JP2017144787A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively facilitate heat radiation by air cooling to enhance durability of a tire.SOLUTION: A pneumatic tire 1 comprises projections 11 arranged on a surface of a tire side part 3. Each of the projections 11 includes: a top surface 12; a front side surface 13, which is a side surface on a front side of a tire rotational direction RD; and a front edge part 17 where the top surface 12 and the front side surface 13 intersect. A thickness tRp of the projection 11, which is a distance from a surface of the tire side part 3 to the top surface 12 of the projection 11, is less than a width hRp of the projection 11, which is a tire circumferential direction of the top surface 12. The width hRp of the projection 11 is equal to or greater than 10 mm. An inclination θ1 in the tire circumferential direction of the top surface 12 at the front edge part 17 is configured to increase the thickness tRp of the projection as separating from the front edge part 17.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a pneumatic tire.

  Patent Documents 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 protrusions are intended to make the airflow on the surface of the tire side part turbulent as the tire rotates. The turbulent flow increases the velocity gradient of the air flow in the vicinity of the surface of the tire side portion, improving the heat dissipation.

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

  Patent Documents 1 and 2 do not teach improvement of heat dissipation by a method other than turbulent airflow near the tire side surface.

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

  The inventor conducted various studies on maximization of the air flow velocity gradient in the vicinity of the tire side surface. When an object (for example, a flat plate) is disposed in a fluid flow, it is known that the fluid velocity abruptly decreases near the object surface due to the viscosity of the fluid. A region where the fluid velocity is not affected by the viscosity is formed outside the region (boundary layer) where the fluid velocity changes suddenly. The thickness of the boundary layer increases from the front edge of the object toward the downstream side. The boundary layer near the front edge of the object is laminar (laminar boundary layer), but becomes turbulent (turbulent boundary layer) through the transition region toward the downstream side. The present inventor has completed the present invention by paying attention to the fact that the heat dissipation efficiency from the object to the fluid is high because the fluid velocity gradient is large in the laminar boundary layer. That is, the present inventor has conceived that high heat dissipation in the laminar boundary layer is applied 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 a surface of a tire side portion, and the protrusion includes a top surface, a front side surface that is a front side surface 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 in the tire circumferential direction of the top surface, The width of the protrusion is 10 mm or more, and the gradient in the tire circumferential direction of the top surface at the front side portion is set so that the thickness of the protrusion increases as the distance from the front side portion increases. Provide pneumatic tires.

  The protrusion has a shape whose thickness is smaller than the width, and the air flow near the top surface of the protrusion becomes a laminar flow when the pneumatic tire rotates. Since the air flow of the laminar flow (laminar flow boundary) has a large velocity gradient, heat dissipation by air cooling of the top surface of the protrusion is effectively promoted. In addition, since the width of the protrusion is set to 10 mm or more, a sufficient heat radiation area of the protrusion due to the laminar flow is ensured. 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 as the distance from the front side increases. This gradient can suppress or prevent the separation of the air flow at the top surface near the front side, and can surely promote heat dissipation by laminar flow.

  According to the pneumatic tire of the present invention, when rotating, the air flow on the top surface of the protrusion formed on the surface of the tire side portion becomes a laminar flow, so that heat dissipation by air cooling is effectively promoted and durability is improved. improves. In addition, since the gradient in the tire circumferential direction of the top surface of the protrusion on the front side portion is set so that the thickness of the protrusion increases as the distance from the front side portion increases, the air on the top surface near the front side portion The separation of the flow can be suppressed or prevented, and the promotion of heat dissipation by the laminar flow can be surely obtained.

The meridian sectional view of the pneumatic tire concerning the embodiment of the present invention. The partial side view of the pneumatic tire which concerns on embodiment of this invention. The elements on larger scale of FIG. The typical perspective view of protrusion. The end view of a processus | protrusion. The partial end elevation of the processus | protrusion for demonstrating a front-end | tip angle. The end view of the processus | protrusion for demonstrating the gradient of a top surface. The top view of the protrusion for demonstrating the path | route of an airflow. The end view of the processus | protrusion for demonstrating the path | route of an airflow. The schematic diagram for demonstrating the path | route of the airflow between protrusions and protrusions. The end view of the processus | protrusion for demonstrating a boundary layer. The end view of the processus | protrusion for demonstrating a boundary layer. The end surface of the processus | protrusion for demonstrating the airflow which flows through a top surface in case an end surface is a flat surface extended along the surface of a tire side part. The end view of the processus | protrusion of embodiment for demonstrating the airflow which flows through a top surface. The end view of the processus | protrusion which shows the alternative of the shape of a top surface. The end view of the processus | protrusion which shows the alternative of the shape of a top surface. The end view of the processus | protrusion which shows the alternative of the shape of a top surface. The end view of the processus | protrusion which shows the alternative of the shape of a top surface. The end view of the processus | protrusion which shows the alternative of the shape of a top surface. The partial side view of a pneumatic tire provided with the processus | protrusion which has the inclination angle of the front side part different from embodiment. The elements on larger scale of FIG. The figure which shows the alternative of the shape of the processus | protrusion in planar view. The figure which shows the alternative of the shape of the processus | protrusion in planar view. The figure which shows the alternative of the shape of the processus | protrusion in planar view. The figure which shows the alternative of arrangement | positioning of a processus | protrusion. The figure which shows the alternative of arrangement | positioning of a processus | protrusion. The figure which shows the alternative of arrangement | positioning of a processus | protrusion. The figure which shows the alternative of arrangement | positioning of a processus | protrusion. The figure which shows the alternative of the shape of protrusion in an end surface view. The figure which shows the alternative of the shape of protrusion in an end surface view. The figure which shows the alternative of the shape of protrusion in an end surface view. The figure which shows the alternative of the shape of protrusion in an end surface view. The figure which shows the alternative of the shape of protrusion in an end surface view. The figure which shows the alternative of the shape of protrusion in an end surface view. The perspective view of the processus | protrusion which provided the vertical slit. The perspective view of the processus | protrusion which provided the horizontal slit.

(First 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 this embodiment is a run-flat tire of size 245 / 40R18. The present invention can also be applied to tires of different sizes. The present invention can also be applied to tires not included in the category of run-flat tires. 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 part 4 is provided at the inner end of the tire side part 3 in the tire radial direction (end opposite to the tread part 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 surface of the tread portion 2. In other words, in the tread portion 2, the belt layer 8 is provided on the outer side in the tire radial direction of the carcass 5.

  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 shape, size, and posture of these protrusions 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 the symbol TH. The protrusion 11 can be provided in a range from 0.05 times to 0.7 times the tire height TH from the outermost peripheral position P1 of the rim.

  In the present specification, “plan view” or a similar term may be used for the shape of the protrusion 11 viewed from the tire width direction, and “end view” for the shape of the protrusion 11 viewed from the inner end surface 15 side described later. Similar terms may be used.

  Referring to FIGS. 4 and 5, the protrusion 11 includes a top surface 12 that is a surface extending along the surface of the tire side portion 3. In the present embodiment, the top surface 12 has a blade cross-sectional shape in the end view. The protrusion 11 includes a pair of side surfaces opposed to 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 protrusion 11 has a pair of end faces opposed to each other in the tire radial direction, that is, an inner end face 15 inside the tire radial direction and an outer end face 16 outside the tire radial direction. As will be described in detail later, 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 that extend 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 intersect each other, and the rear side portion 18 is a portion where the top surface 12 and the rear side surface 14 intersect each other. The inner side portion 19 is a portion where the top surface 12 and the inner end surface 15 intersect each other, and the outer side portion 20 is a portion where the top surface 12 and the outer end surface 16 intersect each other. The front side portion 17, the rear side portion 18, the inner side portion 19, and the outer side portion 20 may be sharp or clear edges as in this embodiment, but have a shape that is curved to some extent in an end view. It may be. In the present embodiment, the shapes of the front side portion 17, the rear side portion 18, the inner side portion 19 and the outer side portion 20 in plan view are all linear. However, the shape in plan view may be a curved line including an arc and an elliptical arc, may be a broken line composed of a plurality of straight lines, or may be a combination of straight lines and curved lines.

  Referring to FIG. 3, the front side portion 17 is inclined with respect to a straight line extending in the tire radial direction passing through the front side portion 17 in plan view. In other words, the front side portion 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 direction in which the reference straight line Ls that passes through the frontmost position in the tire rotation direction RD of the front side portion 17 and extends in the tire radial direction and the front side portion 17 extends. (In this embodiment, the front side 17 which is a straight line) is defined as an angle (clockwise in a plan view is positive).

  The front side portion 17 in the present embodiment extends upward in a plan view. As shown in FIGS. 16 and 17, the protrusion 11 may have a shape in which the front side portion 17 extends downward in a plan view. The rear side portion 18 of the present embodiment extends substantially parallel to the front side portion 17 in plan view. Moreover, the inner side part 19 and the outer side part 20 of this embodiment are mutually extended in parallel with planar view.

  Referring to FIG. 3, the symbol R represents the tire radius, and the symbol Rp represents the 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 tire rotation center of the center pc of the protrusion 11 (for example, the centroid of the top surface 12 in plan view). Further, the symbol hRp in FIG. 3 indicates the size 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. Further, the symbol hRpc in FIG. 3 indicates the width of the protrusion 11 at the center pc of the protrusion.

  Referring to FIGS. 5 and 7, the top surface 12 of the protrusion 11 has a shape protruding or bulging toward the outer side in the tire width direction (the direction away from the surface of the tire side portion 3) in the end view. Specifically, as described above, the end surface of the protrusion 11 of the present embodiment has a blade cross-sectional shape in the end surface view. 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 changes from the front side surface 13 (front side portion 17) to the rear side surface 14 (rear side portion 18). 5 and 7, the position where the thickness tRp is the largest in the top surface 12 in the end view is indicated by the symbol P3.

  Referring to FIG. 7, in the region from the front side 17 to the position P3 on the top surface 12 of the protrusion 11, the gradient in the tire circumferential direction of the top surface 12 increases as the distance from the front side 17 increases (position P3). The thickness hRp of the protrusion 11 is set so as to gradually increase. Moreover, in the area | region from the position P3 to the rear side part 18 among the top surfaces 12 of the protrusion 11, the gradient of the tire peripheral direction of the top surface 12 is accompanied with leaving | separating from the position P3 (with approaching the rear side 18). The thickness hRp of the protrusion 11 is set so as to gradually decrease. At the position P3, the gradient in the tire circumferential direction of the top surface 12 is 0 °. In particular, the gradient θ1 in the tire circumferential direction of the top surface 12 at the front side portion 17 is set upward from the front side portion 17 toward the position P3. Specifically, the gradient θ1 can be set to 5 ° or more and 85 ° or less. Further, the gradient θ2 in the tire circumferential direction of the top surface 12 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 ° to −5 °. The gradient 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 (horizontal line Lh) extending in the tire radial direction passing through one point on the top surface 12 where the gradient is measured in end view. Further, as shown in FIG. 7, the sign of the gradient is positive in the counterclockwise direction when the inner end face 15 of the protrusion 11 is viewed from the inner side in the tire radial direction.

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

  Referring to FIGS. 5 and 6, the top surface 12 of the protrusion 11 and the front side surface 13 form an angle (tip angle a <b> 2) at the front side portion 17 in the end surface view. The front side surface 13 in the present embodiment has an inclination such that the top surface 12 and the front side surface 13 have a tapered shape in which the interval is narrowed toward the front side portion 17. In other words, the inclination of the front side surface 13 is set so that the lower end of the front side surface 13 is positioned on the rear side in the tire rotation direction RD with respect to the front side portion 17 in the 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 °). A 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 air flow flowing into the protrusion 11 from the front side 17 side is near the surface of the tire side 3 as conceptually indicated by the arrow AF <b> 0. To occur. 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 line (horizontal line Lh) drawn with respect to a straight line passing through the position P2 in the tire radial direction. Have According to the analysis performed by the inventor, the inflow angle afl is 12 ° under the conditions that the tire side 245 / 40R18, the distance Rpc of the center Pc of the protrusion 11 from the tire rotation center is 550 mm, and the vehicle traveling speed is 80 km / h. It is. Further, when the traveling speed changes in the range of 40 to 120 km / h, the inflow angle afl has a change of about ± 1 °. In actual use, since there are influences due to various factors including head wind, vehicle structure, etc. in addition to the traveling speed, the inflow angle afl under the above-mentioned conditions can be regarded as about 12 ± 10 °.

  Still referring to FIGS. 8 to 10, the air flow AF1 flows into the protrusion 11 from the front side portion 17, and is divided into two air flows at the time of the inflow. As shown most clearly in FIG. 8, one air flow 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 toward the rear side portion 18 (main air Flow). The other air flow AF2 is guided by the front side surface 13 and flows outward along the surface of the tire side portion 3 in the tire radial direction (subsequent air flow). As shown in FIGS. 12 and 13, when the front side portion 17 is lowered to the right in a plan view, the air flow AF <b> 2 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 protrusion 11 is a laminar flow. That is, the laminar boundary layer LB is formed in the vicinity of the top surface 12 of the protrusion 11. In FIG. 11, the symbol Va conceptually indicates the velocity gradient in the vicinity of the surface of the tire side portion 3 and the vicinity of the top surface 12 of the protrusion 11 in the airflow AF0 and the airflow AF1. Since the air flow AF1 that is a laminar flow has a large velocity gradient, heat is radiated from the top surface 12 of the protrusion 11 to the air flow AF1 with high efficiency. In other words, the air flow AF2 on the top surface 12 of the protrusion 11 becomes a laminar flow, thereby effectively promoting heat dissipation by air cooling. By effectively air-cooling, the durability of the tire 1 is improved.

  As indicated by an arrow AF <b> 3 in FIG. 10, the air flow 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 air flow 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 area TA, heat dissipation from the surface of the tire side portion 3 is promoted by an increase in the velocity 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 achieved by both laminarization of the air flow AF1 on the top surface 12 of the protrusion 11 and turbulence of the air flow AF3 between the protrusions 11 and 11. Has improved.

  As will be described in detail later, the width hRp (see FIG. 3) of the protrusion 11 at the distance Rp from the tire rotation center is set so as to be a laminar boundary layer LB up to the rear side portion 18 of the top surface 12 of the protrusion 11. It is preferable. However, as conceptually shown in FIG. 12, the width hRp of the protrusion 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 protrusion 11. A relatively long dimension is allowed. Even in such a case, in the region where the laminar boundary layer LB is formed on the top surface 12 of the protrusion 11, the advantage of improving heat dissipation is obtained due to the large velocity gradient.

  Referring to FIGS. 13 and 14, when viewed from the tire radial direction, the direction of the air flow 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 It is tilted a little in the direction away from. Therefore, as shown in FIG. 13, if the top surface 12 of the protrusion 11 is a flat surface extending in parallel along the surface of the tire side portion 3, the air flow AF1 flowing through the top surface 12 is in the vicinity of the front side portion 17. May cause peeling PE. When peeling PE occurs, the air flow AF1 becomes a turbulent flow, and the heat dissipation efficiency from the top surface 12 decreases. Referring to FIGS. 7 and 14, in this embodiment, since the gradient θ1 of the top surface 12 in the front side portion 17 is set upward as described above, the air flows from the front side portion 17 toward the position P3. The flow AF1 flows smoothly along the top surface 12, and peeling PE can be suppressed or prevented. Therefore, by setting the gradient θ1 of the top surface 12 in the front side portion 17 upward, heat radiation promotion by laminar flow can be reliably obtained. Referring also to FIG. 5, in order to reliably prevent the separation of the airflow AF1, the position P3 where the slope of the top surface 12 becomes 0 is set on the front side 17 side rather than half of the width hRp of the protrusion 12. It is preferable.

  Referring to FIGS. 7 and 14, as described above, the gradient θ2 of the top surface 12 in the rear side portion 18 is set downward. Therefore, the air flow 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 flow area TA is reliably formed between the adjacent protrusions 11 and 11, and heat dissipation from the surface of the tire side portion 3 due to the turbulent flow of the air flow AF3 is reliably obtained.

  In order to cause the air flow AF0 to be divided into the air flows AF1 and AF2 when flowing into the protrusion 11 as described above, the thickness tRp of the protrusion 11, particularly the thickness tRp in the front side portion 17, It is preferably smaller than the width hp (the minimum width when the width hp is not constant).

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

  Referring to FIG. 3, when the front side portion 17 is rising to the right in a plan view as in the present embodiment, the front side portion 17 intersects the airflow AF0 flowing into the front side portion 17 at 45 °. It is more preferable to set so as to. 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 a range defined by the following expression (1). It is preferable.

  Referring to FIG. 17, when the front side portion 17 is downwardly inclined, the inclination angle a1 of the front side portion 17 is set so as to intersect with the air flow AF0 flowing into the front side portion 17 at 45 °. Is preferable, and is preferably set within a range defined by the following formula (2).

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

  Referring to FIGS. 5 and 6, in order to cause the air flow AF0 when flowing into the protrusion 11 to be divided into the air flows AF1 and AF2, the tip angle a2 of the protrusion 11 does not need to be set excessively 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 °. It is not preferable that the tip angle a2 is excessively small because it causes a decrease in the strength of the protrusion 11 in the vicinity of the front side portion 17. Therefore, the tip angle a2 is particularly preferably set in the 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 narrow, the heat dissipation area from the protrusion 11 due to the laminar boundary layer LB near the top surface 12 becomes insufficient, and heat dissipation due to the laminar flow occurs. The promotion effect cannot be obtained sufficiently. For this reason, the width hRp of the protrusion 11 is preferably set to 10 mm or more.

  Still referring to FIG. 3, the width hRp of the protrusion 11 at an arbitrary position in the tire radial direction is preferably set so as to satisfy the following expression (3). All the mathematical expressions 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 the distance Rp from the tire rotation center

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

  If the width hRp is too large, the velocity boundary layer grows excessively on the protrusion 11 and the velocity gradient becomes small, so that the heat dissipation is deteriorated. The upper limit value 50 in the expression (3) is defined from this viewpoint. Hereinafter, the reason why the upper limit value is set to 50 will be described.

  It is known that the development of the velocity boundary layer on the flat plate, that is, the transition from the laminar boundary layer LB to the turbulent boundary layer TB is expressed 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 flat plate tip where transition from laminar boundary layer to turbulent boundary layer occurs U: Inflow velocity ν: Kinematic viscosity coefficient of fluid

  Considering the influence of mainstream disturbance and the fact that the boundary layer grows to some extent in the vicinity of the transition region, the maximum gradient hRp_max of the width hRp of the protrusion 11 necessary for obtaining a sufficient cooling effect is This is considered to be about ½ of the distance x in equation (4). Therefore, the maximum width hRp_max of the protrusion 11 is expressed by the following formula (5).

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

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

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

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

  When driving at high speed where the heat generation of the tire 1 becomes more conspicuous, specifically considering vehicle speed V up to 160 km / h, hRp_max is as follows from equation (8).

  Thus, in order to form the laminar boundary layer LB in the entire width direction of the top surface 12 of the protrusion 11 even when traveling at a high speed (vehicle speed V is 160 km / h or less), the equation (3) The upper limit value is 50.

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

  The protrusion 11 in FIG. 15A has an arcuate top surface 12 in an end view.

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

  The protrusion 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 gradient. The flat surface 42 from the position P3 to the rear side 18 has a constant downward gradient. The position P3 is set on the front side 17 side rather than half of the width hRp of the protrusion 12.

  The top surface 12 of the protrusion 11 shown in FIG. 15D has two flat surfaces 51 and 53 inclined in the tire circumferential direction with respect to the surface of the tire side portion 3 and one piece extending in parallel with the surface of the tire side portion 3. The flat surface 52 is comprised. 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 gradient. The flat surface 52 extends from the position P3 to the rear side 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 on the front side 17 side rather than half of the width hRp of the protrusion 12.

  The top surface 12 of the protrusion 11 shown in FIG. 15E is composed of a single flat surface inclined in the tire circumferential direction. The end face 12 has a certain upward slope.

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

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

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

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

  18B and 18C has a shape in a plan view in which the front side portion 17 extends to the right and the rear side portion 18 extends to the right. In particular, the protrusion 11 in FIG. 18C has an isosceles trapezoidal shape in plan view.

  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 FIG. 19B and FIG. 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 portion 17 that rises to the right. In FIG. 19C, one of the two types of projections 11 has a front side portion 17 that is raised to the right, and the other projection 11 has a front side portion 17 that is lowered to the right.

  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.

  20A to 21B show various alternatives related to the shape of the front surface 13 of the protrusion 11 in the end view.

  The front side surface 13 of the protrusion 11 shown in FIGS. 20A to 20D constitutes one recess 23 in an end view.

  The front side surface 13 of the protrusion 11 in FIG. 20A is constituted by two flat surfaces 24a and 24b. In the end view, the flat surface 24a is lowered to the right and the flat surface 24b is raised to the right. These flat surfaces 24a and 24b form a triangular recess 23 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. By this curved surface, a semicircular recess 23 is formed when viewed from the end.

  The front side surface 13 of the protrusion 11 in FIG. 20C is configured by a flat surface 25a that is right-downward in an end view and a curved surface 25b having an arcuate cross-sectional shape. The flat surface 25 a is located on the top surface 12 side of the protrusion 11, and the curved surface 25 b is located on the surface side of the tire side portion 3. A recess 23 is formed by the flat surface 25a and the curved surface 25b.

  The front side surface 13 of the protrusion 11 in FIG. 20D is configured by three flat surfaces 26a, 26b, and 26c. In the end view, the flat surface 26a on the top surface 12 side of the protrusion 11 is lowered to the right, the flat surface 26c on the 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. A polygonal recess 23 is formed by these flat surfaces 26a to 26c.

  The front side surface 13 of the protrusion 11 shown in FIGS. 21A and 21B constitutes two depressions 23A and 23B arranged adjacent to each other in the tire radial direction in the end view.

  The front side surface 13 of the protrusion 11 in FIG. 21A is constituted by four flat surfaces 27a to 27d. In the end view, the flat surface 27a on the top surface 12 side of the protrusion 11 is downwardly inclined, and toward the surface of the tire side portion 3, the upwardly inclined flat surface 27b, the downwardly inclined flat surface 27c, and the upwardly flattened surface. The surface 27d is arranged in order. One recess 23A having a triangular cross-sectional shape is formed on the top surface 12 side of the protrusion 11 by the flat surfaces 27a and 27b, and adjacent to the surface side of the tire side portion 3 of the recess 23A, similarly, a triangular shape is formed. One recess 23B having the cross-sectional shape is formed by the flat surfaces 27c and 27d.

  The front side surface 13 of the protrusion 11 in FIG. 21B is composed of two curved surfaces 28a and 28b having a semicircular cross-sectional shape. A single recess 23A having a semicircular cross-sectional shape is formed by the curved surface 28a on the top surface 12 side of the protrusion 11, and adjacent to the surface side of the tire side part 3 of the recess 23A, the recess 23A is also semicircular. One recess 23B having a cross-sectional shape is formed by a curved surface 28b.

  The front side surface 13 of the protrusion 11 may constitute three or more depressions arranged adjacent to each other in the tire radial direction in the end view.

  By appropriately setting the shape, size, and number of depressions on the front side surface 13 as shown in FIGS. 20A to 21B, the air flow AF1 flowing along the top surface 12 of the projection 11 and the front side surface 13 of the projection 11 are formed. The flow rate ratio of the air flow AF2 flowing along can be adjusted.

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

  5 and 15A to 15E and FIGS. 20A to 21B, the angle formed between the top surface 12 of the projection 11 and the front side surface 13 in the front side portion 17, that is, the tip end angle a2 of the projection 11 is viewed in the end view. , And defined as an angle formed by a straight line Lt corresponding to the top surface 12 and a straight line Lfs corresponding to a portion in the vicinity of the front side portion 17 of the front side surface 13.

  The straight line Lt is defined as a straight line passing through the portion (position P3) having the largest thickness tRp on the top surface 12 and extending along the surface of the tire side portion 3. Referring to FIGS. 5, 15A, 15B, and 20A to 21B, when the top surface 12 is a curved surface, the tire side portion 3 passes through a position P3 where the thickness tRp is the largest in the top surface 12 when viewed from the end surface. A straight line extending along the surface is a straight line Lt. Referring to FIGS. 15C, 15D, and 15E, when the end surface 12 is composed of a plurality of or a single inclined flat surface, a straight line obtained by extending a portion in the vicinity of the front side portion 17 in the end surface view is obtained. , A straight line Lt.

  Referring to FIG. 5 and FIG. 15A to FIG. 15E, when the front side surface 13 is composed of a single flat surface, a straight line obtained by extending the front side surface 13 itself in an end view is a straight line Lfs. 20A to 20D, when the front side surface 13 forms a single recess 23, a straight line connecting the front side portion 17 and the most depressed position of the recess 23 in the end view is a straight line Lfs. is there. Referring to FIG. 21A and FIG. 21B, when a plurality of (two in these examples) dents 23A and 23B are configured, the front side 17 and the dent 23A positioned closest to the top surface 12 in the end view are shown. A straight line connecting the most depressed position is a straight line Lfs.

(Other embodiments)
Referring to FIG. 22, if the formation of laminar flow on the top surface 12 is not significantly inhibited, one projection 11 is arranged in the tire circumferential direction by one longitudinal slit 33 extending in the tire radial direction. You may divide | segment into the mutually independent part. Two or more vertical slits 33 may divide one protrusion 11 into three or more independent portions.

  Referring to FIG. 23, if the laminar flow formation on the top surface 12 is not significantly inhibited, the two protrusions 11 are arranged in the tire radial direction by one lateral slit 34 extending in the tire circumferential direction. You may divide | segment into the mutually independent part. One projection 11 may be divided into three or more parts by two or more vertical slits 34.

  One protrusion 11 may be divided into four or more parts by providing one or more vertical slits 33 and one or more horizontal slits 34.

  The depths of the vertical slit 33 and the horizontal slit 34 may be set so that these slits 33 and 34 reach the surface of the tire side part 3 from the top surface 12 as shown in FIGS. You may set so that these slits 33 and 34 may not reach the surface of the tire side part 3. FIG.

DESCRIPTION OF SYMBOLS 1 Tire 2 Tread part 3 Tire side part 4 Bead part 5 Carcass 6 Inner liner 7 Reinforcement 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 Indentation 24a, 24b, 25a, 26a-26c, 27a-27d Flat surface 25b, 28a, 28b Curved surface 31 Projection 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 the surface of the tire side part P3 Position where the thickness of the top surface is the largest Ls Reference straight line Lt, Lfs Straight line Lh Horizontal line AF0, AF1, AF2 Air Flow Va Air flow velocity LB Laminar boundary layer TR Transition region TB Turbulent boundary layer TA Turbulent region 1, .theta.2 gradient PE peeling

Claims (7)

Protrusions 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 tire rotation direction front side, and a front side portion where the top surface and the front side surface intersect each other,
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 in the tire circumferential direction of the top surface,
The width of the protrusion is 10 mm or more;
The pneumatic tire is configured such that a gradient in the tire circumferential direction of the top surface at the front side portion is set so that the thickness of the protrusion increases as the distance from the front side portion 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 facing the front side in the tire circumferential direction, and a rear side where the top side and the rear side intersect,
The gradient in the tire circumferential direction of the top surface at the rear side portion is set so that the thickness of the protrusion becomes smaller as the tire approaches 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 the tire rotation center at an arbitrary position on the 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 portion has an inclination with respect to a straight line extending in the tire radial direction passing through the front side portion 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 that is an angle formed by the top surface and the front side surface in the front side portion of the protrusion is 100 ° or less.

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