Patent Publication Number: US-2021170797-A1

Title: Heavy duty tire

Description:
TECHNICAL FIELD 
     The present disclosure relates to a heavy duty tire. 
     BACKGROUND ART 
     Due to their load bearing capability and size, heavy duty tires are liable to experience a rise in temperature in the vicinity of a buttress portion. The buttress portion undergoes repeated distortion as it repeatedly contacts and moves away from the road surface during travel, causing heat to be generated in the buttress portion. Consideration has therefore been given to forming recess portions in such a buttress portion such that air flows into the recess portions and cools the buttress portion. A tire disclosed in Japanese National-Phase Publication 2009-542528 is an example of a tire in which recess portions are formed in a buttress portion. 
     SUMMARY OF INVENTION 
     Technical Problem 
     Forming recess portions in the buttress portion enables the buttress portion to be cooled to a certain extent. However, larger loads result in greater distortion and thus increase the amount of heat generated, and there is therefore demand for improved cooling capability. 
     In consideration of the above circumstances, an object of the present disclosure is to provide a heavy duty tire with improved buttress portion cooling capability. 
     Solution to Problem 
     A heavy duty tire according to the present disclosure includes a recess portion that is formed in a buttress portion and that opens toward a tire outside, and an air entry and exit promotion portions, each of which is linked to a side portion of the recess portion, that is open toward the tire outside, and that includes a slope from a surface of the tire toward a bottom portion of the recess portion. such that a depth dimension from the tire surface gradually increases. An average incline angle of the slope with respect to the tire surface is no greater than 45°, and the air entry and exit promotion portions are disposed at two or more locations. 
     If the average incline angle of the slope with respect to the tire surface were greater than 45°, it would be difficult to redirect air flowing along the tire surface so as to follow the slope. 
     Advantageous Effects of Invention 
     The heavy duty tire of the present disclosure enables the buttress portion cooling capability to be improved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-section illustrating the vicinity of a buttress portion of a heavy duty tire according to an exemplary embodiment. 
         FIG. 2  is a side view illustrating the vicinity of a buttress portion of a heavy duty tire according to an exemplary embodiment. 
         FIG. 3  is a perspective view illustrating the vicinity of a buttress portion of a heavy duty tire according to an exemplary embodiment. 
         FIG. 4  is an enlarged plan view illustrating an air-cooling portion provided to a buttress portion. 
         FIG. 5(A)  is a cross-section of the air-cooling portion illustrated in  FIG. 4  as sectioned along line  5 A- 5 A.  FIG. 5(B)  is a cross-section of the air-cooling portion illustrated in  FIG. 4  as sectioned along line  5 B- 5 B.  FIG. 5(C)  is a cross-section of the air-cooling portion illustrated in  FIG. 4  as sectioned along line  5 C- 5 C. 
         FIG. 6(A)  to  FIG. 6(D)  are plan views schematically illustrating modified examples of air-cooling portions. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Explanation follows regarding a heavy duty tire  10  according to an exemplary embodiment in the present invention, with reference to  FIG. 1  to  FIG. 6 . With the exception of air-cooling portions  32 , described later, the structure of the heavy duty tire  10  of the present exemplary embodiment is configured similarly to a typical heavy duty pneumatic tire. 
     As illustrated in  FIG. 1 , the heavy duty tire  10  includes a carcass  12  that spans between a pair of non-illustrated bead cores. 
     Belt Configuration 
     A belt  14  is laid at a tire radial direction outer side of the carcass  12 . The belt  14  includes plural belt layers. Specifically, the heavy duty tire  10  according to the present exemplary embodiment includes a protective belt layer  16  configured of two protective belts  16 A,  16 B, a main intersecting belt layer  18  configured of two main intersecting belts  18 A,  18 B, and a small intersecting belt layer  20  configured of two small intersecting belts  20 A,  20 B. Note that the protective belts  16 A,  16 B, the main intersecting belts  18 A,  18 B, and the small intersecting belts  20 A,  20 B each have a typical structure in which plural cords arrayed parallel to each other are coated in covering rubber. 
     The main intersecting belt layer  18  is laid at the tire radial direction outer side of the small intersecting belt layer  20 , and the protective belt layer  16  is laid at the tire radial direction outer side of the main intersecting belt layer  18 . 
     As an example, in the heavy duty tire  10  of the present exemplary embodiment, an angle formed by the cords configuring the small intersecting belt layer  20  with respect to a tire circumferential direction is from 4° to 10°, an angle formed by the cords configuring the main intersecting belt layer  18  with respect to the tire circumferential direction is from 18° to 35°, and an angle formed by the cords configuring the protective belt layer  16  with respect to the tire circumferential direction is from 22° to 33°. 
     Explanation follows regarding widths of the respective belt layers making up the belt  14  of the present exemplary embodiment. 
     The width of the small intersecting belt  20 A that is at the tire radial direction outer side of and adjacent to the small intersecting belt  20 B located at the tire radial direction innermost side is formed slightly narrower than the width of the small intersecting belt  20 B. 
     The width of the main intersecting belt  18 B that is at the tire radial direction outer side of and adjacent to the small intersecting belt  20 A is formed wider than the widths of each of the small intersecting belts  20 A,  20 B. 
     The width of the main intersecting belt  18 A that is at the tire radial direction outer side of and adjacent to the main intersecting belt  18 B is formed wider than the widths of each of the small intersecting belts  20 A,  20 B, but narrower than the width of the main intersecting belt  18 B. 
     The width of the protective belt  16 B that is at the tire radial direction outer side of and adjacent to the main intersecting belt  18 A is formed wider than the widths of each of the small intersecting belts  20 A,  20 B and the main intersecting belts  18 A,  18 B. 
     The width of the protective belt  16 A that is at the tire radial direction outer side of and adjacent to the protective belt  16 B and positioned at the outermost side of the belt  14  is formed narrower than the widths of each of the protective belt  16 B and the main intersecting belt  18 B, but wider than the respective widths of the small intersecting belts  20 A,  20 B and the main intersecting belt  18 A. Note that the protective belt  16 A is an example of an outermost belt ply in the tire radial direction. 
     The protective belt  16 B that configures the fifth belt as counted from the radial direction inner side is formed with the maximum width in the belt  14 . The protective belt  16 B is an example of a maximum width belt ply. 
     Tread rubber  24  configuring a tread  22  is laid at the tire radial direction outer side of the belt  14 . The tread rubber  24  extends along the carcass  12  to tire width direction outer sides of the belt  14 , and parts of the tread rubber  24  laid at the tire width direction outer sides of the belt  14  each configure part of a buttress portion  26 . 
     The buttress portion  26  of the present exemplary embodiment refers to a tire outside region spanning from a position located ½×H from a tire maximum width portion Wmax to a ground contact edge  22 E, H being a tire radial direction dimension between the tire maximum width portion Wmax and the ground contact edge  22 E of the tread  22 . 
     The ground contact edge  22 E of the tread  22  assumes conditions under which the heavy duty tire  10  is fitted to a standard rim as specified in the 2017 Japanese Automobile Tyre Manufacturers Association (JATMA) Year Book, and is filled to an air pressure of 100% internal pressure (maximum pressure) corresponding to the maximum load capacity (the load given in bold in the internal pressure/load capacity correspondence table) for the applicable size and ply rating specified in the JATMA Year Book, such that heavy duty tire  10  is at its maximum load bearing capacity. Note that in cases in which TRA or ETRTO standards apply in the region of use or manufacture, the applicable standards are followed. 
     Plural lug grooves  28  are formed in the tread  22  of the heavy duty tire  10  around the tire circumferential direction. The lug grooves  28  formed in the tread  22  extend further toward the tire width direction outer sides than the ground contact edges  22 E of the tread  22 . As illustrated in  FIG. 2 , end portions of the lug grooves  28  open onto the buttress portions  26  of the heavy duty tire  10 . Note that in the present exemplary embodiment, land portions formed between lug grooves  28  that are adjacent in the tire circumferential direction are referred to as lug blocks  30 . 
     As illustrated in  FIG. 1  to  FIG. 3 , the concave air-cooling portions  32  are formed in the buttress portions  26 . In the present exemplary embodiment, the air-cooling portions  32  are formed to side faces of the respective lug blocks  30  partitioned by the lug grooves  28  (to the buttress portion  26 ). 
     Detailed Configuration of Air-Cooling Portion 
     As illustrated in  FIG. 4 , each of the air-cooling portions  32  is configured including a recess portion  34 , a first air entry and exit promotion portion  36  serving as an example of an air entry and exit promotion portion, and a second air entry and exit promotion portion  38 . Each of the air entry and exit promotion portions is a location linked to a side portion of the recess portion  34  so as to be open toward the tire outside, and has a depth dimension from the tire surface that gradually increases on progression from the tire surface of the buttress portion  26  toward a bottom portion  40  of the recess portion  34 . When viewed in plan view, a combined surface area of slopes  46 ,  52  is greater than a surface area of the bottom portion  40  of the recess portion  34 . 
     Detailed Configuration of Recess Portion 
     First, explanation follows regarding the recess portion  34 . As illustrated in  FIG. 1  to  FIG. 3 , the recess portions  34  are formed to the buttress portions  26  so as to open toward the tire outside. As illustrated in  FIG. 4 , in plan view the recess portion  34  includes the bottom portion  40  that has a trapezoidal shape in which a bottom side  40 A at the tire radial direction outer side (arrow A direction side) has a greater width than an upper side  40 B at the tire radial direction inner side. Note that the bottom side  40 A and the upper side  40 B are parallel to a direction tangential to the tire circumferential direction (arrow B direction), and a side  40 C of the bottom portion  40  at a tire rotation direction front (arrow B direction) side and a side  40 D of the bottom portion  40  on the opposite side to the tire rotation direction front side are inclined with respect to the tire radial direction (arrow A direction). 
     Note that although the bottom portion  40  is trapezoidal shaped in the present exemplary embodiment, the bottom portion  40  may be another polygonal shape such as a square, rectangular, or triangular shape, or may be circular or elliptical in shape. 
     Although the depth of the bottom portion  40  is uniform along the direction toward the tire rotation direction front (arrow B direction) as illustrated in  FIG. 5(A) , the bottom portion  40  is inclined such that its depth gradually becomes shallower on progression from the tire radial direction inner side toward the tire radial direction outer side (arrow A direction side) as illustrated in  FIG. 5(B) . Note that the bottom portion  40  may also be inclined with respect to a direction running along the tire rotation direction (arrow B direction). Alternatively, the bottom portion  40  may have a uniform depth in a direction running along the tire radial direction (arrow A). 
     As illustrated in  FIG. 1 , in the recess portion  34  of the present exemplary embodiment, the bottom portion  40  is disposed at the tire width direction outer side of a tire width direction end portion  16 Be of the protective belt  16 B, this being formed with the maximum width in the belt  14 . In the present exemplary embodiment, the tire width direction end portion  16 Be of the protective belt  16 B is positioned at the tire width direction inner side of a tire radial direction center portion of the recess portion  34 . More specifically, the tire width direction end portion  16 Be is disposed between the bottom side  40 A and the upper side  40 B of the bottom portion  40  (see  FIG. 4 ) so as to be closer to the upper side  40 B. 
     As illustrated in  FIG. 4 , a recess sidewall  42  configuring part of the recess portion  34  is formed on the opposite side of the bottom portion  40  to the tire rotation direction front (arrow B direction) side. A recess sidewall  44  configuring another part of the recess portion  34  is formed at the tire radial direction inner side of the bottom portion  40  (on the opposite side to the arrow A direction). 
     As illustrated in  FIG. 5(A) , the recess sidewall  42  is inclined with respect to a normal line HL that runs perpendicular to the surface of the buttress portion  26 . A theoretical recess sidewall  43  is inclined at the same angle but in the opposite direction to the recess sidewall  42  on the tire rotation direction front (arrow B direction) side of the bottom portion  40 . As illustrated in  FIG. 5(B) , the recess sidewall  44  is also inclined with respect to a normal line HL that runs perpendicular to the surface of the buttress portion  26 . A theoretical recess sidewall  45  is inclined at the same angle but in the opposite direction to the recess sidewall  44  at the tire radial direction outer (arrow A direction) side of the bottom portion  40 . In such a configuration, the recess portion  34  would be formed so as to widen on progression from the bottom portion  40  toward the tire outside. 
     First Air Entry and Exit Promotion Portion 
     Next, explanation follows regarding the first air entry and exit promotion portion  36 . 
     As illustrated in  FIG. 4  and  FIG. 5(A) , the first air entry and exit promotion portion  36  is disposed at the tire rotation direction front (arrow B direction) side of the recess portion  34 . The first air entry and exit promotion portion  36  has a trapezoidal shape in plan view, and is a concave portion including the slope  46  that is inclined from the surface of the buttress portion  26  at the tire rotation direction front side (arrow B direction side) toward the bottom portion  40  of the recess portion  34 . Note that the slope  46  connects smoothly to the bottom portion  40 . 
     Note that although in the present exemplary embodiment an example is given in which the slope  46  has a trapezoidal shape in plan view, the slope  46  may be formed with another polygonal shape in plan view, depending on the inclination direction of the bottom portion  40  (the extension direction of the side  40 C), and the surface profile of the buttress portion  26 . 
     A sidewall  48  that has a steeper incline that the slope  46  is formed at the tire radial direction outer side (arrow A direction side) of the slope  46 , and a sidewall  50  that has a steeper incline than the slope  46  is formed at the tire radial direction inner side of the slope  46 . The angle formed by the sidewall  48  with respect to the slope  46  is greater than the angle formed by the sidewall  50  with respect to the slope  46 . 
     A shortest distance along the slope  46  from the side  40 C to the surface of the buttress portion  26  is longer than a shortest distance along the recess sidewall  42  from the side  40 D to the surface of the buttress portion  26 . 
     As illustrated in  FIG. 4 , the width of the first air entry and exit promotion portion  36  in the tire radial direction gradually increases on progression from the tire rotation direction front side toward the recess portion  34 . In other words, W 3 &gt;W 1  when W 1  is the width of a tire rotation direction front side end portion of the first air entry and exit promotion portion  36 , and W 3  is the width of the first air entry and exit promotion portion  36  on the recess portion  34  side (the width of a portion connected to the recess portion  34  as measured along the tire radial direction). The width of the slope  46  is uniform, whereas the widths of the sidewalls  48 ,  50  gradually increase on progression from the tire rotation direction front side toward the recess portion  34 . Note that the width of the first air entry and exit promotion portion  36  may be uniform on progression from the tire rotation direction front side toward the recess portion  34 . 
     Furthermore, in the present exemplary embodiment, the width W 3  of the first air entry and exit promotion portion  36  on the recess portion  34  side as measured at the tire surface is set so as to be the same as a (tire radial direction) width W 2  of the recess portion  34  at the tire surface. Note that the double-dotted dashed lines (imaginary lines) in  FIG. 4  indicate the extent of the opening of the recess portion  34  were the first air entry and exit promotion portion  36  and the second air entry and exit promotion portion  38  not formed thereto. 
     As illustrated in  FIG. 5(A)  and  FIG. 5(B) , the slope  46  has a gentler incline than the recess sidewall  42  and the recess sidewall  44  of the recess portion  34 . An average incline angle θ 1  of the slope  46  with respect to the surface of the buttress portion  26  is no greater than 45°. If the average incline angle θ 1  were greater than 45°, it would be difficult to redirect air flowing along the tire surface so as to follow the slope  46 . Note that the average incline angle θ 1  may be within a range of from 5° to 30°. If the average incline angle θ 1  were smaller than 5°, the cooling effect would be diminished. Note that the average incline angle θ 1  may be within a range of from 15° to 25°. 
     Note that in cross-section the slope  46  forms a straight line running from the side  40 C to the surface of the buttress portion  26 . Due to forming a straight line in this manner, the slope  46  has a uniform incline angle, such that air inflow and outflow directions can be easily made to follow the slope  46 . 
     Second Air Entry and Exit Promotion Portion 
     Next, explanation follows regarding the second air entry and exit promotion portion  38 . 
     As illustrated in  FIG. 4 , the second air entry and exit promotion portion  38  is disposed on the tire radial direction outer (arrow A direction) side of the recess portion  34 . As illustrated in  FIG. 5(B) , in cross-section the second air entry and exit promotion portion  38  is a concave portion including the slope  52  that is inclined from the surface of the buttress portion  26  toward the bottom portion  40  of the recess portion  34 . The slope  52  has a substantially square shape in plan view. The slope  52  connects smoothly to the bottom portion  40 . 
     Note that although the slope  52  has a substantially square shape in the present exemplary embodiment, the slope  52  may have another polygonal shape such as a rectangular or trapezoidal shape. 
     As illustrated in  FIG. 4 , a sidewall  54  that has a steeper incline that the slope  52  is formed at the tire rotation direction front side (arrow B direction side) of the slope  52 , and a sidewall  56  that has a steeper incline than the slope  52  is formed at the tire rotation direction rear side of the slope  52 . The angles formed by the sidewalls  54 ,  56  with respect to the slope  52  are substantially the same as one another. In the second air entry and exit promotion portion  38  of the present exemplary embodiment, the width dimension (the dimension in a direction intersecting the incline direction of the slope  52 ) at the tire radial direction outer side is formed relatively smaller than the width dimension at the recess portion  34  side. A shortest distance along the slope  52  from the bottom side  40 A to the surface of the buttress portion  26  is longer than a shortest distance along the recess sidewall  44  from the upper side  40 B to the surface of the buttress portion  26 . 
     Note that the width of the slope  52  is uniform from the bottom portion  40  of the recess portion  34  toward the tire radial direction outer side. 
     Note that end portions of the sidewall  54  of the second air entry and exit promotion portion  38  and the sidewall  48  of the first air entry and exit promotion portion  36  previously described are connected to one another. Moreover, end portions of the sidewall  50  of the first air entry and exit promotion portion  36  and the recess sidewall  44  of the recess portion  34  are also connected to one another. 
     The slope  52  has a gentler incline than the recess sidewall  42  and the recess sidewall  44  of the recess portion  34 . As illustrated in  FIG. 5(B) , similarly to the average incline angle θ 1  of the slope  46  of the first air entry and exit promotion portion  36 , an average incline angle θ 2  of the slope  52  with respect to the surface of the buttress portion  26  is no greater than 45°. If the average incline angle θ 2  were greater than 45°, it would be difficult to redirect air flowing along the tire surface so as to follow the slope  46 . Note that the average incline angle θ 2  may be within a range of from 5° to 30°. If the average incline angle θ 2  were smaller than 5°, the cooling effect would be diminished. The average incline angle θ 2  may be within a range of from 15° to 25°. 
     Note that in cross-section the slope  52  forms a straight line running from the bottom side  40 A to the surface of the buttress portion  26 . Due to forming a straight line in this manner, the slope  52  has a uniform incline angle, such that air inflow and outflow directions can be easily made to follow the slope  52 . 
     As illustrated in  FIG. 5(A)  and  FIG. 5(B) , the average incline angle θ 1  of the slope  46  and the average incline angle θ 2  of the slope  52  are both smaller than an average incline angle θ 3  of the recess sidewall  42  and an average incline angle θ 4  of the recess sidewall  44  of the recess portion  34 . In other words, the average incline angles θ 3 ,  04  are both greater than the incline angles of the slopes  46 ,  52 . The average incline angles θ 3 ,  04  are preferably both greater than 40°. 
     Note that in cross-section, the recess sidewall  44  and the recess sidewall  42  each have a rounded profile at a boundary with the surface of the buttress portion  26 . This enables distortion of the buttress portion  26  under load to be suppressed. 
     Note that  FIG. 5(C)  is a cross-section of the air-cooling portion illustrated in  FIG. 4  as sectioned along line  5 C- 5 C. 
     As illustrated in  FIG. 4 , in the air-cooling portion  32  of the present exemplary embodiment, an end portion on the recess portion  34  side of the slope  46  of the first air entry and exit promotion portion  36  is linked to the entire side  40 C at the tire rotation direction front side of the bottom portion  40  of the recess portion  34 . Moreover, an end portion on the recess portion  34  side of the slope  52  of the second air entry and exit promotion portion  38  is linked to the entire bottom side  40 A at the tire rotation direction front side of the bottom portion  40  of the recess portion  34 . 
     Operation and Advantageous Effects 
     Explanation follows regarding operation and advantageous effects of the heavy duty tire  10  of the present exemplary embodiment. 
     As the heavy duty tire  10  rotates while traveling, the tread  22  repeatedly contacts and moves away from the road surface. The tread  22  therefore undergoes repeated distortion, thereby generating a large amount of heat, particularly at the buttress portion  26 . 
     Moreover, as the heavy duty tire  10  rotates while traveling, a difference in speed arises between the tire surface and the surrounding air, causing air to flow into the recess portions  34  of the air-cooling portions  32  formed to the buttress portions  26 . Specifically, as illustrated by the arrow C in  FIG. 3 , air at the tire rotation direction front side of the air-cooling portion  32  flows into the recess portion  34  through the first air entry and exit promotion portion  36  on the tire rotation direction front side. The air that has flowed into the recess portion  34  then flows along the bottom portion  40  of the recess portion  34  so as to cool the bottom portion  40  of the recess portion  34 . 
     The average incline angle θ 1  of the slope  46  of the first air entry and exit promotion portion  36  with respect to the tire surface is no greater than 45°, and the slope  46  connects to the bottom portion  40  of the recess portion  34  at a gentler incline than the recess sidewall  42  and the recess sidewall  44  of the recess portion  34 . This enables air at the tire rotation direction front side of the recess portion  34  to be smoothly directed along the slope  46  and into the recess portion  34 . Moreover, the air that has flowed into the recess portion  34  flows along the bottom portion  40  of the recess portion  34 , enabling the bottom portion  40  to be effectively cooled. Namely, the air-cooling portion  32  including the first air entry and exit promotion portion  36  promotes the inflow of air toward the recess portion  34  compared to cases in which the first air entry and exit promotion portion  36  is not present, enabling the buttress portion  26  to be more effectively cooled. 
     The air flowing along the bottom portion  40  is then dispelled to the tire exterior along the slope  52  of the second air entry and exit promotion portion  38  disposed at the tire radial direction outer side of the recess portion  34 , thereby enabling air that has flowed in from the tire rotation direction front side to be dispelled to the tire outside in turn. Thus, the air-cooling portion  32  promotes the inflow of air into the recess portion  34  compared to cases in which the second air entry and exit promotion portion  38  is not present, enabling the buttress portion  26  to be more effectively cooled. 
     In this manner, the air entry and exit promotion portions, namely the first air entry and exit promotion portion  36  and the second air entry and exit promotion portion  38 , are disposed at two locations in the present exemplary embodiment, thereby enabling openings for air to enter and exit the recess portion  34  to be secured, and thus enabling airflow to be improved. 
     Furthermore, when the second air entry and exit promotion portion  38  at the tire radial direction outer side of the recess portion  34  is positioned at the front side of the recess portion  34  in the direction of progress of the tire, inflow of air traveling toward the rear in the direction of progress of the tire (translational airflow) through this second air entry and exit promotion portion  38  and toward the bottom portion  40  of the recess portion  34  can be promoted. 
     Note that if the average incline angle θ 1  of the slope  46  of the first air entry and exit promotion portion  36  were greater than 45°, it would be difficult to redirect the air flowing along the tire surface so as to follow the slope  46 . If the average incline angle θ 1  of the slope  46  of the first air entry and exit promotion portion  36  were smaller than 5°, the cooling effect of the recess portion  34  would be diminished. Similar applies to the average incline angle θ 2  of the slope  52  of the second air entry and exit promotion portion  38 . 
     As illustrated in  FIG. 4 , in the air-cooling portion  32  of the present exemplary embodiment, the recess portion  34  side end portion of the slope  46  of the first air entry and exit promotion portion  36  is linked to the entire side  40 C at the tire rotation direction front side of the bottom portion  40  of the recess portion  34 . Moreover, the recess portion  34  side end portion of the slope  52  of the second air entry and exit promotion portion  38  is linked to the entire side  40 A at the tire rotation direction front side of the bottom portion  40  of the recess portion  34 . Thus, air flowing in through the first air entry and exit promotion portion  36  can be made to flow in across the entire width of the bottom portion  40  of the recess portion  34  and flow out through the second air entry and exit promotion portion  38 , enabling the bottom portion  40  to be effectively cooled. Air can be also be made to efficiently flow in through the second air entry and exit promotion portion  38 . 
     As the heavy duty tire  10  rotates, the temperature of the tread  22  is liable to rise in the vicinity of the belt  14  where the width of the belt  14  is at its maximum, namely, in the vicinity of the tire width direction end portion  16 Be of the protective belt  16 B where the width of the belt  14  configuration is at its maximum. 
     In the present exemplary embodiment, the bottom portion  40  of the recess portion  34  of the air-cooling portion  32  is disposed at the tire width direction outer side of the tire width direction end portion  16 Be of the protective belt  16 B, and is positioned near to the tire width direction end portion  16 Be of the protective belt  16 B where the temperature is most liable to rise. This enables heat generated near to the tire width direction end portion  16 Be of the protective belt  16 B to be effectively dissipated to the tire exterior through the bottom portion  40  of the recess portion  34 , enabling the rise in temperature near to the tire width direction end portion  16 Be of the maximum width protective belt  16 B to be effectively suppressed. 
     Moreover, in the heavy duty tire  10  of the present exemplary embodiment, the tire width direction end portion  16 Be of the protective belt  16 B is positioned at the tire width direction inner side of the tire radial direction center portion of the bottom portion  40  of the recess portion  34 , thereby enabling a tire radial direction inner side portion and tire radial direction outer side portion of the tire width direction end portion  16 Be to be evenly cooled. 
     Other Exemplary Embodiments 
     An exemplary embodiment in the present invention has been described above. However, the present disclosure is not limited to the above description, and obviously various other modifications may be implemented within a range not departing from the spirit of the present disclosure. 
     In the above exemplary embodiment, the first air entry and exit promotion portion  36  is disposed at the tire rotation direction front side of the recess portion  34  and the second air entry and exit promotion portion  38  is disposed at the tire radial direction outer side of the recess portion  34  as examples of air entry and exit promotion portions in two or more locations. However, the placement and number of air entry and exit promotion portions are not limited thereto. 
     Explanation follows regarding modified examples in which positional relationships and so on of the air entry and exit promotion portions and the recess portion  34  have been modified.  FIG. 6  are plan views schematically illustrating modified examples of the air-cooling portion  32 , in which only the bottom portion of the recess portion  34  and the slopes of the air entry and exit promotion portions are illustrated. 
     In the example illustrated in  FIG. 6(A) , air entry and exit promotion portions (the first air entry and exit promotion portion  36  and a third air entry and exit promotion portion  66 ) are disposed at two locations at the two tire circumferential direction sides of the recess portion  34 . 
     In the example illustrated in  FIG. 6(B) , in addition to the configuration of  FIG. 6(A)  a fourth air entry and exit promotion portion  76  is formed at the tire radial direction inner side of the recess portion  34 . Namely, air entry and exit promotion portions are formed at three locations in this example. 
     In the example illustrated in  FIG. 6(C) , the second air entry and exit promotion portion  38  is formed in addition to the configuration of  FIG. 6(B) . Namely, air entry and exit promotion portions are formed at four locations in this example. 
     In the example illustrated in  FIG. 6(D) , the first air entry and exit promotion portion  36  and the third air entry and exit promotion portion  66  are disposed at two locations at the two tire circumferential direction sides of the recess portion  34 . The tire radial direction widths of the first air entry and exit promotion portion  36  and the third air entry and exit promotion portion  66  gradually increase on progression away from the recess portion  34 . 
     Although the tire width direction end portion  16 Be of the belt ply (the protective belt  16 B) where the width of the belt configuration is at its maximum is positioned at the tire width direction inner side of the bottom portion  40  of the recess portion  34 , the tire width direction end portion  16 Be may be disposed at a position that is displaced slightly from the tire width direction inner side of the bottom portion  40  of the recess portion  34 . 
     Although the bottom portion  40  of the recess portion  34  is not positioned at the tire width direction outer side of a tire width direction end  16 Ae of the protective belt  16 A disposed at the tire radial direction outermost side of the belt  14  in the illustrated example, the bottom portion  40  may be extended toward the tire radial direction outer side such that the bottom portion  40  of the recess portion  34  is positioned at the tire width direction outer side of the tire width direction end  16 Ae of the protective belt  16 A at the outermost side. 
     Cracks may develop at the surface of the tread  22  when the heavy duty tire  10  travels along rough roads or the like. When heat is generated such that the temperature rises in the vicinity of the tire width direction end  16 Ae of the protective belt  16 A at the tire radial direction outermost side, the durability of the tread rubber  24  surrounding the vicinity of the tire width direction end  16 Ae is reduced, and cracks that have developed on the surface of the tread  22  might advance toward the rubber portion where the durability is reduced. 
     Disposing the bottom portion  40  of the recess portion  34  at the tire width direction outer side of the tire width direction end  16 Ae of the protective belt  16 A at the tire radial direction outermost side enables the bottom portion  40  to be brought closer to the tire width direction end  16 Ae. This enables the rise in temperature near to the tire width direction end  16 Ae to be suppressed, enabling the durability of the tread rubber  24  near to the tire width direction end  16 Ae to be maintained, and enabling cracks at the surface of the tread  22  to be suppressed from advancing toward the tread rubber  24  near to the tire width direction end  16 Ae. 
     Although when viewed in plan view the combined surface area of the slopes  46 ,  52  is greater than the surface area of the bottom portion  40  of the recess portion  34  in the above exemplary embodiment, this combined surface area may be equal to or less than the surface area of the bottom portion  40  of the recess portion  34 . 
     Although the end portion of the first air entry and exit promotion portion  36  on the opposite side to the recess portion  34  side terminates at the tire surface of the buttress portion  26  in the above exemplary embodiment, the end portion of the first air entry and exit promotion portion  36  on the opposite side to the recess portion  34  side may be linked to (open onto) a lug groove  28  (not illustrated in the drawings). This enables air in the lug groove  28  to be made to flow into the recess portion  34  in addition to air from the tire side face. Although the end portion of the second air entry and exit promotion portion  38  on the opposite side to the recess portion  34  side terminates at the tire surface of the buttress portion  26  in the above exemplary embodiment, the end portion of the second air entry and exit promotion portion  38  on the opposite side to the recess portion  34  side may be linked to (open onto) a lug groove  28  or a tread end (not illustrated in the drawings). 
     The entire content of the disclosure of Japanese Patent Application No. 2017-237700 filed on Dec. 12, 2017 is incorporated by reference in the present specification. 
     All cited documents, patent applications, and technical standards mentioned in the present specification are incorporated by reference in the present specification to the same extent as if each individual cited document, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.