Patent Publication Number: US-2022227181-A1

Title: Tire

Description:
TECHNICAL FIELD 
     The present invention relates to tires, and more particularly to a tire suitable for improving a durability of a heavy-load tire used in heavy-load vehicles such as large dump trucks, construction vehicles and the like. 
     BACKGROUND 
     Conventionally, a heavy-load tire as shown in Patent Document 1 has been known. In such a tire, a tread gauge is made thick so as to improve a wear life. 
     CITATION DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Unexamined Patent Application Publication No. 2008-114738. 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     However, if the tread gauge is made thick, a heating temperature in a tread portion is increased, which results in degrading the durability of structural members such as a belt, hence it is likely to impair functions as a tire. 
     The present invention has been made in view of the above-mentioned problem, and aims at providing a tire capable of suppressing the increase in the heating temperature in the tread portion. 
     Solution to Problem 
     As a configuration of the tire for solving the above-mentioned problem, a tire according to an aspect of the invention includes: circumferential grooves each formed along a circumferential direction of a tire; lateral grooves provided at predetermined intervals along the circumferential direction of the tire, each of the lateral grooves having one end being opened to a side of the tire and the other end being communicated with the circumferential groove; and narrow grooves provided in blocks defined by the circumferential grooves and the lateral grooves, each of the narrow grooves having one end being opened to the side of the tire and the other end being communicated with the circumferential groove, in which the tire includes a projecting surface that projects, at a position more to one side or the other side in the circumferential direction of the tire than the narrow groove that is opened to the tire side, further to an outer side in a tire width direction than a tire side shape to which the narrow groove is opened, and in which the projecting surface extends in a tire radial direction from a ground contact end so as to include a groove bottom of the narrow groove. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are a plan view of a tread portion and a cross-sectional view of a tire, respectively; 
         FIG. 2  is an external perspective view of a shoulder block; 
         FIGS. 3A and 3B  are a cross-sectional view of a part cut by A-A line shown in  FIG. 1A  and a plan view of a side of the tire, respectively; 
         FIG. 4  is a diagram illustrating an action of a projecting part at the time when the tire is in contact with the ground; 
         FIG. 5  is a diagram illustrating another form of the projecting part; 
         FIGS. 6A and 6B  are diagrams illustrating another form of the projecting part; and 
         FIG. 7  is a diagram illustrating another form of the projecting part. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present invention will be described in detail below through embodiments of the invention; however, the following embodiments are not intended to limit the inventions set forth in the claims, and all of combinations of the features described in the embodiments are not necessarily essential to the solving means of the invention, but selectively employed configurations are included. 
       FIGS. 1A and 1B  are a plan view of a tread portion and a cross-sectional view of a tire, respectively. A tire T illustrated in  FIGS. 1A and 1B  has a structure applied to a heavy-load tire. 
     As illustrated in  FIG. 1B , the tire T includes a bead core  12 , a carcass  14 , a belt  16  and a chafer  18 , which are formed of mainly cord members, and a bead filler  20 , a belt under rubber  22 , a rim cushion rubber  24 , a side rubber  26 , a base rubber  28 , a tread rubber  30  and an inner liner  32 , which are formed of mainly rubber members. 
     Incidentally, in the following description, directions are explained, as illustrated in  FIG. 1 , as a tire width direction, a tire circumference direction and a tire radial direction. With respect to the tire width direction, the direction is defined such that, in the direction of a paper surface, right and left are defined with a tire center CL as a center line separating to right and left, a tire center Cl side is defined as an inner side, and each end part Tt side of right and left-ground contact surfaces Tm is defined as an outer side, and so on. For the convenience of explanation, a direction of rotation of the tire T is specified as shown by the arrows in the figure. 
     The bead core  12  is formed in a ring shape and is provided in pair on the right and left-sides of the tire T. The carcass  14  is configured of one or more carcass plies stacked on top of each other, and is folded back so as to be rolled up from the inner side to the outer side of each bead core  12 , to thereby extend in a toroidal shape between the bead cores  12 . The belt  16  is configured of one or more belt plies stacked on top of each other and is provided by winding a crown part of the toroidally formed carcass  14  in the circumferential direction. The chafer  18  is formed in a sheet shape and is provided so as to enclose the outer side of the carcass  14  wound to the bead core  12 . 
     The bead filler  20  is provided between the carcass  14  folded over the bead core  12 . The belt under-rubber  22  is provided between the carcass  14  at each end part in the tire width direction of the belt  16 . The rim cushion rubber  24  is provided on the outer side in the tire width direction of the chafer  18 . The side rubber  26  is provided on the outer side in the tire radial direction of the rim cushion rubber  24  so as to cover the outer side in the tire width direction of the belt under rubber  22 . The base rubber  28  is provided on the outer side in the tire radial direction of the belt  16  and extends between the right and left-side rubbers  26 . The tread rubber  30  is provided over the base rubber  28  on the outer side in the tire radial direction and extends so as to cover the right and left-side rubbers  26  to thereby form the tread portion of the tire T. The inner liner  32  is provided so as to cover the entire inner circumference of the toroidally formed carcass  14 , and provides airtightness as a pneumatic tire. 
     As illustrated in  FIG. 1A , a tread pattern configured of a block pattern is formed on the tread rubber  30 . The block pattern according to the present embodiment is formed by defining two shoulder land portions  50 ;  52  that are continuous in the tire circumferential direction and a center land portion  54  by a plurality (two in the present embodiment) of circumferential grooves  40 ;  42  extending in a zigzag manner in the tire circumferential direction, and by arranging plural numbers of lateral grooves  44 ;  46 ;  48  that extend in the tire width direction, in each of the land portions  50 ;  52 ;  54  at predetermined intervals in the tire circumferential direction. 
     The lateral grooves  44  are formed in the shoulder land portion  50  in such a matter that one end thereof is opened to one of tire sides Ts and the other end thereof is communicated with the circumferential groove  40 , and are provided at predetermined intervals in the tire circumferential direction. In other words, the shoulder land portion  50  is configured by arranging shoulder blocks  50 A, which are defined by adjacent lateral grooves  44 ;  44  and the circumferential groove  40 , continuously in the tire circumferential direction. 
     The lateral grooves  46  are formed in the other shoulder land portion  52  in such a matter that one end thereof is opened to the other one of the tire sides Ts and the other end thereof is communicated with the circumferential groove  42 , and are provided at predetermined intervals in the tire circumferential direction. In other words, the shoulder land portion  52  is configured by arranging shoulder blocks  52 A, which are defined by adjacent lateral grooves  46 ;  46  and the circumferential groove  42 , continuously in the tire circumferential direction. 
     The lateral grooves  48  are formed in the center land portion  54  to be inclined at a predetermined angle with respect to the tire width direction, so as to be communicated with the circumferential groove  40  and the circumferential groove  42 , and are provided at predetermined intervals in the tire circumferential direction. In other words, the center land portion  54  is configured by arranging center blocks  54 A, which are defined by adjacent lateral grooves  48 ;  48  and the circumferential grooves  40 ;  42 , continuously in the tire circumferential direction. 
     Incidentally, the block pattern according to the present embodiment is formed so that the direction of rotation is not designated when the tire is mounted on a vehicle. That is, the block pattern was formed such that, when the ground contact surface Tm is plane viewed, the block pattern becomes symmetry (point-symmetry) around a point set at an arbitrary position on the tire center CL. In other words, the block pattern was formed by rotating 180° the left side from the tire center CL and aligning the positions of the lateral grooves  48  that define the center block  54 A. And, for example, the tire is mounted on the vehicle so that the circumferential groove  40  side is on the outer side of the vehicle body and the circumferential groove  42  is on the vehicle side. 
     The circumferential groove  40  is configured of an inclined groove  40 A and an inclined groove  40 B that extend in a zigzag pattern while alternately inclined in opposite directions with respect to the tire circumferential direction, and the circumferential groove  42  is formed of an inclined groove  42 A and an inclined groove  42 B that extend in a zigzag pattern while alternately inclined in opposite directions with respect to the tire circumferential direction. In the present embodiment, since the tread pattern is point-symmetry, the inclined groove  40 A of the circumferential groove  40  corresponds to the inclined groove  42 A of the circumferential groove  42 , and the inclined groove  40 B of the circumferential groove  40  corresponds to the inclined groove  42 B of the circumferential groove  42 . 
     In the circumferential groove  40 , the inclined groove  40 A is formed to be inclined along the tire rotation direction from the outer side toward the inner side in the tire width direction, and the inclined groove  40 B is formed to be inclined along the tire rotation direction from the inner side toward the outer side in the tire width direction. In the circumferential groove  42 , the inclined groove  42 A is formed to be inclined along the tire rotation direction from the inner side toward the outer side in the tire width direction, and the inclined groove  42 B is formed to be inclined along the tire rotation direction from the outer side toward the inner side in the tire width direction. 
     The lateral grooves  44  are formed so as to extend from a tire side in a bowed manner in the tire width direction and to be smoothly continuous with the inclined grooves  40 B, and the lateral grooves  46  are formed so as to extend from a tire side in a bowed manner in the tire width direction and to be smoothly continuous with the inclined grooves  42 B. 
     The lateral grooves  48  are formed so as to incline in the same direction as the inclined grooves  40 B and the inclined grooves  42 B. An angle at which the lateral groove  48  is inclined is set to be smaller than an angle at which the inclined groove  40 B and the inclined groove  42 B intersect with respect to the tire width direction, and are communicated with the inclined groove  40 B and the inclined groove  42 B. 
     With respect to the lateral grooves  44 ;  46 , groove widths w 44 ; w 46  (see  FIG. 3B ) are set to be wider than, for example, a groove width of the inclined groove  40 B and a groove width of the inclined groove  42 B to which the lateral grooves  44 ;  46  are connected. 
     The above-mentioned circumferential grooves  40 ;  42  and the lateral grooves  48  are grooves that serve as references for determining a usage limit due to wear, and are provided with wear indicators that indicate the usage limit of the tire T. The lateral grooves  44 ;  46  are formed in such a manner that depths thereof on the circumferential grooves  40 ;  42  sides are formed at the same depth as that of the circumferential grooves  40 ;  42 , and gradually become deeper in an arc shape as the lateral grooves  44 ;  46  go in the tire width direction. In other words, the lateral grooves  44 ;  46  are formed to open wide in the tire radial direction at the tire side so that a groove depth h 44   z  of the opening at the tire side becomes deeper than a groove depth h 44  on the circumferential groove  40 ;  42  side (see  FIG. 3B ). 
       FIG. 2  is an external perspective view of the shoulder block.  FIGS. 3A and 3B  are a cross-sectional view of a part cut by A-A line shown in  FIG. 1A  and a plan view of a side of the tire, respectively. Hereinafter, the configuration of the shoulder block will be described using  FIG. 1  to  FIGS. 3A and 3B . However, as described above, since the tread pattern according to the present embodiment is point-symmetry, an explanation will be given using the shoulder block  50 A, which is defined by the circumferential groove  40  and lateral grooves  44 ;  44  adjacent to each other in the tire circumferential direction. 
     As illustrated in  FIG. 1A  and  FIG. 2 , the shoulder block  50 A has a narrow groove  60  extending along an extended direction of the shoulder block  50 A. The narrow groove  60  is formed in such a manner that one end opens to the tire side surface Ts and the other end opens to the inclined groove  40 B of the circumferential groove  40 . Specifically, the narrow groove  60  is formed so as to extend midway between the groove wall  44   a  of the lateral groove  44  that is continuous with the groove wall ml of the inclined groove  40 A and the groove wall  44   b  of the other lateral groove  44  that defined the shoulder block  50 A. 
     The narrow groove  60  is formed with the same depth from one end side to the other end side in the extension direction, for example, from the ground contact surface Tm. As illustrated in  FIG. 3B , a groove depth h 60  of the narrow groove  60  may be set within a range of, for example, 50% to 100% preferably 60% to 95%, more preferably 65% to 90%, and even more preferably 70% to 85% of the groove depth h 40  of the circumferential groove  40 . 
     Further, a groove width w 60  of the narrow groove  60  may be, for example, 2% to 8%, preferably 3% to 7%, and more preferably 4% to 6% of a distance L 1  in the tire circumferential direction of the lateral grooves  44 ;  44  that define the shoulder block  50 A. 
     Incidentally, also in the shoulder block  52 A, a narrow groove  62  is formed as similarly to the shoulder block  50 A. 
     As illustrated in  FIG. 1A , the center block  54 A includes a narrow groove  64  that extends along the extension direction of the lateral grooves  48  that define the center block  54 A. The narrow groove  64  is formed in such a manner that one end opens to the inclined groove  40 A of the circumferential groove  40  and the other end opens to the inclined groove  42 A of the circumferential groove  42 . The narrow groove  64  is formed so as to extend midway between the groove wall  48   a  of one lateral groove  48  and the groove wall  48   b  of the other lateral groove  48  that define the shoulder block  54 A. 
     The narrow groove  64  is formed, for example, with the same depth from the ground surface Tm, from one end side to the other end side in the extension direction. A groove depth h 64  of the narrow groove  64  may be set within a range of, for example, 50% to 100%, preferably 60% to 95%, more preferably 65% to 90%, and even more preferably 70% to 85% of the groove depth h 40  of the circumferential groove  40 . 
     Further, a groove width w 64  of the narrow groove  64  may be, for example, 2% to 8%, preferably 3% to 7%, and more preferably 4% to 6% of a distance L 2  between center lines of the lateral grooves  44 ;  44  defining the shoulder block  50 A. 
     As described above, by forming the narrow grooves  60 ;  62  in the shoulder blocks  50 A;  52 A and the narrow groove  64  in the center block  54 A, the shoulder blocks  50 A;  52 A and the center block  54 A are formed so as to have two small blocks in appearance, to an extent that each of the narrow grooves  60 ;  62  does not disappear due to wear. 
     By providing the narrow grooves  60 ;  62 ;  64  in the shoulder blocks  50 A;  52 A and the center block  54 A, surface areas of the shoulder blocks  50 A;  52 A and the center block  54 A can be increased, and a heat dissipation area can be widened even when a thickness of the tread rubber  30  is made thick. 
     As illustrated in  FIG. 1  to  FIGS. 3A, 3B , a projecting part  70  that extends in the tire width direction is provided on the tire side surface Ts side of the shoulder block  52 A. The projecting part  70  is provided, for example, in correspondence with the narrow groove  60 . 
     The projecting part  70  has a projecting wall  72  that projects in the tire width direction with an even thickness along the tire circumferential direction. The projecting wall  72  has a first projecting wall  73  formed on the outer side in the tire radial direction and a second projecting wall  74  formed continuously with the first projecting wall  73  on the inner side in tire radial direction, continuous with the first projecting wall  73 . 
     As illustrated in  FIG. 3A , the first projecting wall  73  is formed in such a manner that, in a cross-sectional view, an amount of projection gradually increases in the tire width direction than a basic shape F of the tire side surface Ts, as the first projecting wall  73  goes from the edge Tt side of the ground contact surface Tm to the inner side in the tire radial direction. The basic shape F refers to a cross-sectional outline shape of the tire side surface Ts at a position where the projecting part  70  is not formed. 
     As illustrated in  FIGS. 3A and 3B , the first projecting wall  73  is formed, with respect to the tire radial direction, for example, within a range extended in the tire width direction from the end part Tt of the ground contact surface Tm to a groove bottom  60   z  of the narrow groove  60 . 
     Also, as illustrated in  FIG. 3B , the first projecting wall  73  is formed, with respect to the tire circumferential direction, within a range extended from a rear position distant by a distance L 3  from the groove wall  60   b  on the rear side in the tire rotational direction of the narrow groove  60  that is opened to the tire side surface Ts, to the groove wall  44   b  on the front side in the tire rotational direction of the lateral groove  44  that forms the shoulder block  50 A. 
     An end surface (hereinafter referred to as the projecting surface)  73 A on the front side in the tire rotation direction of the first projecting wall  73  is formed, for example, in a planar shape extending along the tire radial direction and the tire width direction. The projecting surface  73 A is not limited such that an edge part  81  forming the projecting surface  73 A extends in the tire radial direction, but may be formed so as to be inclined with respect to the tire radial direction, or may be formed so as to extend in parallel with an edge part  82  forming an end surface  74 B described later. Further, an end surface  73 B in the tire rotation direction of the first projecting wall  73  is formed in a planar shape in which the groove wall  44   b  is continuously extended in the tire width direction. 
     The second projecting wall  74  is formed in such a manner that, in a cross-sectional view, an amount of projection gradually decreases in the tire radial direction than the basic shape F of the tire side surface Ts, as the second projecting wall  74  goes from the inner side in the tire radial direction of the first projecting wall  73  further to the inner side in the tire radial direction. 
     As illustrated in  FIGS. 3A and 3B , the second projecting wall  74  is formed, with respect to the tire radial direction, within a range in which the second projecting wall  74  continues from the inner side in the tire radial direction of the first projecting wall  73  to the basic shape F at the outer side in the tire radial direction outer by a predetermined distance than the position of an opening groove bottom  44   x  where the lateral groove  44  is opened to the tire side surface Ts. That is, the second projecting wall  74  is formed in such a manner that a boundary  74   z  between the second projecting wall  74  and the basic shape F is located more outward in the tire radial direction than the location of the opening groove bottom  44   x.    
     Also, as illustrated in  FIG. 3B , the second projecting wall  74  is formed, with respect to the tire circumferential direction, within a range extending from a position where the groove wall  60   b  on the rear side in the tire rotational direction of the narrow groove  60 , which is opened to the tire side surface Ts, is extended in the tire radial direction to the groove wall  44   b  on the front side in the tire rotation direction of the lateral groove  44 , which forms the shoulder block  50 A. 
     An end surface (hereinafter referred to as the projecting surface)  74 A on the front side in the tire rotation direction of the second projecting wall  74  is formed, for example, in a planar shape extending along the tire radial direction and the tire width direction. Further, the end surface  74 B in the tire rotation direction of the second projecting wall  74  is formed in a planar shape so as to be flush with the end surface  73 B of the first projecting wall  73 . 
     As described above, since the projecting surface  73 A and the projecting surface  74 A are formed as being displaced in the tire rotational direction, these surfaces are connected via a connecting surface  76 . The connecting surface  76  is formed in a spherical shape, for example. 
     As illustrated in  FIG. 2 , the connecting surface  76  is formed, for example, by a spherical surface with an intersection point p, as a center, at which an extension line f 1  that is an extension of a boundary edge  83  along the tire circumferential direction and an extension line f 2  of the edge part  82  forming the end surface  74 B intersect. 
     By making the connecting surface  76  spherical, cracks that occur, when the projecting surface  73 A and the projecting surface  74 A come into contact with uneven road surfaces, stones and the like, between the projecting surface  73 A and the projecting surface  74 A can be prevented. 
     As such, with the provision of the projecting part  70 , the air flowed along the tire side surface Ts collides with the projecting surface  73 A, the projecting surface  74 A and the connecting surface  76 , and flows in the tire radial direction and the tire width direction. Of the air, air flowed toward the inner side in the tire width direction flows into the narrow grooves  60  provided in the shoulder blocks  50 A, creates a forced flow in the narrow grooves  60 , thus can actively cool each of the shoulder blocks  50 A. 
       FIG. 4  is a diagram illustrating an action of the projecting part  70  at the time when the tire is in contact with the ground. Furthermore, when the ground surface Tm is brought into contact with the road surface  3 , the projecting part  70  is pushed and deformed by the weight of the vehicle toward the road surface  3  from a state indicated by the dotted line in the figure. At this time, since the connecting surface  76  moves in the direction of the road surface  3 , the connecting surface  76  acts to push the air in the area surrounded by the connecting surface  76 , the projecting surface  73 A, and the road surface  3  toward the road surface  3 , and causes the pushed air to flow into the narrow groove  60 . This makes it possible to increase an amount of air than the amount of air more than an amount of air flowing into the grooves  60  other than being in contact with the ground. In this way, each shoulder block  50 A can be cooled by allowing air to flow into the narrow grooves  60  at the time the tire contacts with the ground, which is a main cause of heat generation in the tire T. As a result, the heat generation in the tread portion is suppressed, hence the durability of the tire T can be improved. 
     Next, an explanation will be given as to the function of the projecting part  70  provided in the shoulder block  52 A. In the present embodiment, since the tread pattern was made to be point-symmetry, the projecting part  70  provided in the shoulder block  52 A is located on the front side in the tire rotation direction of the narrow groove  62 . In other words, the projecting surface  73 A and the projecting surface  74 A at the narrow groove  62  are located on the rear side in the tire rotation direction. 
     In this case, by the air flowed through the tire side surface Ts and past the projecting part  70 , pressures on the projecting surface  73 A side and on the projecting surface  74 A side become negative, and act to suck out the air in the narrow groove  62 . 
     Therefore, similar to the case where the explanation was given using the shoulder block  52 A described above, because a forced flow can be generated in the narrow groove  62 , the shoulder block  52 A can be cooled from the inside. 
     As described above, according to the present embodiment, by having provided the narrow grooves  60 ;  62 , which are opened to the tire side surface Ts, in the shoulder blocks  50 A;  52 A of the tire T in which the block pattern was formed, and having provided the projecting parts  70 , which extend in the tire width direction, in correspondence with the narrow grooves  60 ;  62 , the forced air flow can be created in the narrow grooves  60 ;  62 . Whereby, the shoulder block  50 A is cooled from the outside by the air flowing through the lateral grooves  44 ;  44  and the circumferential grooves  40  that define the shoulder block  50 A, and is also cooled from the inside by the air forcibly flowing through the narrow grooves  60 . In addition, the shoulder block  52 A is cooled from the outside by the air flowing through the lateral grooves  46 ;  46  and the circumferential grooves  42  that define the shoulder block  52 A, and is also cooled from the inside by the air forcibly flowing through the narrow grooves  60 . Therefore, even if the thickness of the tread rubber  30  is made thick, increase in the temperature of the tread portion can be suppressed, hence the durability of the tire T can be improved. 
       FIG. 5  is a diagram illustrating another form of the projecting part  70 . 
     In the above-described embodiment, the projecting part  70  has been described as being formed with a uniform thickness in the tire circumferential direction, but is not limited thereto. For example, as illustrated in  FIG. 5 , the projecting part  70  may be formed such that the thickness becomes thinner as the projecting part  70  goes toward the rear side in the tire rotation direction. That is, the projecting part  70  may be formed so that the end surfaces on the rear end sides of the first projecting wall  73  and the second projecting wall  74  are eliminated. 
     Further, in the above-described embodiment, the projecting part  70  has been described as being formed, with respect to the tire radial direction, within a range in which the projecting part  70  continues from the end part Tt of the ground contact surface Tm to the basic shape F at a position in the tire radial direction upper than the position of the opening groove bottom  44   x  where the lateral groove  44  is opened to the tire side surface Ts, but is not limited thereto. The projecting part  70  may be formed so as to include at least from the end part Tt of the ground contact surface Tm to the groove bottom  60   z  of the narrow groove  60 . 
       FIGS. 6A and 6B  are diagrams illustrating another form of the projecting part  70 . In the above-described embodiment, the connecting surface  76  has been described as being formed in the spherical shape, but is not limited thereto. For example, as illustrated in  FIGS. 6A and 6B , the connecting surface  76  may be a planer surface orthogonal to the projecting surface  73 A and the projecting surface  74 A, or may be an arcuate surface formed along the tire circumferential direction. 
     Further, the projecting part  70  may be formed, with respect to the tire radial direction, for example, so as to extend from the end part Tt of the ground contact surface Tm to the tire maximum width part Tw. The projecting part  70  may be formed from the end part Tt of the ground contact surface Tm within a range of preferably 50% to 80%, more preferably 55% to 75%, and even more preferably 60% to 70% of a distance L 4  from the end part Tt of the ground contact surface Tm to the tire maximum width part Tw. 
       FIG. 7  illustrates another form of the projecting part  70 . The projecting part  70  has been described, with respect to the tire width direction, as being gradually projected in the tire width direction as it goes from the end part Tt of the ground contact surface Tm toward the tire radial direction, but is not limited thereto. For example, as illustrated in  FIG. 7 , the projecting part  70  may be made to project in the tire width direction beforehand at the end part Tt of the ground contact surface Tm, and the projecting surface  73 A may be made to have a rectangular shape instead of the triangular shape illustrated in  FIG. 3A . 
     The tire T equipped with the projecting part  70  according to the present embodiment is particularly suitable as a heavy-load tire for trucks, buses, construction vehicles and the like, whose continuous operating time is long and, in addition, the load on the tire is large. 
     In summary, the present invention can be described as follows. Namely, a tire according to an aspect of the invention includes: circumferential grooves each formed along a circumferential direction of a tire; lateral grooves provided at predetermined intervals along the circumferential direction of the tire, each of the lateral grooves having one end being opened to a side of the tire and the other end being communicated with the circumferential groove; and narrow grooves provided in blocks defined by the circumferential grooves and the lateral grooves, each of the narrow grooves having one end being opened to the side of the tire and the other end being communicated with the circumferential groove, in which the tire includes a projecting surface that projects, at a position more to one side or the other side in the circumferential direction of the tire than the narrow groove that is opened to the tire side, further to an outer side in a tire width direction than a tire side shape to which the narrow groove is opened, and in which the projecting surface extends in a tire radial direction from a ground contact end so as to include a groove bottom of the narrow groove. 
     According to this configuration, since the air flowing through the sides of the tire creates a forced air flow in the narrow grooves, it is possible to suppress the rise of the heat generation temperature in the tread portion. 
     As another configuration of the tire, the projecting surface may include: a first projecting surface that extends in the tire radial direction within a range of the groove depth of the narrow groove, and a second projecting surface provided on an inner side in the tire radial direction than the first projecting surface; and the second projecting surface is provided to be displaced in the tire circumferential direction so as to be located on a narrow groove side than the first projecting surface. 
     REFERENCE SIGN LIST 
       3 : Road surface,  12 : Bead core,  14 : Carcass,  16 : Belt,  18 : Chafer,  20 : Bead filler,  22 : Belt under rubber,  24 : Rim cushion rubber,  26 : Side rubber,  28 : Base rubber,  30 : Tread rubber,  32 : Inner rubber,  40 : Circumferential groove,  42 : Circumferential Groove,  44 : Lateral groove,  44   x : Opening groove bottom,  46 : Lateral groove,  48 : Lateral groove,  50 : Shoulder land,  50 A: Shoulder block,  52 : Shoulder land,  52 A: Shoulder block,  54 : Center land,  54 A: Center block,  60 : Narrow groove,  60   b : Groove wall,  60   z : Ggroove bottom,  62 : Narrow groove,  64 : Narrow groove,  70 : Projecting part,  72 : Projecting wall,  73 : First projecting wall,  73 A: End surface (projecting surface),  74 : Second projecting wall,  74 A: End surface (projecting surface),  76 : Connecting surface,  83 : Boundary edge, CL: Tire center, F: Basic shape, L 1 : Distance, L 2 : Distance, L 3 : Distance, L 4 : Distance, ml: Groove wall, n 1 : groove wall, T: Tire, Tm: Ground contact surface, Ts: tire side, Tt: end part, Tw: Tire maximum width.