JP2017144789A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability of a pneumatic tire by effectively promoting heat radiation through air cooling.SOLUTION: A surface of a tire side part 3 is provided with a plurality of protrusions 11 arranged in the circumferential direction. A thickness htp of the protrusions 11, which is the distance from the surface of the tire side part 3 to a top face 12 of the protrusions 11, is smaller than a width hRp of the protrusions 11, which is the dimension of the top face 12 in the tire circumferential direction. Each of the protrusions 11 has a width hRp of 10 mm or more, and a width hRpn of any of the protrusions 11 satisfies 0.5×hs≤hRp≤1.5×hs for a reference width hs of the protrusions 11.SELECTED DRAWING: Figure 15A

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, paying attention to the fact that the heat dissipation efficiency from the object to the fluid is high because the velocity gradient of the fluid is larger in the laminar boundary layer than in the turbulent 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.

As a means for solving the above problems, the present invention provides:
Provided with a plurality of protrusions arranged in the circumferential direction on the surface of the tire side portion,
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,
Each protrusion has a width of 10 mm or more, and the width hRp of an arbitrary protrusion satisfies 0.5 × hs ≦ hRp ≦ 1.5 × hs with respect to the reference width hs of the protrusion. Provide pneumatic tires.

  This configuration effectively secures the top surface with sufficient length in the tire circumferential direction against the range where the air flow flowing on the surface of the projection is expected to be a high-speed laminar boundary layer. Can be cooled. Further, by providing a plurality of protrusions having different widths, any one of the protrusions is suitable for a difference in air flow based on the rotational speed of the tire. Therefore, regardless of the difference in the rotation speed of the tire, heat dissipation can be enhanced by any of the protrusions.

  According to the present invention, the width can be secured and the range in which the air flow at the top surface becomes a laminar boundary layer can be made sufficient. Therefore, it is possible to increase the heat dissipation by increasing the flow velocity at the top surface of the protrusion. Further, since the width is varied, it is possible to exert an appropriate heat dissipation performance corresponding to the difference in the air flow speed accompanying the change in the rotation speed of the tire with any of the protrusions.

The meridian sectional view of the pneumatic tire concerning a 1st embodiment of the present invention. The partial side view of the pneumatic tire which concerns on 1st 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 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 partial side view of a pneumatic tire provided with the processus | protrusion which has the inclination angle of the front side part different from 1st 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 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 cross-sectional shape of an alternative. The figure which shows the cross-sectional shape of an alternative. The perspective view of the processus | protrusion which provided the vertical slit. The perspective view of the processus | protrusion which provided the horizontal slit.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. In addition, the following description is only illustrations essentially and does not intend restrict | limiting this invention, its application thing, or its use. Moreover, the drawings are schematic, and the ratio of each dimension and the like do not always match those of the actual one.

First, the basic configuration of the embodiment of the present invention will be described.
FIG. 1 shows a meridian half sectional view of a rubber pneumatic tire (hereinafter referred to as a tire) 1. This tire 1 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 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 2 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 symbol 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 to be described later. Or, a similar term may be used.

  4 and 5, the protrusion 11 includes a top surface 12 that is a flat surface extending along the surface of the tire side portion 3 in the present embodiment. The protrusion 11 includes 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 (tire rotation reverse direction) in the tire rotation direction RD. Further, the protrusion 11 has an inner end surface 15 on the inner side in the tire radial direction and an outer end surface 16 on the outer side in 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 are curved or chamfered to some extent in an end view. You may have. 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 (front side surface 13) 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).

  However, the front side portion 17 (front side surface 13) is not only linearly inclined in a plan view, but may be curved. In short, it is either in the tire circumferential direction toward the tire outer diameter direction. It only needs to be displaced to one side.

  According to this, it becomes easy to make the air on the surface side of the tire side part 3 diverted at the front side part 17 a first flow (subsequent air flow) that flows in the tire circumferential direction along the front side surface 13. The second flow (main air flow) along the top surface 12 is set to a high-speed laminar flow state, and the range of the laminar boundary layer LB can be expanded.

  The front side surface 13 is preferably displaced in the tire rotation reverse direction toward the tire outer diameter direction.

  According to this, the 2nd flow can be made to correspond with the direction of the centrifugal force which acts on the air which passes the surface of tire side part 3 by rotation of a tire. Therefore, the second flow can be made even smoother.

  The front side portion 17 in the present embodiment extends upward in a plan view. As shown in FIGS. 12 and 13, 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 also to FIG. 5, in this embodiment, the thickness tRp of the protrusion 11 at an arbitrary position in the tire radial direction of the protrusion 11 is constant. That is, the thickness tRp of the protrusion 11 is uniform in the tire radial direction of the protrusion 11. In the present embodiment, the thickness tRp of the protrusion 11 is constant from the front side surface 13 (front side portion 17) to the rear side surface 14 (rear side portion 18). That is, the thickness tRp of the protrusion 11 is uniform even in the tire circumferential direction of the protrusion 11.

  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. 7 to 9, 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 portion 3 as conceptually indicated by the arrow AF <b> 0. To occur. Referring to FIG. 7, the airflow AF0 at a specific position P2 on the surface of the tire side portion 3 is at an angle (horizontal line Lh) with respect to a perpendicular (horizontal line Lh) drawn with respect to a straight line passing through the position P2 and extending in the tire radial direction. Inflow angle afl). According to the analysis performed by the present inventor, the inflow angle afl is 12 ° under the conditions of the tire size 245 / 40R18, the distance Rpc from the center Pc of the protrusion 11 from the tire rotation center, and the vehicle traveling speed 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. 7 to 9, the air flow AF <b> 1 flows into the protrusion 11 from the front side portion 17, and is divided into two air flows at the time of this inflow. As shown most clearly in FIG. 7, 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: first flow). The other air flow AF2 flows outward in the tire radial direction along the front side surface 13 (subsequent air flow: second flow). As shown in FIGS. 12 and 13, when the front side portion 17 is downwardly lowered in plan view, the air flow AF <b> 2 flows along the front side surface 13 inward in the tire radial direction.

  Referring also to FIG. 10, the airflow 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. 10, 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 AF2 which 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 AF2 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, promotion of a change with time of the tire constituent material due to a temperature rise is suppressed, and the durability of the tire 1 is improved.

  As indicated by an arrow AF3 in FIG. 9, the air flow passing through the top surface 12 and flowing downstream from the rear side portion 18 collides with the surface of the tire side portion 3 after passing through the top surface 12 and changes its direction. Is done. As a result, heat radiation from the surface of the tire side portion 3 is promoted between the adjacent protrusions 11 and 11.

  As described above, in the tire 1 of the present embodiment, the heat dissipation of the tire 1 is improved by both laminarization of the airflow AF1 on the top surface 12 of the protrusion 11 and collision of the airflow AF3 between the protrusions 11 and 11. doing.

  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. 11, 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.

  In order for the air flow AF0 flowing into the protrusion 11 described above to be divided into the air flows AF1 and AF2, the thickness http of the protrusion 11, particularly the thickness http at the front side portion 17 is the width hp ( If the width hp is not constant, it is preferably smaller than the minimum width.

  As described above, the air flow AF0 flowing into the protrusion 11 has the inflow angle afl. In order for 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 to 90 ° and 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 become. 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 plan view, 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 °. More preferred. In this case, as described above, since the inflow angle afl of the air flow AF0 can be regarded as about 12 ± 10 °, the inclination angle a1 of the front side portion 17 is equal to the following equation (1). It is preferable to set within the range defined by.

  Referring to FIG. 13, when the front side portion 17 is descending to the right, the inclination angle a1 of the front side portion 17 is set to intersect with the airflow 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).

  5 and 6, in order for the air flow AF0 flowing into the protrusion 11 to be appropriately diverted 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 90 ° or less and should be 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 TB in the vicinity of the top surface 12 is insufficient, and heat dissipation due to the laminar flow. 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).

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 dimension at which the laminar boundary layer TB is obtained.

  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 TB 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 is 50 mm.

  Next, other features of the present invention will be described.

  In FIG. 15A, three types of protrusions 11 (11a, 11b, 11c) having different widths hRp are arranged on the surface of the tire side portion 3. The protrusion 11a has the shortest width hRp, and is wider in the order of the protrusions 11b and 11c. These protrusions 11 are repeatedly arranged in the order of 11a, 11b, 11c, and 11b in the tire rotation reverse direction (clockwise direction in the figure). That is, the ratio of the intermediate width projections 11b accounts for half. Therefore, it is preferable to set the width hRp of the protrusion 11b to a value that maximizes the heat dissipation at the top surface 12 in a traveling state where the heat dissipation effect is expected (vehicle speed V is, for example, 80 km / h).

  Here, the significance of providing three types of protrusions 11 having different widths hRp will be described. That is, the flow velocity of the air flowing through the tire side portion 3 is different due to a difference in the rotation speed of the tire, and the formation length of the laminar boundary layer TB is also changed. The formation length of the laminar boundary layer TB is long when the air flow rate is low, and is short when the air flow rate is high. Therefore, by setting the widths hRp of the protrusions 11 to three types, the heat dissipation can be improved regardless of the difference in the air flow rate. Specifically, when the air flow rate is low, the heat dissipation can be improved by forming a sufficiently long laminar boundary layer TB on the top surface 12 of the projection 11 having a long width hRp. In addition, when the flow velocity of air is high, the laminar boundary layer TB disappears at a short distance and becomes a turbulent boundary layer TB. Therefore, the air exceeding the short protrusion 11 having the short width hRp is guided between the adjacent protrusions 11. The heat dissipation can be improved by causing the tire side portion 3 to collide with the surface. Thereby, even if the flow velocity on the surface of the tire side portion 3 changes based on the difference in the rotational speed of the tire, etc., any one of the protrusions 11 functions effectively to enhance the heat dissipation performance, and the heat dissipation performance as a whole is increased. Can be improved.

  In FIG. 15B, three types of protrusions 11 (11a, 11b, 11c) having different inclination angles a1 of the front side portion 17 (front side surface 13) are arranged on the surface of the tire side portion 3. The front side portions 17 of the three types of protrusions 11 are all raised to the right. The inclination angle a1-1 of the protrusion 11a is the largest at 53 °, the inclination angle a1-2 of the protrusion 11b is 43 °, and the inclination angle a1-3 of the protrusion 11c is 30 ° in this order. These protrusions 11 are repeatedly arranged in the order of the protrusions 11a, 11b, 11c, and 11b in the tire rotation reverse direction (clockwise direction in the figure). That is, the ratio of the protrusions 11b having the intermediate inclination angle a1-2 occupies half. Therefore, in a traveling state where the heat dissipation effect is expected (vehicle speed V is 80 km / h, for example), the first flow along the top surface 12 and the second flow along the front side surface 13 are appropriately divided. It is preferable to set the inclination angle a1-2 to an angle at which heat dissipation is most enhanced.

  According to the above configuration, when the rotation speed of the tire 1 is high, the air flow passing through the protrusion 11a is also fast, and the first flow along the top surface 12 is mostly not diverted well at the front side portion 17. It becomes. On the other hand, since the projection 11c having a large inclination angle a1 can form the second flow along the front side surface 13 even if the air flow speed is high, the first flow along the top surface 12 is separated from the laminar flow boundary. It is possible to exhibit heat dissipation as the layer TB. Further, when the rotation speed of the tire 1 is slow, even with the protrusion 11 a having a small inclination angle a 1, the first flow along the top surface 12 (laminar flow boundary layer TB) and the second flow along the front side surface 13. Therefore, heat can be radiated from the top surface 12 effectively. As described above, since the heat dissipation performance of any one of the protrusions 11 can be enhanced regardless of the rotational speed of the tire 1, the heat dissipation performance of the protrusions 11 can be improved as a whole.

(Other embodiments)
In the above-described embodiment, the projection 11 is configured with three types having different widths hRp. However, the projection 11 may be configured with two types having different widths hRp, or may be configured with four or more types. The two types of protrusions 11 having different widths hRp are preferably arranged alternately in the tire circumferential direction, but a plurality of units 11 may be arranged in such a manner, and the number of the protrusions 11 can be freely set. The same applies to the case of three or more types of protrusions 11 having different widths hRp.

  By increasing the types of protrusions 11 having different widths hRp, it is possible to easily exhibit sufficient heat dissipation with any of the protrusions 11 regardless of the difference in the rotation speed of the tire 1.

The inclination angle a <b> 1 of the front side portion 17 (front side surface 13) is preferably different for each protrusion 11. In this case, it is preferable that the inclination angle a1 satisfies the following with respect to the reference inclination angle as.

  Here, the reference inclination angle as is a reference, an air flow generated in the tire side portion 3 at a certain vehicle speed (for example, 80 km / h) (the flow velocity on the surface of the tire side portion 3 at this time is a flow rate). This is a value that can be effectively cooled by the protrusion 11. If as−10 °> a1, the inclination angle of the front side surface 13 of the protrusion becomes insufficient, and the air does not flow along the front side surface and easily flows over the top surface 12. For this reason, the 1st flow in the top surface 12 is disturbed, it is hard to become a laminar flow state, and heat dissipation is impaired. If a1> as + 10 °, the protrusion 11 is excessively inclined, and it becomes difficult to form the first flow that flows on the top surface 12, and the heat dissipation is also impaired.

The inclination angle a1 of the front side surface 13 of the protrusion 11 preferably satisfies the following expression with respect to the reference width hs in the tire circumferential direction and the width hn in the tire circumferential direction at any protrusion 11.

  Here, the reference width hs in the tire circumferential direction is a value that can be effectively cooled by the protrusion 11 by the air flow generated in the tire side portion 3 at a certain vehicle speed. Therefore, if the case where the vehicle speed is low is used as a reference, hs becomes long. If the case where the vehicle speed is high is used as a reference, hs becomes short. Α is a coefficient, and α = 20 here. α = 20 is assumed because the ratio of the width hn of the protrusion 11 to be adopted with respect to the reference width hs is assumed to be 0.5 to 1.5 times. This is to make ± 10 ° with respect to the inclination angle as.

  Further, the shape of the protrusion 11 in plan view can take various forms as follows.

  The rear side portion 18 of the protrusion 11 in FIG. 14A has a shape in plan view constituted by two straight lines having different inclination angles.

  14B and 14C has a shape in 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. 14C has an isosceles trapezoidal shape in plan view.

Further, when the protrusion 11 is composed of two or more types having different widths hRp, it is preferable that the protrusion 11 is configured to satisfy the following expression with respect to the reference length hs in the tire circumferential direction.

  If 0.5 × hs> hRp, the width of the protrusion 11 becomes too narrow, and the laminar flow range of the air flow cannot be used. If hRp> 1.5 × hs, the top surface 12 is formed beyond the laminar flow range of the air flow, which is not preferable in terms of heat dissipation.

  The protrusion 11 only needs to have an angle formed by the front side surface 13 on the tire rotation direction side and the top surface 12 of the tire side portion 3 of 100 ° or less, preferably 90 ° or less, and less than 90 °. Is preferred.

  If the angle exceeds 100 °, the air flow tends to flow toward the top surface 12 as it is without being diverted well on the front side surface 13 of the protrusion 11. For this reason, it becomes difficult to maintain the air flow state on the top surface 12 as a laminar flow, and there is a possibility that the heat dissipation at the protrusion 11 is deteriorated. By making the angle 90 ° or less, and further less than 90 °, the diversion at the front side portion 17 is more appropriately performed, and the range of the laminar boundary layer of the air flow along the top surface 12 is further expanded. Heat dissipation can be improved.

  In addition, this invention is not limited to the structure described in the said embodiment, A various change is possible.

  In FIG. 15C, two types of projections 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. 15C, one of the two types of projections 11 has a front side portion 17 that rises to the right, and the other projection 11 has a front side portion 17 that falls to the right.

  In FIG. 15D, 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.

  16A to 16C show various alternatives of the shape of the top surface 12 of the protrusion 11 in the end view. The protrusion 11 in FIG. 16A has a top surface 12 having a blade cross-sectional shape in an end view. The protrusion 11 in FIG. 16B has an arcuate top surface 12 in an end view. The protrusion 11 in FIG. 16C has a curved top surface 12 that is neither a blade cross-sectional shape nor an arc shape in the end view.

  The front side surface 13 of the protrusion 11 shown in FIGS. 17A to 17D constitutes a single recess 23 in an end view.

  The front side surface 13 of the protrusion 11 in FIG. 17A 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. 17B 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. 17C 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. 17D 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. 18A and 18B constitutes two depressions 23A and 23B arranged adjacent to each other in the tire radial direction in an end view.

  The front side surface 13 of the protrusion 11 in FIG. 18A is configured 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. 18B 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. 17A to 18B, 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. 16A to 16C and any of the shapes of the front side surface 13 of FIGS. 17A to 18B.

  5 and 16A to 18B, the angle formed by the top surface 12 and the front side surface 13 of the protrusion 11 in the front side portion 17, that is, the tip angle a2 of the protrusion 11 corresponds to the top surface 12 in the end view. Is defined as an angle formed by a straight line Lt and a straight line Lfs corresponding to a portion of the front side surface 13 near the front side portion 17.

  The straight line Lt is defined as a straight line that passes through the portion of the top surface 12 having the largest thickness tRp and extends along the surface of the tire side portion 3. Referring to FIGS. 5 and 17A to 18B, when the top surface 12 is a flat surface extending along the surface of the tire side portion 3, a straight line obtained by extending the top surface 12 itself in the end view is a straight line Lt. is there. Referring to FIGS. 16A to 16C, when the top surface 12 is a curved surface, a straight line passing through the position P3 having the largest thickness tRp in the top surface 12 and extending along the surface of the tire side portion 3 is a straight line. Lt.

  Referring to FIGS. 5 and 16A to 16C, 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 an end view is a straight line Lfs. Referring to FIGS. 17A to 17D, when the front side surface 13 forms a single recess 23, the straight line connecting the front side portion 17 and the most recessed position of the recess 23 in the end view is a straight line Lfs. is there. Referring to FIGS. 18A and 18B, when a plurality of (two in these examples) dents 23A and 23B are configured, the front side 17 and the dent 23A located 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.

  As shown in FIG. 19A, the protrusion 31 may have a semicircular cross-sectional shape, and the groove 32 may have a complementary cross-sectional shape with respect to the protrusion 31. Moreover, as shown to FIG. 19B, the cross-sectional shape of the protrusion 31 and the groove | channel 32 may be square shape.

  Referring to FIG. 20, if the formation of the 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. 21, if the formation of the laminar flow on the top surface 12 is not significantly inhibited, one projection 11 is 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.

  Further, the position where the protrusion 11 is formed may be on the outside (side of the vehicle) or on the inside in a state where the tire 1 is mounted on the vehicle.

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 33 Vertical slit 34 Horizontal slit RD Rotation direction P1 Rim outermost position P2 Tire Specific point on the surface of the side part P3 Position where the thickness of the top surface is the maximum Ls Reference line Lt, Lfs 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 Turbulence region

Claims (6)

Provided with a plurality of protrusions arranged in the circumferential direction on the surface of the tire side portion,
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,
Each protrusion has a width of 10 mm or more, and the width hRp of an arbitrary protrusion satisfies 0.5 × hs ≦ hRp ≦ 1.5 × hs with respect to the reference width hs of the protrusion. Pneumatic tire.   The pneumatic tire according to claim 1, wherein the protrusion has three or more types having different widths hRp.   3. The pneumatic tire according to claim 1, wherein an angle formed between the front side surface on the tire rotation direction side and the top surface of the tire side portion is 100 ° or less.   The pneumatic tire according to claim 3, wherein the angle is less than 90 °.   The pneumatic tire according to claim 3 or 4, wherein the front side surface is displaced in any one of the tire circumferential directions toward the tire outer diameter direction.   The pneumatic tire according to claim 5, wherein the front side surface is displaced in the tire rotation reverse direction toward the tire outer diameter direction.

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