51 Dp is configured so that the depth of the auxiliary groove  51  gradually decreases. 
     Furthermore, in the tire  1 , it is preferable that a ratio of the extending length of the hidden groove  51 H to an extending length of the auxiliary groove  51  in developed view of the tread surface  2  is 0.15 or more and 0.75 or less. If the ratio is 0.15 or more, the rigidity of the intermediate land portion  42   a  provided with the resonator  5  can be suitably maintained, and the uneven wear in the tread can be more reliably suppressed. Furthermore, if the ratio is 0.75 or less, the groove volume of the auxiliary groove  51  of the resonator  5  can be sufficiently acquired, and the drainage performance can further improve. 
     Note that from a viewpoint of further improving the drainage performance while more reliably suppressing the uneven wear in the tread, the ratio of the extending length of the hidden groove  51 H to the extending length of the auxiliary groove  51  in developed view of the tread surface  2  is more preferably 0.30 or more and 0.60 or less, and further preferably 0.35 or more and 0.55 or less. 
     Note that in the tire of the present disclosure, it is preferable that the opening width of the hidden groove  51 H of the auxiliary groove  51  in the tread surface  2  is 0.2 mm or more and 1.0 mm or less. If the opening width is 0.2 mm or more, it is easy to extract a mold to mold the hidden groove  51 H of the auxiliary groove  51  during manufacturing of the tire. If the opening width is 1.0 mm or less, it is easy to close the auxiliary groove  51  at an opening end of the hidden groove  51 H during ground contact of the tire. Furthermore, the groove walls that partition the hidden groove  51 H support each other, and hence the rigidity of the intermediate land portion  42   a  formed with the resonator  5  (especially, shearing rigidity) can be more suitably maintained. 
     Furthermore, it is preferable that in the tire of the present disclosure, a groove depth (a length along a normal line direction of the tread surface T) D 51 Ha of the opening side portion  51 Ha of the hidden groove  51 H of the auxiliary groove  51  is 1.0 mm or more and 4.0 mm or less. If the groove depth is 1.0 mm or more, rigidity in the opening side portion  51 Ha can be more suitably acquired. Furthermore, if the groove depth is 4.0 mm or less, a groove depth D 51 Hb of the groove bottom side portion  51 Hb is sufficiently provided, and the groove volume of the auxiliary groove  51  can be easily acquired. 
     Additionally, in the tire  1  according to the present embodiment, a plurality of resonators  5  described above are arranged in the intermediate land portion  42   a  via an equal space in the tire circumferential direction. Consequently, the air column resonance sound can be reduced in the tire circumferential direction, and the uneven wear in the tread can be suppressed. 
     Note that in the illustrated example, the resonator  5  described above is provided only in the intermediate land portion  42   a , but in the tire of the present disclosure, the resonator  5  described above may be provided also in the other land portion  4 . In this case, the air column resonance sound in the other circumferential main groove  3  with which the resonator  5  communicates is also reduced, and hence a sum of the air column resonance sound generated in the tire can be reduced. 
     Here, in the vehicle-installed inside half portion HA, it is preferable that a ground contact width of the internal shoulder land portion  43   a  (a tire widthwise distance between ground contact ends of a contact patch when the tire is mounted to an applicable rim, filled with a prescribed internal pressure, and loaded with a maximum load) is smaller than a ground contact width of the internal intermediate land portion  42   a.    
     Furthermore, in the vehicle-installed outside half portion HB, it is preferable that a ground contact width of the external shoulder land portion  43   b  is smaller than a ground contact width of the external intermediate land portion  42   b.    
     Additionally, in case where the central land portion  41  is formed as in the embodiment illustrated in  FIG. 1 , it is preferable that a ground contact width of the central land portion  41  is minimum among the plurality of land portions. 
     In the present disclosure, it is preferable that the groove width of the internal circumferential main groove  32   a  located on an outermost side in the tire width direction is maximum among the plurality of circumferential main grooves. This is because it is easy to increase a ground contact length on a vehicle-installed inside during running, and such easiness noticeably contributes to a hydroplaning performance and can therefore effectively improve the hydroplaning performance. 
     In the present disclosure, for an edge length per unit area in the tire width direction, it is preferable that an edge length per unit area of the external shoulder land portion  43   b  in the tire width direction is larger than an edge length per unit area of the internal shoulder land portion  43   a  in the tire width direction. 
     Furthermore, for the edge length per unit area in the tire width direction, it is preferable that an edge length per unit area of the external intermediate land portion  42   b  in the tire width direction is larger than an edge length per unit area of the internal intermediate land portion  42   a  in the tire width direction. 
     Additionally, for an edge length per unit area in the tire circumferential direction, it is preferable that an edge length per unit area of the internal shoulder land portion  43   a  in the tire circumferential direction is larger than an edge length per unit area of the external shoulder land portion  43   b  in the tire circumferential direction. 
     This is because the ground contact length can be optimized, the performance of the resonator can be more effectively exhibited, and quietness can be further improved. 
     EXAMPLES 
     Hereinafter, examples of the present disclosure will be described, but the present disclosure is not limited to the following examples. 
     Example Tire and Comparative Example Tire (both had a tire size of 215/55R17) are experimentally produced under specifications illustrated in Table 1, and reduction effect of air column resonance sound (quietness) and uneven wear resistance are evaluated. 
     Example Tire 1 has a tread pattern illustrated in  FIG. 1 , and comprises a resonator illustrated in  FIGS. 1 to 5 . 
     Comparative Example Tire 1 is a tire similar to Example Tire 1 except that the tire does not comprise a resonator in a land portion. 
     Comparative Example Tire 2 is a tire similar to Example Tire 1 except that the tire comprises a conventional resonator in a land portion (does not include a hidden groove in an auxiliary groove). 
     Example Tire 2 is a tire similar to Example Tire 1 except that an auxiliary groove of a resonator only comprises a hidden groove. 
     Example Tire 3 is a tire similar to Example Tire 1 except that a hidden groove of an auxiliary groove of a resonator is provided in a central portion of the auxiliary groove. 
     Example Tire 4 is a tire similar to Example Tire 1 except that a hidden groove is provided in each end portion of an auxiliary groove in a tire circumferential direction. 
     Example Tire 5 is a tire similar to Example Tire 1 except that a branch groove is not provided adjacent to one end portion of an auxiliary groove in a tire circumferential direction. 
     Example Tire 6 is a tire similar to Example Tire 1 except that a shape of a revealed groove in a tread surface is rectangular. 
     Example Tire 7 is a tire similar to Example Tire 1 except that the tire does not include a groove deepest portion in an auxiliary groove. 
     Example Tire 8 is a tire similar to Example Tire 1 except that a groove deepest portion in an auxiliary groove is formed so that a groove depth of the auxiliary groove gradually increases. 
     Each of Example Tires 9 to 12 is a tire similar to Example Tire 1 except that a ratio of an extending length of a hidden groove to an extending length of an auxiliary groove is different. 
     (Reduction Effect of Air Column Resonance Sound) 
     Each sample tire is assembled to a rim  7 . 5 J to form a tire wheel. When the tire is applied with an air pressure of 230 kPa (an equivalent pressure) and a tire load of 4.46 kN and is run at a speed of 80 km/h on an indoor drum test machine, tire side sound is measured on conditions determined in accordance with JASO C606 standards. Then, a partial overall value in a ⅓ octave center frequency 800-1000-1250 Hz band is computed, and air column resonance sound is calculated. Table 1 illustrates the results with a reduction amount (%) of the air column resonance sound to Comparative Example Tire 1. A larger percentage indicates a larger reduction amount of the air column resonance sound. 
     (Uneven Wear Resistance) 
     Each sample tire is assembled to a rim  7 . 5 J to form a tire wheel, and the tire is applied with an air pressure of 230 kPa (an equivalent pressure) and a tire load of 4.46 kN, and is run as much as 10000 km at a speed of 80 km/h on an indoor drum test machine. Afterward, a worn state of a tread surface is visually confirmed. Table 1 illustrates the results. An uneven wear resistance of Comparative Example Tire 1 evaluated by an uneven wear amount is regarded as 1,and evaluation in five stages is performed. A larger numeric value indicates more excellency in uneven wear resistance. 
     (Drainage Performance) 
     Each sample tire is assembled to a rim ( 7 . 5 J) to form a wheel, and the tire is filled with an air pressure of 230 kPa (an equivalent pressure) and installed in a passenger vehicle. Afterward, the vehicle accelerates from a slow state in an evaluation course where water is sprayed over a paved road surface until a water depth reached 7 mm, and a vehicle speed when a slip rate of the tire reached 10% (a speed when the tire span on water) is obtained, to evaluate a drainage performance (an anti-hydroplaning performance). Table 1 illustrates the results. The drainage performance of Comparative Example Tire  1  by the above vehicle speed is regarded as 100, and drainage performances of the other tires are indexed and evaluated. A larger numeric value indicates more excellency in drainage performance. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Ratio of 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                   
                   
                 extending 
                   
                   
                   
                   
                 Quietness 
               
               
                   
                   
                 length of 
                   
                   
                   
                   
                 (air 
               
               
                   
                   
                 hidden 
                   
                   
                   
                   
                 column 
               
               
                   
                   
                 groove to 
                 Position of 
                 Position of 
                   
                   
                 resonance 
               
               
                   
                   
                 extending 
                 hidden 
                 branch 
                   
                 Shape of 
                 sound 
                   
                 Uneven 
               
               
                   
                 Presence 
                 length of 
                 groove in 
                 groove to 
                 Shape of 
                 groove 
                 reduction 
                 Reduction 
                 wear 
                 Drainage 
               
               
                   
                 of 
                 auxiliary 
                 auxiliary 
                 auxiliary 
                 revealed 
                 deep 
                 amount 
                 amount 
                 resistance 
                 performance 
               
               
                   
                 resonator 
                 groove (%) 
                 groove 
                 groove 
                 groove 
                 portion 
                 (dB)) 
                 (%) 
                 (INDEX) 
                 (INDEX) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Example 
                 Present 
                 45 
                 One side 
                 Both side end 
                 Almost 
                 Local 
                 1.5 
                 −29% 
                 7 
                 107 
               
               
                 Tire 1 
                   
                   
                 end portion 
                 portions 
                 rhombic 
               
               
                 Comparative 
                 None 
                 — 
                 — 
                 — 
                 — 
                 — 
                 0 
                  0% 
                 10 
                 100 
               
               
                 Example 
               
               
                 Tire 1 
               
               
                 Comparative 
                 Present 
                  0 
                 — 
                 Both side end 
                 Almost 
                 — 
                 1.5 
                 −29% 
                 2 
                 105 
               
               
                 Example 
                   
                   
                   
                 portions 
                 parallelogram 
               
               
                 Tire 2 
               
               
                 Example 
                 Present 
                 100  
                 One side 
                 Both side end 
                 Almost 
                 Local 
                 1.5 
                 −29% 
                 8 
                 101 
               
               
                 Tire 2 
                   
                   
                 end portion 
                 portions 
                 rhombic 
               
               
                 Example 
                 Present 
                 45 
                 Central 
                 Both side end 
                 Almost 
                 Local 
                 1.5 
                 −29% 
                 6 
                 105 
               
               
                 Tire 3 
                   
                   
                 portion 
                 portions 
                 rhombic 
               
               
                 Example 
                 Present 
                 90 
                 Both side 
                 Both side end 
                 Almost 
                 Local 
                 1.5 
                 −29% 
                 8 
                 102 
               
               
                 Tire 4 
                   
                   
                 end portions 
                 portions 
                 rhombic 
               
               
                 Example 
                 Present 
                 45 
                 One side 
                 Central 
                 Almost 
                 Local 
                 1.5 
                 −29% 
                 5 
                 106 
               
               
                 Tire 5 
                   
                   
                 end portion 
                 portion 
                 rhombic 
               
               
                 Example 
                 Present 
                 45 
                 One side 
                 Both side end 
                 Rectangular 
                 Local 
                 1.5 
                 −29% 
                 5 
                 106 
               
               
                 Tire 6 
                   
                   
                 end portion 
                 portions 
               
               
                 Example 
                 Present 
                 45 
                 One side 
                 Both side end 
                 Almost 
                 — 
                 1.5 
                 −29% 
                 5 
                 106 
               
               
                 Tire 7 
                   
                   
                 end portion 
                 portions 
                 rhombic 
               
               
                 Example 
                 Present 
                 45 
                 One side 
                 Both side end 
                 Almost 
                 Non-local 
                 1.5 
                 −29% 
                 5 
                 107 
               
               
                 Tire 8 
                   
                   
                 end portion 
                 portions 
                 rhombic 
               
               
                 Example 
                 Present 
                 10 
                 One side 
                 Both side end 
                 Almost 
                 Local 
                 1.5 
                 −29% 
                 2 
                 105 
               
               
                 Tire 9 
                   
                   
                 end portion 
                 portions 
                 rhombic 
               
               
                 Example 
                 Present 
                 15 
                 One side 
                 Both side end 
                 Almost 
                 Local 
                 1.5 
                 −29% 
                 3 
                 105 
               
               
                 Tire 10 
                   
                   
                 end portion 
                 portions 
                 rhombic 
               
               
                 Example 
                 Present 
                 75 
                 One side 
                 Both side end 
                 Almost 
                 Local 
                 1.5 
                 −29% 
                 7 
                 103 
               
               
                 Tire 11 
                   
                   
                 end portion 
                 portions 
                 rhombic 
               
               
                 Example 
                 Present 
                 80 
                 One side 
                 Both side end 
                 Almost 
                 Local 
                 1.5 
                 −29% 
                 7 
                 102 
               
               
                 Tire 12 
                   
                   
                 end portion 
                 portions 
                 rhombic 
               
               
                   
               
            
           
         
       
     
     REFERENCE SIGNS LIST 
       1  tire 
       2  tread surface 
       3 ,  31   a ,  31   b ,  32   a  and  32   b  circumferential main groove 
       4  land portion 
       41  central land portion 
       42   a  and  42   b  intermediate land portion 
       43   a  and  43   b  shoulder land portion 
       5  resonator 
       51  auxiliary groove 
       51 Ea end portion of the auxiliary groove on one side in a tire circumferential direction 
       51 Eb end portion of the auxiliary groove on the other side in the tire circumferential direction 
       51 Dp groove deepest portion 
       51 G revealed groove 
       51 H hidden groove 
       52  branch groove 
       52   a  first branch groove 
       52   b  second branch groove 
     CL tire equator plane 
     HA tire half portion on one side 
     HB tire half portion on the other side 
     TE tread edge