JP4763260B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having improved pattern noise, uneven wear resistance, and handling stability without sacrificing wet performance in a pneumatic tire for summer.

  As a pneumatic tire for summer, a block pattern in which straight main grooves and inclined grooves extending in the tire circumferential direction are generally used (see, for example, Patent Document 1).

  In order to improve the wet hydroplaning property, a method of increasing the groove area (negative) such as increasing the groove width is generally used.

  For the purpose of improving steering stability and the like, a method has been proposed in which the negative rate is changed in each tread area outside, inside and inside the tread with an asymmetric pattern (see, for example, Patent Document 2).

For the purpose of reducing air column resonance, a method has been proposed in which the width of the circumferential main groove is varied to reduce noise (for example, see Patent Document 3).
Further, in order to suppress heel and toe wear, it has been proposed to close the lug grooves and arrange the ribs (see, for example, Patent Document 4).
JP-A-5-246214 Japanese Utility Model Publication No. 03-077772 Japanese Patent Laid-Open No. 03-136909 JP 62-15807 A

  However, if the groove width is widened, drainage generally improves, but simply widening the groove width may result in insufficient block rigidity or pattern noise worsening due to an increase in groove air volume.

  Generally, the land portion row is provided with a lug groove for drainage, but the continuous smooth grounding property is impaired by this lug groove and often becomes a source of pattern noise.

  On the other hand, plain land rows without soaking grooves (so-called ribs) have not only reduced wet drainage but also blip on low μ (coefficient of friction) roads and riding comfort caused by too high land stiffness. Causes deterioration. Also, the impression that it seems to slip for the purpose of viewing is not preferable.

  As a method for reducing the air column resonance noise, it has been proposed to arrange the groove width to be greatly changed to around 50% (Patent Document 3). There is a concern about the generation of pitch noise due to the inclined grooves.

  The present invention has been made to solve the above problems, and an object thereof is to provide a pneumatic tire with improved pattern noise, uneven wear resistance, and steering stability without sacrificing wet performance.

The invention according to claim 1 is a pneumatic tire in which a plurality of circumferential main grooves are arranged in the tread, and the circumferential main groove is located on the innermost side when the vehicle is mounted from the end of the tread surface on the outer side when the vehicle is mounted. A plurality of inclined sipes that are continuously inclined to the tire width direction and that are closed at the time of contact are disposed at intervals in the circumferential direction of the tread, and the circumferential dimension defined by the circumferential main groove and the inclined sipes is A block having a long long pitch and a short block having a short circumferential dimension are partitioned, and the width of the short block is narrower than the width of the long block in the tread tread center region.

  Next, the operation of the pneumatic tire according to claim 1 will be described.

  In the pneumatic tire according to the first aspect, since the plurality of circumferential main grooves are arranged in the tread, basic drainage performance is ensured.

  In the case of the negative camber, a load is applied to the inner side of the tread of the pneumatic tire when the vehicle is mounted, and the inner land portion is easily worn when the vehicle is mounted. Further, in the case of the negative camber, the tire is inclined, so that the diameter of the inner portion of the tread when the vehicle is mounted is smaller than the actual diameter, and is dragged with respect to the road surface by a difference of diameter × π in one rotation.

  In the pneumatic tire according to claim 1, since the inclined sipe is not formed in the land portion adjacent to the vehicle inner side of the innermost circumferential main groove when the vehicle is mounted, the land portion is formed in a rib shape continuous in the circumferential direction. It becomes. When the land portion is formed into a rib shape that is continuous in the circumferential direction, the land portion has a high rigidity in the tire circumferential direction (in comparison with the land portion that forms the inclined sipe), and the circumferential length is prevented from being shortened. For this reason, it can suppress that the innermost turning radius becomes small at the time of vehicle mounting, and can suppress wear by dragging.

  On the other hand, since the land portion adjacent to the vehicle outer side of the outermost circumferential main groove when mounted on the vehicle is divided by the inclined sipe, the rigidity is reduced compared to the land portion that is not divided by the inclined sipe, and the lateral direction during cornering While ensuring the rigidity, the turning radius becomes the direction of reduction (because at least the groove width of the inclined sipe becomes the direction in which the circumferential length becomes shorter), and drag wear due to an increase in diameter can be suppressed.

  Here, when the overall width of the circumferential main groove is reduced as in the prior art to reduce air columnar resonance noise, drainage performance is sacrificed. However, in the pneumatic tire according to claim 1, The width of the short block is narrower than the width of the long block, that is, the width of the circumferential main groove that partitions these blocks is increased in some places, so that air columnar resonance can be dispersed and pattern noise can be improved. .

  In addition, if the wide groove portion of the circumferential main groove is long in the circumferential direction, the sound pressure energy of the air columnar resonance is increased, which is not preferable. Therefore, the groove width is widened by a short block portion having a short circumferential dimension. Yes.

  In addition, the width of the long block with the long circumferential dimension is wide, and the width of the short block with the short circumferential dimension is narrowed. I was able to turn it on. For this reason, air columnar resonance noise can be reduced while maintaining uneven wear resistance and steering stability of the land portion sandwiched between the circumferential main grooves.

  According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the inclined sipe that defines the long block does not overlap in the circumferential direction within the contact surface.

  Next, the operation of the pneumatic tire according to claim 2 will be described.

  By not overlapping all the sloping sipes that define the long block in the circumferential direction within the ground plane, the phase of pitch noise caused by the sloping sipes can be completely shifted, and the pattern noise can be improved.

  According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the circumferential main groove has an inner tread edge that is parallel to the tire circumferential direction and linear when mounted on the vehicle. It is characterized by that.

  Next, the operation of the pneumatic tire according to claim 3 will be described.

  When a vehicle corners, a large load is applied to the tire outside the cornering radius of the vehicle, and when a negative camber is attached, the side that receives input from the road surface is the edge of the land outside the vehicle (edge) This is the part that wears due to increased pressure during cornering. For this reason, the lateral force, and the edge on the vehicle outer side of the land portion, that is, the tread edge (opening edge) on the inner side of the circumferential main groove when the vehicle is mounted are parallel and straight in the tire circumferential direction. It is preferable that the wear can be made uniform (if the tread edge of the circumferential main groove is uneven, it causes lateral force fluctuations and uneven wear).

  Moreover, the mounting direction of a pneumatic tire can also be determined by looking at the direction of the tread edge of the circumferential main groove that is parallel and straight with the tire circumferential direction.

  According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the groove wall of the circumferential main groove that defines an inner side of the short block when the vehicle is mounted. Is characterized in that the groove wall angle with respect to the normal line perpendicular to the tread surface is larger than the groove wall of the circumferential main groove defining the long block.

  Next, the operation of the pneumatic tire according to claim 4 will be described.

  Since the short block is narrower than the long block, the lateral rigidity is lower than that of the long block. For this reason, the groove wall angle of the circumferential main groove defining the inner side when the short block is mounted on the vehicle is set to be larger than the groove wall angle of the circumferential main groove defining the long block. By doing so, the rigidity of the short block in the tire width direction can be increased, and a large lateral force can be obtained even in the short block.

  According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects, the tread edge of the short block facing the inside when the vehicle is mounted is chamfered. It is characterized by that.

  Next, the operation of the pneumatic tire according to claim 5 will be described.

  By chamfering the tread edge that faces the inner side when a short block is mounted on the vehicle, the rubber at the block edge due to load or lateral force escapes (note that the land portion of the tread formed of rubber (elastic body) is grounded) Then, a force that swells in the vicinity of the edge of the land part to the groove side parallel to the road surface acts, and a crushing force as a reaction force of this force acts on the tread.) Frictional force can be generated as a whole. Therefore, the cornering force can be increased.

  Note that even if chamfering is applied to the tread edge that faces the inside when the short block is mounted on the vehicle, there is virtually no effect on the rigidity of the short block in the tire width direction, and the lateral force obtained by the short block is reduced. There is no such thing.

According to a sixth aspect of the present invention, in the pneumatic tire according to any one of the first to fifth aspects, the land portion row in the ground contact surface is a groove that does not close at the time of ground contact , which impairs circumferential continuity. It is characterized by not being divided by.

  Next, the operation of the pneumatic tire according to claim 6 will be described.

  The land portion extending in the circumferential direction formed between the circumferential main groove and the circumferential main groove may be defined by an inclined sipe having a groove width that is closed when the ground is touched. It is better not to divide with grooves that impair the continuity of direction. This is caused when a groove that does not close at the time of ground contact is provided in the land portion, the block-shaped land portion spaced in the circumferential direction is grounded when the tire rolls, and the block-shaped land portion is grounded. This is to generate impact noise (which causes pitch noise).

  If a groove that does not close at the time of grounding is not provided in the land portion, the land portion can be grounded smoothly, and noise generation can be suppressed.

According to a seventh aspect of the present invention, in the pneumatic tire according to any one of the first to sixth aspects, the inner side located on the inner side when the vehicle is mounted than the inner circumferential main groove on the inner side when the vehicle is mounted. The shoulder land portion is not divided by a groove that does not close at the time of ground contact , which impairs circumferential continuity.

  Next, the operation of the pneumatic tire according to claim 7 will be described.

  When a negative camber is applied, the tread has a greater burden on the inner side when the vehicle is mounted than on the outer side when the vehicle is mounted, and also has rib-like land portions that are continuous in the circumferential direction and grooves that impair the continuity in the circumferential direction. When compared with the block-shaped land portion formed by the provision, the block-shaped land portion is easily deformed with respect to the input in the circumferential direction.

  Therefore, in order to suppress uneven wear, it is preferable that the inner shoulder land portion positioned on the inner side when the vehicle is mounted than the innermost circumferential main groove when the vehicle is mounted is not divided by a groove that impairs the continuity in the circumferential direction. .

  The invention according to claim 8 is the pneumatic tire according to any one of claims 1 to 6, wherein the pneumatic tire is arranged on the outer side in the tire width direction than the outermost main groove on the outermost side when the vehicle is mounted. In the outer shoulder land portion, at least one discontinuous sipe is provided between the inclined grooves.

  Next, the operation of the pneumatic tire according to claim 8 will be described.

  When the steering wheel is operated, the burden on the outer shoulder land located outside the circumferential main groove on the outermost outer circumference when a pneumatic tire is mounted on the vehicle is greater than when traveling straight, which affects steering stability. Also grows.

  In the pneumatic tire according to claim 8, by providing at least one discontinuous sipe between the inclined grooves of the outer shoulder land portion, the outer shoulder land portion can be grounded while sufficiently securing rigidity. It can be increased, and high steering stability can be secured.

  The invention according to claim 9 is the pneumatic tire according to any one of claims 1 to 8, wherein the inner side is located on the inner side when the vehicle is mounted than the circumferential main groove on the innermost side when the vehicle is mounted. A plurality of discontinuous sipes extending obliquely with respect to the circumferential direction are disposed on the shoulder land portion, and the circumferential pitch length of the two inclined sipes that divides the short block into the circumferential pitch length of the discontinuous sipes It is characterized by being set to 1/2 or less of the length.

  Next, the operation of the pneumatic tire according to claim 9 will be described.

  As described in the operation of the seventh aspect, when the negative camber is applied, the load on the inner side of the tread is larger than that on the outer side when the vehicle is mounted.

  In addition, on the front wheels of vehicles with negative cambers, the load movement during braking (front turning) pushes down both front tires in the C-shaped direction, so that the tread has a rotational load on the inside when the vehicle is installed. It becomes larger and the inner land portion is easily worn when the vehicle is mounted.

  Therefore, the inner shoulder land portion can secure high rigidity by not providing a continuous sipe that crosses the land portion, and wear due to braking can be suppressed.

  Further, by disposing discontinuous sipes on the inner shoulder land portion, it is possible to reduce the compression rigidity of the inner shoulder land portion while securing the land portion rigidity for suppressing wear due to braking. In the land portion, a portion away from the road surface at the time of kicking slips with respect to the road surface, but wear can be reduced if the ground pressure of the kicking portion is low.

  In the pneumatic tire according to claim 9, the discontinuous sipes are disposed on the inner shoulder land portion to reduce the compression rigidity, so that the contact pressure at the kicked-out portion can be reduced, and wear caused by kicking is suppressed. be able to.

  Furthermore, road noise is also reduced by reducing the compression rigidity of the inner shoulder land portion.

  According to a tenth aspect of the present invention, in the pneumatic tire according to any one of the first to ninth aspects, in the tread, the circumferential main groove on the outermost side when mounted on the vehicle and the innermost groove on the inner side when mounted on the vehicle. When the tread center region is formed between the circumferential main grooves, the widths of the long blocks in the tread center region are all equal.

  Next, the operation of the pneumatic tire according to claim 10 will be described.

  It is known that in the tread center region, deformation toward the ground contact center direction and deformation in the opposite direction occur in a direction parallel to the road surface until the tread is grounded and separated from the road surface. .

  If the wide land part and the narrow land part are unevenly arranged in the tread center region, the balance of deformation of the tread when the ground contact surface is viewed as a whole will be lost and it will be greatly deformed in one direction. An excessive residual lateral force may be generated in the tread, which may adversely affect steering stability.

  In the pneumatic tire according to claim 10, in the tread center region, the widths of the long blocks having high rigidity compared to the short blocks are all made equal. Therefore, it is possible to suppress the generation of excessive residual lateral force and to obtain high steering stability.

  In addition, it is more preferable to arrange a plurality of long blocks equally on the left and right sides of the tire equator plane in order to suppress the occurrence of residual lateral force.

  The invention according to claim 11 is the pneumatic tire according to any one of claims 1 to 10, wherein the plurality of circumferential main grooves defining the long block are centered on a tire equatorial plane. It is characterized by being arranged symmetrically.

  Next, the operation of the pneumatic tire according to claim 11 will be described.

  Since the plurality of circumferential main grooves defining the long block are arranged symmetrically about the tire equator plane, the long blocks can be evenly arranged on the left and right sides of the tire equator plane.

  The invention according to claim 12 is the pneumatic tire according to any one of claims 1 to 11, wherein when viewed between the short blocks adjacent to each other in the tire width direction, one side in the tire width direction. The inclined sipe that divides the short block and the inclined sipe that divides the short block on the other side in the tire width direction do not overlap in the tire circumferential direction, and there are two inclined sipes in the tire circumferential direction that divide the short block. It does not overlap in the tire circumferential direction.

  Next, the operation of the pneumatic tire according to claim 12 will be described.

  Pattern noise can be reduced by not simultaneously grounding the inclined sipes adjacent in the width direction.

  Similarly, pattern noise can be reduced by not simultaneously grounding two inclined sipes in the tire circumferential direction that define the short block.

  The invention according to claim 13 is the pneumatic tire according to any one of claims 1 to 12, wherein, in the tread, the circumferential main groove on the outermost side when the vehicle is mounted and the innermost main groove when the vehicle is mounted. When the tread center region is defined between the circumferential main groove, the long block and the short block are circumferential in the land portion sandwiched between the two circumferential main grooves in the tread center region. It is characterized by being arranged alternately.

  Next, the operation of the pneumatic tire according to claim 13 will be described.

  By arranging the long blocks and the short blocks alternately in the circumferential direction, it is possible to make the wear distribution per tire circumference uniform.

  As described above, according to the pneumatic tire of the present invention, there is an excellent effect that pattern noise, uneven wear, and steering stability can be improved without sacrificing wet performance.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, two circumferential main grooves 14 are arranged on each of the left and right sides of the tread 12 of the pneumatic tire 10 of the present embodiment with the tire equatorial plane CL interposed therebetween.

  The circumferential main grooves 14 are arranged at symmetrical positions with respect to the tire equatorial plane CL.

  The tread 12 has a first inclined sipe 16 that inclines upward from the tread tread surface end 12E on the outer side (in the arrow OUT direction) when the vehicle is mounted toward the circumferential main groove 14 on the innermost side (in the arrow IN direction) when the vehicle is mounted. A plurality of tires are formed in the tire circumferential direction.

  Here, the land portion on the vehicle inner side than the innermost circumferential main groove 14 when the vehicle is mounted is the inner shoulder rib 18, and the land portion outside the vehicle with respect to the outermost main groove 14 when the vehicle is mounted is the outer shoulder. Ribs 20 are provided.

  The center rib 22 extending in the circumferential direction sandwiched between the circumferential main grooves 14 is partitioned by the first inclined sipe 16 into a long block 24 having a long circumferential dimension and a short block 26 having a short circumferential dimension. The dimension in the circumferential direction of the block is a value measured on the center line in the width direction of the block.

  In the present embodiment, the long blocks 24 and the short blocks 26 are alternately arranged in the tire circumferential direction.

  Here, the width of the short block 26 is set to be narrower than the width of the long block 24, and the circumferential main groove 14 has an inner groove opening edge formed in a straight line parallel to the tire circumferential direction when mounted on the vehicle. .

  The inner shoulder rib 18 is formed with a circumferential narrow groove 30 on the circumferential main groove 14 side, and a first discontinuous sipe 28 that is inclined to the left with a small angle with respect to the tire axial direction. Arranged at intervals.

  The circumferential pitch length of the first discontinuous sipe 28 formed on the inner shoulder rib 18 is set to ½ or less of the circumferential pitch length of the two first inclined sipes 16 that define the short block 26. Is preferred.

  In the present embodiment, the circumferential pitch length of the first discontinuous sipes 28 is set to ½ of the circumferential pitch length of the two first inclined sipes 16 that define the short block 26.

  On the other hand, the outer shoulder rib 20 is formed with a circumferential narrow groove 30 on the circumferential main groove 14 side, like the inner shoulder rib 18, and the first inclined sipe 16 and the first sloping sipe 16 that define the long block 24. A second inclined sipe 32 extending in parallel with the first inclined sipe 16 from the tread tread surface end 12 </ b> E toward the first inclined sipe 16 is formed at an intermediate portion with the inclined sipe 16.

  Further, the outer shoulder rib 20 has an intermediate portion between the first inclined sipe 16 and the second inclined sipe 32 and an intermediate portion between the first inclined sipe 16 and the first inclined sipe 16 that define the short block 26. A second discontinuous sipe 34 that is parallel to the first inclined sipe 16 is formed.

  In this embodiment, when it sees in the tire width direction, the 1st inclination sipe 16 which divides the long block 24 does not overlap.

  As shown in FIG. 2A, the groove wall angle (with respect to the normal HL perpendicular to the tread surface) of the groove wall 14A of the circumferential main groove 14 that divides the inner side of the short block 26 when the vehicle is mounted is θA, 2 (B), when the groove wall angle of the groove wall 14B of the circumferential main groove 14 that divides the inner side of the long block 24 when the vehicle is mounted is θB, the groove wall angle θA of the short block 26 is Is set larger than the groove wall angle θB of the long block 24.

  As shown in FIG. 1, the widths of the long blocks 24 are all set equal between the two outer circumferential main grooves 14 on the outermost side in the tire axial direction.

Moreover, when the short blocks 26 adjacent to each other in the tire width direction are viewed, the first inclined sipe 16 that defines the short block 26 on one side in the tire width direction and the first block that defines the short block 26 on the other side in the tire width direction. The inclined sipe 16 does not overlap in the tire circumferential direction, and the two first inclined sipes 16 in the tire circumferential direction that define the short block 26 do not overlap in the tire circumferential direction.
(Function)
In the pneumatic tire 10 of the present embodiment, basic drainage performance is ensured by the plurality of circumferential main grooves 14 provided in the tread 12.

  When the negative camber is applied, a large load is applied to the tread 12 toward the inner side of the vehicle, and the inner land portion is easily worn when the vehicle is mounted.

  The first inclined sipe 16 is not formed on the inner shoulder rib 18 and has a rib shape that is completely continuous in the tire circumferential direction. Wear can be suppressed.

  On the other hand, since the outer shoulder rib 20 is formed with a plurality of first inclined sipes 16 that are transverse to each other in the tire axial direction, the rigidity is reduced in contrast to the case where the first inclined sipes 16 are not formed. For this reason, it is possible to suppress drag wear due to the turning radius being reduced and the diameter being increased while securing the lateral rigidity during cornering.

  Further, when the groove width of the circumferential main groove 14 is reduced as a whole to reduce the air column resonance noise, drainage performance is sacrificed. However, in the pneumatic tire 10 of the present embodiment, the short block 26 and the long block 24 are alternately arranged in the circumferential direction, and the wide portion of the circumferential main groove 14 is dispersedly distributed, so that air columnar resonance can be dispersed and pattern noise can be improved. In addition, since the groove width of the circumferential main groove 14 is widened by the short block portion having a short circumferential dimension, the sound pressure energy of the air columnar resonance sound is reduced rather than by widening the groove width by the long block portion having a long circumferential dimension. Reduced.

  Since the width of the long block 24 having a long circumferential dimension is set wide and the width of the short block 26 having a short circumferential dimension is set narrow, the groove of the circumferential main groove 14 is not changed much without changing the vertical and horizontal rigidity distribution of the block. The width could be changed, and the air columnar resonance noise could be reduced while maintaining the uneven wear resistance and steering stability of the center rib 22.

  Further, since all the first inclined sipes 16 that divide the long block 24 are not overlapped in the circumferential direction, the phase of the pitch noise caused by the first inclined sipes 16 can be completely shifted, and the pattern Noise was improved.

  Since the edge of each rib on the vehicle outer side, that is, the inner tread edge at the time of vehicle mounting of the circumferential main groove 14 is made parallel and straight in the tire circumferential direction, the lateral force during cornering can be made uniform. In addition, the wear of each rib could be made uniform.

  Moreover, the mounting direction of the pneumatic tire 10 can be determined by looking at the direction of the tread edge of the circumferential main groove 14 that is parallel to the tire circumferential direction and straight.

  Since the short block 26 is narrower than the long block 24, if the groove wall angles are all the same, the lateral rigidity will be lower than that of the long block 24, but in this embodiment, The groove wall angle θA of the groove wall 14A of the circumferential main groove 14 defining the inner side when the short block 26 is mounted on the vehicle is defined as the groove wall angle θA of the groove wall 14B of the circumferential main groove 14 defining the long block 14. Since it was set larger than θB, the rigidity of the short block 26 in the tire width direction could be increased, and a large lateral force could be obtained even in the short block 26.

  Since the center rib 22 is formed with only the first inclined sipe 16 having a groove width that closes at the time of ground contact, the center rib 22 can be grounded smoothly with respect to the road surface, and generation of noise is suppressed.

  Since the inner shoulder rib 18 is not divided by a groove that impairs continuity in the circumferential direction, high rigidity in the circumferential direction can be ensured, and even when the load increases due to braking, the inner shoulder rib 18 is not easily worn.

  By disposing the first discontinuous sipe 28 on the inner shoulder rib 18, it is possible to reduce the compression rigidity of the inner shoulder rib 18 while ensuring the rigidity for suppressing wear due to braking. It is possible to reduce the contact pressure at the kicked-out portion and to suppress wear caused by kicking-out.

  Further, the road noise is reduced by reducing the compression rigidity of the inner shoulder rib 18.

  When the steering wheel operation is performed, the load on the outside when the tread 12 is mounted on the vehicle increases, but the outer shoulder rib 20 is provided with the second discontinuous sipe 34 to improve the grounding property while ensuring sufficient rigidity. As a result, high maneuvering stability was ensured.

  When the tread 12 comes in contact with the road surface and separates from the road surface, the tread 12 undergoes deformation toward the center of contact with the ground and deformation in the opposite direction. However, in the pneumatic tire 10 of the present embodiment, a short block is formed in the tread center region. The width of the long block 24, which is high in contrast to 26, is made equal to each other, and is further arranged in an equal number on both sides of the tire equatorial plane CL, so that the generation of excess residual lateral force can be suppressed, and high steering stability is achieved. Obtained.

  In each rib, the first inclined sipes 16 adjacent to each other in the width direction are arranged so as not to be grounded at the same time, so that the pattern noise can be reduced. Similarly, the pattern noise can be reduced by not simultaneously grounding the two first inclined sipes 16 defining the short block 26.

  Since the long blocks 24 and the short blocks 26 are alternately arranged in the circumferential direction, the wear distribution of the center rib 22 per tire circumference can be made uniform.

Moreover, the mounting direction of the pneumatic tire 10 can also be determined by looking at the direction of the circumferential main groove side edge that is parallel and straight with the tire circumferential direction.
(Other embodiments)
In addition, as shown in FIG. 3, you may chamfer the tread edge part which faces the inner side at the time of vehicle mounting of the short block 26. FIG.

  By chamfering 36 on the tread edge that faces the inner side of the short block 26 when the vehicle is mounted, the rubber at the block edge due to a load or lateral force (so-called crushing) is suppressed, and frictional force is exerted on the entire block contact surface. Can be generated. Therefore, the cornering force can be increased.

  Here, the chamfer angle (angle θ of the chamfered portion with respect to the tread surface) is preferably 45 ° ± 10 °. Above this, there is a risk of crushing on the side of the block. On the other hand, below this, there is a possibility of crushing on the block tread side.

  Further, the chamfering height h is preferably 4 mm ± 2 mm. Above this, the tread width with a fixed chamfer angle is reduced. On the other hand, below this, the block side faces are crushed.

Note that even if the chamfering 36 is provided on the tread edge that faces the inner side of the short block 26 when the vehicle is mounted, the rigidity in the tire width direction of the short block 26 is not substantially affected, and the lateral block obtained by the short block 26 is not affected. There is virtually no reduction in power.
(Test example)
In order to confirm the effect of the present invention, two types of conventional pneumatic tires and two types of tires according to the present invention were prepared, and wet hydroplaning performance, pattern noise, dry steering stability, and resistance A comparison was made for uneven wear.

  Wet hydroplaning performance: Feeling evaluation by a test driver at the critical speed of hydroplaning when passing through a wet road with a depth of 5 mm. The evaluation is expressed as an index with Conventional Example 1 being 100, and the larger the value, the higher the wet hydroplaning performance.

  Pattern noise: The test driver evaluated the in-vehicle sound when coasting from 100 km / h on a straight smooth road. The evaluation is an index display with the conventional example 1 being 100, and the larger the numerical value, the lower the pattern noise.

  Dry handling stability: Test driver's feeling evaluation when driving on a dry circuit course in various driving modes. The evaluation is an index display in which Conventional Example 1 is set to 100, and the larger the numerical value, the better the dry steering stability.

  Uneven wear resistance: in mode running assuming highways, urban roads, and mountain slopes, visual evaluation of tire tread surface after running at 5000 km and 10000 km, and overall evaluation of remaining groove measurement. The evaluation is an index display with Conventional Example 1 being 100, and the larger the value, the better the uneven wear resistance.

Tire size: PSR225 / 45R17 (tread width 200mm)
Test conditions: Internal pressure 230 kPa, load equivalent to two passengers. Example tire: Pneumatic tire according to the embodiment described above. The dimensions and angles of each part are as described in Table 1 below.
Conventional example 1: It has a pattern shown in FIG. An inclined groove 40 corresponding to an inclined sipe crosses the tread 12, and an inclined narrow groove 42 that connects the tread tread surface end 12 </ b> E to the circumferential narrow groove 30 is formed. The dimensions and angles of each part are as described in Table 3 below.
Tire of conventional example 2: having a pattern shown in FIG. The groove width, block length, and block width are different from those of the embodiment. The dimensions and angles of each part are as described in Table 4 below.

  Each evaluation is as shown in Table 5 below.

  From the test results, it can be seen that the tire of the example to which the present invention is applied has improved pattern noise, uneven wear resistance, and steering stability without sacrificing wet performance.

1 is a plan view of a pneumatic tire according to an embodiment of the present invention. (A) is the 2A-2A sectional view taken on the line of the short block shown in FIG. 1, (B) is the sectional view on the 2B-2B line of the long block shown in FIG. It is sectional drawing of the short block of the pneumatic tire which concerns on other embodiment. It is a top view of the pneumatic tire which concerns on the prior art example 1. FIG. 6 is a plan view of a pneumatic tire according to Conventional Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 14 Circumferential main groove 16 1st inclination sipe 18 Inner shoulder rib 20 Outer shoulder rib 22 Center rib 24 Long block 26 Short block 28 First discontinuous sipe

Claims (13)

A pneumatic tire having a plurality of circumferential main grooves arranged on a tread,
A sloped sipe that closes at the time of grounding that extends continuously incline with respect to the tire width direction from the end of the tread surface on the outside when the vehicle is mounted to the circumferential main groove located on the innermost side when the vehicle is mounted is spaced apart in the circumferential direction of the tread A plurality of open spaces, and a long pitch block having a long circumferential dimension defined by the circumferential main groove and the inclined sipe, and a short block having a short circumferential dimension are partitioned,
A pneumatic tire characterized in that, in the tread tread center region, the width of the short block is narrower than the width of the long block. 2. The pneumatic tire according to claim 1, wherein the inclined sipes that divide the long block do not overlap in a circumferential direction within a contact surface. 3. The pneumatic tire according to claim 1, wherein the circumferential main groove has an inner tread edge that is parallel to the tire circumferential direction and linear when mounted on the vehicle. The groove wall of the circumferential main groove that defines the inner side of the short block when mounted on the vehicle has a groove wall angle with respect to a normal perpendicular to the tread surface, rather than the groove wall of the circumferential main groove that defines the long block. The pneumatic tire according to any one of claims 1 to 3, wherein the tire is large. The pneumatic tire according to any one of claims 1 to 4, wherein a tread edge portion of the short block facing inward when the vehicle is mounted is chamfered. The pneumatic tire according to any one of claims 1 to 5, wherein the land portion row in the contact surface is not divided by a groove that does not close at the time of contact that impairs continuity in the circumferential direction. . The inner shoulder land portion located on the inner side when the vehicle is mounted than the innermost circumferential main groove when the vehicle is mounted is not divided by a groove that does not close at the time of ground contact that impairs continuity in the circumferential direction. The pneumatic tire according to any one of claims 1 to 6. At least one discontinuous sipe is provided between the inclined grooves in the outer shoulder land portion arranged on the outer side in the tire width direction with respect to the outermost main groove on the outermost side when the vehicle is mounted. The pneumatic tire according to any one of claims 1 to 6. A plurality of discontinuous sipes extending obliquely with respect to the circumferential direction are disposed on the inner shoulder land portion located on the inner side when the vehicle is mounted than the inner circumferential circumferential groove on the innermost side when the vehicle is mounted. The circumferential pitch length is set to ½ or less of the circumferential pitch length of the two inclined sipes that divide the short block. 9. Pneumatic tires. In the tread, when the space between the outermost main groove on the outermost side when the vehicle is mounted and the circumferential main groove on the innermost side when the vehicle is mounted is a tread center region,
The pneumatic tire according to any one of claims 1 to 9, wherein all the long blocks in the tread center region have the same width. The plurality of circumferential main grooves that define the long block are arranged symmetrically with respect to the tire equatorial plane as claimed in any one of claims 1 to 10. Pneumatic tire. When viewed between the short blocks adjacent to each other in the tire width direction, an inclined sipe that defines the short block on one side in the tire width direction and an inclined sipe that defines the short block on the other side in the tire width direction are in the tire circumferential direction. Without overlapping
The pneumatic tire according to any one of claims 1 to 11, wherein two inclined sipes in the tire circumferential direction that define the short block do not overlap in the tire circumferential direction. In the tread, when the space between the outermost main groove on the outermost side when the vehicle is mounted and the circumferential main groove on the innermost side when the vehicle is mounted is a tread center region, The air according to any one of claims 1 to 12, wherein the long blocks and the short blocks are alternately arranged in a circumferential direction in a land portion sandwiched between directional main grooves. Tires.

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