JP6702749B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire.

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

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 air flow near the tire side surface.

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

The present inventor has made various studies on maximizing the velocity gradient of the air flow near the tire side surface. It is known that when an object (for example, a flat plate) is placed in the flow of a fluid, the velocity of the fluid rapidly decreases near the surface of the object due to the viscosity of the fluid. A region where the velocity of the fluid is not affected by the viscosity is formed outside the region (boundary layer) where the velocity of the fluid suddenly changes. 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 body is laminar (laminar boundary layer), but becomes turbulent (downstream) through the transition region toward the downstream side (turbulent boundary layer). The present inventor has completed the present invention by paying attention to the fact that in the laminar boundary layer, the velocity gradient of the fluid is large, so that the heat radiation efficiency from the object to the fluid is high. That is, the present inventor has conceived that the high heat dissipation in the laminar boundary layer is applied to air cooling of a pneumatic tire. The present invention is based on this new idea.

The present invention comprises a protrusion provided on the surface of the tire side portion, and 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 the tire circumferential direction of the top surface. The width is smaller than the width of the protrusion, which is a dimension, and the width of the protrusion is 10 mm or more. The protrusion has a rear side surface that is a rear side surface in the tire rotation direction, and the rear side surface is a tire width. Seen from the direction, extending in a direction inclined with respect to the tire radial direction, on the tire radial direction one end side located on the tire rotation direction front side, a concave portion that is concave on the tire rotation direction front side is formed , The rear side surface is inclined toward the rear side in the tire rotation direction from the one end portion side in the tire radial direction toward the other end portion side, and the first surface portion and the other end portion side located on the one end portion side. A second surface portion, and the recess is formed by the first surface portion and the second surface portion. The second inclination angle of the second surface portion with respect to the tire radial direction is the tire diameter of the first surface portion. A pneumatic tire having an obtuse angle formed between the first surface portion and a side surface of the protrusion located on the one end side in the tire radial direction, the angle being larger than a first inclination angle with respect to the direction. ..

In the present specification, the concave portion means a portion of the rear side surface of the protrusion, which is located on the front side in the tire rotation direction with respect to the line segment connecting the inner end portion and the outer end portion in the tire radial direction of the rear side surface. And

The protrusion has a shape in which the thickness is smaller than the width, and when the pneumatic tire rotates, the air flow near the top surface of the protrusion becomes a laminar flow. Since the laminar airflow (laminar flow boundary) has a large velocity gradient, heat dissipation by air cooling of the top surface of the protrusion is effectively promoted. Further, since the width of the protrusion is set to 10 mm or more, the heat radiation area of the protrusion due to the formation of the laminar flow is sufficiently secured.

Moreover, stagnation of the air flow is likely to occur in the recess formed on the rear side surface of the projection, and the stagnation attracts the air flow separated by passing through the end surface on the one end side in the tire radial direction of the projection to attract the projection. It acts to redeposit on the back side. As a result, the air flow effectively flows to the rear side surface of the protrusion, so that heat dissipation by air cooling is promoted in the region near the rear side surface of the protrusion. Thus, prone to stagnation of air flow, cooling of the area near the side surface side after the protrusion is improved.

According to the pneumatic tire of the present invention, at the time of rotation, the air flow on the top surface of the protrusion formed on the surface of the tire side portion becomes a laminar flow, and in addition to this, the air flow also occurs in the vicinity of the rear side surface of the protrusion. Since it can be effectively flowed, heat dissipation by air cooling is effectively promoted and durability is improved.

The meridian sectional view of the pneumatic tire which concerns on 1st Embodiment of this 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 schematic perspective view of a protrusion. The end view of a protrusion. FIG. 3 is a partial end view of a protrusion for explaining a tip angle. The top view of the protrusion for demonstrating the path|route of an airflow. FIG. 3 is an end view of a protrusion for explaining a path of an air flow. The top view for demonstrating the path|route of the airflow which flows along the tire radial end part of a protrusion. FIG. 3 is a schematic diagram for explaining a protrusion and an airflow path between the protrusions. FIG. 3 is an end view of a protrusion for explaining a boundary layer. FIG. 3 is an end view of a protrusion for explaining a boundary layer. The figure which shows the alternative of the shape of the protrusion in planar view. The figure which shows the alternative of the shape of the protrusion in planar view. The figure which shows the alternative of the shape of the protrusion in planar view. The figure which shows the alternative of the shape of the protrusion in an end view. The figure which shows the alternative of the shape of the protrusion in an end view. The figure which shows the alternative of the shape of the protrusion in an end view. The figure which shows the alternative of the shape of the protrusion in an end view. The figure which shows the alternative of the shape of the protrusion in an end view. The figure which shows the alternative of the shape of the protrusion in an end view. The figure which shows the alternative of the shape of the protrusion in an end view. The figure which shows the alternative of the shape of the protrusion in an end view. The figure which shows the alternative of the shape of the protrusion in an end view. The partial side view of the pneumatic tire which concerns on 2nd Embodiment. The elements on larger scale of FIG. The schematic diagram for demonstrating the path|route of the airflow which flows along the tire radial end part of a protrusion.

(First embodiment)
FIG. 1 shows a pneumatic tire (hereinafter referred to as tire) 1 made of rubber 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 be applied to tires of different sizes. The present invention can also be applied to tires that are not included in the category of run flat tires. The tire 1 has a designated rotation direction. 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 of the bead portions 4 is provided at an inner end portion of the tire side portion 3 in the tire radial direction (an end portion on the side opposite to the tread portion 2). A carcass 5 is provided between the pair of bead portions 4. A reinforcing rubber 7 is arranged 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 outside the carcass 5 in the tire radial direction.

Referring to FIGS. 2 and 3, a plurality of protrusions 11 are provided on the surface of the tire side portion 3 at intervals in the tire circumferential direction. In this embodiment, these protrusions 11 have the same shape, size, and posture. In FIG. 1, the distance (tire height) from the outermost peripheral position P1 of the rim (not shown) to the outermost position of the tread portion 2 in the tire radial direction is indicated by TH. The protrusion 11 can be provided in a range of 0.05 times or more and 0.7 times or less of the tire height TH from the outermost peripheral position P1 of the rim.

In this specification, the shape of the protrusion 11 viewed from the tire width direction may be referred to as “plan view” or a similar term, and the shape of the protrusion 11 viewed from the inner end surface 15 side described below may be referred to as “end view” or Sometimes terms like that are used.

With reference to FIGS. 4 and 5, the protrusion 11 includes a top surface 12 that is a flat surface that extends along the surface of the tire side portion 3 in the present embodiment. Further, the protrusion 11 includes a pair of side surfaces facing each other in the tire circumferential direction, that is, a front side surface 13 and a rear side surface 14. The front side surface 13 is located on the front side in the tire rotation direction RD, and the rear side surface 14 is located on the rear side in the tire rotation direction RD. Further, the protrusion 11 has a pair of end surfaces facing each other in the tire radial direction, that is, an inner end surface 15 on the tire radial inner side and an outer end surface 16 on the tire radial outer side. As described in detail later, the front side surface 13 in the present embodiment is a flat surface that is 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 with each other, and the rear side portion 18 is a portion where the top surface 12 and the rear side surface 14 intersect with each other. The inner side portion 19 is a portion where the top surface 12 and the inner end surface 15 intersect with each other, and the outer side portion 20 is a portion where the top surface 12 and the outer end surface 16 intersect with each other. The front side portion 17, the rear side portion 18, the inner side portion 19, and the outer side portion 20 may have a sharp or clear edge as in the present embodiment, but have a curved shape to some extent in an end view. May be. In the present embodiment, the shapes of the front side portion 17, the inner side portion 19, and the outer side portion 20 in plan view are all linear, and the shape of the rear side portion 18 in plan view is two straight lines. It is a polygonal line composed of. However, the shape in plan view thereof may be a curved shape including an arc and an elliptic arc, a polygonal line composed of a plurality of straight lines, or 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 passing through the front side portion 17 and extending in the tire radial direction in a 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 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 direction in which the front side portion 17 extends. It is defined as an angle formed by (the front side portion 17 itself which is a straight line in the present embodiment) (clockwise is positive in a plan view).

The front side portion 17 in the present embodiment extends to the upper right in a plan view. Further, the inner side portion 19 and the outer side portion 20 of the present embodiment extend parallel to each other in a plan view.

The rear side portion 18 of the present embodiment has a shape formed by two straight lines having different inclination angles in a plan view. Specifically, the rear side surface 14 is composed of a first surface portion 14a located inside the tire radial direction and a second surface portion 14b located outside the tire radial direction. The first surface portion 14a extends upward in the plan view at an inclination angle a3 with respect to the tire radial direction. The second surface portion 14b extends upward in the plan view at an inclination angle a4 with respect to the tire radial direction, and is substantially parallel to the front side surface 13 in the plan view. The inclination angle a4 of the second surface portion 14b is larger than the inclination angle of the first surface portion 14a, that is, the second surface portion 14b is inclined rearward of the first surface portion 14a in the tire rotation direction RD.

A bent portion z1 is formed between the first surface portion 14a and the second surface portion 14b. In other words, as the rear side surface 14 advances from the tire radial direction inner side to the outer side, the inclination angle with respect to the tire radial direction increases toward the rear side in the tire rotation direction RD with the bent portion z1 as a boundary. That is, when viewed from the tire width direction, the rear side surface 14 is formed with a concave portion 30 that is a concave portion on the front side in the tire rotation direction RD by the first surface portion 14a and the second surface portion 14b. When viewed from the direction, it has a bending point z1 at the peripheral edge. The bent portion z1 is located in a range of 1/2L on the tire radial direction inner side with respect to the tire radial dimension L of the protrusion 11. That is, the recess 30 is formed from the inner side in the tire radial direction. In addition, in the present specification, the concave portion is more than a line segment Lr connecting the inner end portion and the outer end portion in the tire radial direction of the rear side surface 14 of the rear side surface 14 of the protrusion 11 when viewed from the tire width direction. It means a portion located on the front side in the tire rotation direction RD.

Referring to FIG. 3, reference symbol R indicates the tire radius, and reference symbol Rp indicates the distance from the tire rotation center at any position of the protrusion 11 in the tire radial direction. Further, reference symbol Rpc in FIG. 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 dimension of the protrusion 11 in the tire circumferential direction, that is, the width of the protrusion 11, at an arbitrary position in the tire radial direction. Reference numeral hRpc in FIG. 3 indicates the width of the protrusion 11 at the center pc of the protrusion. Further, as described above, since the second surface portion 14b extends substantially parallel to the front side surface 13, the width hRp at any position passing through the second surface portion 14b is substantially constant. Further, the width hRp at an arbitrary position passing through the first surface portion 14a is longer than that on the second surface portion 14b side.

Referring also to FIG. 5, in the present embodiment, the thickness tRp of the protrusion 11 at any 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. Further, 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 in the tire circumferential direction of the protrusion 11.

Referring to FIGS. 5 and 6, in the end view, the top surface 12 of the projection 11 and the front side surface 13 of the front side portion 17 form an angle (tip angle a2). 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 taper shape with a narrower interval toward the front side portion 17. In other words, the inclination of the front side surface 13 is set such that the lower end of the front side surface 13 is located rearward of the front side portion 17 in the tire rotation direction RD in 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°). The specific definition of the tip angle a2 will be described later.

Referring to FIG. 7 to FIG. 10, when the vehicle equipped with the tire 1 is traveling, the airflow flowing into the protrusion 11 from the front side 17 side is near the surface of the tire side 3 as conceptually indicated by an arrow AF0. Occurs in. Referring to FIG. 7, 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 vertical line (horizontal line Lh) drawn with respect to a straight line extending in the tire radial direction passing through the position P2. Have. According to the analysis performed by the present inventor, the inflow angle afl is 12° under the condition 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. Is. When the traveling speed changes in the range of 40 to 120 km/h, the inflow angle afl changes by about ±1°. In actual use, the inflow angle afl under the above-mentioned conditions can be considered to be about 12±10° because there are various factors such as head wind and vehicle structure in addition to the traveling speed.

With continued reference to FIGS. 7 to 10, the airflow AF0 flows into the projection 11 from the front side portion 17 and is divided into two airflows at the time of this inflow. As shown most clearly in FIG. 7, one airflow AF1 rides up from the front side surface 13 to the top surface 12 and flows along the top surface 12 from the front side portion 17 to the rear side portion 18 (main air Flow). The other air flow AF2 flows outward along the front side surface 13 in the tire radial direction (subordinate air flow).

Referring also to FIG. 11, 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 near the top surface 12 of the protrusion 11. In FIG. 11, reference symbol Va conceptually shows velocity gradients in the vicinity of the surface of the tire side portion 3 and in the vicinity of the top surface 12 of the projection 11 of the airflows AF0 and AF1. Since the airflow AF1 that is a laminar flow has a large velocity gradient, heat is efficiently radiated from the top surface 12 of the protrusion 11 to the airflow AF1. In other words, since the airflow AF1 on the top surface 12 of the protrusion 11 becomes a laminar flow, heat dissipation by air cooling is effectively promoted. The effective air cooling improves the durability of the tire 1.

As shown by an arrow AF4 in FIG. 10, air flow stagnation occurs on the rear surface side (that is, the rear side surface 14 side) of the projection 11 with respect to the flow direction of the air flow AF0. Since this stagnation has a relatively small flow rate with respect to the surrounding airflow, the surrounding airflow is attracted so as to supplement the airflow AF4 in the stagnation. Therefore, as indicated by an arrow AF3, the air flow passing through the top surface 12 and flowing from the rear side portion 18 to the downstream side is attracted by the stagnation (air flow AF4) on the back surface side of the protrusion 11, and the top surface 12 is drawn. Falls toward the surface of the tire side portion 3. The airflow AF3 collides with the surface of the tire side portion 3. As a result, the air flow in the area TA near the surface of the tire side portion 3 becomes turbulent between the adjacent protrusions 11, 11. In this area TA, heat dissipation from the surface of the tire side portion 3 is promoted due to an increase in velocity gradient due to turbulence of the air flow.

Further, the airflow AF3 that has collided with the area TA is directed to the next protrusion 11 adjacent to the rear side of the tire rotation direction RD. Thereby, in addition to the air cooling by the laminar flow of the air flow AF1 on the surface of the projections 11, the air cooling is realized between the projections 11 by the turbulent flow generated by the collision of the air flow AF3.

Here, referring to FIG. 9, in the present invention, the rear side surface 14 of the protrusion 11 extends in a direction inclined with respect to the tire radial direction when viewed from the tire width direction, and is located in front of the tire rotation direction RD. A concave portion 30 that is a concave portion on the front side in the tire rotation direction RD is formed on one end side in the tire radial direction in which the tire is positioned. That is, in the present embodiment, the rear side surface 14 extends upward in the plan view shown in FIG. 9, and the inner end portion in the tire radial direction is located on the front side in the tire rotation direction RD. The recess 30 is formed on the rear side surface 14 on the inner end side in the tire radial direction.

Since it is difficult for the surrounding airflow to flow into the recess 30, the stagnation of the airflow occurs as indicated by an arrow AF6. As described above, since the stagnation has a relatively small flow rate with respect to the surrounding air flow, it acts to attract the surrounding air flow. Therefore, the airflow AF6 acts so as to attract the airflow AF8 that has passed through the inner end surface 15 of the projection 11 and separated from the projection 11 and to reattach it to the rear side surface 14 of the projection 11.

As described above with reference to FIG. 10, the airflow AF1 that has passed through the top surfaces of the protrusions 11 gently drops toward the tire side portion between the protrusions that are adjacent in the tire circumferential direction. The flow of air is less likely to flow in the region near, and stagnation AF4 tends to occur over the entire rear surface. That is, on the rear side surface 14 side of the protrusion 11, the stagnation AF4 of the air flow is generated over the entire rear side surface, and the stagnation AF6 is locally generated in the concave portion 30. Therefore, the air flow AF7 that has passed along the inner end surface 15 of the protrusion 11 in the tire radial direction is once separated from the protrusion 11 as shown by an arrow AF8, but is generated in the recess 30 as shown by an arrow AF9. It is attracted by the AF 6, reattaches to the projection 11 as shown by an arrow AF 10, and flows in the tire radial direction along the rear side surface 14. As a result, the stagnation of the air flow AF4 generated on the rear side surface 14 of the protrusion 11 is scavenged by the air flow AF10 flowing along the rear side surface 14 and eliminated. This promotes heat dissipation by air cooling in the region near the rear side surface 14.

When there is no recess on the rear side surface 14 of the protrusion 11, the airflow AF8 that has passed through the inner end surface 15 and separated on the rear side surface 14 side is gently tired, as indicated by the dashed lines AF90 and AF100 in FIG. It does not flow radially outward and reattach to the rear side surface 14. Therefore, the stagnation of the airflow AF4 in the region near the rear side surface 14 of the protrusion 11 is not eliminated.

In addition, preferably, the bending point z1 is 1/4L or more/from the one end in the tire radial direction located on the front side of the rear side surface 14 in the tire rotation direction RD with respect to the tire radial length L of the protrusion 11. It is located in the range of 3L or less. That is, in the present embodiment, since the rear side surface 14 extends upward in the plan view to the right, the bending point z1 is from the inner end portion of the rear side surface 14 in the tire radial direction located on the front side in the tire rotation direction RD. It is located in the range of 1/4L or more and 1/3L or less. As a result, the concave portion 30 formed by the bending point z1 is located closer to the front end of the rear side surface 14 in the tire rotation direction RD than the rear side surface 14, and the air flow separated by passing through the end side. The AF 8 can be effectively attracted so as to be reattached to the rear side surface 14 side of the protrusion 11.

As described above, in the tire 1 of the present embodiment, the laminar flow of the air flow AF1 on the top surface 12 of the protrusion 11, the turbulent flow of the air flow AF3 between the protrusions 11 and the rear surface 14 of the protrusion 11. The heat dissipation of the tire 1 is improved by the scavenging of the region in the vicinity of.

As will be described later in detail, the width hRp (see FIG. 3) of the protrusion 11 at the distance Rp from the tire rotation center is set so that the laminar flow boundary layer LB extends to the rear side portion 18 of the top surface 12 of the protrusion 11. Preferably. 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. Relatively long dimensions are also acceptable. Even in such a case, in the region of the top surface 12 of the protrusion 11 where the laminar flow boundary layer LB is formed, the advantage of improving the heat dissipation is obtained due to the large velocity gradient.

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

As described above, the airflow AF0 flowing into the protrusion 11 has the inflow angle afl. In order to cause the airflow AF0 to be divided into the airflows AF1 and AF2, the inclination angle a1 of the front side portion 17 of the projection 11 in plan view is set to be 90° when the airflow AF0 enters the front side portion 17. Must be set so that In other words, it is necessary to tilt the front side portion 17 of the protrusion 11 with respect to the airflow AF0 in plan view.

Referring to FIG. 3, as in the present embodiment (for example, see FIG. 3 ), when the front side portion 17 is rising to the right in a plan view, the front side portion 17 has an air flow AF0 flowing into the front side portion 17. More preferably, they are set to intersect at 45°. In this case, as described above, the inflow angle afl of the airflow AF0 can be regarded as about 12±10°, and therefore the inclination angle a1 of the front side portion 17 is set within the range defined by the following equation (1). Preferably.

Referring to FIGS. 5 and 6, in order to cause the airflow AF0 to be divided into the airflows AF1 and AF2 when flowing into the protrusion 11, the tip angle a2 of the protrusion 11 needs not 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°. An excessively small tip angle a2 is not preferable because it causes a decrease in the strength of the protrusion 11 near the front side portion 17. Therefore, it is preferable to set the tip angle a2 in the range of 45° or more and 65° or less.

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

Continuing to refer to FIG. 3, the width hRp of the protrusion 11 at any position in the tire radial direction is preferably set so as to satisfy the following expression (2). All 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 any 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 region in which the velocity gradient increases cannot be sufficiently secured, and a sufficient cooling effect cannot be obtained. The lower limit value 10 in the equation (2) corresponds to the minimum necessary heat radiation area 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 protrusions 11, the velocity gradient becomes small, and the heat dissipation deteriorates. The upper limit value 50 in the formula (2) 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 flow boundary layer LB to the turbulent boundary layer TB is represented by the following equation (3).

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

x: Distance from the tip of flat plate where transition from laminar boundary layer to turbulent boundary layer occurs U: Inflow velocity ν: Dynamic viscosity coefficient of fluid

Considering the influence of the turbulence of the main flow and the fact that the boundary layer grows to some extent in the vicinity of the transition region to reduce the velocity gradient, the maximum value hRp_max of the width hRp of the protrusion 11 required to obtain a sufficient cooling effect is It is considered to be about ½ of the distance x in Expression (3). Therefore, the maximum width hRp_max of the protrusion 11 is expressed by the following equation (4).

The inflow velocity U of the fluid into the protrusion 11 is represented 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 the product of the tire radius R and the tire angular speed (V=Rω). Therefore, the relationship of the following expression (6) is established.

The following equation (6) is established for the kinematic viscosity ν of air.

By substituting the equations (5) and (6) into the equation (4), the following equation (7) is obtained.

Assuming that the vehicle speed V is 80 km/h, hRp_max is as follows from Expression (7).

When the vehicle runs at high speed where the heat generation of the tire 1 becomes more remarkable, specifically, when considering the vehicle speed V up to 160 km/h, hRp_max is as follows from the equation (7).

As described above, even when the vehicle travels at high speed (the vehicle speed V is 160 km/h or less), the laminar flow boundary layer LB is formed in the entire width direction of the top surface 12 of the protrusion 11 by the formula (2). Is 50.

13A to 13C show various alternatives of the shape of the protrusion 11 in plan view. Specifically, an alternative plan is shown in which a plurality of bending points and/or inflection points are formed in the peripheral portion of the recess 30 in a plan view.

The projection 11 in FIG. 13A has a rear side surface 14 that is formed by a first surface portion 21a, a second surface portion 21b, and a third surface portion 21c that extend in the tire radial direction at different inclination angles in plan view. Each of the first surface portion 21a, the second surface portion 21b, and the third surface portion 21c extends linearly in a plan view, and a bending point z1 is formed between the first surface portion 21a and the second surface portion 21b. A bending point z2 is formed between the second surface portion 21b and the third surface portion 21c. The third surface portion 21c extends substantially parallel to the front side surface 13 in plan view. The 1st surface part 21a, the 2nd surface part 21b, and the 3rd surface part 21c are a boundary of the bending points z1 and z2, and a tire radial direction outer part is a tire rotation direction RD rear side rather than a tire radial direction inner part. Is inclined to. The bending points z1 and z2 are located in the range of 1/2L of the radial dimension L of the protrusion 11 from the inner end of the protrusion 11 in the tire radial direction.

The protrusion 11 in FIG. 13B has a rear side surface 14 that is configured by a first surface portion 22a, a second surface portion 22b, and a third surface portion 22c that extend in the tire radial direction at different inclination angles in plan view. Each of the first surface portion 22a and the third surface portion 22c extends linearly in a plan view, and the second surface portion 22b extends in an arc shape in a plan view. The third surface portion 22c extends substantially parallel to the front side surface 13 in plan view. An inflection point x1 is formed between the first surface portion 22a and the second surface portion 22b, and an inflection point x2 is formed between the second surface portion 22b and the third surface portion 22c. The first surface portion 21a, the second surface portion 21b, and the third surface portion 21c are arranged such that the outer side portion in the tire radial direction is located behind the inner side portion in the tire radial direction RD with the inflection points x1 and x2 as boundaries. Inclined to the side. The inflection points x1 and x2 are located in the range of 1/2L of the radial dimension L of the protrusion 11 from the inner end of the protrusion 11 in the tire radial direction.

The protrusion 11 of FIG. 13C has a rear side surface 14 formed by a first surface portion 23a, a second surface portion 23b, a third surface portion 23c, and a fourth surface portion 23d, which extend in the tire radial direction at different inclination angles in plan view. Have Each of the first surface portion 23a, the second surface portion 23b and the fourth surface portion 23d extends linearly in a plan view, and the third surface portion 23c extends in an arc shape in a plan view. The fourth surface portion 23d extends substantially parallel to the front side surface 13 in plan view. A bending point z1 is formed between the first surface portion 23a and the second surface portion 23b, an inflection point x1 is formed between the second surface portion 23b and the third surface portion 23c, and a third surface portion 23c and a fourth surface portion 23c are formed. An inflection point x2 is formed between the surface portion 23d. In the first surface portion 23a, the second surface portion 23b, the third surface portion 23c, and the fourth surface portion 23d, the outer side portion in the tire radial direction is an inner side portion in the tire radial direction with the bending point z1 and the inflection points x1 and x2 as boundaries. Is inclined rearward with respect to the tire rotation direction RD. The bending point z1 and the inflection points x1 and x2 are located within a range of 1/2L of the radial dimension L of the protrusion 11 from the inner end of the protrusion 11 in the tire radial direction.

14A to 14C show various alternatives of the shape of the top surface 12 of the protrusion 11 in an end view. The protrusion 11 in FIG. 14A has a top surface 12 having a blade cross-sectional shape in an end view. The protrusion 11 in FIG. 14B has a top surface 12 that is arcuate in an end view. The protrusion 11 in FIG. 14C has a curved top surface 12 that is neither a blade cross-sectional shape nor an arc shape in end view.

15A to 16B show various alternatives regarding the shape of the front side surface 13 of the protrusion 11 in an end view.

The front side surface 13 of the protrusion 11 shown in FIGS. 15A to 15D constitutes one recess 23 in an end view.

The front side surface 13 of the protrusion 11 in FIG. 15A is composed of two flat surfaces 24a and 24b. In the end view, the flat surface 24a is sloping down to the right and the flat surface 24b is sloping up to the right. These flat surfaces 24a, 24b form a triangular recess 23 in an end view.

The front side surface 13 of the protrusion 11 in FIG. 15B is configured by a curved surface having a semicircular cross-sectional shape. With this curved surface, a semicircular recess 23 is formed in an end view.

The front side surface 13 of the protrusion 11 in FIG. 15C is configured by a flat surface 25a that is inclined downward to the right in an end view and a curved surface 25b having an arc-shaped cross section. The flat surface 25a is located on the top surface 12 side of the protrusion 11, and the curved surface 25b is located on the front surface side of the tire side portion 3. A depression 23 is formed by the flat surface 25a and the curved surface 25b.

The front side surface 13 of the protrusion 11 in FIG. 15D is composed of three flat surfaces 26a, 26b, 26c. In the end view, the flat surface 26a on the top surface 12 side of the protrusion 11 is sloping down to the right, the flat surface 26c on the surface side of the tire side portion 3 is rising to the right, and the central flat surface 26b extends in the tire width 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. 16A and 16B constitutes two recesses 23A and 23B that are arranged adjacent to each other in the tire width direction in an end view.

The front side surface 13 of the protrusion 11 in FIG. 16A is composed of four flat surfaces 27a to 27d. In the end view, the flat surface 27a on the top surface 12 side of the projection 11 is downwardly sloping to the right, and the flat surface 27b to the right, the flat surface 27c to the right, and the flat surface to the right are directed toward the surface of the tire side portion 3. The surface 27d is arranged in order. By the flat surfaces 27a and 27b, one depression 23A having a triangular cross-sectional shape is formed on the side of the top surface 12 of the projection 11, and the depression 23A is adjacent to the surface side of the tire side portion 3 and similarly has a triangular shape. One recess 23B having a cross-sectional shape of is formed by the flat surfaces 27c and 27d.

The front side surface 13 of the protrusion 11 in FIG. 16B is composed of two curved surfaces 28a and 28b having a semicircular cross-sectional shape. A single depression 23A having a semicircular cross-sectional shape is formed by the curved surface 28a of the projection 11 on the top surface 12 side, and the depression 23A is adjacent to the surface side of the tire side portion 3 and similarly has a semicircular shape. One recess 23B having the cross-sectional shape of is formed by the curved surface 28b.

The front side surface 13 of the protrusion 11 may form three or more recesses that are arranged adjacent to each other in the tire radial direction in an end view.

By appropriately setting the shape, size, and number of the depressions on the front side surface 13 as shown in FIGS. 15A to 16B, 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 of the airflow AF2 flowing along can be adjusted.

One projection 11 may be formed by combining any one of the shapes of the top surface 12 of FIGS. 14A to 14C and any of the shapes of the front side surface 13 of FIGS. 15A to 16B.

Referring to FIGS. 5 and 14A to 16B, the angle formed by the top surface 12 of the protrusion 11 and the front side surface 13 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 the angle formed by the straight line Lt and the straight line Lfs corresponding to the 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 position P3 where the thickness is the maximum thickness tRp of the top surface 12 and extends along the surface of the tire side portion 3. Referring to FIGS. 5 and 15A to 16B, since the top surface 12 is a flat surface extending along the surface of the tire side portion 3 in any case, a straight line obtained by extending the top surface 12 itself in the end view is a straight line. It is Lt. Referring to FIGS. 14A to 14C, when the top surface 12 is a curved surface, a straight line that passes through the position P3 where the thickness tRp is largest in the top surface 12 in the end view and that extends along the surface of the tire side portion 3 is a straight line. It is Lt.

Referring to FIGS. 5 and 14A to 14C, when the front side surface 13 is configured by a single flat surface, the straight line obtained by extending the front side surface 13 itself in the end view is the straight line Lfs. Referring to FIGS. 15A to 15D, when the front side surface 13 constitutes a single recess 23, a 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. With reference to FIGS. 16A and 16B, when a plurality of (two in these examples) recesses 23A and 23B are configured, in the end view, the recess 23A positioned on the front side portion 17 and the most top surface 12 side is located. The straight line connecting the most depressed position is the straight line Lfs.

(Second embodiment)
17 to 19 show a second embodiment of the present invention. The present embodiment is the same as the first embodiment except that the shape of the projection 11 is different and extends downward to the right.

The protrusion 11 of FIGS. 17 and 18 has a front side portion 17 extending downward to the right in plan view. The inclination angle a3 of the front side portion 17 with respect to the tire radial direction is preferably set so as to intersect the airflow AF0 flowing into the front side portion 17 at 45° as described above, and the following formula (10) is used. It is preferable to set it within the range defined by.

With reference to FIG. 18, the rear side portion 18 has a shape configured by two straight lines having different inclination angles in a plan view. Specifically, the rear side surface 14 is configured by a first surface portion 14a located inside the tire radial direction and a second surface portion 14b located outside the tire radial direction. The first surface portion 14a extends downward in the plan view at an inclination angle a3 with respect to the tire radial direction, and the second surface portion 14b extends downward in the plan view at an inclination angle a4 with respect to the tire radial direction. The inclination angle a3 of the first surface portion 14a is larger than the inclination angle of the second surface portion 14b, that is, the first surface portion 14a is inclined rearward of the second surface portion 14b in the tire rotation direction RD.

A bent portion z1 is formed between the first surface portion 14a and the second surface portion 14b. In other words, the inclination angle of the rear side surface 14 with respect to the tire radial direction increases toward the rear side in the tire rotation direction RD with the bent portion z1 as a boundary as the rear side surface 14 advances from the outer side to the inner side in the tire radial direction. That is, when viewed from the tire width direction, the rear side surface 14 is formed with a concave portion 30 that is concave toward the front side in the tire rotation direction RD by the first surface portion 14a and the second surface portion 14b. The bent portion z1 is located in a range of 1/2L on the outer side in the tire radial direction with respect to the radial height L of the protrusion 11. That is, the concave portion 30 is formed from the outer side in the tire radial direction.

According to the present embodiment, as shown in FIG. 19, the front side portion 17 is downwardly sloping down in plan view, so that the airflow AF2 flows along the front side surface 13 inward in the tire radial direction. On the other hand, the airflow AF17 flowing along the outer end surface 16 of the projection 11 is once separated from the projection 11 as an airflow AF18 when flowing out to the rear side surface 14 side. However, in the present embodiment, since the concave portion 30 is formed at the outer end portion of the protrusion 11 in the tire radial direction, the concave portion 30 is attracted by the airflow AF16 as a stagnation generated in the concave portion 30, and as shown by an arrow AF19. It reattaches to 11 and flows inward in the tire radial direction along the rear side surface 14 as indicated by arrow AF20. As a result, the stagnation of the air flow 4 generated on the rear side surface 14 of the protrusion 11 is scavenged by the air flow AF20 flowing along the rear side surface 14 and eliminated. This promotes heat dissipation by air cooling in the region near the rear side surface 14.

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 12a Downhill Side 13 Front Side 14 Rear Side 15 Inner End 16 Outer End 17 Front Side 18 Rear Side portion 19 Inner side portion 20 Outer side portion 23, 23A, 23B Recess 24a, 24b, 25a, 26a to 26c, 27a to 27d Flat surface 25b, 28a, 28b Curved surface 30 Recessed portion 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 largest z1, z2, z3 Bending point x1, x2 Inflection point Ls Reference straight line Lt, Lfs Straight line Lh Horizontal line AF0, AF1, AF2, AF3, AF4, AF5 , AF6, AF7, AF8, AF9, AF10 Airflow Va Airflow velocity LB Laminar boundary layer TR transition region TB Turbulent boundary layer TA Turbulent region

Claims (6)

With a protrusion provided on the surface of the tire side part,
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 that is the dimension of the top surface in the tire circumferential direction,
The width of the protrusion is 10 mm or more,
The protrusion has a rear side surface that is a rear side surface in the tire rotation direction,
The rear side surface extends in a direction inclined with respect to the tire radial direction when viewed from the tire width direction, and is recessed to the front side in the tire rotation direction at one end side in the tire radial direction located on the front side in the tire rotation direction. Has a concave part that becomes ,
The rear side surface is inclined toward the rear side in the tire rotation direction from the one end portion side in the tire radial direction toward the other end portion side, and is located on the first surface portion and the other end portion side located on the one end portion side. A second surface portion that is positioned, and the concave portion is formed by the first surface portion and the second surface portion,
The second inclination angle of the second surface portion with respect to the tire radial direction is larger than the first inclination angle of the first surface portion with respect to the tire radial direction,
The pneumatic tire in which the angle between the first surface portion and the side surface of the protrusion located on the one end side in the tire radial direction is an obtuse angle . The one end side is an inner side in the tire radial direction,
The pneumatic tire according to claim 1. The pneumatic tire according to claim 1 or 2 , wherein the concave portion includes at least one bending point and/or inflection point at a peripheral edge portion when viewed in the width direction. The pneumatic tire according to claim 3 , wherein the bending point and/or the inflection point is located within a range of ½ of a radial height of the projection from a radial inner end of the rear side surface. . The bending point and / or the variable Kyokuten is located in a range of 1/4 or more than 1/3 of the radial height of the projection from the radially inner end of the rear side, to claim 3 Pneumatic tire described. The pneumatic tire according to any one of claims 3 to 5 , wherein a plurality of the bending points and/or the inflection points are formed.

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