JP6635818B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  Patent Literatures 1 and 2 disclose a run flat tire in which a plurality of protrusions for air cooling are formed on a tire side portion. These projections are intended to turbulence the airflow on the tire side surface as the tire rotates. Due to the turbulence, the velocity gradient of the air flow in the vicinity of the surface of the tire side part is increased, and the improvement of the heat dissipation is improved.

International Publication No. WO2007 / 032405 International Publication No. WO2008 / 114668

  Patent Literatures 1 and 2 do not teach improvement of heat dissipation by a method other than turbulence of an air flow near the surface of a tire side portion.

  An object of the present invention is to improve durability of a pneumatic tire by effectively promoting heat radiation by air cooling.

  The present inventor has made various studies on maximizing the velocity gradient of the airflow near the surface of the tire side portion. It is known that when an object (for example, a flat plate) is placed in the flow of a fluid, the velocity of the fluid rapidly decreases near the surface of the object due to the viscosity of the fluid. A region where the velocity of the fluid is not affected by the viscosity is formed outside the region (boundary layer) where the velocity of the fluid changes rapidly. The thickness of the boundary layer increases downstream from the leading edge of the object. Although the boundary layer near the leading edge of the object is laminar (laminar boundary layer), it becomes turbulent toward the downstream side through a transition region (turbulent boundary layer). The present inventor has focused on the fact that the velocity gradient of the fluid is large in the laminar flow boundary layer, so that the efficiency of heat radiation from the object to the fluid is high, and completed the present invention. In other words, the inventor has conceived of applying the high heat dissipation in the laminar boundary layer to air cooling of a pneumatic tire. The present invention is based on such a new idea.

  The present invention includes a protrusion provided on the surface of the tire side portion, wherein the protrusion has a top surface, a front side surface that is a side surface on the front side in the tire rotation direction, and a front side portion where the top surface and the front side surface intersect. The thickness of the protrusion, which is the distance from the surface of the tire side portion to the top surface of the protrusion, is smaller than the width of the protrusion, which is a dimension of the top surface in the tire circumferential direction, The width of the protrusion is 10 mm or more, the gradient in the tire circumferential direction of the top surface at the front side is set so that the thickness of the protrusion increases with distance from the front side, Provide pneumatic tires.

  The projection has a shape whose thickness is smaller than the width, and when the pneumatic tire rotates, the airflow near the top surface of the projection becomes laminar. Since the laminar air flow (laminar flow boundary) has a large velocity gradient, heat dissipation by air cooling of the top surface of the projection is effectively promoted. Further, since the width of the protrusion is set to 10 mm or more, a heat radiation area of the protrusion due to the formation of the laminar flow is sufficiently secured. The inclination of the top surface of the protrusion at the front side in the tire circumferential direction is set so that the thickness of the protrusion increases as the distance from the front side increases. Due to this gradient, the separation of the air flow on the top surface near the front side can be suppressed or prevented, and the heat dissipation by the laminar flow can be reliably obtained.

  According to the pneumatic tire of the present invention, at the time of rotation, the airflow on the top surface of the projection formed on the surface of the tire side portion becomes laminar, so that heat dissipation by air cooling is effectively promoted and durability is improved. improves. In addition, the gradient in the tire circumferential direction of the top surface of the protrusion on the front side is set so that the thickness of the protrusion increases with distance from the front side, so that the air on the top surface near the front side is Separation of the flow can be suppressed or prevented, and the promotion of heat radiation by the laminar flow can be reliably obtained.

FIG. 1 is a meridional section of a pneumatic tire according to an embodiment of the present invention. 1 is a partial side view of a pneumatic tire according to an embodiment of the present invention. The elements on larger scale of FIG. The typical perspective view of a projection. FIG. FIG. 3 is a partial end view of a projection for explaining a tip angle. FIG. 4 is an end view of a projection for explaining a gradient of a top surface. FIG. 4 is a plan view of a projection for explaining a path of an air flow. FIG. 4 is an end view of a projection for explaining a path of an air flow. The schematic diagram for demonstrating the projection and the path | route of the airflow between projections. FIG. 4 is an end view of a projection for explaining a boundary layer. FIG. 4 is an end view of a projection for explaining a boundary layer. FIG. 4 is an end view of a projection for explaining an airflow flowing on a top surface when the end surface is a flat surface extending along the surface of the tire side portion. FIG. 4 is an end view of the protrusion of the embodiment for describing an airflow flowing on the top surface. FIG. 4 is an end view of a projection showing an alternative top surface shape. FIG. 4 is an end view of a projection showing an alternative top surface shape. FIG. 4 is an end view of a projection showing an alternative top surface shape. FIG. 4 is an end view of a projection showing an alternative top surface shape. FIG. 4 is an end view of a projection showing an alternative top surface shape. The partial side view of the pneumatic tire provided with the projection which has the inclination angle of the front part different from an embodiment. The elements on larger scale of FIG. The figure which shows the alternative of the shape of a protrusion in planar view. The figure which shows the alternative of the shape of a protrusion in planar view. The figure which shows the alternative of the shape of a protrusion in planar view. The figure which shows the alternative of arrangement | positioning of a protrusion. The figure which shows the alternative of arrangement | positioning of a protrusion. The figure which shows the alternative of arrangement | positioning of a protrusion. The figure which shows the alternative of arrangement | positioning of a protrusion. The figure which shows the alternative of the shape of a protrusion in end view. The figure which shows the alternative of the shape of a protrusion in end view. The figure which shows the alternative of the shape of a protrusion in end view. The figure which shows the alternative of the shape of a protrusion in end view. The figure which shows the alternative of the shape of a protrusion in end view. The figure which shows the alternative of the shape of a protrusion in end view. FIG. 3 is a perspective view of a projection provided with a vertical slit. FIG. 3 is a perspective view of a projection provided with a horizontal slit.

(1st Embodiment)
FIG. 1 shows a rubber pneumatic tire (hereinafter referred to as a tire) 1 according to a first embodiment of the present invention. The tire 1 of the present embodiment is a run flat tire of size 245 / 40R18. The invention can be applied to tires of different sizes. Further, the present invention can be applied to a tire that is not included in the category of the run flat tire. The rotation direction of the tire 1 is specified. The designated rotation direction is indicated by an arrow RD in FIG.

  The tire 1 includes a tread portion 2, a pair of tire side portions 3, and a pair of bead portions 4. Each bead portion 4 is provided at an inner end of the tire side portion 3 in the tire radial direction (an end opposite to the tread portion 2). A carcass 5 is provided between the pair of bead portions 4. A reinforcing rubber 7 is disposed between the carcass 5 and the inner liner 6 on the innermost peripheral surface of the tire 1. A belt layer 8 is provided between the carcass 5 and the tread of the tread portion 2. In other words, in the tread portion 2, the belt layer 8 is provided outside the carcass 5 in the tire radial direction.

  Referring to FIGS. 2 and 3, a plurality of protrusions 11 are provided on the surface of the tire side portion 3 at intervals in the tire circumferential direction. In the present embodiment, the shapes, dimensions, and postures of these projections 11 are the same. In FIG. 1, the distance (tire height) from the outermost peripheral position P1 of the rim (not shown) to the outermost position in the tire radial direction of the tread portion 1 is indicated by a symbol TH. The protrusions 11 can be provided in a range from 0.05 to 0.7 times the tire height TH from the outermost peripheral position P1 of the rim.

  In the present specification, the term “plan view” or a similar term may be used for the shape of the protrusion 11 viewed from the tire width direction, and the term “end view” or the term Similar terms may be used.

  Referring to FIGS. 4 and 5, the protrusion 11 has a top surface 12 that extends along the surface of the tire side portion 3. In the present embodiment, the top surface 12 has a blade cross-sectional shape when viewed from the end. Further, the projection 11 includes a pair of side surfaces facing each other in the tire circumferential direction, that is, a front side surface 13 and a rear side surface 14. The front side surface 13 is located on the front side in the tire rotation direction RD, and the rear side surface 14 is located on the rear side in the tire rotation direction RD. Further, the projection 11 has a pair of end surfaces facing each other in the tire radial direction, that is, an inner end surface 15 inside in the tire radial direction and an outer end surface 16 outside in the tire radial direction. As described later in detail, the front side surface 13 in the present embodiment is a flat surface inclined with respect to the surface of the tire side portion 3 and the top surface 12. The rear side surface 14, the inner end surface 15, and the outer end surface 16 in the present embodiment are flat surfaces extending substantially perpendicular to the surface of the tire side portion 3.

  The front side portion 17 is a portion where the top surface 12 and the front side surface 13 cross each other, and the rear side portion 18 is a portion where the top surface 12 and the rear side surface 14 cross each other. The inner side portion 19 is a portion where the top surface 12 and the inner end surface 15 cross each other, and the outer side portion 20 is a portion where the top surface 12 and the outer end surface 16 cross each other. The front side portion 17, the rear side portion 18, the inner side portion 19, and the outer side portion 20 may have a sharp or clear edge as in the present embodiment, but have a shape curved to some extent in end view. May be. In the present embodiment, the shapes of the front side 17, the rear side 18, the inner side 19, and the outer side 20 in plan view are all linear. However, the shape in plan view may be a curved line including a circular arc and an elliptical arc, a broken line composed of a plurality of straight lines, or a combination of a straight line and a curved line.

  Referring to FIG. 3, the front side 17 is inclined with respect to a straight line extending in the tire radial direction passing through the front side 17 in a plan view. In other words, the front side 17 is inclined with respect to the tire radial direction. The inclination angle a1 of the front side portion 17 with respect to the tire radial direction is a reference straight line Ls extending in the tire front direction in the tire rotation direction RD of the front side portion 17 and extending in the tire radial direction, and a direction in which the front side portion 17 extends. In the present embodiment, the angle is defined as an angle (clockwise in plan view is defined as positive) formed by the front side 17 itself which is a straight line.

  The front side portion 17 in the present embodiment extends rightward in plan view. As shown in FIG. 16 and FIG. 17, the protrusion 11 may have a shape in which the front side portion 17 extends to the lower right in plan view. The rear side portion 18 of the present embodiment extends substantially parallel to the front side portion 17 in plan view. Further, the inner side portion 19 and the outer side portion 20 of the present embodiment extend in parallel with each other in plan view.

  Referring to FIG. 3, reference symbol R indicates a tire radius, and reference symbol Rp indicates a distance from the tire rotation center at an arbitrary position of the protrusion 11 in the tire radial direction. 3 indicates the distance from the center of rotation of the tire to the center pc of the protrusion 11 (for example, the centroid of the top surface 12 in plan view). Further, the reference symbol hRp in FIG. 3 indicates the dimension of the protrusion 11 in the tire circumferential direction at an arbitrary position in the tire radial direction, that is, the width of the protrusion 11. The symbol hRpc in FIG. 3 indicates the width of the protrusion 11 at the center pc of the protrusion.

  5 and 7, when viewed from the end, the top surface 12 of the projection 11 has a shape protruding or bulging outward in the tire width direction (direction away from the surface of the tire side portion 3). Specifically, as described above, the end face of the projection 11 of the present embodiment has a wing cross-sectional shape when viewed from the end face. Therefore, the thickness tRp of the protrusion 11 at an arbitrary position in the tire radial direction of the protrusion 11 has a distribution in the tire circumferential direction. That is, the thickness tRp of the protrusion 11 varies between the front side surface 13 (front side portion 17) and the rear side surface 14 (rear side portion 18). 5 and 7, the position of the top surface 12 where the thickness tRp is the largest is indicated by a reference symbol P3 in the end view.

  Referring to FIG. 7, in a region of the top surface 12 of the protrusion 11 from the front side portion 17 to the position P3, the gradient of the top surface 12 in the tire circumferential direction increases as the top surface 12 moves away from the front side portion 17 (position P3). , The thickness hRp of the protrusion 11 is set to gradually increase. In the region from the position P3 to the rear edge 18 of the top surface 12 of the projection 11, the gradient of the top surface 12 in the tire circumferential direction increases as the distance from the position P3 increases (as the distance approaches the rear edge 18). T), the thickness hRp of the protrusion 11 is set so as to gradually decrease. At the position P3, the gradient of the top surface 12 in the tire circumferential direction is 0 °. In particular, the gradient θ1 in the tire circumferential direction of the top surface 12 at the front side 17 is set upward from the front side 17 toward the position P3. Specifically, the gradient θ1 can be set to 5 ° or more and 85 ° or less. Further, the gradient θ2 of the top surface 12 in the tire circumferential direction at the rear side portion 18 is set downward from the position P3 side toward the rear side portion 18. Specifically, the gradient θ2 can be set to −30 ° or more and −5 ° or less. The slope in the tire circumferential direction of the top surface 12 of the protrusion 11 is defined as an inclination angle with respect to a perpendicular line (horizontal line Lh) extending in the tire radial direction passing through a point on the top surface 12 whose slope is measured in end view. As shown in FIG. 7, the sign of the gradient is positive in the counterclockwise direction when the inner end face 15 of the projection 11 is viewed from the inside in the tire radial direction.

  In the present embodiment, the thickness tRp of the projection 11 at an arbitrary position on the top surface 12 in the tire radial direction is constant from the inner end surface 15 to the outer end surface 16. That is, the thickness tRp of the projection 11 is uniform in the tire radial direction.

  Referring to FIGS. 5 and 6, when viewed from the end surface, the top surface 12 of the protrusion 11 and the front side surface 13 form an angle (tip angle a2) at the front side portion 17. The front side surface 13 in the present embodiment has a slope such that the top surface 12 and the front side surface 13 have a tapered shape in which the interval decreases toward the front side portion 17. In other words, the inclination of the front side surface 13 is set such that the lower end of the front side surface 13 is located rearward of the front side portion 17 in the tire rotation direction RD in end view. Since the front side surface 13 has such an inclination, the tip angle a2 of the protrusion 11 of the present embodiment is an acute angle (45 °). The specific definition of the tip angle a2 will be described later.

  Referring to FIGS. 8 to 10, when the vehicle equipped with the tire 1 travels, the airflow flowing into the projection 11 from the front side 17 side near the surface of the tire side portion 3 is conceptually indicated by an arrow AF0. Occurs. Referring to FIG. 8, the airflow AF0 at a specific position P2 on the surface of the tire side portion 3 is an angle (inflow angle afl) with respect to a perpendicular (horizontal line Lh) drawn from a straight line extending in the tire radial direction passing through the position P2. Having. According to the analysis performed by the inventor, under the condition that the distance Rpc of the center Pc of the tire side 245 / 40R18, the center Pc of the protrusion 11 from the center of rotation of the tire is 550 mm, and the running speed of the vehicle is 80 km / h, the inflow angle afl is 12 °. It is. When the traveling speed changes in the range of 40 to 120 km / h, the inflow angle afl changes by about ± 1 °. At the time of actual use, in addition to the traveling speed, there are influences due to various factors including a head wind, a structure of the vehicle, and the like. Therefore, the inflow angle afl under the above-described conditions can be regarded as about 12 ± 10 °.

  8 to 10, the airflow AF1 flows into the protrusion 11 from the front side portion 17, and is divided into two airflows at the time of the inflow. As shown most clearly in FIG. 8, one airflow AF1 rides on the top surface 12 from the front side surface 13 and flows along the top surface 12 from the front side portion 17 to the rear side portion 18 (main airflow). Flow). The other airflow AF2 is guided by the front side surface 13 and flows outward in the tire radial direction along the surface of the tire side portion 3 (subordinate airflow). As shown in FIG. 12 and FIG. 13, when the front side portion 17 is lower right in plan view, the airflow AF2 is guided by the front side surface 13 and flows inward in the tire radial direction along the surface of the tire side portion 3.

  Referring also to FIG. 11, the air flow AF1 flowing along the top surface 12 of the projection 11 is laminar. That is, the laminar flow boundary layer LB is formed near the top surface 12 of the projection 11. In FIG. 11, reference numeral Va conceptually shows the velocity gradient of the airflow AF0 and the airflow AF1 near the surface of the tire side portion 3 and near the top surface 12 of the projection 11. Since the velocity of the laminar airflow AF1 is large, heat is radiated from the top surface 12 of the projection 11 to the airflow AF1 with high efficiency. In other words, since the airflow AF2 on the top surface 12 of the projection 11 becomes laminar, heat dissipation by air cooling is effectively promoted. By performing the air cooling effectively, the durability of the tire 1 is improved.

  As shown by an arrow AF3 in FIG. 10, the airflow passing through the top surface 12 and flowing downstream from the rear side portion 18 falls from the top surface 12 toward the surface of the tire side portion 3. The airflow AF3 collides with the surface of the tire side portion 3. As a result, the airflow in the area TA near the surface of the tire side portion 3 becomes turbulent between the adjacent protrusions 11 and 11. In this region TA, heat dissipation from the surface of the tire side portion 3 is promoted by an increase in the speed gradient due to the turbulence of the air flow.

  As described above, in the tire 1 of the present embodiment, the heat dissipation of the tire 1 is caused by both the laminarization of the airflow AF1 on the top surface 12 of the projection 11 and the turbulence of the airflow AF3 between the projections 11, 11. Have improved.

  As will be described in detail later, the width hRp of the protrusion 11 at a distance Rp from the center of rotation of the tire (see FIG. 3) is set so that the laminar flow boundary layer LB extends to the rear edge 18 of the top surface 12 of the protrusion 11. Is preferred. However, as conceptually shown in FIG. 12, the width hRp of the projection 11 is such that the velocity boundary layer becomes the transition region TR or the turbulent boundary layer TB on the rear side 18 side of the top surface 12 of the projection 11. Relatively long dimensions are also acceptable. Even in such a case, in the region of the top surface 12 of the projection 11 where the laminar flow boundary layer LB is formed, the advantage of improving heat dissipation can be obtained due to a large velocity gradient.

  13 and 14, when viewed from the tire radial direction, the direction of the airflow AF0 flowing into the protrusion 11 is not parallel to the surface of the tire side portion 3 but slightly upward, that is, the surface of the tire side 3. Slightly inclined away from Therefore, as shown in FIG. 13, if the top surface 12 of the protrusion 11 is a flat surface that extends in parallel along the surface of the tire side portion 3, the airflow AF1 flowing through the top surface 12 is close to the front side portion 17. May cause peeling PE. When the peeling PE occurs, the air flow AF1 becomes turbulent, and the heat radiation efficiency from the top surface 12 decreases. Referring to FIGS. 7 and 14, in the present embodiment, as described above, the gradient θ1 of the top surface 12 at the front side 17 is set to be upward, so that the air flows from the front side 17 toward the position P3. The flow AF1 flows smoothly along the top surface 12, and the separation PE can be suppressed or prevented. Therefore, by setting the gradient θ1 of the top surface 12 at the front side portion 17 to be upward, the heat dissipation can be reliably promoted by the laminar flow. Referring also to FIG. 5, in order to reliably prevent the separation of the airflow AF <b> 1, the position P <b> 3 where the gradient of the top surface 12 becomes 0 is set closer to the front side 17 than half the width hRp of the protrusion 12. Is preferred.

  Referring to FIGS. 7 and 14, the gradient θ2 of the top surface 12 at the rear side portion 18 is set downward as described above. Therefore, the airflow AF3 flowing downstream beyond the rear side portion 18 surely falls from the top surface 12 toward the surface of the tire side portion 3 (see FIG. 10). As a result, a turbulent region TA is reliably formed between the adjacent protrusions 11, 11, and heat dissipation from the surface of the tire side portion 3 due to the turbulence of the airflow AF <b> 3 is reliably obtained.

  In order to cause the airflow AF0 to be divided into the airflows AF1 and AF2 when flowing into the protrusion 11 described above, the thickness tRp of the protrusion 11, particularly, the thickness tRp at the front side portion 17 is determined by the thickness of the protrusion 11. It is preferable that the width is smaller than the width hp (the minimum width when the width hp is not constant).

  As described above, the airflow AF0 flowing into the projection 11 has the inflow angle afl. In order to cause the airflow AF0 to be divided into the airflows AF1 and AF2, the inclination angle a1 of the front side portion 17 of the projection 11 in a plan view is set to 90 ° and the entrance angle of the airflow AF0 with respect to the front side portion 17 is 90 °. It is necessary to set so that it does not become. In other words, it is necessary to incline the front side 17 of the projection 11 with respect to the airflow AF0 in plan view.

  Referring to FIG. 3, as in the present embodiment, when the front side 17 rises to the right in plan view, the front side 17 intersects the airflow AF0 flowing into the front side 17 at 45 °. It is more preferable that the setting is made to be performed. In this case, as described above, since the inflow angle afl of the airflow AF0 can be regarded as about 12 ± 10 °, the inclination angle a1 of the front side portion 17 is set within the range defined by the following equation (1). Is preferred.

  Referring to FIG. 17, when the front side 17 is inclined rightward, the inclination angle a1 of the front side 17 is set so as to intersect with the airflow AF0 flowing into the front side 17 at 45 °. Is preferably set within the range defined by the following equation (2).

  In short, it is preferable that the inclination angle of the front side portion 17 be set so as to satisfy Expression (1) or (2).

  Referring to FIGS. 5 and 6, in order to cause the air flow AF0 to be divided into the air flows AF1 and AF2 when flowing into the protrusion 11, the tip angle a2 of the protrusion 11 must not be set too large. . Specifically, the tip angle a2 is preferably set to 100 ° or less. More preferably, the tip angle a2 is set to an acute angle, that is, less than 90 °. An excessively small tip angle a2 is not preferable because it causes a decrease in the strength of the projection 11 near the front side portion 17. Therefore, it is preferable that the tip angle a2 is set in a range of 45 ° to 65 °.

  Referring to FIG. 3, if the width hRp of the protrusion 11 at an arbitrary position in the tire radial direction is excessively small, the heat release area from the protrusion 11 due to the laminar boundary layer LB near the top surface 12 is insufficient, and the heat release due to the laminar flow is performed. The promotion effect cannot be sufficiently obtained. Therefore, it is preferable to set the width hRp of the protrusion 11 to 10 mm or more.

  With continued reference to FIG. 3, it is preferable that the width hRp of the protrusion 11 at an arbitrary position in the tire radial direction be set so as to satisfy the following expression (3). All equations in the following description use the SI unit system.

Ｒ：タイヤ半径Ｒ
Ｒｐ：突起上の任意の位置のタイヤ回転中心からの距離
ｈＲｐ：タイヤ回転中心からの距離Ｒｐにおける突起の幅

R: tire radius R
Rp: distance from the tire rotation center at an arbitrary position on the protrusion hRp: width of the protrusion at a distance Rp from the tire rotation center

  If the width hRp is too small, a region where the speed gradient increases cannot be sufficiently secured, and a sufficient cooling effect cannot be obtained. The lower limit value 10 in the equation (3) corresponds to the minimum necessary heat radiation area for securing the heat radiation promotion effect by the laminar flow.

  If the width hRp is too large, the velocity boundary layer grows excessively on the projections 11, and the velocity gradient becomes small, so that the heat radiation property deteriorates. The upper limit value 50 in the equation (3) is defined from such a viewpoint. Hereinafter, the reason why the upper limit is set to 50 will be described.

  It is known that the development of the velocity boundary layer on a flat plate, that is, the transition from the laminar boundary layer LB to the turbulent boundary layer TB is represented by the following equation (4).

ｘ：層流境界層から乱流境界層への遷移が生じる平板先端からの距離
Ｕ：流入速度
ν：流体の動粘性係数

x: distance from the tip of the flat plate at which transition from laminar boundary layer to turbulent boundary layer occurs U: inflow velocity ν: kinematic viscosity coefficient of fluid

  Considering the influence of the turbulence of the main flow and the fact that the velocity gradient decreases due to the growth of the boundary layer to some extent near the transition region, the maximum value hRp_max of the width hRp of the protrusion 11 necessary for obtaining a sufficient cooling effect is: , The distance x in Expression (4). Therefore, the maximum width hRp_max of the protrusion 11 is represented by the following equation (5).

  The inflow velocity U of the fluid into the protrusion 11 is expressed as the product of the distance Rp of the protrusion 11 at an arbitrary position in the tire radial direction from the center of rotation of the tire and the tire angular velocity (U = Rpω). The vehicle speed V is expressed as a product of a tire radius R and a tire angular speed (V = Rω). Therefore, the following equation (6) holds.

  The following equation (7) holds for the kinematic viscosity coefficient ν of air.

  By substituting the equations (6) and (7) into the equation (5), the following equation (8) is obtained.

  Assuming that the vehicle speed V is 80 km / h, hRp_max is as follows from Expression (8).

  In high-speed running when the heat generation of the tire 1 becomes more remarkable, specifically, when the vehicle speed V is considered up to 160 km / h, hRp_max is as follows from Expression (8).

  As described above, even when the vehicle is traveling at a high speed (at a vehicle speed V of 160 km / h or less), the laminar boundary layer LB is formed in the entire width direction of the top surface 12 of the projection 11 by the following equation (3). Is 50.

  15A to 15E show various alternatives of the shape of the top surface 12 of the projection 11 in end view.

  The projection 11 in FIG. 15A has an arc-shaped top surface 12 in end view.

  The projection 11 in FIG. 15B has a curved top surface 12 that is neither a wing cross-sectional shape nor an arc shape in end view.

  The projection 11 in FIG. 15C has a top surface 12 composed of two flat surfaces 41 and 42 inclined in the tire circumferential direction with respect to the surface of the tire side portion 3. The flat surface 41 from the front side portion 17 to the position P3 where the thickness hRp of the protrusion 11 is maximum has a constant upward slope. The flat surface 42 from the position P3 to the rear side portion 18 has a constant downward slope. The position P3 is set closer to the front side 17 than half the width hRp of the protrusion 12.

  The top surface 12 of the projection 11 shown in FIG. 15D has two flat surfaces 51, 53 inclined in the tire circumferential direction with respect to the surface of the tire side portion 3, and one flat surface 51 extending parallel to the surface of the tire side portion 3. It is constituted by a flat surface 52. The flat surface 51 from the front side portion 17 to the position P3 where the thickness hRp of the protrusion 11 is maximum has a constant upward slope. The flat surface 52 extends from the position P3 to the rear side portion 18 side. The flat surface 53 extends from the end on the rear side 18 side of the flat surface 52 to the rear side 18. The position P3 is set closer to the front side 17 than half the width hRp of the protrusion 12.

  The top surface 12 of the projection 11 shown in FIG. 15E is constituted by a single flat surface inclined in the tire circumferential direction. End face 12 has a constant upward slope.

  15A to 15D, the gradient θ1 of the end surface 12 at the front side 17 and the gradient θ2 of the end surface 12 at the rear side 18 are set in the same manner as in the present embodiment (for example, FIG. 7). In the alternative of FIG. 15E, the gradient θ1 of the end face 12 at the front side 17 is set in the same manner as in the present embodiment.

  16 to 19D show various alternatives of the shape of the projection 11 in plan view.

  The projection 11 in FIGS. 16 and 17 has the front side 17 extending upward to the right in plan view as described above.

  The rear side portion 18 of the projection 11 in FIG. 18A has a shape in plan view constituted by two straight lines having different inclination angles.

  The projections 11 in FIGS. 18B and 18C have a shape in plan view in which the front side portion 17 extends rightward and the rear side portion 18 extends rightward and downward. In particular, the projection 11 of FIG. 18C has a shape in plan view of an equilateral trapezoidal shape.

  In FIG. 19A, two types of protrusions 11 having different widths hRp are alternately arranged on the surface of the tire side portion 3.

  In FIGS. 19B and 19C, two types of protrusions 11 having different inclination angles a1 of the front side portion 17 are alternately arranged on the surface of the tire side portion 3. In FIG. 19B, each of the two types of protrusions 11 has a front side 17 that rises to the right. In FIG. 19C, one of the two types of protrusions 11 has a front side 17 rising rightward, and the other protrusion 11 has a front side 17 falling rightward.

  In FIG. 19D, two types of protrusions 11 having different positions in the tire radial direction are alternately arranged on the surface of the tire side portion 3.

  FIGS. 20A to 21B show various alternatives regarding the shape of the front side surface 13 of the projection 11 in end view.

  The front side surface 13 of the projection 11 shown in FIGS. 20A to 20D forms one recess 23 when viewed from the end.

  The front side surface 13 of the projection 11 in FIG. 20A is constituted by two flat surfaces 24a and 24b. In the end view, the flat surface 24a is lower right and the flat surface 24b is upper right. A triangular depression 23 is formed by these flat surfaces 24a and 24b in an end view.

  The front side surface 13 of the protrusion 11 in FIG. 20B is configured by a curved surface having a semicircular cross-sectional shape. The curved surface forms a semicircular depression 23 when viewed from the end.

  The front side surface 13 of the protrusion 11 in FIG. 20C is configured by a flat surface 25a which is lower right when viewed from the end, and a curved surface 25b having an arc-shaped cross-sectional shape. The flat surface 25 a is located on the top surface 12 side of the projection 11, and the curved surface 25 b is located on the surface side of the tire side portion 3. A depression 23 is formed by the flat surface 25a and the curved surface 25b.

  The front side surface 13 of the projection 11 in FIG. 20D is constituted by three flat surfaces 26a, 26b, 26c. In the end view, the flat surface 26a on the top surface 12 side of the projection 11 is lowered to the right, the flat surface 26c on the front surface side of the tire side portion 3 is raised to the right, and the central flat surface 26b extends in the tire radial direction. Polygonal depressions 23 are formed by these flat surfaces 26a to 26c.

  The front side surface 13 of the projection 11 shown in FIG. 21A and FIG. 21B constitutes two recesses 23A and 23B arranged adjacently in the tire radial direction when viewed from the end.

  The front side surface 13 of the projection 11 in FIG. 21A is constituted by four flat surfaces 27a to 27d. When viewed from the end, the flat surface 27a on the top surface 12 side of the projection 11 is downward-sloping, and the flat surface 27b rising rightward, the flat surface 27c falling rightward, and the flat surface rising rightward toward the surface of the tire side portion 3. The surfaces 27d are arranged in order. The flat surfaces 27a and 27b form a single depression 23A having a triangular cross-sectional shape on the top surface 12 side of the projection 11, and the depression 23A is adjacent to the surface side of the tire side portion 3 and similarly has a triangular shape. Is formed by the flat surfaces 27c and 27d.

  The front side surface 13 of the projection 11 in FIG. 21B is constituted by two curved surfaces 28a and 28b having a semicircular cross-sectional shape. A single concave portion 23A having a semicircular cross-sectional shape is formed by the curved surface 28a on the top surface 12 side of the projection 11, and a semicircular shape is formed adjacent to the concave side 23A on the surface side of the tire side portion 3. Is formed by the curved surface 28b.

  The front side surface 13 of the projection 11 may form three or more depressions arranged adjacent to each other in the tire radial direction when viewed from the end.

  The air flow AF1 flowing along the top surface 12 of the protrusion 11 and the front surface 13 of the protrusion 11 The flow rate ratio of the airflow AF2 flowing along can be adjusted.

  One projection 11 may be formed by combining any one of the shapes of the top surface 12 in FIGS. 15A to 15E and any of the shapes of the front side surface 13 in FIGS. 20A to 21B.

  Referring to FIGS. 5 and 15A to 15E and FIGS. 20A to 21B, an angle formed between the top surface 12 of the protrusion 11 and the front side surface 13 in the front side portion 17, that is, a tip angle a2 of the protrusion 11 , The straight line Lt corresponding to the top surface 12 and the straight line Lfs corresponding to the portion near the front side 17 of the front side surface 13.

  The straight line Lt is defined as a straight line that passes through the portion (position P3) of the top surface 12 where the thickness tRp is the largest and extends along the surface of the tire side portion 3. Referring to FIG. 5, FIG. 15A, FIG. 15B, and FIG. 20A to FIG. 21B, when the top surface 12 is a curved surface, it passes through the position P3 where the thickness tRp is the largest among the top surfaces 12 in end view, and the tire side portion 3 Is a straight line Lt. Referring to FIGS. 15C, 15D, and 15E, when the end face 12 is constituted by a plurality or a single inclined flat face, a straight line obtained by extending a portion near the front side 17 in end view is obtained. , A straight line Lt.

  Referring to FIG. 5 and FIGS. 15A to 15E, when the front side surface 13 is formed of a single flat surface, a straight line obtained by extending the front side surface 13 itself in end view is a straight line Lfs. Referring to FIGS. 20A to 20D, when the front side surface 13 forms a single depression 23, a straight line connecting the front side portion 17 and the most depressed position of the depression 23 in an end view is a straight line Lfs. is there. Referring to FIGS. 21A and 21B, when a plurality of (two in these examples) recesses 23 </ b> A and 23 </ b> B are configured, the front side 17 and the recess 23 </ b> A located closest to the top surface 12 are viewed from the end face. The straight line connecting the most depressed position is the straight line Lfs.

(Other embodiments)
Referring to FIG. 22, if the formation of the laminar flow on the top surface 12 is not significantly impaired, one protrusion 11 is arranged in the tire circumferential direction by one longitudinal slit 33 extending in the tire radial direction. It may be divided into independent parts. One protrusion 11 may be divided into three or more independent portions by two or more vertical slits 33.

  Referring to FIG. 23, if the formation of laminar flow on the top surface 12 is not significantly impaired, one protrusion 11 is arranged in the tire radial direction by one transverse slit 34 extending in the tire circumferential direction. It may be divided into independent parts. One projection 11 may be divided into three or more parts by two or more vertical slits 34.

  By providing one or more vertical slits 33 and one or more horizontal slits 34, one projection 11 may be divided into four or more parts.

  The depths of the vertical slits 33 and the horizontal slits 34 may be set so that these slits 33 and 34 extend from the top surface 12 to the surface of the tire side portion 3, as shown in FIGS. The slits 33 and 34 may be set so as not to reach the surface of the tire side portion 3.

REFERENCE SIGNS LIST 1 tire 2 tread portion 3 tire side portion 4 bead portion 5 carcass 6 inner liner 7 reinforcing rubber 8 belt layer 11 protrusion 12 top surface 13 front side surface 14 rear side surface 15 inner end surface 16 outer end surface 17 front side portion 18 rear side portion 19 inside Side 20 Outer side 23, 23A, 23B Depression 24a, 24b, 25a, 26a to 26c, 27a to 27d Flat surface 25b, 28a, 28b Curved surface 31 Ridge 32 Groove 33 Vertical slit 34 Horizontal slit 41, 42, 51, 52, 53, 61 Flat surface RD Rotation direction P1 Outermost peripheral position of rim P2 Specific point on surface of tire side part P3 Position where top surface has maximum thickness Ls Reference straight line Lt, Lfs straight line Lh Horizontal line AF0, AF1, AF2 Air Flow Va velocity of air flow LB laminar boundary layer TR transition region TB turbulent boundary layer TA turbulent region 1, .theta.2 gradient PE peeling

Claims (7)

With a projection provided on the surface of the tire side part,
The protrusion includes a top surface, a front side surface that is a side surface on the front side in the tire rotation direction, and a front side portion where the top surface and the front side surface intersect,
The thickness of the protrusion, which is the distance from the surface of the tire side portion to the top surface of the protrusion, is smaller than the width of the protrusion, which is the dimension of the top surface in the tire circumferential direction,
The width of the protrusion is 10 mm or more;
The pneumatic tire, wherein a slope of the top surface in the tire circumferential direction at the front side is set such that a thickness of the protrusion increases as the distance from the front side increases.   The pneumatic tire according to claim 1, wherein the gradient is not less than 5 ° and not more than 85 °. The protrusion includes a rear side surface facing the front side surface and the tire circumferential direction, and a rear side portion where the top surface and the rear side surface intersect,
The gradient of the top surface in the tire circumferential direction at the rear side portion is set such that the thickness of the protrusion becomes smaller as approaching the rear side portion. Pneumatic tires. The pneumatic tire according to any one of claims 1 to 3, wherein the width of the protrusion satisfies the following.

R: Tire radius R
Rp: Distance from tire rotation center at any position on protrusion
hRp: Width of protrusion at distance Rp from tire rotation center   The pneumatic tire according to any one of claims 1 to 4, wherein the front side has an inclination with respect to a straight line extending in the tire radial direction passing through the front side when viewed from the tire width direction. . The pneumatic tire according to claim 5, wherein an inclination angle of the front side portion of the protrusion as viewed from the tire width direction satisfies the following.

  The pneumatic tire according to any one of claims 1 to 6, wherein a tip angle, which is an angle formed between the top surface and the front side surface at the front side portion of the protrusion, is 100 ° or less.

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