JP2012066662A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having increased droplet splash suppressing performance.SOLUTION: This pneumatic tire 1 includes a projection 7 for droplet splash reduction at the side wall section. The projection 7 includes a soft rubber layer 71 having rubber hardness according to JIS-A which is less than 55 degrees and smaller than that of a tread rubber 5. When droplets collide with the projection 7, the kinetic energy of the droplets is absorbed and attenuated by the soft rubber layer 71 of the projection 7. Consequently, the splashed height (maximum value) of the droplets is decreased.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of improving water splash suppression performance.

  2. Description of the Related Art In recent years, heavy load pneumatic tires employ a configuration in which a protrusion is provided on a buttress portion of a tire as a countermeasure against water splashes that occur when traveling on a wet road surface. And by this protrusion part, the kinetic energy of water splash is absorbed and the scattering height of water splash is reduced. As a conventional pneumatic tire employing such a configuration, a technique described in Patent Document 1 is known.

JP 2000-318410 A

  An object of the present invention is to provide a pneumatic tire capable of improving water splash suppression performance.

  In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire provided with a protrusion for reducing water splash on a side wall, wherein the protrusion is less than 55 degrees and smaller than a tread rubber. A soft rubber layer having -A rubber hardness is provided.

  In this pneumatic tire, when water splashes collide with the protrusion, the kinetic energy is absorbed by the soft rubber layer of the protrusion and is attenuated. Thereby, there is an advantage that the splash height (maximum value) of the water splash is reduced and the water splash suppression performance of the tire is improved.

  In the pneumatic tire according to the present invention, the soft rubber layer is disposed on the surface of the protrusion.

  In this pneumatic tire, since the water splash directly collides with the soft rubber layer on the surface of the protrusion, the kinetic energy is efficiently absorbed by the soft rubber layer and attenuated. Thereby, there is an advantage that the splash height of the water splash is reduced and the water splash suppression performance of the tire is further improved.

  In the pneumatic tire according to the present invention, the thickness d of the soft rubber layer is in a range of 0 [mm] <d <7 [mm].

  In this pneumatic tire, since the thickness d of the soft rubber layer is optimized, there is an advantage that both the water splash suppression performance and the durability performance of the tire are compatible.

  In the pneumatic tire according to the present invention, the soft rubber layer extends to the wall surface on the radially inner side of the protrusion.

  In this pneumatic tire, the kinetic energy of the water splash that travels around the protrusion in the radial direction of the tire and scatters is absorbed and attenuated by the soft rubber layer extending to the wall of the protrusion in the radial direction of the tire. . Thereby, there is an advantage that the splash height of the water splash is reduced and the water splash suppression performance of the tire is further improved.

  The pneumatic tire according to the present invention draws a curve m parallel to the profile of the tread surface from the groove bottom of the circumferential main groove having the deepest groove depth among the circumferential main grooves formed in the tread portion. When the intersection of the curve m and the side wall portion is P, the soft rubber layer is inside the tire radial direction from the intersection P.

  In this pneumatic tire, the soft rubber layer is disposed at a position deviating from the wear range of the tread portion (the range from the wear of the tread portion until the wear indicator of the circumferential main groove appears). Therefore, since the exposure of the soft rubber layer to the tread surface is prevented at the end of wear, there is an advantage that uneven wear of the tread portion is prevented.

  Further, in the pneumatic tire according to the present invention, when the tangent line 1 is drawn from the tire ground contact edge to the protrusion, and the contact between the tangent l and the protrusion is T, the soft rubber layer includes at least the contact T. Placed in the area.

  In this pneumatic tire, since the soft rubber layer is at the end portion (contact point T) of the protrusion, there is an advantage that the water splash suppression performance of the tire is effectively improved.

  The pneumatic tire according to the present invention has an JIS-A rubber hardness smaller than the tread rubber and larger than the soft rubber layer, and an intermediate rubber layer disposed between the tread rubber and the soft rubber layer. Is provided.

  In this pneumatic tire, when the intermediate rubber layer is disposed, the JIS-A rubber hardness at the protruding portion gradually decreases from the surrounding tread rubber toward the soft rubber layer. Thereby, when the difference in rubber hardness between the tread rubber and the soft rubber layer is large, there is an advantage that the structural strength around the protrusion can be secured. Moreover, since the kinetic energy of water splash is absorbed by both the soft rubber layer and the intermediate rubber layer, there is an advantage that the water splash suppression performance of the tire is effectively improved.

  In the pneumatic tire according to the present invention, a protective rubber layer having a JIS-A rubber hardness larger than that of the soft rubber layer is disposed on the surface of the soft rubber layer.

  In this pneumatic tire, since the protective rubber layer protects the surface of the soft rubber layer, there is an advantage that damage to the soft rubber layer (for example, trauma due to curbstone or the like) is suppressed.

  Moreover, the pneumatic tire according to the present invention is applied to a heavy load tire mounted on a front axle of a heavy load vehicle.

  In this pneumatic tire according to the present invention, when water droplets collide with the protrusion, the kinetic energy is absorbed by the soft rubber layer of the protrusion and is attenuated. Thereby, there is an advantage that the splash height (maximum value) of the water splash is reduced and the water splash suppression 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. 2 is a cross-sectional view in the tire meridian direction showing Modification 1 of the pneumatic tire depicted in FIG. 1. FIG. 3 is a cross-sectional view in the tire meridian direction showing Modification Example 2 of the pneumatic tire depicted in FIG. 1. FIG. 4 is a cross-sectional view in the tire meridian direction showing Modification 3 of the pneumatic tire depicted in FIG. 1. FIG. 5 is a cross-sectional view in the tire meridian direction showing Modification 4 of the pneumatic tire depicted in FIG. 1. FIG. 6 is a graph showing the results of the simulation of the pneumatic tire according to the embodiment of the present invention. FIG. 7 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.

  The pneumatic tire 1 includes a bead core (not shown), a carcass layer 3, a belt layer 4, a tread rubber 5, and a sidewall rubber 6 (see FIG. 1). The bead core has an annular structure and is configured as a pair of left and right. The carcass layer 3 is bridged in a toroidal shape between the left and right bead cores to form a tire skeleton. The belt layer 4 includes a plurality of stacked belt members 41 to 44 and is disposed on the outer periphery in the tire radial direction of the carcass layer 3. The tread rubber 5 is disposed on the outer circumference in the tire radial direction of the carcass layer 3 and the belt layer 4 to constitute a tread portion of the tire. The sidewall rubber 6 is configured as a pair of left and right sides, and is disposed on the outer side in the tire width direction of the carcass layer 3 to constitute a sidewall portion of the tire.

  Further, the tread portion (tread rubber 5) is formed with a plurality of circumferential main grooves 51 extending in the tire circumferential direction and a plurality of land portions 52 and 53 partitioned by the circumferential main grooves 51. Is done. In this embodiment, the circumferential main groove 51 located on the outermost side in the tire width direction has the deepest groove depth, and the circumferential main groove 51 causes the center land portion 52 and the shoulder land portion 53 of the tread portion to Is partitioned. The circumferential main groove means a circumferential groove having a groove depth of 8 mm or more.

[Protrusions for reducing water splash]
The pneumatic tire 1 includes a protrusion 7 for reducing water splash (see FIG. 1). This protrusion 7 is formed on the side wall portion located on the outer side in the vehicle width direction at least in the vehicle mounted state among the left and right side wall portions of the tire. In addition, the protrusion 7 has a shape protruding from the side wall in a cross-sectional view in the tire meridian direction, and includes a wall surface on the tire radial outer side (upper wall surface on the tread end side) and a wall surface on the inner side in the tire radial direction (side And a lower wall surface on the wall side. Further, the protrusion 7 is disposed in the vicinity of the end of the belt layer 4, a tangent line D1 drawn from the intersection K between the extension line of the outermost layer belt 44 and the side wall portion to the outer wall surface in the tire radial direction, and the tread from the intersection K. An angle β formed by a tangent line D2 drawn on the side wall surface on the end side is set to a predetermined opening degree. Moreover, the protrusion part 7 is comprised with the several element which separated the cyclic | annular and rib-like structure or space | interval extended in a tire peripheral direction along a side wall part.

  The side wall portion is a wall portion on the outer side in the tire width direction from the tread end portion to the sidewall portion in a cross-sectional view in the tire meridian direction, and corresponds to a so-called buttress portion. The protrusion 7 may be formed, for example, at the time of vulcanization molding of the tire, or may be attached by adhesion after the vulcanization molding of the tire.

  In the pneumatic tire 1, when traveling on a wet road surface, the protrusion 7 (particularly, the wall surface on the outer side in the tire radial direction) guides water droplets scattered in the tire width direction to suppress the scattering height of the water splashes. Thereby, for example, when traveling in rainy weather, it is possible to suppress splashing of water splashes on other vehicles traveling in the adjacent lane and the oncoming lane (spraying water splashes on the windshield of the passenger car and blocking the driver's view).

  Further, the protrusion 7 is arranged in the vicinity of the end of the belt layer 4 and the angle β formed by D1 and D2 is set to a predetermined opening, so that the tread portion (especially the tread rubber 5 and the belt layer) is The heat generated in 4) is released from the protrusion 7 to the outside of the tire. Thereby, since the raise of tire temperature is suppressed, the heat-resistant performance of a tire improves.

  For example, in this embodiment, the shape and arrangement of the protrusions 7 are set as follows.

  First, the ground contact end of the tread portion is A in the tire meridian cross-sectional view. In this embodiment, the ground contact end A and the tread end are in the same position. Further, a tangent line 1 is drawn from the grounding end A to the protrusion 7, and a contact point between the tangent line 1 and the protrusion 7 is T. Further, the inclination angle of the tangent line 1 with respect to the tire axial direction is α. Further, a curve m parallel to the profile of the tread surface is drawn from the groove bottom of the deepest circumferential main groove 51, and an intersection of the curve m and the side wall portion is defined as P.

  At this time, the top of the protrusion 7 has an arc-shaped contour line, and the contact T is located on the arc of the top. In addition, the wall surface on the outer side in the tire radial direction of the protruding portion 7 has an arc-shaped contour line that is concave on the tire inner side with respect to the tangent line l. Specifically, the wall surface on the tire radial direction outer side of the protruding portion 7 and the side wall surface on the tread end side are connected via an arc-shaped contour line that is concave on the tire inner side. The arc shape forms a wall surface that curves in the tire axial direction from the side wall surface on the ground contact end A side toward the contact point T. Further, the inclination angle α of the tangent line 1 is in the range of α <45 [deg], and more preferably in the range of 32 [deg] ≦ α ≦ 37 [deg]. And the guide direction (deflection direction) of the water splash at the time of wet road driving | running | working is controlled by the wall surface of the tire radial direction outer side of this protrusion part 7, and the scattering height of water splash is suppressed.

  The angle β formed by D1 and D2 is set to 60 degrees or more. Thereby, the heat generation in the tread portion during vehicle travel is configured to be efficiently released from the protrusion 7 to the outside of the tire.

  Further, the protrusion 7 is located on the inner side in the tire radial direction from the intersection P. Thereby, it is comprised so that the protrusion part 7 may remain | survive until a tread part is worn out and the wear indicator of the circumferential direction main groove 51 appears. Further, the height H of the protrusion 7 with respect to the wall surface of the sidewall portion is H = 12.5 [mm].

  The ground contact edge of a tire is a tire when a tire is attached to 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 is the “maximum air pressure” specified by JATMA. However, in the case of tires for passenger cars, the specified internal pressure is an air pressure of 180 kPa, and the specified load is 88% of the maximum load capacity. is there. The maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “INFLATION PRESSURES” defined in ETRTO. The specified load means “maximum load capacity” defined in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “LOAD CAPACITY” defined in ETRTO.

[Rubber hardness of protrusion]
Further, in the pneumatic tire 1, the protruding portion 7 includes a soft rubber layer (soft rubber portion) 71 having a JIS-A rubber hardness less than 55 degrees and smaller than the tread rubber 5 (see FIG. 1). In such a configuration, when water splashes collide with the protrusion 7, the kinetic energy is absorbed by the soft rubber layer 71 of the protrusion 7 and attenuates. Thereby, the splash height (maximum value) of the water splash is reduced, and the water splash suppression performance of the tire is improved.

  For example, in this embodiment, the entire protruding portion 7 and the side wall portion from the protruding portion 7 to the grounding end A are constituted by the soft rubber layer 71. Therefore, substantially the entire area of the buttress portion including the protrusion 7 is constituted by the soft rubber layer 71. Further, the JIS-A rubber hardness of the tread rubber 5 and the side wall rubber 6 is set to 58 degrees, and the JIS-A rubber hardness of the protrusion 7 is set to be smaller than 55 degrees.

  The soft rubber layer 71 preferably has a JIS-A rubber hardness of 35 degrees to 50 degrees, and more preferably a JIS-A rubber hardness of 40 degrees to 45 degrees. For example, if the JIS-A rubber hardness of the projection 7 is less than 35 degrees, it is difficult to manufacture the projection, or the structural strength of the projection is insufficient, and the projection is damaged. . Moreover, when the JIS-A rubber hardness of the protrusion 7 is 55 degrees or more, the effect of reducing water splash is not obtained, which is not preferable.

[Modification 1]
2 is a cross-sectional view in the tire meridian direction showing Modification 1 of the pneumatic tire depicted in FIG. 1. In the figure, the same components as those of the pneumatic tire 1 shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  In the pneumatic tire 1 of the first modification, the soft rubber layer 71 is disposed on the surface of the protrusion 7. For example, in the first modification, the soft rubber layer 71 extends from the top of the protruding portion 7 along the side wall portion on the outer side in the tire radial direction to the ground contact end A to form a surface layer in this region. Further, the thickness d of the soft rubber layer 71 is set within a predetermined range. Further, the soft rubber layer 71 is disposed so as to cover only the surface of the protruding portion 7 while leaving a core having a high rubber hardness (a part of the tread rubber 5) inside the protruding portion 7. Thereby, the structural strength of the protrusion 7 is ensured. In such a configuration, since the water splash directly collides with the soft rubber layer 71 on the surface of the protrusion 7, the kinetic energy is efficiently absorbed by the soft rubber layer 71 and attenuated. Thereby, the splash height of water splash decreases and the water splash suppression performance of a tire improves.

  In the above configuration, the thickness d of the soft rubber layer 71 is preferably in the range of 0 [mm] <d <7 [mm], preferably in the range of 1 [mm] ≦ d ≦ 5 [mm]. More preferably. Here, as the thickness d of the soft rubber layer 71 is thinner, the effect of reducing water splash tends to decrease, which is not preferable. Conversely, the thicker the thickness d, the less the structural strength of the protrusion due to the soft rubber layer tends to cause damage to the protrusion, which is not preferable. On the other hand, the lower the JIS-A rubber hardness of the soft rubber layer 71 is, the better in terms of improving the effect of reducing water droplets. However, the structural strength of the protrusions is insufficient, and the protrusions are easily damaged. There is also a problem. Therefore, the thickness d of the soft rubber layer 71 is preferably set as appropriate in relation to the JIS-A rubber hardness of the soft rubber layer 71.

  Moreover, in said structure, it is preferable that the soft rubber layer 71 is extended to the wall surface inside the tire radial direction of the projection part 7 (refer FIG. 2). For example, in this embodiment, the soft rubber layer 71 is disposed so as to wrap around the wall surface on the inner side in the tire radial direction while covering the top portion of the protrusion 7 from the wall surface on the outer side in the tire radial direction of the protrusion 7. In such a configuration, when there is a water droplet that travels along the tire radial direction and scatters along the protrusion 7, the kinetic energy of the water splash is on the soft rubber layer 71 on the wall surface in the tire radial direction of the protrusion 7. It is absorbed and attenuates. Thereby, the splash height of water splash decreases and the water splash suppression performance of a tire improves further.

  The maximum value of the distance between the tangent line 1 and the soft rubber layer 71 on the inner wall surface in the tire radial direction of the protrusion 7 (the position of the point C) is referred to as a wraparound amount t of the soft rubber layer 71. The wraparound amount t is preferably in the range of 0 [mm] <t ≦ 7 [mm], and more preferably in the range of 1 [mm] ≦ t ≦ 5 [mm]. That is, if there is a wraparound amount t to some extent, the soft rubber layer 71 appears on the wall surface on the inner side in the tire radial direction of the protrusion 7, so that the water splash suppression performance of the tire is improved. On the other hand, an excessive amount of wraparound t is not preferable because the structural strength of the protrusion is insufficient and damage to the protrusion is likely to occur.

[Modification 2]
FIG. 3 is a cross-sectional view in the tire meridian direction showing Modification Example 2 of the pneumatic tire depicted in FIG. 1. In the figure, the same components as those of the pneumatic tire 1 shown in FIGS. 1 and 2 are denoted by the same reference numerals, and the description thereof is omitted.

  In the pneumatic tire 1, the soft rubber layer 71 is preferably located on the inner side in the tire radial direction from the intersection point P defined by the maximum groove depth of the circumferential main groove 51 (see FIG. 3). For example, in the second modified example, the protrusion 7 is located on the inner side in the tire radial direction from the intersection P, and the soft rubber layer 71 extends from the intersection P along the wall surface on the outer side in the tire radial direction of the protrusion 7. The top of 7 is covered. In such a configuration, the soft rubber layer 71 is disposed at a position deviated from the wear range of the tread portion (the range from the wear of the tread portion until the wear indicator of the circumferential main groove 51 appears). Therefore, since the exposure of the soft rubber layer to the tread surface at the end of wear is prevented, uneven wear of the tread portion is prevented.

  In the above-described configuration, the soft rubber layer 71 may be disposed within the range from the intersection point P to the contact point T of the protrusion 7 and cover at least a part of the protrusion 7. Therefore, the soft rubber layer 71 may not reach the intersection point P.

  Moreover, it is preferable that the soft rubber layer 71 covers the top of the protrusion 7. Specifically, the soft rubber layer 71 is preferably disposed in a region including at least the contact T. Further, it is preferable that the soft rubber layer 71 extends from the contact point T to the outer side in the tire radial direction by 2 [mm] or more. For example, in this embodiment, the soft rubber layer 71 covers the top of the protrusion 7 and extends to the wall surface on the outer side in the tire radial direction of the protrusion 7 so that the contact T is positioned on the soft rubber layer 71. Yes. In such a configuration, since the soft rubber layer 71 is at the end portion (contact point T) of the protruding portion 7, the water splash suppression performance of the tire is effectively improved.

[Modification 3]
FIG. 4 is a cross-sectional view in the tire meridian direction showing Modification 3 of the pneumatic tire depicted in FIG. 1. In the figure, the same components as those of the pneumatic tire 1 described in FIGS. 1 to 3 are denoted by the same reference numerals, and the description thereof is omitted.

  This pneumatic tire 1 has an JIS-A rubber hardness smaller than that of the tread rubber 5 and larger than that of the soft rubber layer 71, and includes an intermediate rubber layer 72 disposed between the tread rubber 5 and the soft rubber layer 71. (See FIG. 4). For example, in Modification 3, the JIS-A rubber hardness of the tread rubber 5 is 58 degrees, the JIS-A rubber hardness of the intermediate rubber layer 72 is 50 degrees, and the JIS-A rubber hardness of the soft rubber layer 71 is 40 degrees. Then, an intermediate rubber layer 72 is disposed at an end portion (a portion corresponding to the buttress portion) of the tread rubber 5, and a soft rubber layer 71 is laminated on the surface of the intermediate rubber layer 72, thereby forming the protruding portion 7. . Further, the intermediate rubber layer 72 constitutes the basic portion (core portion) of the protruding portion 7, and the structural strength of the protruding portion 7 is secured by the intermediate rubber layer 72. Further, the intermediate rubber layer 72 extends from the ground contact end A beyond the protrusion 7 to the sidewall portion side. In addition, the soft rubber layer 71 has a substantially uniform thickness d, and extends from the ground contact end A to the protrusion 7 to cover the top of the protrusion 7.

  In such a configuration, the intermediate rubber layer 72 is disposed, so that the JIS-A rubber hardness at the protruding portion 7 gradually decreases from the surrounding tread rubber 5 toward the soft rubber layer 71. Thereby, when the difference in rubber hardness between the tread rubber 5 and the soft rubber layer 71 is large, the structural strength around the protrusion 7 can be secured. For example, in a configuration in which the intermediate rubber layer 72 has the same JIS-A rubber hardness as that of the soft rubber layer 71 (for example, see FIG. 1), the soft rubber layer 71 has a low JIS-A rubber hardness (for example, 35 degrees) and When the thickness d of the soft rubber layer 71 is large (for example, d = 7 [mm]), the structural strength of the protrusion may be insufficient.

  Further, in such a configuration, since the kinetic energy of water splash is absorbed by both the soft rubber layer 71 and the intermediate rubber layer 72, there is an advantage that the water splash suppression performance of the tire is effectively improved. For example, in the configuration in which the intermediate rubber layer 72 has the same JIS-A rubber hardness as that of the tread rubber 5 (for example, see FIG. 2), the soft rubber layer 71 has a high JIS-A rubber hardness (for example, 50 degrees) and is soft. When the thickness d of the rubber layer 71 is small (for example, d <1 [mm]), there is a possibility that the water splash suppression performance of the tire cannot be sufficiently obtained.

  In the third modification, the intermediate rubber layer 72 has a single-layer structure and has uniform JIS-A rubber hardness. However, the present invention is not limited thereto, and the intermediate rubber layer 72 may have a multilayer structure in which rubber materials having different JIS-A rubber hardnesses are laminated (not shown).

[Modification 4]
FIG. 5 is a cross-sectional view in the tire meridian direction showing Modification 4 of the pneumatic tire depicted in FIG. 1. In the figure, the same components as those of the pneumatic tire 1 described in FIGS. 1 to 4 are denoted by the same reference numerals, and the description thereof is omitted.

  In the pneumatic tire 1, it is preferable that a protective rubber layer 73 having a JIS-A rubber hardness larger than that of the soft rubber layer 71 is disposed on the surface of the soft rubber layer 71 (see FIG. 5). For example, in this modified example 4, the protective rubber layer 73 has a JIS-A rubber hardness of 58 degrees and is laminated on the surface of the soft rubber layer 71. Further, the soft rubber layer 71 extends from the top of the protrusion 7 to the grounding end A, and the protective rubber layer 73 wraps the surface side of the soft rubber layer 71 so as to cover the entire area of the soft rubber layer 71. Yes. In such a configuration, since the protective rubber layer 73 protects the surface of the soft rubber layer 71, damage to the soft rubber layer 71 (for example, trauma due to curbstone or the like) is suppressed.

  In addition, it is preferable that the thickness of the protective rubber layer 73 is set within a range of, for example, greater than 0 [mm] and 2 [mm] or less. Therefore, if there is the protective rubber layer 73, damage to the soft rubber layer 71 can be suppressed even if the thickness is small. On the other hand, if the thickness of the protective rubber layer 73 is too thick, the water splash suppression effect by the soft rubber layer 71 is lowered, which is not preferable.

[Applicable to]
In addition, it is preferable that this pneumatic tire 1 is applied to the heavy load tire with which the front axle of a heavy load vehicle is mounted | worn. In such heavy-duty tires, problems due to splashing water droplets are significant. Therefore, when the configuration of the pneumatic tire 1 is applied to the heavy load tire, there is an advantage that the water splash suppressing effect by the soft rubber layer 71 can be remarkably obtained.

[simulation]
FIG. 6 is a graph showing the results of the simulation of the pneumatic tire according to the embodiment of the present invention. In the figure, the horizontal axis indicates the reach distance (spatter distance) of the water splash in the tire axial direction, and the vertical axis indicates the maximum height of the water splash at each reach distance.

  In this simulation, a pneumatic tire having no protrusions, a pneumatic tire having protrusions but no soft rubber layer, and a pneumatic tire 1 having protrusions 7 and a soft rubber layer 71, water A comparison was made regarding splash suppression performance. It is also assumed that a pneumatic tire with a tire size of 275 / 80R22.5 is mounted on the front wheel of a truck after being mounted on a rim stipulated by JATMA, and a normal internal pressure and a normal load stipulated by JATMA are applied to this pneumatic tire. The simulation was done.

  Here, in a pneumatic tire having a protrusion but no soft rubber layer, the JIS-A rubber hardness of the tread rubber and the protrusion is set to the same 58 degrees.

  On the other hand, the pneumatic tire 1 having the protrusion 7 and the soft rubber layer 71 is the pneumatic tire 1 described in FIG. 2, and the soft rubber layer 71 is laminated on the surface of the protrusion 7 so that the top of the protrusion 7 is It extends to the grounding end A. The tread rubber 5 has a JIS-A rubber hardness of 58 degrees, and the soft rubber layer 71 has a JIS-A rubber hardness of 40 degrees. Further, the thickness d of the soft rubber layer 71 is set to d = 3 [mm].

  As shown in the simulation results, in the pneumatic tire 1 having the protrusions 7 and the soft rubber layer 71, it can be seen that the maximum height of water splash is reduced and the water splash suppression performance of the tire is improved.

[performance test]
FIG. 7 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  In this embodiment, the performance test regarding (1) water splash suppression performance and (2) durability performance was performed about the pneumatic tire 1 in which the protrusion 7 has the soft rubber layer 71. In this performance test, a pneumatic tire having a tire size of 275 / 70R22.5 is assembled to an applicable rim specified by JATMA, and a normal internal pressure and a normal load specified by JATMA are applied to the pneumatic tire. In addition, two pneumatic tires are mounted on the steer shaft of the 2-D route bus vehicle.

  The pneumatic tire 1 is the pneumatic tire 1 shown in FIG. 2, and a soft rubber layer 71 is laminated on the surface of the protruding portion 7 and extends from the top of the protruding portion 7 to the ground contact end A. The tread rubber 5 has a JIS-A rubber hardness of 58 degrees. And about this pneumatic tire 1, the JIS-A rubber hardness and thickness d of the soft rubber layer 71 are changed, and each performance test is performed.

  (1) In the performance test related to water splash suppression performance, the test vehicle travels on a watering path with a water depth of 10 [mm] at a running speed of 60 [km / h], and the maximum height of the generated water splash is measured. . And index evaluation is performed based on this measurement result. This evaluation is preferable as the numerical value increases.

  (2) In the performance test related to the durability performance, the damage occurrence rate when the pneumatic tire is rubbed against the curb is measured. The damage occurrence rate is preferably as the numerical value is smaller.

  As shown in the test results, it can be understood that the water splash suppression performance and the durability performance of the tire are improved by optimizing the JIS-A rubber hardness and the thickness d of the soft rubber layer 71.

[effect]
As described above, in the pneumatic tire 1, the protrusion 7 has a JIS-A rubber hardness of less than 55 degrees and smaller than the tread rubber 5 in the configuration including the protrusion 7 for reducing water splash on the side wall. The soft rubber layer 71 is provided (see FIGS. 1 to 5). In such a configuration, when water splashes collide with the protrusion 7, the kinetic energy is absorbed by the soft rubber layer 71 of the protrusion 7 and attenuates. Thereby, the splash height (maximum value) of the water splash is reduced, and there is an advantage that the water splash suppression performance of the tire is improved (see FIG. 6).

  Moreover, in this pneumatic tire 1, the soft rubber layer 71 is arrange | positioned on the surface of the projection part 7 (refer FIG. 2). In such a configuration, since the water splash directly collides with the soft rubber layer 71 on the surface of the protrusion 7, the kinetic energy is efficiently absorbed by the soft rubber layer 71 and attenuated. Thereby, there is an advantage that the splash height of the water splash is reduced and the water splash suppression performance of the tire is further improved.

  In the above configuration, the thickness d of the soft rubber layer 71 is in the range of 0 [mm] <d <7 [mm] (see, for example, FIG. 2). In such a configuration, since the thickness d of the soft rubber layer 71 is optimized, there is an advantage that both the water splash suppression performance and the durability performance of the tire are compatible (see FIG. 7).

  Moreover, in this pneumatic tire 1, the soft rubber layer 71 extends to the wall surface on the inner side (side wall portion side) in the tire radial direction of the protrusion 7 (for example, see FIG. 2). In such a configuration, the kinetic energy of water splash that travels inward in the tire radial direction through the protrusion 7 and is scattered is absorbed and attenuated by the soft rubber layer 71 extending to the inner wall surface of the protrusion 7 in the tire radial direction. To do. Thereby, there is an advantage that the splash height of the water splash is reduced and the water splash suppression performance of the tire is further improved.

  In the pneumatic tire 1, the curve m parallel to the profile of the tread surface is drawn from the groove bottom of the circumferential main groove 51 having the deepest groove depth among the circumferential main grooves 51 formed in the tread portion. When the intersection of the curve m and the side wall portion is P, the soft rubber layer 71 is on the inner side in the tire radial direction from the intersection P (see FIG. 3). In such a configuration, the soft rubber layer 71 is disposed at a position deviated from the wear range of the tread portion (the range from the wear of the tread portion until the wear indicator of the circumferential main groove 51 appears). Therefore, since the exposure of the soft rubber layer to the tread surface is prevented at the end of wear, there is an advantage that uneven wear of the tread portion is prevented.

  Further, in this pneumatic tire 1, when the tangent line 1 is drawn from the ground contact end A to the protruding portion 7 and the contact point between the tangent line 1 and the protruding portion 7 is T, the soft rubber layer 71 is at least in a region including the contact point T. It is preferable that the protrusions 7 are arranged (or the entire protrusion 7 is made of the soft rubber layer 71) (see, for example, FIGS. 1 to 3). In such a configuration, since the soft rubber layer 71 is at the end portion (contact point T) of the protruding portion 7, there is an advantage that the water splash suppression performance of the tire is effectively improved.

  Further, in the pneumatic tire 1, the intermediate rubber layer 72 having a JIS-A rubber hardness smaller than the tread rubber 5 and larger than the soft rubber layer 71 and disposed between the tread rubber 5 and the soft rubber layer 71. (See FIG. 4). In such a configuration, the intermediate rubber layer 72 is disposed, so that the JIS-A rubber hardness at the protruding portion 7 gradually decreases from the surrounding tread rubber 5 toward the soft rubber layer 71. Thereby, when the difference in rubber hardness between the tread rubber 5 and the soft rubber layer 71 is large, there is an advantage that the structural strength around the protrusion 7 can be secured. Moreover, since the kinetic energy of water splash is absorbed by both the soft rubber layer 71 and the intermediate rubber layer 72, there is an advantage that the water splash suppression performance of the tire is effectively improved.

  Moreover, in this pneumatic tire 1, the protective rubber layer 73 which has JIS-A rubber hardness larger than the soft rubber layer 71 is arrange | positioned on the surface of the soft rubber layer 71 (refer FIG. 5). In such a configuration, since the protective rubber layer 73 protects the surface of the soft rubber layer 71, there is an advantage that damage to the soft rubber layer 71 (for example, trauma due to a curb stone or the like) is suppressed.

  As described above, the pneumatic tire according to the present invention is useful in that it can improve the water splash suppression performance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 3 Carcass layer 4 Belt layer 41-44 Belt material 5 Tread rubber 51 Circumferential main groove 52 Center land part 53 Shoulder land part 6 Side wall rubber 7 Protrusion part 71 Soft rubber layer 72 Intermediate rubber layer 73 Protective rubber layer

Claims (9)

A pneumatic tire provided with a protrusion for reducing water splash on the side wall,
The pneumatic tire according to claim 1, wherein the protrusion includes a soft rubber layer having a JIS-A rubber hardness of less than 55 degrees and smaller than the tread rubber.   The pneumatic tire according to claim 1, wherein the soft rubber layer is disposed on a surface of the protrusion.   The pneumatic tire according to claim 2, wherein a thickness d of the soft rubber layer is in a range of 0 [mm] <d <7 [mm].   The pneumatic tire according to claim 2 or 3, wherein the soft rubber layer extends to a wall surface in the tire radial direction of the protrusion.   A curve m parallel to the profile of the tread surface is drawn from the groove bottom of the circumferential main groove having the deepest groove depth among the circumferential main grooves formed in the tread portion, and the intersection of the curve m and the side wall portion is defined as P. The pneumatic tire according to any one of claims 1 to 4, wherein the soft rubber layer is on the inner side in the tire radial direction from the intersection point P.   The tangent line 1 is drawn from the tire ground contact edge to the protrusion, and when the contact between the tangent l and the protrusion is T, the soft rubber layer is disposed in a region including at least the contact T. The pneumatic tire according to any one of the above.   The intermediate rubber layer which has a JIS-A rubber hardness smaller than the tread rubber and larger than the soft rubber layer and is disposed between the tread rubber and the soft rubber layer. Pneumatic tire described in one.   The pneumatic tire according to any one of claims 1 to 7, wherein a protective rubber layer having a JIS-A rubber hardness larger than that of the soft rubber layer is disposed on a surface of the soft rubber layer.   The pneumatic tire according to any one of claims 1 to 8, which is applied to a heavy duty tire mounted on a front axle of a heavy duty vehicle.

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