JP2016196218A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of restraining occurrence of a hydro-planing phenomenon by securing drainage performance even after wear, and maintaining excellent uneven wear resistant performance.SOLUTION: A tread part 1 is provided with a widening main groove 10 formed of an inside wall surface 11, an outside wall surface 12 and a bottom surface 13. The inside wall surface 11 and the outside wall surface 12 are constituted of an inside wall surface upper part 11a and an outside wall surface upper part 12a inclined toward the inside in the width direction of the widening main groove 10, and an inside wall surface lower part 11b and an outside wall surface lower part 12b inclined in the inverse direction, respectively. Distances h1 and h2 from respective tread surfaces of connection points 11p and 12p for connecting an upper part and a lower part of the respective wall surfaces 11 and 12, satisfy the relationship of h1>h2. Groove widths of the widening main groove 10 at wear of 50%, 80% and 100% are expanded more than virtual groove widths in corresponding positions of virtual grooves constituted of extension lines of the inside wall surface upper part 11a and the outside wall surface upper part 12a, respectively.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire having a main groove extending in the circumferential direction. More specifically, the present invention secures drainage performance even after wear, suppresses the occurrence of hydroplaning phenomenon, and maintains excellent uneven wear resistance performance. The present invention relates to a pneumatic tire.

  Conventionally, in a pneumatic tire, a main groove extending in the tire circumferential direction is formed on a tread surface in order to ensure drainage performance in rainy weather or the like and suppress the occurrence of a hydroplaning phenomenon. However, since the conventional general main groove has a shape in which the groove width decreases toward the groove bottom side, when the tread surface wears, the groove area on the ground contact surface decreases, and the drainage performance decreases as compared with a new product. There is a problem that the occurrence of the hydroplaning phenomenon cannot be sufficiently suppressed.

  Therefore, in recent years, the groove width of the main groove is gradually increased from the tread surface side toward the groove bottom side (see, for example, Patent Document 1), and the upper portion and the groove width of the main groove are gradually reduced. It has been proposed to secure a groove area on the ground contact surface even after wear by comprising a lower portion that gradually increases (see, for example, Patent Document 2).

  However, when the main groove having such a shape is provided, it seems that the land portion adjacent to both sides of the main groove is greatly swollen toward the groove bottom side of the main groove because the main groove is widened on the groove bottom side. Since the cross-sectional shape is not sufficient, the rigidity of these land portions cannot be sufficiently secured, and there is a problem that uneven wear is likely to occur (uneven wear resistance performance is reduced).

JP 2001-121924 A JP-A-9-164814

  An object of the present invention is to provide a pneumatic tire that secures drainage performance even after wear and suppresses the occurrence of a hydroplaning phenomenon, and can maintain excellent uneven wear resistance.

  In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire provided with a tread portion that extends in the tire circumferential direction and has an annular shape. An inner wall surface on the tread surface side in which a widened main groove composed of an inner wall surface on the inner side in the direction, an outer wall surface on the outer side in the tire width direction and a bottom surface is formed, and the inner wall surface is inclined toward the inner side in the width direction of the widened main groove. An upper surface and an inner wall lower portion on the bottom surface side inclined in a direction opposite to the upper side of the inner wall surface, and the outer wall surface on the tread surface side and the outer surface in which the outer wall surface is inclined inward in the width direction of the widened main groove. A distance h1 from the tread surface at the connection point between the inner wall surface upper portion and the inner wall surface lower portion, the outer wall surface upper portion and the outer surface. The distance h2 from the tread surface at the connection point with the lower surface satisfies the relationship of h1> h2, and the groove width at 50% wear, groove width at 80% wear, and groove at 100% wear of the widened main groove The width is larger than the virtual groove width at the corresponding position of the virtual groove formed by the extension line of the upper part of the inner wall surface and the extension line of the upper part of the outer wall surface, respectively.

  In the present invention, the inner wall lower portion and the outer wall lower portion of the widened main groove are inclined toward the outer side in the width direction of the widened main groove, so that the groove width at the time of 50% wear and the groove at the time of 80% wear of the widened main groove. Since the width and the groove width at 100% wear are larger than the virtual groove width at the corresponding position of the virtual groove formed by the extension line of the upper part of the inner wall surface and the extension line of the upper part of the outer wall surface, respectively. Even so, the groove area is secured, the drainage performance can be sufficiently maintained, and the occurrence of the hydroplaning phenomenon can be suppressed. At this time, the distance h1 from the tread surface of the connection point between the inner wall surface upper portion and the inner wall surface lower portion and the distance h2 from the tread surface of the connection point between the outer wall surface upper portion and the outer wall surface lower portion satisfy the relationship of h1> h2. Since the position in the depth direction of the widened main groove at the point where the inclination is reversed is shifted, the amount of depression on the land side from the extension line of the inner wall surface upper part (that is, the inner wall surface of the virtual groove) It becomes smaller than the amount of depression on the land portion side than the upper extension line (that is, the outer wall surface of the virtual groove), and the rigidity of the land portion adjacent to the inner wall surface side of the widened main groove is maintained at a high level. As a result, the rigidity of the land portion on the tire equator side that tends to cause uneven wear is maintained, and the uneven wear resistance can be sufficiently maintained.

  In the present invention, the distance h1 is 0.5 to 0.8 times the groove depth h0 of the widened main groove, and the distance h2 is 0.1 to 0.4 times the groove depth h0 of the widened main groove. Preferably there is. By setting to such a range, the rigidity balance of the land part adjacent to both sides of the widened main groove can be improved, and uneven wear can be effectively suppressed.

  In the present invention, the distance L1 from the tire equator to the center in the width direction of the widened main groove is set to 50% to 80% of the distance L0 from the tire equator to the ground contact edge, while the tire is between the tire equator and the widened main groove. A main groove extending in the circumferential direction is formed, and the width L2 of the land portion defined by the main groove and the widened main groove is preferably 20% to 40% of the distance L0 from the tire equator to the ground contact end. . As a result, the groove on the outer side in the tire width direction in the case of having two grooves extending in the tire circumferential direction on one side of the tire equator becomes the widened main groove, and the arrangement of the widened main groove and the land portion adjacent to the widened main groove Therefore, the rigidity balance between the land portions adjacent to both sides of the widened main groove can be improved, and uneven wear resistance can be effectively maintained.

  In the present invention, the inclination angle β1 at the lower inner wall surface is smaller than the inclination angle α1 at the upper inner wall surface, the inclination angle β2 at the lower outer wall surface is smaller than the inclination angle α2 at the upper outer wall surface, and the inclination angle β1 at the lower inner wall surface is It is preferably 30 ° or less, and the inclination angle β2 of the lower portion of the outer wall surface is preferably 30 ° or less. By setting the inclination angle of each part of the wall surface of the widened main groove in this way, the shape of the widened main groove becomes favorable, which is advantageous for maintaining uneven wear resistance while obtaining drainage performance. Moreover, since the expansion of the groove width on the bottom surface side is limited with respect to the portion where the groove width of the widened main groove is minimized, the workability at the time of tire molding is improved.

  In the present invention, it is preferable that the inner wall surface and the outer wall surface are connected in an arc shape in the bottom surface and the meridian cross section, respectively, and the radius of curvature of each arc is 0.3 mm or more and 3 mm or less. By adopting such a shape, a sufficient groove volume in the vicinity of the bottom surface of the widened main groove can be secured, which is advantageous for maintaining drainage performance after wear.

  In the present invention, the ground contact end is an end portion in the tire axial direction when a normal load is applied by placing the tire on a normal rim and filling the normal internal pressure in a vertical state on a plane. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESURE” for ETRTO, but 180 kPa when the tire is a passenger car. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFORATION PRESSURES” is “LOAD CAPACITY” if it is ETRTO, but if the tire is a passenger car, the load is equivalent to 88% of the load.

It is a meridian half section view of the pneumatic tire which consists of an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a widened main groove of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a widened main groove of a pneumatic tire according to an embodiment of the present invention. It is explanatory drawing which expands and shows the tread part of the pneumatic tire which consists of embodiment of this invention.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  In FIG. 1, the symbol CL represents the tire equator. The pneumatic tire of the present invention includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, a pair of sidewall portions 2 that are disposed on both sides of the tread portion 1, and the tire radial direction of the sidewall portions 2 It is comprised from a pair of bead part 3 arrange | positioned inside. A carcass layer 4 is mounted between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back around the bead core 5 disposed in each bead portion 3 from the vehicle inner side to the outer side. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4. On the other hand, a plurality of layers (two layers in FIG. 1) of belt layers 7 and 8 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each of the belt layers 7 and 8 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and is disposed so that the reinforcing cords cross each other between the layers. In these belt layers 7 and 8, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set, for example, in a range of 10 ° to 40 °. Further, a belt reinforcing layer 9 is provided on the outer peripheral side of the belt layers 7 and 8. The belt reinforcing layer 9 includes an organic fiber cord oriented in the tire circumferential direction. In the belt reinforcing layer 9, the organic fiber cord has an angle with respect to the tire circumferential direction set to, for example, 0 ° to 5 °.

  The present invention is applied to such a general pneumatic tire, but its cross-sectional structure is not limited to the basic structure described above.

  In the pneumatic tire of the present invention, as shown in FIG. 1, a widened main groove 10 extending in the tire circumferential direction is provided in the tread portion 1. As shown in an enlarged view in FIG. 2, the widened main groove 10 includes an inner wall surface 11 on the inner side in the tire width direction, an outer wall surface 12 on the outer side in the tire width direction, and a bottom surface 13. When viewed from the tread surface side toward the groove bottom side, the inner wall surface 11 is inclined toward the inner side in the width direction of the widened main groove 10 from the tread surface to the middle in the depth direction of the widened main groove 10. The inclination is reversed at the middle of the depth direction 10, and from the middle of the depth direction of the widened main groove 10 to the bottom of the groove, the width is inclined outward in the width direction of the widened main groove 10. That is, the inner wall surface 11 is inclined in the opposite direction to the inner wall surface upper portion 11a on the tread surface side and the inner wall surface upper portion 11a inclined toward the inner side in the width direction of the widened main groove 10 (that is, the width direction of the widened main groove 10). It is composed of an inner wall surface lower portion 11b on the bottom surface 13 side (inclined toward the outside). Similarly, when viewed from the tread surface side toward the groove bottom side, the outer wall surface 12 is also inclined toward the inner side in the width direction of the widened main groove 10 from the tread surface to the middle in the depth direction of the widened main groove 10. The inclination is reversed in the middle of the widened main groove 10 in the depth direction, and from the middle of the widened main groove 10 in the depth direction to the bottom of the groove is inclined outward in the width direction of the widened main groove 10. That is, the outer wall surface 11 is inclined in the opposite direction to the outer wall surface upper portion 12a and the outer wall surface upper portion 12a on the tread surface side inclined toward the inner side in the width direction of the widened main groove 10 (that is, the outer side in the width direction of the widened main groove 10). The outer wall surface lower portion 12b on the bottom surface 13 side (inclined toward the bottom surface).

  At this time, the position in the depth direction of the widened main groove 10 at the point where the inclination is reversed on the inner wall surface 11 and the point where the inclination is reversed on the outer wall surface 12 are different. Specifically, the point where the inner wall surface upper portion 11a and the inner wall surface lower portion 11b are connected is the inner connection point 11p, and the point where the outer wall surface upper portion 12a and the outer wall surface lower portion 12b are connected is the outer connection point 12p. The point 11p is arranged at a deeper position in the depth direction of the widened main groove 10 than the outer connection point 12p. In other words, the distance h1 from the tread surface of the inner connection point 11p is larger than the distance h2 from the tread surface of the outer connection point 12p. When the inner wall surface upper portion 11a and the inner wall surface lower portion 11b are smoothly connected, the intersection of the extension lines of the respective portions is set as the inner connection point 11p, and the outer wall surface upper portion 12a and the outer wall surface lower portion 12b are smoothly connected. If there is, the intersection of the extension lines of each part is taken as the outer connection point 12p.

  As described above, the inner wall surface 11 includes the inner wall surface upper portion 11a and the inner wall surface lower portion 11b, and the outer wall surface 12 includes the outer wall surface upper portion 12a and the outer wall surface lower portion 12b. As compared with a conventional groove whose groove width gradually decreases toward the bottom (that is, a groove in which the inner wall surface upper portion 11a and the outer wall surface upper portion 12a extend to the bottom surface 13, respectively), the bottom surface 13 side is widened. At this time, in the widened main groove 10 of the present invention, the groove width at the position of 50% of the effective groove depth H of the widened main groove 10 from the tread surface (hereinafter referred to as “50% worn groove width”), The groove width at the position of 80% of the effective groove depth H of the widened main groove 10 from the tread surface (hereinafter referred to as “groove width at 80% wear”), and the effective groove depth of the widened main groove 10 from the tread surface The groove width at the position of 100% of H (hereinafter referred to as “groove width at 100% wear”) is an imaginary groove formed by an extension line of the inner wall surface upper part 11a and an extension line of the outer wall surface upper part 12a, respectively. It is made larger than the groove width at the corresponding position. The effective groove depth H is the distance in the depth direction of the widened main groove 10 from the surface of the tread portion 1 to the upper end surface of a wear indicator (not shown) formed on the bottom surface 13 of the widened main groove 10. . In other words, it is the depth obtained by subtracting the height of the wear indicator (usually 1.7 mm) from the groove depth h0 of the widened main groove 10 described later.

  Thus, in the present invention, by providing the widened main groove 10 having the above-described structure, the groove area is ensured even after wear as compared with the conventional groove in which the groove width gradually decreases toward the groove bottom. The drainage performance can be sufficiently maintained. As a result, the occurrence of the hydroplaning phenomenon can be effectively suppressed. Further, the position in the depth direction of the widened main groove at the point where the distance h1 from the tread surface of the inner connecting point 11p and the distance h2 from the tread surface of the outer connecting point 12p satisfy the relationship of h1> h2, and the inclination is reversed. In general, uneven wear tends to occur as the difference in rigidity between adjacent land portions increases. In particular, when the rigidity on the tire equator side is large, the tendency is strong. The amount of depression on the land portion side from the inner wall surface of the virtual groove) is smaller than the amount of depression on the land portion side than the extension line of the outer wall surface upper portion 12a (that is, the outer wall surface of the virtual groove), The rigidity of the land portion adjacent to the inner wall surface 11 side (the tire equator CL side) of the widened main groove 10 is maintained at a high level, and the uneven wear resistance can be sufficiently maintained.

  At this time, any of the groove width at the time of 50% wear, the groove width at the time of 80% wear, and the groove width at the time of 100% wear of the widened main groove 10 depending on the arrangement of the inner connection point 11p and the outer connection point 12p is a virtual groove. If the groove width is not larger than the corresponding groove width, the groove area after wear cannot be obtained sufficiently, and it becomes difficult to maintain the drainage performance after wear.

  Even if the inner connecting point 11p and the outer connecting point 12p have different positions in the depth direction of the widened main groove 10, if the distance h1 is smaller than the distance h2, the tire equator CL side is likely to cause uneven wear as described above. It becomes difficult to sufficiently maintain the rigidity of the land portion, and it is difficult to sufficiently maintain the uneven wear resistance.

  Preferably, the distance h1 is 0.5 to 0.8 times the groove depth h0 of the widened main groove 10, and the distance h2 is 0.1 to 0.4 times the groove depth h0 of the widened main groove 10. There should be. By setting to such a range, the rigidity balance of the land part adjacent to the both sides of the widening main groove 10 can be made favorable, and uneven wear-proof performance can be maintained effectively. If the distance h1 is smaller than 0.5 times the groove depth h0, the land portion adjacent to the inner side in the tire width direction of the widened main groove 10 is greatly struck, and it is difficult to ensure the rigidity of the land portion. Become. If the distance h1 is larger than 0.8 times the groove depth h0, the inner connection point 11p is disposed in the vicinity of the bottom surface 13, so that it is difficult to ensure a sufficient groove width after wear. If the distance h2 is smaller than 0.1 times the groove depth h0, the land portion adjacent to the outer side in the tire width direction of the widened main groove 10 has a large shape, and it is difficult to ensure the rigidity of the land portion. Become. If the distance h2 is larger than 0.4 times the groove depth h0, the outer connecting point 12p is disposed on the bottom surface 13 side, so that it is difficult to ensure a sufficient groove width after wear.

  As described above, each part of the wall surface of the widened main groove 10 is inclined. However, as shown in FIG. 3, the inclination angle of the inner wall surface upper portion 11a is α1, the inclination angle of the inner wall surface lower portion 11b is β1, and the outer wall surface upper portion. When the inclination angle of 12a is α2 and the inclination angle of the outer wall surface lower portion 12b is β2, it is preferable that the inclination angle β1 is smaller than the inclination angle α1 and the inclination angle β2 is smaller than the inclination angle α2. Further, it is preferable that the inclination angle β1 is 30 ° or less and the inclination angle β2 is 30 ° or less. Each inclination angle is an inclination angle with respect to the normal line of the surface of the tread portion 1. By setting the inclination angle of each part in this manner, the shape of the widened main groove 10 becomes favorable, which is advantageous for maintaining the uneven wear resistance by improving the rigidity balance while obtaining the drainage performance. Further, since the expansion of the groove width on the bottom surface 13 side is limited with respect to the portion where the groove width of the widened main groove 10 is minimized, the workability at the time of molding the tire is improved.

  At this time, if the inclination angles β1 and β2 exceed 30 °, the groove bottom side of the land portion adjacent to both sides of the widened main groove 10 has a large cross-sectional shape, and the rigidity of the land portion is sufficiently ensured. Can not be. The inclination angle of each part only needs to satisfy the above relationship, but more preferably, the inclination angle α1 is 10 ° to 30 °, the inclination angle β1 is 5 ° to 25 °, the inclination angle α2 is 5 ° to 25 °, The inclination angle β2 is preferably 0 ° to 20 °.

  As illustrated in FIGS. 1 to 3, in the meridian section, the inner wall surface 11 (inner wall surface lower portion 11 b) and the bottom surface 13, and the outer wall surface 12 (outer wall surface lower portion 12 b) and the bottom surface 13 are smoothly connected, The connecting portion is arcuate. At this time, as shown in FIG. 3, the radius of curvature of the arc of the connection portion between the inner wall surface 11 (inner wall surface lower portion 11 b) and the bottom surface 13 is R1, and the connection portion between the outer wall surface 12 (outer wall surface lower portion 12 b) and the bottom surface 13. When the radius of curvature of the arc is R2, it is preferable that the radius of curvature R1 and R2 is not less than 0.3 mm and not more than 3 mm. By setting it as such a cross-sectional shape, it becomes possible to ensure enough groove volume near the bottom face 13 of the widened main groove 10, and it becomes advantageous in maintaining the drainage performance after wear. At this time, if the curvature radii R1 and R2 are smaller than 0.3 mm, the arc of the connecting portion is too small to be the same as the case where the connecting portions have corner portions. When the curvature radii R1 and R2 are larger than 3 mm, the groove volume at the groove bottom portion becomes small, and it becomes difficult to ensure sufficient drainage performance after wear.

  In the embodiment of FIG. 1, in addition to the widened main groove 10, a main groove 20 extending in the tire circumferential direction is formed in the tread portion 1. The main groove 20 is disposed closer to the tire equator CL than the widened main groove 10. In other words, two grooves extending in the circumferential direction are formed on one side of the tire equator CL, and a groove on the outer side in the tire width direction is the widened main groove 10. At this time, as shown in FIG. 4, the distance L1 from the tire equator CL to the center in the width direction of the widened main groove 10 is set to 50% to 80% of the distance L0 from the tire equator CL to the ground contact E. It is preferable that the width L2 of the land portion defined by the main groove 10 and the main groove 20 is 20% to 40% of the distance L0 from the tire equator CL to the ground contact end E. By setting it as such an aspect, the rigidity balance of the land part adjacent to the both sides of the widening main groove 10 can be made favorable, and uneven wear-proof performance can be maintained effectively.

  At this time, when the distance L1 is smaller than 50% of the distance L0, the width L2 of the land portion adjacent to the inner side in the tire width direction of the widened main groove 10 cannot be sufficiently secured, and the rigidity of the land portion is sufficiently maintained. It becomes difficult. If the distance L1 is greater than 80% of the distance L0, the widened main groove 10 is too close to the ground contact E, and the length that the widened main groove 10 contacts the road surface at the time of grounding is not sufficiently secured. The effect of 10 (maintaining drainage performance after wear) is not fully exhibited. If the width L2 is smaller than 20% of the distance L0, the width L2 is too small and it becomes difficult to sufficiently maintain the land portion rigidity. When the width L2 is larger than 40% of the distance L0, the drainage of this portion cannot be sufficiently performed, and it becomes difficult to suppress the occurrence of the hydroplaning phenomenon.

  The tire size is 215 / 60R16, has the cross-sectional shape illustrated in FIG. 1, the ratio h1 / h0 between the distance h1 from the tread surface of the inner connection point and the groove depth h0 of the widened main groove, Ratio h2 / h0 between the distance h2 from the tread surface and the groove depth h0 of the widened main groove, and the ratio L1 between the distance L1 from the tire equator to the center in the width direction of the widened main groove and the distance L0 from the tire equator to the ground contact edge / L0, the ratio L2 / L0 between the width L2 of the land section defined by the widened main groove and the main groove and the distance L0 from the tire equator to the ground contact edge, the inclination angle α1 with respect to the normal of the tread surface on the inner wall surface, Inclination angle β1 with respect to the normal line of the tread surface at the lower inner wall surface, Inclination angle α2 with respect to the normal line of the tread surface at the upper outer wall surface, Inclination angle β2 with respect to the normal line of the tread surface at the lower outer wall surface, of 17 types of pneumatic tires of Conventional Example 1, Comparative Examples 1 to 3, and Examples 1 to 13 in which the radius of curvature R1 and the radius of curvature R2 of the connecting portion between the outer wall surface and the bottom surface are set as shown in Tables 1 and 2, respectively. Produced.

  In all examples, the groove depth of the widened main groove was 10 mm and was common. The main groove has a groove depth of 10 mm, an inclination angle with respect to the normal line of the tread surface of the groove wall on the inner side in the tire width direction, and an inclination angle with respect to the normal line of the tread surface of the groove wall on the outer side in the tire width direction. The groove has a radius of curvature of 2 mm at a connecting portion between the groove wall and the groove bottom at 10 °.

  Conventional Example 1 is a groove in which the groove width gradually decreases from the tread surface toward the groove bottom. In Table 1, the groove is composed of only the inner wall surface upper portion and the outer wall surface upper portion where the groove wall is inclined toward the inner side in the width direction of the widened main groove, that is, the inner connection point and the outer connection point exist on the bottom surface (h1 = h2 = h0). Comparative Example 1 is a groove whose groove width gradually increases from the tread surface toward the groove bottom. In Table 1, a groove composed of only a lower inner wall surface and an outer lower wall surface whose groove wall is inclined outward in the width direction of the widened main groove, that is, an inner connection point and an outer connection point exist on the tread surface (h1). = H2 = 0).

  For these 17 types of pneumatic tires, drainage performance (when new, 30% worn, 50% worn) and uneven wear resistance were evaluated by the following evaluation methods. The results are also shown in Table 1. .

Drainage performance (new, 30% worn, 50% worn)
Each test tire was assembled to a wheel with a rim size of 16 × 61 / 2JJ, and the air pressure was set to 200 kPa, and it was mounted on a front-wheel drive passenger car with a displacement of 1.6 L so as to enter a pool with a water depth of 10 mm on a straight road. A running test was conducted to gradually increase the approach speed to the pool and measure the critical speed at which the hydroplaning phenomenon occurred. The drainage performance at 30% wear and 50% wear was measured by performing the above test after each test tire was worn from the tread surface to a position of 30% or 50% of the effective groove depth. The evaluation results are shown as an index with Conventional Example 1 as 100. A larger index value means better drainage performance.

Uneven wear resistance performance Each test tire is mounted on a wheel with a rim size of 16x61 / 2JJ, mounted on a front-wheel drive passenger car with an air pressure of 200 kPa and a displacement of 1.6 L, and a test course at an average speed of 80 km / h. The amount of wear step after running 50000 km was measured. The evaluation result was shown by the index | exponent which sets the prior art example 1 to 100 using the reciprocal number of the measured value. The larger the score, the smaller the wear step and the better the uneven wear resistance.

  As is apparent from Table 1, Examples 1 to 13 all improved drainage performance after wear (30% wear and 50% wear) while maintaining uneven wear resistance against Conventional Example 1. . On the other hand, Comparative Examples 1 and 2 were able to improve drainage performance after wear, but uneven wear resistance performance was worse than that of Conventional Example 1.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7, 8 Belt layer 9 Belt reinforcement layer 10 Widening main groove 11 Inner wall surface 11a Inner wall surface upper part 11b Inner wall surface lower part 11p Inner connection point 12 Outer wall surface 12a Outer wall upper part 12b Outer wall lower part 12p Outer connection point 13 Bottom face 20 Main groove CL Tire equator E Grounding end

Claims (5)

In a pneumatic tire having a tread portion that extends in the tire circumferential direction and has an annular shape,
A widened main groove is formed in the tread portion in the tire circumferential direction, and is formed of an inner wall surface on the inner side in the tire width direction, an outer wall surface on the outer side in the tire width direction, and a bottom surface, and the inner wall surface of the widened main groove is An inner wall upper portion on the tread surface side inclined toward the inner side in the width direction and an inner wall lower portion on the bottom surface side inclined in the opposite direction to the inner wall upper portion, and the outer wall surface on the inner side in the width direction of the widened main groove. An upper portion of the outer wall surface on the tread surface side inclined toward the upper surface and a lower portion of the outer wall surface on the bottom surface side inclined in the opposite direction to the upper portion of the outer wall surface. H1 and the distance h2 from the tread surface of the connection point between the upper portion of the outer wall surface and the lower portion of the outer wall surface satisfy the relationship of h1> h2, and the groove width at the time of 50% wear of the widened main groove and 80% wear. of time The width and the groove width at 100% wear are larger than the virtual groove width at the corresponding position of the virtual groove formed by the extension line of the upper part of the inner wall surface and the extension line of the upper part of the outer wall surface, respectively. Pneumatic tires.   The distance h1 is 0.5 to 0.8 times the groove depth h0 of the widened main groove, and the distance h2 is 0.1 to 0.4 times the groove depth h0 of the widened main groove. The pneumatic tire according to claim 1, wherein there is a pneumatic tire.   While the distance L1 from the tire equator to the center in the width direction of the widened main groove is set to 50% to 80% of the distance L0 from the tire equator to the ground contact end, the tire circumferential direction is between the tire equator and the widened main groove. A land groove defined by the main groove and the widened main groove has a width L2 of 20% to 40% of a distance L0 from the tire equator to the ground contact edge. The pneumatic tire according to claim 1 or 2.   The inclination angle β1 of the lower inner wall surface is smaller than the inclination angle α1 of the upper inner wall surface, the inclination angle β2 of the lower outer wall surface is smaller than the inclination angle α2 of the upper outer wall surface, and the inclination angle β1 of the lower inner wall surface. The pneumatic tire according to any one of claims 1 to 3, wherein an inclination angle β2 of the lower portion of the outer wall surface is 30 ° or less.   The inner wall surface and the outer wall surface are connected in an arc shape in the bottom surface and the meridian cross section, respectively, and the curvature radius of each arc is 0.3 mm or more and 3 mm or less. Pneumatic tires.

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