JP2018172059A - tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire capable of exhibiting superior wet performance while maintaining steering stability on a dry road surface.SOLUTION: A tire includes a tread part 2 whose direction of fitting relative to a vehicle is specified. The tread part 2 is divided into four land parts according to an outside tread end To, an inside tread end Ti, one crown main groove 3, and shoulder main grooves 4 arranged one by one on both sides respectively of the crown main groove. The land parts include two crown land parts 6 positioned on both sides of the crown main groove 3. On each of the crown land parts 6, grooves with a width of 3 mm or more are not formed, however a plurality of first crown sipes 16 and a plurality of second crown sipes 17 are formed. In each of the crown land parts 6, at least one of the second crown sipes 17 has a larger tire axial direction length than the first crown sipe 16.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tire that can exhibit excellent wet performance while maintaining steering stability on a dry road surface.

  Various so-called four land tires have been proposed in which two shoulder land portions and two crown land portions are divided into a tread portion in which the mounting direction of the vehicle is specified (for example, Patent Document 1 below). reference.). Each land portion of the tire tends to have a large width and high rigidity. Therefore, the above four land tires are expected to have excellent steering stability on dry road surfaces.

  On the other hand, it is necessary to ensure wet performance even in the case of four land tires. However, when a lateral groove is provided in the crown land portion in order to improve wet performance, the rigidity of the crown land portion is lowered, and the steering stability on the dry road surface, which is an advantage of the tire of the four land portions, is lowered. was there.

Japanese Patent Laid-Open No. 2006-013820

  The present invention has been devised in view of the above problems, and has as its main object to provide a tire that can exhibit excellent wet performance while maintaining steering stability on a dry road surface.

  The present invention is a tire having a tread portion in which the direction of mounting on a vehicle is designated, and the tread portion is positioned on an outer tread end positioned on the vehicle outer side when the vehicle is mounted and on the vehicle inner side when the vehicle is mounted. The land portion is divided into four land portions by an inner tread end, one crown main groove extending in the tire circumferential direction, and a shoulder main groove disposed on each side of the crown main groove. Including two crown land portions located on both sides of the groove, each of the crown land portions is not provided with a groove having a width of 1.5 mm or more and a depth of 2.0 mm or more. A plurality of first crown sipes having one end communicating with the main groove on the outer tread end side of the crown land portion and the other end terminating in the crown land portion having a width of less than 1.5 mm; The inner tray of the crown land A plurality of second crown sipes having a width of less than 1.5 mm, the second crown sipes being connected to the main groove on the end side and having the other end terminating in the crown land portion. At least one has a tire axial length greater than the first crown sipe.

  In the tire according to the present invention, the two crown land portions include an outer crown land portion disposed on the outer tread end side of the crown main groove, and an inner crown disposed on the inner tread end side of the crown main groove. At least one of the first crown sipes provided on the inner crown land portion and the second crown sipes provided on the outer crown land portion via the crown main groove. It is desirable to extend continuously.

  In the tire of the present invention, it is desirable that the first crown sipe and the second crown sipe overlap in the tire axial direction in the outer crown land portion.

  In the tire of the present invention, it is preferable that, in the inner crown land portion, the other end of the second crown sipe is separated from the other end of the first crown sipe in the tire axial direction.

  In the tire of the present invention, it is desirable that a shallow crown groove having a depth of less than 2 mm is provided in the inner crown land portion.

  In the tire of the present invention, it is preferable that the shallow crown groove is connected between the other end of the first crown sipe and the other end of the second crown sipe.

  In the tire according to the present invention, it is preferable that the first crown sipe and the second crown sipe are each bent.

  In the tire according to the present invention, the first crown sipe and the second crown sipe are respectively connected to the first portion extending from the one end and the first portion, and are larger than the first portion in the tire axial direction. It is desirable to include a second portion that is inclined at an angle and extends to the other end.

  In the tire of the present invention, it is desirable that one of the two crown land portions is provided with a circumferential shallow groove having a depth of less than 2.0 mm and extending continuously in the tire circumferential direction.

  The tread portion of the tire of the present invention includes an outer tread end positioned on the vehicle outer side when the vehicle is mounted, an inner tread end positioned on the vehicle inner side when the vehicle is mounted, one crown main groove extending in the tire circumferential direction, It is divided into four land portions by shoulder main grooves arranged one on each side. The land portion includes two crown land portions located on both sides of the crown main groove. Each crown land portion is not provided with a groove having a width of 1.5 mm or more and a depth of 2.0 mm or more. Each of such crown land portions has high rigidity and can maintain high steering stability on a dry road surface.

  Each crown land portion includes a plurality of first crown sipes having one end communicating with the main groove on the outer tread end side of the crown land portion and the other end terminating in the crown land portion having a width of less than 1.5 mm, and one end A plurality of second crown sipes having a width of less than 1.5 mm are provided which communicate with the main groove on the inner tread end side of the crown land portion and whose other ends terminate in the crown land portion. The first crown sipe and the second crown sipe can increase the frictional force with respect to the initial wet road surface that is slippery by the edge while maintaining the rigidity of the land portion.

  In general, tires are often attached to vehicles with a negative camber. For this reason, there is a tendency that a relatively large ground pressure acts on each crown land portion in a region on the vehicle inner side when the vehicle is mounted. In the present invention, focusing on this point, in each crown land portion, at least one of the second crown sipes communicating with the main groove on the inner tread end side has a tire axial length greater than that of the first crown sipes. Have. Thereby, since a sipe having a large length is arranged in a region where a large ground pressure acts, a large frictional force can be expected on the wet road surface.

It is an expanded view of the tread part of the tire of one embodiment of the present invention. It is an enlarged view of the outer crown land part and inner crown land part of FIG. It is the sectional view on the AA line of FIG. It is an enlarged view of the outer crown land part of FIG. It is an enlarged view of the inner crown land part of FIG. It is an enlarged view of the outer crown land part and inner crown land part of other embodiments of the present invention. It is an enlarged view of the outer side shoulder land part of FIG. It is the BB sectional view taken on the line of FIG. It is an enlarged view of the inner side shoulder land part of FIG. It is an expanded view of the tread 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 this embodiment is suitably used as a pneumatic tire for passenger cars, for example. In another embodiment of the present invention, the tire 1 can be used as, for example, a heavy-duty pneumatic tire or a non-pneumatic tire that is not filled with pressurized air inside the tire.

  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 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, each tread end To, Ti is a grounding position on the outermost side in the tire axial direction when a regular load is applied to the regular tire 1 and grounded on a plane with a camber angle of 0 °. The normal state is a state in which the tire is assembled on the normal rim and is 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. The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO.

  “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 LIMITS” The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO.

  The tread portion 2 of the present embodiment is provided with, for example, a main groove extending continuously in the tire circumferential direction. As the main groove, one crown main groove 3 and shoulder main grooves 4, 5 arranged on the both sides respectively are formed.

  The crown main groove 3 of the present embodiment is provided on the tire equator C, for example. The shoulder main grooves 4 and 5 are, for example, an outer shoulder main groove 4 disposed between the tire equator C and the outer tread end To, and an inner shoulder main disposed between the tire equator C and the inner tread end Ti. Groove 5. In a desirable mode, each of the main grooves 3 to 5 extends linearly in the tire circumferential direction.

  In the outer shoulder main groove 4 and the inner shoulder main groove 5, for example, the distance L1 from the tire equator C to the groove center line is preferably 0.20 to 0.30 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.

  The crown main groove 3, the outer shoulder main groove 4, and the inner shoulder main groove 5 preferably have, for example, groove widths W1a, W1b, and W1c that are 6 to 9% of the tread width TW. The total groove width W1a + W1b + W1c of each of the main grooves 3 to 5 is preferably 22 to 25% of the tread width TW, for example. Thereby, wet performance and steering stability are improved with good balance.

  In a more desirable mode, the groove width W1a of the crown main groove 3 is larger than the groove width W1b of the outer shoulder main groove 4. The groove width W1c of the inner shoulder main groove 5 is larger than the groove width W1a of the crown main groove 3. In other words, the groove widths of the main grooves 3 to 5 are set so as to increase toward the inner tread end Ti side. Thereby, the drainage excellent in the field between tire equator C and inner tread edge Ti can be exhibited. Further, the rigidity in the region between the tire equator C and the outer tread end To is increased, and excellent steering stability is obtained.

  The tread portion 2 is divided into two crown land portions 6 and two shoulder land portions 7 by the main grooves 3 to 5 described above. In such a four land portion tire, each land portion tends to have a large width and high rigidity. Therefore, the above four land tires are expected to have excellent steering stability on dry road surfaces.

  The crown land portion 6 of the present embodiment includes, for example, an outer crown land portion 11 and an inner crown land portion 12. The outer crown land portion 11 is divided between the crown main groove 3 and the outer shoulder main groove 4. The outer crown land portion 11 is located outside the tire equator C when the vehicle is mounted. The inner crown land portion 12 is divided between the crown main groove 3 and the inner shoulder main groove 5. The inner crown land portion 12 is positioned on the vehicle inner side of the outer crown land portion 11 when the vehicle is mounted.

  The shoulder land portion 7 of the present embodiment includes, for example, an outer shoulder land portion 13 and an inner shoulder land portion 14. The outer shoulder land portion 13 is divided on the outer side in the tire axial direction of the outer shoulder main groove 4. The inner shoulder land portion 14 is divided on the outer side in the tire axial direction of the inner shoulder main groove 5.

  FIG. 2 shows an enlarged view of the outer crown land portion 11 and the inner crown land portion 12. As shown in FIG. 2, each of the crown land portions 11 and 12 is not provided with a groove having a width of 1.5 mm or more and a depth of 2.0 mm or more. The land portion provided with the groove has a tendency to greatly decrease the rigidity. In the present invention, since the groove is eliminated, each of the crown land portions 11 and 12 has high rigidity and can maintain high steering stability on a dry road surface. In the tire according to the present embodiment, the crown land portions 11 and 12 and the main grooves 3 to 5 described above can be combined to improve the steering stability on the dry road surface and the wet performance with a good balance.

  Each crown land portion 11, 12 is provided with a first crown sipe 16 and a second crown sipe 17. In this specification, “sipe” is defined as a notch having a width of less than 1.5 mm, and the same applies to the first crown sipe 16 and the second crown sipe 17. The first crown sipe 16 has one end 16a communicating with the main groove on the outer tread end To side of the crown land portions 11 and 12, and the other end 16b terminating in the crown land portion. The second crown sipe 17 has one end 17 a communicating with the main groove on the inner tread end Ti side of the crown land portions 11, 12 and the other end terminating in the crown land portions 11, 12. Since each crown sipe 16 and 17 is terminated in the land portion, the rigidity of each land portion 11 and 12 can be maintained high. Moreover, each crown sipe 16 and 17 provides a big frictional force by the edge, for example in the initial wet road surface which began to get wet in rain. For this reason, wet performance is improved.

  FIG. 3 shows a cross-sectional view taken along line AA of the first crown sipe 16 as a diagram showing the cross-sectional shape of each crown sipe 16, 17. As shown in FIG. 3, the crown sipe 16 of the present embodiment includes an aspect extending from the bottom of the shallow groove 15 having a depth d1 of less than 2.0 mm, for example. However, the crown sipe 16 is not limited to such a form, and may extend from the tread of the land as indicated by a virtual line. The depth d2 from the tread of the land portion of the crown sipe 16 is preferably, for example, 5.0 to 7.0 mm. For example, the shallow groove 15 of the present embodiment desirably has an opening width W2 of 2.0 to 5.0 mm on the tread surface of the land.

  In general, tires are often attached to vehicles with a negative camber. For this reason, a relatively large ground pressure tends to act on each crown land portion 11, 12 in a region on the vehicle inner side when the vehicle is mounted. In the present invention, paying attention to this point, as shown in FIG. 2, in each crown land portion 11, 12, at least one of the second crown sipes 17 communicating with the main groove on the inner tread end Ti side is It has a tire axial length greater than one crown sipe 16. Thereby, since a sipe having a large length is arranged in a region where a large ground pressure acts, a large frictional force can be expected on the wet road surface.

  In order to further enhance the above-described effects, in the present embodiment, each second crown sipe 17 has a greater tire axial length than the first crown sipe 16. The first crown sipe 16 and the second crown sipe 17 are desirably provided alternately in the tire circumferential direction, for example.

  FIG. 4 shows an enlarged view of the outer crown land portion 11. As shown in FIG. 4, in the outer crown land portion 11, the first crown sipe 16 </ b> A has a length L <b> 2 that is 0.25 to 0.35 times the width W <b> 3 of the outer crown land portion 11, for example. . The second crown sipe 17A has a length L3 that is 0.70 to 0.80 times the width W3 of the outer crown land portion 11, for example.

  In the outer crown land portion 11, the ratio L2 / L3 between the length L2 of the first crown sipe 16A and the length L3 of the second crown sipe 17A is preferably 0.35 or more, more preferably 0.40 or more. , Preferably 0.55 or less, more preferably 0.50 or less. Such 1st crown sipe 16A and 2nd crown sipe 17A can improve wet performance, suppressing the excessive rigidity fall of the area | region inside the vehicle of the outer crown land part 11. FIG.

  In the outer crown land portion 11, it is desirable that the first crown sipe 16A and the second crown sipe 17A overlap in the tire axial direction. In other words, the other end 17c in the outer crown land portion 11 of the second crown sipe 17A is positioned closer to the outer tread end To than the other end 16c in the outer crown land portion 11 of the first crown sipe 16A. . The overlap width L4 in the tire axial direction between the second crown sipe 17A and the first crown sipe 16A is preferably 2.0 to 4.0% of the width W3 of the outer crown land portion 11, for example. Such an arrangement of the crown sipes 16A and 17A helps to improve the wet performance and the steering stability in a balanced manner.

  For example, the first crown sipe 16A is preferably inclined at an angle θ1 of 15 to 25 ° with respect to the tire axial direction. Similarly, it is desirable that the second crown sipe 17A is inclined at an angle θ2 of 15 to 25 ° with respect to the tire axial direction, for example. Such first crown sipe 16A and second crown sipe 17A can provide a friction force in a balanced manner in the tire circumferential direction and the tire axial direction on the initial wet road surface.

  The shallow groove 15a connected to the outer side in the tire radial direction of the second crown sipe 17A preferably includes, for example, an inner portion 26 and an outer portion 27 having different opening widths on the tread of the land portion. The inner portion 26 extends, for example, within the outer crown land portion 11 with an opening width W4. The outer portion 27 extends from the inner portion 26 to the crown main groove 3 and has an opening width W5 that is larger than the opening width W4 of the inner portion 26, for example. The ratio W4 / W5 between the opening width W4 of the inner portion 26 and the opening width W5 of the outer portion 27 is preferably, for example, 0.60 to 0.80. As a result, the inner tread end Ti side of the second crown sipe 17A is easily opened moderately, and as a result, the wet performance is enhanced.

  FIG. 5 shows an enlarged view of the inner crown land portion 12. As shown in FIG. 5, the first crown sipe 16B provided in the inner crown land portion 12 is, for example, 0.20 to 0.30 times as long as the width W6 of the inner crown land portion 12 in the tire axial direction. It is desirable to have L5. The second crown sipe 17B provided in the inner crown land portion 12 has, for example, a tire axial length L6 that is 0.45 to 0.55 times the width W6 of the inner crown land portion 12 in the tire axial direction. It is desirable.

  In the inner crown land portion 12, the ratio L5 / L6 between the length L5 of the first crown sipe 16B and the length L6 of the second crown sipe 17B is preferably 0.35 or more, more preferably 0.40 or more. , Preferably 0.55 or less, more preferably 0.50 or less. Such 1st crown sipe 16B and 2nd crown sipe 17B can improve wet performance, suppressing the excessive rigidity fall of the area | region inside the vehicle of the inner crown land part 12. FIG.

  In the inner crown land portion 12, the other end 17d in the inner crown land portion 12 of the second crown sipe 17B is separated from the other end 16d in the inner crown land portion 12 of the first crown sipe 16B in the tire axial direction. Is desirable. In other words, the other end 16d of the first crown sipe 16B is located closer to the outer tread end To than the other end 17d of the second crown sipe 17B. The separation width L7 in the tire axial direction between the other end 16d of the first crown sipe 16B and the other end 17d of the second crown sipe 17B is, for example, 0.15 to 0.30 of the width W6 of the inner crown land portion 12. It is desirable to be double. Such arrangement of the first crown sipe 16B and the second crown sipe 17B can exhibit excellent steering stability while maintaining wet performance. Further, the arrangement of the crown sipes 16B and 17B in the inner crown land portion 11 as described above, combined with the arrangement of the crown sipes 16A and 17A in the outer crown land portion 11 described above, suppresses uneven wear of each land portion. To help.

  As shown in FIG. 2, the shortest distance L9 in the tire circumferential direction between the other end 16d of the first crown sipe 16B and the other end 17d of the second crown sipe 17B in the inner crown land portion 12 is the outer crown land portion. 11 is preferably larger than the shortest distance L8 in the tire circumferential direction between the other end 16c of the first crown sipe 16A and the other end 17c of the second crown sipe 17A. The shortest distance L9 is preferably 0.50 to 0.70 times the shortest distance L8, for example. Such an arrangement of each sipe can make the outer crown land portion 11 more rigid than the inner crown land portion 12, and in particular, can improve steering stability during turning.

  At least one of the first crown sipes 16B provided in the inner crown land portion 12 is, for example, smoothly connected to the second crown sipe 17A provided in the outer crown land portion 11 via the crown main groove 3. It is desirable to extend. As a result, the second crown sipe 17A and the first crown sipe 16B can be easily opened at the time of ground contact, and the frictional force on the initial wet road surface is further increased. Note that “smoothly continuous” includes at least an aspect in which when one sipe is virtually extended along its length direction, it is continuous with the end of the other sipe.

  For example, the first crown sipe 16 and the second crown sipe 17 provided in the inner crown land portion 12 are inclined in the same direction as the first crown sipe 16 and the second crown sipe 17 provided in the outer crown land portion 11. It is desirable. As shown in FIG. 5, in the inner crown land portion 12, the angle θ3 with respect to the tire axial direction of the first crown sipe 16B and the angle θ4 with respect to the tire axial direction of the second crown sipe 17B are, for example, 15 to 25 °. It is desirable that Thereby, when the crown land portions 11 and 12 are grounded on the wet road surface, the sipes provided on the crown land portions 11 and 12 can cooperate to guide water on the road surface in one direction in the tire axial direction. Therefore, it becomes easy for the crown land portions 11 and 12 to push away water smoothly, and as a result, the wet performance is maintained.

  As shown in FIG. 5, the inner crown land portion 12 is preferably provided with a crown shallow groove 28. The shallow crown groove 28 has a depth of less than 2 mm, for example. The shallow crown groove 28 is preferably, for example, less than 3 mm in width. In a more desirable aspect, the crown shallow groove 28 connects, for example, the other end 16d of the first crown sipe 16B and the other end 17d of the second crown sipe 17B. Such a shallow crown groove 28 can improve the wet performance while maintaining the rigidity of the inner crown land portion 12.

  For example, the shallow crown groove 28 of the present embodiment is inclined in the direction opposite to the first crown sipe 16 and the second crown sipe 17 with respect to the tire axial direction. For example, the shallow crown groove 28 is preferably inclined at an angle θ5 of 60 to 80 ° with respect to the tire axial direction. Such a shallow crown groove 28 provides a large frictional force in the tire axial direction on the initial wet road surface due to its edge.

  FIG. 6 shows an example of another embodiment of the outer crown land portion 11 and the inner crown land portion 12. As shown in FIG. 6, in this embodiment, the first crown sipe 16 and the second crown sipe 17 are bent. Each such sipe can provide frictional forces in multiple directions during wet running.

  The first crown sipe 16 and the second crown sipe 17 each include, for example, a first portion 31 and a second portion 32 having different angles with respect to the tire axial direction. For example, the first portion 31 extends from the one end on the main groove side. The second portion 32 is, for example, connected to the first portion 31 and is inclined at a larger angle than the first portion 31 with respect to the tire axial direction and extends to the other end in the land portion. Each such crown sipe can enhance the apparent rigidity of the land portion when the sipe walls facing each other come into close contact with each other.

  In the shallow groove 15 in which the crown sipes 16 and 17 are continuous, for example, the opening width in the first portion 31 is preferably larger than the opening width in the second portion 32. Such a shallow groove 15 can further solidify the wet performance.

  For example, a circumferential shallow groove 33 is preferably provided in one of the two crown land portions 11 and 12. The circumferential shallow groove 33 has a depth of less than 2.0 mm. For example, the circumferential shallow groove 33 preferably has a width of less than 3 mm. In the present embodiment, a circumferential shallow groove 33 is provided in the outer crown land portion 11. The circumferential shallow groove 33 can enhance the wet performance while maintaining the rigidity of the land portion.

  FIG. 7 shows an enlarged view of the outer shoulder land portion 13. As shown in FIG. 7, the outer shoulder land portion 13 is provided with, for example, a plurality of outer shoulder lateral grooves 35 and outer shoulder sipes 36. In the present embodiment, the outer shoulder lateral grooves 35 and the outer shoulder sipes 36 are alternately provided in the tire circumferential direction.

  For example, one end of the outer shoulder lateral groove 35 communicates with the outer shoulder main groove 4. In a desirable mode, the outer shoulder lateral groove 35 extends from the outer shoulder main groove 4 to the outer tread end To, for example. It is desirable that the outer shoulder lateral groove 35 has a groove width W8 that is 0.30 to 0.50 times the groove width W1b (shown in FIG. 1) of the shoulder main groove 4, for example. Such an outer shoulder lateral groove 35 can improve the steering stability and wet performance on a dry road surface in a well-balanced manner together with the main groove and the crown land portion described above.

  It is desirable that the outer shoulder lateral groove 35 be smoothly curved and extended so that, for example, the angle θ6 with respect to the tire axial direction gradually increases toward the inner side in the tire axial direction. The angle θ6 is preferably in the range of 5 to 20 °, for example. Such outer shoulder lateral grooves 35 can smoothly guide the water in the grooves to the outer tread end To side during wet running, and can exhibit excellent wet performance.

  FIG. 8 is a cross-sectional view of the outer shoulder lateral groove 35 taken along the line BB. As shown in FIG. 8, it is desirable that the outer shoulder lateral groove 35 has a raised bottom surface, for example, at an inner end 35i in the tire axial direction. The depth d4 of the inner end portion 35i is preferably 0.50 to 0.60 times the maximum depth d3 of the outer shoulder lateral groove 35, for example. Such outer shoulder lateral grooves 35, together with the above-mentioned crown land portions 11 and 12, can further enhance the handling stability on the dry road surface.

  As shown in FIG. 1, the outer shoulder lateral groove 35 desirably extends so as to be smoothly continuous with the first crown sipe 16 </ b> A via the shoulder main groove 4, for example. Such an outer shoulder lateral groove 35 can easily open the first crown sipe 16A at the time of ground contact, and can further increase the frictional force on the initial wet road surface.

  As shown in FIG. 7, the outer shoulder sipe 36 completely crosses the outer shoulder land portion 13, for example. It is desirable that the outer shoulder sipe 36 bends smoothly so that, for example, an angle θ7 with respect to the tire axial direction gradually increases toward the inner side in the tire axial direction. The angle θ7 is preferably in the range of 5 to 20 °, for example. In a more desirable embodiment, the outer shoulder sipe 36 extends along the outer shoulder lateral groove 35. Such an outer shoulder sipe 36 can suppress distortion of the ground contact surface of the outer shoulder land portion 13 and can suppress uneven wear.

  FIG. 9 shows an enlarged view of the inner shoulder land portion 14. As shown in FIG. 9, the inner shoulder land portion 14 is provided with, for example, a plurality of inner shoulder lateral grooves 37 and inner shoulder sipes 38. In the present embodiment, the inner shoulder lateral grooves 37 and the inner shoulder sipes 38 are alternately provided in the tire circumferential direction.

  For example, the inner shoulder lateral groove 37 extends from the inner tread end Ti to the inner side in the tire axial direction and is interrupted in the inner shoulder land portion 14. The inner shoulder lateral groove 37 of the present embodiment desirably has a tire axial length L10 that is 0.75 to 0.85 times the width W7 of the inner shoulder land portion 14 in the tire axial direction. Such an inner shoulder lateral groove 37 can improve wet performance and steering stability on a dry road surface in a well-balanced manner.

  In the present embodiment, the region between the inner shoulder lateral groove 37 and the inner shoulder main groove 5 is not provided with a slit such as a sipe. Thereby, the rigidity inside the tire axial direction of the inner shoulder land portion 14 is reliably increased.

  The inner shoulder lateral groove 37 includes, for example, a first groove portion 41 and a second groove portion 42 having different angles with respect to the tire axial direction. For example, the first groove portion 41 is inclined at an angle θ8 (not shown) of 5 ° or less with respect to the tire axial direction. For example, the second groove portion 42 is bent so as to form a bent groove portion 43 between the second groove portion 42 and the first groove portion 41. The angle θ9 of the second groove portion 42 with respect to the tire axial direction is preferably 10 to 20 °, for example. As a more desirable mode, for example, each groove center line of the first groove portion 41 and the second groove portion 42 extends linearly. Such an inner shoulder lateral groove 37 can guide the water in the groove toward the inner tread end Ti side.

  The distance L11 in the tire axial direction from the inner tread end Ti to the bent groove 43 is preferably 0.40 to 0.60 times the width W7 of the inner shoulder land portion 14, for example. Thereby, the above-described effect can be obtained while suppressing uneven wear of the inner shoulder land portion 14.

  As a more desirable aspect, the second groove portion 42 has a pair of groove edges that are inclined with respect to the tire axial direction and linearly extend, and the groove width between the pair of groove edges gradually decreases inward in the tire axial direction. It is desirable. Such a second groove portion 42 can suppress uneven wear at the inner end portion of the inner shoulder lateral groove 37.

  For example, one end of the inner shoulder sipe 38 communicates with the inner shoulder main groove 5 and extends to the inner tread end Ti. As shown in FIG. 1, the inner shoulder sipe 38 extends smoothly and continuously with the second crown sipe 17 </ b> B via the inner shoulder main groove 5, for example. As a result, the inner shoulder sipe 38 and the second crown sipe 17B can be easily opened at the time of ground contact, and a larger frictional force on the initial wet road surface can be expected.

  As shown in FIG. 9, the inner shoulder sipe 38 includes, for example, a first sipe portion 45 and a second sipe portion 46 having different angles with respect to the tire axial direction. For example, the first sipe portion 45 extends at an angle θ10 (not shown) of 5 ° or less with respect to the tire axial direction. For example, the second sipe part 46 is bent so as to form a bent sipe part 47 with the first sipe part 45. For example, the second sipe portion 46 is preferably inclined at an angle θ11 of 15 to 25 ° with respect to the tire axial direction. As a more desirable aspect, each of the first sipe part 45 and the second sipe part 46 extends linearly.

  The distance L12 in the tire axial direction from the inner tread end Ti to the bent sipe portion 47 of the present embodiment is preferably 0.40 to 0.50 times the width W7 of the inner shoulder land portion 14, for example. Such a bent sipe portion 47 is useful for suppressing distortion of the ground contact surface at the center of the inner shoulder land portion 14.

  As mentioned above, although the tire of one embodiment of the present invention was explained in detail, the present invention is not limited to the above-mentioned specific embodiment, and can be carried out by changing to various modes.

A tire of size 205 / 55R16 having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1. As Comparative Example 1, as shown in FIG. 10, a tire in which the first crown sipe and the second crown sipe were formed with the same length in the tire axial direction was manufactured. Each test tire was tested for wet performance and handling stability on dry roads. The common specifications and test methods for each test tire are as follows.
Wearing rim: 16 × 6.5JJ
Tire internal pressure: 230kPa
Test vehicle: Front-wheel drive vehicle, displacement 2000 cc
Tire mounting position: All wheels The test method is as follows.

<Wet performance>
The test vehicle traveled on an initial wet road surface with a radius of 100 m (a road surface that was entirely wet with water but had no water pool formed), and the lateral acceleration (lateral G) of the front wheels was measured. The result is an average lateral G at a speed of 50 to 80 km / h, and is indicated by an index with the value of Comparative Example 1 being 100. It shows that wet performance is excellent, so that a numerical value is large.

<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 sets the comparative example 1 to 100, and shows that the steering stability on a dry road surface 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 exhibited excellent wet performance while maintaining steering stability on the dry road surface.

2 Tread portion 3 Crown main groove 4 Shoulder main groove 6 Crown land portion 16 First crown sipe 17 Second crown sipe To Outer tread end Ti Inner tread end

Claims (9)

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 on the vehicle outer side when the vehicle is mounted, an inner tread end positioned on the vehicle inner side when the vehicle is mounted, one crown main groove extending in the tire circumferential direction, and one on each side thereof. It is divided into four land parts by shoulder main grooves arranged one by one,
The land portion includes two crown land portions located on both sides of the crown main groove,
Each of the crown land portions is not provided with a groove having a width of 1.5 mm or more and a depth of 2.0 mm or more,
In each crown land portion,
A plurality of first crown sipes having one end communicating with the main groove on the outer tread end side of the crown land portion and the other end terminating in the crown land portion having a width of less than 1.5 mm;
A plurality of second crown sipes having one end communicating with the main groove on the inner tread end side of the crown land portion and the other end terminating in the crown land portion having a width of less than 1.5 mm;
In each of the crown land portions, at least one of the second crown sipe has a tire axial length greater than that of the first crown sipe. The two crown land portions include an outer crown land portion disposed on the outer tread end side of the crown main groove, and an inner crown land portion disposed on the inner tread end side of the crown main groove,
At least one of the first crown sipes provided on the inner crown land portion extends smoothly and continuously with the second crown sipes provided on the outer crown land portion via the crown main groove. The tire according to claim 1.   The tire according to claim 2, wherein in the outer crown land portion, the first crown sipe and the second crown sipe overlap in the tire axial direction.   4. The tire according to claim 2, wherein, in the inner crown land portion, the other end of the second crown sipe is separated from the other end of the first crown sipe in the tire axial direction.   The tire according to any one of claims 2 to 4, wherein a crown shallow groove having a depth of less than 2 mm is provided in the inner crown land portion.   The tire according to claim 5, wherein the crown shallow groove connects between the other end of the first crown sipe and the other end of the second crown sipe.   The tire according to claim 1, wherein each of the first crown sipe and the second crown sipe is bent.   The first crown sipe and the second crown sipe are respectively inclined at a larger angle with respect to the tire axial direction than the first portion and the first portion extending from the one end and connected to the first portion. The tire according to claim 7, further comprising a second portion extending to the other end.   The tire according to claim 7 or 8, wherein one of the two crown land portions is provided with a circumferential shallow groove having a depth of less than 2.0 mm and extending continuously in the tire circumferential direction.

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