JP2016137748A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that exerts excellent wet performance and steering stability performance.SOLUTION: In a pneumatic tire 1, a tread part 2 is provided with inclined grooves 4, extending to a tread end Te from a vicinity of a tire equator C toward a later landing side in a rotation direction N and sipes 5 communicating with the inclined grooves 4 and extending in a tire shaft direction. The inclined grooves 4 include: straight line parts 6 having angles of 10 to 30° relative to a tire circumference direction; and bent parts 7 extending to the tread end Te while gradually increasing the angels relative to the tire circumference direction. The sipes 5 include: first sipes 11 that communicate straight line parts 6 and 6 of adjacent inclined grooves 4 in the tire circumference direction with each other; and second sipes 12 that communicate the straight line part 6 of the inclined groove 4 and the bent part 7 adjacent in the tire circumference direction with each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire that can exhibit excellent wet performance and steering stability performance.

  A pneumatic tire is known in which a plurality of inclined grooves extending from the tire equator toward the rear arrival side of the tread end toward the tread end and a plurality of vertical grooves communicating between the inclined grooves are provided in the tread portion. . Such a pneumatic tire improves the wet performance because the inclined groove and the vertical groove can discharge the water film under the land portion to the outside of the tread end by using rolling of the tire.

  However, the vertical groove has a problem that the side grip force of the land portion is easily lowered, and it is difficult to improve the steering stability performance.

JP 2011-189846 A

  The present invention has been devised in view of the above problems, and is based on the improvement of the inclined grooves and sipes of the tread portion, and a pneumatic tire with improved wet performance and steering stability performance. The main purpose is to provide.

  The present invention is a pneumatic tire having a tread portion in which a rotation direction is specified, and the tread portion is provided on each side of the tire equator from the tire equator or the vicinity thereof toward the rear arrival side in the rotation direction. A plurality of inclined grooves extending to the tread end and a sipe extending in the tire axial direction so as to communicate with the inclined grooves, and each of the inclined grooves is 10 ° to 30 ° with respect to the tire circumferential direction. And a sipe that is connected to the linear portion and gradually increases the angle with respect to the tire circumferential direction and extends to the tread end, and the sipe includes the linear portions of the inclined grooves adjacent to each other in the tire circumferential direction. And a second sipe that communicates the linear portion and the curved portion of the inclined groove adjacent to each other in the tire circumferential direction.

  In the pneumatic tire according to the present invention, the tread portion is provided with a center main groove extending continuously in the tire circumferential direction on the tire equator, and each of the inclined grooves is located away from the center main groove. It is desirable to have an inner end in the tire axial direction.

  In the pneumatic tire according to the present invention, it is preferable that the first sipe extends through the inclined groove on the rear landing side among the inclined grooves adjacent in the tire circumferential direction and extends to the center main groove.

  In the pneumatic tire according to the present invention, it is preferable that the second sipe extends to the vicinity of the tire equator through the inclined groove on the rear landing side among the inclined grooves adjacent in the tire circumferential direction.

  In the pneumatic tire according to the present invention, it is preferable that the first sipe extends through the first-sided inclined groove among the inclined grooves adjacent in the tire circumferential direction and extends to the tread end.

  In the pneumatic tire according to the present invention, it is preferable that the first sipe extends in the tire axial direction from one tread end to the other tread end continuously or via another groove.

  In the pneumatic tire according to the present invention, it is preferable that the second sipe extends in the tire axial direction from one tread end to the other tread end continuously or via another groove.

  In the pneumatic tire according to the present invention, it is desirable that the inclined groove on one side of the tire equator and the inclined groove on the other side of the tire equator communicate with each other on the tire equator.

  In the pneumatic tire according to the present invention, it is desirable that the inclined groove on one side of the tire equator and the inclined groove on the other side of the tire equator are misaligned in the tire circumferential direction.

  In the pneumatic tire according to the present invention, the first sipe extends from the tread end to the inner side in the tire axial direction, and is disposed on the inner side in the tire axial direction from the first portion and is wider than the first portion. It is desirable to include a small second portion.

  The tread portion of the pneumatic tire of the present invention is provided with a plurality of inclined grooves extending from the tire equator or the vicinity thereof toward the rear arrival side in the rotational direction toward the tread end on each side of the tire equator. Such an inclined groove uses the rolling of the tire to discharge the water film below the land portion to the outside of the tread end, thereby improving the wet performance.

  Each inclined groove includes a straight portion having an angle of 10 to 30 ° with respect to the tire circumferential direction, and a curved portion extending to the tread end while being gradually increased in angle with respect to the tire circumferential direction. Such a straight portion can effectively accumulate a water film while reducing drainage resistance during straight traveling. In addition, the curved portion increases the lateral rigidity on the tread end side of the land portion, so that the steering stability performance is improved.

  When running straight ahead, a large contact pressure acts on the land on the tire equator side. Further, during turning, a large lateral force acts on the land portion on the tread end side. For this reason, the water in the inclined groove is effectively discharged from the straight portion and the curved portion during straight traveling and turning traveling on a wet road surface. Accordingly, the wet performance is further improved.

  In addition, sipes extending along the tire axial direction are provided on each side of the tire equator so as to communicate with the inclined grooves. Such a sipe increases the ground contact property (grip force) with the road surface by generating the deflection of the land portion, and thus improves the steering stability performance.

  The sipe includes a first sipe that communicates linear portions of the inclined grooves adjacent in the tire circumferential direction and a second sipe that communicates the linear portion and the curved portion of the inclined grooves adjacent in the tire circumferential direction. That is, since the sipes are spaced apart in the tire circumferential direction, the deflection of the land portion is generated over the tire circumferential direction. For this reason, since the ground contact property between the land portion and the road surface is further improved, the steering stability performance is further improved.

  The second sipe that communicates the straight portion and the curved portion is longer in the tire axial direction than the first sipe that communicates the straight portions. For this reason, the second sipe can generate a larger deflection. Moreover, since the 2nd sipe is connecting the curved part, it is provided in a tire axial direction outer side rather than a 1st sipe. Thereby, since the grip force of the tire axial direction outer side part of a land part is raised more, steering stability performance improves further.

  Therefore, in the pneumatic tire of the present invention, the sipe including the inclined groove including the linear portion and the curved portion, the first sipe that communicates the linear portions, and the second sipe that communicates the linear portion and the curved portion. By providing, it is possible to exhibit excellent wet performance and steering stability performance.

It is an expanded view of the tread part of the pneumatic tire of a 1st embodiment of the present invention. It is an expanded view of the tread part of the pneumatic tire of a 1st embodiment of the present invention. It is an expanded view of the tread part of the pneumatic tire of 2nd Embodiment of this invention. It is an expanded view of the tread part of the pneumatic tire of 3rd Embodiment of this invention. It is an expanded view of the tread part of the pneumatic tire of 4th Embodiment of this invention. It is an expanded view of the tread part of the pneumatic tire of 5th Embodiment of this invention. It is an expanded view of the tread part of the pneumatic tire of 6th Embodiment of this invention. It is an expanded view of the tread part of the pneumatic tire of a comparative example. It is an expanded view of the tread part of the pneumatic tire of another comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of the tread portion 2 of the pneumatic tire 1 according to the first embodiment of the present invention. The pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment is suitably used for, for example, a four-wheel racing cart. In the tire 1, the rotation direction N is designated. The rotation direction N is displayed by, for example, characters or symbols on a sidewall portion (not shown).

  In the tread portion 2 of the tire 1 of the present embodiment, one main groove 3, a plurality of inclined grooves 4 provided on each side of the tire equator C, and a plurality of inclined grooves 4 communicating with each inclined groove 4. A sipe 5 is provided.

  The main groove 3 of this embodiment extends continuously on the tire equator C in the tire circumferential direction. Such a main groove 3 effectively drains a water film in a land portion in the vicinity of the tire equator C, which is most difficult to drain, thereby improving wet performance.

  The main groove 3 extends linearly. Such a main groove 3 increases the rigidity of the land portion in the vicinity of the main groove 3, suppresses unstable behavior such as vehicle wobbling and one-way flow during braking, and improves steering stability performance. The shape of the main groove 3 is not limited to a linear shape, and may be, for example, a zigzag shape or a wave shape.

  The inclined groove 4 of the present embodiment extends from the vicinity of the tire equator C toward the rear arrival side in the rotational direction N to the tread end Te. Such an inclined groove 4 uses the rolling of the tire to discharge the water film below the land portion to the outside of the tread end Te, thereby improving the wet performance.

  The “tread end” Te is a normal load applied by applying a normal load to a tire in a normal state in which a rim is assembled on a normal rim and filled with a normal internal pressure, and a normal load is applied to a flat surface with a camber angle of 0 degrees. It is determined as a contact position on the outermost side in the tire axial direction in the state. In the normal state, the distance in the tire axial direction between the tread ends Te and Te 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 this 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". If ETRTO, "INFLATION PRESSURE". When the tire is for a passenger car, the normal internal pressure is 180 kPa. When the tire is used for a racing cart, the normal internal pressure is 100 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 load corresponds to 88% of the load. When the tire is for a racing cart, the normal load is 392N.

  In the present embodiment, the inclined groove 4 has an inner end 4 e in the tire axial direction that terminates without communicating with the main groove 3. Since such an inclined groove 4 suppresses a decrease in rigidity of the land portion in the vicinity of the main groove 3, the steering stability performance and the wear resistance performance are maintained high. In addition, when the tire axial direction distance La of the inner end 4e of the inclined groove 4 and the main groove 3 is large, there exists a possibility that wet performance may deteriorate. For this reason, the tire axial direction distance La is preferably 5% to 10% of the tread contact width TW.

  Each inclined groove 4 includes a straight portion 6 that extends linearly and a curved portion 7 that continues to the straight portion 6 and extends to the tread end Te. When traveling straight ahead, a large contact pressure acts on the land on the tire equator C side. Further, during turning, a large lateral force acts on the land portion on the tread end Te side. For this reason, the water in the inclined groove 4 is effectively discharged from the straight portion 6 and the curved portion 7 during straight traveling and turning traveling on a wet road surface. Accordingly, the wet performance is further improved.

  The straight portion 6 has an angle θ1 of 10 to 30 ° with respect to the tire circumferential direction. When the angle θ1 of the straight portion 6 is less than 10 degrees, the water film under the land portion cannot be effectively accumulated over the tire axial direction, and the wet performance cannot be improved. When the angle θ1 of the straight portion 6 exceeds 30 degrees, the drainage resistance of the straight portion 6 becomes large during straight traveling, and the wet performance cannot be improved.

  For example, the straight portion 6 extends with a certain width. Since such a straight part 6 maintains the rigidity of the land part in the vicinity of the straight part 6 high, it exhibits excellent steering stability performance and wear resistance performance. The straight line portion 6 is not limited to such a mode, and may be a mode in which the groove width gradually increases toward the tread end Te, for example.

  The curved portion 7 extends to the tread end Te while gradually increasing the angle θ2 with respect to the tire circumferential direction. Such a curved portion 7 increases the lateral rigidity of the land portion on the tread end Te side, and thus improves the steering stability performance. In addition, the bending portion 7 reduces the tire axial direction rigidity step of the land portion in the vicinity of the bending portion 7, thereby improving wear resistance performance and steering stability performance.

  From the viewpoint of effectively exhibiting the above-described action, the angle θ2 of the curved portion 7 with respect to the tire circumferential direction is preferably 60 degrees or more, more preferably 70 degrees or more on the tread end Te.

  The curved portion 7 and the straight portion 6 are smoothly connected. Thereby, the rigidity step of the land part near the connection part of the curved part 7 and the linear part 6 is maintained small, and wear resistance performance and steering stability performance improve. “Smooth connection” refers to an aspect in which the groove center line 7c of the curved portion 7 and the groove center line 6c of the straight portion 6 are connected without intersecting.

  In the present embodiment, the inclined groove 4A on one side (right side in FIG. 1) of the tire equator C and the inclined groove 4B on the other side (left side in FIG. 1) of the tire equator C are displaced in the tire circumferential direction. Yes. Thereby, since the rigidity step in the tire axial direction is reduced over the tire circumferential direction, steering stability performance and wear resistance performance are improved. In order to exhibit such an action more effectively, it is desirable that the inclined groove 4A on one side and the inclined groove 4B on the other side are shifted by a half pitch in the tire circumferential direction.

  In order to improve the steering stability performance and the wet performance with a good balance, the groove width W1 of the main groove 3 and the groove width W2 of the inclined groove 4 are preferably 4% to 15% of the tread ground contact width TW, more preferably, It is 6% to 10% of the tread ground contact width TW. The groove depth (not shown) of the main groove 3 and the inclined groove 4 is about 4 to 10 mm.

  In the present embodiment, the sipe 5 extends along the tire axial direction. Such a sipe 5 maintains a high rigidity in the tire axial direction of the land portion in the vicinity of the sipe 5, and thus generates a large side grip. Further, since the sipe 5 generates a deflection of the land portion and improves the ground contact property (grip force) with the road surface, the steering stability performance is further improved. In order to effectively exhibit such an action, the angle θ3 of the sipe 5 with respect to the tire axial direction is preferably 5 degrees or less, and more preferably 0 degrees.

  The sipe 5 extends linearly. Such a sipe 5 maintains the tire axial rigidity of the land portion in the vicinity of the sipe 5 even higher. Note that the sipe 5 is not limited to such an embodiment, and may be wavy or zigzag.

  The sipe 5 includes a first sipe 11 that connects the straight portions 6 and 6 of the inclined grooves 4 and 4 adjacent in the tire circumferential direction, and a straight portion 6 and the curved portion 7 of the inclined grooves 4 and 4 adjacent in the tire circumferential direction. And a second sipe 12 that communicates with each other. Since the sipe 5 is spaced apart in the tire circumferential direction, the pitch of deflection of the land portion is reduced. For this reason, since the ground contact property between the land portion and the road surface is further enhanced, the steering stability performance is further improved.

  Moreover, the 2nd sipe 12 which connects the linear part 6 and the curved part 7 has the length of a tire axial direction larger than the 1st sipe 11 which connects the linear parts 6 and 6 mutually. For this reason, the second sipe 12 can generate a larger deflection than the first sipe 11. Further, since the curved portion 7 is communicated, a small tire axial rigidity step near the second sipe 12 is ensured. Thereby, since the grip force of the tire axial direction outer side part of a land part is raised more, steering stability performance improves further.

  The first sipe 11 of the present embodiment includes a first middle portion 15, a first center portion 16 disposed on the inner side in the tire axial direction than the first middle portion 15, and an outer side in the tire axial direction from the first middle portion 15. And a first shoulder portion 17 disposed on the first shoulder portion 17.

  In the present embodiment, the first middle portion 15 continues the straight portions 6 and 6 of the inclined grooves 4 and 4 adjacent in the tire circumferential direction. In the present embodiment, the first center portion 16 joins the main groove 3 and the straight portion 6 and is smoothly connected to the first middle portion 15 via the straight portion 6. In the present embodiment, the first shoulder portion 17 joins the tread end Te and the straight portion 6 and is smoothly connected to the first middle portion 15 via the straight portion 6.

  In this way, the first sipe 11 extends between the main groove 3 and the tread end Te via the inclined grooves 4 and 4 adjacent in the tire circumferential direction. As a result, the first middle portion 15, the first center portion 16, and the first shoulder portion 17 are bent at the same time, so that the ground contact with the road surface is further improved by the resonance effect of these deflections. The “smooth connection” means that a virtual center line 15 e obtained by extending the width center line 15 c of the first middle portion 15 in the tire axial direction is provided in the first center portion 16 or the first shoulder portion 17. Refers to an embodiment.

  In the present embodiment, the length L1 of the first middle portion 15 in the tire axial direction is larger than the length L2 of the first center portion 16 in the tire axial direction. Further, the length L1 of the first middle portion 15 is smaller than the length L3 of the first shoulder portion 17 in the tire axial direction. That is, in this embodiment, the length of the sipe arranged on the outer side in the tire axial direction is larger than the length of the sipe arranged on the inner side in the tire axial direction. Thereby, since the deflection of the outer portion in the tire axial direction of the land portion can be generated more than the inner portion in the tire axial direction of the land portion, the steering stability performance can be improved particularly. In addition, when the length L3 of the first shoulder portion 17 is excessively large, there is a possibility that the inner portion of the tread portion 2 in the tire axial direction cannot be effectively deflected. From this point of view, the length L2 of the first center portion 16 is preferably 60% to 90% of the length L1 of the first middle portion 15. The length L1 of the first middle portion 15 is preferably 50% to 80% of the length L3 of the first shoulder portion 17.

  As shown in FIG. 2, in the present embodiment, the first sipe 11 includes a first portion 18 and a second portion 19 having a smaller width than the first portion 18. The first portion 18 of the present embodiment extends inward in the tire axial direction from the tread end Te. Such a first portion 18 increases the deflection of the outer portion of the land portion in the tire axial direction, thereby enhancing the grip force.

  The first sipe 11 has a first sipe 11A on one side of the tire equator C and a first sipe 11B on the other side of the tire equator C. In the present embodiment, the first sipe 11A on one side and the first sipe 11B on the other side are from one tread end Te to the other tread end Te via the main groove 3 and the inclined grooves 4A and 4B on both sides. It is extended. Since such a 1st sipe 11 generate | occur | produces a deflection with a road surface in the inside and outside of a tire axial direction, ground contact property improves further. The first sipe 11A on one side and the first sipe 11B on the other side of the present embodiment are displaced in the tire circumferential direction.

  When the width W3 of the first portion 18 is excessively large, the rigidity of the land portion in the vicinity of the tread end Te is lowered, and the steering stability performance may be deteriorated. For this reason, the width W3 of the first portion 18 is preferably 2% or more of the tread ground contact width TW, more preferably 2.5% or more of the tread ground contact width TW, and preferably less than 5% of the tread ground contact width TW. More preferably, it is less than 4.0% of the tread ground contact width TW. From the same viewpoint, the length L4 of the first portion 18 in the tire axial direction is preferably smaller than the length L3 of the first shoulder portion 17, and more preferably 3% to 8% of the tread ground contact width TW. %. Further, the depth of the first portion 18 is preferably 65% to 100% of the groove depth of the main groove 3. The width W4 of the second portion 19 is preferably 25% to 90% of the width W3 of the first portion 18.

  The second sipe 12 includes a second shoulder portion 20 and a second center portion 21 disposed on the inner side in the tire axial direction than the second shoulder portion 20. The second shoulder portion 20 continues the straight portion 6 and the curved portion 7 of the inclined grooves 4 and 4 adjacent in the tire circumferential direction. The second center portion 21 joins the main groove 3 and the straight portion 6 and is smoothly connected to the second shoulder portion 20 via the straight portion 6. The “smooth connection” refers to an aspect in which a virtual center line 20 e obtained by extending the width center line 20 c of the second shoulder portion 20 inward and outward in the tire axial direction is provided in the second center portion 21.

  The second sipe 12 is formed with an equal width. This is because the second shoulder portion 20 is connected to the curved portion 7 having a width wider than that of the sipe 5. For this reason, since the 2nd sipe 12 suppresses the excessive rigidity fall by the tread end Te side of a land part, it is not necessary to provide the wide 1st part 18 like the 1st sipe 11. FIG.

  The length L5 of the second shoulder portion 20 in the tire axial direction is larger than the length L6 of the second center portion 21 in the tire axial direction. As a result, the length of the sipe disposed on the outer side in the tire axial direction is larger than the length of the sipe disposed on the inner side in the tire axial direction, so that a large deflection of the outer portion in the tire axial direction of the tread portion 2 is generated. Can do. The length L5 of the second center portion 21 in the tire axial direction is preferably 85% to 97% of the length L4 of the second shoulder portion 20 in the tire axial direction.

  The second sipe 12 has a second sipe 12A on one side of the tire equator C and a second sipe 12B on the other side of the tire equator C. In the present embodiment, the second sipe 12A on one side and the first sipe 11B on the other side are provided on the tire equator C at the same position in the tire circumferential direction. The second sipe 12B on the other side and the first sipe 11A on the one side are provided at the same position in the tire circumferential direction on the tire equator C. Thereby, the tire axial direction rigidity of the land part in the vicinity of the sipe 5 is equalized over the tire circumferential direction.

  Although not particularly limited, the width W5 of the second sipe 12 is preferably 1% or more of the tread ground width TW, less than 5% of the tread ground width TW, and more preferably, the tread ground width TW. It is less than 4.0%. The depth (not shown) of the second sipe 12 is preferably 50% to 100% of the groove depth of the main groove 3.

  By such a main groove 3, the inclined groove 4, and the sipe 5, the tread portion 2 has a center block-like portion 23, a middle block-like portion 24 disposed on the outer side in the tire axial direction than the center block-like portion 23, and The shoulder block-like portion 25 is arranged on the outer side in the tire axial direction than the middle block-like portion 24.

  The center block-shaped part 23 communicates with the linear part 6 of the inclined groove 4, the main groove 3, the first center part 16 communicating with the linear part 6, and the linear part 6 on the rear arrival side of the linear part 6. 1 center part 16 and 1st middle part 15 are divided. The center block-shaped portion 23 of the present embodiment has a substantially trapezoidal shape in which the width Wa in the tire axial direction gradually increases toward the rear arrival side in the rotation direction N. Since the center block-like portion 23 is easily deformed when the block-like portion is stepped on or kicked out, the ground contact with the road surface is improved.

  The middle block-shaped portion 24 is divided into inclined grooves 4 and 4 adjacent to each other in the tire circumferential direction, a second shoulder portion 20 and a first middle portion 15. The middle block-like portion 24 of the present embodiment has a substantially trapezoidal shape in which the width Wb in the tire axial direction gradually increases toward the rear arrival side in the rotation direction N. Such a middle block-shaped part 24 can exhibit the same effect as the above-described center block-shaped part 23.

  Thus, the center block-like portion 23 and the middle block-like portion 24 provided on the inner side in the tire axial direction on which a large contact pressure acts during straight traveling, the width in the tire axial direction is large on the rear arrival side in the rotational direction N. Is done. Thereby, in the land part inside a tire axial direction, the ground contact property with a road surface can be improved effectively, and steering stability performance improves.

  The width Wb in the tire axial direction of the middle block portion 24 is preferably 5% to 20% of the tread ground contact width TW, and more preferably 8% to 15% of the tread ground contact width TW. If the width Wb of the middle block-shaped portion 24 is small, the rigidity in the tire axial direction of the middle block-shaped portion 24 may be reduced, and the lateral grip may be reduced. When the width Wb of the middle block-shaped part 24 is large, the groove width of the inclined groove 4 becomes small, and the wet performance may be deteriorated.

  The shoulder block-like portion 25 is divided into inclined grooves 4 and 4 adjacent to each other in the tire circumferential direction, a tread end Te, and a second shoulder portion 20. The shoulder block-like portion 25 of the present embodiment has a tire circumferential direction length Lc that gradually increases outward in the tire axial direction. Since such a shoulder block-like portion 25 has a tire circumferential rigidity that increases toward the tread end Te, the deformation of the curved portion 7 due to the contact pressure is suppressed, and the groove width is maintained large. For this reason, the outstanding wet performance is exhibited.

  Further, the tread portion 2 of the tire 1 of the present embodiment is not provided with grooves except for the main groove 3 and the inclined groove 4. For this reason, the big rigidity fall of the tread part 2 is suppressed. Further, by providing a sipe 5 that communicates between the inclined grooves 4 and 4 and extends along the tire axial direction, the main groove 3, the inclined groove 4, And a deflection | deviation can be generated in the land part enclosed by the sipe 5. FIG. Thereby, the ground contact property between the land portion and the road surface is enhanced, and the steering stability performance is improved. In the present specification, the groove is a cut having a groove width of 4.0% or more of the tread grounding width TW, and the sipe is a cut having a width of less than 4.0% of the tread grounding width TW.

  The tread portion 2 is divided into a pair of shoulder regions Sh and Sh, a pair of middle regions Mi and Mi disposed on the inner side in the tire axial direction of the shoulder region Sh, and a center region Ce disposed between the middle regions Mi and Mi. Is done. The shoulder region Sh is a region that is 1/6 of the tread contact width TW from the tread end Te to the inside in the tire axial direction. The middle region Mi is a region of 1/6 of the tread contact width TW from the inner end in the tire axial direction of each shoulder region to the inner side in the tire axial direction.

  In such shoulder region Sh, middle region Mi, and center region Ce, the land ratio of the shoulder region Sh is larger than the land ratio of the middle region Mi, and the land ratio of the middle region Mi is the land ratio of the center region Ce. Is desirable. That is, during cornering, a larger lateral force acts on the land portion on the outer side in the tire axial direction than on the land portion on the inner side in the tire axial direction. For this reason, the steering stability performance is improved by improving the land ratio of each region as described above.

  The land ratio of the shoulder region Sh is preferably 50% to 90% in order to improve the stable performance of turning and straight traveling on a wet road surface with a good balance. The land ratio of the middle region Mi is preferably 45% to 80%. The land ratio of the center region Ce is preferably 30% to 70%. The land ratio of each region is a ratio (Mb / Ma) between the total surface area Mb of the tread surface of each region and the virtual surface area Ma of the virtual tread surface obtained by filling all the grooves and sipes provided in each region.

  FIG. 3 is a development view of the tread portion 2 of the second embodiment. The description of the same configuration as that shown in FIG. 1 is omitted. In the second embodiment, the inclined groove 4A on one side of the tire equator C and the inclined groove 4B on the other side of the tire equator C are not displaced in the tire circumferential direction. Such an inclined groove 4 makes the tire axial rigidity of the tread portions 2 on both sides sandwiching the tire equator C uniform over the tire circumferential direction, so that, in particular, the straight running stability performance on a wet road surface is improved.

  In the second embodiment, the first middle portion 15 and the first shoulder portion 17 of the first sipe 11 are displaced in the tire circumferential direction. Thereby, since the tire axial direction rigidity level | step difference over the tire peripheral direction of a land part approaches uniformly, abrasion resistance performance improves. Note that “the first middle portion 15 and the first shoulder portion 17 of the first sipe 11 are displaced in the tire circumferential direction” means a virtual center line 15e of the first middle portion 15 (shown in FIG. 1). However, the aspect which is not provided in the 1st shoulder part 17 is said.

  In the second embodiment, the second shoulder portion 20 and the second center portion 21 of the second sipe 12 are displaced in the tire circumferential direction. Thereby, the above-mentioned operation is effectively exhibited.

  FIG. 4 is a development view of the tread portion 2 of the third embodiment. The description of the same configuration as that shown in FIG. 1 is omitted. In the third embodiment, the inclined groove 4A on one side of the tire equator C and the inclined groove 4B on the other side of the tire equator C communicate with each other on the tire equator C without being displaced in the tire circumferential direction. That is, both the inclined grooves 4A and 4B form one groove that connects one tread end Te and the other tread end Te. Such an inclined groove 4 also discharges a water film on the tire equator C to the tread end Te side.

  In the tread portion 2 of the third embodiment, the main groove 3 extending on the tire equator C is not provided. For this reason, during straight running, the rigidity of the land portion on the tire equator C on which a large contact pressure acts is ensured, so that the straight running stability performance particularly on wet road surfaces is improved.

  In the tread portion 2 of the third embodiment, the first sipe 11 includes a first first arrival portion 11S on the first arrival side in the rotation direction N and a first rear arrival portion 11T on the rear arrival side with respect to the first first arrival portion 11S. It is out. Such a tread portion 2 further generates a deflection of the land portion.

  11 S of 1st first arrival parts are formed from the front middle part 30A which joins the linear parts 6 and 6 of the inclination groove | channel 4, and the front shoulder part 30B distribute | arranged to the tire axial direction outer side rather than the front middle part 30A. The front middle portion 30 </ b> A and the front shoulder portion 30 </ b> B are smoothly connected via the inclined groove 4.

  The first rear attachment portion 11T is formed of a rear middle portion 31A that joins the straight portions 6 and 6 of the inclined groove 4 and a rear center portion 31B that is arranged on the inner side in the tire axial direction than the rear middle portion 31A. . The rear center portion 31B connects between the straight portions 6 and 6 of the inclined grooves 4 on both sides of the tire equator C, and is smoothly connected via the rear middle portions 31A and the straight portions 6 on both sides. Such a rear center portion 31B increases the deflection of the land portion on the tire equator C on which a large contact pressure acts, and thus improves the contact property with the road surface.

  FIG. 5 is a development view of the tread portion 2 of the fourth embodiment. The description of the same configuration as that shown in FIG. 1 is omitted. In the fourth embodiment, a third center sipe 35 that connects the main groove 3 and the inclined groove 4 is provided between the first center portion 16 of the first sipe 11 and the second center portion 21 of the second sipe 12. ing. Such a third center sipe 35 further generates deflection in the land portion, so that the steering stability performance is improved.

  In the tread portion 2 of the fourth embodiment, the first sipe 11, the second sipe 12, and the third center sipe 35 on each side of the tire equator C are displaced in the tire circumferential direction. Thereby, the tire axial direction rigidity of the tread portion 2 approaches uniformly in the tire circumferential direction.

  FIG. 6 is a development view of the tread portion 2 of the fifth embodiment. The description of the same configuration as that shown in FIG. 1 is omitted. In this aspect, the first sipe 11 includes only the first middle portion 15 and the first center portion 16. Further, the second sipe 12 is composed of only the second shoulder portion 20. Since such a tread portion 2 maintains the rigidity of the land portion on the inner side in the tire axial direction, the straight running stability performance on a wet road surface is improved.

  In the tread portion 2 of the fifth embodiment, a plurality of arc grooves 37 extending in an arc shape from the tread end Te inward in the tire axial direction toward the first arrival side in the rotation direction N and terminating without communicating with other grooves or sipes. Is provided. Such an arc groove 37 improves wet performance.

  FIG. 7 is a development view of the tread portion 2 of the sixth embodiment. The description of the same configuration as that shown in FIG. 1 is omitted. In the sixth embodiment, the second sipe 12 includes a second first sipe 39 provided on the first arrival side in the rotational direction N, and a second rear sipe 41 provided on the rear arrival side relative to the second first sipe 39. Yes. The second tip sipe 39 includes a second tip shoulder portion 39A that joins the curved portion 7 and the straight portion 6, and a second tip center portion 39B that is provided on the inner side in the tire axial direction than the second tip shoulder portion 39A. ing. The second rear sipe 41 includes a second rear shoulder portion 41A that joins the curved portion 7 and the straight portion 6, and a second rear center portion 41B that is provided on the inner side in the tire axial direction than the second rear shoulder portion 41A. ing. Also in the sixth embodiment, a large amount of deflection with the road surface can be generated, so that the steering stability performance is further improved.

  In the sixth embodiment, a sub-groove having a large groove width extending in parallel with the tire axial direction is provided on the outer side in the tire axial direction of the first sipe 11. Such sub-grooves improve wet performance.

  As mentioned above, although embodiment of this invention was explained in full detail, it cannot be overemphasized that this invention is not limited to illustrated embodiment, and can be deform | transformed and implemented in a various aspect.

Tires for a four-wheel racing cart having the basic pattern shown in FIG. 1 were prototyped based on the specifications in Table 1 and tested for wet grip performance, steering stability performance, and wear resistance performance. The main common specifications and test methods for each sample tire are as follows.
Tread contact width TW: 85mm (front wheel), 105mm (rear wheel)
Groove depth of main and inclined grooves: 5.0mm
Width W4 of the second portion and width W5 of the second sipe: 2% (ratio to the tread ground contact width TW)
Angle θ2 on the tread end Te of the curved portion: 70 degrees

<Wet grip performance>
Each test tire is mounted on all wheels of a 100cc four-wheel racing cart with the following conditions, and a test driver runs the racing cart on a wet asphalt road test course with a water depth of 5 mm. The driving characteristics related to grip force were evaluated by the test driver's sensuality. The result is indicated by a score of 5 for the tire of Example 1 and 1 for the tire of Comparative Example 3. The larger the value, the better.
<Front wheel>
Size: 10x4.50-5
Rims: 4.5
Internal pressure: 100kPa
<Rear wheel>
Size: 11x6.50-5
Rims: 6.5
Internal pressure: 100kPa

<Running time (steering stability performance)>
A test driver ran the racing cart on the dry asphalt road test track for 7 laps for 1 lap. The results are displayed by a five-point method in which the running time is scored by the following evaluation method. The larger the value, the better.
1: Fastest time + 2.5 seconds or more 2: Fastest time + 1.5 seconds or more, less than 2.5 seconds 3: Fastest time + 0.5 seconds or more, less than 1.5 seconds 4: Fastest time + 0.1 seconds or more, 0 Less than 5 seconds 5: Fastest time + less than 0.1 seconds

<Abrasion resistance>
After the time trial described above, the test driver observed the wrinkle-like wear (abrasion wear) on the surface of the tread portion. The results are displayed by a five-point method in which the wear state is scored by the following evaluation method. The larger the value, the better.
1: Serious abrasion wear occurred.
2: Moderate abrasion wear occurred.
3: Mild abrasion wear occurred.
4: Signs of abrasion wear were observed.
5: No abrasion wear occurred.
The test results are shown in Table 1.

  As a result of the test, it can be understood that the tire of the example has improved wet performance and steering stability performance in a well-balanced manner as compared with the tire of the comparative example. In addition, the same test was carried out by changing the tire size, but showed the same tendency as the test result.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 4 Inclined groove 5 Sipe 6 Straight part 7 Curved part 11 1st sipe 12 2nd sipe N Rotation direction Te Tread end

Claims (10)

A pneumatic tire having a tread portion with a specified rotation direction,
The tread portion includes a plurality of inclined grooves extending from the tire equator or the vicinity thereof toward the rear arrival side in the rotational direction toward the tread end on each side of the tire equator, and a tire shaft communicating with the inclined grooves. There is a sipe extending along the direction,
Each of the inclined grooves includes a straight portion having an angle of 10 to 30 ° with respect to the tire circumferential direction, and a curved portion extending to the tread end while gradually increasing the angle with respect to the tire circumferential direction.
The sipe is
A first sipe that communicates the linear portions of the inclined grooves adjacent in the tire circumferential direction;
A pneumatic tire comprising: a second sipe that communicates the linear portion and the curved portion of the inclined grooves adjacent in the tire circumferential direction. The tread portion is provided with a center main groove extending continuously in the tire circumferential direction on the tire equator,
The pneumatic tire according to claim 1, wherein each of the inclined grooves has an inner end in a tire axial direction at a position away from the center main groove.   The pneumatic tire according to claim 2, wherein the first sipe extends through the inclined groove on the rear arrival side among the inclined grooves adjacent in the tire circumferential direction and extends to the center main groove.   4. The pneumatic tire according to claim 2, wherein the second sipe extends through the inclined groove on the rear arrival side among the inclined grooves adjacent in the tire circumferential direction and extends to the vicinity of the tire equator.   5. The pneumatic tire according to claim 1, wherein the first sipe extends through a first-sided inclined groove among the inclined grooves adjacent in the tire circumferential direction and extends to a tread end.   The pneumatic tire according to any one of claims 1 to 5, wherein the first sipe extends in a tire axial direction continuously from one tread end to the other tread end through another groove.   The pneumatic tire according to claim 1, wherein the second sipe extends in the tire axial direction from one tread end to the other tread end continuously or via another groove.   The pneumatic tire according to claim 1, wherein the inclined groove on one side of the tire equator and the inclined groove on the other side of the tire equator communicate with each other on the tire equator.   The pneumatic tire according to any one of claims 1 to 7, wherein the inclined groove on one side of the tire equator and the inclined groove on the other side of the tire equator are displaced in the tire circumferential direction. The first sipe includes a first portion extending inward in the tire axial direction from a tread end, and a second portion disposed on the inner side in the tire axial direction than the first portion and having a smaller width than the first portion. The pneumatic tire according to any one of 1 to 9.

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