JP6136133B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can improve fuel efficiency while ensuring water splash control performance of the tire.

  In recent years, a heavy load pneumatic tire employs a structure in which fins are provided in a buttress portion of a tire as a countermeasure against water splashes generated when traveling on a wet road surface. And by this fin, the kinetic energy of water splash is absorbed and the scattering height of water splash is reduced. As conventional pneumatic tires employing such a configuration, techniques described in Patent Documents 1 and 2 are known.

JP 2000-318410 A Special table 2010-528916

  Here, in the pneumatic tire including the above-described fins, when the tire rolls, the air resistance may increase due to the fins, and the fuel efficiency of the tire may be deteriorated.

  Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire that can improve fuel efficiency while ensuring water splash suppression performance of the tire.

In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire having a buttress portion with water splash suppression fins, the buttress portion being located between the tire ground contact edge and the tire maximum width position. The height H of the fin is in the range of 10.0 [mm] ≦ H ≦ 15.0 [mm], and the top of the fin is more than the tire maximum width position. located widthwise inwardly, the fins, the tire circumferential direction discontinuously disposed of Rutotomoni the fin height direction plurality of which are discontinuously disposed dimples in the tire radial direction outer side wall surface and the tire radial direction inner side of the A relationship of 0.10 ≦ a ′ / L ≦ 0.4 is established, in which at least one of the wall surfaces, the width a ′ of the dimple applied in the height direction of the fin and the predetermined wall length L of the fin it has a And features.

  In the pneumatic tire according to the present invention, since the fin includes a plurality of dimples arranged discontinuously in the tire circumferential direction on the wall surface, turbulence is generated around the fin when the tire rolls, and the wall surface of the fin The separation of the air flow from the air is alleviated. Thereby, there is an advantage that the separation region of the air flow in the rear of the vehicle traveling direction is reduced, the air resistance is reduced, and the fuel efficiency performance of the tire is improved.

FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged view showing fins of the pneumatic tire depicted in FIG. 1. FIG. 3 is a perspective sectional view showing fins of the pneumatic tire shown in FIG. 1. FIG. 4 is an explanatory view showing the dimples of the fin described in FIG. FIG. 5 is an explanatory view showing the dimples of the fin described in FIG. FIG. 6 is an explanatory view showing the action of the dimples of the fin described in FIG. FIG. 7 is an explanatory view showing the action of the dimples of the fin described in FIG. FIG. 8 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. FIG. 9 is an explanatory view illustrating a modified example of the pneumatic tire depicted in FIG. 1. FIG. 10 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. FIG. 11 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. FIG. 12 is an explanatory diagram illustrating a modification of the pneumatic tire depicted in FIG. 1. FIG. 13 is an explanatory view illustrating a modified example of the pneumatic tire depicted in FIG. 1. FIG. 14 is an explanatory view showing a modified example of the pneumatic tire depicted in FIG. 1. FIG. 15 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. As an example of the pneumatic tire 1, FIG. 1 shows a heavy duty radial tire mounted on a steer shaft such as a truck or bus for long-distance transportation. Reference sign CL is a tire equator plane.

  The pneumatic tire 1 includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16, and a pair. Rim cushion rubbers 17 and 17 (see FIG. 1).

  The pair of bead cores 11 and 11 has an annular structure and constitutes the core of the left and right bead portions. The pair of bead fillers 12 and 12 includes a lower filler 121 and an upper filler 122, which are disposed on the tire radial direction outer periphery of the pair of bead cores 11 and 11, respectively, to reinforce the bead portion.

  The carcass layer 13 is bridged in a toroidal shape between the left and right bead cores 11 and 11 to form a tire skeleton. Further, both ends of the carcass layer 13 are wound and locked from the inner side in the tire width direction to the outer side in the tire width direction so as to wrap the bead core 11 and the bead filler 12. The carcass layer 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material (for example, nylon, polyester, rayon, etc.) with a coating rubber and rolling them, and has an absolute value of 85 [deg] or more and 95. [Deg] The following carcass angle (inclination angle in the fiber direction of the carcass cord with respect to the tire circumferential direction).

  The belt layer 14 is formed by laminating a plurality of belt plies 141 to 144, and is arranged around the outer periphery of the carcass layer 13. These belt plies 141 to 144 include, for example, a high-angle belt 141, a pair of cross belts 142 and 143, and a belt cover 144. Each belt ply 141 to 144 is formed by rolling a plurality of belt cords made of steel or organic fiber material with a coating rubber and rolling the belt cords, and a predetermined belt angle (inclination of the belt cord in the fiber direction with respect to the tire circumferential direction). Corner).

  The tread rubber 15 is disposed on the outer circumference in the tire radial direction of the carcass layer 13 and the belt layer 14 to constitute a tread portion of the tire. The pair of side wall rubbers 16 and 16 are respectively arranged on the outer side in the tire width direction of the carcass layer 13 to constitute left and right side wall portions. The pair of rim cushion rubbers 17 and 17 are arranged on the outer sides in the tire width direction of the left and right bead cores 11 and 11 and the bead fillers 12 and 12, respectively, and constitute left and right bead portions.

  The pneumatic tire 1 includes a plurality of circumferential main grooves 21 and 22 extending in the tire circumferential direction and a plurality of land portions 31 to 33 that are partitioned by the circumferential main grooves 21 and 22. Prepare for the department.

  For example, in the configuration of FIG. 1, the four circumferential main grooves 21 and 22 are arranged symmetrically about the tire equatorial plane CL. The circumferential main grooves 21 and 22 define three rows of center land portions 31 and 32 and a pair of left and right shoulder land portions 33. Further, the circumferential main groove 22 on the outermost side in the tire width direction has the deepest groove depth, and the second land portion 32 and the shoulder land portion 33 are partitioned by the circumferential main groove 22. The circumferential main groove means a circumferential groove having a groove depth of 8.0 [mm] or more.

[Fin for water splash control]
2 and 3 are an enlarged view (FIG. 2) and a perspective sectional view (FIG. 3) showing the fins of the pneumatic tire shown in FIG.

  This pneumatic tire 1 includes fins 6 for suppressing water splash (see FIGS. 2 and 3). The fins 6 are formed on at least the buttress portions on the left and right sides of the tire at the buttress portion on the outer side in the vehicle width direction when the vehicle is mounted. For example, in the configuration of FIG. 1, the fins 6 are respectively formed on the left and right buttress portions of the tire. The fin 6 has a shape protruding in the tire width direction from the profile of the buttress portion, and has a wall surface on the outer side in the tire radial direction (tire contact end side) and a wall surface on the inner side in the tire radial direction (side wall portion side). . Further, the fin 6 has an annular and rib-like structure that continuously extends over the entire circumference of the tire.

  Note that the buttress portion refers to a side wall portion between the tire ground contact end A and the tire maximum width position. Further, the fin 6 may be integrally formed with the sidewall rubber 16 at the time of tire vulcanization molding, or may be adhered and attached after the tire vulcanization molding.

  Further, the shape and position of the fin 6 are set as follows.

  First, a tangent line l is drawn from the tire ground contact end A to the fin 6 in a cross-sectional view in the tire meridian direction when the tire is mounted on the specified rim and applied with a specified internal pressure and is in an unloaded state. Let B be the contact point with the fin 6. Further, the inclination angle of the tangent line 1 with respect to the tire axial direction is defined as θ. Further, a curve m parallel to the profile of the tread surface is drawn from the groove bottom of the deepest circumferential main groove (here, the circumferential main groove 22 on the outermost side in the tire width direction). Let P be the intersection with.

  At this time, the top of the fin 6 has an arc-shaped outline, and the contact point B is positioned on the arc of the top. In addition, the wall surface on the outer side in the tire radial direction of the fin 6 is recessed toward the tire inner side with respect to the tangent l. Thus, a concave side wall surface that is curved or bent in the tire axial direction from the tire ground contact end A toward the contact point B is formed. In the configuration of FIG. 2, the wall surface on the outer side in the tire radial direction and the wall surface on the inner side in the tire radial direction of the fin 6 have an arc-shaped contour line that is concave on the inner side of the fin 6. Are connected smoothly.

  Further, the inclination angle θ of the tangent l is in the range of θ <45 [deg], and more preferably in the range of 32 [deg] ≦ θ ≦ 37 [deg]. Further, the fin 6 is disposed on the wall surface on the inner side in the tire radial direction from the intersection P. Further, the arrangement position and the height H of the fin 6 are adjusted so that the top of the fin 6 does not exceed the tire maximum width position. As a result, the shape and position of the fin 6 are optimized. In addition, the height H of the fin 6 is measured on the basis of the profile of the buttress portion, and is preferably in the range of 10.0 [mm] ≦ H ≦ 15.0 [mm].

  The tire ground contact end A is a tire when a tire is mounted on a specified rim and applied with a specified internal pressure, and is placed perpendicular to a flat plate in a stationary state and applied with a load corresponding to the specified load. The end in the tire axial direction on the contact surface between the flat plate and the flat plate.

  The specified rim is an “applied rim” defined in JATMA, a “Design Rim” defined in TRA, or a “Measuring Rim” defined in ETRTO. The specified internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The specified load means the “maximum load capacity” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO. However, in JATMA, in the case of tires for passenger cars, the specified internal pressure is air pressure 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

[Fin dimples]
4 and 5 are explanatory views showing the dimples of the fin described in FIG. In these drawings, FIG. 4 shows a sectional view in the tire meridian direction of the fin 6 at the position where the dimple 7 is arranged, and FIG. 5 shows a developed view of the wall surface of the fin 6 from the point P to the point B.

  In this pneumatic tire 1, the fin 6 includes a plurality of dimples 7 (see FIGS. 3 to 5). These dimples 7 are arranged on at least one of the wall surface on the outer side in the tire radial direction of the fin 6 and the wall surface on the inner side in the tire radial direction. Therefore, the dimple 7 may be disposed only on one side wall surface of the fin 6 (not shown). The dimples 7 are discontinuously arranged in the tire circumferential direction. These dimples 7 are discontinuously arranged in the height direction of the fins 6. Therefore, the dimples 7 are arranged independently of each other (without communication) in the tire circumferential direction and the height direction of the fins 6. In addition, the case where the dimples 7 adjacent to each other in the tire circumferential direction are in contact with each other will be described later.

  For example, in the configuration of FIG. 5, the fin 6 has a hemispherical dimple 7. A plurality of dimples 7 are respectively disposed on both the outer wall surface in the tire radial direction and the inner wall surface in the tire radial direction of the fin 6. A plurality of dimples 7 are arranged over the entire circumference of the fin 6 with a predetermined interval in the tire circumferential direction and the height direction of the fin 6. Further, the fin 6 includes a group of three rows of dimples 7 arranged side by side in the tire circumferential direction. Thereby, the plurality of dimples 7 are arranged in a matrix over the entire wall surface of the fin 6.

  In the pneumatic tire 1, the width a of the dimple 7 in the tire circumferential direction and the center distance b between the dimples 7 and 7 adjacent in the tire circumferential direction are 1.0 ≦ b / a ≦ 5.0. It is preferable to have the following relationship. The width a of the dimple 7 is the opening width of the dimple 7 and is measured in a plan view of the wall surface of the fin 6. The center distance b of the dimple 7 is also measured in a plan view of the wall surface of the fin 6. In addition, when b / a = 1.0, the dimples 7 and 7 adjacent to each other in the tire circumferential direction come into contact with each other.

  In this pneumatic tire 1, the width a ′ of the dimple 7 in the height direction of the fin 6 and the wall length L of the fin 6 satisfy the relationship of 0.10 ≦ a ′ / L ≦ 1.0. Have. The width a ′ of the dimple 7 is the opening width of the dimple 7 and is measured in a plan view of the wall surface of the fin 6. The wall length L of the fin 6 is measured as the distance between the point P and the point B in the development view of the wall surface of the fin 6. When a ′ = L, one dimple 7 extends over the entire area of the fin 6 in the height direction.

  In this pneumatic tire 1, it is preferable that the maximum width a_max of the dimple 7 and the depth d of the dimple 7 have a relationship of 0.05 ≦ d / a_max ≦ 1.0. However, the depth d of the dimple 7 is set in a range in which the dimple 7 does not penetrate the fin 6. The maximum width a_max of the dimple 7 is the maximum value of the opening width of the dimple 7 in an arbitrary direction, and is measured in a plan view of the wall surface of the fin 6.

  6 and 7 are explanatory views showing the action of the dimples of the fin described in FIG. In these drawings, FIG. 6 shows a state of air flow in the tire circumferential direction at the time of tire rolling, and FIG. 7 shows a state of air flow in the tire radial direction at the time of tire rolling.

  In general, in a pneumatic tire provided with fins for water splash suppression in the buttress portion, as shown in FIG. 6, an air flow that flows in the tire circumferential direction along the fins is generated during tire rolling. At this time, in the configuration in which the fin has a flat wall surface (conventional example 1 without dimples described later), the air flow is easily separated from the wall surface of the fin, and the separation region of the air flow in the rearward direction of the vehicle increases. As a result, air resistance increases, and the fuel efficiency of the tire may be deteriorated.

  In this respect, in the pneumatic tire 1, as shown in FIG. 6, the fin 6 includes a plurality of dimples 7 disposed discontinuously in the tire circumferential direction on the wall surface. A turbulent flow is generated around the air and the separation of the air flow from the wall surface of the fin 6 is alleviated. As a result, the separation region of the air flow behind the vehicle traveling direction is reduced, the air resistance is reduced, and the fuel efficiency performance of the tire is improved.

  Further, as shown in FIG. 7, during tire rolling, an air flow flows along the tire side surface and crosses the tire in the radial direction. For this reason, the air flow hits the wall surface on the outer side in the tire radial direction of the fin 6 at the front in the vehicle traveling direction, and hits the wall surface on the inner side in the tire radial direction at the rear in the vehicle traveling direction. At this time, since the fin 6 has the dimples 7 on both the outer wall surface in the tire radial direction and the inner wall surface in the tire radial direction (see FIG. 4), the separation region of the air flow straddling the fin 6 is reduced. The resistance is reduced and the fuel efficiency of the tire is improved.

  Furthermore, as shown in FIG. 7, the fin 6 includes a plurality of dimples 7 discontinuously arranged in the height direction of the fin 6 (see FIGS. 4 and 5), so that the fin 6 has a height of the fin 6. Compared with a configuration including a single dimple 7 in the direction (see FIG. 11), the separation region of the air flow across the fin 6 is reduced. As a result, the air resistance is further reduced, and the fuel efficiency of the tire is further improved.

[Modification]
8-14 is explanatory drawing which shows the modification of the pneumatic tire described in FIG. These drawings show development views of the wall surface of the fin 6 from the point P to the point B. FIG.

  In the configuration of FIG. 5, the width a of the dimple 7 in the tire circumferential direction and the center distance b between the dimples 7 and 7 adjacent in the tire circumferential direction have a relationship of 1.0 <b / a. The dimples 7 and 7 adjacent in the tire circumferential direction are arranged separately from each other with a predetermined interval. Similarly, the dimples 7 adjacent to each other in the height direction of the fins 6 are arranged separately from each other with a predetermined interval.

  On the other hand, in the configuration shown in FIG. 8, the dimples adjacent in the tire circumferential direction have a relationship of b / a = 1.0 between the width a of the dimples 7 adjacent in the tire circumferential direction and the center distance b. 7 and 7 are in contact with each other. Similarly, the dimples 7 and 7 adjacent to each other in the height direction of the fin 6 are in contact with each other.

  At this time, if the depth d at the boundary between adjacent dimples is d = 0, it can be said that these dimples are discontinuously arranged. Therefore, even when adjacent dimples are in contact with each other (when the width a of the dimples in the tire circumferential direction and the center distance b between the dimples adjacent in the tire circumferential direction are a = b), the dimple depth d is It can be said that these dimples are discontinuously arranged in the tire circumferential direction on condition that d = 0 [mm] at the edge of the dimple. Therefore, adjacent dimples 7 may contact each other as in the configuration of FIG.

  Further, in the configuration of FIG. 5, the dimple 7 has a circular shape in plan view of the wall surface of the fin 6, and also has a hemispherical inner peripheral surface shape (see FIG. 4). However, the present invention is not limited thereto, and the dimple 7 may have an arbitrary planar shape such as an ellipse or a polygon. Further, the dimple 7 can have any inner peripheral shape such as a truncated cone and a truncated pyramid.

  For example, in the configuration of FIG. 9, the dimple 7 has an elliptical shape that is long in the height direction of the fin 6. In the configuration of FIG. 10, the dimple 7 has an octagonal planar shape. In the configuration of FIG. 11, the dimples 7 have a triangular planar shape, and the plurality of dimples 7 are arranged in a zigzag shape in the tire circumferential direction while reversing directions.

  In the configuration of FIG. 5, the fin 6 includes a group of dimples 7 that are discontinuously arranged in the tire circumferential direction, and includes three rows of dimple groups. As shown in FIG. 7, such a configuration is preferable in that the separation region of the air flow on the downstream side of the fin 6 can be reduced with respect to the air flow flowing across the fin 6.

  However, the present invention is not limited to this, and only one row of dimples 7 may be arranged in the tire circumferential direction. For example, in the configuration of FIG. 12, only one row of dimples 7 is arranged with a predetermined interval in the tire circumferential direction. Further, since the dimple 7 has an elliptical shape that is long in the height direction of the fin 6, the dimple 7 extends over an area of 50% or more of the wall length L of the fin 6.

  Further, in the configuration of FIG. 5, the fin 6 has only the dimple 7 having the same diameter and a circular shape. For this reason, each dimple 7 has the same opening area.

  However, the present invention is not limited to this, and the fin 6 may include a plurality of types of dimples having different opening areas. For example, in the configuration of FIG. 13, three rows of dimples 7 having a large diameter and a circular shape are arranged side by side in the tire circumferential direction, and 1 d having a small diameter and a circular shape between these dimples 7 group. Seven groups of dimples in a row are arranged. Therefore, the large-diameter dimple 7 and the small-diameter dimple 7 are arranged in a mixed manner. Thereby, the air resistance of the fin 6 is reduced effectively.

  Further, in the configuration of FIG. 14, the fins 6 have two rows of dimples 7 having a large diameter and a circular shape, and three rows of dimples 7 having a small diameter and a circular shape are adjacent to each other in the height direction of the fin 6. Are arranged together. The opening area of the three rows of dimples 7 arranged on the top side of the fin 6 is smaller than the opening area of the two rows of dimples 7 arranged on the root side of the fin 6. Thus, the air resistance of the fin 6 is effectively reduced by setting the opening area of the dimple 7 arranged on the top side of the fin 6 small.

  As shown in FIGS. 13 and 14, in the configuration in which the fin 6 includes a plurality of types of dimples 7, the widths a1 and a2 in the tire circumferential direction and the width a1 ′ in the height direction of the fins 6 in each type of dimple 7 a2 ′, arrangement intervals b1, b2 and wall length L of the fin 6 are 1.0 ≦ b1 / a1 ≦ 5.0, 1.0 ≦ b2 / a2 ≦ 5.0, 0.10 ≦ a1 ′ / L It is preferable to satisfy the relationship of ≦ 1.0 and 0.10 ≦ a2 ′ / L ≦ 1.0, respectively.

[effect]
As described above, in the pneumatic tire 1, the buttress part includes the fins 6 for suppressing water splash (see FIGS. 1 to 3). Further, the fin 6 includes a plurality of dimples 7 arranged discontinuously in the tire circumferential direction on at least one of the outer wall surface in the tire radial direction and the inner wall surface in the tire radial direction (see FIGS. 4 and 5).

  In such a configuration, the fin 6 includes a plurality of dimples 7 arranged discontinuously in the tire circumferential direction on the wall surface. Therefore, turbulence is generated around the fin 6 when the tire rolls, and from the wall surface of the fin 6. The air flow separation is reduced (see FIG. 6). Thereby, there is an advantage that the separation region of the air flow in the rear of the vehicle traveling direction is reduced, the air resistance is reduced, and the fuel efficiency performance of the tire is improved.

  Further, in the pneumatic tire 1, the relationship of 1.0 ≦ b / a ≦ 5.0 is established, in which the width a of the dimple 7 in the tire circumferential direction and the center distance b between the dimples 7 adjacent in the tire circumferential direction are (See FIG. 5). In such a configuration, the relationship between the width a of the dimple 7 and the center-to-center distance b in the tire circumferential direction is optimized, thereby improving the turbulent flow generation effect by the dimple 7 and reducing the air resistance of the fin 6. There are advantages.

  In the pneumatic tire 1, the width a ′ of the dimple 7 in the height direction of the fin 6 and the predetermined wall length L of the fin 6 satisfy 0.10 ≦ a ′ / L ≦ 1.0. There is a relationship (see FIG. 5). In such a configuration, the relationship between the width a ′ of the dimple 7 in the height direction of the fin 6 and the wall length L of the fin 6 is optimized, so that the effect of generating turbulence by the dimple 7 is improved, and the fin There is an advantage that the air resistance of 6 is reduced.

  In the pneumatic tire 1, the maximum width a_max of the dimple 7 (a_max = a = a ′ in FIG. 5) and the depth d of the dimple 7 satisfy 0.05 ≦ d / a_max ≦ 1.0. There is a relationship (see FIG. 4). In such a configuration, the relationship between the maximum width a_max and the depth d of the dimple 7 is optimized, so that the effect of generating turbulence by the dimple 7 is improved, and the air resistance of the fin 6 is reduced.

  Moreover, in this pneumatic tire 1, the fin 6 has a plurality of dimples 7 on both the outer wall surface in the tire radial direction and the inner wall surface in the tire radial direction (see FIG. 4). In such a configuration, when the tire rolls, the air flow that flows along the tire side surface and traverses the tire in the radial direction hits the wall surface on the outer side in the tire radial direction of the fin 6 in the vehicle traveling direction, and moves backward in the vehicle traveling direction. It hits the wall surface in the tire radial direction (see FIG. 7). At this time, since the fin 6 has the dimples 7 on both the outer wall surface in the tire radial direction and the inner wall surface in the tire radial direction (see FIG. 4), the separation region of the air flow straddling the fin 6 is reduced. There is an advantage that the resistance is reduced and the fuel efficiency of the tire is improved.

  Moreover, in this pneumatic tire 1, the fin 6 is provided with the some dimple 7 arrange | positioned discontinuously in the height direction of the fin 6 (refer FIG. 5). Thereby, the turbulent flow generation effect by the dimple 7 is improved, and there is an advantage that the air resistance of the fin 6 is reduced.

  Moreover, in this pneumatic tire 1, the fin 6 is provided with the multiple types of dimple 7 which has mutually different opening areas (refer FIG. 13). Thereby, the turbulent flow generation effect by the dimple 7 is improved, and there is an advantage that the air resistance of the fin 6 is reduced.

  In the pneumatic tire 1, the dimple 7 disposed on the top side of the fin 6 among the dimples 7 adjacent to each other in the height direction of the fin 6 has an opening area of the dimple 7 disposed on the root side of the fin 6. It is smaller than the opening area (see FIG. 14). In such a configuration, when the tire rolls, the separation region of the air flow that flows along the tire side surface, traverses the tire in the radial direction, and straddles the fins 6 is reduced (see FIG. 7). Thereby, there exists an advantage which air resistance further reduces and the fuel-consumption performance of a tire improves further.

  FIG. 15 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  In this performance test, evaluations on (1) water splash suppression performance and (2) fuel consumption performance were performed on a plurality of different pneumatic tires (see FIG. 15). In this performance test, a pneumatic tire having a tire size of 275 / 70R22.5 is assembled to a rim having a rim size of 22.5 × 7.50, and the pneumatic tire has an air pressure of 900 [kPa] and a front wheel load of 30.89 [kN]. A rear wheel load of 28.44 [kN] is applied. A pneumatic tire is mounted on a truck having a total weight of 25 [ton], which is a test vehicle.

  (1) In the evaluation regarding the water splash suppression performance, the test vehicle travels straight on a wet road having a water depth of 10 [mm], and the splash height of the water splash is photographed with a video camera and measured. Then, based on the measurement result, index evaluation is performed with the conventional example 1 as a reference (100). This evaluation is preferable as the numerical value increases.

  (2) In the evaluation relating to the fuel consumption performance, the test vehicle travels on a test course having a total length of 2 [km] at a speed of 100 [km / h] for 5 hours, and the travel distance per liter of gasoline is measured. Then, based on the measurement result, index evaluation is performed with the conventional example 1 as a reference (100). This evaluation is preferable as the numerical value increases.

  In the pneumatic tires 1 of Examples 1 to 17, the fin 6 includes a plurality of dimples 7 on both the inner wall surface and the outer wall surface in the tire radial direction (see FIG. 4). The height of the fin 6 is 15 [mm].

  The pneumatic tire of Conventional Example 1 is the same as the pneumatic tire 1 of Example 1, but the fins 6 do not have dimples. The pneumatic tire of Conventional Example 2 has a row of through-holes in which the fins are arranged at predetermined intervals in the tire circumferential direction in the central portion of the pneumatic tire of Conventional Example 1.

  As shown in the test results, in the pneumatic tires 1 of Examples 1 to 17, it can be seen that the fuel efficiency can be improved while ensuring the water splash suppression performance of the tire.

  DESCRIPTION OF SYMBOLS 1 Pneumatic tire, 11 Bead core, 12 Bead filler, 121 Lower filler, 122 Upper filler, 13 Carcass layer, 14 Belt layer, 141-144 Belt ply, 15 Tread rubber, 16 Side wall rubber, 17 Rim cushion rubber, 21, 22 circumferential grooves, 31-33 land, 6 fins, 7 dimples

Claims (6)

It is a pneumatic tire provided with fins for water splash suppression in the buttress part,
The buttress portion is defined as a side wall portion between a tire ground contact edge and a tire maximum width position;
The height H of the fin is in the range of 10.0 [mm] ≦ H ≦ 15.0 [mm],
The top of the fin is inside the tire width direction from the tire maximum width position,
The fin includes a plurality of dimples arranged discontinuously in the tire circumferential direction and discontinuously arranged in the height direction of the fin on at least one of a wall surface on the tire radial direction outer side and a wall surface on the tire radial direction inner side. ,and,
Pneumatic, characterized in that a width a ′ of the dimple in the height direction of the fin and a predetermined wall length L of the fin have a relationship of 0.10 ≦ a ′ / L ≦ 0.4 tire.   The pneumatic according to claim 1, wherein a width a of the dimple in the tire circumferential direction and a center distance b between dimples adjacent in the tire circumferential direction have a relationship of 1.0 ≦ b / a ≦ 5.0. tire.   The pneumatic tire according to claim 1 or 2, wherein a maximum width a_max of the dimple and a depth d of the dimple have a relationship of 0.05 ≦ d / a_max ≦ 1.0.   The pneumatic tire according to any one of claims 1 to 3, wherein the fin includes the plurality of dimples on both the outer wall surface in the tire radial direction and the inner wall surface in the tire radial direction.   The pneumatic tire according to any one of claims 1 to 4, wherein the fin includes a plurality of types of the dimples having different opening areas. The opening area of the dimple arranged on the top side of the fin among the dimples adjacent to each other in the height direction of the fin is smaller than the opening area of the dimple arranged on the root side of the fin. The described pneumatic tire.

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