JP2019206263A - tire - Google Patents

Abstract

To provide a tire that can be improved in steering stability on a dry road surface and on-snow performance.SOLUTION: A tire has a tread part 2 whose direction of mounting on a vehicle is specified. The tread part 2 has an outer tread end To, an inner tread end Ti, an outer middle land part 7 and an inner middle land part 8. The inner middle lad part 8 is provided with an inner middle lateral groove 20 extending from a first vertical edge and terminating in the inner middle land part 8. The outer middle land part 7 is provided with an outer middle lateral groove 15 extending from the first vertical edge and terminating in the outer middle land part 7. The outer middle land part 7 is not provided with a lateral groove extending from a second vertical edge toward the first vertical edge and reaching a center position in a tire shaft direction of the outer middle land part 7. A ratio Li/Wi of a length Li of the inner middle lateral groove 20 to a width Wi of the inner middle land part 8 is larger than a ratio Lo/Wo of a length Lo of the outer middle lateral groove 15 to a width Wo of the outer middle land part 7.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tire, and more particularly to a tire that can be suitably implemented as an all-season tire.

  All-season tires require basic driving performance on snowy roads as well as dry road surfaces. In order to improve running performance on slippery snowy roads, tires are required to have a large snow column shearing force and a road surface scratching effect. The snow column shearing force is obtained by pressing the snow on the road surface with a lateral groove and shearing it. Therefore, in order to improve the performance on snow, it is effective to provide many long lateral grooves in the tread portion. In addition, the lateral groove and the edge of the sipe improve the traction by scratching the pressed snow road. As a related technique, there is Patent Document 1 below.

Japanese Unexamined Patent Publication No. 2015-013604

  Although the lateral grooves and sipes provided in the tread portion are useful for improving the performance on snow, there is a tendency that the pattern rigidity of the tread portion is lowered, and consequently the steering stability on the dry road surface is deteriorated.

  The present invention has been devised in view of the above problems, and has as its main object to provide a tire capable of improving the handling stability on a dry road surface and the performance on snow.

  The present invention is a tire having a tread portion in which the direction of mounting on a vehicle is specified, and the tread portion is located on an outer tread end located outside the vehicle when the vehicle is mounted, and an inner side positioned inside the vehicle when the vehicle is mounted A tread end; an outer middle land portion disposed between the outer tread end and the tire equator; and an inner middle land portion disposed between the inner tread end and the tire equator; Each of the land portion and the inner middle land portion includes a first vertical edge extending in the tire circumferential direction on the inner tread end side, a second vertical edge extending in the tire circumferential direction on the outer tread end side, and the first vertical edge. An inner middle lateral groove extending from the first vertical edge and interrupted in the inner middle land portion is provided in the inner middle land portion, and the outer middle land portion is provided on the inner middle land portion. An outer middle lateral groove extending from the first vertical edge and interrupted in the outer middle land portion is provided in the land portion, and the outer middle land portion is provided on the side of the first vertical edge from the second vertical edge. A lateral groove reaching the center position in the tire axial direction of the outer middle land portion is not provided, a width Wi in the tire axial direction of the inner middle land portion, and a length in the tire axial direction of the inner middle lateral groove The ratio Li / Wi with Li is larger than the ratio Lo / Wo between the width Wo of the outer middle land portion in the tire axial direction and the length Lo of the outer middle lateral groove in the tire axial direction.

  In the tire of the present invention, it is preferable that the length Li of the inner middle lateral groove is larger than the length Lo of the outer middle lateral groove.

  In the tire of the present invention, it is preferable that the inner middle land portion is provided with a first inner middle sipe extending from a discontinuous end of the inner middle lateral groove to the second vertical edge.

  In the tire of the present invention, it is preferable that a region where the first inner middle sipe is extended toward the outer tread end side intersects with a region where the outer middle lateral groove is extended toward the inner tread end side.

  In the tire of the present invention, it is preferable that the outer middle land portion is provided with a first outer middle sipe extending from a discontinuous end of the outer middle lateral groove to the second vertical edge.

  In the tire of the present invention, the inner middle land portion is not provided with a lateral groove extending from the second longitudinal edge to the first longitudinal edge side and reaching the center position of the inner middle land portion in the tire axial direction. Is desirable.

  In the tire according to the present invention, it is preferable that each of the inner middle lateral groove and the outer middle lateral groove extends with a constant groove width.

  Each of the outer middle land portion and the inner middle land portion arranged in the tread portion of the tire of the present invention extends in the tire circumferential direction on the inner tread end side and in the tire circumferential direction on the outer tread end side. A second vertical edge; and a tread surface between the first vertical edge and the second vertical edge.

  The inner middle land portion is provided with an inner middle lateral groove extending from the first vertical edge and interrupted in the inner middle land portion. The outer middle land portion is provided with an outer middle lateral groove extending from the first vertical edge and interrupted in the outer middle land portion. Such inner middle lateral grooves and outer middle lateral grooves can provide a snow column shearing force when traveling on snow. Further, the inner middle lateral groove and the outer middle lateral groove prevent a decrease in rigidity on the second vertical edge side of each land portion, and suppress a deterioration in steering stability. In addition, the outer middle land portion is not provided with a lateral groove extending from the second vertical edge to the first vertical edge side and reaching the center position of the outer middle land portion in the tire axial direction. In general, this type of groove greatly reduces the rigidity of the land near the second vertical edge, but by not providing this type of groove, the rigidity of the outer middle land is further maintained, and excellent steering stability is achieved. Is demonstrated.

  The ratio Li / Wi between the width Wi of the inner middle land portion in the tire axial direction and the length Li of the inner middle lateral groove in the tire axial direction is the width Wo of the outer middle land portion in the tire axial direction and the tire in the outer middle lateral groove. It is larger than the ratio Lo / Wo with the length Lo in the axial direction. Thereby, in the inner middle land portion where a relatively large ground pressure acts, the length of the lateral groove is ensured, and excellent performance on snow is exhibited.

  As described above, the tire of the present invention can improve the handling stability on the dry road surface and the performance on snow.

It is an expanded view of the tread part of the tire of one embodiment of the present invention. FIG. 2 is an enlarged view of an outer middle land portion and an inner middle land portion of FIG. 1. (A) is the sectional view on the AA line of FIG. 2, (B) is the sectional view on the BB line of FIG. 2, (C) is the cross section of the 2nd outer side middle sipe in other embodiment. FIG. It is CC sectional view taken on the line of FIG. It is an enlarged view of the outer side shoulder land part of FIG. It is an enlarged view of the inner side shoulder land part of FIG. It is an enlarged view of the outer middle land part and the inner middle land part of the tire of a comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread portion 2 of a tire 1 showing an embodiment of the present invention. The tire 1 of the present embodiment is configured as a pneumatic tire, for example. In the present embodiment, as a preferable aspect, an all-season tire intended for mounting on a passenger car or SUV is shown.

  As shown in FIG. 1, the tire 1 of the present invention has a tread portion 2 in which the direction of mounting on the vehicle is specified. The tread portion 2 of the tire 1 of the present embodiment has an asymmetric tread pattern. The tread portion 2 has an outer tread end To positioned on the vehicle outer side when the tire 1 is mounted on the vehicle, and an inner tread end Ti positioned on the vehicle inner side when the vehicle is mounted. The direction of mounting on the vehicle is displayed, for example, with letters or symbols on a sidewall (not shown).

  In the case of a pneumatic tire, the outer tread end To and the inner tread end Ti are the contact positions on the outermost side in the tire axial direction when a normal load is applied to the tire 1 in a normal state and the tire 1 contacts the plane with a camber angle of 0 °. The normal state is a state in which the tire is assembled on the normal rim and filled with the normal internal pressure, and further, there is no load. In this specification, when there is no notice in particular, the dimension of each part of a tire, etc. are values measured in the normal state.

  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, “Standard Rim” for JATMA, “Design Rim” for TRA, and “ETRTO” If there is "Measuring Rim".

  “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. “JAMATA” is “maximum air pressure”, TRA is “TIRE LOAD LIMITS AT” The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

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

  In the tread portion 2 of the present embodiment, for example, a plurality of main grooves 3 extending continuously in the tire circumferential direction are provided. The main groove 3 includes, for example, an outer shoulder main groove 4 disposed on the outermost tread end To side, an inner shoulder main groove 5 disposed on the innermost tread end Ti side, and a crown main portion disposed therebetween. And groove 6. In the present embodiment, one crown main groove 6 is provided on the tire equator C. Thereby, the tread part 2 is divided into four land parts. In another aspect, the tread portion 2 may be divided into five land portions by, for example, the outer shoulder main groove 4 and the inner shoulder main groove 5 and the two crown main grooves 6 sandwiching the tire equator C. .

  The distance L1 in the tire axial direction from the groove center line of the outer shoulder main groove 4 or the inner shoulder main groove 5 to the tire equator C is preferably, for example, 0.15 to 0.25 times the tread width TW. The tread width TW is a distance in the tire axial direction from the outer tread end To to the inner tread end Ti in the normal state.

  Each main groove 3 extends linearly, for example. Each main groove 3 may extend in a zigzag shape, for example. The groove width W1 of the main groove 3 is preferably 4.0% to 7.0% of the tread width TW, for example. The groove depth of the main groove 3 is preferably 5.0 to 12.0 mm, for example. As a result, the handling stability on the dry road surface and the performance on snow can be improved in a balanced manner.

  The tread portion 2 of this embodiment is divided into an outer middle land portion 7, an inner middle land portion 8, an outer shoulder land portion 9, and an inner shoulder land portion 10. The outer middle land portion 7 is disposed between the tire equator C and the outer tread end To, and is specifically divided between the crown main groove 6 and the outer shoulder main groove 4. The inner middle land portion 8 is disposed between the tire equator C and the inner tread end Ti, and is specifically divided between the crown main groove 6 and the inner shoulder main groove 5. The outer shoulder land portion 9 is divided between the outer shoulder main groove 4 and the outer tread end To. The inner shoulder land portion 10 is divided between the inner shoulder main groove 5 and the inner tread end Ti.

  FIG. 2 shows an enlarged view of the outer middle land portion 7 and the inner middle land portion 8. 2, the outer middle land portion 7 includes a first vertical edge 7a extending in the tire circumferential direction on the inner tread end Ti side, and a second vertical edge 7b extending in the tire circumferential direction on the outer tread end To side. And a tread surface between the first vertical edge 7a and the second vertical edge 7b. Similarly, the inner middle land portion 8 includes a first vertical edge 8a extending in the tire circumferential direction on the inner tread end Ti side, a second vertical edge 8b extending in the tire circumferential direction on the outer tread end To side, and a first vertical edge. 8a and a tread between the second vertical edges 8b.

  The outer middle land portion 7 is provided with an outer middle lateral groove 15. The outer middle lateral groove 15 extends from the first vertical edge 7 a and is interrupted in the outer middle land portion 7. The outer middle land portion 7 is not provided with a lateral groove extending from the second vertical edge 7b to the first vertical edge 7a side and reaching the center position of the outer middle land portion 7 in the tire axial direction.

  An inner middle lateral groove 20 is provided in the inner middle land portion 8. The inner middle lateral groove 20 extends from the first vertical edge 8 a and is interrupted in the inner middle land portion 8.

  The inner middle lateral groove 20 and the outer middle lateral groove 15 can provide a snow column shear force when running on snow. Further, the inner middle lateral groove 20 and the outer middle lateral groove 15 prevent a decrease in rigidity on the second vertical edge side of each land portion, and suppress a deterioration in steering stability. Moreover, the outer middle land portion 7 is not provided with a lateral groove that extends from the second vertical edge 7b toward the first vertical edge 7a and reaches the center position of the outer middle land portion 7 in the tire axial direction. In general, this type of groove greatly reduces the rigidity of the land portion near the second vertical edge 7b, but by not providing this type of groove, the rigidity of the outer middle land portion 7 is further maintained and excellent maneuvering is achieved. Stability is demonstrated.

  The ratio Li / Wi between the width Wi of the inner middle land portion 8 in the tire axial direction and the length Li of the inner middle lateral groove 20 in the tire axial direction is equal to the width Wo of the outer middle land portion 7 in the tire axial direction and the outer middle width. It is larger than the ratio Lo / Wo with the length Lo of the lateral groove 15 in the tire axial direction. Thereby, in the inner middle land portion 8 where a relatively large ground pressure acts, the length of the lateral groove is ensured, and excellent on-snow performance is exhibited.

  Further, such a lateral groove arrangement can relatively increase the rigidity of the outer middle land portion 7. As a result, a tire having a large self-aligning torque (hereinafter sometimes referred to as “SAT”) is obtained. For example, when tires with a large SAT are mounted on all wheels of an FF passenger car, the cornering power of the front wheels (hereinafter sometimes referred to as “CP”) is relatively reduced by the SAT, and the front wheel CP and rear The CP of the wheel approaches. Therefore, the passenger car having the tires of the present invention mounted on all the wheels easily shifts to a steady state in which the cornering force of the front wheels and the cornering force of the rear wheels are substantially balanced when the steering angle is given to the front wheels. The steering stability can be demonstrated.

  The outer middle land portion 7 is provided with the outer middle lateral groove 15, the first outer middle sipe 16, and the second outer middle sipe 17. The first outer middle sipe 16 extends from the discontinuous end of the outer middle lateral groove 15 to the second vertical edge 7b. The second outer middle sipe 17 extends from the first vertical edge 7 a and is interrupted on the second vertical edge 7 b side from the interrupted end of the outer middle lateral groove 15. In the present specification, “sipe” is a notch having a width of less than 1.5 mm, and in a preferred embodiment, the width of the sipe is, for example, 0.5 to 1.0 mm.

  The first outer middle sipe 16 is a notch with a small width, and can easily open the outer middle lateral groove 15 while suppressing an excessive decrease in rigidity of the land portion, thereby increasing the amount of snow entering the outer middle lateral groove. The second outer middle sipe 17 is a land piece between the outer middle lateral groove 15 and the second outer middle sipe 17 on the first vertical edge 7a side while maintaining rigidity on the second vertical edge 7b side of the outer middle land portion 7. Can be moved moderately, and as a result, the snow that has entered the outer middle lateral groove 15 can be strongly pressed. As described above, in the present embodiment, the arrangement of the first outer middle sipe 16 and the second outer middle sipe 17 increases the snow column shear force of the outer middle lateral groove 15 and provides excellent on-snow performance.

  In a desirable mode, the outer middle land portion 7 is not provided with a lateral groove extending from the second vertical edge 7 b and exceeding 0.25 times the width Wo of the outer middle land portion 7. As a more desirable mode, in the present embodiment, the outer middle land portion 7 is not provided with a lateral groove extending from the second vertical edge 7b, and only the sipe is connected to the second vertical edge 7b. Further, the second vertical edge 7b is not provided with a chamfered portion in which a corner portion between the tread surface and the side surface of the land portion is recessed. Such an outer middle land portion 7 has higher rigidity in the vicinity of the second vertical edge 7b, and further excellent steering stability can be expected.

  The ratio Lo / Wo between the width Wo of the outer middle land portion 7 in the tire axial direction and the length Lo of the outer middle lateral groove 15 in the tire axial direction is preferably 0.40 to 0.60, for example. The outer middle lateral groove 15 of the present embodiment reaches, for example, the center position of the outer middle land portion 7 in the tire axial direction. Such outer middle lateral grooves 15 can improve the steering stability on the dry road surface and the performance on snow with a good balance.

  The outer middle lateral groove 15 is preferably inclined with respect to the tire axial direction, for example. The angle of the outer middle lateral groove 15 with respect to the tire axial direction is preferably less than 30 °, for example, 15 to 25 °. Such an outer middle lateral groove 15 can be expected to have a large traction on the snow.

  The outer middle lateral groove 15 preferably extends with a constant groove width, for example. It should be noted that extending with a constant groove width includes an aspect in which the difference between the maximum groove width and the minimum groove width of the lateral grooves is less than 5% of the maximum groove width. The groove width W2 of the outer middle lateral groove 15 is preferably 0.25 to 0.40 times the groove width W1 of the main groove 3, for example.

  For example, the first outer middle sipe 16 is preferably inclined in the same direction as the outer middle lateral groove 15 with respect to the tire axial direction. The angle of the first outer middle sipe 16 with respect to the tire axial direction is preferably less than 30 °.

  3A is a cross-sectional view of the outer middle lateral groove 15 and the first outer middle sipe 16 taken along the line AA. As shown in FIG. 3A, the depth d2 of the first outer middle sipe 16 is preferably 0.50 to 0.70 times the depth d1 of the outer middle lateral groove 15. Such a first outer middle sipe 16 can improve on-snow performance while preventing a decrease in rigidity of the outer middle land portion 7.

  As shown in FIG. 2, for example, the second outer middle sipe 17 is interrupted on the second vertical edge 7 b side with respect to the center position of the outer middle land portion 7 in the tire axial direction. The length L2 of the second outer middle sipe 17 in the tire axial direction is, for example, 0.65 to 0.85 times the width Wo of the outer middle land portion 7 in the tire axial direction. The length L2 of the second outer middle sipes 17 is preferably 1.40 to 1.60 times the length Lo of the outer middle lateral grooves 15 in the tire axial direction. As a result, the land piece between the outer middle lateral groove 15 and the second outer middle sipes 17 becomes easier to move, and when running on snow, the snow in the outer middle lateral groove 15 is strongly pressed and a greater snow column shear force is obtained. It is done.

  For example, the second outer middle sipes 17 are inclined in the same direction as the outer middle lateral grooves 15 with respect to the tire axial direction. The angle of the second outer middle sipe 17 with respect to the tire axial direction is, for example, 10 to 30 °.

  FIG. 3B is a cross-sectional view of the second outer middle sipe 17 taken along line BB. As shown in FIG. 3 (B), the second outer middle sipes 17 are, for example, at the shallow bottom portion 17a where the groove bottom is raised at the end portion on the first vertical edge 7a side, and on the discontinuous end on the second vertical edge 7b side. And a gradually decreasing portion 17b having a gradually decreasing depth. The depth d4 of the shallow bottom portion 17a is 0.70 to 0.90 times the maximum depth d3 of the second outer middle sipe 17. Since the second outer middle sipe 17 having the shallow bottom portion 17a and the gradually decreasing portion 17b is suppressed from being excessively opened, it is possible to prevent the steering stability on the dry road surface from being lowered.

  FIG. 3C shows a cross-sectional view of another embodiment of the second outer middle sipe 17. As shown in FIG. 3C, the depth of the second outer middle sipe 17 of this embodiment is gradually reduced from the end on the first vertical edge 7a side toward the discontinuous end. The ratio d5 / d3 between the maximum depth d3 and the minimum depth d5 of the second outer middle sipe 17 is, for example, 0.20 to 0.40. In the outer middle land portion 7 in which the second outer middle sipes 17 are arranged, the rigidity in the tire circumferential direction gradually increases toward the second vertical edge 7b, so that the steering response at the time of turning can be made linear. it can.

  As shown in FIG. 2, the outer middle land portion 7 is provided with a chamfered portion 18 having a recessed corner portion between the tread surface and the side surface of the land portion on the first vertical edge 7a side. The chamfered portion 18 of the present embodiment is connected to, for example, the outer middle lateral groove 15. Such a chamfered portion 18 suppresses uneven wear of the outer middle land portion 7. Further, the chamfered portion 18 helps to unite the snow in the outer middle lateral groove 15 and the snow in the crown main groove 6 when traveling on snow, and thus can suppress clogging of the snow in the outer middle lateral groove 15.

  The ratio Li / Wi between the width Wi of the inner middle land portion 8 in the tire axial direction and the length Li of the inner middle lateral groove 20 in the tire axial direction is more preferably, for example, 0.70 to 0.90. The length Li of the inner middle lateral groove 20 is preferably larger than the length Lo of the outer middle lateral groove 15. Thereby, the performance on snow is further enhanced.

  The inner middle land portion 8 is not provided with a lateral groove extending from the second vertical edge 8b toward the first vertical edge 8a and reaching the center position of the inner middle land portion 8 in the tire axial direction. In a desirable mode, the inner middle land portion 8 is not provided with a lateral groove extending from the second vertical edge 8 b and exceeding 0.25 times the width Wo of the inner middle land portion 8. As a more desirable mode, in the present embodiment, the inner middle land portion 8 is not provided with a lateral groove extending from the second vertical edge 8b, and only the sipe is connected to the second vertical edge 8b. Further, the second vertical edge 8b is not provided with a chamfered portion in which a corner portion between the tread surface and the side surface of the land portion is recessed. Such an inner middle land portion 8 can further enhance steering stability on a dry road surface.

  For example, the inner middle lateral groove 20 is preferably inclined in the same direction as the outer middle lateral groove 15. The angle of the inner middle lateral groove 20 with respect to the tire axial direction is preferably less than 30 °, for example, 15 to 25 °. Such an inner middle horizontal groove 20 can improve the traction on the snow and the turning performance in a well-balanced manner.

  The inner middle lateral groove 20 preferably extends with a constant groove width. The groove width W3 of the inner middle lateral groove 20 is preferably 0.25 to 0.40 times the groove width W1 of the main groove 3, for example.

  The inner middle land portion 8 is provided with a first inner middle sipe 21 and a second inner middle sipe 22.

  For example, the first inner middle sipe 21 extends from the discontinuous end of the inner middle lateral groove 20 to the second vertical edge 8b. For example, the first inner middle sipe 21 is preferably inclined in the same direction as the inner middle lateral groove 20 with respect to the tire axial direction. The angle of the first inner middle sipe 21 with respect to the tire axial direction is preferably less than 30 °, for example.

  The region where the first inner middle sipe 21 is extended to the outer tread end To side preferably intersects the region where the outer middle lateral groove 15 is extended to the inner tread end Ti side in the crown main groove 6. Such an arrangement of the lateral grooves and sipes makes it easier to open each lateral groove moderately and helps to improve the performance on snow.

  For example, the second inner middle sipe 22 extends from the first vertical edge 8a to the second vertical edge 8b. Such a 2nd inner side middle sipe 22 can raise the traction on snow.

  For example, the second inner middle sipe 22 is preferably inclined in the same direction as the inner middle lateral groove 20 with respect to the tire axial direction. The angle of the second inner middle sipe 22 with respect to the tire axial direction is, for example, 10 to 30 °.

  4 is a cross-sectional view of the second inner middle sipe 22 taken along the line CC. As shown in FIG. 4, the second inner middle sipe 22 preferably has shallow bottom portions 22 a at both ends in the tire axial direction. The depth d7 of the shallow bottom portion 22a is, for example, 0.70 to 0.90 times the maximum depth d6 of the second inner middle sipe 22. Such a 2nd inner side middle sipe 22 can improve the performance on snow, suppressing the fall of steering stability.

  As shown in FIG. 2, the inner middle land portion 8 is provided with a chamfered portion 23 having a recessed corner portion between the tread surface and the side surface of the land portion on the first vertical edge 8a side. The chamfered portion 23 of the present embodiment is connected to, for example, the inner middle lateral groove 20. Such a chamfer 23 can suppress uneven wear of the inner middle land portion 8. Further, the length in the tire circumferential direction of the chamfered portion 23 provided in the inner middle land portion 8 is larger than the length in the tire circumferential direction of the chamfered portion 18 provided in the outer middle land portion 7. Thereby, the difference in the progress of wear between the inner middle land portion 8 and the outer middle land portion 7 due to the difference in contact pressure is reduced.

  FIG. 5 shows an enlarged view of the outer shoulder land portion 9. As shown in FIG. 5, the outer shoulder land portion 9 is provided with an outer shoulder lateral groove 25, a first outer shoulder sipe 26, and a second outer shoulder sipe 27.

  The outer shoulder lateral groove 25 extends, for example, from the outer shoulder main groove 4 to the outer tread end To. The outer shoulder lateral groove 25 is inclined, for example, in the same direction as the outer middle lateral groove 15 with respect to the tire axial direction. The angle of the outer shoulder lateral groove 25 with respect to the tire axial direction is preferably 10 to 30 °, for example.

  The outer shoulder lateral groove 25 of the present embodiment includes a first groove portion 25a extending from the outer shoulder main groove 4 and a second groove portion 25b extending to the outer tread end To with a groove width larger than the first groove portion 25a. Including. In a more desirable mode, one edge of the first groove portion 25a and one edge of the second groove portion 25b are smoothly continuous.

  The groove width W4 of the first groove portion 25a is desirably smaller than the groove width W2 (shown in FIG. 2) of the outer middle lateral groove 15, for example. The groove width W5 of the second groove portion 25b is preferably larger than the groove width W2 of the outer middle lateral groove 15, for example. The groove width W5 of the second groove portion 25b is preferably, for example, 1.70 to 2.00 times the groove width W4 of the first groove portion 25a. Such outer shoulder lateral grooves 25 can improve the steering stability on the dry road surface and the performance on snow with a good balance.

  The length L3 of the first groove portion 25a in the tire axial direction is, for example, 0.35 to 0.55 times the width W6 of the outer shoulder land portion 9 in the tire axial direction. Further, the length L3 of the first groove portion 25a in the tire axial direction is preferably larger than the length Lo (shown in FIG. 2) of the outer middle lateral groove 15 in the tire axial direction.

  For example, the second groove portion 25b desirably has a depth greater than that of the first groove portion 25a. The depth of the second groove portion 25b is preferably 1.5 to 2.0 times the depth of the first groove portion 25a, for example. Such outer shoulder lateral grooves 25 exhibit excellent on-snow performance due to the second groove portions 25b while preventing the rigidity of the land portions from being lowered by the first groove portions 25a.

  The first outer shoulder sipe 26 is, for example, a closed sipe in which both ends are interrupted in the outer shoulder land portion 9. In the present embodiment, two first outer shoulder sipes 26 are provided between two outer shoulder lateral grooves 25 adjacent in the tire circumferential direction.

  The length of the first outer shoulder sipe 26 in the tire axial direction is preferably larger than the length of the first groove portion 25a of the outer shoulder lateral groove 25 in the tire axial direction, for example.

  The second outer shoulder sipe 27 extends from the outer tread end To to the tire equator C side and is interrupted in the outer shoulder land portion 9. In the present embodiment, two second outer shoulder sipes 27 are provided between two outer shoulder lateral grooves 25 adjacent in the tire circumferential direction. In a desirable mode, the second outer shoulder sipe 27 and the first outer shoulder sipe 26 do not overlap in the tire axial direction. Such a second outer shoulder sipe 27 is useful for enhancing the wandering performance on snow while maintaining the rigidity of the land portion.

  The outer shoulder land portion 9 is provided with a chamfered portion 28 in which a corner portion between the tread surface and the side surface of the land portion is recessed on the outer shoulder main groove 4 side. The chamfered portion 28 of the present embodiment is connected to the outer shoulder lateral groove 25, for example. Such a chamfer 28 can form a large snow column together with the outer shoulder lateral groove 25, and can improve the performance on snow.

  As shown in FIG. 1, it is desirable that a region obtained by extending the chamfered portion 28 provided in the outer shoulder land portion 9 along the tire axial direction intersects the second outer middle sipe 17. Such an arrangement of the chamfered portion 28 is useful for suppressing uneven wear of the outer shoulder land portion 9.

  FIG. 6 shows an enlarged view of the inner shoulder land portion 10. As shown in FIG. 6, the inner shoulder land portion 10 is provided with an inner shoulder lateral groove 30, a first inner shoulder sipe 31, and a second inner shoulder sipe 32.

  For example, the inner shoulder lateral groove 30 extends from the inner shoulder main groove 5 to the inner tread end Ti. For example, the inner shoulder lateral groove 30 is inclined in the same direction as the inner middle lateral groove 20 with respect to the tire axial direction. The angle of the inner shoulder lateral groove 30 with respect to the tire axial direction is preferably 10 to 30 °, for example.

  The groove width W7 of the inner shoulder lateral groove 30 is preferably at least larger than the groove width W4 (shown in FIG. 5) of the first groove portion 25a of the outer shoulder lateral groove 25. In a more desirable mode, the groove width W7 of the inner shoulder lateral groove 30 is larger than both the groove width W2 of the outer middle lateral groove 15 (shown in FIG. 2) and the groove width W3 of the inner middle lateral groove 20 (shown in FIG. 2). Such an inner shoulder lateral groove 30 is useful for exhibiting excellent performance on snow.

  For example, the inner shoulder lateral groove 30 preferably has a shallow bottom portion with a raised groove bottom at the end on the inner shoulder main groove 5 side. The length of the shallow bottom portion in the tire axial direction is desirably smaller than the length of the first groove portion 25a (shown in FIG. 5) of the outer shoulder lateral groove 25 in the tire axial direction. Further, the depth of the shallow bottom portion is, for example, 0.55 to 0.70 times the maximum depth of the inner shoulder lateral groove 30.

  The first inner shoulder sipe 31 extends, for example, from the inner shoulder main groove 5 toward the inner tread end Ti and is interrupted in the inner shoulder land portion 10. In the present embodiment, two first inner shoulder sipes 31 are provided between two inner shoulder lateral grooves 30 adjacent in the tire circumferential direction. The length L4 of the first inner shoulder sipe 31 in the tire axial direction is, for example, 0.75 to 0.90 times the width W8 of the inner shoulder land portion 10 in the tire axial direction.

  The second inner shoulder sipe 32 extends from the inner tread end Ti to the tire equator C side and is interrupted in the inner shoulder land portion 10. In the present embodiment, two second inner shoulder sipes 32 are provided between two inner shoulder lateral grooves 30 adjacent in the tire circumferential direction. In a desirable mode, the second inner shoulder sipe 32 and the first inner shoulder sipe 31 do not overlap in the tire axial direction. Such a 2nd inner side shoulder sipe 32 can improve the wandering performance on snow, maintaining the rigidity of the inner side shoulder land part 10. FIG.

  The inner shoulder land portion 10 is provided with a chamfered portion 33 in which a corner portion between the tread surface and the side surface of the land portion is recessed on the inner shoulder main groove 5 side. The chamfered portion 33 of the present embodiment is connected to, for example, the inner shoulder lateral groove 30 and the first inner shoulder sipe 31. Such a chamfered portion 33 can suppress uneven wear of the inner shoulder land portion 10.

  As mentioned above, although preferable embodiment of the tire of this invention was described in detail, this invention is not limited to said specific embodiment, It can implement by changing into a various aspect.

A tire of size 185 / 65R15 having the basic pattern of FIG. As a comparative example, as shown in FIG. 7, the ratio Lo / Wo between the width Wo of the outer middle land portion a in the tire axial direction and the length Lo of the outer middle lateral groove c in the tire axial direction is the inner middle land portion b. A tire having the same ratio Li / Wi between the width Wi in the tire axial direction and the length Li in the tire axial direction of the outer middle lateral groove d was manufactured. The tire of the comparative example has a tread pattern substantially the same as that shown in FIG. 1 except for the above-described configuration. The test stability of each test tire on the dry road surface and the performance on snow were tested. The common specifications and test methods for each test tire are as follows.
Wearing rim: 15 × 6.0J
Tire internal pressure: Front wheel 220 kPa, rear wheel 210 kPa
Test vehicle: 1300cc displacement, front-wheel drive vehicle Tire mounting position: all wheels

<Operation stability on dry road>
Steering stability when driving on the dry road surface with the test vehicle was evaluated by the driver's sensuality. A result is a score which makes a comparative example 100, and shows that the steering stability on a dry road surface is excellent, so that a numerical value is large.

<Snow performance>
The performance when driving on a snowy road with the above test vehicle equipped with each test tire was evaluated by the driver's sensuality. A result is a score which makes a comparative example 100, and shows that performance on snow is excellent, so that a numerical value is large.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tires of the examples had improved handling stability on the dry road surface and performance on snow compared to the tires of the comparative examples.

2 tread portion 7 outer middle land portion 8 inner middle land portion 15 outer middle lateral groove 20 inner middle lateral groove To outer tread end Ti inner tread end Wi inner middle land portion tire axial width Wo outer middle land portion tire axial direction Width Li Length of the inner middle lateral groove in the tire axial direction Lo Length of the outer middle lateral groove in the tire axial direction

Claims (7)

A tire having a tread portion in which a direction of mounting on a vehicle is specified,
The tread portion includes an outer tread end positioned outside the vehicle when the vehicle is mounted, an inner tread end positioned inside the vehicle when the vehicle is mounted, and an outer middle land portion disposed between the outer tread end and the tire equator. An inner middle land portion disposed between the inner tread end and the tire equator,
Each of the outer middle land portion and the inner middle land portion has a first vertical edge extending in the tire circumferential direction on the inner tread end side, a second vertical edge extending in the tire circumferential direction on the outer tread end side, A tread surface between the first vertical edge and the second vertical edge;
The inner middle land portion is provided with an inner middle lateral groove extending from the first vertical edge and interrupted in the inner middle land portion,
The outer middle land portion is provided with an outer middle lateral groove extending from the first vertical edge and interrupted in the outer middle land portion, and the outer middle land portion is provided with the first vertical edge from the second vertical edge. There is no lateral groove extending to the edge side and reaching the center position in the tire axial direction of the outer middle land portion,
The ratio Li / Wi between the width Wi in the tire axial direction of the inner middle land portion and the length Li in the tire axial direction of the inner middle lateral groove is equal to the width Wo of the outer middle land portion in the tire axial direction and the outer side. It is larger than the ratio Lo / Wo with the length Lo of the middle lateral groove in the tire axial direction,
tire.   The tire according to claim 1, wherein the length Li of the inner middle lateral groove is larger than the length Lo of the outer middle lateral groove.   The tire according to claim 1 or 2, wherein the inner middle land portion is provided with a first inner middle sipe extending from a discontinuous end of the inner middle lateral groove to the second vertical edge.   The tire according to any one of claims 1 to 3, wherein a region where the first inner middle sipe is extended to the outer tread end side intersects with a region where the outer middle lateral groove is extended to the inner tread end side.   The tire according to any one of claims 1 to 4, wherein the outer middle land portion is provided with a first outer middle sipe extending from a discontinuous end of the outer middle lateral groove to the second vertical edge.   6. The inner middle land portion is not provided with a lateral groove extending from the second vertical edge toward the first vertical edge side and reaching the center position in the tire axial direction of the inner middle land portion. The tire according to any one.   The tire according to any one of claims 1 to 6, wherein each of the inner middle lateral groove and the outer middle lateral groove extends with a constant groove width.

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