JP6423739B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire with improved residual cornering force while maintaining uneven wear resistance.

  A pneumatic tire having a block pattern in which a plurality of blocks are divided into a plurality of main grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire axial direction is known in the tread portion. In recent years, such a block pattern has been improved, the price tear residual cornering force (hereinafter sometimes referred to as “residual CF”) is increased, and the intentional direction (for example, the direction in which the tire flows due to a road surface cant or the like) The direction of the tire is controlled in one direction.

  Based on FIGS. 5A and 5B, a mechanism for generating a residual CF based on a block will be briefly described. First, FIG. 5A shows a partial front view of the tire. Since the outer surface profile of the tread portion t is formed in an arc shape that protrudes outward in the tire radial direction centering on the tire equator C, the rotation radius differs at the inner and outer positions in the tire axial direction. For this reason, when the tire is running, driving force is dragged to the block on the center side having a larger radius of rotation Rc compared to the average radius of rotation (dynamic load radius) Ra, and dragged to the block on the shoulder side having a smaller radius of rotation Rs. The braking force due to each acts.

  Next, FIG. 5B shows a schematic plan view of the center block a arranged on the center side forming a rhombus and the shoulder block b arranged on the shoulder side. The driving force f1 and the braking force f2 described above act on the apexes p1 and p2 on the first arrival side in the rotational direction of the blocks a and b, respectively, and a torsional torque m is generated in the blocks a and b. Due to this twisting torque, residual CF is generated in the tire.

  Therefore, in order to increase the residual CF, it is effective to generate a large torsion torque m in the same direction in each of the blocks a and b. For this reason, conventionally, it has been considered effective to relatively increase the angle of the lateral groove with respect to the tire axial direction.

  However, when the angle of the lateral groove is increased, the residual CF increases, but there is a problem that the rigidity of the block is lowered and anisotropy occurs, and the uneven wear resistance performance deteriorates.

  Further, the driving force and the braking force do not act on the position of the dynamic load radius of the tread portion. Therefore, if the block is disposed across the dynamic load radius, the torsional torque m cannot be increased sufficiently. In addition, there are the following as technical documents related to residual CF.

Japanese Patent Laid-Open No. 2004-98791

  The present invention has been devised in view of the above problems, and limits the ratio between the width of the center land portion and the width of the shoulder land portion, and the center lateral groove and shoulder land provided in the center land portion. The main object is to provide a pneumatic tire capable of increasing the residual CF while maintaining the uneven wear resistance performance, based on the limitation of the arrangement angle and the arrangement position with the shoulder lateral groove provided in the section.

  In the present invention, one center main groove extending continuously on the tire equator in the tire circumferential direction and a pair of shoulder main grooves extending continuously on both sides of the center main groove in the tire circumferential direction are provided on the tread portion. By being provided, the pneumatic tire includes a pair of center land portions extending between the center main groove and the shoulder main groove, and a pair of shoulder land portions formed outside the shoulder main groove. The center land portion and the shoulder land portion are divided into a plurality of center blocks and shoulder blocks by a center lateral groove and a shoulder lateral groove that are spaced apart in the tire circumferential direction, respectively. Inclined at an angle of 35 to 55 degrees with respect to the tire, and the inner side in the tire axial direction of the shoulder lateral groove is inclined in the direction opposite to the center lateral groove. Both communicate with the shoulder main groove at an angle of 20 to 40 degrees with respect to the tire axial direction, and the outer portion of the shoulder lateral groove opens at an angle of 10 degrees or less with respect to the tire axial direction at the tread grounding end. The width Wc in the tire axial direction of the center land portion is 0.65 to 0.75 times the width Ws in the tire axial direction of the shoulder land portion, and the communication position of the center lateral groove to the shoulder main groove is The shoulder lateral groove is displaced in the tire circumferential direction from the communication position with the shoulder main groove, and the positional deviation amount is 0.3 to 0.5 times the spaced pitch of the shoulder lateral groove. .

  In the pneumatic tire according to the present invention, the shoulder block has a position at a distance of 25 to 45% of the width of the shoulder land portion from the outer groove edge in the tire axial direction of the shoulder main groove. It is desirable to provide a shoulder sub-groove extending in the tire circumferential direction with a groove depth smaller than the groove.

  In the pneumatic tire according to the present invention, the shoulder main groove is located at the center block at a position separated from the groove edge of the center main groove by 35 to 55% of the width of the center land portion outward in the tire axial direction. It is desirable to provide a center sub-groove extending in the tire circumferential direction with a smaller groove depth.

  In the pneumatic tire according to the present invention, the center block has an outer end in the tire axial direction communicating with the shoulder main groove and an inner end in the tire axial direction at the center main center at a substantially intermediate position in the tire circumferential direction. It is desirable to provide a center lug groove that terminates without communicating with the groove.

  The pneumatic tire of the present invention includes a center main groove extending continuously on the tire equator in the tire circumferential direction on the tread portion, and a pair of shoulders extending continuously on both sides of the center main groove in the tire circumferential direction. By providing a main groove, comprising a pair of center land portions extending between the center main groove and the shoulder main groove, and a pair of shoulder land portions formed outside the shoulder main groove, The center land portion and the shoulder land portion are divided into a plurality of center blocks and shoulder blocks by a center lateral groove and a shoulder lateral groove that are spaced apart in the tire circumferential direction, respectively. The width Wc of the center land portion in the tire axial direction is formed to be 0.65 to 0.75 times the width Ws of the shoulder land portion in the tire axial direction. As a result, during tire rolling, a large driving force is applied to the center block on the tire equator side and a large braking force is applied to the shoulder block, so that the torsional torque generated at the center and the shoulder block is increased.

  Further, the inner side portion of the shoulder lateral groove in the tire axial direction is inclined in the direction opposite to the center lateral groove. Thereby, a large torsion torque in the same direction is generated in the center block on which the driving force acts and on the shoulder block on which the braking force acts. Therefore, the pneumatic tire of the present invention can generate a large residual CF.

  In the pneumatic tire of the present invention, the center lateral groove is inclined at an angle of 35 to 55 degrees with respect to the tire axial direction, and the shoulder lateral groove is inclined at an angle of 20 to 40 degrees with respect to the tire axial direction. The edge effect of the center lateral groove and the shoulder lateral groove is exhibited while ensuring the rigidity of the center land portion and the shoulder land portion. Therefore, the pneumatic tire of the present invention improves residual CF and uneven wear resistance in a well-balanced manner.

  Further, the outer portion of the shoulder lateral groove opens at the tread ground contact end at an angle of 10 degrees or less with respect to the tire axial direction. Such a shoulder lateral groove improves the rigidity of the shoulder land portion on the tread grounding end side where a large braking force acts and facilitates drainage to the tread grounding end side. Therefore, the pneumatic tire of the present invention improves uneven wear resistance and drainage performance.

  Further, the communication position of the center lateral groove to the shoulder main groove continuously extending in the tire circumferential direction is shifted from the communication position of the shoulder lateral groove to the shoulder main groove in the tire circumferential direction, and the positional deviation amount is It is 0.3 to 0.5 times the separation pitch of the shoulder lateral groove. As a result, the top portion on the inner side in the tire axial direction of the shoulder block having low rigidity is adjacent to the central portion of the side edge of the center block having high rigidity, and the top portion on the outer side in the axial direction of the center block tire having low rigidity is high in rigidity. Adjacent to the central part of the side edge of the shoulder block. Accordingly, the pattern rigidity of the block is improved and the groove volume of the shoulder main groove is ensured. Further, since the positional deviation amount is within a specified range, the resonance vibration (air column resonance sound) of the air generated in the center main groove passing through the center lateral groove is reduced by being collided and absorbed by the shoulder block. Therefore, the pneumatic tire of the present invention improves uneven wear resistance, drainage performance and noise performance.

It is an expanded view of the tread part which shows the pneumatic tire of one Embodiment of this invention. It is the elements on larger scale of FIG. It is a schematic plan view showing the torsion torque which arises in each block of this embodiment. It is an expanded view of the tread part which shows a comparative example. (A) is the partial front view showing the rotation radius of a tire, (b) is a schematic plan view explaining the generation | occurrence | production mechanism of residual CF.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, a pneumatic tire (hereinafter, simply referred to as “tire”) 1 according to the present embodiment is suitably used as a tire for a passenger car, for example. One center main groove 3 extending continuously in the tire circumferential direction on the tire equator C and a pair of shoulder main grooves 4 extending continuously in the tire circumferential direction on both sides of the center main groove 3 are provided. As a result, the tread portion 2 has a pair of center land portions 5 extending between the center main groove 3 and the shoulder main groove 4 and a pair of shoulder land portions extending between the shoulder main groove 4 and the tread grounding end Te. 6 are formed.

  Here, the “tread grounding end” Te is applied to the tire 1 in a normal state in which the rim is assembled to the normal rim and filled with the normal internal pressure, and a normal load is applied to the flat tire with a camber angle of 0 degree. Is defined as the contact position on the outermost side in the tire axial direction. A distance in the tire axial direction between the tread ground contact Te and Te is determined as a tread ground contact width TW. Further, the dimensions and the like of each part of the tire are values in the normal state unless otherwise specified.

  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 and “Design Rim” for TRA. For ETRTO, use "Measuring Rim".

  The “regular internal pressure” is the air pressure defined by each standard for each tire in the standard system including the standard on which the tire is based, and is “maximum air pressure” for JATMA and table for TRA. The maximum value described in TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES is "INFLATION PRESSURE" for ETRTO, but 180 kPa for tires for passenger cars.

  Furthermore, “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. “Maximum load capacity” for JATMA, “TIRE” for TRA The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is “LOAD CAPACITY” if it is ETRTO, but if the tire is for a passenger car, the load is equivalent to 88% of the above load.

  The center land portion 5 is provided with center lateral grooves 7 spaced in the tire circumferential direction. The center lateral groove 7 of the present embodiment extends over the entire width of the center land portion 5. Accordingly, the center land portion 5 forms a block row in which a plurality of center blocks 9 divided by the center main groove 3, the shoulder main groove 4, and the center lateral groove 7 are arranged in the tire circumferential direction.

  In the shoulder land portion 6, shoulder lateral grooves 8 are provided in the tire circumferential direction. The shoulder lateral groove 8 of the present embodiment extends over the entire width of the shoulder land portion 6. As a result, the shoulder land portion 6 forms a block row in which a plurality of shoulder blocks 10 divided by the shoulder main groove 4, the tread ground contact Te, and the shoulder lateral groove 8 are arranged in the tire circumferential direction.

  Note that the tread pattern of the present embodiment is formed in a substantially point-symmetric pattern except for a variable pitch with an arbitrary point on the tire equator C as the center.

  The center main groove 3 and the shoulder main groove 4 of this embodiment form a linear shape along the tire circumferential direction. Such main grooves 3 and 4 are desirable in that they can exhibit excellent drainage performance. Also, the groove widths of the center main groove 3 and the shoulder main groove 4 (the groove width perpendicular to the longitudinal direction of the groove, hereinafter the same applies to other grooves) W1, W2 and groove depths D1, D2 (not shown) ) Can be determined in accordance with customary practice, but if the groove widths W1 and W2 or the groove depths D1 and D2 are too large, the steering stability performance may be deteriorated. There is. In the case of a passenger car tire as in this embodiment, the groove widths W1 and W2 are preferably, for example, 4.0 to 8.0% of the tread ground contact width TW. The groove depths D1 and D2 are preferably 6.0 to 9.0 mm.

  FIG. 2 is an enlarged view of the tread portion 2 on the right side of FIG. As shown in FIG. 2, the center lateral groove 7 is inclined downward to the right, and an angle θ <b> 1 with respect to the tire axial direction is set to 35 to 55 degrees. As a result, the center block 9 is partitioned into a parallelogram shape that is downwardly lowered in plan view. As a particularly preferable aspect, it is desirable that the center lateral groove 7 be smoothly curved in an arc shape so that the angle θ1 gradually decreases toward the outer side in the tire axial direction as in the present embodiment. Such a center lateral groove 7 ensures a large lateral stiffness in the tire axial direction of the block on which a large lateral force acts during turning, and helps to improve drainage performance utilizing centrifugal force during turning.

  On the other hand, the inner side portion of the shoulder lateral groove 8 in the tire axial direction (for example, a portion larger than 50% of the width Ws of the shoulder land portion 6 from the inner end 8s of the shoulder lateral groove 8 in the tire axial direction) Is inclined in the reverse direction (upward to the right) and communicates with the shoulder main groove 4 at an angle θ2a of 20 to 40 degrees with respect to the tire axial direction. The outer side portion 8b of the shoulder lateral groove 8 is open to the tread ground contact Te at a small angle θ2b of 10 degrees or less with respect to the tire axial direction. In this example, the inner side portion 8a and the outer side portion 8b of the shoulder lateral groove 8 both extend with an upward slope. As a result, the shoulder block 10 is partitioned into a parallelogram shape that rises to the right in plan view. It is preferable that the shoulder lateral groove 8 has an arc shape in which the angle θ2 gradually decreases toward the tread ground contact Te side.

  The groove widths W3 and W4 and the groove depths D3 and D4 (not shown) of the center lateral groove 7 and the shoulder lateral groove 8 are respectively determined by customs, but in order to maintain high drainage performance and uneven wear resistance performance, The groove widths W3 and W4 of the lateral groove 7 and the shoulder lateral groove 8 are preferably 15% or more, more preferably 20% or more, and preferably 70% or less, more preferably 60% of the groove width W2 of the shoulder main groove 4. The following is desirable. Further, the groove depths D3 and D4 are preferably 60% or more of the groove depth D2 of the shoulder main groove 4, more preferably 70% or more, and preferably 95% or less. Since the groove width W4 of the shoulder lateral groove 8 of the present embodiment is larger than the groove width W3 of the center lateral groove 7, the drainage performance toward the tread ground contact Te side is enhanced. The groove widths W3 and W4 of the center lateral groove 7 and the shoulder lateral groove 8 of the present embodiment are formed with the same groove width over the length direction.

  In the tire 1 configured as described above, the center block 9 and the shoulder block 10 are formed in parallelogram shapes having different inclination directions, respectively. As a result, as shown in FIG. While acting on the first p1 of the center block 9 on the first arrival side and the braking force f2 acting on the first p2 on the first arrival side of the shoulder block 10, both the center block 9 and the shoulder block 10 are in the same direction (in this example, opposite to A clockwise torsional torque m can be generated.

  Furthermore, in the present invention, in order to maximize the torsional torque m in the same direction generated in the center block 9 and the shoulder block 10, the width Wc of the center land portion 5 in the tire axial direction is set so that the shoulder land portion 6 extends in the tire axial direction. It is formed 0.65 to 0.75 times the width Ws.

  As a result of various experiments, in the profile of the outer surface of a general tread portion of a passenger car tire (curvature radius of about 300 to 800 mm, camber amount of about 5.0 to 8.0 mm), the ratio of the land width as described above By realizing the above, the shoulder main groove 4 can be set substantially at the position of the dynamic load radius of the tire 1. As a result, when the tire rolls, with the shoulder main groove 4 as a boundary, a larger driving force due to the tire rotation radius can be applied to the center block 9 and a larger braking force can be applied to the shoulder block 10. it can. In a preferred embodiment, a single driving force and braking force can be applied to each of the blocks 9 and 10, respectively. Accordingly, the torsional torque generated in each block 9 and 10 is further increased.

  As described above, the pneumatic tire 1 of the present invention can generate a larger residual CF and can control the single flow of the tire in an intended direction. Further, since the twisting torque m acting on each of the blocks 9 and 10 is in the same direction, the deformation of the block is also in the same direction, which helps to prevent uneven wear due to the direction of the twisting torque. In addition, from the tire equator to the outer side in the tire axial direction, at a position 25% apart from the width of the belt layer (not shown) arranged on the outer side in the tire radial direction of the carcass as a tire constituent member, in particular, the belt ply having the smallest width. Since a position separated by 25% of the width is generally a boundary position for drive control, the twist torque m can be more effectively maximized by providing the shoulder main groove 4 at this position.

  Here, if the angle θ1 of the center lateral groove 7 is less than 35 degrees or the angle θ2a of the inner portion 8a of the shoulder lateral groove 8 is less than 20 degrees, a sufficiently large torsion torque m cannot be generated, and the residual CF is Get smaller. On the contrary, when the angle θ1 exceeds 55 degrees or the angle θ2a exceeds 40 degrees, the lateral rigidity of the center block 9 and the shoulder block 10 is remarkably lowered, and the uneven wear resistance performance is deteriorated. From such a viewpoint, the angle θ1 is preferably 40 degrees or more, and preferably 50 degrees or less. The angle θ2a is preferably 25 degrees or more, and preferably 35 degrees or less.

  Further, when the width Wc of the center land portion 5 in the tire axial direction is less than 0.65 times or larger than 0.75 times the width Ws of the shoulder land portion 6 in the tire axial direction, it acts on the blocks 9 and 10. Driving force and braking force to be reduced, and residual CF is also reduced. The width Wc of the center land portion 5 in the tire axial direction is preferably 0.67 to 0.73 times the width Ws of the shoulder land portion 6 in the tire axial direction.

  Further, if the angle θ2b of the outer portion 8b of the shoulder lateral groove 8 exceeds 10 degrees, the rigidity on the tread grounding end Te side of the shoulder land portion 6 on which a large braking force acts is reduced, and the uneven wear resistance performance is deteriorated. Smooth drainage due to centrifugal force during turning is suppressed, and drainage performance deteriorates. From such a viewpoint, the angle θ2b is preferably set to 8 degrees or less while being inclined in the same direction as the inner portion 8a.

  Furthermore, in the tire 1 of the present invention, as shown in FIG. 1, the communication position K1 of the center lateral groove 7 to the shoulder main groove 4 is the same as the communication position K2 of the shoulder lateral groove 8 to the shoulder main groove 4 and the tire circumferential direction. Is misaligned. The positional deviation amount L is set to 0.3 to 0.5 times the separation pitch P of the shoulder lateral groove 8.

  With the above configuration, the central portion of the outer side edge 9e of the center block 9 having high rigidity faces the apex portion 10a on the inner side in the tire axial direction of the shoulder block 10 having low rigidity through the shoulder main groove 4. Similarly, the central portion of the inner side edge 10e of the shoulder block 10 having high rigidity faces the apex portion 9a on the outer side in the tire axial direction of the center block 9 having low rigidity via the shoulder main groove 4. As a result, the rigidity of the pattern portion formed by both blocks 9, 10 is made uniform and improved in the tire circumferential direction. This is useful for suppressing the occurrence of uneven wear. Further, by shifting the groove communication positions K1 and K2, even when the blocks 9 and 10 are simultaneously twisted in the same direction, it is possible to prevent the groove volume of the shoulder main groove 4 from being locally reduced at the communication position. It can prevent the deterioration of drainage performance. Furthermore, by setting the positional shift amount L in the above-described range, a part of the air passing through the center main groove 3 passes through the center lateral groove 7 and collides with the inner side edge 10e of the shoulder block 10. Besides being absorbed and reduced, the air column flow in the shoulder main groove 4 is disturbed to improve the noise performance. In order to effectively exhibit such an effect, the positional shift amount L is more preferably 0.4 times or more of the separation pitch P.

  As described above, the tire 1 of the present invention limits the ratio of the widths Wc and Ws between the center land portion 5 and the shoulder land portion 6 and limits the angle and position of the center lateral groove 7 and the shoulder lateral groove 8. As a result, the residual CF generated in the center block 9 and the shoulder block 10 is increased, and the one-sided flow of the tire can be controlled in an intended direction, and the uneven wear resistance performance, drainage performance and noise performance are improved in a well-balanced manner. .

  As shown in FIG. 2, since the tire according to the present embodiment has a point-symmetric pattern, the center lateral grooves 7A and 7B on both sides of the tire equator C are both inclined in the same direction (downward in this example). . Similarly, the shoulder lateral grooves 8 on both sides of the tire equator C are both inclined in the same direction (in this example, upward to the right). In such a pattern, as schematically shown in FIG. 3, for example, the torsional torque m in the same direction can be generated in all the blocks regardless of the rotation direction.

  The center block 9 may be provided with one center sub-groove 12 extending in the tire circumferential direction. Since the center sub-groove 12 of this embodiment is linear, the drainage performance is improved. The center sub-groove 12 divides the center block 9 into an outer center block portion 15 outside the tire axial direction and an inner center block portion 16 inside the tire axial direction.

  The center sub-groove 12 is disposed at a position where the groove center line 12G is separated from the groove edge 3e of the center main groove 3 by a distance Lc of 35 to 55% of the width Wc of the center land portion 5 outward in the tire axial direction. Is desirable. When the center sub-groove 12 approaches the inner side in the tire axial direction, the wear tends to concentrate on the center inner block portion 16, and conversely, when the center sub-groove 12 approaches the outer side in the tire axial direction, the outer center block portion 15 wears. It becomes easier to concentrate.

  The groove depth D5 (not shown) of the center sub-groove 12 is preferably smaller than the groove depth D2 of the shoulder main groove 4. Such a center sub-groove 12 ensures a large rigidity of the center block 9. However, if the groove depth D5 is excessively small, the drainage performance may be deteriorated. Thereby, the groove depth D5 of the center sub-groove 12 is preferably 20% or more of the groove depth D2, more preferably 30% or more, and preferably 80% or less. From the same viewpoint, the groove width W5 of the center sub-groove 12 is preferably 1.0 mm or more, more preferably 1.5 mm or more, and preferably 3.0 mm or less, more preferably 2.5 mm or less.

  Each center block 9 is provided with one center lug groove 17. The center lug groove 17 has an outer end 17 e in the tire axial direction communicating with the shoulder main groove 4 and an inner end 17 i in the tire axial direction terminating without communicating with the center main groove 3. In the present embodiment, the inner end 17 i of the center lug groove 17 is located on the inner side in the tire axial direction than the center sub-groove 12. For this reason, the center outer block portion 15 is divided into a first center outer block piece 15A formed on one side in the tire circumferential direction and a second center outer block piece 15B formed on the other side in the tire circumferential direction. Since the center lug groove 17 can discharge the drainage water in the center sub-groove 12 to the shoulder main groove 4 side, the drainage performance can be improved.

  Further, the center lug groove 17 of the present embodiment is arranged at a substantially intermediate position in the tire circumferential direction of the center block 9 and extends in the same direction as the center lateral groove 7. Such a center lug groove 17 exerts its edge effect, increases the residual CF, and helps to ensure the rigidity of the center block 9 and maintain uneven wear resistance. Further, the rigidity balance between the first center outer block piece 15A and the second center outer block piece 15B is ensured, and the uneven wear resistance performance is maintained high. The “substantially intermediate position” refers to a mode in which the groove center line 17G of the center lug groove 17 is arranged at an intermediate position in the tire circumferential direction of the center block 9, and the tire circumferential direction of the center block 9 from the intermediate position. The groove center line 17G is disposed within ± 10% of the length L5.

  Further, the length L4 of the center lug groove 17 in the tire axial direction is preferably 70% or more, more preferably 75% or more of the width Wc of the center land portion 5, and preferably 90% or less, more preferably. 85% or less is desirable. As a result, the residual CF can be further increased while preventing the rigidity of the center block 9 from being lowered.

  The groove width W6 and the groove depth D6 (not shown) of the center lug groove 17 are preferably 1.5 mm or more, more preferably from the viewpoint of achieving both rigidity and drainage performance of the center block 9. 2.0 mm or more is desirable, preferably 3.5 mm or less, more preferably 3.0 mm or less. Further, the groove depth D6 is preferably 50% or more of the groove depth D2 of the shoulder main groove 4, more preferably 60% or more, and preferably 90% or less, more preferably 80% or less. .

  The shoulder block 10 may be provided with one shoulder sub-groove 11 extending in the tire circumferential direction. Thus, the shoulder block 10 is divided into a shoulder outer block portion 13 on the outer side in the tire axial direction and a shoulder inner block portion 14 on the inner side in the tire axial direction. Since the shoulder sub-groove 11 of this embodiment is linear, the drainage performance is improved.

  Further, the shoulder sub-groove 11 has a groove center line 11G having a distance Ls of 25 to 45% of the width Ws of the shoulder land portion 6 from the outer groove edge 4e of the shoulder main groove 4 in the tire axial direction. It is desirable to be arranged at a position separated outward. When the shoulder minor groove 11 approaches the inner side in the tire axial direction, the wear tends to concentrate on the shoulder inner block portion 14, and conversely, when the shoulder minor groove 11 approaches the outer side in the tire axial direction, the outer shoulder block portion 13 wears. It becomes easier to concentrate. Further, in order to ensure a large lateral rigidity of the shoulder outer block portion 13 where a large lateral force acts during turning, the groove center line 11G is preferably disposed on the tire equator C side.

  Further, the groove depth D7 (not shown) of the shoulder sub-groove 11 is preferably smaller than the groove depth D2 of the shoulder main groove 4. Such a shoulder sub-groove 11 can ensure a large block rigidity of the shoulder block 10. However, if the groove depth D7 is excessively small, the drainage performance may be deteriorated. Thereby, the groove depth D7 of the shoulder sub-groove 11 is preferably 20% or more of the groove depth D2, more preferably 30% or more, and preferably 80% or less. From the same viewpoint, the groove width W7 of the shoulder sub-groove 11 is preferably 1.0 mm or more, more preferably 1.5 mm or more, and preferably 3.0 mm or less, more preferably 2.5 mm or less.

  Further, the shoulder outer block portion 13 includes a shoulder outer lug groove 18 that extends from the outer side in the tire axial direction of the tread ground end Te toward the inner side in the tire axial direction and terminates without reaching the shoulder sub-groove 11. However, a plurality (two in this embodiment) are provided in the tire circumferential direction.

  Further, the shoulder inner block portion 14 has an inner end 19i in the tire axial direction that opens into the shoulder main groove 4 and an outer end 19e in the tire axial direction that terminates without communicating with the shoulder sub-groove 11. A plurality of 19 (two in the present embodiment) 19 are provided apart from each other in the tire circumferential direction. Further, the shoulder inner block portion 14 is provided with a shoulder inner joint groove 20 that joins the shoulder inner lug grooves 19 and 19 spaced in the tire circumferential direction.

  Such an outer shoulder lug groove 18 and an inner shoulder lug groove 19 exert an edge effect and further help to improve the residual CF. Further, it is desirable that the shoulder outer lug groove 18 and the shoulder inner lug groove 19 are inclined in the same direction as the shoulder lateral groove 8 and arranged at substantially the same angle in order to maintain the rigidity of the shoulder block 10 high.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the illustrated embodiments, and can be implemented in various forms.

Pneumatic tires (size: 195 / 65R15) having the pattern of FIG. 1 and based on the specifications in Table 1 were manufactured and tested for their respective performance. The common specifications are as follows.
Tread contact width: 130mm
<Center main groove>
Groove width W1 / Tread contact width TW: 4.6%
Groove depth D1: 7.0 mm
Angle relative to tire equator C: 0 degree <shoulder main groove>
Groove width W2 / tread contact width TW: 6.0%
Groove depth D2: 8.0 mm
Angle relative to tire equator C: 0 degrees <Center lateral groove>
Groove width W3: 2.5mm
Groove depth D3: 6.0 mm
<Shoulder lateral groove>
Groove width W4: 3.5mm
Groove depth D4: 6.0 mm
<Center sub-groove (not provided in Example 5)>
Groove width W5: 2.0mm
Groove depth D5 / D2: 63%
<Center lug groove>
Groove width W6: 2.5mm
Groove depth D6 / D2: 63%
Tire axial length L4 / Wc: 80%
<Shoulder minor groove (not provided in Example 4)>
Groove width W7: 2.5mm
Groove depth D7 / D2: 63%
The test method is as follows.

<Noise performance>
A sample tire is mounted on all wheels of a vehicle (domestic 1800cc, FF vehicle) under the conditions of a rim (6JJ) and internal pressure (200kPa), and the road noise measurement path (asphalt rough road) is run at a speed of 60km / h. The noise in the car was collected with a microphone installed at the driver's seat side ear position, and the sound pressure level of the peak value of the air column resonance sound in the narrow band around 240 Hz was measured. Evaluation is indicated by an index with Comparative Example 1 being 100, and the larger the value, the better.

<Uneven wear resistance>
Using the test vehicle, the tire test course was run for 30 km by limit running, and the presence or absence of block chipping or uneven wear was visually observed. Evaluation is indicated by an index with Comparative Example 1 being 100, and the larger the value, the better the uneven wear resistance.

<Drainage performance>
In the above test vehicle, on the asphalt road surface with a radius of 100 m, on the course where a puddle with a depth of 10 mm and a length of 20 m was provided, the vehicle was entered while increasing the speed stepwise, and the lateral acceleration (lateral G) was measured. The average lateral G of the front wheels at a speed of 50 to 80 km / h was calculated. The results were expressed as an index with Comparative Example 1 as 100. The larger the value, the better.

<Pattern effect of price tear residual cornering force>
Each test tire was tested by running it on a flat belt machine at a speed of 10 km / H and a load of 4.0 kN according to JASO C607. The result is the difference between the average value of the measured values of 20 test tires and the average value of the measured values of 20 plain tires without grooves. The larger the numerical value, the better, for example, because it is possible to effectively suppress the single flow of the tire with respect to the road surface cant.
The test results are shown in Table 1.

  As a result of the test, it can be confirmed that the tires of the examples have improved various performances as compared with the comparative examples.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Center main groove 4 Shoulder main groove 5 Center land part 5A Center block 6 Shoulder land part 6A Shoulder block 7 Center horizontal groove 8 Shoulder horizontal groove 8a Inner part of shoulder horizontal groove 8b Outer part of shoulder horizontal groove C Tire equator K1 Communication position of the center lateral groove to the shoulder main groove K2 Communication position of the shoulder lateral groove to the shoulder main groove P Separation pitch Te of the shoulder lateral groove Te Tread grounding end

Claims (4)

The tread portion is provided with one center main groove extending continuously on the tire equator in the tire circumferential direction and a pair of shoulder main grooves extending continuously on both sides of the center main groove in the tire circumferential direction. A pneumatic tire comprising a pair of center land portions extending between the center main groove and the shoulder main grooves, and a pair of shoulder land portions formed outside the shoulder main grooves,
The center land portion and the shoulder land portion are each divided into a plurality of center blocks and shoulder blocks by a center lateral groove and a shoulder lateral groove that are spaced apart in the tire circumferential direction, respectively.
The center lateral groove is inclined at an angle of 35 to 55 degrees with respect to the tire axial direction,
An inner portion of the shoulder lateral groove in the tire axial direction is inclined in a direction opposite to the center lateral groove, communicates with the shoulder main groove at an angle of 20 to 40 degrees with respect to the tire axial direction, and is outside the shoulder lateral groove. The part opens at an angle of 10 degrees or less with respect to the tire axial direction at the tread ground contact end,
The width Wc in the tire axial direction of the center land portion is 0.65 to 0.75 times the width Ws in the tire axial direction of the shoulder land portion,
In addition, the communication position of the center lateral groove to the shoulder main groove is shifted in the tire circumferential direction from the communication position of the shoulder lateral groove to the shoulder main groove, and the amount of displacement is 0 of the separation pitch of the shoulder lateral groove. A pneumatic tire characterized by being 3 to 0.5 times larger.   In the shoulder block, a tire having a groove depth smaller than that of the shoulder main groove at a position separated by 25 to 45% of the width of the shoulder land portion from the outer groove edge in the tire axial direction of the shoulder main groove. The pneumatic tire according to claim 1, wherein a shoulder sub-groove extending in a circumferential direction is provided.   In the center block, a position that is 35 to 55% of the width of the center land portion is separated from the groove edge of the center main groove to the outer side in the tire axial direction with a groove depth smaller than that of the shoulder main groove. The pneumatic tire according to claim 1, wherein a center sub-groove extending in a direction is provided.   The center block has a center that terminates in a substantially intermediate position in the tire circumferential direction with an outer end in the tire axial direction communicating with the shoulder main groove and an inner end in the tire axial direction not communicating with the center main groove. The pneumatic tire according to any one of claims 1 to 3, wherein a lug groove is provided.

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