JP6565559B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  In the pneumatic tire, a groove is formed on the tread surface mainly in order to ensure drainage, and this groove is formed in consideration of various requirements during traveling of the vehicle. For example, in the pneumatic tires described in Patent Literature 1 and Patent Literature 2, in order to achieve both on-snow performance and wet performance, or to reduce pattern noise, the pneumatic tire extends in the tire circumferential direction at the center in the tire width direction. A circumferential groove is provided, and lug grooves extending in the tire width direction while being curved in the tire circumferential direction are formed on both sides of the circumferential groove in the tire width direction.

JP 2013-230709 A JP-A-8-2217

  Here, paying attention to steering stability, which is one of the functions required for pneumatic tires, it is effective to reduce the tread surface groove area and increase the ground contact area. As a result, the wet performance deteriorates. As described above, since steering stability and wet performance are functions that are contradictory to each other in a pneumatic tire, it has been very difficult to achieve both of them.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can make steering stability and wet performance compatible.

  In order to solve the above-described problems and achieve the object, a pneumatic tire according to the present invention is a pneumatic tire in which a mounting direction (inside / outside) with respect to a vehicle is defined, and extends in the tire circumferential direction and is tread. A circumferential groove located on the inner side in the vehicle width direction from the tire equator line on the surface and a plurality of grooves arranged on the tread surface, and the depth varies depending on the position in the longitudinal direction, and the depth at the center in the longitudinal direction. A narrow groove that is deepest and has a shallowest depth at at least one end, and the narrow groove is located on the outer side in the vehicle width direction with respect to the circumferential groove, and between the tire width direction and the tire circumferential direction. A first narrow groove that is inclined with respect to both sides, is located on the outer side in the vehicle width direction with respect to the circumferential groove and is inclined with respect to both the tire width direction and the tire circumferential direction; A second narrow groove whose tilt direction is opposite to the tilt direction of the first narrow groove, the first narrow groove intersecting at least two of the second narrow grooves, and the second narrow groove The narrow groove intersects with at least two of the first narrow grooves, and is incorporated in a specified rim, filled with a specified internal pressure and loaded with a specified load, and the groove area ratio in the contact surface is 20% or less. Features.

  Moreover, in the pneumatic tire, the first narrow groove has one end terminated in the tread surface, and the other end straddles the grounding end located on the outer side in the vehicle width direction among the grounding ends in the tire width direction, It is preferable that one end of the second narrow groove terminates in the tread surface and the other end opens in the circumferential groove.

  Further, in the pneumatic tire, the first narrow groove is formed with a curvature, and an end portion of the end side near the circumferential groove is located on the outer side in the vehicle width direction with respect to the tire circumferential direction. It is preferable that the angle is smaller than the angle with respect to the tire circumferential direction on the side.

  Further, in the pneumatic tire, the second narrow groove is formed with a curvature, and an end portion of the end portion near the circumferential groove is located on the outer side in the vehicle width direction with respect to the tire circumferential direction. It is preferable that the angle is larger than the angle with respect to the tire circumferential direction on the side.

  Further, in the pneumatic tire, of the plurality of block portions formed on the tread surface and at least partially partitioned by the narrow grooves, one end of the block portion adjacent to the circumferential groove is the narrow portion. It is preferable that a shallow groove having an opening in the groove and the other end opening in the circumferential groove is formed.

  In the pneumatic tire, among the plurality of block portions formed on the tread surface and at least partially partitioned by the narrow grooves, one end of the block portion through which the ground contact end in the tire width direction passes is It is preferable that a shallow groove opening in the narrow groove and having the other end straddling the grounding end is formed.

  Further, in the pneumatic tire, the block portions where the shallow grooves are formed are arranged between the block portions where the shallow grooves are formed, so that the block portions where the shallow grooves are formed are arranged between the block portions. It is preferable that they are separated.

  Further, in the pneumatic tire, the narrow groove is located on the inner side in the vehicle width direction than the circumferential groove and is inclined with respect to both the tire width direction and the tire circumferential direction, and one end thereof is the circumferential direction. A third narrow groove that opens in the groove, is located on the inner side in the vehicle width direction than the circumferential groove and is inclined with respect to both the tire width direction and the tire circumferential direction, and the inclination direction with respect to the tire circumferential direction is And a fourth narrow groove straddling the ground contact end located in the vehicle width direction among the ground contact ends in the tire width direction. It is preferable that the fourth narrow grooves are alternately arranged in the tire circumferential direction.

  Further, in the pneumatic tire, the narrow groove has a groove width that is narrower from the opening toward the groove bottom, and the groove width on the opening side is the widest at the center in the longitudinal direction, It is preferable that it becomes the narrowest at least at one end.

  Further, in the pneumatic tire, the narrow groove is formed with a chamfer whose chamfer width varies depending on the position in the longitudinal direction at the opening, and the chamfer width is the widest at the center in the longitudinal direction, and at least one of the chamfer widths It is preferable that it becomes the narrowest at the end.

  The pneumatic tire according to the present invention has an effect that both steering stability and wet performance can be achieved.

FIG. 1 is a meridional cross-sectional view showing a main part of a pneumatic tire according to an embodiment. FIG. 2 is an AA arrow view of FIG. FIG. 3 is a schematic cross-sectional view for explaining the groove depth of the first narrow groove shown in FIG. FIG. 4 is a schematic cross-sectional view for explaining the groove depth of the second narrow groove shown in FIG. FIG. 5 is a detailed plan view of the narrow groove shown in FIG. 6 is a cross-sectional view taken along line BB in FIG. FIG. 7 is a modification of the pneumatic tire according to the embodiment, and is a detailed plan view of a narrow groove. 8 is a cross-sectional view taken along the line CC of FIG. FIG. 9A is a chart showing the results of the performance test of the pneumatic tire according to the embodiment. FIG. 9B is a chart showing the results of the performance test of the pneumatic tire according to the embodiment.

  Hereinafter, an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  In the following description, the tire width direction refers to a direction parallel to the rotation axis of the pneumatic tire, the inner side in the tire width direction is the direction toward the tire equator line in the tire width direction, and the outer side in the tire width direction is The direction opposite to the direction toward the tire equator line in the tire width direction. The tire radial direction means a direction orthogonal to the tire rotation axis, the tire radial inner direction means the direction toward the tire rotation axis in the tire radial direction, and the tire radial direction outer direction means that the tire rotates in the tire radial direction. The direction away from the axis. Further, the tire circumferential direction refers to a direction rotating around the tire rotation axis.

  FIG. 1 is a meridional cross-sectional view showing a main part of a pneumatic tire according to an embodiment. Here, the pneumatic tire 1 shown in FIG. 1 defines a mounting direction with respect to the vehicle, that is, a direction when the vehicle is mounted. The pneumatic tire 1 also has a mounting direction display unit (not shown) that indicates a mounting direction with respect to the vehicle. The mounting direction display part is configured by, for example, marks or irregularities attached to the sidewall part of the tire. For example, ECER30 (European Economic Commission Regulation Article 30) obligates the installation of a mounting direction display section on the side wall that is on the outer side in the vehicle width direction when the vehicle is mounted. The pneumatic tire 1 has a tread portion 2 disposed in the outermost portion in the tire radial direction when viewed from the meridional section, and the surface of the tread portion 2, that is, the pneumatic tire 1 is mounted. A portion that comes into contact with the road surface when the vehicle (not shown) travels is formed as a tread surface 3. Further, a sidewall portion 16 is disposed from the end portion of the tread portion 2 in the tire width direction to a predetermined position on the inner side in the tire radial direction. That is, the sidewall portions 16 are disposed at two locations on both sides of the pneumatic tire 1 in the tire width direction.

  Further, the bead portions 10 are located on the inner side in the tire radial direction of the respective sidewall portions 16, and the bead portions 10 are arranged at two positions on both sides of the tire equator line 5, similarly to the sidewall portions 16. It is installed. Each bead portion 10 is provided with a bead core 11, and a bead filler 12 is provided outside the bead core 11 in the tire radial direction.

  A plurality of belt layers 14 are provided on the inner side of the tread portion 2 in the tire radial direction. The belt layer 14 is provided by laminating a plurality of cross belts 141 and 142 and a belt cover 143. Among them, the cross belts 141 and 142 are formed by rolling a plurality of belt cords made of steel or organic fiber material with a coating rubber and having a belt angle of 20 ° to 55 ° in absolute value. Composed. Further, the plurality of cross belts 141 and 142 have different belt cords defined as the inclination angles of the fiber direction of the belt cord with respect to the tire circumferential direction, and are laminated by crossing the fiber directions of the belt cords. It is configured as a so-called cross-ply structure. The belt cover 143 is formed by rolling a plurality of cords made of steel coated with a coat rubber or an organic fiber material, and has a belt angle of 0 ° to 10 ° in absolute value. The belt cover 143 is disposed so as to be laminated on the outer side in the tire radial direction of the cross belts 141 and 142.

  A carcass layer 13 containing a radial ply textile cord is continuously provided on the inner side in the tire radial direction of the belt layer 14 and on the tire equator line 5 side of the sidewall portion 16. The carcass layer 13 has a single-layer structure composed of a single carcass ply or a multilayer structure formed by laminating a plurality of carcass plies, and has a toroidal shape between bead cores 11 disposed on both sides in the tire width direction. It is bridged to form the tire skeleton. Specifically, the carcass layer 13 is disposed from one bead portion 10 to the other bead portion 10 among the bead portions 10 located on both sides in the tire width direction, and wraps the bead core 11 and the bead filler 12. The bead portion 10 is wound back along the bead core 11 outward in the tire width direction. The carcass ply of the carcass layer 13 is formed by rolling a plurality of carcass cords made of steel, or organic fiber materials such as aramid, nylon, polyester, rayon, etc. with a coat rubber, and with respect to the tire circumferential direction. The carcass angle, which is the inclination angle of the fiber direction of the carcass cord, is formed to be 80 ° to 95 ° in absolute value.

  A rim cushion rubber 17 constituting a contact surface of the bead portion 10 with respect to the rim flange is disposed on the inner side in the tire radial direction and the outer side in the tire width direction of the rewind portion of the bead core 11 and the carcass layer 13 in the bead portion 10. An inner liner 15 is formed along the carcass layer 13 on the inner side of the carcass layer 13 or on the inner side of the carcass layer 13 in the pneumatic tire 1.

  FIG. 2 is an AA arrow view of FIG. One tread groove 30 extending in the tire circumferential direction is formed on the tread surface 3 of the tread portion 2. The circumferential groove 30 is located on the inner side in the vehicle mounting direction than the tire equator line 5 on the tread surface 3. That is, the pneumatic tire 1 according to the present embodiment has a tire width direction orientation when being mounted on the vehicle, and the circumferential groove 30 is a tire equator line when the pneumatic tire 1 is mounted on the vehicle. It is arrange | positioned rather than 5 in the vehicle width direction. Note that the circumferential groove 30 does not have to be located entirely in the vehicle width direction with respect to the tire equator line 5, and a part of the circumferential groove 30 is on the tire equator line 5. May be. The circumferential groove 30 only needs to be positioned on the inner side in the vehicle width direction of the tire equator line 5 with respect to the center of the circumferential groove 30 in the tire width direction.

  The circumferential groove 30 has a groove width of 8% or more and 15% or less with respect to the ground contact width, and a groove depth of 6.0 mm or more and 12.0 mm or less. The circumferential groove 30 is disposed in the tire width direction from the tire equator line 5 to the inner grounding end Ein, which is the grounding end E located on the inner side in the vehicle width direction of the grounding end E. It is preferable to be disposed at a position within the range of 25% to 65% from the tire equator line 5 when Win is set to 100%.

  In this case, the ground contact width is determined by attaching the pneumatic tire 1 to a specified rim, a specified internal pressure, for example, an internal pressure condition of air pressure corresponding to a specified load, and a specified load, for example, a condition of 75% load of the maximum load capacity. The longest straight distance between the ground contact ends E in the tire width direction on the ground contact surface formed on the flat plate when loaded in the vertical direction on the flat plate.

  The specified rim refers to “applied rim” defined in JATMA, “Design Rim” defined in TRA, or “Measuring Rim” defined in ETRTO. The specified internal pressure refers to the “maximum air pressure” specified in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified in TRA, or “INFLATION PRESSURES” specified in ETRTO. The specified load means “maximum load capacity” defined in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “LOAD CAPACITY” defined in ETRTO.

  The tread surface 3 is formed not only in a region corresponding to the ground contact surface but also in a portion outside the ground contact surface in the tire width direction, that is, the tread surface 3 extends inside and outside the ground contact end E in the tire width direction. Is formed. A plurality of narrow grooves 40 are formed in the tread surface 3 in the ground contact surface of the tread surface 3 or over the inside and outside of the ground contact surface of the tread surface 3. The plurality of narrow grooves 40 all have a maximum groove depth of 4.0 mm or more and 12.0 mm or less. The narrow groove 40 includes a first narrow groove 41 and a second narrow groove 42 that are located on the outer side in the vehicle width direction than the circumferential groove 30, and a third narrow groove 43 that is located on the inner side in the vehicle width direction with respect to the circumferential groove 30. A fourth narrow groove 44 is provided. Among these, the 1st narrow groove 41 inclines with respect to both a tire width direction and a tire circumferential direction, and is formed over the inside and outside of the contact surface in the tread surface 3. For this reason, one end of the first narrow groove 41 terminates in the tread surface 3, and the other end side has an outer grounding end Eout which is a grounding end E located outside the vehicle width direction among the grounding ends E in the tire width direction. It is formed straddling. The second narrow groove 42 is inclined with respect to both the tire width direction and the tire circumferential direction in the same manner as the first narrow groove 41, and the inclination direction with respect to the tire circumferential direction is the inclination direction of the first fine groove 41. It is in the opposite direction. One end of the second narrow groove 42 terminates in the tread surface 3, and the other end communicates with the circumferential groove 30 and opens in the circumferential groove 30. The end 56 of the second narrow groove 42 on the side terminating in the tread surface 3 may be located in the ground contact surface or may be located outside the ground contact surface in the tire width direction. That is, the second narrow groove 42 may be formed only in the grounding surface of the tread surface 3 or may be formed across the grounding surface across the inner grounding end Eout.

  The first narrow groove 41 has a shape inclined from the side where the outer ground contact end Eout on the tread surface 3 is located toward the side where the circumferential groove 30 is located, and also in the direction toward the tire circumferential direction. It is formed side by side in the direction. Further, the second narrow groove 42 has a shape inclined from the side where the circumferential groove 30 is located toward the side where the outer grounding end Eout is located and toward the tire circumferential direction. It is formed side by side. Further, the first narrow groove 41 and the second narrow groove 42 are the tire circumferential direction when the first narrow groove 41 is directed from the outer ground contact end Eout side to the circumferential groove 30 side, and the second narrow groove. The direction of the tire circumferential direction when 42 faces from the circumferential groove 30 side to the outer grounding end Eout side is the same direction. For this reason, the first narrow groove 41 and the second narrow groove 42 are inclined in directions opposite to each other with respect to the tire circumferential direction.

  Further, the end 56 on the side of the first narrow groove 41 that terminates in the tread surface 3 is more in the tire width direction than the end 56 on the side of the second narrow groove 42 that terminates in the tread surface 3. It is located at a position near the circumferential groove 30. That is, the plurality of first narrow grooves 41 and the second narrow grooves 42 are arranged side by side in the tire circumferential direction while having portions that are at the same position in the tire width direction. Therefore, the first fine groove 41 and the second fine groove 42 intersect each other, the first fine groove 41 intersects with at least two second fine grooves 42, and the second fine groove 42 It intersects with at least two first narrow grooves 41. In the present embodiment, the first narrow groove 41 intersects with the three second narrow grooves 42, and the second narrow groove 42 also intersects with the three first narrow grooves 41.

  Further, the first fine groove 41 and the second fine groove 42 that are inclined in the direction toward the tire circumferential direction while facing the tire width direction are both curved and formed with a curvature. Specifically, in the first narrow groove 41, the angle θ1 with respect to the tire circumferential direction on the end 56 side near the circumferential groove 30 is larger than the angle θ2 with respect to the tire circumferential direction on the end 56 side located on the outer side in the vehicle width direction. Is also curved in the direction of decreasing. Further, in the second narrow groove 42, the angle θ4 with respect to the tire circumferential direction on the end 56 side near the circumferential groove 30 is larger than the angle θ3 with respect to the tire circumferential direction on the end 56 side located on the outer side in the vehicle width direction. Curved in the direction. That is, the first narrow groove 41 and the second narrow groove 42 are angles θ2 and θ4 with respect to the tire circumferential direction of the end portion 56 on the side straddling the outer grounding end Eout or the side opened to the circumferential groove 30. Rather, the angles θ1 and θ3 with respect to the tire circumferential direction of the end portion 56 that terminates in the tread surface 3 are smaller.

  In addition, the narrow groove 40 with respect to the tire circumferential direction is a relative angle with respect to the tire circumferential direction of the tangent line of the narrow groove 40 in the vicinity of the end portion 56 in the curved narrow groove 40. Of the angles of the narrow grooves 40 with respect to the tire circumferential direction, θ1 and θ3 are 0 ° or more and 25 ° or less, and θ2 and θ4 are 20 ° or more and 60 ° or less.

  The region where the first fine groove 41 and the second fine groove 42 intersect on the tread surface 3 intersects the circumferential groove 30 on the tread surface 3 because the first fine groove 41 and the second fine groove 42 intersect. In addition, a plurality of block portions 21 defined by the narrow grooves 40 and the circumferential grooves 30 are provided on the outer side in the vehicle width direction. That is, the plurality of block portions 21 formed on the tread surface 3 are formed by being at least partially partitioned by the narrow grooves 40.

  Among the plurality of block portions 21, one end opens in the narrow groove 40 and the other end opens in the circumferential groove 30 in the circumferential groove side block portion 22 which is the block portion 21 adjacent to the circumferential groove 30. A plurality of shallow grooves 60 are formed. Similarly, among the plurality of block portions 21, the ground end-side block portion 23, which is the block portion 21 through which the outer ground end Eout passes, has one end that opens into the narrow groove 40 and the other end that is shallow across the outer ground end Eout. A groove 60 is formed. The shallow groove 60 has a groove width of 0.5 mm to 3.0 mm, and a groove depth of 1.0 mm to 5.0 mm.

  As described above, the block portions 21 in which the shallow grooves 60 are formed are intermittently disposed without adjacent the block portions 21 in which the shallow grooves 60 are formed. That is, one or more block portions 21 where the shallow grooves 60 are not formed are arranged between the block portions 21 where the shallow grooves 60 are formed, and thereby, the block portions 21 where the shallow grooves 60 are formed. Are separated.

  The first and second narrow grooves 41 and 42 of the narrow groove 40 are arranged on the outer side in the vehicle width direction than the circumferential groove 30 as described above, whereas the third and fourth narrow grooves 43 and 4 The narrow groove 44 is disposed on the inner side in the vehicle width direction than the circumferential groove 30. Among these, the third narrow groove 43 is inclined with respect to both the tire width direction and the tire circumferential direction, and one end opens into the circumferential groove 30 and the other end terminates in the tread surface 3. . The end 56 of the third narrow groove 43 on the side terminating in the tread surface 3 may be located in the ground contact surface or may be located outside the ground contact surface in the tire width direction. . That is, the third narrow groove 43 may be formed only in the grounding surface of the tread surface 3 or may be formed across the grounding surface across the inner grounding end Ein.

  The fourth narrow groove 44 is inclined with respect to both the tire width direction and the tire circumferential direction, and the inclination direction with respect to the tire circumferential direction is opposite to the inclination direction of the third fine groove 43, The tread surface 3 is formed across the ground contact surface. For this reason, the fourth narrow groove 44 straddles the inner grounding end Ein, and the end portion 56 located near the circumferential groove 30 is not connected to the circumferential groove 30 and terminates in the tread surface 3. As described above, the third fine grooves 43 and the fourth fine grooves 44 whose inclination directions with respect to the tire circumferential direction are opposite to each other are alternately arranged in the tire circumferential direction.

  Since at least one end of each of the third narrow groove 43 and the fourth narrow groove 44 is formed in the tread surface 3, the block portion 21 is located at the inner side in the vehicle width direction of the land portion 20 with respect to the circumferential groove 30. A rib 25 extending in the tire circumferential direction is formed on the inner side in the vehicle width direction than the circumferential groove 30.

  The third fine groove 43 and the fourth fine groove 44 are curved and have a curvature, and the third fine groove 43 that opens in the circumferential groove 30 opens in the circumferential groove 30. The second narrow groove 42 is disposed in a continuous position and is formed in a shape continuous with the second narrow groove 42. That is, the third fine groove 43 is formed in a shape that is continuous with the second fine groove 42 across the circumferential groove 30.

  As described above, the pneumatic tire 1 according to the present embodiment in which the circumferential groove 30 and the narrow groove 40 are formed on the tread surface 3 is assembled in a specified rim, filled with a specified internal pressure, and loaded with a specified load. The groove area ratio in the ground plane at is 20% or less. In this case, the groove area ratio is the ratio of the groove area to the total area of the ground plane and the groove area.

  FIG. 3 is a schematic cross-sectional view for explaining the groove depth of the first narrow groove shown in FIG. FIG. 4 is a schematic cross-sectional view for explaining the groove depth of the second narrow groove shown in FIG. Each narrow groove 40 is formed so that the depth varies depending on the position in the longitudinal direction. Specifically, the narrow groove 40 has the deepest depth at the central portion 55 in the longitudinal direction, the shallowest depth at at least one end portion 56, and the maximum depth at the central portion 55 is 4.0 mm. It is 12.0 mm or less. Note that the central portion 55 in this case does not indicate a single point but points to a predetermined range. Specifically, the central portion 55 extends from the center position in the longitudinal direction of the narrow groove 40 toward both end portions 56. Thus, it is in the range of 25% of the length of the narrow groove 40. That is, the central portion 55 is in a range of ± 25% from the center position in the longitudinal direction of the narrow groove 40.

  The narrow groove 40 whose depth varies depending on the position in the longitudinal direction is, for example, when the end portions 56 on both sides in the longitudinal direction of the first narrow groove 41 are terminated in the tread surface 3, As shown in FIG. 3, it is deepest near the central portion 55, and becomes shallower toward the end portions 56 on both sides, and the groove depth becomes the minimum depth at the position of the end portions 56.

  Further, when one end 56 is connected to the circumferential groove 30 as in the second narrow groove 42, the length from the connecting portion to the other end 56 is set to the second narrow groove 42. As shown in FIG. 4, the central portion 55 of the second narrow groove 42 is near the center of the length. The second narrow groove 42 becomes shallower from the vicinity of the central portion 55 toward the end portions 56 on both sides, and the groove depth is minimized at the position of the end portion 56 on the side terminating in the tread surface 3. Become. On the other hand, at the end 56 of the second narrow groove 42 on the side connected to the circumferential groove 30, the groove depth becomes a predetermined depth, and the second narrow groove 42 is connected to the circumferential groove 30. It is open to the circumferential groove 30 at the portion where it is present.

  FIG. 5 is a detailed plan view of the narrow groove shown in FIG. 6 is a cross-sectional view taken along line BB in FIG. The narrow groove 40 has a groove width Gw that decreases from the opening 50 toward the groove bottom 51. That is, the narrow groove 40 is formed in a substantially V shape when viewed in the longitudinal direction. Further, the narrow groove 40 has a groove width Gw on the opening 50 side that is widest at the central portion 55 in the longitudinal direction of the narrow groove 40 and is narrowest at least at one end portion 56. Thus, the groove width Gw on the side of the opening 50 that changes depending on the position of the narrow groove 40 in the longitudinal direction is such that the maximum groove width Gw near the central portion 55 of the narrow groove 40 is 0.5 mm or more and 7.0 mm or less. It has become.

  The narrow grooves 40 do not need to be formed so that the groove width Gw becomes narrower from the opening 50 toward the groove bottom 51 in all the narrow grooves 40, for example, the third narrow groove 43 and the fourth narrow groove 44. The groove width Gw may be substantially constant in the groove depth direction. The narrow groove 40 only needs to be formed such that at least the first narrow groove 41 and the second narrow groove 42 have a groove width Gw that decreases from the opening 50 toward the groove bottom 51. The narrow groove 40 may not be formed symmetrically with respect to the center in the groove width direction. For example, when viewed in the longitudinal direction, the narrow groove 40 and the center of the opening 50 in the groove width direction and the groove bottom 51 The center may be shifted in the groove width direction.

  When the pneumatic tire 1 configured as described above is mounted on a vehicle and travels, the pneumatic tire 1 rotates while the tread surface 3 positioned below the tread surface 3 is in contact with the road surface. On the other hand, only one circumferential groove 30 is formed on the tread surface 3, and the grooves other than the circumferential groove 30 formed on the tread surface 3 are only the narrow grooves 40 and the shallow grooves 60. . For this reason, the tread surface 3 has a large ground contact area, and the rigidity of the land portion 20 is also high, so that the steering stability during vehicle travel is high. Further, since the groove area ratio in the tread surface 3 is 20% or less, the tread surface 3 also has a large ground contact area, and the rigidity of the land portion 20 is increased, so that steering stability is improved.

  Further, when the vehicle lane is changed or cornered, a relatively large load is likely to be applied to a region on the outer side in the vehicle width direction on the tread surface 3, but the circumferential groove 30 is more in the vehicle width direction than the tire equator line 5. Arranged inside. For this reason, a large load is likely to be applied when the vehicle is traveling, the ground contact area on the outer side in the vehicle width direction is large, and the rigidity of the land portion 20 is high, so that the steering stability during vehicle traveling is higher. It has become.

  Further, since the narrow grooves 40 formed on the tread surface 3 intersect with two or more other narrow grooves 40, water between the ground contact surface and the road surface enters into the narrow grooves 40 when traveling in the rain. At this time, this water can be passed through the other narrow grooves 40 one after another. Thereby, drainage can be improved and wet performance can be improved. As a result, it is possible to achieve both steering stability and wet performance.

  Further, since the circumferential groove 30 is formed with a groove width within a range of 8% to 15% and a groove depth within a range of 6.0 mm to 12.0 mm with respect to the ground contact width, Performance and steering stability can be achieved. That is, when the groove width of the circumferential groove 30 is less than 8% of the ground contact width or the groove depth is less than 6.0 mm, the groove width is too narrow or the groove depth is too shallow. It becomes difficult to obtain sufficient drainage. Further, when the groove width of the circumferential groove 30 is larger than 15% of the ground contact width or the groove depth is deeper than 12.0 mm, the ground contact area is reduced or the rigidity of the land portion 20 is decreased. As a result, the steering stability may be reduced. On the other hand, in the present embodiment, the circumferential groove 30 has a groove width in the range of 8% to 15% with respect to the ground width, and a groove depth in the range of 6.0 mm to 12.0 mm. Since it is formed, the ground contact area and the rigidity of the land portion 20 can be ensured while ensuring sufficient drainage, and both drainage and steering stability can be achieved.

  Moreover, since the maximum groove depth is formed within the range of 4.0 mm or more and 12.0 mm or less, the narrow groove 40 can achieve both drainage performance and steering stability. That is, when the maximum groove depth of the narrow groove 40 is less than 4.0 mm, it is difficult to obtain sufficient drainage because the maximum groove depth is too shallow. Moreover, when the maximum groove depth of the narrow groove 40 is deeper than 12.0 mm, there exists a possibility that steering stability may fall because the rigidity of the land part 20 falls. On the other hand, in the present embodiment, the narrow groove 40 is formed within a range where the maximum groove depth is 4.0 mm or more and 12.0 mm or less. The rigidity of the portion 20 can be ensured, and both drainage and steering stability can be achieved.

  Moreover, since the 1st fine groove 41 which the fine groove 40 has straddles the outer side ground end Eout, the 1st fine groove 41 drains the water which entered the 1st fine groove 41 to the exterior from the outer side ground end Eout. be able to. Further, since the second narrow groove 42 of the narrow groove 40 is open to the circumferential groove 30, the second narrow groove 42 drains the water that has entered the second narrow groove 42 toward the circumferential groove 30. can do. As a result, water between the ground contact surface and the road surface can enter the first narrow groove 41 and the second narrow groove 42 one after another, and can be excluded from between the ground contact surface and the road surface. As a result, wet braking performance can be improved.

  Further, the first narrow groove 41 and the second narrow groove 42 are end portions opened to the outer grounding end Eout side and the circumferential groove 30 rather than the end portion 56 side which is terminated in the tread surface 3. Since the angle with respect to the tire circumferential direction is larger on the 56 side, the water in the first narrow groove 41 and the second narrow groove 42 can be drained more reliably. As a result, the wet performance can be improved more reliably.

  Further, since the angle θ1 of the first narrow groove 41 with respect to the tire circumferential direction on the end 56 side near the circumferential groove 30 is 0 ° or more and 25 ° or less, the pneumatic tire 1 rotates in the tire circumferential direction. When performing, the water between the ground surface and the road surface can be captured more reliably, and the drainage can be ensured. Similarly, since the angle θ3 with respect to the tire circumferential direction on the end 56 side located on the outer side in the vehicle width direction of the second narrow groove 42 is 0 ° or more and 25 ° or less, the pneumatic tire 1 is in the tire circumferential direction. When rotating, the water between the ground surface and the road surface can be captured more reliably, and the drainage can be ensured.

  In addition, the first narrow groove 41 has an angle θ2 with respect to the tire circumferential direction on the end 56 side located on the outer side in the vehicle width direction, which is 20 ° or more and 60 ° or less. Can be secured. That is, when the angle θ2 of the first narrow groove 41 is less than 20 °, there is a possibility that the rigidity of the block portion 21 in the vicinity of the ground contact end Eout becomes too low, which may cause uneven wear. is there. On the other hand, when the angle θ2 of the first narrow groove 41 is larger than 60 °, the angle with respect to the tire circumferential direction is too large, and there is a concern that the drainage performance may deteriorate. On the other hand, in this embodiment, the first narrow groove 41 has an uneven wear because the angle θ2 with respect to the tire circumferential direction on the end 56 side located on the outer side in the vehicle width direction is 20 ° or more and 60 ° or less. Drainability can be secured while suppressing the above. Similarly, since the angle θ4 with respect to the tire circumferential direction on the end 56 side near the circumferential groove 30 is also 20 ° or more and 60 ° or less, the second narrow groove 42 has a drainage performance while suppressing uneven wear. Can be secured.

  In addition, among the plurality of block parts 21 at least partially partitioned by the narrow grooves 40, one end of the circumferential groove side block part 22 opens into the narrow groove 40 and the other end opens into the circumferential groove 30. Since the shallow groove 60 is formed, the water in the narrow groove 40 can be drained more reliably toward the circumferential groove 30. Similarly, the grounding end side block portion 23 is also formed with a shallow groove 60 having one end opened to the narrow groove 40 and the other end straddling the outer grounding end Eout. It is possible to drain more reliably toward the outside in the direction. As a result, the wet performance can be improved more reliably.

  Further, since the block portions 21 where the shallow grooves 60 are not formed are arranged between the block portions 21 where the shallow grooves 60 are formed, the block portions 21 where the shallow grooves 60 are formed are separated from each other. The rigidity of the block portion 21 can be changed in the tire circumferential direction. As a result, pitch variations can be provided, and pattern noise during vehicle travel can be reduced.

  Moreover, since the shallow groove 60 is formed within a range where the groove width is 0.5 mm or more and 3.0 mm or less and a groove depth is within a range where the groove depth is 1.0 mm or more and 5.0 mm or less, drainage performance and steering stability are improved. It can be compatible with sex. That is, when the groove width of the shallow groove 60 is less than 0.5 mm or the groove depth is less than 1.0 mm, the groove width is too narrow or the groove depth is too shallow. It becomes difficult to get sex. In addition, when the groove width of the shallow groove 60 is larger than 3.0 mm or the groove depth is deeper than 5.0 mm, the ground contact area decreases or the rigidity of the block portion 21 decreases. There is a risk that the steering stability is lowered. On the other hand, in this embodiment, the shallow groove 60 is formed within a range where the groove width is 0.5 mm or more and 3.0 mm or less and a groove depth is 1.0 mm or more and 5.0 mm or less. Therefore, the ground contact area and the rigidity of the block portion 21 can be ensured while ensuring sufficient drainage, and both drainage and steering stability can be achieved.

  In addition, since the third fine groove 43 of the fine groove 40 has one end opened to the circumferential groove 30, the third fine groove 43 directs the water that has entered the third fine groove 43 toward the circumferential groove 30. Can be drained. Moreover, since the 4th fine groove 44 which the fine groove 40 has straddles the inner side ground end Ein, the 4th fine groove 44 drains the water which entered the 4th fine groove 44 to the exterior from the inner side ground end Ein. be able to. As a result, water between the ground contact surface and the road surface can enter the third narrow groove 43 and the fourth narrow groove 44 one after another, and can be excluded from between the ground contact surface and the road surface. As a result, wet braking performance can be improved.

  In addition, since the third narrow grooves 43 and the fourth narrow grooves 44 are formed in directions opposite to each other in the direction of inclination with respect to the tire circumferential direction and are alternately arranged in the tire circumferential direction, the rotational direction of the pneumatic tire 1 The difference in performance such as drainage can be reduced.

  The narrow groove 40 is formed so that the groove width Gw becomes narrower from the opening 50 toward the groove bottom 51, and the groove width Gw on the opening 50 side has a central portion 55 in the longitudinal direction of the narrow groove 40. Since it changes depending on the position in the longitudinal direction so that it is the widest and the narrowest at least at one end portion 56, the drainage can be improved while ensuring the rigidity of the block portion 21. That is, the narrow groove 40 can secure the rigidity of the block portion 21 by narrowing the groove width Gw on the groove bottom 51 side, and can increase the opening area by widening the groove width Gw on the opening portion 50 side. And drainage can be improved. As a result, wet braking performance can be improved while ensuring steering stability.

  Moreover, since the maximum groove width Gw by the side of the opening part 50 is in the range of 0.5 mm or more and 7.0 mm or less, the narrow groove 40 can achieve both drainage and steering stability. That is, when the maximum groove width Gw on the opening 50 side is less than 0.5 mm, it is difficult to obtain sufficient drainage because the maximum groove width Gw is too narrow. Further, when the maximum groove width Gw on the opening 50 side is larger than 7.0 mm, the rigidity of the block portion 21 is lowered, and thus the steering stability may be lowered. On the other hand, in this embodiment, since the maximum groove width Gw on the opening 50 side of the narrow groove 40 is not less than 0.5 mm and not more than 7.0 mm, the rigidity of the block portion 21 is increased while ensuring sufficient drainage. It can be ensured, and both drainage and steering stability can be achieved.

  In the pneumatic tire 1 according to the above-described embodiment, the narrow groove 40 is formed so that the groove width Gw becomes narrower from the opening 50 toward the groove bottom 51. However, the narrow groove 40 has a groove depth. The groove width Gw may be substantially constant in the direction of. In this case, the groove width Gw of the narrow groove 40 is preferably 0.5 mm or more and 3.0 mm or less. That is, when the groove width Gw of the narrow groove 40 is less than 0.5 mm, it is difficult to obtain sufficient drainage because the groove width Gw is too narrow. Further, when the groove width Gw of the narrow groove 40 is larger than 3.0 mm, there is a possibility that the steering stability may be lowered due to a decrease in the contact area or a decrease in the rigidity of the land portion 20. On the other hand, when the groove width Gw of the narrow groove 40 is in the range of 0.5 mm or more and 3.0 mm or less, the ground contact area and the rigidity of the land portion 20 are ensured while ensuring sufficient drainage. Can do. As a result, both drainage and steering stability can be achieved.

  Further, when the groove width Gw of the narrow groove 40 is constant, it is preferable to form a chamfer 58 in the opening 50 of the narrow groove 40. FIG. 7 is a modification of the pneumatic tire according to the embodiment, and is a detailed plan view of a narrow groove. 8 is a cross-sectional view taken along the line CC of FIG. When the chamfer 58 is formed in the narrow groove 40, the chamfer 58 preferably changes the chamfer width Cw depending on the position of the narrow groove 40 in the longitudinal direction. Specifically, the chamfering width Cw of the chamfer 58 is the largest at the central portion 55 in the longitudinal direction of the narrow groove 40 and the narrowest at at least one end portion 56. As described above, when the chamfering width Cw of the chamfer 58 is changed depending on the position of the narrow groove 40 in the longitudinal direction, the maximum chamfering width Cw near the central portion 55 of the narrow groove 40 is set to the groove width Gw of the narrow groove 40. It is preferably 80% or more and 400% or less. Further, the chamfering depth Cd of the chamfer 58 is preferably 50% or less of the groove depth Gd at that position in any position in the longitudinal direction of the narrow groove 40.

  The chamfer 58 of the narrow groove 40 does not need to be formed in all the narrow grooves 40. For example, the chamfer 58 is not formed in the third narrow groove 43 and the fourth narrow groove 44, and the first narrow groove 41 and the first narrow groove 40 are not formed. It may be formed only in the two narrow grooves 42.

  As described above, the groove width Gw of the narrow groove 40 is made constant and the chamfer 58 is formed in the narrow groove 40. The chamfer 58 has the chamfer width Cw that is the widest at the central portion 55 in the longitudinal direction of the narrow groove 40, By changing according to the position in the longitudinal direction so as to be the narrowest at least at one end portion 56, drainage can be improved while ensuring the rigidity of the block portion 21. That is, since the groove width Gw of the narrow groove 40 is not increased, the rigidity of the block portion 21 can be secured, and the substantial opening area can be increased by forming the chamfer 58 in the opening 50 of the narrow groove 40. , Drainage can be improved. As a result, wet braking performance can be improved while ensuring steering stability.

  Further, the chamfer 58 of the narrow groove 40 can achieve both drainage and steering stability by setting the maximum chamfer width Cw to 80% or more and 400% or less of the groove width Gw of the narrow groove 40. That is, when the maximum chamfering width Cw is less than 80% of the groove width Gw of the narrow groove 40, the maximum chamfering width Cw is too narrow, and it becomes difficult to obtain sufficient drainage. Further, when the maximum chamfering width Cw is larger than 400% of the groove width Gw of the narrow groove 40, the rigidity of the block portion 21 is lowered, and thus the steering stability may be lowered. On the other hand, the chamfer 58 of the narrow groove 40 is formed so that the maximum chamfer width Cw is 80% or more and 400% or less of the groove width Gw of the narrow groove 40, thereby ensuring sufficient drainage and blocking. The rigidity of the portion 21 can be ensured, and both drainage and steering stability can be achieved.

〔Example〕
FIG. 9A and FIG. 9B are charts showing the results of the performance test of the pneumatic tire according to the embodiment. Hereinafter, the performance evaluation test performed on the pneumatic tire 1 according to the comparative example and the pneumatic tire 1 according to the present invention will be described. The performance evaluation test was conducted for dry handling stability and wet braking performance.

  In these evaluation tests, a 195 / 65R15 91H size pneumatic tire 1 was assembled on a rim wheel of a 15 × 6J size JATMA standard rim, the air pressure was adjusted to 230 kPa, and the test was run on a domestic 2000cc passenger car. It was done by doing. As for the evaluation method of each test item, the dry steering stability was performed by driving a vehicle equipped with the pneumatic tire 1 to be evaluated and performing a feeling evaluation by the panel. The dry maneuvering stability is displayed with a score of 100 as Comparative Example 1 described later, and the larger the value, the better the dry maneuvering stability. The wet braking performance was evaluated by performing braking evaluation from an initial speed of 100 km / h on a flat road with a water depth of 1 mm. The wet braking performance is displayed with a score of Comparative Example 1 described later as 100, and the larger the numerical value, the better the wet braking performance.

  The evaluation test was performed with the three types of pneumatic tires 1 of Comparative Examples 1 to 3 and the six types of pneumatic tires 1 of Examples 1 to 6 which are the pneumatic tires 1 according to the present invention. The pneumatic tires 1 that perform the evaluation test all have one circumferential groove 30 on the tread surface 3 and a plurality of narrow grooves 40 in the outer region in the vehicle width direction. The pattern has a pitch number of 20 in the direction. Further, the narrow groove 40 has an angle θ1 of 10 ° with respect to the tire circumferential direction on the end 56 side of the first narrow groove 41 near the circumferential groove 30, and the tire circumferential direction on the end 56 side located on the outer side in the vehicle width direction. The angle θ2 with respect to the angle is 42 °. Among these pneumatic tires 1, in Comparative Example 1, the circumferential groove 30 is not offset in the tire width direction from the tire equator line 5, and in Comparative Example 2, the narrow grooves 40 do not intersect each other. In Comparative Example 3, the groove area ratio in the ground contact surface is 25%.

  On the other hand, in Examples 1 to 6, which are examples of the pneumatic tire 1 according to the present invention, the circumferential grooves 30 are all offset inward in the vehicle width direction with respect to the tire equator line 5, and the narrow grooves 40 intersect each other. The groove area ratio in the ground plane is 15%. Further, in the pneumatic tire 1 according to Examples 1 to 6, whether or not the narrow groove 40 is changed depending on the position in the longitudinal direction, whether or not the narrow groove 40 is V-shaped, Whether or not they intersect, whether or not one end of the narrow groove 40 is open to the ground end or the circumferential groove 30, and the presence or absence of the shallow groove 60 is different.

  As a result of performing an evaluation test using these pneumatic tires 1, as shown in FIGS. 9A and 9B, the pneumatic tires 1 of Examples 1 to 6 are compared to the pneumatic tires 1 of Comparative Examples 1 to 3. Thus, it was found that dry handling stability and wet braking performance were improved. That is, the pneumatic tires 1 of Examples 1 to 6 can achieve both steering stability and wet performance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Tread surface 5 Tire equator line 10 Bead part 13 Carcass layer 14 Belt layer 16 Side wall part 20 Land part 21 Block part 22 Circumferential groove side block part 23 Ground end side block part 25 Rib 30 circumference Directional groove 40 Fine groove 41 First fine groove 42 Second fine groove 43 Third fine groove 44 Fourth fine groove 50 Opening 51 Groove bottom 55 Central part 56 End part 58 Chamfer 60 Shallow groove E Grounding end Gw Groove width

Claims (10)

It is a pneumatic tire with a specified mounting direction with respect to the vehicle,
A circumferential groove extending in the tire circumferential direction and positioned on the inner side in the vehicle width direction from the tire equator line on the tread surface;
A plurality of grooves arranged on the tread surface, and the depth varies depending on the position in the longitudinal direction, and the depth is the deepest at the center in the longitudinal direction, and the depth is the shallowest at least at one end;
With
The narrow groove is
A first narrow groove that is located on the outer side in the vehicle width direction than the circumferential groove and is inclined with respect to both the tire width direction and the tire circumferential direction;
It is located on the outer side in the vehicle width direction than the circumferential groove and is inclined with respect to both the tire width direction and the tire circumferential direction, and the inclination direction with respect to the tire circumferential direction is opposite to the inclination direction of the first narrow groove. The second narrow groove to become,
Have
The first narrow groove intersects with at least two of the second narrow grooves,
The second narrow groove intersects with at least two of the first narrow grooves,
A pneumatic tire characterized in that a groove area ratio in the ground contact surface is 20% or less in a state in which a specified load is applied after being loaded into a specified rim and filled with a specified internal pressure. The first narrow groove has one end terminating in the tread surface, and the other end straddling the grounding end located on the vehicle width direction outside of the grounding end in the tire width direction,
The pneumatic tire according to claim 1, wherein one end of the second narrow groove terminates in the tread surface and the other end opens in the circumferential groove.   The first narrow groove is formed with a curvature, and an angle with respect to the tire circumferential direction on the end side near the circumferential groove is an angle with respect to the tire circumferential direction on the end side located on the outer side in the vehicle width direction. The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire is smaller.   The second narrow groove is formed with a curvature, and an angle with respect to the tire circumferential direction on the end side near the circumferential groove is an angle with respect to the tire circumferential direction on the end side located on the outer side in the vehicle width direction. The pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire is larger.   Of the plurality of block portions formed on the tread surface and at least partially partitioned by the narrow groove, the block portion adjacent to the circumferential groove has one end opened to the narrow groove and the other end The pneumatic tire according to any one of claims 1 to 4, wherein a shallow groove opening in the circumferential groove is formed.   Of the plurality of block portions formed on the tread surface and at least partially partitioned by the narrow groove, the block portion through which the ground contact end in the tire width direction passes has one end opened to the narrow groove and the other end The pneumatic tire according to any one of claims 1 to 5, wherein a shallow groove is formed with a side straddling the ground contact end.   The block portions where the shallow grooves are formed are separated from each other by disposing the block portions where the shallow grooves are not formed between the block portions where the shallow grooves are formed. 6. The pneumatic tire according to 6. The narrow groove is
A third narrow groove that is located on the inner side in the vehicle width direction than the circumferential groove and that is inclined with respect to both the tire width direction and the tire circumferential direction, and one end of which opens in the circumferential groove;
It is located in the vehicle width direction inner side than the circumferential groove and is inclined with respect to both the tire width direction and the tire circumferential direction, and the inclination direction with respect to the tire circumferential direction is opposite to the inclination direction of the third narrow groove Further, a fourth narrow groove straddling the ground contact edge located on the inner side in the vehicle width direction among the ground contact edges in the tire width direction,
Have
The pneumatic tire according to any one of claims 1 to 7, wherein the third narrow grooves and the fourth narrow grooves are alternately arranged in the tire circumferential direction.   The narrow groove has a groove width that narrows from the opening toward the groove bottom, and the groove width on the opening side is the widest at the center in the longitudinal direction and the narrowest at least at one end. The pneumatic tire according to any one of claims 1 to 8.   A chamfer whose chamfering width varies depending on a position in the longitudinal direction is formed in the opening in the narrow groove, and the chamfering width is widest at a central portion in the longitudinal direction and narrowest at at least one end. The pneumatic tire according to any one of 1 to 8.

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