JP5400286B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire including a protrusion that generates turbulent flow.

  In general, an increase in tire temperature in a pneumatic tire promotes a change over time such as a change in material properties, or causes a damage of a tread portion at high speed running, which is not preferable from the viewpoint of durability. . To improve durability, especially in off-the-road radial tires (ORR), truck / bus radial tires (TBR), and run-flat tires during puncture (running at an internal pressure of 0 kPa), which are used under heavy loads Reducing tire temperature has become a major issue.

  For example, in a run flat tire having a side wall reinforcing layer having a crescent-shaped cross section, deformation in the tire radial direction is concentrated on the side wall reinforcing layer during puncturing, and the side wall reinforcing layer reaches a very high temperature, resulting in durability. Has a great influence on sex.

  As a means for reducing the tire temperature in such a pneumatic tire, a reinforcing member for reducing and suppressing distortion of each component of the pneumatic tire (particularly, a carcass layer and a bead portion located in a sidewall portion) is provided. A technique for preventing temperature rise due to tire distortion as much as possible has been disclosed (for example, see Patent Document 1).

  However, in the conventional pneumatic tire described above, the provision of the reinforcing member may cause an unintended new failure such as an increase in tire weight or separation (peeling) at the reinforcing member. There is a problem that the normal running performance such as the riding comfort is deteriorated. In particular, in a run-flat tire, there is a concern that the vertical spring (elasticity in the tire longitudinal direction) during normal internal pressure travel is increased and the normal travel performance is deteriorated, and a technique that does not impair this normal travel performance is required.

  On the other hand, tires having a large number of protrusions on the tire surface have been conventionally proposed. Conventional protrusions are intended to make the unevenness generated in the sidewall portion of the tire inconspicuous (for example, refer to Patent Document 2) or to improve the crack resistance performance of the paddle portion (for example, refer to Patent Document 3). Met.

Here, the inventor has paid attention to that the protrusion provided on the tire surface can be a means for reducing the tire temperature. That is, when the tire rotates, an air flow flows along the tire surface, and heat exchange is performed between the air flow and the tire surface, so that the tire temperature can be reduced. However, since the airflow flowing on the flat tire surface is a smooth flow along the tire surface, positive heat exchange is not performed with the tire surface, and heat exchange efficiency is poor. On the other hand, the airflow flowing on the tire surface provided with the protrusions becomes turbulent flow due to the protrusions. The turbulent flow has a higher flow velocity than the smooth air flow, and the air flow having a higher flow velocity promotes heat exchange. Further, since the turbulent flow has a very high probability of hitting the tire surface smoothly compared to the air flow, heat exchange is promoted. For this reason, by providing protrusions on the tire surface, positive heat exchange is performed between the turbulent air and the tire surface, which can be a means for reducing the tire temperature.
JP 2006-76431 A Japanese Patent Laid-Open No. 11-32143 JP 2002-205514 A

  However, since the protrusion provided on the tire surface also serves as a hindrance when the heat inside the tire is dissipated from the tire surface, that is, promotes heat storage, simply providing the protrusion on the tire surface reduces the tire temperature. I can't.

  Then, an object of this invention is to provide the pneumatic tire which can aim at reduction of tire temperature by providing a protrusion on the tire surface on appropriate conditions.

  A feature of the present invention is a pneumatic tire in which a large number of protrusions are provided on the tire surface, each protrusion having a height in the range of 0.3 to 5 mm, and air flow with respect to the tire surface. The gist of the present invention is that the angle formed by the front wall surface on the side where the abuts is in the range of 70 to 110 degrees.

  According to such a configuration, the airflow flowing on the tire surface becomes turbulent due to the protrusions, and positive heat exchange is performed between the turbulent flow and the tire surface.

  Here, if the height of the protrusion is less than 0.3 mm, the upper air flow that flows through the upper portion of the protrusion passes through the air flow almost without bending, so that the heat exchange is actively promoted. If the turbulent flow cannot be generated and the height of the protrusion exceeds 5 mm, the heat storage by the protrusion becomes too large. On the other hand, when the height of the protrusion is in the range of 0.3 mm to 5 mm, a turbulent flow that actively promotes heat exchange can be generated, and heat storage by the protrusion can be suppressed to be small.

  In addition, when the angle of the front wall surface of the protrusion is less than 70 degrees with respect to the tire surface, among the airflows that have collided with the protrusion, the upper airflow that flows upward from the protrusion has a smaller separation angle from the protrusion. A gentle downward flow does not occur on the downstream side of the protrusion, and effective heat exchange with the tire surface cannot be promoted. Also, if the angle of the front wall surface of the protrusion with respect to the tire surface exceeds 110 degrees, among the airflows that collided with the protrusion, the upper airflow that flows toward the top of the protrusion has an excessively large separation angle with the protrusion. Since it flows in a direction away from the protrusion and is unlikely to flow downward on the downstream side of the protrusion, effective heat exchange with the tire surface cannot be promoted. On the other hand, when the angle of the front wall surface of the protrusion is in the range of 70 to 110, the upper air flow that flows upward of the protrusion out of the air flow that collides with the protrusion has an appropriate separation angle with the protrusion. Since the downflow flows downstream from the protrusion and hits the tire surface, positive heat exchange is performed with the tire surface. For this reason, the tire temperature can be reliably reduced by the protrusions provided on the tire surface.

  The width dimension of each protrusion is preferably in the range of 0.3 mm to 5 mm. If the width of the protrusion is less than 0.3 mm, the side airflow that flows through the side of the protrusion passes through the side of the protrusion almost without bending, so that the heat exchange is actively promoted. If the turbulent flow cannot be generated and the width of the protrusion exceeds 5 mm, the heat storage by the protrusion becomes too large. On the other hand, when the width of the protrusion is in the range of 0.3 mm to 5 mm, a turbulent flow that actively promotes heat exchange can be generated, and heat storage by the protrusion can be suppressed to a low level. For this reason, the tire temperature can be reliably reduced by the protrusions provided on the tire surface.

  Furthermore, each protrusion preferably has an angle formed by the side wall surface with respect to the tire surface in a range of 70 degrees to 110 degrees. If the angle of the side wall surface of the protrusion is less than 70 degrees, heat storage in the protrusion becomes too large. When the angle of the side wall surface of the protrusion exceeds 110 degrees, the side air flow that flows toward the side of the protrusion out of the air flow that collides with the protrusion flows in the direction away from the protrusion and is downstream of the protrusion. Since it does not become a return flow, it is not possible to form a heat dissipation region where a predetermined heat dissipation effect is expected around the protrusion. On the other hand, in the range of the angle of the side wall surface of 70 to 110, the side air flow that flows toward the side of the protrusion out of the air flow that collides with the protrusion forms a return flow downstream of the protrusion. In addition, it is possible to form a heat dissipation region in which a predetermined heat dissipation effect can be expected around the protrusion, and to suppress heat storage by the protrusion. For this reason, the tire temperature can be reliably reduced by the protrusions provided on the tire surface.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which can aim at reduction of tire temperature with the protrusion provided in the tire surface can be provided.

  Hereinafter, a pneumatic tire according to an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings is contained. 1 to 6 show an embodiment of the present invention, FIG. 1 is a perspective view showing a state in which a part of a pneumatic tire is broken, and FIG. 2 is a cross-sectional view in the tread width direction of the pneumatic tire. 3 is a perspective view of the protrusion, FIG. 4 is a perspective view showing a state in which the air flow hitting the protrusion becomes a turbulent flow, and FIG. 5A is a view as viewed from the arrow A in FIG. FIG. 5 and FIG. 5B are views of the protrusions as viewed from above, showing the flow of the side air flow, and FIG. 6 is a view taken in the direction of arrow B in FIG.

(Composition of pneumatic tire)
As shown in FIGS. 1 and 2, the pneumatic tire 1 has a pair of bead portions 3 including at least a bead core 3a and a bead filler 3b. The pneumatic tire 1 has a carcass layer 5 that is folded around the bead core 3a from the inner side in the tread width direction toward the outer side in the tread width direction and extends in a toroidal shape via the sidewall portion SW. On the inner side in the tread width direction of the carcass layer 5, a crescent-shaped side wall reinforcing layer 7 that reinforces the sidewall portion SW in the cross section in the tread width direction is provided. An inner liner 9, which is a highly airtight rubber layer corresponding to a tube, is provided on the inner side in the tread width direction of the sidewall reinforcing layer 7.

  A belt layer 11 is provided outside the carcass layer 5 in the tire radial direction. The belt layer 11 includes a first belt layer 11A and a second belt layer 11B in which a cord is inclined with respect to the tire circumferential direction, and a circumferential belt layer in which the cord is arranged substantially parallel to the tire circumferential direction. 11C.

  A tread portion 13 in contact with the road surface is provided on the outer side of the belt layer in the tire radial direction. A large number of protrusions 17 are provided at intervals in the circumferential direction of the tire surface 15 of the sidewall portion SW.

(Projection arrangement, arrangement density)
As shown in FIG. 1, the plurality of protrusions 17 are arranged at predetermined intervals in the circumferential direction and the tire radial direction, and are adjacent to the row along the circumferential direction and the tire radial direction thereto. The columns are arranged at positions shifted from each other by ½ interval. That is, the many protrusions 17 are arranged in a staggered arrangement. The many protrusions 17 are provided at an arrangement density of 0.1 to 13 pieces / cm ² .

(Structure of protrusion)
As shown in FIG. 3, each protrusion 17 is a quadrangular prism having a trapezoidal shape when viewed from above. The width dimension D of each protrusion 17 is set in the range of 0.3 mm to 5 mm. The height dimension H of each protrusion 17 is set in the range of 0.3 mm to 5 mm. Each protrusion 17 has an angle θ <b> 1 formed by the front wall surface 17 a on the side where the air flow strikes the tire surface 15 in a range of 70 to 110 degrees. Each projection 17 has an angle θ <b> 2 and θ <b> 3 formed by the side wall surface 17 c with respect to the tire surface 15 in a range of 70 degrees to 110 degrees. In the present embodiment, the width dimension D and the height dimension H indicate the maximum values of the protrusions 17, respectively. The tire surface indicates the outer surface and the inner surface of the tire.

(Function of protrusion)
In the above configuration, when the pneumatic tire 1 rotates, an air flow “a” in the direction opposite to the tire rotation direction relatively flows in the vicinity of the tire surface 15 as shown in FIG. This air flow a hits each projection 17. As shown in FIGS. 5A and 5B, the air flow a hitting the front wall surface 17a of the protrusion 17 flows along the upper air flow a1 flowing upward from the upper wall surface 17b and the left and right side wall surfaces 17c. The flow is mainly divided into a pair of side air flows a2 and becomes a turbulent flow. Since the air flow a flowing through the tire surface 15 becomes a turbulent flow in this way, heat exchange is actively performed with the tire surface 15 as compared with the air flow flowing regularly and smoothly on the tire surface 16.

  Here, when the height H of the protrusion 17 is less than 0.3 mm, the upper air flow a1 flowing through the upper portion of the protrusion 17 passes through the air flow a with almost no bending, so that heat exchange is actively performed. Turbulent flow of a magnitude that can be promoted automatically cannot be generated. If the height H of the protrusion 17 exceeds 5 mm, the heat storage in the protrusion 17 becomes too large. On the other hand, when the height H of the protrusions 17 is in the range of 0.3 mm to 5 mm, turbulent flow that can actively promote heat exchange can be generated, and heat storage by the protrusions 17 can be suppressed. .

  Further, in the protrusion 17, an angle θ <b> 1 formed by the front wall surface 17 a on the side where the air flow strikes the tire surface 15 is set in a range of 70 degrees to 110 degrees. As shown in FIG. 5A, when the angle θ1 of the front wall surface 17a of the protrusion 17 is less than 70 degrees, the upper airflow that flows upward of the protrusion 17 in the airflow a that collides with the protrusion 17 In a1, the peeling angle β with the protrusion 17 becomes small, and only a gentle downward flow is changed on the downstream side of the protrusion 17, and no positive heat exchange is performed with the tire surface 15. When the angle θ1 of the front wall surface 17a of the protrusion 17 exceeds 110 degrees, the upper air flow a1 that flows upward of the protrusion 17 in the air flow a that has collided with the protrusion 17 has a separation angle β with respect to the protrusion 17. It is so large that it flows in the direction away from the protrusion 17 (the direction of the arrow b in FIG. 5A), and is unlikely to flow downward on the downstream side of the protrusion 17. For this reason, positive heat exchange with the tire surface 15 is not performed.

  On the other hand, when the angle θ1 of the front wall surface 17a of the protrusion 17 is in the range of 70 to 110, the upper air flow a1 has a large separation angle β with the protrusion 17, and a strong downward flow on the downstream side of the protrusion 17. Thus, since it hits the tire surface 15, effective heat exchange with the tire surface 15 is performed. For this reason, the tire temperature can be reliably reduced by the protrusions 17 provided on the tire surface 15.

  In this embodiment, the width dimension D of each protrusion 17 is set in the range of 0.3 mm to 5 mm. If the width of the projection 17 is less than 0.3 mm, the side air flow a2 flowing through the side of the projection 17 passes through the side of the projection 17 with almost no bending, so that heat exchange with the tire surface 15 is almost achieved. It is not possible to generate a turbulent flow of a magnitude that actively promotes If the width D of the protrusion 17 exceeds 5 mm, the heat storage by the protrusion 17 becomes too large. On the other hand, when the width D of the protrusion 17 is in the range of 0.3 mm to 5 mm, a turbulent flow that actively promotes heat exchange is generated on the tire surface 15, and heat storage by the protrusion 17 is suppressed to a low level. be able to. As described above, the tire temperature can be reliably reduced by the protrusions 17 provided on the tire surface 15.

  In this embodiment, each projection 17 is set such that the angles θ2 and θ3 formed by the side wall surface 17c with respect to the tire surface 15 are in the range of 70 degrees to 110 degrees. When the angle of the side wall surface 17c of the protrusion 17 is less than 70 degrees, the heat storage in the protrusion 17 becomes too large. When the angles θ2 and θ3 of the side wall surface 17c of the protrusion 17 exceed 110 degrees, the side air flow a2 that flows toward the side of the protrusion 17 out of the airflow that collides with the protrusion 17 is generated from the protrusion 17. Since it flows in the direction away from (in the direction of arrow c in FIG. 5B) and does not return to the downstream of the protrusion 17, a heat dissipation region in which a predetermined heat dissipation effect can be expected cannot be formed around the protrusion 17. On the other hand, when the angles θ2 and θ3 of the side wall surface 17c are in the range of 70 degrees to 110, the side airflow a2 that flows toward the side of the protrusion 17 out of the airflow that collides with the protrusion 17 is the protrusion 17. Thus, a return flow is formed on the downstream side, a heat dissipation region in which a predetermined heat dissipation effect can be expected is formed around the protrusion 17, and heat storage by the protrusion 17 can be suppressed small. As described above, the tire temperature can be reliably reduced by the protrusions 17 provided on the tire surface 15.

In this embodiment, the arrangement density of the protrusions 17 is set in a range of 0.1 to 13 pieces / cm ² . Here, when the arrangement density of the protrusions 17 exceeds 13 / cm ² , the heat storage effect by the protrusions 17 becomes larger than the heat dissipation effect by the protrusions 17. Further, when the arrangement density of the protrusions 17 is less than 0.1 / cm ² , the turbulent flow area due to the protrusions is too small with respect to the area of the tire surface 15, and the heat dissipation effect by the protrusions 17 can hardly be expected. On the other hand, when the arrangement density of the projections 17 is in the range of 0.1 to 13 pieces / cm ² , a turbulent flow region can be generated in a sufficiently large range on the tire surface 15. Heat storage can also be suppressed to some extent. Therefore, by using such an arrangement density, the tire temperature can be reliably reduced by the protrusions 17 provided on the tire surface 15.

(Other embodiments)
In the above embodiment, the pneumatic tire 1 has the sidewall reinforcing layer 7 (run flat tire), but other tires, that is, the tire not having the sidewall reinforcing layer 7 (off-the-road radial). Tires), truck / bus radial tires, and the like.

  In the above embodiment, the protrusion 17 has a quadrangular prism shape, but the protrusion may have a cylindrical shape, and various other shapes are possible.

  In the above-described embodiment, the arrangement pattern of the protrusions 17 is arranged at equal intervals in the direction of the air flow a and the direction orthogonal thereto, but various arrangement patterns such as a staggered pattern are possible.

  In the above-described embodiment, the protrusion 17 is provided on the outer surface of the sidewall portion SW, but may be provided on the bottom surface 13a of the groove 13A formed in the tread portion 13 as shown in FIG. Further, as shown in FIG. 7B, the protrusion 17 may be provided on the side surface 13 b of the groove 13 </ b> A formed in the tread portion 13. By providing the protrusions 17 at such positions, the tire temperature can be reduced in the vicinity of the groove 13A formed in the tread portion 13 closest to the end portion of the belt layer 11 where separation (peeling) or cracks are likely to occur. Contributes to improved durability.

  Further, as shown in FIG. 8, the protrusion 17 may be provided on the inner surface of the inner liner 9 on the inner side in the tread width direction. By providing the protrusion 17 at this position, the tire temperature can be reduced from the tire inner surface side.

  In particular, it is effective in reducing the temperature of the tire inner surface in the punctured state of the pneumatic tire 1, and durability can be improved. Specifically, when the pneumatic tire 1 is in a punctured state, heat is exchanged between the inside air inside the tire and the outside air outside the tire through a hole opened in the pneumatic tire 1. At this time, since the protrusion 17 can accelerate the inside air inside the tire and heat exchange can be performed smoothly, the temperature of the tire inner surface in the punctured state can be reduced.

  In particular, in a pneumatic tire (run-flat tire) provided with the sidewall reinforcement layer 7, the temperature inside the tire becomes higher when a punctured state is obtained as compared to a pneumatic tire without the sidewall reinforcement layer 7. End up. For this reason, by providing the protrusion 17 inside the tire, the temperature inside the tire can be reduced and the durability can be improved.

〔Example〕
(Experiments regarding the height of protrusions and the angle of the front wall)
Similar to the above embodiment, the protrusion has a quadrangular prism shape, a width D of 2 mm, a height H of various dimensions in the range of 0.3 mm to 6 mm, and angles θ1, θ2 of the front wall surface and the side wall surface, θ3 is 90 degrees.

  Data on each pneumatic tire was measured under the following conditions.

Tire size: 285 / 50R20
Wheel size: 8JJ × 20
Internal pressure condition: 0 kPa (puncture state)
Load condition: 9.8kN
Each pneumatic tire is mounted on a drum testing machine installed indoors, rolled at a constant speed (90 km / h), and the durability distance until a pneumatic tire without a protrusion fails is set to 100, and there is a protrusion. The durability of the pneumatic tire was evaluated as a relative value. It can be inferred that the larger the index, the better the durability, that is, the temperature reduction characteristics.

  As shown in FIG. 9, it was confirmed by experiments that the durability (heat dissipation characteristics) is improved when the height H of the protrusion is in the range of 0.3 mm to 5 mm.

  As shown in FIG. 10, it was confirmed by experiment that the durability (heat radiation characteristic) was improved by the protrusion when the angle θ1 of the front wall surface of the protrusion was in the range of 70 to 110 degrees.

(Experiments regarding the angle of the side wall of the protrusion)
The experimental conditions regarding the angle of the side wall surface of the protrusion are the same as the above-described experimental contents. Experiments were performed on samples with different angles θ2 and θ3 on the side wall surfaces of the protrusions, and experimental results as shown in FIG. 11 were obtained.

  As shown in FIG. 11, it was confirmed by experiments that the durability (heat dissipation characteristics) was improved by the protrusions when the angles θ2 and θ3 of the side wall surfaces of the protrusions were in the range of 70 to 110.

(Experiment contents regarding the width of protrusions)
The experimental conditions regarding the width of the protrusions are the same as those described above. Experiments were performed on samples with different width dimensions D of the protrusions, and experimental results as shown in FIG. 12 were obtained.

  As shown in FIG. 12, it was confirmed by experiments that the durability (heat dissipation characteristics) was improved by the protrusions when the protrusion width D was in the range of 0.3 mm to 5 mm.

It is a perspective view showing the state where a part of the pneumatic tire concerning an embodiment of the invention was fractured. It is a tread width direction sectional view of a pneumatic tire concerning an embodiment of the invention. It is a perspective view of a protrusion. It is a perspective view which shows the state from which the airflow which hit | hung the protrusion became a turbulent flow. FIG. 4A is a view taken in the direction of arrow A in FIG. 3 and shows a flow of an upper air flow. FIG. 4B is a view of a protrusion as viewed from above, and shows a flow of a side air flow. FIG. 4 is a view taken in the direction of arrow B in FIG. (A) is sectional drawing of the pneumatic tire in which protrusion was provided in the bottom face of the groove | channel of a tread part, (b) is sectional drawing of the pneumatic tire in which protrusion was provided in the side surface of the groove | channel of a tread part. It is sectional drawing of the pneumatic tire in which protrusion was provided in the tire inner surface. It is a figure which shows the relationship between the height of the processus | protrusion obtained by experiment, and durability. It is a figure which shows the relationship between the front wall surface of a processus | protrusion obtained by experiment, and durability. It is a figure which shows the relationship between the side wall surface of the processus | protrusion obtained by experiment, and durability. It is a figure which shows the relationship between the width | variety of protrusion obtained by experiment, and durability.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 15 Tire surface 17, 17A Protrusion 17a Front wall surface 17b Upper wall surface 17c Side wall surface a Air flow a1 Upper air flow a2 Side air flow D Width of protrusion H Height of protrusion θ1 Angle of front wall of protrusion θ2, θ3 Angle of side wall of protrusion

Claims (2)

A pneumatic tire having a large number of protrusions on the tire surface,
Each of the protrusions has a height in the range of 0.3 to 5 mm, and an angle formed by the front wall surface on the side where the airflow strikes the tire surface is in the range of 70 to 110 degrees.
A groove is formed in the tread part in contact with the road surface,
Each said protrusion is provided in the bottom face of the said groove | channel, The pneumatic tire characterized by the above-mentioned.   2. The pneumatic tire according to claim 1, wherein the groove is a groove provided at a position closest to an end portion of the belt layer among the grooves extending along the tire circumferential direction.

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