JP2014131898A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which allows improvement of dry performance, noise resistance performance and uneven wear resistance performance while suppressing deterioration of wet performance.SOLUTION: In a pneumatic tire 1, a shoulder main groove 3 is provided in a tread part 2, and the shoulder land part 6 is segmented. In the shoulder land part 6, a plurality of shoulder lateral grooves 10 extending from the tread ground contact end E toward the shoulder main groove 3 and inclined to one side are provided, and the shoulder lateral grooves 10 include a groove wall surface 12A on one side, a groove wall surface 12B on the other side and a groove bottom part 16. The groove wall surface 12A on one side includes a step-wise part 17 consisting of an outside wall surface part 17A extending from a lateral edge 11A, a level difference surface part 17B extending from the outside wall surface part 17A in the groove width direction and an inside wall surface part 17C from the level difference part 17B to the groove bottom part 16, and the step-wise part 17 is provided at least at a position including the tread ground contact end E.

Description

  The present invention relates to a pneumatic tire capable of improving dry performance, noise resistance performance, and uneven wear resistance performance while suppressing a decrease in wet performance.

  Patent Document 1 below proposes a pneumatic tire in which a tread portion is provided with a main groove extending continuously in the tire circumferential direction. The tread portion is provided with a shoulder main groove on the outermost side in the tire axial direction, and the shoulder land portion is divided between the shoulder main groove and the tread grounding end. Further, the shoulder land portion is provided with a plurality of shoulder lateral grooves extending from the tread grounding end toward the shoulder main groove and inclined toward one side in the tire circumferential direction.

JP 2005-170147 A

  In the pneumatic tire as described above, on the tread ground end side of the shoulder land portion, for example, an angle formed by the groove edge on one side of the shoulder lateral groove and the tread ground end is formed at an acute angle. On the other hand, the angle formed by the groove edge on the other side of the shoulder lateral groove and the tread grounding end is formed as an obtuse angle. Accordingly, the rigidity of the groove edge on one side is smaller than the rigidity of the groove edge on the other side. For this reason, a rigidity difference arises in each groove edge adjacent across the shoulder lateral groove. Due to such a difference in rigidity, the pneumatic tire has a problem that uneven wear tends to occur at the groove edge on one side having relatively small rigidity. Further, such a difference in rigidity may reduce dry performance (for example, steering stability on a dry road surface).

  The present invention has been made in view of the above problems, and has as its main object to provide a pneumatic tire capable of improving dry performance, noise resistance performance and uneven wear resistance performance while suppressing a decrease in wet performance.

  Of the present invention, the invention according to claim 1 is characterized in that the shoulder main groove and the tread are provided in the tread portion by providing a shoulder main groove extending continuously in the tire circumferential direction on at least one tread grounding end side. A pneumatic tire in which a shoulder land portion is partitioned from a ground contact end, and the at least one shoulder land portion extends from the tread ground contact end toward the shoulder main groove and extends in a tire circumferential direction. A plurality of shoulder lateral grooves inclined to one side are provided, and each shoulder lateral groove has a cross section perpendicular to the center line between the groove edges, and the other side facing the groove wall surface on the one side and the groove wall surface on the one side. The groove wall surface on one side includes an outer wall surface portion extending inward in the tire radial direction from the groove edge on the one side, and the outer surface. A step surface portion extending in the groove width direction from the inner end in the tire radial direction of the surface portion toward the center of the shoulder lateral groove, and an inner wall surface portion extending inward in the tire radial direction from the end of the step surface portion and reaching the groove bottom portion. A stepped portion is included, and the stepped portion is provided at a position including at least the tread grounding end.

  In the second aspect of the present invention, in the cross section, the shoulder lateral groove has a ratio (W1 / W2) between a width W1 of the stepped surface portion in the groove width direction and a groove width W2 between the shoulder edges of the shoulder lateral groove. Is a pneumatic tire according to claim 1.

  According to a third aspect of the present invention, in the cross section, the shoulder lateral groove is a ratio of a height h in the tire radial direction from the groove bottom to the stepped surface portion and a maximum depth H of the shoulder lateral groove ( 3. The pneumatic tire according to claim 1, wherein h / H) is 0.3 to 0.9.

  According to a fourth aspect of the present invention, in the transverse section, the groove wall on the other side of the shoulder lateral groove extends smoothly with an inclination that reduces the groove width from the groove edge toward the groove bottom. The pneumatic tire according to any one of claims 1 to 3, further comprising an arc portion that smoothly connects the main portion and the groove bottom portion.

  According to a fifth aspect of the present invention, in the cross section, the main portion of the groove wall surface on the other side and the outer wall surface portion of the groove wall surface on the one side are grooves toward the groove bottom portion, respectively. 5. The pneumatic tire according to claim 4, wherein the pneumatic tire is inclined in a direction to reduce a width, and an inclination angle of the main portion is larger than an inclination angle of the outer wall surface portion.

  In the invention according to claim 6, the tread portion is designated in the direction of mounting on the vehicle, and the tread portion is positioned outside the tire equator when the vehicle is mounted. An inner tread portion positioned on the vehicle inner side than the tire equator, and the shoulder main groove and the shoulder lateral groove are provided in the outer tread portion and the inner tread portion, respectively, and provided in the outer tread portion. In each shoulder lateral groove, the stepped portion is formed in the entire range in the length direction of the shoulder lateral groove, and in each shoulder lateral groove provided in the inner tread portion, the stepped portion is the length of the shoulder lateral groove. The pneumatic tire according to any one of claims 1 to 5, wherein the pneumatic tire is formed in a range of 30 to 60% of a direction.

  In the invention according to claim 7, the shoulder lateral grooves provided in the outer tread part and the shoulder lateral grooves provided in the inner tread part are directed from the tread ground end toward the shoulder main groove. The pneumatic tire according to claim 6, wherein the tires are inclined in opposite directions in the tire circumferential direction.

  In the pneumatic tire of the present invention, a plurality of shoulder lateral grooves extending from the tread grounding end toward the shoulder main groove and inclined toward one side in the tire circumferential direction are provided in the shoulder land portion. The groove wall surface on the one side of the shoulder lateral groove includes a stepped portion including an outer wall surface portion, a step wall surface portion, and an inner wall surface portion, and the stepped portion is provided at a position including at least the tread end. .

  In the pneumatic tire of the present invention, the rigidity of the groove edge on one side having relatively small rigidity can be enhanced by the stepped portion on the tread grounding end side of the shoulder land portion. Therefore, since the pneumatic tire of the present invention can reduce the difference in rigidity between the groove edge on one side and the groove edge on the other side, it can suppress uneven wear that tends to occur on the groove edge on one side. Uneven wear resistance performance can be improved. Further, the pneumatic tire of the present invention can improve the rigidity on the tread ground end side of the shoulder land portion by the stepped portion, so that the driving stability on the dry road surface can be improved, and the dry performance can be improved. Can be improved.

  Furthermore, in the pneumatic tire according to the present invention, the volume of the shoulder lateral groove can be reduced by the stepped portion, so that the amount of air having the shoulder lateral groove as an air column tube can be reduced. Therefore, the pneumatic tire of the present invention can suppress generation of a large air column resonance sound and improve noise resistance. Moreover, in the pneumatic tire of the present invention, the stepped portion is formed only on the groove wall surface on one side of the groove wall surface on one side and the groove wall surface on the other side of the shoulder lateral groove. The amount of reduction in the groove volume of the lateral groove can be minimized. Therefore, the pneumatic tire of the present invention can maintain the drainage by the shoulder lateral groove, and can suppress a decrease in wet performance.

It is the expanded view by which the tread part of the pneumatic tire of embodiment of this invention was expand | deployed. It is meridian sectional drawing of a pneumatic tire. It is the top view to which the outer side tread part was expanded with the shoulder lateral groove. It is AA sectional drawing shown by FIG. It is the top view to which the inner side tread part was expanded with the shoulder lateral groove. FIG. 6 is a BB cross-sectional view shown in FIG. 5. FIG. 6 is a development view in which a tread portion of a pneumatic tire of Comparative Example 2 is developed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a development view of a tread portion 2 of a pneumatic tire (hereinafter, sometimes simply referred to as “tire”) 1 of the present embodiment.

  The tire 1 of the present embodiment is configured as a passenger car tire. When the tire 1 is mounted on the vehicle, for example, the direction of mounting on the vehicle is designated such that one tread ground end Ea side in the tire axial direction is the vehicle outer side and the other tread ground end Eb side in the tire axial direction is the vehicle inner side. Is done. Accordingly, the tread portion 2 of the present embodiment is divided into an outer tread portion 2A located on the vehicle outer side than the tire equator C and an inner tread portion 2B located on the vehicle inner side than the tire equator C.

  Here, the “tread grounding end” means that a normal load is applied to a tire in a normal internal pressure state in which a normal rim is assembled and a normal internal pressure is filled, and a flat surface is grounded at a camber angle of 0 °. The outermost end of the tread contact surface in the tire axial direction.

  The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, a “standard rim” for JATMA and a “Design” for TRA. "Rim" or "Measuring Rim" for ETRTO.

  The “regular internal pressure” is an air pressure defined by each standard for each tire in a standard system including a standard on which the tire is based. The maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa for passenger cars.

  The “regular load” is a load determined by each standard for each tire in a standard system including a standard on which the tire is based. For example, in the case of JATMA, “maximum load capacity” or TRA. For example, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” for ETRTO.

  In addition, the dimension of each part of the tire 1 such as the groove width is a value measured in a no-load normal internal pressure state unless otherwise specified. The groove width is a value measured at right angles to the center line between the groove edges in the tread portion.

  As shown in FIG. 1, the tread portion 2 includes a pair of shoulder main grooves extending continuously in the tire circumferential direction on at least one of the tire axial directions, in the present embodiment, both tread ground contact ends E in the tire axial direction. 3 and a crown main groove 4 extending continuously in the tire circumferential direction along the tire equator C is provided between the pair of shoulder main grooves 3. As a result, the tread portion 2 includes a pair of shoulder land portions 6 divided between the shoulder main groove 3 and the tread grounding end E, and a pair divided between the shoulder main groove 3 and the crown main groove 4. The crown land portion 7 is provided.

  FIG. 2 shows a meridian cross-sectional view of the tire 1. As shown in FIGS. 1 and 2, the shoulder main groove 3 includes, for example, an outer main groove 3 </ b> A provided on the one ground contact end Ea side of the tire equator C, and the other ground contact end Eb of the tire equator C. It is comprised from the inner side main groove 3B provided in the side.

  Since the outer main groove 3A is disposed on the one tread grounding end Ea side, the drainage of the outer tread portion 2A can be improved. As a result, since the tire 1 can improve the ground contact performance on the wet road surface, the wet performance can be improved.

  The outer main groove 3A desirably extends linearly continuously in the tire circumferential direction. Such a linear outer main groove 3A can enhance drainage as compared with, for example, a zigzag groove continuously extending in the tire circumferential direction.

  In order to effectively exhibit the above-described action, the distance A from the groove center of the outer main groove 3A of the present embodiment to the tire equator C is set to a range of 5 to 30% of the tread contact width TW. Is desirable. When the distance A is less than 5% of the tread ground contact width TW, the outer main groove 3A is excessively close to the tire equator C, so that the drainage performance on the one tread ground contact end Ea side may be deteriorated. Therefore, there is a possibility that the tire 1 cannot fully exhibit the wet performance. On the contrary, when the distance A exceeds 30% of the tread ground contact width TW, the outer main groove 3A excessively approaches one tread ground contact end Ea, which may reduce the rigidity on the one tread ground contact end Ea side. is there. Therefore, the tire 1 cannot sufficiently improve the feeling of rigidity at the time of turning, and there is a possibility that the steering stability on the dry road surface may be impaired. From these viewpoints, the distance A is preferably 10 to 27% of the tread ground contact width TW, and more preferably 15 to 25% of the tread ground contact width TW.

  Further, the groove width Wa of the outer main groove 3A is preferably 4 to 20% of the tread ground contact width TW. If the groove width Wa is less than 4% of the tread ground contact width TW, the drainage of the outer main groove 3A may be insufficient. On the other hand, when the groove width Wa exceeds 20% of the tread contact width TW, the pattern rigidity and rigidity balance of the outer main groove 3A are deteriorated, and the steering stability of the tire 1 tends to be impaired. From these viewpoints, the groove width Wa is preferably 6 to 15%, more preferably 8 to 12% of the tread ground contact width TW.

  As shown in FIG. 2, the groove depth Ha of the outer main groove 3A is preferably 6.0 to 9.0 mm, more preferably 6.5 to 6.0 mm, from the same viewpoint as the groove width Wa. It is desirable to be 8.5 mm.

  As shown in FIGS. 1 and 2, the inner main groove 3 </ b> B of the present embodiment extends linearly in the same manner as the outer main groove 3 </ b> A. Such an inner main groove 3B can enhance the drainage of the tire 1. As a result, since the tire 1 has improved ground contact performance on the wet road surface, the wet performance can be improved. The inner main groove 3B preferably has a distance B from the groove center to the tire equator C and a groove depth Hb in the same range as the distance A and the groove depth Ha of the outer main groove 3A.

  Furthermore, the inner main groove 3B is preferably smaller than the groove width Wa of the outer main groove 3A. The inner tread portion 2B provided with such an inner main groove 3B can increase the pattern rigidity as compared with the outer tread portion 2A, and can improve the grip performance when traveling straight. Note that if the groove width Wb of the inner main groove 3B is less than 2 mm, the drainage tends to be insufficient. From these viewpoints, the groove width Wb is preferably 3.0 to 10.0 mm.

  It is desirable that the crown main groove 4 of the present embodiment extends linearly like the outer main groove 3A and the inner main groove 3B. Such a crown main groove 4 can improve the drainage of the tire 1 when traveling straight.

  The crown main groove 4 desirably has a groove width Wc smaller than the groove width Wa of the outer main groove 3A. Such a crown main groove 4 can enhance pattern rigidity near the tire equator. On the other hand, if the groove width Wc of the crown main groove 4 is less than 2 mm, the drainage effect tends to be insufficient. As shown in FIG. 2, the groove depth Hc of the crown main groove 4 is preferably in the same range as the groove depth Ha of the outer main groove 3A and the groove depth Hb of the inner main groove 3B.

  As shown in FIG. 1, the shoulder land portion 6 of the present embodiment includes, for example, an outer shoulder land portion 6 </ b> A divided between the outer main groove 3 </ b> A and one tread grounding end Ea, and an inner main groove 3 </ b> B. It includes an inner shoulder land portion 6B that is partitioned between the other tread ground contact edge Eb. Furthermore, at least one shoulder land portion 6 is provided with a plurality of shoulder lateral grooves 10 extending from the tread grounding end E toward the shoulder main groove 3.

  The shoulder lateral grooves 10 include a plurality of outer shoulder lateral grooves 10A extending from one tread ground end Ea toward the outer main groove 3A, and a plurality of inner shoulder lateral grooves extending from the other tread ground end Eb toward the inner main groove 3B. 10B. The shoulder lateral grooves 10A and the shoulder lateral grooves 10B are inclined in directions opposite to each other in the tire circumferential direction.

  FIG. 3 shows a plan view in which the outer tread portion 2A is enlarged together with the outer shoulder lateral groove 10A. 4 is a cross-sectional view taken along the line AA shown in FIG. 3 and perpendicular to the center line Lc between the groove edges 11A and 11B of the outer shoulder lateral groove 10A. As shown in FIG. 3 or FIG. 4, the outer shoulder lateral groove 10A is formed, for example, from one tread ground end Ea to the outer main groove 3A from the other side Si (lower side in the figure) in the tire circumferential direction to the one side So. Inclined (upward in the figure). Further, the outer shoulder lateral groove 10A terminates without reaching the outer main groove 3A. Such an outer shoulder lateral groove 10A can enhance drainage while maintaining the rigidity of the outer shoulder land portion 6A. In order to effectively exhibit such an action, the groove width W2 of the outer shoulder lateral groove 10A is preferably 2.0 to 4.0 mm, and the maximum depth H of the outer shoulder lateral groove 10A is Preferably, it is 5.5 to 7.5 mm.

  The outer shoulder lateral groove 10A includes a groove edge 11A on one side So and a groove edge 11B on the other side Si. In the present embodiment, since the outer shoulder lateral groove 10A is inclined as described above, the angle formed by the groove edge 11A on one side So of the outer shoulder lateral groove 10A and the one tread grounding end Ea is formed at an acute angle. Is done.

  As shown in FIG. 4, the outer shoulder lateral groove 10A includes a groove wall surface 12A on one side So in the tire circumferential direction, a groove wall surface 12B on the other side Si facing the groove wall surface 12A, and a groove bottom portion 16 having a maximum depth H. Including.

  The groove wall surface 12A on one side So extends from the groove edge 11A on the one side So inward in the tire radial direction, and toward the center side of the outer shoulder lateral groove 10A from the tire radial inner edge of the outer wall surface portion 17A. The stepped portion 17 includes a step surface portion 17B extending in the groove width direction and an inner wall surface portion 17C extending from the end of the step surface portion 17B inward in the tire radial direction and reaching the groove bottom portion 16. Such a stepped portion 17 can increase the rigidity of the groove edge 11A on the one side So having relatively low rigidity, and the difference in rigidity between the groove edge 11A on the one side So and the groove edge 11B on the other side Si. Can be reduced. Therefore, the tire 1 can suppress uneven wear occurring at the groove edge 11A on the one side So of the outer shoulder land portion 6A, and can improve uneven wear resistance.

  As shown in FIG. 3, the stepped portion 17 is preferably provided at a position including at least one tread grounding end Ea. Such a stepped portion 17 can effectively increase the rigidity of the outer shoulder land portion 6A on the one tread ground contact end Ea side. Therefore, the tire 1 can further improve the handling stability and can further improve the dry performance.

  Furthermore, it is desirable that the stepped portion 17 is formed over the entire range in the length direction of the outer shoulder lateral groove 10A, for example. Thereby, the step-like portion 17 can further increase the pattern rigidity of the outer tread portion 2A, and can further improve the dry performance. Note that the stepped portion 17 may be extended, for example, to the outer side in the tire axial direction of one tread ground contact end Ea.

  Further, since the stepped portion 17 can reduce the groove volume of the outer shoulder lateral groove 10A, the amount of air having the outer shoulder lateral groove 10A as the air column tube can be reduced. Therefore, the tire 1 can suppress generation of a large air column resonance sound and can improve noise resistance. Moreover, in the tire 1 of the present embodiment, the outer shoulder lateral groove 10A includes the stepped portion 17 only on the groove wall surface 12A on the one side So, so that the groove volume of the outer shoulder lateral groove 10A by the stepped portion 17 is increased. The amount of decrease can be minimized. Therefore, the tire 1 can maintain the drainage by the outer shoulder lateral groove 10A, and can suppress a decrease in wet performance.

  As shown in FIG. 4, in the cross section, the outer shoulder lateral groove 10A has a ratio (W1 / W2) between the width W1 of the stepped surface portion 17B in the groove width direction and the groove width W2 between the groove edges of the outer shoulder lateral groove 10A. Is preferably 0.15 to 0.7. When the ratio of the width W1 to the groove width W2 (W1 / W2) is less than 0.15, the rigidity of the groove edge 11A cannot be sufficiently increased, and the uneven wear resistance performance is improved. difficult. On the contrary, when the ratio (W1 / W2) of the width W1 and the groove width W2 is larger than 0.7, the groove volume of the outer shoulder lateral groove 10A is reduced by the stepped portion 17, and the drainage of the outer shoulder lateral groove 10A is reduced. Is greatly reduced, and it is difficult to suppress a reduction in wet performance. From such a viewpoint, the ratio (W1 / W2) between the width W1 and the groove width W2 is more preferably 0.25 to 0.5.

  In the cross section, the outer shoulder lateral groove 10A has a ratio (h / H) between the height h in the tire radial direction from the groove bottom 16 to the stepped surface portion 17B and the maximum depth H of the outer shoulder lateral groove 10A. .3 to 0.9 is desirable. If the ratio of the height h to the maximum depth H (h / H) is less than 0.3, the rigidity of the groove edge 11A cannot be sufficiently increased, and the uneven wear resistance performance is improved. Is difficult. Conversely, when the ratio of the height h to the maximum depth H (h / H) is greater than 0.9, the stepped portion 17 reduces the groove volume of the outer shoulder lateral groove 10A, and the outer shoulder lateral groove 10A There is a risk that the drainage will be greatly reduced. From such a viewpoint, the ratio (h / H) between the height h and the maximum depth H is more preferably 0.5 to 0.75.

  The groove wall surface 12B of the other side Si of the outer shoulder lateral groove 10A has, for example, a main portion 18 extending from the groove edge 11B of the other side Si toward the groove bottom portion 16 in the cross section shown in FIG. An arc portion 19 that smoothly connects the bottom portion 16 is included. Such an arc portion 19 can suppress the occurrence of cracks that are likely to occur between the main portion 18 and the groove bottom portion 16.

  The main portion 18 of the groove wall surface 12 </ b> B of the other-side Si in the present embodiment extends smoothly in a direction of decreasing the groove width toward the groove bottom portion 16. The inclination angle α of the main portion 18 with respect to the tire radial direction is larger than the inclination angle β of the outer wall surface portion 17A with respect to the tire radial direction. As a result, the amount of deflection when the main portion 18 is on the late arrival side can be reduced, and the amount of sliding with the road surface can be reduced. Therefore, even when the main portion 18 is the rear arrival side, uneven wear can be reduced.

  FIG. 5 shows a plan view in which the inner tread portion 2B is enlarged together with the inner shoulder lateral groove 10B. FIG. 6 is a cross-sectional view taken along the line BB shown in FIG. 5 and perpendicular to the center line Lc between the groove edges 13A and 13B of the inner shoulder lateral groove 10B. As shown in FIG. 5 or FIG. 6, the inner shoulder lateral groove 10B of the present embodiment is one from the other side Si (upper side in the figure) in the tire circumferential direction from the other tread ground contact end Eb to the inner main groove 3B. Inclined to the side So (lower side in the figure). Further, the inner shoulder lateral groove 10B reaches the inner main groove 3B and terminates. Such an inner shoulder lateral groove 10B can enhance drainage while maintaining the rigidity of the inner shoulder land portion 6B. In order to effectively exhibit such an action, the groove width W2 of the inner shoulder lateral groove 10B is preferably 2.0 to 4.0 mm, and the maximum depth H of the inner shoulder lateral groove 10B is Preferably, it is 5.5 to 7.5 mm.

  The inner shoulder lateral groove 10B includes a groove edge 13A on one side So and a groove edge 13B on the other side Si. In the present embodiment, since the inner shoulder lateral groove 10B is inclined as described above, the angle formed by the groove edge 13A on one side So of the inner shoulder lateral groove 10B and the other tread grounding end Eb is formed at an acute angle. Is done.

  As shown in FIG. 6, the inner shoulder lateral groove 10B includes a groove wall surface 14A on one side So in the tire circumferential direction, a groove wall surface 14B on the other side Si facing the groove wall surface 14A, and a groove bottom portion having a maximum depth H. 16 is included.

  In the inner shoulder lateral groove 10B of the present embodiment, a stepped portion 17 is formed in the same manner as the outer shoulder lateral groove 10A. Such a stepped portion 17 can increase the rigidity of the groove edge 13A on the one side So having relatively low rigidity, and the rigidity of the groove edge 13A on the one side So and the groove edge 13B on the other side Si can be increased. The difference can be reduced. Therefore, the tire 1 can suppress uneven wear that occurs in the groove edge 13A on the one side So of the inner shoulder land portion 6B, and can improve uneven wear resistance.

  As shown in FIG. 5 or FIG. 6, the stepped portion 17 is desirably provided at a position including at least the other tread grounding end Eb. Such a stepped portion 17 can increase the rigidity of the other tread grounding end Eb side of the inner tread portion 2B, and can further improve the dry performance. Further, the stepped portion 17 of the present embodiment is formed in a range of 30 to 60% in the length direction of the inner shoulder lateral groove 10B from the other tread grounding end Eb of the inner shoulder lateral groove 10B. Thereby, the stair-like portion 17 can increase the rigidity only on the other tread grounding end Eb side of the inner tread portion 2B. When the stepped portion 17 is in a range smaller than 30% in the length direction of the inner shoulder lateral groove 10B, it is difficult to sufficiently increase the rigidity on the other tread grounding end Eb side of the inner tread portion 2B. Conversely, when the stepped portion 17 is in a range larger than 60% in the length direction of the inner shoulder lateral groove 10B, the obtuse angle rigidity formed by the inner main groove 3A and the groove edge 13A on one side So of the inner shoulder lateral groove 10B. May increase and cause uneven wear. From such a viewpoint, the stepped portion 17 is preferably formed in a range of 40 to 50% in the length direction of the inner shoulder lateral groove 10B. Note that the stepped portion 17 may be extended, for example, on the outer side in the tire axial direction of the other tread ground contact end Eb.

  In the inner shoulder lateral groove 10B of the present embodiment, for example, the wide wall portion 21 is provided on the other side Si on the groove wall surface 14B facing the stepped portion 17 of the groove wall surface 14A. Such a wide portion 21 can reduce the amount of reduction in the groove volume of the inner shoulder lateral groove 10B due to the stepped portion 17. Therefore, the tire 1 can maintain drainage and can further suppress a decrease in wet performance.

  Although the tire 1 of the present embodiment is exemplified in which the stepped portion 17 is provided in both the outer shoulder lateral groove 10A and the inner shoulder lateral groove 10B, it is not limited thereto. For example, the stepped portion 17 may be provided only in either the outer shoulder lateral groove 10A or the inner shoulder lateral groove 10B.

  As shown in FIG. 3 or FIG. 5, the outer shoulder land portion 6A and the inner shoulder land portion 6B are provided with a plurality of sipings 22 and 23 extending in the tire circumferential direction and the tire axial direction. The siping 22 includes, for example, a closed type siping 22A in which both ends are cut off at the outer shoulder land portion 6A. The siping 23 includes an open-type first siping 23A having an inner end communicating with the inner main groove 3B and a multi-end communicating with the other tread ground end Eb, and one end communicating with the inner main groove 3B and the other end. Is provided with an open-type second siping 23B that communicates with the inner shoulder lateral groove 10B. Such sipings 22 and 23 can improve the drainage of the outer shoulder land portion 6A and the inner shoulder land portion 6B, and can further improve the wet performance of the tire 1.

  As shown in FIG. 1 or 2, the outer shoulder land portion 6A of the present embodiment is provided with an outer auxiliary groove 26A extending in the tire circumferential direction outside the outer main groove 3A in the tire axial direction. Thus, the outer shoulder land portion 6A is provided with outer ribs 25A that are divided between the outer main groove 3A and the outer sub-groove 26A. Such an outer rib 25A can increase the lateral rigidity of the outer shoulder land portion 6A, and can improve the steering stability.

  The outer sub-groove 26A is connected to the inner end of the outer shoulder lateral groove 10A in the tire axial direction and continuously extends in the tire circumferential direction. Further, the groove width We of the outer sub-groove 26A is formed to be about 5 to 25% of the groove width Wa of the outer main groove 3A. Further, the groove depth He of the outer sub-groove 26A is formed to be about 40 to 60% of the groove depth Ha of the outer main groove 3A. Such outer sub-groove 26A can smoothly drain the water film between the outer shoulder land portion 6A and the road surface while maintaining the rigidity of the outer shoulder land portion 6A.

  As shown in FIG. 1, the crown land portion 7 of the present embodiment includes an outer crown land portion 7 </ b> A divided between the outer main groove 3 </ b> A and the crown main groove 4, and the inner main groove 3 </ b> B and the crown main groove 4. And an inner crown land portion 7 </ b> B divided between the two.

  As shown in FIG. 1 or 2, the outer crown land portion 7A of the present embodiment is provided with an inner sub-groove 26B extending in the tire circumferential direction on the inner side of the outer main groove 3A in the tire axial direction. As a result, the outer crown land portion 7A is provided with the inner rib 25B that is divided between the outer main groove 3A and the inner sub-groove 26B. Such an inner rib 25B can increase the lateral rigidity of the outer crown land portion 7A, and can improve the steering stability.

  The outer crown land portion 7A is provided with a plurality of outer crown lateral grooves 8A extending from the crown main groove 4 toward the outer side in the tire axial direction and communicating with the inner auxiliary groove 26B. The outer crown lateral groove 8A is provided so as to be inclined from the other side Si to the one side So, for example, from the crown main groove 4 toward the inner sub-groove 26B. Such outer crown lateral groove 8A and inner sub-groove 26B can improve the drainage of outer crown land portion 7A.

  The inner sub-groove 26B is connected to the inner end of the outer crown lateral groove 8A in the tire axial direction and continuously extends in the tire circumferential direction. Further, the groove width Wf and the groove depth Hf of the inner auxiliary groove 26B are formed in the same range as the groove width We and the groove depth Hf of the outer auxiliary groove 26A. Such an inner sub-groove 26B can smoothly drain the water film between the outer crown land portion 7A and the road surface while maintaining the rigidity of the outer crown land portion 7A.

  The outer crown land portion 7A may be provided with a plurality of sipings 24 extending in the tire circumferential direction and the tire axial direction, for example. The outer crown land portion 7A of the present embodiment is provided with a closed type siping 24A with one end interrupted. The siping 24A can further improve the drainage of the outer crown land portion 7A.

  The inner crown land portion 7B is provided with, for example, a plurality of inner crown lateral grooves 8B extending from the crown main groove 4 toward the outer side in the tire axial direction and communicating with the inner main groove 3B. For example, the inner crown lateral groove 8B is provided so as to be inclined from the one side So to the other side Si from the crown main groove 4 toward the inner main groove 3B. Such inner crown lateral groove 8B can improve the drainage of the inner crown land portion 7B.

  The inner crown land portion 7B of the present embodiment is provided with a plurality of sipings 24 as in the outer crown land portion 7A. These sipings 24 include a closed type siping 24A and an open type siping 24B whose both ends communicate with the inner crown lateral groove 8B. These sipings 24A and 24B can further improve the drainage of the inner crown land portion 7B.

  Although the present embodiment has been described in detail above, the present invention is not limited to this embodiment, and can be implemented with various modifications.

  The prototype has the basic pattern shown in FIG. 1 and was prototyped based on the specifications in Table 1. These radial tires for passenger cars were mounted on a test vehicle and traveled on each test course described later, and dry performance, wet performance, noise resistance performance and uneven wear resistance performance were evaluated.

For comparison, a tire (Comparative Example 1) having the basic pattern shown in FIG. 1 and including no stepped portion was manufactured. 7 has the basic pattern, that is, in each of the tread portions 2A and 2B, the shoulder lateral groove 10 extends from the tread grounding end E toward the shoulder main groove 3 and one side So in the tire state direction. The tire has a stepped portion 30 formed on the groove wall surfaces 12B and 14B of the other side Si of the shoulder lateral groove 10, and a wide portion 31 formed on the groove wall surface 14A of the one side So of the inner tread portion 2B. Comparative Example 2) was produced. And the performance of the tire of these comparative examples 1 and 2 was evaluated similarly to the Example.
Main common specifications such as tires are as follows.

Test vehicle: 2000cc domestic FF car Tire:
Size: 195 / 65R15
Internal pressure: 230 kPa
Each test method is as follows.

<Dry performance>
A test course consisting of dry asphalt and dry road surface was run, and the steering response and stability at high speed were evaluated by the driver's sensory evaluation. Evaluation was shown by the index | exponent which sets the comparative example 1 to 100. The larger the value, the better.

<Wet performance>
A test vehicle was entered while gradually increasing the speed in the range of 50 to 80 km / h on a test course in which a water pool with a depth of 5 mm and a length of 20 m was provided on an asphalt road surface with a radius of 100 m. ) Was measured. Then, an average lateral G at a speed of 50 to 80 km / h was calculated (lateral hydroplaning test), and an index with Comparative Example 1 as 100 was shown. The larger the value, the better.

<Noise resistance>
A test course consisting of a dry road surface was run at a speed of 50 km / h, and the noise at that time was measured with a microphone installed in the left ear of the driver's seat and a microphone located at the height of the ear in the center of the rear seat. And the reciprocal number of measured noise db (A) was shown by the index | exponent which sets the comparative example 1 to 100. FIG. The larger the value, the better.

<Uneven wear resistance>
After running a test course consisting of a dry road surface for 10,000 km at a speed of 100 km / h, the height from the bottom of the shoulder lateral groove to each groove edge was measured. Evaluation was shown by the index | exponent which sets the comparative example 1 to 100. The larger the value, the better.

  As shown in Table 1, it was confirmed that the tires of the examples could improve the dry performance, noise resistance performance, and uneven wear resistance performance while suppressing the decrease in wet performance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Shoulder main groove 6 Shoulder land part 10A, 10B Shoulder lateral groove 11A, 11B Groove edge 12A, 12B Groove wall surface 13A, 13B Groove edge 14A, 14B Groove wall surface 16 Groove bottom part 17 Stepped part 17A Outer wall surface Part 17B Stepped surface part 17C Inner wall surface part E Tread grounding end TW Tread grounding width C Tire equator So One side Si Other side

Claims (7)

Air in which a shoulder land portion is divided between the shoulder main groove and the tread ground end by providing a shoulder main groove extending continuously in the tire circumferential direction on at least one tread ground end side in the tread portion. A tire containing
The at least one shoulder land portion is provided with a plurality of shoulder lateral grooves extending from the tread grounding end toward the shoulder main groove and inclined to one side in the tire circumferential direction,
Each of the shoulder lateral grooves has, in a cross section perpendicular to the center line between the groove edges, the groove wall on the one side, the groove wall on the other side facing the groove wall on the one side, and a groove bottom portion having a maximum depth. Including
The one-side groove wall surface includes an outer wall surface portion extending inward in the tire radial direction from the groove edge on the one side, and a groove width direction from a tire radial inner end of the outer wall surface portion toward a center side of the shoulder lateral groove. A stepped portion comprising a step surface portion extending from the inner wall surface portion extending from the end of the step surface portion to the inside in the tire radial direction and reaching the groove bottom,
The pneumatic tire according to claim 1, wherein the stepped portion is provided at a position including at least the tread grounding end.   In the transverse cross section, the shoulder transverse groove has a ratio (W1 / W2) of a width W1 of the stepped surface portion in the groove width direction to a groove width W2 between groove edges of the shoulder transverse groove of 0.15 to 0.7. The pneumatic tire according to claim 1.   In the transverse cross section, the shoulder lateral groove has a ratio (h / H) between a height h in the tire radial direction from the groove bottom to the stepped surface portion and a maximum depth H of the shoulder lateral groove (0.3). The pneumatic tire according to claim 1, which is 0.9.   In the transverse section, the groove wall surface on the other side of the shoulder lateral groove has a main part that smoothly extends with an inclination in a direction of reducing the groove width from the groove edge toward the groove bottom part, and the main part and the groove bottom part. The pneumatic tire according to any one of claims 1 to 3, further comprising an arc portion that smoothly connects the two. In the cross section, the main portion of the groove wall surface on the other side and the outer wall surface portion of the groove wall surface on the one side are inclined to reduce the groove width toward the groove bottom portion, respectively.
The pneumatic tire according to claim 4, wherein an inclination angle of the main portion is larger than an inclination angle of the outer wall surface portion. The tread portion is designated for mounting on the vehicle,
The tread portion includes an outer tread portion positioned on the vehicle outer side than the tire equator and an inner tread portion positioned on the vehicle inner side than the tire equator when the vehicle is mounted.
The shoulder main groove and the shoulder lateral groove are provided in the outer tread portion and the inner tread portion, respectively.
In each shoulder lateral groove provided in the outer tread portion, the stepped portion is formed in the entire range in the length direction of the shoulder lateral groove,
The air according to any one of claims 1 to 5, wherein each shoulder lateral groove provided in the inner tread portion has the stepped portion formed in a range of 30 to 60% in a length direction of the shoulder lateral groove. Enter tire.   The shoulder lateral grooves provided in the outer tread portion and the shoulder lateral grooves provided in the inner tread portion are inclined in opposite directions in the tire circumferential direction from the tread ground contact end toward the shoulder main groove. The pneumatic tire according to claim 6.