JP7769745B2 - Pneumatic tire and mold for molding pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire and a mold for molding a pneumatic tire, and more specifically to a pneumatic tire having an undulating curved surface provided on the tire side surface, which is the axially outer surface of the tire radially outward from the rim line.

In recent years, the provision of multiple protrusions on the side of a tire has been considered in order to improve the design of the tire. For example, Patent Document 1 describes the provision of multiple cylindrical protrusions that protrude from the surface of the sidewall and generate turbulence. Patent Document 1 states that turbulence is generated by the edges at the connection between the tip surfaces of the protrusions and the sidewall surface.

Patent Document 2 describes how multiple protrusions that protrude outward from the tire are regularly arranged on the surface of the tire side, with the maximum width and height of the protrusions being within a predetermined range, and the spacing between the protrusions along the tire surface being greater than 0.1 μm and less than 100 μm. This is said to create an optimal air buffer layer on the tire surface.

Patent Document 3 describes a configuration in which multiple mountain-shaped protrusions with varying heights and minute pitches are formed on the tire side surface, resulting in an overall undulating shape that is inclined relative to the tire circumferential direction. This is said to improve the rigidity of the sidewall.

WO 2008/096879 JP 2013-169827 A Chinese Patent Application Publication No. 107499068

The configurations described in Patent Documents 1 to 3 leave room for improvement in terms of achieving a balance between improving the absorption of vibrations caused by bumps from the road surface during driving, suppressing increases in internal heat generation due to radial tire deflection, and reducing air resistance, while also making it easier to create contrast on the tire side surfaces.

The pneumatic tire of the present invention is a pneumatic tire that is provided with an undulating curved surface that is provided on the tire side surface, which is the axially outer surface of the tire, radially inward from the ground-contact edge of the tread and radially outward from the rim line, and that undulates radially in the tire direction to have multiple angle-shaped protrusions in the tire radial direction, each of which extends circumferentially in the tire direction, and multiple curved protrusions are provided on the surface of the undulating curved surface.

The pneumatic tire mold according to the present invention is a mold for molding a pneumatic tire according to the present invention, and has a mold-side curved surface on the molding surface that corresponds to the undulating curved surface, and a plurality of curved surface recesses corresponding to the curved surface protrusions are formed on the mold-side curved surface.

In the pneumatic tire and pneumatic tire mold according to the present invention, the undulating curved surface on the tire side undulates radially with multiple angle-shaped protrusions in the tire radial direction. This absorbs vibrations caused by upward thrusts when the tire goes over potholes and road bumps during travel, and increases the tire surface area, thereby suppressing increases in internal heat generation due to radial deflection. Furthermore, by providing a curved shape with few or no edges on the tire side, turbulence caused by edges can be suppressed, thereby reducing air resistance. Furthermore, the multiple curved protrusions facilitate contrast on the tire side. This achieves a balance between improved absorption of vibrations caused by upward thrusts from the road during travel, suppression of increases in internal heat generation due to radial deflection, and reduced air resistance, while also facilitating contrast on the tire side.

1 is a diagram showing a tire contour shape in a meridian cross section of a pneumatic tire that is an example of an embodiment, and is a diagram showing a range in which an undulating surface is formed. FIG. 1 is a perspective view showing a part in the tire circumferential direction of a pneumatic tire according to an embodiment, cut away from other parts. FIG. 2 is a perspective view showing a partially cutaway annular portion that forms an undulating curved surface in the embodiment. FIG. 2 is an enlarged cross-sectional view of part A in FIG. 1 . FIG. 4 is a schematic view as seen in the direction of arrow B in FIG. 3 . FIG. 10 is an enlarged perspective view of a curved surface protrusion provided on a wavy curved surface in the embodiment. 7 is a view of the curved projection of FIG. 6 viewed from the outside in the height direction. FIG. 10 is a schematic diagram showing that, in an embodiment, after an air flow collides with a curved protrusion, turbulence causes the air flow to reattach to another curved protrusion downstream, and the separation point is likely to be downstream. FIG. 10 is a schematic diagram showing that, in another example of the embodiment, a wavy curved surface does not generate turbulence in the same way as a smooth surface. FIG. 10 is a schematic diagram illustrating, using a cylinder Sa as a simulation, how a wake region is generated by a separated air flow downstream of a tire side surface in the air flow in another example of the embodiment. FIG. 10 is a schematic diagram illustrating, using a cylinder S, how the width of the wake region caused by the separated air flow narrows downstream of the tire side surface in the air flow, increasing the negative pressure reduction effect, in an embodiment. 1 is a schematic diagram showing an example of a case where a tire according to an embodiment overcomes a road bump; FIG. 2 is a cross-sectional view showing a mold for molding a pneumatic tire in an embodiment. 10A and 10B are diagrams illustrating protrusions on a curved surface in a pneumatic tire according to another embodiment. 10A and 10B are diagrams illustrating protrusions on a curved surface in a pneumatic tire according to another embodiment. 10A and 10B are diagrams illustrating protrusions on a curved surface in a pneumatic tire according to another embodiment. 10A and 10B are diagrams illustrating protrusions on a curved surface in a pneumatic tire according to another embodiment. FIG. 10 is a perspective view showing a curved surface protrusion in a pneumatic tire according to another embodiment. FIG. 19 is a view seen in the direction of arrow C in FIG. 18. This is a cross-sectional view taken along the line DD in FIG. 19. 20 is a cross-sectional view taken along the line E-E in FIG. 19. 10 is a view of a curved projection of a pneumatic tire according to another embodiment as viewed from the outside in the height direction. FIG. 10 is a view of a curved projection of a pneumatic tire according to another embodiment as viewed from the outside in the height direction. FIG. 10 is a view of a curved projection of a pneumatic tire according to another embodiment as viewed from the outside in the height direction. FIG. FIG. 6 is a view corresponding to FIG. 5 of a pneumatic tire according to another embodiment. FIG. 26 is a schematic diagram showing that the light absorption effect is produced by the configuration of FIG. 25 .

Below, one example of an embodiment of a pneumatic tire and a mold for molding the same according to the present invention will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. Furthermore, the present invention includes selective combinations of the components of the multiple embodiments and variations described below.

FIG. 1 is a meridian cross-section of a pneumatic tire 1 according to an embodiment, showing the tire contour shape and the range of undulation. FIG. 2 is a perspective view of a circumferential portion of the pneumatic tire 1, cut away from the rest of the tire. As shown in FIGS. 1 and 2, the pneumatic tire 1 includes a tread 10, which is the portion that comes into contact with the road surface. Hereinafter, "pneumatic tire 1" will be referred to as "tire 1." The tread 10 has a tread pattern including multiple blocks and is formed in an annular shape along the tire circumferential direction. While FIG. 1 shows the tread 10 as being formed of a single block, in reality, as shown in FIG. 2, the tread 10 includes multiple blocks 11a and 11b separated in the tire axial direction X. The multiple blocks 11a and 11b are separated by circumferential grooves 11c (FIG. 2) extending in the tire circumferential direction. The tread 10 has a ground-contact edge T. In FIGS. 1 and 2, the tire axial direction is indicated by X, the tire radial direction is indicated by Y, and the tire circumferential direction is indicated by α.

The following description of the tire 1 configuration focuses on the vehicle outer (OUT side) portion centered on the center CL in the tire axial direction X. The tire 1 is symmetrical between the vehicle outer and inner portions of the tire 1 with respect to the shape, except for the annular portion 100 provided with the undulating curved surface of the tire side surface (described below). Meanwhile, the vehicle inner (IN side) portion of the tire may also be provided with an annular portion 100 similar to the vehicle outer portion.

The tire 1 comprises a sidewall 12, which is located at the outer end of the tread 10 in the tire axial direction X and bulges outward most in the tire axial direction X, and a bead 15 (Figure 2) fixed to the wheel rim. The sidewall 12 and bead 15 are formed in an annular shape along the tire circumferential direction. The sidewall 12 extends inward in the tire radial direction Y from both ends of the tread 10 in the tire axial direction X. A rim strip 18, which forms the outer surface of the bead 15, is provided adjacent to the sidewall 12 at the inner end of the tire in the radial direction Y.

The tire 1 is a pneumatic tire that is filled with air at a predetermined pressure. The tread 10 is made of tread rubber. The sidewall 12 is made of a different type of sidewall rubber than the tread rubber.

Unless otherwise specified, the dimensions of each part of a tire in this specification are those measured when an unused tire is mounted on a standard rim, inflated to the standard internal pressure, and in a standard, unloaded condition.

"Touching edge T" refers to both ends in the axial direction X of the tire in the area that comes into contact with a flat road surface when an unused tire 1 is mounted on a standard rim and inflated to the standard internal pressure, and a load of 88% of the standard load at the standard internal pressure is applied.

Here, a "regular rim" is a rim specified by tire standards, and is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. "Regular internal pressure" is the "maximum air pressure" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "INFLATION PRESSURE" for ETRTO. "Regular load" is the "maximum load capacity" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "LOAD CAPACITY" for ETRTO.

The tire 1 comprises a carcass, a belt layer, and an inner liner. The carcass is a rubber-coated cord layer that forms the skeleton of the tire 1, enduring loads, impacts, air pressure, etc. The belt layer is a reinforcing band placed between the tread rubber and the carcass. The belt layer tightens the carcass, increasing the rigidity of the tire 1. The belt layer is formed by overlapping multiple belts in the tire radial direction Y. Each belt is formed by multiple cords that are arranged in a direction inclined relative to the tire circumferential direction and are covered with rubber. The cords of adjacent belts are inclined in opposite directions relative to the tire circumferential direction so that they cross each other. The cords are made of steel or the like.

A belt reinforcing layer is provided between the belt layer and the tread rubber, extending in the tire circumferential direction and covering the entire belt layer in the tire axial direction X. The belt reinforcing layer is formed by covering cords that extend approximately in the tire circumferential direction with rubber. The cords are made of organic fibers, etc.

In this embodiment, the tire 1 has a specified mounting orientation for the front and back of the tire 1 relative to the vehicle. That is, the tire 1 is specified as having an outer and inner side relative to the vehicle. In Figure 1, the tire 1 is mounted on the vehicle so that the right side is the outer side (OUT side) of the vehicle and the left side is the inner side (IN side) of the vehicle.

Tyre sidewalls generally have symbols called serial numbers. Serial numbers include information such as the size code, manufacturing date (manufacturing year and week), and manufacturing location (manufacturing factory code). The mounting direction of the tire 1 on the vehicle can be specified by providing a serial number only on the tire sidewall 12 facing the outside of the vehicle, or by providing different serial numbers on the side facing the outside and the side facing the inside of the vehicle. A specific example is to provide a manufacturing factory code and size code on both sides of the tire 1, and provide the manufacturing year and week only on the side facing the outside of the vehicle's width.

Also, the tire side facing outward from the vehicle may be marked with letters or symbols to indicate that it is on the outside when mounted on the vehicle.

A rim protector 19 that protrudes axially outward is provided as part of the rim strip rubber that forms the rim strip 18. The rim line 20 is provided in an annular shape along the circumferential direction of the tire at the apex of the rim protector 19 located at the axially outer end of the tire. The rim protector 19 functions to protect the rim from external damage. The rim line 20 is a line that can be used to check the gap between the tire and the rim to ensure that the tire 1 is properly positioned on the rim. While the rim protector 19 is provided in Figure 1, the configuration may also be such that it does not include the rim protector 19, as indicated by the two-dot chain line in Figure 1. Even in this case, the rim line, which is a circular protrusion that protrudes axially outward, is provided on the side of the tire to ensure that the tire 1 is properly positioned on the rim.

In this example, an annular portion 100 including a undulating surface 30 is provided on the tire side surface 13, which is the outer surface in the tire axial direction X, located radially inward of the ground contact edge T of the tread 10 and radially outward of the rim line 20.

As shown in FIG. 2 , the tire side surface 13 facing the vehicle exterior has an annular portion 100 with a constant radial length around the entire circumference. The annular portion 100 is formed by an undulating surface 30 that protrudes axially outward from the bottom of an annular recess 37. The undulating surface 30 undulates radially to form multiple angled protrusions 35. The ridge lines 31 of each angled protrusion 35 and the valley lines 38 between adjacent angled protrusions 35 extend circumferentially. The peaks of the angled protrusions 35 and the valley lines 38 are spaced at equal intervals radially. As described later, the tire of the present invention may have an arc-shaped portion located at one or more positions circumferentially on the tire side surface, instead of the annular portion 100 having an annular recess 37 with an annular undulating surface formed on its inner side, and having an arc-shaped recess with an arc-shaped undulating surface formed circumferentially.

Figure 3 is a perspective view, partially cut away, of the annular portion 100, which forms the undulating surface 30 in this embodiment. Figure 4 is an enlarged cross-sectional view of part A in Figure 1. Figure 5 is a schematic view as viewed in the direction of arrow B in Figure 3. The undulating surface 30 is formed on the tire side surface 13, inside an annular recess 37 provided along the tire circumferential direction. The annular recess 37 is recessed from the sidewall reference plane 14 (Figures 2 and 3) toward the tire inner surface with the same radial width.

The sidewall reference surface 14 refers to the surface of the tire side surface 13 facing axially outward of the sidewall 12 in a portion where partial irregularities such as protrusions or recesses, such as side blocks, are not formed.

The undulating surface 30 is formed so as to protrude in the tire axial direction inside the annular recess 37, with valley lines 38 at multiple locations in the tire radial direction on the bottom surface of the annular recess 37, and so that valleys and peaks alternate in the tire radial direction. The ridge lines 31, which are the tops of the multiple angle-shaped protrusions 35 that are peaks, and the multiple valley lines 38 are each aligned at equal intervals in the tire radial direction. As a result, the undulating surface 30 is formed so as to rise in the tire axial direction from the bottom surface of the annular recess 37. As a result, the undulating surface 30 changes periodically in the tire radial direction.

The radial ends of the undulating surface 30 are connected to the wall surfaces of the annular recess 37 at both radial ends. The height H1 (Figure 4) from the valley line 38 of the undulating surface 30 to the ridge line 31 of the angled protrusion 35 is slightly greater than the depth D (Figure 4) from the opening end 39 of the annular recess 37 to the valley line 38 on the bottom surface. As a result, the area near the ridge line 31 of each angled protrusion 35 protrudes outward beyond the opening end 39 of the annular recess 37.

As shown in Figure 4, the height H1 of the undulating surface 30 is, for example, 0.3 mm or more and 1.1 mm or less. Meanwhile, the depth D of the annular recess 37 is 0.2 mm or more and 1.0 mm or less, and it is preferable that the vicinity of the ridge line 31 of the angled protrusion 35 protrudes outward from the opening end 39 of the annular recess 37 by 0.1 mm or more. By having the vicinity of the ridge line 31 of the angled protrusion 35 protrude outward from the opening end 39 of the annular recess 37 in this way, the presence of the undulating surface 30 can be emphasized from the outside, thereby improving the design of the tire side surface 13.

As shown in Figures 3 and 5, the pitch P1 of the undulating surface 30, which is the distance between the ridgelines 31 of the angled protrusions 35 in the tire radial direction, which is perpendicular to the extension direction of the angled protrusions 35, is 3 mm or more and 80 mm or less. Preferably, the pitch P1 is 20 mm or more and 30 mm or less.

Furthermore, when the pitch of the undulating surface 30 is P1 and the height of the undulating surface 30 is H1, the radius of curvature of the peaks and valleys of the undulating surface 30 is (P1/2) or more and ((P1/H1) + P1) or less. The radius of curvature of the peaks and the valleys may be the same or different. For example, the radius of curvature of the peaks may be larger than the radius of curvature of the valleys.

In addition, as described above, the undulating surface 30 is formed so as to rise from the bottom surface of the annular recess 37 in the tire axial direction, which makes it easier to equalize the volume of the tire's rubber, makes it easier to form the undulating surface 30, and reduces the overall weight of the tire.

Furthermore, a plurality of curved protrusions 34 are provided on the surface of the undulating surface 30. The plurality of curved protrusions 34 are arranged at multiple positions in the tire radial direction and at multiple positions in the tire circumferential direction on the undulating surface 30. For example, the plurality of curved protrusions 34 may be arranged at approximately equal intervals at multiple positions in the tire radial direction and at multiple positions in the tire circumferential direction on the undulating surface 30.

The configuration of each curved protrusion 34 will be described with reference to Figure 5 above and Figures 6 and 7. Figure 6 is an enlarged perspective view of the curved protrusion 34. Figure 7 is a view of the curved protrusion 34 as seen from the outside in the height direction Z. Hereinafter, the curved protrusion 34 will be referred to as the protrusion 34.

As shown in Figure 6, each protrusion 34 protrudes from the undulating surface 30 in a generally conical shape. As a result, when viewed from the side perpendicular to the height direction Z of the protrusion 34, it has a triangular shape that is convex outward, and its horizontal length decreases toward the tip. The "horizontal direction" is the direction perpendicular to the height direction Z of the protrusion 34.

As shown in Figure 7, the shape of the base end of each protrusion 34 when viewed from the outside in the height direction is circular. Here, "circular" means that the length ratio between the vertical and horizontal directions, which are perpendicular to each other, is 0.85 or greater and 1.15 or less. In Figure 7, the vertical direction is the direction of arrow F, and the horizontal direction is the direction of arrow G. In other words, when the vertical length is LF and the horizontal length is LG, a "circular" shape is defined as one that satisfies 0.85≦LF/LG≦1.15.

By providing the protrusions 34 on the undulating surface 30 in this way, the contrast between the protrusions and recesses can be utilized to improve the design of the tire 1. Furthermore, when the vehicle is traveling, air can flow smoothly around the protrusions 34 on the undulating surface 30 along the curved outer edge, as indicated by arrows A1 and A2 in Figure 7, thereby suppressing increases in air resistance.

Furthermore, as indicated by the arrow β in Figure 5, each protrusion 34 protrudes in a direction perpendicular to the protrusion formation plane at the protrusion formation position on the undulating surface 30. The "protrusion formation plane" is the tangent plane when the protrusion 34 is assumed to be standing in contact with the undulating surface 30. In this way, each protrusion 34 protrudes in a direction perpendicular to the protrusion formation plane, which enhances the air resistance reduction effect described below. Furthermore, in areas where two protrusions 34 are located close to each other on either side of the valley line 38 of the valley portion of the undulating surface 30, shadows are likely to be generated between the protrusions 34. On the other hand, in areas where two protrusions 34 are located on either side of the ridge line 31 of the undulating surface 30, light is likely to be reflected between the protrusions 34. This makes it easier for light and dark contrasts to occur on the undulating surface 30.

Of the vertical length LF and horizontal length LG of the base end of the protrusion 34, the maximum length La, which is the longer length, is 0.15 mm or more and 5.0 mm or less, and it is preferable that the height of the protrusion 34 be 0.8 to 1.5 times this maximum length La, in terms of improving design and suppressing increases in air resistance. On the other hand, if the maximum length La is less than 0.15 mm, the effect of improving design is reduced. If the maximum length La exceeds 5.0 mm, the effect of suppressing increases in air resistance is reduced. If the height of the protrusion 34 is less than 0.8 times the maximum length La, the effect of improving design is reduced. If the height of the protrusion 34 exceeds 1.5 times the maximum length La, the effect of suppressing increases in air resistance is reduced.

Furthermore, as shown in Figure 5, when the spacing between adjacent protrusions 34 is P2 and the height of each protrusion 34 is H2, the protrusion spacing height ratio P2/H2 is between 2 and 6. This reduces the air resistance of the tire 1 while minimizing any deterioration in its appearance.

According to the tire 1 described above, the undulating curved surface 30 of the tire side surface 13 undulates radially with multiple angled protrusions 35. This allows the angled protrusions 35 to deflect and absorb vibrations from impacts received when driving over potholes or road bumps. Furthermore, the increased tire surface area suppresses increases in internal heat generation due to radial deflection. Furthermore, by providing the tire side surface 13 with a curved shape with few or no edges, turbulence caused by edges can be suppressed, thereby reducing air resistance. Furthermore, the multiple protrusions 34 facilitate contrast on the tire side surface 13. Meanwhile, the increased surface area of the undulating curved surface 30 facilitates streamlining of the flow near the surface of the undulating curved surface 30, which causes air to adhere to the surface, which is detrimental to reducing negative pressure. Meanwhile, the presence of protrusions 34 on the undulating curved surface 30 as described above facilitates air separation. This reduces the negative pressure of the air flowing over the undulating surface 30, thereby reducing air resistance. This achieves a balance between improved absorption of vibrations caused by bumps from the road surface while driving, suppression of internal heat buildup due to radial tire deflection, and reduced air resistance, while also making it easier to create contrast on the tire side surface 13.

In addition, even if mud gets into the multiple valleys of the undulating curved surface 30 on the tire side surface 13 while the tire is running, the angled protrusions 35 flex in the radial direction of the tire while the tire is running, expanding and contracting the spacing between the valleys. This allows the mud that has gotten into the valleys to be easily expelled, improving mud removal performance.

In addition, the ridges of the undulating surface 30 that extend in the circumferential direction of the tire allow the rubber near the tire side surface 13 at the bottom of the tire to easily deform vertically in response to changes in the road surface, which tends to increase the contact area. This improves wet braking performance on wet roads.

Figure 8 is a schematic diagram showing that, in an embodiment, after an airflow collides with a protrusion 34, turbulence causes the airflow to reattach to another protrusion 34 downstream, making the separation point more likely to shift downstream. In this embodiment, the protrusion-to-height ratio P2/H2 is between 2 and 6, so that the airflow that collides with a protrusion 34 on the undulating surface 30 becomes turbulent and heads downstream. This turbulence then collides again with another protrusion 34 downstream, and so on. This makes it easier for the separation point of the airflow on the undulating surface 30 to shift downstream. Therefore, as described below, the width of the wake region, which is formed by the portion sandwiched on both sides by the separated airflow from the separation position on the undulating surface 30 and creates negative pressure, can be reduced on the downstream side of the airflow in the tire. This reduces the pressure resistance caused by the formation of the protrusions 34, thereby suppressing an increase in air resistance.

Figure 9 is a schematic diagram showing how, in another embodiment, the surface of an undulating curved surface is less likely to generate turbulence, just like a smooth surface. When the projection spacing-height ratio P2/H2 is less than 2, as shown in Figure 9, the density of multiple projections 34a per unit area of the undulating curved surface increases. This makes the undulating surface similar to a smooth surface in relation to the airflow indicated by arrow δ, making it less likely to generate turbulence in the airflow. As a result, the separation point of the airflow on the undulating curved surface is less likely to shift downstream. This reduces the negative pressure reduction effect, and therefore reduces the effect of suppressing an increase in air resistance.

On the other hand, if the protrusion spacing height ratio P2/H2 exceeds 6, the number of protrusions 34 formed on the undulating surface will be reduced, resulting in a lower negative pressure reduction effect. In this case as well, the effect of suppressing an increase in air resistance will be reduced.

The effects of the embodiment will be explained in more detail using Figures 10 and 11. Figure 10 is a schematic diagram showing, using a cylinder Sa to simulate the generation of a wake region 40 due to separated airflow downstream of the tire side surface 13 in the airflow in another example configuration in which the protrusion spacing height ratio P2/H2 is less than 2. In Figure 10, many turbulent flows are formed within the wake region 40. In Figures 10 and 11, the tire is shown simulated by the cylinders Sa and S.

In another example shown in Figure 10, the protrusion spacing-height ratio P2/H2 is less than 2, so the undulating surface, like a smooth surface, does not generate turbulence. Consider this case: As the tire rotates during vehicle travel, an airflow, indicated by the dashed line, impinges on the surface of the cylinder Sa, which serves as the tire side surface 13. In this case, positive pressure is generated on the upstream side of the cylinder Sa, pushing the cylinder Sa downstream. As the airflow flows downstream along the surface of the cylinder Sa from the upstream side of the cylinder Sa, the airflow separates from the surface of the cylinder Sa at positions C1 and C2 in Figure 10. A wake region 40, where negative pressure exists, is formed in the area sandwiched between the separated airflows from the separation position of the cylinder Sa. In the case of Figure 10, the width (vertical length in Figure 10) of this wake region 40 is large, resulting in a smaller negative pressure reduction effect. For this reason, if the projection spacing height ratio P2/H2 is less than 2, the effect of suppressing increases in pressure resistance in the tire is low, and therefore the effect of suppressing increases in air resistance is also small.

Figure 11 is a schematic diagram showing, in an embodiment, how the width of the wake region 40 caused by the separated air flow narrows downstream of the tire side surface 13 in the air flow, thereby increasing the negative pressure reduction effect, using a cylindrical body S to simulate this. In Figure 11, the formation of multiple protrusions 34 on the tire side surface 13 on both sides of the tire in the axial direction is simulated by tiny protrusions formed on the surface of the cylindrical body S.

As shown in FIG. 11 , in this embodiment, the protrusion spacing-height ratio P2/H2 is between 2 and 6, both inclusive. Therefore, for the reasons explained in FIG. 8 , the separation point of the airflow from the tire side surface 13 is more likely to shift to downstream positions C3 and C4. This reduces the width of the wake region 40, which is formed downstream of the cylinder S simulating a tire and sandwiched between the separated airflow from the separation point on the surface of the cylinder S, and where negative pressure occurs. While FIG. 11 simulates multiple protrusions 34 formed on the tire side surface 13 on both axial sides of the tire, the width of the wake region 40 is also reduced even when multiple protrusions 34 are formed only on the tire side surface 13 on the vehicle's outer side, as in this embodiment. As a result, in this embodiment, the effect of suppressing an increase in pressure resistance in the tire is enhanced, thereby suppressing an increase in air resistance.

In addition, in an embodiment, the undulating surface 30 may be configured to be formed on the tire side surface 13 within a tire radial direction Y range (the range indicated by the arrow η in Figure 1) of 25% to 65% when the tire radial direction position of the rim line 20 is set to 0 and the tire cross-sectional height Ht is set to 100.

With this configuration, the undulating surface 30 can be provided in the range from the axially outer end (P in Figure 1) of the tire side surface 13, which corresponds to the maximum tire width, to the outer portion in the tire radial direction Y, where the air flow is likely to hit, to the outer peripheral portion of the tire, which is more noticeable and has a significant effect on improving design.

Figure 12 is a schematic diagram showing an example of when tire 1 of the embodiment goes over a road bump. As shown in Figure 12, when tire 1 goes over a road bump 112 on a road surface 110, vibrations are likely to occur on the tire side surface 13. However, because multiple angled protrusions 35 extending in the tire circumferential direction are provided on undulating surface 30, the vibrations are more easily absorbed by each angled protrusion 35, which has reduced rigidity in the tire radial direction. This improves the absorption of vibrations caused by impacts from the road surface 110 during driving, thereby improving ride comfort.

In addition, air flowing in the circumferential direction of the tire on the tire side surface 13 is more easily guided through the valleys of the undulating surface 30. Furthermore, near the tire's contact patch, the tire side surface 13 tends to expand axially outward, causing the airflow to tend to curl up. This curling increases the resistance of the airflow flowing rearward in the direction of travel of the tire 1. According to this embodiment, this curling can be suppressed by the peaks of the undulating surface 30, further reducing air resistance.

Figure 13 is a cross-sectional view showing a tire molding mold according to an embodiment. The tire 1 of this embodiment is formed using a tire molding mold 70. Hereinafter, the tire molding mold 70 will be referred to as mold 70. Mold 70 is a mold used to mold the tire 1 shown in Figures 1 to 8 above. Mold 70 achieves a balance of high performance, including improved absorption of vibrations caused by impacts from the road surface during driving, suppression of increases in internal heat generation due to deflection in the tire's radial direction, and reduced air resistance, while also realizing a tire 1 that is more likely to produce contrast on the tire side surfaces.

Below, each component will be described according to the tire axial direction X and tire radial direction Y of the tire 1 described above molded using the mold 70.

The mold 70 has a tread mold 71 that molds the tread surface of the tire 1 and a pair of side molds 72 that mold the sidewall surfaces.

The tread mold 71 has a body 74 with a tread molding surface 73 and a protrusion 75 protruding from the tread molding surface 73.

The main body 74 is made of a metal material, such as an aluminum alloy. Suitable aluminum alloys include AC4 and AC7. The protrusions 75 form circumferential grooves in the tire 1. The protrusions 75 are made of the same metal material as the main body 74.

The side mold 72 has a main body 76 with side molding surfaces 77a, 77b. The side molding surface 77a, which forms the tire side surface on the outside of the vehicle, has an annular protrusion 78 that protrudes outward from the side molding surface 77a. The main body 76 is made of the same metal material as the main body 74. The annular protrusion 78 is the part that forms the annular recess 37 (Figures 2 to 4) in the tire 1, which has an undulating curved surface 30 on the inside.

The tread mold 71 has a fan shape in a plan view, formed by dividing an annular body into multiple circumferential segments. The multiple segments of the tread mold 71 form a continuous annular body with an inner diameter corresponding to the outer diameter of the tire 1 to be molded when clamped as described below. The upper side mold 72 is annular and fixed to the underside of an upper plate (not shown) constituting the vulcanization molding machine. It rises and falls in conjunction with the rise and fall of a first lifting member (not shown). The lower side mold 72 is annular and fixed to the floor surface and to the underside of a lower plate (not shown) constituting the vulcanization molding machine. The vulcanization molding machine raises and lowers multiple segments (not shown), one for each tread mold 71, outside the multiple segments using a first lifting member. Simultaneously with the raising and lowering of the first lifting member, the vulcanization molding machine vertically slides the inclined surfaces of the outer peripheral surfaces of the multiple segments on an inclined cylindrical surface provided at the lower end of a second lifting member (not shown) that rises and falls independently of the first lifting member. As a result, the vulcanization molding machine moves multiple segments back and forth radially relative to the central axis of the annular, continuous tread mold 71. In this way, the vulcanization molding machine switches the mold 70 between a mold clamped state and a mold open state.

In the mold 70 configured in this manner, a green tire is placed on the lower tread mold 71 with the tire axial direction aligned vertically when the mold is open. An inflatable bladder is then placed inside the green tire and inflated by supplying air to the bladder. Then, with the inner surface of the green tire held by the outer surface of the bladder, the first and second lifting members are raised and lowered to close the mold 70. The rubber of the green tire is pressed against the tread molding surface 73 and side molding surfaces 77a, 77b by the pressure from the mold 70, and a heat exchange medium adjusted to a predetermined temperature is constantly flowing between the member fixing the upper plate and the member fixing the lower plate. This vulcanizes the rubber of the green tire, completing the tire 1 with the predetermined shape.

In this embodiment, an annular protrusion 78 is formed on the side molding surface 77a, which forms the tire side surface 13 on the vehicle outer side, to mold the annular recess 37 having an undulating surface 30 on the inside. The ridge line 78a at the top of the annular protrusion 78 corresponds to the valley line 38 of the valley of the annular recess 37. Furthermore, a mold-side curved surface 80 is formed on the side of the annular protrusion 78 so as to undulate in the radial direction, corresponding to the undulating surface 30. Multiple inner-surface recesses (not shown) are formed on the mold-side curved surface 80 to correspond to the multiple protrusions 34 of the undulating surface 30.

The multiple recesses within the curved surface of the mold can be formed by drilling holes in the mold-side curved surface 80 of the mold. For example, NC machining using a cutting tool such as an end mill, laser machining, or electric discharge machining can be used for drilling holes.

The tire obtained using the tire 1 and mold 70 described above achieves a balance of high performance, including improved absorption of vibrations caused by impacts from the road surface during driving, suppression of increases in internal heat generation due to radial deflection of the tire, and reduced air resistance, while also producing a tire 1 that is more likely to produce contrast on the tire side surface.

In the above embodiment, the shape of the protrusion 34 when viewed from the side perpendicular to the height direction is triangular, but in the present invention, the curved protrusion is not limited to this shape. Figures 14 to 17 show four examples of curved protrusions in tires according to other embodiments.

First, the protrusion 34b of the first example shown in Figure 14 has a truncated cone shape when viewed from the side, which is a trapezoid with inclined sides 32 on both sides in the horizontal direction. When viewed from the outside in the height direction, the protrusion 34b has a circular shape, similar to the protrusion 34 shown in Figure 7.

The second example of the protrusion 34c shown in Figure 15 has a cylindrical shape that is roughly rectangular when viewed from the side. When viewed from the outside in the height direction, the shape of the protrusion 34c is circular, similar to the protrusion 34 shown in Figure 7.

The protrusion 34d of the third example shown in Figure 16 has a hemispherical shape when viewed from the side. When viewed from the outside in the height direction, the shape of the protrusion 34d is circular, similar to the protrusion 34 shown in Figure 7.

The fourth example of the protrusion 34e shown in Figure 17 has a mountain-like shape when viewed from the side, with inclined sides 33a on both sides in the horizontal direction, and a curved portion 33b that has an arcuate portion at the top and is convex outward, connected to it. The shape of the protrusion 34e when viewed from the outside in the height direction is circular, similar to the protrusion 34 shown in Figure 7.

Figure 18 is a perspective view showing a protrusion 34f in a tire according to another embodiment. Figure 19 is a view as viewed in the direction of arrow C in Figure 18. Figure 20 is a cross-sectional view taken along line D-D in Figure 19. Figure 21 is a cross-sectional view taken along line E-E in Figure 19.

The protrusions 34f in the tire of this example have a shape that creates a sense of brightness based on strong contrast on the tire side surface when viewed from a direction perpendicular to the undulating surface 30. Specifically, as described below, the protrusions 34f in this example are polygonal, having two first surfaces 83 that rise from the undulating surface 30 at an angle within a range of ±15% based on a surface that stands upright at 90 degrees to the undulating surface 30, and two second surfaces 84 that are connected to the first surfaces 83 at their apexes and rise at an angle greater than 90 degrees + 15% relative to the undulating surface 30.

The two first surfaces 83 are identically shaped rectangles and are connected to each other in a V-shape. The two second surfaces 84 are connected to each first surface 83, are connected to each other in a V-shape, and are symmetrical with respect to the connecting line 85 between the two second surfaces 84. Furthermore, the protrusion 34f has two triangular third surfaces 88 connected to the first surface 83 and the second surface 84 at both ends of its length along the ridge line 87 of the V-shape. As shown in FIG. 19, each second surface 84 has a diamond shape when viewed in a direction perpendicular to the position of the protrusion 34f on the undulating surface 30. Furthermore, as shown in FIG. 20, the position of each second surface 84 increases as it approaches the ridge line 87 of the V-shape (FIGS. 18 and 19).

As shown in Figure 20, each first surface 83 of each protrusion 34f rises from the undulating surface 30 at an angle α1 within a range of ±15% based on a surface S1 that stands upright at 90 degrees to the undulating surface 30. Furthermore, each second surface 84 of each protrusion 34f is connected to the first surface 83 by a ridge line 87 and rises so as to be inclined at an angle α2 greater than 90 degrees + 15% relative to the undulating surface 30.

The first surfaces 83 of the projections 34f shown in Figure 20 extend from the undulating surface 30 at the same angle α as the surface S1 that extends perpendicularly at 90 degrees to the undulating surface 30, but they may extend from the undulating surface 30 at an angle greater than 90 degrees or less than 90 degrees, within the range of 90 degrees ±15%. Furthermore, the second surfaces 84 of the projections 34f may extend from the undulating surface 30 at an angle greater than 90 degrees + 30%, or more preferably, at an angle greater than 90 degrees + 50%.

As a result, the second surface 84 forms a light-reflecting surface on the undulating curved surface 30, and the first surface 83 creates shadow areas such as black lines, thereby giving the tire side surface a strong contrast. This allows the tire side surface to be given an excellent shine by utilizing the reflection of light, resulting in a tire with a highly aesthetic design.

Here, unlike the embodiment, consider a case in which each first surface 83 of each protrusion 34f extends from the undulating surface 30 at an angle exceeding +15% with respect to a surface S1 that is perpendicular to the undulating surface 30 at an angle of 90 degrees (for example, as shown by the dashed dotted line α3 in Figure 20, the angle between the surface S1 and the undulating surface 30 is greater than θ1, which is an angle of +15% with respect to the 90-degree surface S1). In this case, the increase in brightness due to the first surface 83 exceeds 15%, making it difficult to create a contrast between light and dark on the tire side surface.

Also, unlike the embodiment, consider a case in which each first surface 83 of each protrusion 34f extends from the undulating surface 30 at an angle of less than -15% relative to a surface that is perpendicular to the undulating surface 30 at 90 degrees (for example, as shown by the dashed dotted line α4 in Figure 20, the angle between the first surface 83 and the undulating surface 30 is smaller than θ2, which is an angle of -15% relative to the 90-degree surface S1). In this case, the so-called under-angle becomes larger, and the difference in brightness on the tire side surface becomes greater, but there is a risk of the rubber tearing when the molded tire is removed from the mold during tire molding, reducing moldability.

As shown in the embodiment of Figures 18 to 21, the first surface 83 of each protrusion 34f extends from the undulating surface 30 at an angle within a range of ±15% relative to the surface S1 that is perpendicular to the undulating surface 30 at an angle of 90 degrees. This prevents such problems, facilitates the creation of a contrast between light and dark on the tire side surface, and maintains good tire formability.

In Figures 18 to 21, the protrusion 34f on the undulating surface 30 is described as a six-sided polygon including two first surfaces 83 and two second surfaces 84. However, the protrusion may be any polygon having at least one first surface and one second surface. For example, the protrusion may have a single first surface extending from the undulating surface at an angle within a range of ±15% relative to a surface that is perpendicular to the undulating surface at 90 degrees, and a single second surface connected at its apex to the first surface and inclined at an angle greater than 90 degrees + 15% relative to the undulating surface, resulting in a four-sided polygon including third surfaces at both ends. In this example, the remaining configuration and operation are the same as those in Figures 1 to 8.

Figure 22 is a view of a protrusion 34g in a tire according to another embodiment, viewed from the outside in the height direction. In this example, the shape of the protrusion 34g when viewed from the outside in the height direction is triangular, and the protrusion 34g can be a triangular pyramid or triangular prism. Furthermore, in the shape of the base end of the protrusion 34g when viewed from the outside in the height direction, the ratio (LF1/LG1) of the longitudinal length LF1 to the lateral length LG1, which are perpendicular to each other, can be 0.85 to 1.15. Furthermore, the height of each protrusion 34g can be 0.8 to 1.5 times the longer of the longitudinal length LF1 and the lateral length LG1.

Figure 23 is a view of a protrusion 34h in a tire according to another embodiment, viewed from the outside in the height direction. In this example, the shape of the protrusion 34h when viewed from the outside in the height direction is a parallelogram, and the protrusion 34h can also be a square pyramid or square prism. Furthermore, in the shape of the base end of the protrusion 34h when viewed from the outside in the height direction, the ratio (LF2/LG2) of the longitudinal length LF2 to the lateral length LG2, which are perpendicular to each other, can be 0.85 to 1.15. Furthermore, the height of each protrusion 34h can be 0.8 to 1.5 times the longer of the longitudinal length LF2 and the lateral length LG2.

Figure 24 is a view of a protrusion 34i in a tire according to another embodiment, viewed from the outside in the height direction. In this example, the shape of the protrusion 34i when viewed from the outside in the height direction is a regular pentagon, and the protrusion 34i can also be a pentagonal pyramid or pentagonal prism. Furthermore, in the shape of the base end of the protrusion 34i when viewed from the outside in the height direction, the ratio (LF3/LG3) of the longitudinal length LF3 to the lateral length LG3, which are perpendicular to each other, can be 0.85 to 1.15. Furthermore, the height of each protrusion 34i can be 0.8 to 1.5 times the longer of the longitudinal length LF3 and the lateral length LG3.

Also, although not shown in the figures, another example of the protrusion may be a hexagonal pyramid or hexagonal prism, which has a regular hexagonal shape when viewed from the outside in the height direction.

Figure 25 is a view corresponding to Figure 5 of a tire according to another embodiment. Unlike the configurations of Figures 1 to 8, the configuration of this example has multiple protrusions 34 protruding parallel to each other from the undulating surface 30 and facing outward in a direction perpendicular to the sidewall reference plane. With the configuration of this example, when the spacing between the multiple protrusions 34 is reduced, the light absorption effect can be improved, making the spaces between the protrusions 34 darker and easier to contrast with other bright areas.

Figure 26 is a schematic diagram showing the light absorption effect achieved by the configuration of Figure 25. In the configuration of Figure 25, as shown in Figure 26, when the spacing between multiple protrusions 34 is small and light enters between the protrusions from the outside, it is more likely to penetrate deeper between the protrusions 34 while being reflected by the side surfaces of the protrusions 34, as indicated by arrows β1, β2, and β3. This increases the light absorption effect of the configuration of this example. In this example, the other configurations and functions are the same as those of the configurations of Figures 1 to 8.

In the above embodiments, the tire side surface 13 is provided with an annular portion 100 including an undulating surface 30, which is continuous around the entire tire circumferential direction. However, in the above embodiments, the tire side surface may instead include an arc-shaped portion that is provided only in a portion of the tire circumferential direction or in multiple locations around the tire circumferential direction, with an arc-shaped recess having an arc-shaped undulating surface formed inside. The arc-shaped portion has an undulating surface that undulates in the tire radial direction, with multiple angle-shaped protrusions formed in the tire radial direction, inside the arc-shaped recess along the tire circumferential direction. The arc-shaped portion is preferably formed in a band-like area extending in the tire circumferential direction that is 25% or more of the entire tire circumferential circumference. The undulating surface may also be formed in four or more locations around the tire circumferential direction, for example. The undulating surface may also be formed in four or more locations around the tire circumferential direction, for example. Furthermore, when the undulating surfaces are arranged in multiple positions around the tire, the total circumferential length of each undulating surface is preferably 50% or more of the total circumferential length of the tire at the radial position of the undulating surface. Regarding the circumferential range of the undulating surface, the proportion of the total circumferential length of the portion where the undulating surface is arranged to the entire circumference of the sidewall is preferably 50% or more, more preferably 80% or more, and most preferably the entire circumference (100%).

In addition, instead of the annular protrusion 78 formed on the side molding surface 77a of the mold 70 shown in Figure 13, multiple arc-shaped portions having an arc-shaped mold side curved surface for molding an arc-shaped undulating surface may be formed.

In addition, in each of the above embodiments, an undulating surface 30 is formed inside an annular or arc-shaped recess formed in the tire side surface 13. However, an undulating surface may be formed that protrudes axially outward from the sidewall reference plane of the tire side surface, and that undulates in the tire radial direction so as to have multiple angle-shaped protrusions in the tire radial direction.

In addition, in each of the above embodiments, although not shown in the drawings, markings such as letters or symbols may be provided on the undulating surface. In addition, in each of the above embodiments, if the undulating surface is provided at a portion of the sidewall in the circumferential direction, or at multiple positions in the circumferential direction, markings such as letters or symbols may be provided on a curved surface or smooth surface that is located at the same radial position as the undulating surface and does not have a undulating surface.

The present disclosure is further illustrated by the following embodiments.
Configuration 1: The tire side surface is provided on the tire radially inner side of the tread contact edge and on the tire radially outer side of the rim line, which is the tire axially outer surface, and includes an undulating curved surface that undulates in the tire radial direction so as to have a plurality of angle-shaped protrusions in the tire radial direction,
Each of the plurality of angle-shaped protrusions extends in the tire circumferential direction, and a plurality of curved protrusions are provided on the surface of the undulating curved surface.
Pneumatic tires.
Configuration 2: When each of the plurality of curved protrusions is viewed from the outside in the height direction, the shape of the base end of the curved protrusion is a circle with a length ratio between the vertical and horizontal directions, which are perpendicular to each other, of 0.85 to 1.15.
2. The pneumatic tire according to claim 1.
Configuration 3: The height of each of the plurality of curved protrusions is 0.8 to 1.5 times the longer of its length in the vertical direction or its length in the horizontal direction.
3. The pneumatic tire according to claim 2.
Configuration 4: When the arrangement interval between adjacent curved projections is P2 and the height of each of the plurality of curved projections is H2, P2/H2 is 2 or more and 6 or less.
4. The pneumatic tire according to configuration 3.
Configuration 5: The undulating surface is provided continuously over the entire circumference in the tire circumferential direction.
5. The pneumatic tire of any one of configurations 1 to 4.
Configuration 6: A recessed portion recessed from a sidewall reference plane toward the tire inner surface is formed on the tire side surface, and the undulating surface is formed so as to rise from the bottom surface of the recessed portion in the tire axial direction.
6. The pneumatic tire of any one of configurations 1 to 5.
Configuration 7: The undulating curved surface changes periodically in the tire radial direction,
The pitch of the undulating curved surface is 3 mm or more and 80 mm or less,
The height of the undulating surface is 0.3 mm or more and 1.1 mm or less.
7. The pneumatic tire of any one of configurations 1 to 6.
Configuration 8: When the pitch of the undulating surface is P1 and the height of the undulating surface is H1, the radius of curvature of the peaks and valleys of the undulating surface is (P1/2) or more ((P1/H1)+P1) or less.
8. The pneumatic tire according to claim 7.
Configuration 9: The undulating surface is formed on the tire side surface within a tire radial range of 25% to 65% when the tire radial position of the rim line or the axially outer end of the rim protector is set to 0 and the tire cross-sectional height is set to 100.
9. The pneumatic tire of any one of configurations 1 to 8.
Configuration 10: A pneumatic tire mold for molding the pneumatic tire according to any one of Configurations 1 to 9,
The molding surface has a mold-side curved surface corresponding to the undulating curved surface, and a plurality of curved surface recesses corresponding to the curved surface protrusions are formed on the mold-side curved surface.
Mold for molding pneumatic tires.

1 Pneumatic tire (tire), 10 Tread, 11a, 11b Block, 11c Circumferential groove, 12 Sidewall, 13 Tire side surface, 14 Sidewall reference surface, 15 Bead, 18 Rim strip, 19 Rim protector, 20 Rim line, 30 Wavy curved surface, 31 Ridge line, 32 Inclined edge, 33a Inclined edge, 33b Curved portion, 34, 34a, 34b, 34c, 34d, 34e, 34f, 34g, 34i Curved surface protrusion (protrusion), 35 Angular protrusion, 37 Annular recess, 38 Valley line, 39 Opening end, 40 Wake region, 70 Tire molding mold, 71 Tread mold, 72 Side mold, 73 Tread molding surface, 74 Main body, 75 Protrusion, 76 Main body, 77a, 77b Side molding surface, 78 Annular protrusion, 78a ridge line, 80 mold side curved surface, 83 first surface, 84 second surface, 85 connecting line, 87 ridge line, 88 third surface, 100 annular portion, 110 road surface, 112 road surface step, T ground contact edge.

Claims (10)

The tire side surface is provided on the tire radially inner side of the tread contact edge and on the tire radially outer side of the rim line, which is the tire axially outer surface, and has an undulating curved surface that undulates in the tire radial direction so as to have a plurality of angle-shaped protrusions in the tire radial direction,
Each of the plurality of angle-shaped protrusions extends in the tire circumferential direction, and a plurality of curved protrusions are provided on the surface of the undulating curved surface.
Pneumatic tires. a base end of each of the plurality of curved projections when viewed from the outside in the height direction has a circular shape with a length ratio between vertical and horizontal directions that are orthogonal to each other of 0.85 to 1.15;
The pneumatic tire according to claim 1 . The height of each of the plurality of curved protrusions is 0.8 to 1.5 times the longer of the vertical length and the horizontal length.
The pneumatic tire according to claim 2. When the arrangement interval between adjacent curved protrusions is P2 and the height of each of the plurality of curved protrusions is H2, P2/H2 is equal to or greater than 2 and equal to or less than 6.
The pneumatic tire according to claim 3. The undulating surface is provided continuously around the entire circumference in the tire circumferential direction.
The pneumatic tire according to claim 1 . a recess formed in the tire side surface from a sidewall reference plane toward the tire inner surface, and the undulating surface is formed so as to rise from the bottom surface of the recess in the tire axial direction;
The pneumatic tire according to claim 1 . the undulating surface changes periodically in the tire radial direction,
The pitch of the undulating curved surface is 3 mm or more and 80 mm or less,
The height of the undulating surface is 0.3 mm or more and 1.1 mm or less.
The pneumatic tire according to claim 1 . When the pitch of the undulating surface is P1 and the height of the undulating surface is H1, the radius of curvature of the peaks and valleys of the undulating surface is (P1/2) or more ((P1/H1)+P1) or less.
The pneumatic tire according to claim 7. The undulating surface is formed on the tire side surface within a tire radial direction range of 25% to 65% when the tire radial direction position of the rim line or the tire axial outer end of the rim protector is set to 0 and the tire cross-sectional height is set to 100.
The pneumatic tire according to claim 1 . A pneumatic tire mold for molding the pneumatic tire according to any one of claims 1 to 9,
A mold for molding pneumatic tires has a mold-side curved surface on the molding surface that corresponds to the undulating curved surface, and a plurality of curved surface recesses corresponding to the curved surface protrusions are formed on the mold-side curved surface.