JP2015136952A - pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve snow road performance.SOLUTION: A pneumatic tire 1 is designated in an orientation of attachment to a vehicle. An outside middle land part 8 is formed between a first main groove 3 and a second main groove 4. A first portion 6 and a second portion 7 whose groove width is larger than that of the first portion 6 are alternately formed in the first main groove 3 in a tire circumferential direction. At the outside middle land part 8, there are formed a plurality of pieces of middle inclined grooves 12 which do not communicate with either of the first main groove 3 and the second main groove 4, a plurality of middle lag grooves 13 which connect the second portion 7 of the first main groove 3 and the middle inclined grooves 12, and inside middle lag grooves 14 which connect the middle inclined grooves 12 and the second main groove 4. The outside middle lag grooves 13 are formed at positions different from the inside middle lag grooves 14 in the tire circumferential direction.

Description

  The present invention relates to a pneumatic tire having improved snowy road performance while maintaining steering stability performance.

    Winter pneumatic tires have the opportunity to run on dry roads as well as snowy roads. Therefore, in such a pneumatic tire for winter, it is required to improve not only snow road performance but also steering stability performance at a high level and in a well-balanced manner.

  For example, in order to increase snow column shearing force and improve snow road performance, a pneumatic tire having a large volume lateral groove in the tread portion has been proposed.

  However, the pneumatic tire as described above has a problem that steering stability performance deteriorates due to a decrease in rigidity of the tread portion.

JP 2011-51425 A

  The present invention has been devised in view of the above circumstances, and a main object thereof is to provide a pneumatic tire having excellent snow road performance while maintaining steering stability performance.

  The present invention provides an air having a tread portion having an outer tread end positioned outside the vehicle when the vehicle is mounted and an inner tread end positioned inside the vehicle when the vehicle is mounted. A first main groove extending continuously in the tire circumferential direction on the outermost tread end side, and adjacent to the first main groove on the inner tread end side and on the tire tread. By providing the second main groove extending continuously in the direction, an outer middle land portion is formed between the first main groove and the second main groove, and the first main groove is , Second portions having a groove width larger than that of the first portion are alternately formed in the tire circumferential direction, and the outer middle land portion communicates directly with both the first main groove and the second main groove. A plurality of middle inclined grooves not formed, and the first A plurality of outer middle lug grooves that connect the second portion of the groove and the middle inclined groove, and an inner middle lug groove that connects between the middle inclined groove and the second main groove, and the outer middle lug groove is The inner middle lug groove and the tire circumferential direction are provided at different positions.

  In the pneumatic tire according to the present invention, it is preferable that the groove width in the tire axial direction of the first portion is 60% to 80% of the groove width in the tire axial direction of the second portion.

  In the pneumatic tire according to the present invention, the first main groove includes a first inclined portion in which a groove edge on the tire equator side is inclined with respect to the tire circumferential direction, and a tire circumferential direction with respect to the first inclined portion. It is desirable that the second inclined portions having a large angle are alternately arranged in a zigzag shape, and the second inclined portions are smoothly connected to one groove edge of the outer middle lug groove.

  In the pneumatic tire according to the present invention, it is preferable that the first inclined portion has an arc shape that is a smooth convex toward the tire equator.

  In the pneumatic tire according to the present invention, the middle inclined groove includes a first middle inclined portion that gradually increases in groove width from an inner end portion on the inner tread end side to an outer end portion on the outer tread end side, and It is desirable to have a second middle inclined portion that connects between the outer end portion of the first middle inclined portion and the outer middle lug groove and has a groove width smaller than that of the first middle inclined portion.

  In the pneumatic tire according to the present invention, it is preferable that the first middle inclined portion has the inner end portion provided on the tire equator.

  In the pneumatic tire of the present invention, an outer middle land portion provided with a middle inclined groove, an outer middle lug groove, and an inner middle lug groove is formed between the first main groove and the second main groove. As for the 1st main groove, the 1st part and the 2nd part whose groove width is larger than the 1st part are alternately formed in the tire peripheral direction. That is, the second portion has a portion protruding from the first portion in the tire axial direction. The overhanging portion presses and hardens the snow and shears, thereby exerting a snow column shear force and improving snow road performance.

  Such a first main groove is provided on the outermost tread end side where a large ground pressure acts during turning. For this reason, snow can be firmly pressed and solidified by the second portion during turning. Therefore, in particular, turning performance on snowy roads is improved.

  The middle inclined groove does not directly communicate with either the first main groove or the second main groove. Such a middle inclined groove prevents a decrease in rigidity of the outer middle land portion, and maintains steering stability performance.

  The outer middle lug groove connects the second portion of the first main groove and the middle inclined groove. As a result, a large axial groove component is formed in which the outer middle lug groove communicates with the second portion. Such a groove component exhibits a large snow column shear force and further improves snow road performance.

  The inner middle lug groove connects between the middle inclined groove and the second main groove. That is, the middle inclined groove communicates with the first main groove and the second main groove via the outer middle lug groove and the inner middle lug groove. Further, the middle inclined groove has a tire axial direction component and a tire circumferential direction component. As a result, snow in the middle inclined groove is effectively discharged to the first main groove and the second main groove by using the rolling and turning force of the tire, so that the snow road performance is further improved.

  The outer middle lug groove is provided at a position different from the inner middle lug groove in the tire circumferential direction. Thereby, the rigidity in the tire axial direction is ensured in a well-balanced manner in the tire circumferential direction, so that the steering stability performance is further maintained.

  Therefore, the pneumatic tire of the present invention improves snow road performance while maintaining steering stability performance.

It is an expanded view of the tread part which shows one Embodiment of this invention. It is an enlarged view of the 1st main groove of FIG. It is an enlarged view of the outer middle land part of FIG. It is an enlarged view of the outer middle land part of FIG. It is an expanded view of the tread part of other embodiment of this invention. It is an expanded view of the tread part of other embodiment of this invention. It is an expanded view of the tread part of other embodiment of this invention. 3 is a development view of a tread portion of Comparative Example 1. FIG.

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 1 showing an embodiment of the present invention. As shown in FIG. 1, a pneumatic tire (hereinafter, simply referred to as “tire”) 1 of the present embodiment is suitably used as a studless tire for a passenger car, for example.

  The tread portion 2 of the tire 1 has an asymmetric tread pattern in which the mounting direction to the vehicle is specified. The tread portion 2 has an outer tread end To positioned on the vehicle outer side when the tire 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, in characters on a sidewall (not shown).

  Each of the “tread ends” To and Ti is grounded on a flat surface at a camber angle of 0 degrees by applying a normal load to a normal tire 1 that is assembled with a normal rim and filled with a normal internal pressure. Is defined as the contact position on the outermost side in the tire axial direction. In the normal state, the distance in the tire axial direction between the tread ends To and Ti is determined as the tread contact width TW. Unless otherwise noted, the dimensions and the like of each part of the tire are values measured in a 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, ETRTO Then "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 the “maximum air pressure”, TRA is the table “TIRE LOAD LIMITS” The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO. When the tire is for a passenger car, the normal internal pressure is 180 kPa.

  “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. “JATMA” is “maximum load capacity”, TRA is “TIRE LOAD” The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO. When the tire is for a passenger car, the normal load is a load corresponding to 88% of the load.

  The tread portion 2 is provided with a plurality of main grooves extending continuously in the tire circumferential direction. The main groove of this embodiment includes a first main groove 3, a second main groove 4, and a third main groove 5.

  The first main groove 3 is disposed on the outermost tread end To side. FIG. 2 shows an enlarged view of the first main groove 3. As shown in FIG. 2, the first main grooves 3 of the present embodiment alternately include first portions 6 and second portions 7 having a larger groove width than the first portions 6. The second portion 7 has a portion protruding from the first portion 6 in the tire axial direction. The overhanging portion presses and hardens the snow and shears, thereby exerting a snow column shear force and improving snow road performance.

  The first portion 6 and the second portion 7 include a tire axial line passing through the point 3a on the outermost tread end To side of the groove edge 3e on the tire equator C side of the first main groove 3 and the tire of the first main groove 3 It is divided by the tire axial direction line passing the point 3b closest to the tire equator C of the groove edge 3i on the outer side in the axial direction. In FIG. 2, the first portion 6 and the second portion 7 are divided by virtual lines.

  The length L1 in the tire circumferential direction of the second portion 7 is 35 of one pitch of the first main groove 3 (the length L2 in the tire circumferential direction between the points 3b and 3b on the tire equator C side adjacent to the tire circumferential direction). % To 65% is desirable. When the length L1 is less than 35% or more than 65% of the length L2, the rigidity of the land portion in the vicinity of the point 3a on the outermost tread end To side and the point 3b on the most tire equator C side is There is a possibility that the steering stability performance deteriorates.

  The groove width W1a of the first portion 6 in the tire axial direction is preferably 60% to 80% of the groove width W1b of the second portion 7 in the tire axial direction. When the groove width W1a of the first portion 6 exceeds 80% of the groove width W1b of the second portion 7, the overhanging portion becomes small, and there is a possibility that the snow road performance is deteriorated. When the groove width W1a of the first portion 6 is less than 60% of the groove width W1b of the second portion 7, the rigidity of the land portion of the overhanging portion becomes small, and the steering stability performance may be deteriorated.

  The groove width W1a of the first portion 6 is preferably 2% to 10% of the tread ground contact width TW. The groove depth (not shown) of the first main groove 3 is preferably 3 to 10 mm.

  The groove edge 3e on the tire equator C side of the first main groove 3 is, for example, a first inclined portion 3A inclined with respect to the tire circumferential direction, and a second inclination having a larger angle with respect to the tire circumferential direction than the first inclined portion 3A. It has a zigzag shape in which the portions 3B are alternately arranged. Such a groove edge 3e can exert a braking force / driving force on a snowy road due to an edge component in the tire axial direction of the second inclined portion 3B.

  The first inclined portion 3A has, for example, an arc shape that is a smooth convex toward the tire equator C side. Such a first inclined portion 3A ensures a large groove volume in the protruding portion and improves the snow road performance, while maintaining the rigidity of the land portion adjacent to the first inclined portion 3A, thereby improving the steering stability performance. Suppresses the decline.

  Although not particularly limited, from the viewpoint of ensuring the rigidity of the land portion on the groove edge 3e side while effectively exerting a snow column shear force, the angle α1 of the first inclined portion 3A with respect to the tire circumferential direction is The angle is preferably 2 to 15 degrees. Moreover, the angle α2 of the second inclined portion 3B with respect to the tire circumferential direction is preferably 70 to 90 degrees. The angles α1 and α2 are angles at intermediate positions of the lengths of the inclined portions 3A and 3B.

  The groove edge 3i on the outer side in the tire axial direction of the first main groove 3 is, for example, a third inclined portion 3C inclined with respect to the tire circumferential direction, and a fourth inclination having a larger angle with respect to the tire circumferential direction than the third inclined portion 3C. It is a zigzag shape in which the portions 3D are alternately arranged.

  Such a first main groove 3 is provided on the outermost tread end To side where a large ground pressure acts during turning. For this reason, the snow can be firmly pressed and solidified by the second portion 7 during turning. Therefore, in particular, turning performance on snowy roads is improved.

  As shown in FIG. 1, the second main groove 4 is adjacent to the first main groove 3 on the inner tread end Ti side. For example, the second main groove 4 is arranged on the inner tread end Ti side with respect to the tire equator C. The second main groove 4 of the present embodiment is linear along the tire circumferential direction. Such a second main groove 4 increases the rigidity of the land portion in the vicinity of the second main groove 4.

  The third main groove 5 is disposed on the innermost tread end Ti side. The third main groove 5 extends in a sawtooth wave shape, for example. The groove edge 5i on the inner tread end Ti side of the third main groove 5 extends linearly along the tire circumferential direction. A groove edge 5e on the tire equator C side of the third main groove 5 is inclined to one side with respect to the tire circumferential direction 5A, and is inclined in the opposite direction to the one edge 5A and is more circumferential than the one edge 5A. The other edges 5B having a small length in the direction are alternately formed in the tire circumferential direction. Such a third main groove 5 also exerts a snow column shearing force.

  The groove widths W2 and W3 and the groove depth (not shown) of the second main groove 4 and the third main groove 5 in the tire axial direction can be variously determined in accordance with common practice. The groove widths W2 and W3 of the second main groove 4 and the third main groove 5 are preferably 3 to 12% of the tread ground contact width TW, for example. The groove depths of the second main groove 4 and the third main groove 5 are desirably 3 to 10 mm, for example, in the case of a passenger car tire.

  In the tread portion 2, an outer middle land portion 8, an outer shoulder land portion 9, an inner middle land portion 10, and an inner shoulder land portion 11 are divided by the main grooves 3 to 5.

  FIG. 3 is an enlarged view of the outer middle land portion 8. As shown in FIG. 3, the outer middle land portion 8 is formed between the first main groove 3 and the second main groove 4. The outer middle land portion 8 of the present embodiment is provided in the tread central region including the tire equator C.

  The outer middle land portion 8 is provided with a plurality of middle inclined grooves 12, outer middle lug grooves 13, and inner middle lug grooves 14, respectively.

  The middle inclined groove 12 is inclined with respect to the tire circumferential direction. Such a middle inclined groove 12 ensures high rigidity of the outer middle land portion 8 and maintains steering stability performance as compared with a groove having a tire radial direction component.

  The middle inclined groove 12 does not directly communicate with either the first main groove 3 or the second main groove 4. That is, both ends of the middle inclined groove 12 terminate in the middle land portion 6. Such middle inclined groove 12 ensures the rigidity of the outer middle land portion 8 to be higher.

  The middle inclined groove 12 includes a first middle inclined portion 15 and a second middle inclined portion 16 that is smaller than the groove width of the first middle inclined portion 15.

  The first middle inclined portion 15 has an inner end portion 15i on the inner tread end Ti side and an outer end portion 15o on the outer tread end To side. The groove width of the first middle inclined portion 15 gradually increases from the inner end portion 15i to the outer end portion 15o. In the first middle inclined portion 15, the inner end portion 15i is a portion having the smallest groove width, and the outer end portion 15o is a portion having the largest groove width.

  An inner end portion 15 i of the first middle inclined portion 15 is provided on the tire equator C. As a result, snow can be firmly pressed on the tire equator C on which the greatest contact pressure acts when traveling straight ahead, and a large snow column shear force is exerted to improve snow road performance.

  The outer end portion 15o of the first middle inclined portion 15 is provided at a position separated from the tire equator C. Thereby, since the 1st middle inclination part 15 has an axial direction component, it exhibits big snow column shear force.

  In order to improve the snow road performance and the steering stability performance with a good balance, the groove width W4a of the inner end portion 15i is preferably 2% to 6% of the maximum width Wa of the outer middle land portion 8 in the tire axial direction. From the same viewpoint, the groove width W4b of the outer end portion 15o is preferably 15% to 35% of the maximum width Wa of the outer middle land portion 8. In this specification, the groove width of the inclined groove and the lug groove described later is a distance between the groove edge in the direction perpendicular to the groove center line. The groove center line is a line segment that continues the midpoint (not shown) of the tire axial line that connects the groove edges on both sides. The groove depth (not shown) of the first middle inclined portion 15 is preferably 3 to 9 mm.

  The first middle inclined portion 15 has an angle θ1 with respect to the tire circumferential direction, preferably 10 to 30 degrees. When the said angle (theta) 1 is less than 10 degree | times, the tire axial direction component of the 1st middle inclination part 15 becomes small, and there exists a possibility that snowy road performance may deteriorate. When the angle θ1 exceeds 30 degrees, the inner end portion 15i or the outer end portion 15o is disposed in the vicinity of the first main groove 3 or the second main groove 4, and the rigidity of the outer middle land portion 8 in the vicinity thereof decreases. There is a fear. In this specification, the groove angle is measured at the groove centerline.

  The second middle inclined portion 16 has an outer end 16 t extending from the outer end portion 15 o of the first middle inclined portion 15 to the outer tread end To side and positioned in the outer middle land portion 8. Such a second middle inclined portion 16 has an axial component and further improves snow road performance.

  The outer end 16t of the second middle inclined portion 16 is provided on the inner side in the tire axial direction than the outer end 15t of the first middle inclined portion 15 in the tire axial direction. Thereby, the rigidity of the outer middle land portion 8 between the outer end 16t and the first main groove 3 is ensured to be high.

  The groove edge 16e on the tire equator C side of the second middle inclined portion 16 of the present embodiment is smoothly continuous with the groove edge 15e on the tire equator C side of the first middle inclined portion 15. Thereby, the rigidity of the outer middle land portion 8 is further ensured. In the present embodiment, the groove edge 16e of the second middle inclined portion 16 and the groove edge 15e of the first middle inclined portion 15 are continuous with a smooth arc.

  The second middle inclined portion 16 has a substantially constant groove width. Thereby, the rigidity of the outer middle land portion 8 in the vicinity of the second middle inclined portion 16 is further ensured to be high.

  The groove width W5 of the second middle inclined portion 16 is preferably 1% of the maximum width Wa of the outer middle land portion 8 in order to effectively compress the snow while ensuring high rigidity of the outer middle land portion 8. ~ 7%. The length L2 of the second middle inclined portion 16 in the tire circumferential direction is preferably 25% to 45% of L1 of the length of the first middle inclined portion 15 in the tire circumferential direction. The groove depth of the second middle inclined portion 16 is preferably 10% to 60% of the groove depth of the first middle inclined portion 15.

  The outer middle lug groove 13 connects the second portion 7 having a larger groove width than the first portion 6 and the middle inclined groove 12. As a result, a large axial groove component in which the outer middle lug groove 13 and the second portion 7 communicate with each other is formed. Such a groove component exhibits a large snow column shear force and further improves snow road performance. In addition, since such an outer middle lug groove 13 is provided on the outer tread end To side, the snow can be more firmly pressed and solidified by the second portion 7 and the outer middle lug groove 13 during turning, and snow road performance is further improved. Will improve. The outer middle lug groove 13 of the present embodiment joins the second portion 7 and the first middle inclined portion 15.

  FIG. 4 shows an enlarged view of the outer middle land portion 8. As shown in FIG. 4, one groove edge 13 a of the outer middle lug groove 13 is smoothly connected to the second inclined portion 3 </ b> B of the first main groove 3. Thereby, the stress concentration acting on the inner end portion of the second inclined portion 3B in the tire axial direction is relaxed, and the rigidity of the outer middle land portion 8 on the outer tread end To side is increased. In the present embodiment, one groove edge 13a of the outer middle lug groove 13 and the second inclined portion 3B form a smooth arc.

  The outer middle lug groove 13 includes a first outer middle lug groove 13A and a second outer middle lug groove 13B having a length in the tire axial direction larger than that of the first outer middle lug groove 13A, and these are alternately arranged in the tire circumferential direction. ing. Such an outer middle lug groove 13 can exert a large snow column shear force while securing the rigidity of the outer middle land portion 8.

  In the present embodiment, the other groove edge 13b of the first outer middle lug groove 13A is smoothly connected to the groove edge 15a of the outer end portion 15o of the first middle inclined portion 15. Thereby, the snow in the 1st middle inclination part 15 is discharged | emitted to the 1st main groove 3 effectively via the 1st outer side middle lug groove 13A, and a snowy road performance improves. The other groove edge 13b of the first outer middle lug groove 13A and the groove edge 15a of the outer end portion 15o of the first middle inclined portion 15 form a smooth arc.

  The second middle inclined portion 16 communicates with the second outer middle lug groove 13B. Thereby, the snow in the 2nd middle inclination part 16 is discharged | emitted smoothly to the 1st main groove 3 via the 2nd outer side middle lug groove 13B.

  The distance L3 in the tire circumferential direction between the first outer middle lug groove 13A and the second outer middle lug groove 13B is preferably 40% to 60% of one pitch P1 in the tire circumferential direction of the first outer middle lug groove 13A. is there. When the separation distance L3 is less than 40% or more than 60% of one pitch P1 of the first outer middle lug groove 13A, the rigidity balance in the tire circumferential direction of the outer portion in the tire axial direction of the outer middle land portion 8 is deteriorated. The steering stability performance may be reduced.

  The outer middle lug groove 13 extends, for example, with a substantially constant groove width. Such an outer middle lug groove 13 ensures high rigidity of the outer middle land portion 8.

  The groove width W6 of the outer middle lug groove 13 is preferably 4 to 9 mm in order to form a large snow column while ensuring the rigidity of the outer middle land portion 8. From the same viewpoint, the groove depth (not shown) of the outer middle lug groove 13 is preferably 3 to 7 mm. The angle θ2 of the outer middle lug groove 13 with respect to the tire axial direction is preferably 5 to 20 degrees.

  The inner middle lug groove 14 connects between the second main groove 4 and the middle inclined groove 12. As a result, the snow in the first middle inclined portion 15 is discharged to the second main groove 4 via the inner middle lug groove 14 using the rolling and turning force of the tire. The inner middle lug groove 14 of the present embodiment communicates with the first middle inclined portion 15.

  The inner middle lug grooves 14 of the present embodiment alternately include first inner middle lug grooves 14A and second inner middle lug grooves 14B that are longer in the tire axial direction than the first inner middle lug grooves 14A in the tire circumferential direction. Is formed.

  The inner middle lug groove 14 is provided at a position different from the outer middle lug groove 13 in the tire circumferential direction. Thereby, the rigidity in the tire axial direction is ensured in a well-balanced manner in the tire circumferential direction, so that the steering stability performance is further maintained. In the present embodiment, the projection areas in the tire axial direction of the first inner middle lug groove 14A and the second inner middle lug groove 14B overlap with the projection areas in the tire axial direction of the first outer middle lug groove 13A and the second outer middle lug groove 13B. Not.

  In order to effectively exhibit the above-described action, the shortest separation distance La in the tire circumferential direction between the inner middle lug groove 14 and the outer middle lug groove 13 is preferably 2% to 12% of the maximum width Wa of the outer middle land portion 8. %. When the shortest separation distance La exceeds 7% of the maximum width Wa of the outer middle land portion 8, snow road performance may be deteriorated.

  In the present embodiment, the inner middle lug grooves 14 and the outer middle lug grooves 13 are alternately provided along the tire circumferential direction. Thereby, the rigidity in the tire axial direction of the outer middle land portion 8 is ensured with good balance along the tire circumferential direction.

  In order to effectively exhibit the above-described action, the separation distance L4 in the tire circumferential direction between the first inner middle lug groove 14A and the second inner middle lug groove 14B is preferably between the first inner middle lug grooves 14A and 14A. It is 40% to 60% of one pitch P2 in the tire circumferential direction.

  For example, the inner middle lug groove 14 has a substantially constant groove width W7. Thereby, the rigidity of the outer middle land portion 8 is further ensured.

  The groove width W7 of the inner middle lug groove 14 is preferably 4 to 9 mm in order to form a large snow column while ensuring the rigidity of the outer middle land portion 8. From the same viewpoint, the groove depth (not shown) of the inner middle lug groove 14 is preferably 3 to 7 mm.

  An angle θ3 of the inner middle lug groove 14 with respect to the tire axial direction is larger than an angle θ2 of the outer middle lug groove 13. Thereby, the snow in the inner middle lug groove 14 arranged on the tire equator C side is smoothly discharged to the rear arrival side by rolling of the tire, and the snow in the outer middle lug groove 13 on the outer side in the tire axial direction is Using the lateral force at the time of turning, it is smoothly discharged to the first main groove 3 side. From such a viewpoint, the angle θ3 of the inner middle lug groove 14 is preferably 10 to 30 degrees.

  The middle inclined groove 12, the outer middle lug groove 13, and the inner middle lug groove 14 are inclined in the same direction (upward in FIG. 4) with respect to the tire circumferential direction. Thereby, the rigidity of the outer middle land portion 8 is further ensured.

  As shown in FIG. 1, the outer shoulder land portion 9 is disposed between the outer tread end To and the first main groove 3. The outer shoulder land portion 9 is provided with a plurality of outer shoulder lateral grooves 20 extending between the outer tread end To and the first main groove 3. Accordingly, the outer shoulder land portion 9 is formed as a block row in which outer shoulder blocks 9B divided by the outer tread end To, the first main groove 3, and the outer shoulder lateral groove 20 are arranged in the tire circumferential direction.

  The outer shoulder lateral groove 20 of the present embodiment includes an inner portion 20A disposed on the inner side in the tire axial direction, and an outer portion 20B disposed on the outer tread end To side than the inner portion 20A and having a larger groove width than the inner portion 20A. Is included. In such an outer shoulder lateral groove 20, the snow in the groove is smoothly discharged from the outer tread end To.

  The outer shoulder block 9B includes a first outer block 22A provided with a first inclined narrow groove 21A extending inward in the tire axial direction from the outer shoulder lateral groove 20 and terminating in the outer shoulder block 9B, and from the outer shoulder lateral groove 20 in the tire axial direction. Second outer blocks 22B provided with second inclined narrow grooves 21B communicating with the outer and outer tread ends To are formed alternately in the tire circumferential direction. The first inclined narrow groove 21 </ b> A and the second inclined narrow groove 21 </ b> B are smoothly connected via the outer shoulder lateral groove 20.

  The first outer block 22A is provided with a cut-out outer sipe 23A that extends from the outer tread end To inward in the tire axial direction and terminates in the first outer block 22A without communicating with the first inclined narrow groove 21A. ing.

  The second outer block 22B is provided with a notched inner sipe 23B that is disposed on the inner side in the tire axial direction than the second inclined narrow groove 21B and whose both ends are located in the second outer block 22B.

  The inner middle land portion 10 is formed between the second main groove 4 and the third main groove 5. The inner middle land portion 10 is a rib-like body in which a lateral groove that connects between the second main groove 4 and the third main groove 5 is not provided.

  The inner middle land portion 10 is provided with an inner lug groove 24 extending from the third main groove 5 to the tire equator C side and terminating in the inner middle land portion 10.

  The inner shoulder land portion 11 is formed between the third main groove 5 and the inner tread end Ti. The inner shoulder land portion 11 is provided with a plurality of inner shoulder lug grooves 26 extending in the tire axial direction and inner shoulder vertical grooves 27 extending continuously in the tire circumferential direction.

  The inner shoulder lug groove 26 of the present embodiment extends inward in the tire axial direction from the inner tread end Ti and communicates with the inner shoulder vertical groove 27. Further, the inner shoulder lug groove 26 is disposed on the outer tread end To side of the first inner portion 26A disposed on the inner side in the tire axial direction and on the outer tread end To side of the first inner portion 26A, and has a groove width larger than that of the first inner portion 26A. A large second inner portion 26B. In such an inner shoulder lug groove 26, snow in the groove is smoothly discharged from the outer tread end To.

  As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, it cannot be overemphasized that this invention can be changed into various aspects, without being limited to said specific embodiment.

A pneumatic tire of size 215 / 60R16 having the basic pattern of FIG. 1 and the patterns of FIGS. 5 to 8 was prototyped based on the specifications in Table 1, and the snow road performance and steering stability performance of each sample tire were tested. The common specifications and test methods for each sample tire are as follows. FIG. 5 is a pattern of Example 6 in which the second inclined portion and one groove edge of the outer middle lug groove are not smoothly connected. FIG. 6 is a pattern of Example 7 in which the first inclined portion has an arc shape that is a smooth convex on the vehicle outer side. FIG. 7 is a pattern of Example 8 in which the inner end portion of the first middle inclined groove is not provided on the tire equator. FIG. 8 shows a pattern of Comparative Example 1 in which the outer middle lug groove and the inner middle lug groove overlap in the tire circumferential direction.
Tread contact width TW: 166mm
Groove depth of the 1st middle slope part: 13mm
Groove depth of second middle inclined part: 14mm
Outer middle lug groove depth: 8mm
Inner middle lug groove depth: 9mm
The test method is as follows.

<Snow road performance>
Each test tire was mounted on all wheels of a passenger car with a displacement of 2400cc under the following conditions. Then, the test driver made the vehicle run on a test course on a snowy road surface, and the running characteristics regarding steering stability performance such as steering wheel stability, rigidity, traction and grip at this time were evaluated by the test driver's sensuality. The results are displayed with a score of Comparative Example 1 being 100. The larger the value, the better.
Rim (all wheels): 16 × 6.5JJ
Internal pressure (all wheels): 230kPa

<Steering stability>
The test driver ran the test vehicle on the dry asphalt road test course, and the driving characteristics at the time of turning, such as steering response and rigidity, were evaluated by the test driver's sensuality. The results are displayed with a score of Comparative Example 1 being 100. The larger the value, the better. The test results are shown in Table 1.

  As a result of the test, it can be confirmed that in the tire of the example, the snow road performance and the steering stability performance are improved in a well-balanced manner as compared with the comparative example. In addition, a test was performed on tires with different tire sizes, and the results were the same as the test results.

3 First main groove 4 Second main groove 8 Outer middle land portion 6 First portion 7 Second portion 12 Middle inclined groove 13 Outer middle lug groove 14 Inner middle lug groove

Claims (6)

A pneumatic tire having a tread portion having an outer tread end positioned on the outer side of the vehicle when the vehicle is mounted and an inner tread end positioned on the inner side of the vehicle when the vehicle is mounted by specifying the mounting direction on the vehicle. And
A first main groove extending continuously in the tire circumferential direction on the outermost tread end side, and adjacent to the first main groove on the inner tread end side and continuously extending in the tire circumferential direction on the tread portion. By providing the second main groove, an outer middle land portion is formed between the first main groove and the second main groove,
In the first main groove, first portions and second portions having a groove width larger than the first portion are alternately formed in the tire circumferential direction,
The outer middle land portion includes a plurality of middle inclined grooves that are not in direct communication with either the first main groove or the second main groove, the second portion of the first main groove, and the middle inclination. A plurality of outer middle lug grooves that connect the groove, and an inner middle lug groove that connects between the middle inclined groove and the second main groove,
The pneumatic tire is characterized in that the outer middle lug groove is provided at a position different from the inner middle lug groove in the tire circumferential direction.   The pneumatic tire according to claim 1, wherein a groove width in the tire axial direction of the first portion is 60% to 80% of a groove width in the tire axial direction of the second portion. The first main groove includes a first inclined portion in which a groove edge on the tire equator side is inclined with respect to the tire circumferential direction and a second inclined portion having a larger angle with respect to the tire circumferential direction than the first inclined portion. Zigzag arranged in the
The pneumatic tire according to claim 1, wherein the second inclined portion is smoothly connected to one groove edge of the outer middle lug groove.   The pneumatic tire according to claim 3, wherein the first inclined portion has an arc shape that is a smooth convex toward the tire equator side. The middle inclined groove is
A first middle inclined portion extending gradually from the inner end portion on the inner tread end side to the outer end portion on the outer tread end side;
5. The device according to claim 1, further comprising: a second middle inclined portion that connects between the outer end portion of the first middle inclined portion and the outer middle lug groove and has a groove width smaller than that of the first middle inclined portion. Pneumatic tire described in 2.   The pneumatic tire according to claim 5, wherein the first middle inclined portion has the inner end portion provided on a tire equator.

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