Patent Publication Number: US-2023147644-A1

Title: Pneumatic tire

Description:
RELATED APPLICATIONS 
     This application claims the benefit of foreign priority to Japanese Patent Application No. JP2021-178905. filed Nov. 1, 2021, which is incorporated by reference in its entirety. 
     Field of the Disclosure 
     The present disclosure relates to a pneumatic tire. 
     BACKGROUND OF THE DISCLOSURE 
     Patent Document 1 below discloses a pneumatic tire with a tread portion having a plurality of blocks which is divided by a main groove arranged in the shoulder region of the tread portion and lug grooves reaching the sidewall portion from the main groove. A raised portion formed so as to protrude into one of the lug grooves is provided on the outer side of each block in the tire width direction. 
     Patent Document 
     [Patent document 1] Japanese Patent 6065033 
     SUMMARY OF THE DISCLOSURE 
     In recent years, it has been required to improve the visibility of protectors and improve the appearance performance of the pneumatic tire while maintaining the traction performance on rough terrain such as muddy road surfaces. 
      The present disclosure has been made in view of the above circumstances and has a major object to provide a pneumatic tire capable of improving appearance performance while maintaining traction performance. 
     In one aspect of the present disclosure, a pneumatic tire includes a tread portion having a first tread edge, and a first buttress portion extending inwardly in a tire radial direction from the first tread edge. The first buttress portion is provided with a plurality of protectors protruding outwardly in a tire axial direction. Each of the plurality of protectors includes a top surface facing outwardly in the tire axial direction, and a side surface extending inwardly in the tire axial direction from an edge of the top surface. The side surface includes an outward-facing portion facing outwardly in the tire radial direction, an inward-facing portion facing inwardly in the tire radial direction, and a circumferential portion facing in a tire circumferential direction. The outward-facing portion, the inward-facing portion and the circumferential portion have different angles with respect to respective normal lines of the top surface from each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a tire meridian cross-sectional view illustrating an embodiment of a pneumatic tire according to the present disclosure; 
         FIG.  2    is a perspective view of a first buttress portion; 
         FIG.  3    is a front view of the first buttress portion; 
         FIG.  4 A  is a cross-sectional view taken along the line A-A of  FIG.  3   ; 
         FIG.  4 B  is a cross-sectional view taken along the line B-B of  FIG.  3   ; 
         FIG.  4 C  is a cross-sectional view taken along the line C-C of  FIG.  3   ; 
         FIG.  5    is a front view of the first buttress portion; 
         FIG.  6    is a front view of the first buttress portion; 
         FIG.  7    is a front view of the first buttress portion; 
         FIG.  8    is a front view of the first buttress portion according to another embodiment; 
         FIG.  9 A  is a front view of the first buttress portion according to yet another embodiment: and 
         FIG.  9 B  is a cross-sectional view taken along the line D-D of  FIG.  9 A . 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     Hereinafter, one or more embodiments of the present disclosure will be described with reference to the drawings. 
       FIG.  1    is a tire meridian cross-sectional view including the tire axis illustrating an embodiment of a pneumatic tire (hereafter, may be simply referred to as “tire”)  1  under a normal state.  FIG.  1    illustrates, as a preferred embodiment, a pneumatic tire to be mounted on 4WD vehicles or the like that enable driving on rough terrain. Alternatively, the present disclosure can be applied to tires  1  including those for light trucks and heavy loads. 
     As used herein, the “normal state” is such that the tire  1  is mounted onto a standard wheel rim (not illustrated) with a standard pressure but loaded with no tire load. As used herein, unless otherwise noted, dimensions of portions of the tire  1  are values measured under the normal state. 
     As used herein, the “standard wheel rim” is a wheel rim officially approved for each tire by standards organizations on which the tire is based, wherein the standard wheel rim is the “standard rim” specified in JATMA, the “Design Rim” in TRA, and the “Measuring Rim” in ETRTO, for example. 
     As used herein, the “standard pressure” is a standard pressure officially approved for each tire by standards organizations on which the tire is based, wherein the standard pressure is the “maximum air pressure” in JATMA, the maximum pressure given in the “Tire Load Limits at Various Cold Inflation Pressures” table in TRA, and the “Inflation Pressure” in ETRTO, for example. 
     In the present embodiment, the tire  1  includes some tire components such as a carcass  6 . a belt layer and the like. Known members are appropriately adopted for these tire components. 
     In the present embodiment, the tire  1  includes a tread portion  2  having a first tread edge To, and a first buttress portion  4 A extending inwardly in the tire radial direction from the first tread edge To. Further, the tire  1 , for example, includes a second tread edge Ti and a second buttress portion  4 B extending inwardly in the tire radial direction from the second tread edge Ti. In the present embodiment, the second buttress portion  4 B is formed in the same manner as the first buttress portion  4 A, so the explanation thereof is omitted herein. Alternatively, the second buttress portion  4 B may be formed in a different manner from the first buttress portion  4 A. 
     The first tread edge To and the second tread edge Ti are the axial outermost edges of the ground contacting patch of the tire  1  which occurs under the condition such that the tire  1  under the normal state is grounded on a plane with a standard tire load at zero camber angles. The tread portion  2  is formed between the first tread edge To and the second tread edge Ti. The distance in the tire axial direction between the first tread edge To and the second tread edge Ti is the tread width TW. 
     As used herein, the “standard tire load” is a tire load officially approved for each tire by the standards organization in which the tire is based, wherein the standard tire load is the “maximum load capacity” in JATMA, the maximum value given in the above-mentioned table in TRA, and the “Load Capacity” in ETRTO, for example. 
       FIG.  2    is a perspective view of the first buttress portion  4 A. As illustrated in  FIG.  2   , the first buttress portion  4 A according to the present embodiment is provided with a plurality of protectors  10  protruding outwardly in the tire axial direction. The protectors  10  can enhance traction performance by coming into contact with muddy road surface and the like. 
       FIG.  3    is a front view of the first buttress portion  4 A As illustrated in  FIG.  2    and  FIG.  3   , each protector  10  includes a top surface  11  facing outwardly in the tire axial direction and a side surface  12  extending inwardly in the tire axial direction from an edge  13  of the top surface  11 . The side surface  12 , for example, protrudes from an outer surface  4   s  of the first buttress portion  4 A. As used herein, the outer surface  4   s  means a surface that extends smoothly on the first buttress portion  4 A excluding localized unevenness including embossed marks such as marks and uneven patterns in the normal state. 
     The side surface  12  includes an outward-facing portion  15  facing outwardly in the tire radial direction, an inward-facing portion  16  facing inwardly in the tire radial direction, and a circumferential portion  17  facing in the tire circumferential direction. Note that the shape of protector  10  in a front view of the first buttress portion  4 A is not limited to the shape shown in the figure, but various shapes can be adopted. 
       FIG.  4 A  is a cross-sectional view taken along the line A-A of  FIG.  3   .  FIG.  4 A  shows a cross section of the outward-facing portion  15  in a direction orthogonal to a longitudinal direction of the outward-facing portion  15 .  FIG.  4 B  is a cross-sectional view taken along the line B-B of  FIG.  3   .  FIG.  4 B  shows a cross section of the inward-facing portion  16  in a direction orthogonal to the longitudinal direction of the inward-facing portion  16 .  FIG.  4 C  is a cross-sectional view taken along the line C-C of  FIG.  3   .  FIG.  4 C  shows a cross section of the circumferential portion  17  in a direction orthogonal to the longitudinal direction of the circumferential portion  17 . As illustrated in  FIGS.  4 A to  4 C , the outward-facing portion  15 , the inward-facing portion  16  and the circumferential portion  17  have different angles with respect to respective normal lines n of the top surface  11  from each other. Note that the normal lines n pass through the edges  13  in the respective cross-sectional views. As a result, protruding heights of the outward-facing portion  15 , the inward-facing portion  16  and the circumferential portion  17  appear to be different from each other. Thus, the visibility of each protector  10  can be improved and the appearance performance can be improved. The outward-facing portion  15  is located outside than the inward-facing portion  16  in the tire radial direction, for example. 
     The outward-facing portion  15 , for example, is inclined inwardly in the tire radial direction toward the outside in the tire axial direction. The inward-facing portion  16 , for example, is inclined outwardly in the tire radial direction toward the tire outside in the tire axial direction. The circumferential portion  17 , for example, is inclined in a direction close to the center of the top surface  11  in the tire circumferential direction toward the outside in the tire axial direction. In other words, the side surface  12  is inclined outwardly of the top surface  11  toward the inside in the tire axial direction. 
       FIG.  5    illustrates a front view of the first buttress portion  4 A. As illustrated in  FIG.  5   , the outward-facing portion  15 , the inward-facing portion  16  and the circumferential portion  17  are defined as follows. The outward-facing portion  15  is a portion of the side surface  12  facing outward in the tire radial direction. The outward-facing portion has a straightly extending edge  13   a  of the edge  13  where the angle α1 between the tire radial line N 1  passing on a virtual straight line X 1  connecting longitudinal ends  13   e  and  13   e  of the straightly extending edge  13   a  and the virtual straightly extending line X 1  is greater than 45 degrees. The inward-facing portion  16  is a portion of the side surface  12  facing inward in the tire radial direction. The inward-facing portion  16  has an edge with the above-mentioned angle α1 with respect to the tire radial line N 1  greater than 45 degrees. The circumferential portion  17  is a portion of the side surface  12  facing the tire circumferential direction. The circumferential portion  17   has an edge with the angle α1 with respect to the tire radial line N 1  equal to or less than 45 degrees. The angle α1 means the angle of 90 degrees or less of the two divided angles.  FIG.  5    shows the outward-facing portion  15  and the circumferential portion  17  as an example. 
     As illustrated in  FIGS.  4 B and  4 C , an angle θi of the inward-facing portion  16  with respect to the normal lines n is preferably smaller than an angle θc of the circumferential portion  17  with respect to the normal line n. As illustrated in  FIG.  3   , in a view where the inward-facing portion  16  is vertically downward, the inward-facing portion  16  is a region where the irradiation of light is relatively small. Thus, by making the angle θi of the inward-facing portion  16  smaller than the angle θc of the inward portion  17 . the shadow of the inward-facing portion  16  can become large . As a result, the difference in the apparent protruding height between the inward-facing portion  16  and the substantially portion  17  becomes clear, and the appearance performance can be improved. In addition, since the angle θc of the circumferential portion  17  is larger than the angle θi of the inward-facing portion  16 , the rigidity of the circumferential portion  17 , which receives a large pressure when traveling in muddy ground, can be enhanced, and traction performance and cut resistance can be improved. 
     When the angle θc of the circumferential portion  17  becomes excessively larger than the angle θi of the inward-facing portion  16 , the circumferential shear force of the circumferential portion  17  on the mud may be reduced. In addition, the angle θi of the inward-facing portion  16  becomes excessively small, and the tire mass variation over the tire radial direction of the inward-facing portion  16  becomes large. Thus, the uniformity of the tire may deteriorate and the performance related to noise and vibration (hereinafter referred to as “NV performance”) may decrease. When the difference (θc - θi) between the angle θc of the circumferential portion  17  and the angle θi of the inward-facing portion  16  becomes excessively small, the difference between the apparent protruding heights of the two portions may become small and the appearance performance may deteriorate. From this point of view, the difference (θc - θi) between the angle θc of the circumferential portion  17  and the angle θi of the inward-facing portion  16  is preferably equal to or more than 10 degrees, more preferably equal to or more than 15 degrees, but preferably equal to or less than 25 degrees, more preferably equal to or less than 20 degrees. 
     The angle θc of the circumferential portion  17  is preferably smaller than the angle θo of the outward-facing portion  15  with respect to the normal line n. This can increase the shear force of the circumferential portion  17  against the mud. As illustrated in  FIG.  3   , in a view where the outward-facing portion  15  is vertically upward, the outward-facing portion  15  is the region where the light irradiation is relatively large. Thus, by making the angle θo of the outward-facing portion  15  larger than the angle θc of the circumferential portion  17 , the reflection of light at the outward-facing portion  15  becomes larger. Therefore, the outward-facing portion  15  becomes more distinct from the circumferential portion  17  and the inward-facing portion  16  in terms of the apparent protruding height, which can improve the appearance performance. When the angle θo of the outward-facing portion  15  becomes excessively larger than the angle θc of the circumferential portion  17 . the vertical shear force of the outward-facing portion  15  may be smaller and the traction performance may decrease. In order to effectively demonstrate such an effect, the difference (θo - θc) between the angle θo of the outward-facing portion  15  and the angle θc of the circumferential portion  17  is preferably equal to or more than 10 degrees, more preferably equal to or more than 15 degrees, but preferably equal to or less than 25 degrees, more preferably equal to or less than 20 degrees. 
     When the angles θo, θi, and θc of the portions  15  to  17  become large with the area of top surface  11  being unchanged, the tire mass becomes large, and the rubber volume of the protectors  10  become large and the heat generation increases, which may deteriorate the rolling resistance performance. In order to effectively achieve the above-mentioned effects, the angle θi of the inward-facing portion  16  is preferably equal to or more than 0 degrees, more preferably equal to or more than 5 degrees, but preferably equal to or less than 35 degrees, more preferably equal to or less than 25 degrees. Further, the angle θc of the circumferential portion  17  is preferably equal to or more than 5 degrees, more preferably equal to or more than 15 degrees, but preferably equal to or less than 45 degrees, more preferably equal to or less than 35 degrees. Furthermore, the angle θo of the outward-facing portion  15  is preferably equal to or more than 15 degrees, more preferably equal to or more than 25 degrees, but preferably equal to or less than 60 degrees, more preferably equal to or less than 50 degrees. These can improve the appearance performance while maintaining the traction performance. In addition, such a tire  1  has excellent cut resistance performance, rolling resistance performance, and the NV performance, and the increase in tire mass can be suppressed. 
     As illustrated in  FIG.  1    and  FIG.  2   , the tread portion  2 , for example, includes a shoulder land portion  8  forming the first tread edge To. The shoulder land portion  8  according to the present embodiment is divided into a plurality of shoulder blocks  8 R by a plurality of shoulder lateral grooves  9  extending so as to traverse the first tread end To in the tire axial direction. The shoulder blocks  8 R, for example, include block walls  8   a  that extend inwardly in the tire radial direction from the first tread edge To. In other words, the block walls  8   a  form a part of the first buttress portion  4 . 
     The first buttress portion  4 A, in the present embodiment, is provided with a groove portion  19  connected to inner edges in the tire radial direction of the block walls  8   a  and recessed inwardly in the tire axial direction. The groove portion  19 , for example, extends continuously in the tire circumferential direction. The groove portion  19  is not limited to such a manner, for example, but it may be formed in a plurality of groove elements in the tire circumferential direction arranged through one or more breaks (not shown). Also, the tire  1  according to the present disclosure is not limited to one including the groove portion  19 . 
     As illustrated in  FIG.  5   , the block walls  8   a  of the shoulder blocks  8 R, for example, are connected to the respective protectors  10  via the groove portion  19 . More specifically, the block walls  8   a  each include a pair of block edges  20  connecting the first tread edge To and the groove portion  19 . In each shoulder block  8 R, radial inner ends  20   e  of the block edges  20  are located in the same positions in the tire circumferential direction as the respective radial outer ends  17   i  of the circumferential portions  17  connected to the groove portion  19 . This can further improve the traction performance due to the shear force generated by the circumferential portions  17  and the block edges  20 . The “same position in the tire circumferential direction” means that a separation distance La in the tire circumferential direction between the adjacent inner ends  20   e  and outer ends  17   i  is within 5 mm. 
     The protectors  10 , in the present embodiment, have a maximum width W1 in the tire circumferential direction equal to or more than 10% of the tread width TW, more preferably equal to or more than 14%, but preferably equal to or less than 25% of the tread width TW, more preferably equal to or less than 20%. The protectors  10 . for example, have a maximum length L1 in the tire radial direction equal to or more than 12% of the tire section height Ha (shown in  FIG.  1   ), more preferably equal to or more than 16%, but preferably equal to or less than 30% of the tire section height Ha, more preferably equal to or less than 25%. The protectors  10  have a protruding height H1 (shown in  FIG.  1   ) equal to or more than 1.5 mm, more preferably equal to or more than 2.0 mm, but preferably equal to or less than 6.0 mm, more preferably equal to or less than 5.5 mm. 
       FIG.  6    is a front view of the first buttress portion  4 A according to the present embodiment. As illustrated in  FIG.  6   , each of the protectors  10 , for example, includes an outer portion  10   s  and an inner portion  10   u  located inwardly of the outer portion  10   s  in the tire radial direction. The outer portion  10   s  and the inner portion  10   u  are virtually demarcated by a circumferential line Y passing through the outer end  15   e  in the tire radial direction of the outward-facing portion  15 . The outer portion  10   s  is connected to the groove portion  19 , in the present embodiment. 
     The maximum width Ws of the outer portion  10   s  in the tire circumferential direction is smaller than the maximum width Wu of the inner portion  10   u  in the tire circumferential direction. This can reduce the tire mass distribution outside the tire radial direction, compared to the case where the maximum width Ws of the outer portion  10   s  is larger than the maximum width Wu of the inner portion  10   u , and can improve the NV performance. These protectors  10  may have excellent appearance performance. 
     The first buttress portion  4 A may have a recess K formed by the inner portion  10   u  and the outer portion  10   s . Such a recess K can increase the shear force in the tire circumferential and radial directions, thus improving the traction performance. 
     In a front view of the first buttress portion  4 A. the protectors  10 , in the present embodiment, include L-shaped first protectors  10 A protruding in the first tire circumferential direction F and inverted L-shaped second protectors  10 B protruding in the opposite direction to the first tire circumferential direction F. 
     Each of the first protectors  10 A, in the present embodiment, includes a single outward-facing portion  15 , two inward-facing portions  16 , and three circumferential portions  17 . The two inward-facing portions  16  include a first inward-facing portion  16 A that is inclined outwardly in the tire radial direction toward the first tire circumferential direction F and a second inward-facing portion  16 B inclined inwardly in the tire radial direction toward the first tire circumferential direction F side. The three circumferential portions  17  include a first circumferential portion  17 A connecting the groove portion  19  and the second inward-facing portion  16 B, a second circumferential portion  17 B connecting the groove portion  19  and the outward-facing portion  15 . and a third circumferential portion  17 C connecting the first inward-facing portion  16 A and the outward-facing portion  15 . The outward-facing portion  15 , in the present embodiment, is inclined inwardly in the tire radial direction toward the first tire circumferential direction F side. 
      Each of the second protectors  10 B includes a single outward-facing portion  15 . a single inward-facing portion  16 , and three circumferential portions  17 . The three circumferential portions  17  include a fourth circumferential portion  17 D adjacent to the first circumferential portion  17 A in the tire circumferential direction, a fifth circumferential portion  17 E connecting the groove portion  19  and the outward-facing portion  15 , and a sixth circumferential portion  17 F connecting the outward-facing portion  15  and the inward-facing portion  16 . The outward-facing portion  15  and the inward-facing portion  16 , in the present embodiment, are inclined outwardly in the tire radial direction toward the first tire circumferential direction F side. 
     In addition, the first buttress portion  4 A is provided with tie-bars  21  each of which connects a set of one of the first protectors  10 A and one of the second protectors  10 B which are adjacent in the tire circumferential direction. Each tie-bar  21 , in the present embodiment, protrudes outwardly in the tire axial direction with a protruding height which is smaller than that of the protectors  10 . Such a tie-bar  21  can enhances the rigidity in the tire circumferential direction of the first protectors  10 A and the second protectors  10 B to prevent chipping of the protectors  10 , thus improving the cut resistance of the first buttress portion  4 A. In addition, the tie-bar  21  can suppress the deformation of the first protectors  10 A and the second protectors  10 B, increase the shear force in the tire circumferential direction, and improve the traction performance. 
     In the present embodiment, each tie-bar  21  connects the first circumferential portion  17 A and the fourth circumferential portion  17 D. The tie-bar  21 , for example, is connected to an innermost end  17   j  of the first circumferential portion  17 A. 
       FIG.  7    is a front view of the first buttress portion  4 A.  FIG.  7    shows the edge  13  of the top surface  11  and an innermost edge  14  of the side surface  12  in the tire axial direction. The edge  13  of the top surface  11  is the outermost edge of the side surface  12  in the tire axial direction. The innermost edge  14  is the boundary between the outer surface  4   s  and the side surface  12 . As illustrated in  FIG.  7   , a width Wa of the outward-facing portion  15  in a direction orthogonal to the longitudinal direction is preferably greater than a width Wb of the inward-facing portion  16  in a direction orthogonal to the longitudinal direction. As a result, the rigidity of the outward-facing portion  15 , which is relatively easy to come into contact with mud, can be increased, and the cut resistance can be improved. In addition, the tire mass of the inward-facing portion  16  which has a relatively small chance of coming into contact with mud can be reduced. Also, when the width Wa of the outward-facing portion  15  and the width Wb of the inward-facing portion  16  are different, the visibility of the protectors  10  can be enhanced. 
     In order to effectively exert such an action, a width Wc of the circumferential portion  17  orthogonal to the longitudinal direction is preferably different from the width Wa of the outward-facing portion  15 . Further, the width Wc of the circumferential portion  17  orthogonal to the longitudinal direction is preferably different from the width Wb of the inward-facing portion  16 . 
       FIG.  8    illustrates a front view of the first buttress portion  4 A in accordance with another embodiment. The same elements as in the first buttress portion  4 A as the above-mentioned embodiment may be denoted with the same reference numbers and their description may be omitted. As illustrated in  FIG.  8   , the first buttress portion  4 A according to this embodiment is provided with the protectors  10 . 
     In this embodiment, the protectors  10  include at least one inverted L-shaped third protector  10 C protruding in the opposite direction to the first tire circumferential direction F. and at least one inverted L-shaped fourth protectors  10 D protruding in the opposite direction to the first tire circumferential direction F and having an area of the top surface  11  smaller than that of the third protector  10 C. 
     The third protector  10 C, in this embodiment, includes a single outward-facing portion  15 , a single inward-facing portion  16  and three circumferential portions  17 , like the second protectors  10 B. The fourth protector  10 D, in this embodiment, includes a single inward-facing portion  16  and three circumferential portions  17 . The three circumferential portions  17  of the fourth protector  10 D include a pair of outer circumferential portions  17 G and  17 G extending from the groove portion  19 , and an inner circumferential portion  17 H that connects an innermost end i in the tire radial direction of one of the outer circumferential portions  17 G adjacent to the third protector  10 C and the inward-facing portion  16 . The inner circumferential portion  17 H, for example, has an angle with respect to the tire radial direction larger than that of the circumferential portions  17 G. Even in the fourth protector  10 D, the angles θi and θc of the inward-facing portion  16  and the circumferential portions  17 , respectively, with respect to the respective normal lines n of the top surface  11  are set as in the above embodiment. 
       FIG.  9 A  is a front view of the first buttress portion  4 A according to yet another embodiment.  FIG.  9 B  is a cross-sectional view taken along the line D-D of  FIG.  9 A . The same elements as in the first buttress portion  4 A as the above-mentioned embodiment may be denoted with the same reference numbers and their description may be omitted . As illustrated in  FIGS.  9 A and  9 B , the top surfaces  11  are provided with border portions  25  extending along the edges  13  of the top surfaces  13 . The border portions  25 , in this embodiment, are located inwardly from the edges  13  of the top surfaces  11 . Note that the border portions  25  may be located to include the edges  13  (not illustrated). The border portions  25 , for example, are formed as projecting bodies  25   a  that protrude outwardly in the tire axial direction. Such border portions  25  can give a change in the visibility of the protectors  10  and improve the appearance performance. 
     The border portions  25 , for example, extend along the edges  13  forming the inward-facing portions  16  and the edges  13  forming the inward-facing portions  17 . The border portions  25 , for example, are arranged on the protectors  10 . In each protector  10 , the border portion  25  according to this embodiment is arranged inward in the tire radial direction from the outer end  15   e  of the outward-facing portion  15 . 
     The projecting bodies  25   a  each have an arc-shaped cross-section. This can effectively exert the above-mentioned effects. It is preferable that the arc-shaped cross-section of the projecting bodies  25   a  has a radius of curvature r of from 0.2 to 2 mm. 
     Although the particularly preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the embodiments shown in Figures. 
     EXAMPLE 
     Tires having the basic structure shown in  FIG.  1    and having the buttress portion shown in  FIG.  2    were prepared, and their appearance performance, traction performance, cut resistance, tire mass and NV performance were evaluated. The test methods and common specifications are as follows.
     Tire size: 265/70R18   Rim: 18x7.5 J   Internal pressure: 250 kPa   

     Appearance Performance Test 
     Ten test drivers evaluated the beauty and visibility of the first buttress portion sensually. The results are shown in Table 1 scored by the 20-point method with a maximum of 20 points, and are shown by the average score of 10 test drivers. The larger the value, the better the appearance performance. 
      Traction Performance and NV Performance Test 
     Each test tire was mounted on all wheels of a four-wheel drive vehicle with a displacement of 3500 cc. Then, a test driver drove the above vehicle on a test course. As for the traction performance, the driving characteristics related to the smoothness of acceleration when driving on a muddy road surface were evaluated by the sensuality of the test driver. The NV performance was evaluated by the sensuality of the test driver as to the degree of noise generated from the tire when running on dry asphalt. The results are shown in Table 1 by the 20-point method with a maximum of 20 points. The larger the value, the better the traction performance and NV performance. 
     Cut Resistance Test 
     A test driver drove the above vehicle about 1500 km on rocky road surfaces containing rocks and rubble. Then, the cut resistance was evaluated based on the depth of the cut scratches and the length of the cut scratches on the outer surface of the buttress portion. The test results are shown in Table 1 by the 20-point method with a maximum of 20 points. The larger the value, the smaller the cut scratches and the better the cut resistance. 
     Tire Mass Test 
     The mass of the protectors of each test tire was measured. The results are shown in Table 1 as an exponent with the reciprocal of the mass (kg) of Example 1 being 20. The larger the angles θi, θc, and θo, the smaller the area of the top surface and the smaller the tire mass. The larger the value, the smaller the mass and the better. Tires with a small mass have excellent rolling resistance. 
     The test results are shown in Table 1. The overall evaluation is the total points of each test result. A score of 85 or higher is passed in the overall evaluation.   
     
       
         
          TABLE 1
           
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
                   
                 Ref 1 
                 Ref. 2 
                 Ref. 3 
                 Ex. 1 
                 Ex. 2 
                 Ex. 3 
                 Ex. 4 
                 Ex. 5 
                 Ex. 6 
                 Ex. 7 
                 Ex. 8 
                 Ex. 9 
               
             
            
               
                 θi (deg.) 
                 0 
                 15 
                 15 
                 5 
                 45 
                 0 
                 5 
                 5 
                 50 
                 5 
                 5 
                 5 
               
               
                 θc (deg.) 
                 0 
                 15 
                 15 
                 15 
                 25 
                 30 
                 50 
                 15 
                 15 
                 15 
                 15 
                 15 
               
               
                 θo (deg.) 
                 0 
                 15 
                 15 
                 30 
                 10 
                 60 
                 60 
                 60 
                 30 
                 80 
                 30 
                 30 
               
               
                 Border portion(s) 
                 presence 
                 presence 
                 absence 
                 presence 
                 presence 
                 absence 
                 absence 
                 absence 
                 absence 
                 absence 
                 presence 
                 presence 
               
               
                 r (mm) 
                 1.0 
                 1.0 
                 - 
                 1.0 
                 1.0 
                 - 
                 - 
                 - 
                 - 
                 - 
                 0.1 
                 3.0 
               
               
                 Ws (mm) 
                 40 
                 70 
                 70 
                 40 
                 40 
                 40 
                 40 
                 40 
                 40 
                 40 
                 70 
                 70 
               
               
                 Wu (mm) 
                 80 
                 45 
                 45 
                 80 
                 80 
                 80 
                 80 
                 80 
                 80 
                 80 
                 45 
                 45 
               
               
                 Appearance performance [Score: larger is better.] 
                 14 
                 15 
                 14 
                 18 
                 16 
                 18 
                 17 
                 18 
                 16 
                 17 
                 17 
                 17 
               
               
                 Traction performance [Score: larger is better.] 
                 20 
                 18 
                 18 
                 18 
                 17 
                 17 
                 17 
                 18 
                 17 
                 18 
                 17 
                 18 
               
               
                 Cut resistance [Score: larger is better.] 
                 15 
                 16 
                 15 
                 18 
                 18 
                 17 
                 17 
                 16 
                 17 
                 16 
                 17 
                 19 
               
               
                 Tire mass [Index: larger is better.] 
                 16 
                 18 
                 18 
                 18 
                 17 
                 19 
                 17 
                 17 
                 18 
                 18 
                 18 
                 17 
               
               
                 NV performance [Score: larger is better.] 
                 16 
                 15 
                 15 
                 18 
                 17 
                 16 
                 18 
                 17 
                 17 
                 17 
                 16 
                 15 
               
               
                 Overall evaluation [85 points or higher is passed.] 
                 81 
                 82 
                 80 
                 90 
                 85 
                 87 
                 86 
                 86 
                 85 
                 86 
                 85 
                 86 
               
            
           
         
       
     
     As a result of the test, it is confirmed that the tires of the examples can improve cut resistance and mud performance as compared with the tires of the comparative examples. It is also confirmed that the tires of the examples can suppress the increase in tire mass. 
     Additional Note 
     The present disclosure includes the following aspects. 
     Note 1 
     A pneumatic tire comprising:
     a tread portion having a first tread edge, and   a first buttress portion extending inwardly in a tire radial direction from the first tread edge, wherein   the first buttress portion is provided with a plurality of protectors protruding outwardly in a tire axial direction,   each of the plurality of protectors comprises a top surface facing outwardly in the tire axial direction, and a side surface extending inwardly in the tire axial direction from an edge of the top surface,   the side surface comprises an outward-facing portion facing outwardly in the tire radial direction, an inward-facing portion facing inwardly in the tire radial direction, and a circumferential portion facing in a tire circumferential direction, and   the outward-facing portion, the inward-facing portion and the circumferential portion have different angles with respect to respective normal lines of the top surface from each other.   

     Note 2 
     A pneumatic tire comprising: 
     a tread portion having a first tread edge, and   a first buttress portion extending inwardly in a tire radial direction from the first tread edge, wherein   the first buttress portion is provided with a plurality of protectors protruding outwardly in a tire axial direction,   each of the plurality of protectors comprises a top surface facing outwardly in the tire axial direction, and a side surface extending inwardly in the tire axial direction from an edge of the top surface,   the side surface comprises an inward-facing portion facing inwardly in the tire radial direction, and a circumferential portion facing in a tire circumferential direction, and   the inward-facing portion and the circumferential portion have different angles with respect to respective normal lines of the top surface from each other.   

     Note 3 
     The pneumatic tire according to note 1 or 2, wherein 
     an angle θi of the inward-facing portion with respect to the normal line is smaller than an angle θc of the circumferential portion with respect to the normal line. 
     Note 4 
     The pneumatic tire according to note 3, wherein 
     a difference (θc - θi) between the angle θc of the circumferential portion with respect to the normal line and the angle θi of the inward-facing portion with respect to the normal line is in a range from 10 to 25 degrees. 
     Note 5 
     The pneumatic tire according to any one of notes 1 to 4, wherein 
     an angle θi of the inward-facing portion with respect to the normal line is equal to or less than 35 degrees, and   an angle θc of the circumferential portion with respect to the normal line is in a range from 5 to 45 degrees.   

     Note 6 
     The pneumatic tire according to note 1, wherein 
     an angle θc of the circumferential portion with respect to the normal line is smaller than an angle θo of the outward-facing portion with respect to the normal line. 
     Note 7 
     The pneumatic tire according to note 6, wherein 
     a difference (θo - θc) between the angle θo of the outward-facing portion with respect to the normal line and the angle θc of the circumferential portion with respect to the normal line is in a range from 10 to 25 degrees. 
     Note 8 
     The pneumatic tire according to note 6 or 7. wherein 
     the angle θo of the outward-facing portion with respect to the normal line is in a range from 15 to 60 degrees. 
     Note 9 
     The pneumatic tire according to any one of notes 1 to 8, wherein
     each of the plurality of protectors comprises an outer portion and an inner portion located inwardly in the tire radial direction of the outer portion, and   a maximum length in a tire circumferential direction of the outer portion is smaller than a maximum length in the tire circumferential direction of the inner portion.   

     Note 10 
     The pneumatic tire according to any one of notes 1 to 9, wherein 
     the top surface is provided with a border portion extending along the edge of the top surface. 
     Note 11 
     The pneumatic tire according to note 10, wherein 
     the border portion extends along an edge part forming the inward-facing portion and an edge part forming the circumferential portion. 
     Note 12 
     The pneumatic tire according to note 10 or 11, wherein 
     the border portion has a projecting body protruding outwardly in the tire axial direction. 
     Note 13 
     The pneumatic tire according to note 12, wherein 
     the projecting body, in a cross-sectional view thereof, has an arc-shaped surface having a radius of curvature of from 0.2 to 2 mm.