JP2017197145A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire enhanced in on-ice brake performance of the tire.SOLUTION: A pneumatic tire comprises: land parts 31-33 each including a rib or multiple blocks on a tread surface. The land parts 31-33 comprise multiple types of recessed parts 8 (81, 82) having mutually different volumes derived from respective three-dimensional shapes mutually different in a depth direction, arranged in a ground contact surface. A volume ratio Vce of the recessed part 8 in a center area of the tread part, and a volume ratio Vsh of the recessed part 8 in a shoulder area of the tread part have a relation of Vce<Vsh.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of improving the braking performance on ice of the tire.

  In a general new tire, since chemicals adhere to the tread surface, there is a problem that the water absorption action and the edge action of the block at the initial stage of wear are small, and the braking performance on ice is low. For this reason, in recent studless tires, a configuration is adopted in which a plurality of shallow fine grooves are provided on the surface of the block. In such a configuration, the on-ice braking performance of the tire is improved by removing the water film in which the shallow groove is interposed between the ice road surface and the tread surface in the early stage of wear. As a conventional pneumatic tire employing such a configuration, a technique described in Patent Document 1 is known.

  Further, in recent studless tires, a configuration in which fine and numerous protrusions are formed on the tread surface is employed in order to improve tire performance on an icy road surface and a snowy road surface in the initial use of the tire. In such a configuration, the surface roughness of the tire ground contact surface is increased, and the air gap between the protrusions removes the water film interposed between the ice road surface and the tread surface, and the protrusions cause the road surface and the tread surface to be separated. The frictional force increases. Thereby, the performance on ice and the performance on snow when a tire is new are improved. As a conventional pneumatic tire employing such a configuration, a technique described in Patent Document 2 is known.

Japanese Patent No. 3702958 JP 2013-136346 A

  An object of the present invention is to provide a pneumatic tire capable of improving the braking performance on ice of the tire.

  In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire including a land portion having ribs or a plurality of blocks on a tread surface, wherein the land portions have three-dimensional shapes in mutually different depth directions. Having a plurality of types of recesses having different volumes on the ground contact surface, defining a ratio of the total volume of the recesses in a predetermined region and the contact area of the land portion as a volume ratio of the recesses, and The volume ratio Vce of the concave portion in the tread portion center region and the volume ratio Vsh of the concave portion in the tread portion shoulder region have a relationship of Vce <Vsh.

  In the pneumatic tire according to the present invention, the volume ratio Vsh of the recess in the tread shoulder region is set to be large, so that the water absorption of the tread surface in the tread shoulder region where a water film is easily generated is improved. As a result, the adhesion of the block tread to the icy road surface is improved, and there is an advantage that the braking performance on ice and the turning performance on ice are improved.

FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a plan view showing a tread surface of the pneumatic tire depicted in FIG. 1. FIG. 3 is an explanatory diagram illustrating a land portion of the pneumatic tire illustrated in FIG. 2. FIG. 4 is an enlarged view showing the tread of the block. FIG. 5 is an explanatory view showing a cross section in the depth direction of the recess. FIG. 6 is an explanatory diagram showing a land portion of the pneumatic tire depicted in FIG. 2. FIG. 7 is an explanatory diagram illustrating a land portion of the pneumatic tire illustrated in FIG. 2. FIG. 8 is an explanatory view showing the inner wall surface shape of the recess. FIG. 9 is an explanatory view showing the inner wall surface shape of the recess. FIG. 10 is an explanatory view showing the inner wall surface shape of the recess. FIG. 11 is an explanatory view showing the inner wall surface shape of the recess. FIG. 12 is an explanatory view showing the inner wall surface shape of the recess. FIG. 13 is a cross-sectional view in the depth direction of the narrow shallow grooves and the recesses. FIG. 14 is an explanatory view showing a modification of the tread of the block shown in FIG. FIG. 15 is an explanatory diagram illustrating a modification of the tread surface of the block illustrated in FIG. 4. FIG. 16 is an explanatory diagram illustrating a modified example of the tread surface of the block illustrated in FIG. 4. FIG. 17 is an explanatory diagram illustrating a modified example of the tread surface of the block illustrated in FIG. 4. FIG. 18 is an explanatory diagram illustrating a modification of the tread surface of the block illustrated in FIG. 4. FIG. 19 is an explanatory view showing a modification of the tread of the block shown in FIG. FIG. 20 is an explanatory diagram illustrating a modified example of the tread surface of the block illustrated in FIG. 4. FIG. 21 is an explanatory view showing a modification of the tread surface of the block shown in FIG. FIG. 22 is an explanatory view showing a modification of the tread of the block shown in FIG. FIG. 23 is an explanatory view showing a modification of the tread of the block shown in FIG. FIG. 24 is an explanatory diagram illustrating a modified example of the tread surface of the block illustrated in FIG. 4. FIG. 25 is an explanatory diagram illustrating a modified example of the tread surface of the block illustrated in FIG. 4. FIG. 26 is an explanatory diagram illustrating a modification of the tread surface of the block illustrated in FIG. 4. FIG. 27 is an explanatory view showing a modification of the tread of the block shown in FIG. FIG. 28 is an explanatory view showing a modified example of the pneumatic tire depicted in FIG. 2. FIG. 29 is an explanatory view showing a modified example of the pneumatic tire depicted in FIG. 2. FIG. 30 is an explanatory view showing a modified example of the pneumatic tire depicted in FIG. 2. FIG. 31 is an explanatory diagram showing a modification of the pneumatic tire depicted in FIG. 2. FIG. 32 is an explanatory view showing a modified example of the pneumatic tire depicted in FIG. 2. FIG. 33 is an explanatory diagram showing a modified example of the pneumatic tire depicted in FIG. 2. FIG. 34 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. The same figure has shown sectional drawing of the one-side area | region of a tire radial direction. The figure shows a radial tire for a passenger car as an example of a pneumatic tire.

  In the figure, the cross section in the tire meridian direction means a cross section when the tire is cut along a plane including a tire rotation axis (not shown). Reference sign CL denotes a tire equator plane, which is a plane that passes through the center point of the tire in the tire rotation axis direction and is perpendicular to the tire rotation axis. Further, the tire width direction means a direction parallel to the tire rotation axis, and the tire radial direction means a direction perpendicular to the tire rotation axis.

  The pneumatic tire 1 has an annular structure centered on the tire rotation axis, and includes a pair of bead cores 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, and a tread rubber 15. And a pair of sidewall rubbers 16 and 16 and a pair of rim cushion rubbers 17 and 17 (see FIG. 1).

  The pair of bead cores 11 and 11 is an annular member formed by bundling a plurality of bead wires, and constitutes the core of the left and right bead portions. The pair of bead fillers 12 and 12 are disposed on the outer circumference in the tire radial direction of the pair of bead cores 11 and 11 to constitute a bead portion.

  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 is bridged in a toroidal shape between the left and right bead cores 11 and 11 to form a tire skeleton. Configure. Further, both end portions of the carcass layer 13 are wound and locked outward in the tire width direction so as to wrap the bead core 11 and the bead filler 12. The carcass ply of the carcass layer 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) with a coat rubber and rolling it, and has an absolute value of 80 It has a carcass angle (defined as the inclination angle of the fiber direction of the carcass cord with respect to the tire circumferential direction) of [deg] or more and 95 [deg] or less.

  The belt layer 14 is formed by laminating a pair of cross belts 141 and 142 and a belt cover 143, and is arranged around the outer periphery of the carcass layer 13. The pair of cross belts 141 and 142 is formed by rolling a plurality of belt cords made of steel or organic fiber material with a coating rubber, and has an absolute value of a belt angle of 20 [deg] or more and 55 [deg] or less. Have. The pair of cross belts 141 and 142 have belt angles with different signs from each other (defined as an inclination angle of the fiber direction of the belt cord with respect to the tire circumferential direction), and intersect the fiber directions of the belt cords with each other. (So-called cross-ply structure). The belt cover 143 is formed by rolling a plurality of cords made of steel or organic fiber material covered with a coat rubber, and has a belt angle of 0 [deg] or more and 10 [deg] or less in absolute value. Further, 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.

  The tread rubber 15 is disposed on the outer circumference in the tire radial direction of the carcass layer 13 and the belt layer 14 to constitute a tread portion of the tire. The pair of side wall rubbers 16 and 16 are respectively arranged on the outer side in the tire width direction of the carcass layer 13 to constitute left and right side wall portions. The pair of rim cushion rubbers 17, 17 are respectively disposed on the inner side in the tire radial direction of the wound portions of the left and right bead cores 11, 11 and the carcass layer 13, and constitute the contact surfaces of the left and right bead portions with respect to the rim flange.

[Tread pattern]
FIG. 2 is a plan view showing a tread surface of the pneumatic tire depicted in FIG. 1. The figure shows a tread pattern of a studless tire. In the figure, the tire circumferential direction refers to the direction around the tire rotation axis. Moreover, the code | symbol T is a tire grounding end.

  As shown in FIG. 2, the pneumatic tire 1 includes a plurality of circumferential main grooves 21 and 22 that extend in the tire circumferential direction, and a plurality of land portions 31 to 31 that are partitioned by the circumferential main grooves 21 and 22. 33 and a plurality of lug grooves 41 to 43 arranged in these land portions 31 to 33 are provided in the tread portion.

  The circumferential main groove is a circumferential groove having a wear indicator indicating the end of wear, and generally has a groove width of 5.0 [mm] or more and a groove depth of 7.5 [mm] or more. The lug groove means a lateral groove having a groove width of 2.0 [mm] or more and a groove depth of 3.0 [mm] or more.

  The groove width is measured as the maximum value of the distance between the left and right groove walls at the groove opening in a no-load state in which the tire is mounted on the prescribed rim and filled with the prescribed internal pressure. In the configuration where the land part has a notch part or a chamfered part at the edge part, the groove width is based on the intersection of the tread surface and the extension line of the groove wall in a cross-sectional view in which the groove length direction is a normal direction. Measured. In the configuration in which the groove extends in a zigzag shape or a wave shape in the tire circumferential direction, the groove width is measured with reference to the center line of the amplitude of the groove wall.

  The groove depth is measured as the maximum value of the distance from the tread surface to the groove bottom in an unloaded state in which the tire is mounted on the specified rim and filled with the specified internal pressure. Moreover, in the structure which a groove | channel has a partial uneven | corrugated | grooved part and a sipe in a groove bottom, groove depth is measured except these.

  The specified rim refers to an “applied rim” defined in JATMA, a “Design Rim” defined in TRA, or a “Measuring Rim” defined in ETRTO. The specified internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The specified load means the “maximum load capacity” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO. However, in JATMA, in the case of tires for passenger cars, the specified internal pressure is air pressure 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

  For example, in the configuration of FIG. 2, four circumferential main grooves 21 and 22 having a straight shape are arranged symmetrically about the tire equatorial plane CL. Further, five rows of land portions 31 to 33 are partitioned by the four circumferential main grooves 21 and 22. The land portion 31 is disposed on the tire equator plane CL. Moreover, each land part 31-33 is provided with the several lug groove | channels 41-43 which are arrange | positioned at predetermined intervals in the tire circumferential direction, and penetrate the land parts 31-33 in a tire width direction. Further, the second land portion 32 includes a circumferential narrow groove 23 that extends while being bent in the tire circumferential direction. And each land part 31-33 is divided into the circumferential direction main grooves 21 and 22, the circumferential direction fine groove 23, and the lug grooves 41-43, and becomes a block row | line | column.

  In the configuration of FIG. 2, as described above, the circumferential main grooves 21 and 22 have a straight shape. However, the present invention is not limited to this, and the circumferential main grooves 21 and 22 may have a zigzag shape or a wavy shape extending while being bent or curved in the tire circumferential direction (not shown).

  In the configuration of FIG. 2, as described above, the land portions 31 to 33 are divided in the tire circumferential direction by the lug grooves 41 to 43 to form a block row. However, the present invention is not limited to this, and for example, by having a semi-closed structure in which some of the lug grooves 41 to 43 terminate inside the land portions 31 to 33, some of the land portions 31 to 33 are continuous in the tire circumferential direction. It may be a rib (not shown).

  Further, in the configuration of FIG. 2, the pneumatic tire 1 has a tread pattern that is symmetrical with respect to left and right points. However, the present invention is not limited to this, and the pneumatic tire 1 may have, for example, a tread pattern that is symmetrical to the left and right lines, a tread pattern that is asymmetric to the left and right, and a tread pattern that has directionality in the tire rotation direction (not shown).

  In the configuration of FIG. 2, as described above, the pneumatic tire 1 includes four circumferential main grooves 21 and 22, and five rows of land portions 31 to 33 partitioned by these circumferential main grooves. It has. However, the present invention is not limited to this, and the pneumatic tire 1 may include three circumferential main grooves and four rows of land portions, or five or more circumferential main grooves and six rows or more of land portions. May be provided (not shown).

  In the tread pattern including the circumferential main grooves 21 and 22, the land portions 31 (see FIG. 2) on the tire equator plane CL or the left and right land divided into the circumferential main grooves on the tire equator plane CL. The part (not shown) is called the center land part. Also, the land portions 32, 32 on the inner side in the tire width direction defined by the left and right circumferential main grooves 22, 22 on the outermost side in the tire width direction are called second land portions, and the land portion 33 on the outer side in the tire width direction is the shoulder. Called the land.

  In the configuration of FIG. 2, as described above, the pneumatic tire 1 includes the circumferential main grooves 21 and 22 extending in the tire circumferential direction. However, the present invention is not limited thereto, and the pneumatic tire 1 may include a plurality of inclined main grooves that extend while being inclined at a predetermined angle with respect to the tire circumferential direction, instead of the circumferential main grooves 21 and 22. For example, the pneumatic tire 1 has a V-shape that is convex in the tire circumferential direction, and extends in the tire width direction and opens to the left and right tread ends, and adjacent V-shaped slopes. You may provide the several lug groove which connects a main groove, and the several land part divided by these V-shaped inclination main grooves and lug grooves (illustration omitted).

[Block sipe]
FIG. 3 is an explanatory diagram illustrating a land portion of the pneumatic tire illustrated in FIG. 2. The figure shows a plan view of one block 5 constituting the shoulder land portion 33. The shoulder land portion 33 is defined as a land portion on the outer side in the tire width direction that is partitioned into the outermost circumferential main groove.

  As shown in FIGS. 2 and 3, in the pneumatic tire 1, the blocks 5 of all the land portions 31 to 33 each have a plurality of sipes 6. With these sipes 6, the edge components of the land portions 31 to 33 are increased, and the braking performance on ice and the performance on snow are improved.

  A sipe is an incision formed in a land portion, and generally has a sipe width of less than 1.0 [mm] and a sipe depth of 2.0 [mm] or more, so that the sipe is closed at the time of tire contact. The upper limit of the sipe depth is not particularly limited, but is generally shallower than the groove depth of the main groove.

  The sipe width is measured as the maximum value of the sipe opening width on the ground contact surface of the land portion in a no-load state in which a tire is mounted on a specified rim and filled with a specified internal pressure.

  The sipe 6 has a closed structure that terminates in the land portions 31 to 33 at both ends, opens to the edge portion of the block 5 at one end portion, and terminates in the block 5 at the other end portion. It may have either a semi-closed structure that opens or an open structure that opens at the edge of the block 5 at both ends. Moreover, the length, the number, and the arrangement structure of the sipes 6 in the land portions 31 to 33 can be appropriately selected within a range obvious to those skilled in the art. Further, the sipe 6 can extend in any direction of the tire width direction, the tire circumferential direction, and the direction inclined to these.

  For example, in the configuration of FIG. 3, the shoulder land portion 33 includes a plurality of blocks 5 that are partitioned into an outermost circumferential main groove 22 and a plurality of lug grooves 43 (see FIG. 2). One block 5 includes a plurality of sipes 6. These sipes 6 have a zigzag shape extending in the tire width direction, and are arranged in parallel at a predetermined interval in the tire circumferential direction. Further, the sipe 6 on the outermost side in the tire circumferential direction has a closed structure that terminates inside the block 5 at both ends. Thereby, the rigidity of the edge part of the step-on side and kick-out side of the block 5 at the time of tire rolling is ensured. Further, the sipe 6 at the center in the tire circumferential direction has a semi-closed structure that opens into the circumferential main groove 22 at one end and terminates inside the block 5 at the other end. . Thereby, the rigidity of the center part of the block 5 is reduced, and the rigidity distribution in the tire circumferential direction of the block is made uniform.

[Narrow shallow groove in the block]
FIG. 4 is an enlarged view showing the tread of the block. FIG. 5 is an explanatory view showing a cross section in the depth direction of the recess. In these drawings, FIG. 4 shows the positional relationship between the sipe 6, the thin shallow groove 7 and the concave portion 8, and FIG. 5 shows the depth relation between the thin shallow groove 7 and the two types of concave portions 81 and 82. .

  In this pneumatic tire 1, the land portions 31 to 33 include a plurality of narrow grooves 7 on the ground contact surface (see FIG. 3). In such a configuration, the on-ice braking performance of the tire is improved by the thin shallow grooves 7 sucking and removing the water film interposed between the ice road surface and the tread surface when the tire is in contact with the tire.

  The plurality of thin shallow grooves 7 have a longitudinal shape and are arranged in parallel to each other (see FIG. 4). In such a configuration, since the thin shallow groove 7 has a longitudinal shape, the water film absorbed in the thin shallow groove 7 can be guided and discharged in the longitudinal direction of the thin shallow groove 7. Moreover, since the recessed part 8 mentioned later is arrange | positioned ranging over the some thin shallow groove | channel 7 which has this longitudinal shape, the recessed part 8 becomes a reservoir of the absorbed water film, and the water absorption of the block 5 improves. These improve the braking performance on ice of the tire.

  The thin shallow groove 7 has a groove width of 0.2 [mm] or more and 0.7 [mm] or less and a groove depth Hg (see FIG. 5) of 0.2 [mm] or more and 0.7 [mm] or less. . For this reason, the narrow shallow groove 7 is shallower than the sipe 6. A plurality of thin shallow grooves 7 are arranged on the entire surface of the land portions 31 to 33.

  For example, in the configuration of FIG. 3, the plurality of shallow grooves 7 are arranged over the entire ground contact surface of the shoulder land portion 33. Further, the thin shallow groove 7 has a linear shape, and is disposed at a predetermined inclination angle θ (see FIG. 4) with respect to the tire circumferential direction. A plurality of shallow grooves 7 are arranged in parallel with a predetermined interval P (see FIG. 4) between each other. As shown in FIG. 4, the thin shallow groove 7 intersects with the sipe 6 and is divided by the sipe 6 in the longitudinal direction.

  As shown in FIG. 3, in the configuration in which the plurality of shallow grooves 7 have a long shape and are arranged in parallel to each other, the inclination angle θ of the shallow grooves 7 (see FIG. 4) is 20 [deg. ] ≦ θ ≦ 80 [deg], preferably 40 [deg] ≦ θ ≦ 60 [deg]. The arrangement interval P (see FIG. 4) of the thin shallow grooves 7 is preferably in the range of 0.5 [mm] ≦ P ≦ 1.5 [mm], and 0.7 [mm] ≦ P ≦ 1. More preferably, it is in the range of 2 [mm]. Thereby, the water film removal effect | action by the thin shallow groove | channel 7 is ensured appropriately, and the ground-contact area of the land parts 31-33 is ensured. The arrangement density of the narrow shallow grooves 7 is not particularly limited, but is limited by the arrangement interval P described above.

  The arrangement interval P of the thin shallow grooves 7 is defined as the distance between the groove center lines of the adjacent thin shallow grooves 7 and 7.

[Block recess]
As shown in FIGS. 2 and 3, in the pneumatic tire 1, all the land portions 31 to 33 include a plurality of concave portions 8 on the ground contact surface. In such a configuration, when the tire is in contact with the tire, the concave portion 8 absorbs a water film formed between the ice road surface and the tread surface, and the edge component of the land portions 31 to 33 is increased by the concave portion 8 so that the braking performance on the ice of the tire is increased. Will improve.

  The concave portion 8 is a closed depression formed on the ground contact surface of the land portions 31 to 33 (a recess not opened at the boundary of the ground contact surface, so-called dimple), and has an arbitrary geometry on the ground contact surface of the land portions 31 to 33. Has a geometric shape. For example, the opening of the recess 8 may have a circular shape or an elliptical shape, or may have a polygonal shape such as a quadrangular shape or a hexagonal shape. The circular or elliptical concave portion 8 is preferable in that the uneven wear of the ground contact surfaces of the land portions 31 to 33 is small, and the polygonal concave portion 8 is preferable in that the edge component is large and the braking performance on ice can be improved.

  Moreover, it is preferable that the opening area of the recessed part 8 exists in the range of 2.5 [mm ^ 2] or more and 10 [mm ^ 2] or less. For example, in the case of the circular concave portion 8, the diameter is in the range of about 1.8 [mm] to 3.6 [mm]. Thereby, the opening area of the recessed part 8 is optimized. That is, when the opening area of the recess 8 is 2.5 [mm ^ 2] or more, the edge action and water absorption of the recess 8 are ensured. Moreover, when the opening area of the recessed part 8 is 10 [mm ^ 2] or less, the ground contact area of the block 5 is ensured.

  The opening area of the recessed portion 8 is an opening area of the recessed portion 8 on the ground contact surface of the land portions 31 to 33, and is measured as an unloaded state while attaching a tire to a specified rim and applying a specified internal pressure.

  Moreover, it is preferable that the depth of the recessed part 8 exists in the range of 0.10 [mm] or more and less than 2.0 [mm], and exists in the range of 0.2 [mm] or more and 1.5 [mm] or less. Is more preferable. That is, the depth of the concave portion 8 is obviously deeper than the surface roughness level applied to the tire ground contact surface, and a general sipe (for example, a linear sipe 6 or a circular sipe (not shown)). The range is clearly shallower than the depth of. Due to the lower limit of the numerical range, the function of the concave portion 8 is appropriately secured, and the rigidity of the land portions 31 to 33 is appropriately secured by the upper limit of the numerical range.

  The wall angle α (see FIG. 5) of the recess 8 is preferably in the range of −85 [deg] ≦ α ≦ 95 [deg]. That is, it is preferable that the inner wall of the recess 8 is substantially perpendicular to the ground contact surfaces of the land portions 31 to 33. Thereby, the edge component of the recessed part 8 increases.

  The wall angle α of the concave portion 8 is measured as an angle formed by the ground contact surfaces of the land portions 31 to 33 and the inner wall of the concave portion 8 in a sectional view of the concave portion 8 in the depth direction.

  In addition, as shown in FIG. 4, the recess 8 is disposed away from the sipe 6. That is, the recessed part 8 and the sipe 6 are arrange | positioned in a mutually different position on the ground surface of the land parts 31-33, and do not cross | intersect. The distance g between the recess 8 and the sipe 6 is preferably in the range of 0.2 [mm] ≦ g, and more preferably in the range of 0.3 [mm] ≦ g. Thereby, the rigidity of land part 31-33 is ensured appropriately.

  In addition, as shown in FIG. 4, the recess 8 is disposed so as to intersect the thin shallow groove 7 and communicate with the thin shallow groove 7. Moreover, the recessed part 8 is arrange | positioned ranging over several adjacent thin shallow grooves 7 and 7 isolate | separated mutually. In other words, a plurality of adjacent thin shallow grooves 7, 7 separated from each other are disposed through one recess 8. Thereby, a plurality of adjacent thin shallow grooves 7 and 7 are connected via the recess 8 and communicate with each other. Further, the concave portion 8 is interposed between the plurality of adjacent thin shallow grooves 7 and 7 to partially enlarge the volume of the thin shallow groove 7. Then, when the tire is in contact with the tire, the concave portion 8 becomes a pool of water, and the water film on the ice road surface is efficiently absorbed. Thereby, the braking performance on ice of a tire improves.

  The plurality of shallow grooves 7 separated from each other refers to a plurality of shallow grooves 7 extending without intersecting each other in an arrangement pattern of only the shallow grooves 7 excluding the sipes 6 and the recesses 8. Accordingly, an arrangement pattern in which the plurality of thin shallow grooves 7 intersect each other is excluded.

  For example, in the configuration of FIG. 3, the plurality of thin shallow grooves 7 having a linear shape are disposed on the entire surface of the land portion 33 at predetermined intervals while being inclined at a predetermined angle with respect to the tire circumferential direction. For this reason, as shown in FIG. 4, the adjacent thin shallow grooves 7 and 7 are arranged in parallel with each other and run in one direction. Moreover, the recessed part 8 is arrange | positioned ranging over two adjacent thin shallow grooves 7 and 7, and these thin shallow grooves 7 and 7 are connected. In other words, the two thin shallow grooves 7 and 7 that run side by side pass through one recess 8 in one direction. Not limited to the above, three or more shallow grooves 7 may penetrate one recess 8 (not shown).

  Further, in the above configuration, the number of the concave portions 8 arranged across the plurality of adjacent thin shallow grooves 7 on the grounding surface of one block 5 is based on the total number of the concave portions 8 on the grounding surface. It is preferably 70% or more, more preferably 80% or more. Thereby, the function as a water pool of the above-mentioned recessed part 8 is exhibited effectively. For example, in the configuration of FIG. 3, all the recesses 8 are disposed across two adjacent thin shallow grooves 7, 7. However, the present invention is not limited to this, and some of the recesses 8 may intersect with the single narrow groove 7 or between the adjacent shallow grooves 7 and 7 without intersecting the shallow groove 7. (Not shown).

  In the configuration of FIG. 3, the land portion 33 includes a plurality of sipes 6 that divide the narrow shallow grooves 7 on the ground contact surface. Further, a portion of one narrow shallow groove 7 defined by the sipe 6 extends without penetrating the plurality of recesses 8. That is, the plurality of recesses 8 are distributed and arranged so as not to be overlapped with respect to the portion of the single shallow groove 7 partitioned by the sipe 6. For this reason, only one concave portion 8 is arranged at the maximum in one narrow groove 7 portion.

  Further, as shown in FIG. 3, the recesses 8 are arranged sparsely compared to the narrow shallow grooves 7. Specifically, the arrangement density Da of the recesses 8 in the entire area of the ground contact surface of one block 5 is in the range of 0.8 [pieces / cm ^ 2] ≦ Da ≦ 4.0 [pieces / cm ^ 2]. It is more preferable that it is in the range of 1.0 [pieces / cm 2] ≦ Da ≦ 3.0 [pieces / cm 2]. Thereby, arrangement | positioning density Da of the recessed part 8 is optimized. That is, when 0.8 [pieces / cm ^ 2] ≦ Da, the number of the recessed portions 8 is secured, and the function of the recessed portions 8 is appropriately secured. In addition, since Da ≦ 4.0 [pieces / cm 2], the ground contact area of the block 5 is appropriately secured.

  The arrangement density Da of the recesses 8 is defined as the total number of the recesses 8 with respect to the area of the ground contact surface of one rib or block. For example, when the land portion is a rib that is continuous in the tire circumferential direction (not shown), the total number of recesses 8 with respect to the contact area of the entire one rib is the arrangement density Da. When the land portion is a block (see FIGS. 2 and 3), the total number of the recesses 8 with respect to the ground contact area of one block 5 is the arrangement density Da.

  The contact area of the land is determined by the tire and the flat plate when the tire is mounted on the specified rim and applied with the specified internal pressure, and is placed perpendicular to the flat plate in a stationary state and applied with a load corresponding to the specified load. Measured at the contact surface.

[Arrangement of recesses]
Here, the center area | region and edge part area | region of a tire width direction are defined in the continuous contact surface of the land parts 31-33. The center region and the end region in the tire width direction can be defined for both ribs and blocks.

  The central region in the tire width direction is defined as the region of the central portion 50 [%] in the tire width direction of the continuous contact surface. The end region in the tire width direction is defined as the region of the left and right end portions 25 [%] in the tire width direction of the continuous contact surface. For example, when the land portion is a rib that is continuous in the tire circumferential direction (not shown), a center region and an end region in the tire width direction are defined for the ground contact surface of one entire rib. When the land portion is a block row (see FIG. 2), a center region and an end region are respectively defined for the ground contact surfaces of the blocks constituting the block row. Moreover, if the center of a recessed part exists in the said area | region, it can be said that the recessed part is arrange | positioned in the said area | region.

  A continuous ground plane is defined as a ground plane defined by grooves having a groove width of 2.0 [mm] or more and a groove depth of 3.0 [mm] or more. Specifically, the ground contact surface of one rib or one block defined by the circumferential groove and the lug groove having the groove width and the groove depth corresponds to the continuous ground contact surface. Also, for example, a closed structure lug groove that terminates in the land part, a partial notch formed in the land part (for example, a notch part 311 in FIG. 7 described later), a sipe or kerf that closes when the tire touches, It does not correspond to the above groove because it does not divide the ground contact surface. In the shoulder land portion 33, the continuous ground contact surface can be defined by the tire ground contact end T (see FIG. 3).

  The tire ground contact edge T is the contact between the tire and the flat plate when a load corresponding to the predetermined load is applied by attaching the tire to the specified rim and applying the specified internal pressure and placing the tire perpendicularly to the flat plate in a stationary state. The maximum width position in the tire axial direction on the surface.

  Further, a 5 [mm] square area including the corners of the continuous ground contact surface is defined as the corner of the land. The corner portion of the land portion is not only a portion of the land portion partitioned by the main groove and the lug groove, but also a land portion partitioned by a notch portion formed in the land portion (for example, a notch portion 311 in FIG. 7 described later). Including the part. Moreover, if the center of a recessed part exists in the said area | region, it can be said that the recessed part is arrange | positioned at the corner | angular part of a land part.

  In the configuration in which the land portions 31 to 33 each include a block row including a plurality of blocks 5 and each block 5 includes a plurality of sipes 6 extending in the tire width direction, the plurality of sipes 6 are in the tire circumferential direction. Are arranged in parallel to divide the block 5 into a plurality of sections in the tire circumferential direction. These sections are defined as the sections of the block 5. The section of block 5 can be defined for each block 5. The sipe 6 may have an open structure, or a closed structure or a semi-closed structure.

  In the configuration of FIG. 3, the block 5 of the shoulder land portion 33 has a rectangular ground surface. Further, the block 5 is partitioned in the tire circumferential direction by a plurality of sipes 6 to form a plurality of sections. Further, all the sections of the block 5 have at least one recess 8. Moreover, at least one of arbitrary three sections adjacent to each other in the tire circumferential direction has a recess 8 in a central region in the tire width direction. Further, at least one of arbitrary three sections adjacent in the tire circumferential direction has a recess 8 in an end region in the tire width direction. Thereby, the recesses 8 are arranged in a distributed manner in the block 5.

  In the end region in the tire width direction of the block 5, particularly in the end region on the circumferential main groove 22 side, a larger ground pressure acts than the central region of the block 5 at the time of tire contact. For this reason, when traveling on an icy road surface, the ice on the road surface is easily melted by the contact pressure, and a water film is easily generated. Therefore, by arranging the recess 8 in the end region of the block 5, the water film on the tread is efficiently absorbed, and the braking performance on ice of the tire is improved.

  In particular, the shoulder land portion 33 has a great influence on the braking performance of the tire. Therefore, as shown in FIG. 3, the block 5 of the shoulder land portion 33 is provided with a recess 8 having a larger volume than the thin shallow groove 7 in the end region in the tire width direction, thereby improving the braking performance on ice by the recess 8. The effect is remarkably obtained.

  Further, in the configuration of FIG. 3, sections of both end portions in the tire circumferential direction of the block 5 have the concave portions 8 at two corners on the circumferential main groove 22 side of the block 5, respectively. In particular, it is preferable that the concave portion 8 is disposed at a corner portion having a ground contact surface with an acute angle (that is, less than 90 [deg]). For example, in the configuration of FIG. 3, the block 5 has corners at the intersections between the outermost circumferential main groove 22 and the pair of lug grooves 43, 43, and the lower left corner in the figure has a sharp ground contact surface. In the figure, the upper left corner has an obtuse ground contact surface.

  A large contact pressure acts on the corner of the block 5, particularly the corner having an acute contact surface when the tire contacts the ground. For this reason, when traveling on an icy road surface, the ice on the road surface is easily melted by the contact pressure, and a water film is easily generated. Therefore, by disposing the recess 8 at the corner of the block 5, the water film on the tread is efficiently absorbed, and the braking performance on ice of the tire is improved.

  In the configuration of FIG. 3, the sipe 6 is disposed parallel to or slightly inclined from the lug groove 43, and is disposed only in a region inside the tire width direction from the tire ground contact end T. Further, the narrow shallow groove 7 extends beyond the tire ground contact end T to a region outside the land portion 33 in the tire width direction. Further, the concave portion 8 is disposed only in a region on the inner side in the tire width direction from the tire ground contact end T.

  6 and 7 are explanatory views showing a land portion of the pneumatic tire shown in FIG. In these drawings, FIG. 6 shows a plan view of the blocks 5 per pitch constituting the second land portion 32. FIG. 7 shows a plan view of one block 5 constituting the center land portion 31. The second land portion 32 is defined as a land portion on the inner side in the tire width direction that is partitioned by the outermost circumferential main groove 22. The center land portion 31 is defined as a land portion 31 (see FIG. 2) on the tire equator plane CL or a land portion (not shown) adjacent to the tire equator plane CL.

  In the configuration of FIG. 2, the second land portion 32 is divided in the tire width direction by one circumferential narrow groove 23, and further divided in the tire circumferential direction by a plurality of lug grooves 42, thereby dividing the plurality of blocks 5. ing. Further, a block 5 that is long in the tire circumferential direction is formed in a region on the inner side in the tire width direction of the second land portion 32, and a short block 5 is formed in a region on the outer side in the tire width direction. In addition, one pitch of the second land portion 32 is configured by one long block 5 and two short blocks 5 as a set.

  Moreover, as shown in FIG. 6, the one short block 5 in the tread part shoulder area | region side of the 2nd land part 32 has a rectangular-shaped ground surface. A short block 5 is partitioned in the tire circumferential direction by a plurality of sipes 6 to form a plurality of sections. All the sections of the short block 5 have at least one recess 8. Moreover, at least one of arbitrary three sections adjacent to each other in the tire circumferential direction has a recess 8 in a central region in the tire width direction. Further, at least one of arbitrary three sections adjacent in the tire circumferential direction has a recess 8 in an end region in the tire width direction. Further, in the sections of both ends of the short block 5 in the tire circumferential direction, the concave portions 8 are respectively disposed at the corners of the short block 5 on the circumferential main groove 22 side. Thereby, the recessed part 8 is disperse | distributed and arrange | positioned at the edge part area | region and center part area | region of the tire width direction, and the braking performance on ice of a tire is improved.

  In particular, since the short block 5 has low rigidity, the amount of collapse of the block 5 is large during vehicle braking. Further, in the configuration in which the block 5 has a plurality of sipes 6, the tendency becomes remarkable, and the braking performance on ice of the tire tends to be lowered. Further, the second land portion 32 has a great influence on the braking / driving performance of the tire. Therefore, the short block 5 has the recesses 8 in all sections partitioned by the sipe 6, so that the water film on the tread is efficiently absorbed and the braking performance on the tire is ensured.

  In FIG. 6, the long block 5 on the tread portion center region side of the second land portion 32 has a substantially rectangular contact surface that is long in the tire circumferential direction. Further, the long block 5 is partitioned in the tire circumferential direction by a plurality of sipes 6 to form a plurality of sections. In such a block 5 that is long in the tire circumferential direction, it is preferable that at least one of any three sections adjacent in the tire circumferential direction has a recess 8. In FIG. 6, at least one of an arbitrary pair of sections adjacent in the tire circumferential direction has a recess 8. Moreover, in the section of the both ends of the long block 5 in the tire circumferential direction, the concave portions 8 are respectively disposed at the corners of the long block 5 on the circumferential main groove 21 side. Thereby, the recessed part 8 is dispersively arrange | positioned and the braking performance on ice of a tire is improved.

  In the configuration of FIG. 2, the center land portion 31 is divided in the tire circumferential direction by a plurality of lug grooves 41, and a plurality of blocks 5 are partitioned. Further, the block 5 has a notch 311 on the extension line of the lug groove 42 of the second land portion 32. The block 5 has a rectangular grounding surface.

  Moreover, as shown in FIG. 7, the block 5 of the center land portion 31 is partitioned in the tire circumferential direction by a plurality of sipes 6 to form a plurality of sections. Further, at least one of arbitrary three sections adjacent to each other in the tire circumferential direction has a recess 8. Further, in the sections of both end portions of the block 5 in the tire circumferential direction, the concave portions 8 are respectively arranged at corner portions of the block 5 on the circumferential main groove 21 side. Further, the section including the notch 311 has a recess 8 in the vicinity of the notch 311. Thereby, the recessed part 8 is disperse | distributed and arrange | positioned in the block 5, and the braking performance on ice of a tire is improved.

  In the above configuration, it is preferable that at least a part of the recesses 8 is disposed at a position corresponding to a vent hole of a tire molding die (not shown). That is, in the tire vulcanization molding step, it is necessary to discharge the air in the tire molding die to the outside in order to press the green tire against the tire molding die. For this reason, the tire molding die has a plurality of vent devices (a vent device provided with a so-called ventless mold, not shown) on the die surface for molding the ground contact surfaces of the land portions 31 to 33. Moreover, a certain kind of vent apparatus forms the vent hole (small hollow) as a vent trace in the ground surface of the land parts 31-33 after vulcanization molding. Therefore, by using this vent hole as the concave portion 8, the vent hole is effectively used, and unnecessary dents in the ground contact surfaces of the land portions 31 to 33 are reduced to reduce the ground contact area of the land portions 31 to 33. Properly secured.

  In particular, in the tire vulcanization molding process, there is a problem that residual air tends to accumulate at the corners of the land portions 31 to 33. For this reason, it is preferable that the corner | angular part of land part 31-33 has the recessed part 8, and this recessed part 8 is arrange | positioned in the position corresponding to the vent hole of a tire shaping die. Thereby, the residual air of a corner | angular part can be reduced effectively, utilizing a vent hole as the recessed part 8. FIG.

[Uneven distribution of volume ratio of recesses in center / shoulder region]
As shown in FIG. 2, in the pneumatic tire 1, the land portions 31 to 33 include a plurality of types of concave portions 81 and 82. In the same figure, the white circles and the black circles indicate different types of recesses 8 from each other. Moreover, these recessed parts 81 and 82 have a mutually different volume by having the solid shape of a depth direction mutually different.

  The volume of the recess is defined as the volume of the space surrounded by the tread surface of the land and the inner wall surface of the recess, and is measured as a no-load state while applying a specified internal pressure by mounting the tire on a specified rim.

  The three-dimensional shape in the depth direction is defined as a dimension and shape in the depth direction of the recess, and is a concept including a depth Hd and an inner wall surface shape (see FIGS. 8 to 12) of the recess 8 described later.

  Further, the volume ratio Vce of the concave portion 8 in the tread portion center region and the volume ratio Vsh of the concave portion 8 in the tread portion shoulder region have a relationship of Vce <Vsh. That is, the volume ratio Vsh of the concave portion 8 in the tread portion shoulder region is larger than that in the tread portion center region. Further, the ratio Vsh / Vce of the volume ratios of the recesses 8 preferably has a relationship of 1.10 ≦ Vsh / Vce, and more preferably has a relationship of 1.20 ≦ Vsh / Vce. The upper limit of the ratio Vsh / Vce is not particularly limited, but is limited by the relationship with the numerical range such as the depth of the recess 8, the three-dimensional shape, the arrangement density, and the opening area.

  Moreover, as shown in FIG. 2, it is preferable that the recessed part 8 is disperse | distributed and arrange | positioned to the whole region of the grounding area | region of a tread part. Thereby, the fundamental effect of the single recessed part 8 is obtained in the whole tread. However, the present invention is not limited to this, and the recess 8 may be disposed only in the tread shoulder region (not shown). In this case, that is, when the concave portion 8 is disposed only in the tread portion shoulder region and is not disposed in the tread portion center region, Vce = 0 and the relationship of Vce <Vsh is satisfied.

  In principle, the tread portion center region and the shoulder region are defined with a reference line dividing the ground contact region of the tread portion into three equal parts in the tire width direction as a boundary. However, circumferential grooves (for example, circumferential main grooves, circumferential narrow grooves, etc.) that are continuous in the tire circumferential direction are arranged in a region from 28 [%] to 38 [%] of the tire ground contact width from the tire ground contact edge T. In the configuration (see FIG. 2), the tread portion center region and the shoulder region are defined with the circumferential groove closest to the reference line (in FIG. 2, the circumferential narrow groove 23) as a boundary line.

  The contact area of the tread portion is defined as an area between the left and right tire contact ends T, T. The tire ground contact end T is a contact surface between the tire and the flat plate when a tire is mounted on a predetermined rim to apply a predetermined internal pressure and a load corresponding to the predetermined load is applied in a stationary state perpendicular to the flat plate. Is defined as the maximum width position in the tire axial direction.

  The volume ratio of the recesses is defined as a ratio between the total volume of the recesses arranged in the predetermined area and the contact area of the area. When the concave portion and the boundary line of the region intersect, it can be said that the concave portion is arranged in the region if the central point of the concave portion is in the region.

  The contact area of the region is determined by the tire and the flat plate when the tire is mounted on the specified rim and applied with the specified internal pressure and is placed perpendicular to the flat plate in a stationary state and applied with a load corresponding to the specified load. Measured at the contact surface.

  Further, the volume ratios Vce and Vsh of the recesses 8 in the tread portion center region and the tread portion shoulder region are the three-dimensional shapes in the depth direction of the recesses 8 disposed in each region (for example, the depth and inner wall surface shape described later). It is preferable to adjust by. That is, the group of the recesses 8 in the center region of the tread part and the group of the recesses 8 in the shoulder region of the tread part have different three-dimensional shapes in the depth direction, so that the volume ratio Vce of the recesses 8 in each area. , A difference is formed in Vsh.

  (1) Generally, in the tread portion shoulder region, the contact pressure is higher than that in the tread portion center region, and a water film is likely to be generated when traveling on an icy road surface. At this time, by setting the volume ratio Vsh of the recess 8 in the tread shoulder region to be large, the water absorption of the tread surface in the tread shoulder region where a water film is easily generated is improved, and the ground contact characteristic of the tread shoulder region is improved. improves. Thereby, the braking performance on ice and the turning performance on ice are improved. (2) Generally, the tread portion center region has a large contribution to the steering stability performance at a small steering angle of the tire. Therefore, by setting the volume ratio Vce of the concave portion 8 in the tread portion center region to be small as described above, a decrease in block rigidity due to the arrangement of the concave portion 8 is mitigated, and the steering stability performance of the tire is improved.

  In the above configuration, the opening area ratio Sce of the recess 8 in the center region of the tread and the opening area ratio Ssh of the recess 8 in the shoulder region of the tread have a relationship of 0.90 ≦ Ssh / Sce ≦ 1.10. Preferably, it has a relationship of 0.95 ≦ Ssh / Sce ≦ 1.05. Therefore, the opening area ratios Sce and Ssh of the recess 8 are made uniform between the tread center region and the shoulder region. Thereby, a difference can be formed in the volume ratios Vce and Vsh of the recesses 8 in each region while making the ground contact area of each region in the tread portion uniform.

  The opening area ratio of the recess is defined as a ratio between the sum of the opening areas of the recesses arranged in the predetermined region and the ground contact area of the region. When the concave portion and the boundary line of the region intersect, it can be said that the concave portion is arranged in the region if the central point of the concave portion is in the region.

  Further, it is preferable that the arrangement density Dce of the recesses 8 in the tread portion center region and the arrangement density Dsh of the recesses 8 in the tread portion shoulder region have a relationship of 0.90 ≦ Dsh / Dce ≦ 1.10. It is more preferable to have a relationship of 95 ≦ Dsh / Dce ≦ 1.05. In such a configuration, since the arrangement density Dce, Dsh of the recesses 8 is made uniform between the tread portion center region and the shoulder region, the ground portions 31-33 are grounded due to the uneven distribution of the volume ratios Vce, Vsh of the recesses 8. An excessive change in characteristics can be suppressed.

  The arrangement density Dce, Dsh of the recesses is defined as a ratio between the total number of the recesses 8 arranged on the ground contact surface of each region (center region and left and right shoulder regions) of the tread portion and the contact area of each region. The

  Further, the number of the recessed portions 8 is counted as the number of the center points of the recessed portions 8 in the predetermined area. Further, when the recess 8 intersects the boundary line of the region, it can be said that the recess is disposed in the region if the center point of the recess is in the region.

  Moreover, it is preferable that the maximum value A_max and the minimum value A_min of the opening area of the recesses 8 arranged in the entire tread portion have a relationship of 1.00 ≦ A_max / A_min ≦ 1.10, and 1.00 ≦ A_max It is more preferable to have a relationship of /A_min≦1.05. Therefore, the opening area of each recess 8 is made uniform throughout the tread portion. Thereby, the excessive change of the grounding characteristic resulting from the dispersion | variation in the opening area of the recessed part 8 can be suppressed.

  Therefore, in this embodiment, the volume ratios Vce and Vsh of the recess 8 in each region are mainly adjusted by the depth of the recess 8 or the inner wall surface shape described later.

  In the configuration of FIG. 2, as described above, the pneumatic tire 1 includes the four circumferential main grooves 21 and 22 and the five rows of land portions 31 to 33. Further, these circumferential main grooves 21 and 22 are arranged symmetrically about the tire equatorial plane CL. The tread portion center region and the shoulder region are partitioned with the circumferential narrow grooves 23 and 23 of the left and right second land portions 32 and 32 as boundaries.

  Here, in the configuration having four or more circumferential main grooves 21 and 22 as shown in FIG. 2, the volume ratio V1 of the concave portion 8 in the center land portion 31, the volume ratio V2 of the concave portion 8 in the second land portion 32, It is preferable that the volume ratio V3 of the concave portion 8 in the shoulder land portion 33 has a relationship of V1 <V3 <V2. That is, the volume ratio V2 of the concave portion 8 in the second land portion 32 is the highest (V1 <V2 and the volume ratio V1 of the concave portion 8 in the center land portion 31 and the volume ratio V3 of the concave portion 8 in the shoulder land portion 33. V3 <V2). Further, the volume ratio V3 of the concave portion 8 in the shoulder land portion 33 is higher than the volume ratio V1 of the concave portion 8 in the center land portion 31 (V1 <V3). Further, as described above, the volume ratio Vsh of the tread portion shoulder region is set to be relatively larger than the volume ratio Vce of the tread portion center region (Vce <Vsh). Thereby, the volume ratios Vce and Vsh of the concave portion 8 in the ground contact region of the entire tread are optimized.

  In the configuration having the circumferential main groove on the tire equator plane CL (not shown), the left and right land portions defined by the circumferential main groove on the tire equator plane CL are the center land portions, and the above-described recess 8 The condition of the volume ratio V1 is satisfied.

  In the above configuration, the volume ratio V1 of the recess 8 in the center land portion 31 and the volume ratio V3 of the recess 8 in the shoulder land portion 33 preferably have a relationship of 1.10 ≦ V3 / V1. It is more preferable to have a relationship of 20 ≦ V3 / V1. The upper limit of the ratio V3 / V1 is not particularly limited, but is limited by the range of the arrangement density Da of the concave portions 8 on the continuous ground contact surface of the land portions 31 to 33 described above.

  Similarly, the volume ratio V3 of the recess 8 in the shoulder land portion 33 and the volume ratio V2 of the recess 8 in the second land portion 32 preferably have a relationship of 1.10 ≦ V2 / V3, and 1.20 ≦ V2 / V3. It is more preferable to have this relationship.

  In the configuration of FIG. 2, the second land portion 32 includes the circumferential narrow groove 23 extending in the tire circumferential direction as described above. Further, the circumferential narrow groove 23 is formed at the center of the second land portion 32 in the tire width direction (an area of 30 [%] to 70 [%] of the width of the second land portion 32 with respect to the outermost circumferential main groove 22). Has been placed. Further, the volume ratio V21 of the recess 8 in the inner region in the tire width direction of the second land portion 32 partitioned by the circumferential narrow groove 23 and the volume ratio V22 of the recess 8 in the outer region in the tire width direction are V21 <V22. It is preferable to have the following relationship. Therefore, the concave portion 8 is set relatively high in the region on the outer side in the tire width direction of the second land portion 32. Specifically, the volume ratios V21 and V22 of the concave portion 8 preferably have a relationship of 1.10 ≦ V22 / V21, and more preferably have a relationship of 1.20 ≦ V22 / V21.

[Uneven distribution of recess depth in center / shoulder region]
For example, in the configuration of FIG. 2, two types of recesses 81 and 82 are mixedly arranged in the tread portion center region and the tread portion shoulder region. In the figure, a white circle indicates a shallow concave portion 81 and a black circle indicates a deep concave portion 82. The volume ratios Vce and Vsh of the recess 8 in each region are adjusted by these two types of recesses 81 and 82.

  Specifically, the block 5 of each land part 31-33 is provided with two types of recessed parts 81 and 82 which have a mutually different volume by having a mutually different depth. Moreover, the average value Hdce of the depth of the recess 8 in the tread portion center region and the average value Hdsh of the depth of the recess 8 in the tread portion shoulder region have a relationship of Hdce <Hdsh. That is, the average value Hdsh of the depth of the recess 8 in the shoulder region is larger than that in the center region. Further, the average value Hdce of the depth of the recess 8 in the tread portion center region and the average value Hdsh of the depth of the recess 8 in the end region in the tire width direction have a relationship of 1.10 ≦ Hdsh / Hdce. It is more preferable that the relationship of 1.20 ≦ Hdsh / Hdce is more preferable. The upper limit of the ratio Hdsh / Hdce is not particularly limited, but is limited by the relationship with the numerical range such as the depth of the recess 8, the three-dimensional shape, the arrangement density, and the opening area.

  Moreover, it is preferable that the average value Hdsh of the depth of the recessed part 8 in the left and right tread part shoulder regions satisfies the above condition Hdce <Hdsh. However, the present invention is not limited to this, for example, the average value Hdsh of the depth of the recess 8 in one tread shoulder region satisfies the above condition Hdce <Hdsh, and the average value Hdsh of the depth of the recess 8 in the other shoulder region. However, it may be the same as the average depth Hdce of the recesses 8 in the center region (Hdce = Hdsh) (not shown). Even with this configuration, a certain degree of effect can be obtained.

  The average value of the depths of the recesses is defined as a ratio between the sum of the depths of the recesses in the predetermined region and the total number of recesses in the region.

  Generally, in the tread portion shoulder region, the contact pressure is higher than that in the tread portion center region, and a water film is likely to be generated when traveling on an icy road surface. At this time, by setting the average value Hdsh of the depth of the concave portion 8 in the tread portion shoulder region to be large, the water absorption of the tread portion shoulder region where the water film is likely to be generated is improved, and the tread portion shoulder region Improves grounding characteristics. Thereby, the braking performance on ice and the turning performance on ice are improved.

  In general, the tread portion center region greatly contributes to the steering stability performance at a small steering angle of the tire. Therefore, as described above, by setting the average value Hdce of the depth of the concave portion 8 in the tread portion center region to be small, the decrease in the block rigidity due to the arrangement of the concave portion 8 is alleviated, and the steering stability performance of the tire is improved. improves.

  Further, 70 [%] or more (preferably 80 [%] or more) of the recesses 8 arranged in the center region of the tread part is 50 [%] with respect to the groove depth Hg (see FIG. 5) of the thin shallow groove 7. The depth Hd is preferably 150% or more and 150% or less, more preferably 80% or more and 120% or less. That is, in the tread portion center region, the depth Hd of most of the recesses 8 is set to be substantially the same as the groove depth Hg of the thin shallow groove 7. As a result, most of the concave portions 8 in the center region of the tread portion can disappear at the same time as the thin shallow grooves 7 as the tire wear progresses.

  Furthermore, 70 [%] or more (preferably 80 [%] or more) of the recesses 8 arranged in the shoulder region of the tread portion is 120 [%] with respect to the groove depth Hg (see FIG. 5) of the thin shallow groove 7. It is preferable to have the above depth Hd, and it is more preferable to have a depth Hd of 180 [%] or more. That is, in the tread shoulder region, the depth Hd of most of the recesses 8 is set larger than the groove depth Hg of the thin shallow groove 7. Therefore, as the tire wear progresses, most of the recesses 8 arranged in the tread shoulder region remain even after the narrow grooves 7 disappear. Not limited to the above, all the recesses 8 may disappear at the same time as or before the thin shallow groove 7 disappears.

  In the above configuration, since the groove depth Hg of each thin shallow groove 7 is in the range of 0.2 [mm] or more and 0.7 [mm] or less, most of the recesses disposed in the tread portion center region. The depth of 8 is substantially in the range of 0.10 [mm] or more and 1.05 [mm] or less. Moreover, as above-mentioned, the depth of all the recessed parts 8 arrange | positioned at the land parts 31-33 needs to exist in the range of the said 0.10 [mm] or more and less than 2.0 [mm].

  Further, 70 [%] or more, preferably 80 [%] or more of the recesses 8 disposed in the tread portion shoulder region has a depth larger than the average value Hdce of the depths of the recesses 8 in the tread portion center region. Is preferable, it is more preferable to have a depth of 110% or more, and it is more preferable to have a depth of 120% or more. That is, in the tread portion shoulder region, the depth of most of the concave portions 8 is set to be larger than the depth of the concave portion 8 in the tread portion center region. Thereby, the installation number of the deep recessed parts 8 in a tread part shoulder area | region is ensured, and the function of the deep recessed part 8 is ensured appropriately.

  In the configuration of FIG. 2, the boundary between the center region and the shoulder region of the tread portion is defined by the circumferential narrow groove 23 of the second land portion 32. For this reason, the block line on the tire equatorial plane CL side of the center land portion 31 and the second land portion 32 belongs to the tread portion center region, and the block row on the tire ground contact end T side of the second land portion 32 and the shoulder land portion 33 Belongs to the tread shoulder region.

  Also, two types of recesses 81 and 82 having different depths Hd1 and Hd2 (Hd1 <Hd2) are employed. Moreover, the shallow recessed part 81 is arrange | positioned at the block 5 in a tread part center area | region, and the deep recessed part 82 is arrange | positioned at the block 5 in a tread part shoulder area | region. As shown in FIGS. 3, 6 and 7, only the deep recess 82 is disposed in the block 5 of the tread shoulder region, and only the shallow recess 81 is disposed in the tread center region. For this reason, the depth of the recessed part 8 in each area | region is constant in any size.

  However, the present invention is not limited to this, and a plurality of types of recesses 81 and 82 may be mixed and disposed in one region (not shown). In this case, the depth of the recessed portion 8 of 70 [%] or more, preferably 80 [%] or more arranged in the center region of the tread portion is shallower than the average value of the recessed portions in the entire tread portion. It is preferable that the depth of the recess 8 of 70 [%] or more, preferably 80 [%] or more arranged in the shoulder region is deeper than the average depth of the recess in the entire tread portion. Thereby, the function by the uneven distribution of the depth of the recessed part 8 in each area | region is ensured appropriately.

  In the configuration of FIG. 2, the average value Hda1 of the depth of the concave portion 8 in the center land portion 31, the average value Hda2 of the depth of the concave portion 8 in the second land portion 32, and the depth of the concave portion 8 in the shoulder land portion 33. And the average value Hda3 of Hda1 <Hda2 <Hda3. Therefore, the average values Hda1 to Hda3 of the depths of the recesses 8 are smaller in the land portion on the tire equatorial plane CL side, and conversely, are larger in the land portion on the tire ground contact end T side. Thereby, the relationship Hdce <Hdsh of the average value of the depth of the recessed part 8 between the tread part center area | region and the tread part shoulder area | region is implement | achieved efficiently.

  In the configuration of FIG. 2, the average value Hda1 of the depth of the concave portion 8 in the center land portion 31 and the average depth of the concave portion 8 in the second land portion 32 in the left and right regions with the tire equator plane CL as a boundary. The value Hda2 and the average value Hda3 of the depth of the recess 8 in the shoulder land portion 33 may have a relationship of Hda1 <Hda3 <Hda2, respectively. In the second land portion 32 that contributes most to the driving performance and braking performance of the tire, the function of the concave portion 8 is effectively exhibited by setting the average depth Hda2 of the concave portion 8 large. Further, since the average values Hda1 and Hda3 of the depths of the concave portions 8 in the center land portion 31 and the shoulder land portion 33 have the relationship Hda1 <Hda3, the tread portion center region and the tread portion shoulder region The relationship of the average values of the depths of the recesses 8 Hdce <Hdsh is properly realized.

  In the configuration of FIG. 2, in FIG. 6, the average value Hda21 of the depth of the concave portion 8 in the tire width direction inner region of the second land portion 32 partitioned by the circumferential narrow groove 23 and the tire width direction outer region And the average value Hda22 of the depths of the recesses 8 have a relationship of Hda21 <Hda22. For this reason, the left and right regions having the circumferential narrow groove 23 of the second land portion 32 as a boundary have different ground characteristics. Moreover, the relationship Hdce <Hdsh of the average value of the depth of the recessed part 8 between a tread part center area | region and a tread part shoulder area | region is implement | achieved appropriately.

[Difference in the shape of the inner wall surface of the recess in the tire width direction]
8-12 is explanatory drawing which shows the inner wall surface shape of a recessed part. 8 to 12, the three-dimensional shape shown shows the inner wall surface shape of the recess 8, and the bottom surface of the three-dimensional shape in the drawing indicates the opening of the recess 8 with respect to the block tread surface, and the bottom or top of the upper portion of the drawing is The bottom of the recess 8 is shown. FIG. 13 is a cross-sectional view in the depth direction of the narrow shallow grooves and the recesses.

  As described above, the concave portion 8 may have a circular shape or an elliptical shape on the ground contact surface of the block 5, or may have a polygonal shape such as a quadrangular shape or a hexagonal shape. At this time, the recess 8 may have an arbitrary inner wall surface shape inside the block 5. Specifically, the inner wall surface shape of the recess 8 may have a three-dimensional shape such as a column shape, a frustum shape, a cone shape, or a hemispherical shape, or a columnar three-dimensional shape in which the bottom of the recess 8 is narrowed. You may have.

  For example, as shown in FIG. 4, when the concave portion 8 has a circular opening at the ground contact surface of the block 5, the inner wall surface shape of the concave portion 8 is a cylindrical shape (FIG. 8) or a truncated cone shape (FIG. 9). , A two-stage cylindrical shape (FIG. 10), a cylindrical shape in which the bottom of the concave portion 8 is narrowed into a truncated cone (FIG. 11), a cylindrical shape in which the bottom of the concave portion 8 is rounded into a spherical shape (FIG. 12), and a hemispherical shape (illustrated) May be omitted). The concave portion 8 having such an inner wall surface shape is preferable in that the processing is easy and the function of the concave portion 8 can be appropriately secured.

  Further, in the columnar concave portion 8 whose bottom is narrowed, as shown in FIGS. 10 to 12, the depth Hd of the concave portion 8 is measured using the maximum depth position of the concave portion 8 as a measurement point. As shown, the wall angle α of the recess 8 is measured as the angle formed by the ground contact surface of the block 5 and the inner wall surface of the recess 8 at the opening of the recess 8. The wall angle α of the recess 8 is preferably in the range of −85 [deg] ≦ α ≦ 95 [deg].

  Here, the volume of the recess 8 can be adjusted by the shape of the inner wall surface of the recess 8. For example, the volume of the cylindrical concave portion 8 shown in FIG. 8 is larger than the volume of the concave portion 8 having a narrowed bottom side shown in FIGS. 9 to 12 even if the depth Hd of the concave portion 8 is the same. . Therefore, the volume ratio of the recessed part 8 in each area | region of a tread part can be adjusted by using the multiple types of recessed part 8 which has mutually different inner wall surface shape. In general, if the opening area and depth Hd of the recess 8 are constant, the volume of the columnar recess 8 is larger than the volume of the recess 8 with the bottom of the recess 8 narrowed.

  For example, in the configuration of FIG. 2, the block 5 includes two types of concave portions 81 and 82 having different depths as described above, and the average value Hdce of the depth of the concave portion 8 in the tread portion center region and the tread portion shoulder. Since the average value Hdsh of the depths of the recesses 8 in the region has a relationship of Hdce <Hdsh, the volume ratio condition Vce <Vsh of the recesses 8 is satisfied.

  However, the present invention is not limited to this, and two types of recesses 81 and 82 having different volumes by using mutually different inner wall shapes are used, and the recess 8 having a relatively small volume is arranged in the tread portion center region. The recess 8 having a relatively large volume may be disposed in the tread shoulder region so that the volume ratio condition Vce <Vsh of the recess 8 may be satisfied. In this case, the volume of the recesses 8 of 70 [%] or more, preferably 80 [%] or more arranged in the center region of the tread is smaller than the average value of the recesses in the entire tread, and the tread shoulder It is preferable that the volume of the recesses 8 of 70 [%] or more, preferably 80 [%] or more arranged in the region is larger than the average value of the volume of the recesses in the entire tread portion. Thereby, the function by the uneven distribution of the volume of the recessed part 8 in each area | region is ensured appropriately.

  In said structure, the comparatively large recessed part 8 is arrange | positioned in the tread part shoulder area | region where a water film tends to generate | occur | produce at the time of driving | running | working on an ice road surface. Then, the water film on the tread surface on the ice road surface is efficiently absorbed by the water absorbing action of the concave portion 8. Thereby, the adhesiveness of the block tread with respect to an ice road surface improves, and the braking performance on ice of a tire improves. Moreover, since the comparatively small recessed part 8 is arrange | positioned in a tread part center area | region, the fall of the block rigidity resulting from arrangement | positioning of the recessed part 8 is relieve | moderated, and the steering stability performance of a tire improves.

  For example, in a configuration (see FIGS. 2, 3, 6 and 7) having two types of recesses 81 and 82 in the ground contact area of the tread, the first recess 81 has a truncated cone shape (see FIG. 9) and has two steps. The second recess 82 may have a cylindrical shape (see FIG. 8), with a three-dimensional shape with a narrowed bottom such as a cylindrical shape (see FIG. 10) or a cylindrical shape (FIG. 11 or FIG. 12). Moreover, each recessed part 8 has the same opening shape and the same opening area. Specifically, each recess 8 has a circular opening shape (see FIG. 4) and uniform outer diameters Dd1 and Dd2 (see FIG. 13). Moreover, as shown in FIG. 13, each recessed part 81 and 82 has uniform depth Hd1 and Hd2. For this reason, the first recessed portion 81 has a volume smaller than that of the second recessed portion 82 by the amount corresponding to the three-dimensional shape with the bottom portion narrowed. Further, only the concave portion 81 having a small volume is disposed in the tread portion center region, and only the concave portion 82 having a large volume is disposed in the tread portion shoulder region. Thereby, the condition Vce <Vsh of the volume ratio of the recessed part 8 in each area | region is satisfy | filled.

  Further, as shown in FIG. 13, the depths Hd1 and Hd2 of the two types of recesses 81 and 82 and the groove depth Hg of the thin shallow groove 7 are uniform (specifically, ± 10 [%] or less). Is set. For this reason, when wear progresses, the concave portions 81 and 82 and the shallow groove 7 on the block tread surface disappear at the same time.

  In the above configuration, 70 [%] or more, preferably 80 [%] or more of the recesses 8 arranged in the ground contact region of the tread is a columnar shape or a columnar inner wall surface shape in which the bottom side of the recesses is narrowed. And a wall angle α in the range of −85 [deg] ≦ α ≦ 95 [deg]. That is, most of the recesses 8 in the ground contact area of the tread have an inner wall surface shape substantially perpendicular to the tread surface of the block 5. Thereby, the edge effect | action and water absorption of the recessed part 8 improve effectively.

  In the above configuration, the two types of recesses 81 and 82 have mutually different inner wall shapes, but have uniform depths Hd1 and Hd2 (see FIG. 13). However, the present invention is not limited to this, and the two types of recesses 81 and 82 may have mutually different inner wall surface shapes, and may have mutually different depths Hd1 and Hd2 (not shown). As a result, the condition Vce <Vsh for the volume ratio of the recess 8 in each region and the condition Hdce <Hdsh for the average value of the depths may be satisfied simultaneously. This effectively increases the braking performance of the tire on ice.

[Modification]
14-20 is explanatory drawing which shows the modification of the tread of the block described in FIG. These drawings show the positional relationship between the sipe 6, the thin shallow groove 7, and the recess 8.

  In the configuration of FIG. 4, the narrow shallow grooves 7 are arranged to be inclined at a predetermined angle θ with respect to the tire circumferential direction. Such a configuration is preferable in that the inclined thin shallow grooves 7 cause edge components in both the tire circumferential direction and the tire width direction.

  However, the present invention is not limited to this, and the narrow shallow groove 7 may extend in parallel to the tire circumferential direction (see FIG. 14), or may extend in parallel to the tire width direction (see FIG. 15).

  Moreover, in the structure of FIG. 4, the thin shallow groove 7 has a linear shape. Such a configuration is preferable in that the thin shallow groove 7 can be easily formed.

  However, the present invention is not limited to this, and the thin shallow groove 7 may have a zigzag shape (see FIG. 16) or a wavy shape (see FIG. 17). At this time, as shown in FIGS. 16 and 17, the plurality of thin shallow grooves 7 may be arranged in phase with each other, or may be arranged out of phase with each other as shown in FIG. 18. Further, as shown in FIG. 19, the thin shallow groove 7 may have a short structure that is bent or curved. At this time, the short thin shallow grooves 7 may be arranged in series while being offset from each other (see FIG. 19), or may be arranged in a matrix (not shown). Further, the thin shallow groove 7 may have an arc shape (see FIG. 20) or may have a curved shape such as an S shape (not shown).

  Also in FIGS. 16 to 20, similar to the configurations of FIGS. 4, 14, and 15, the shallow groove 7 may be inclined at a predetermined angle θ with respect to the tire circumferential direction, or the tire circumferential direction May extend parallel to the tire width or may extend parallel to the tire width direction. When the thin shallow groove 7 has a zigzag shape or a wavy shape, the inclination angle θ of the thin shallow groove 7 is measured with reference to the center of the amplitude of the zigzag shape or the wavy shape.

  FIG. 21 and FIG. 22 are explanatory views showing modifications of the tread surface of the block shown in FIG. These drawings show the positional relationship between the sipe 6, the thin shallow groove 7, and the recess 8.

  In the configuration of FIG. 4, the thin shallow groove 7 has a linear structure extending in a predetermined direction. Such a configuration is preferable in that the thin shallow groove 7 can extend continuously over the entire area of the ground contact surface of the block 5.

  However, the present invention is not limited to this, and as shown in FIGS. 21 and 22, the thin shallow grooves 7 may have an annular structure and be arranged at a predetermined interval from each other. For example, the thin shallow groove 7 may have a polygonal shape (not shown) such as a circular shape (FIG. 21) or an elliptical shape (not shown), a rectangular shape (FIG. 22), a triangular shape, or a hexagonal shape. Also in such a configuration, the concave portion 8 is disposed across a plurality of adjacent thin shallow grooves 7 and 7 separated from each other.

  FIG. 23 is an explanatory view showing a modification of the tread of the block shown in FIG. This figure shows a cross-sectional view in the depth direction of the narrow shallow grooves 71 and 72 and the recess 8.

  In the configuration of FIG. 5, all the thin shallow grooves 7 have the same groove depth Hg.

  On the other hand, in the configuration of FIG. 23, the groove depth Hg1 of a part of the shallow grooves 71 is set to be shallower than the groove depth Hg2 of the reference shallow groove 72. In such a configuration, the thin shallow groove 71 having the shallow groove depth Hg1 disappears first and the thin shallow groove 72 having the deep groove depth Hg2 disappears after the tire wear progresses. Thereby, the property change of the block 5 by all the thin shallow grooves 7 disappearing simultaneously can be suppressed.

  24-27 is explanatory drawing which shows the modification of the tread of the block described in FIG. These drawings show the positional relationship between the sipe 6, the thin shallow groove 7, and the recess 8.

  In the configuration of FIG. 4, all the narrow grooves 7 are arranged in parallel to each other. For this reason, the thin shallow grooves 7 are arranged in a stripe shape without crossing each other.

  However, the present invention is not limited to this, and the thin shallow grooves 7 may be arranged so as to intersect or communicate with each other as shown in FIGS. For example, as shown in FIGS. 24 to 25, a plurality of narrow grooves 7 may be arranged in a mesh shape. At this time, the shallow grooves 7 may be arranged to be inclined with respect to the tire circumferential direction and the tire width direction (FIG. 24), or may be arranged in parallel to the tire circumferential direction and the tire width direction ( FIG. 25). Further, some of the thin shallow grooves 7 may be arranged curved, for example, in an arc shape or a wave shape (FIG. 26). Further, the narrow shallow grooves 7 may have an annular structure and be arranged in communication with each other (FIG. 27). For example, in the configuration of FIG. 27, the thin shallow grooves 7 are arranged in a honeycomb shape. Moreover, also in these structures, the recessed part 8 is arrange | positioned crossing the 2 or more thin shallow groove | channel 7 which does not cross | intersect mutually.

[Omission of narrow shallow grooves]
In the configuration of FIG. 2, the blocks 5 of all the land portions 31 to 33 are provided with a plurality of shallow grooves 7 on the tread. However, the present invention is not limited to this, and these thin shallow grooves 7 may be omitted.

  28 to 33 are explanatory views showing modifications of the pneumatic tire depicted in FIG. In these drawings, FIG. 28 is a plan view of the tread surface of the pneumatic tire 1, FIG. 29 is a plan view of the block 5 of the shoulder land portion 33 shown in FIG. 28, and FIG. FIG. 31 is a cross-sectional view perpendicular to the tread of the block 5 shown in FIG. 30. 32 schematically shows a plan view of the surface processed portion 9 applied to the tread surface of the block 5, and FIG. 33 schematically shows a cross-sectional view of the surface processed portion 9 in the height direction.

  As shown in FIGS. 28 and 29, the block 5 of the land portions 31 to 33 has an arithmetic average roughness Ra of 1 [μm] or more and 50 [μm] or less instead of the thin shallow groove 7 of FIG. 2. The processing unit 9 may be provided on the grounding surface. The arithmetic average roughness Ra is preferably in the range of 10 [μm] to 40 [μm]. In such a configuration, the water film interposed between the ice road surface and the tread surface is removed by the gap between the protrusions, and the frictional force between the road surface and the tread surface is increased by the protrusions. Thereby, the performance on ice and the performance on snow when a tire is new are improved.

  The arithmetic average roughness Ra is measured according to JIS B0601 (2001). In addition, the arithmetic average roughness Ra is measured by excluding the sipe 6, the concave portion 8, the notch, and the narrow groove formed in the land portion.

  For example, in the structure of FIG. 28, the surface processing part 9 shown in FIG. 32 and FIG. 33 is given to the grounding surface of all the blocks 5 of each land part 31-33. Further, the surface processed portion 9 has a structure in which fine and many hemispherical protrusions are scattered throughout the ground surface. Further, the maximum height Hp (see FIG. 33) of the protrusion is in the range of 1 [μm] to 50 [μm], and the maximum outer diameter Dp (see FIG. 32) of the protrusion is 1 [μm. ] And not more than 50 [μm]. Moreover, it is preferable that the average space | interval of the top part of an adjacent protrusion part exists in the range of 5 [micrometers] or more and 100 [micrometers] or less.

  As shown in FIGS. 32 and 33, the maximum height Hp and the maximum outer diameter Dp of the protrusion are defined by the outer contour line of the protrusion (defined by the intersection of the outer surface of the protrusion and the flat portion of the block). Is measured using, for example, a microscope.

  32 and 33, as described above, the protrusion of the surface processed portion 9 has a hemispherical shape. However, the present invention is not limited to this, and the protrusion of the surface processed portion 9 may have a trapezoidal shape such as a truncated hemispherical shape, a truncated cone shape, and a truncated pyramid shape, or a cylindrical shape, a prismatic shape, etc. It may have a rectangular cross section (not shown).

  In the configuration of FIG. 28, as described above, all the blocks 5 of the land portions 31 to 33 have the surface processing portion 9 described above in the entire tread surface. However, the present invention is not limited to this, and some or all of the blocks 5 of the land portions 31 to 33, or some or all of the treads of the block 5 may have a plain region having the surface processed portion 9. good. A plain region is defined as a region having an arithmetic average roughness Ra of less than 1 [μm].

  Here, a region having an arithmetic average roughness Ra of 50 [μm] or less is defined as a flat region. This flat region is a concept including both the region having the surface processed portion 9 and the plain region.

[effect]
As described above, the pneumatic tire 1 includes land portions 31 to 33 having ribs or a plurality of blocks on the tread surface (see FIG. 2). Further, the land portions 31 to 33 are provided with a plurality of types of concave portions 8 (81, 82) on the grounding surface having different volumes by having three-dimensional shapes in different depth directions. Further, the volume ratio Vce of the concave portion 8 in the tread portion center region and the volume ratio Vsh of the concave portion 8 in the tread portion shoulder region have a relationship of Vce <Vsh.

  With this configuration, (1) since the land portions 31 to 33 include the concave portions 8 on the ground contact surface, there is an advantage that the edge components of the land portions 31 to 33 are increased and the braking performance on the ice of the tire is improved. (2) In general, the tread shoulder region has a higher contact pressure than the tread center region, and a water film is likely to be generated when traveling on an icy road surface. At this time, by setting the volume ratio Vsh of the concave portion 8 in the tread portion shoulder region to be large, the water absorption of the tread surface in the tread portion shoulder region where a water film is likely to be generated is improved. Thereby, the adhesion of the block tread surface to the ice road surface is improved, and the braking performance on ice and the turning performance on ice are improved. In addition, (3) In general, the tread portion center region has a large contribution to the steering stability performance at a small steering angle of the tire, and also has a large contribution to the center feel during steering of the tire. Therefore, by setting the volume ratio Vce of the concave portion 8 in the tread portion center region to be small as described above, the decrease in the block rigidity due to the arrangement of the concave portion 8 is alleviated, and the steering stability performance of the tire is improved. There is also an advantage that the turning performance is improved. Moreover, (4) Since the recessed part 8 is shallow compared with a sipe (for example, linear sipe 6 or circular sipe (illustration omitted)), the rigidity of the land parts 31-33 is ensured appropriately. Thereby, there exists an advantage by which the braking performance on ice of a tire is ensured.

  In the pneumatic tire 1, the volume ratio Vce of the recess 8 in the center region of the tread and the volume ratio Vsh of the recess 8 in the shoulder region of the tread have a relationship of 1.10 ≦ Vsh / Vce. Thereby, there is an advantage that the ratio Vsh / Vce of the volume ratio of the concave portion 8 in each region is ensured, and the action due to the uneven distribution of the volume ratio of the concave portion 8 can be obtained appropriately.

  Further, in the pneumatic tire 1, the opening area ratio Sce of the recess 8 in the tread portion center region and the opening area ratio Ssh of the recess 8 in the tread portion shoulder region satisfy 0.90 ≦ Ssh / Sce ≦ 1.10. There is a relationship (see FIG. 2). Thereby, there is an advantage that a difference can be formed in the volume ratios Vce and Vsh of the recesses 8 in each region while making the ground contact area in each region of the tread portion uniform.

  Moreover, in this pneumatic tire 1, the arrangement density Dce of the recesses 8 in the tread portion center region and the arrangement density Dsh of the recesses 8 in the tread portion shoulder region satisfy a relationship of 0.90 ≦ Dsh / Dce ≦ 1.10. (See FIG. 2). In such a configuration, since the arrangement density of the recesses 8 is made uniform in each region in the tire width direction, there is an advantage that an excessive change in the ground contact characteristics of the land portion due to the uneven distribution of the volume ratios Vce and Vsh of the recesses 8 can be suppressed. is there.

  Further, in the pneumatic tire 1, the maximum value A_max and the minimum value A_min of the opening area of the recesses 8 arranged in the entire tread portion have a relationship of 1.00 ≦ A_max / A_min ≦ 1.10. 2). In such a configuration, since the opening area of each recess 8 is made uniform throughout the tread portion, there is an advantage that an excessive change in grounding characteristics due to variation in the opening area of the recess 8 can be suppressed.

  Moreover, in this pneumatic tire 1, the land parts 31-33 are provided with the multiple types of recessed part 8 (81, 82) which has mutually different volume by having mutually different depth Hd1, Hd2 (refer FIG. 5). ). In addition, the average value Hdce of the depth of the recess 8 in the center region of the tread and the average value Hdsh of the depth of the recess 8 in the shoulder region of the tread have a relationship of Hdce <Hdsh (see FIG. 2). (1) Generally, in the tread portion shoulder region, the contact pressure is higher than that in the tread portion center region, and a water film is likely to be generated when traveling on an icy road surface. At this time, by setting the average value Hdsh of the depth of the concave portion 8 in the tread shoulder region to be large, the water absorption of the tread surface in the tread shoulder region where a water film is likely to be generated is improved. Thereby, the adhesion of the block tread surface to the ice road surface is improved, and the braking performance on ice and the turning performance on ice are improved. In addition, (2) In general, the tread portion center region has a large contribution to the steering stability performance at a small steering angle of the tire, and also has a large contribution to the center feel during steering of the tire. Therefore, as described above, by setting the average value Hdce of the depth of the concave portion 8 in the tread portion center region to be small, the decrease in the block rigidity due to the arrangement of the concave portion 8 is alleviated, and the steering stability performance of the tire is improved. There is an advantage to improve, and there is an advantage to improve the turning performance.

  Further, in this pneumatic tire 1, the average value Hdce of the depth of the recess 8 in the center region of the tread and the average value Hdsh of the depth of the recess 8 in the shoulder region of the tread satisfy 1.10 ≦ Hdsh / Hdce. Have a relationship. Thereby, there is an advantage that the ratio Hdsh / Hdce of the average value of the depth of the recess 8 in each region is ensured, and the effect of improving the braking performance on ice by the recess 8 can be obtained appropriately.

  Further, in the pneumatic tire 1, 70 [%] or more of the recesses 8 arranged in the center region of the tread portion is 50 [%] or more and 150 [%] or less with respect to the groove depth Hg of the thin shallow groove 7. It has a depth Hd. In such a configuration, most of the recesses 8 in the center region of the tread portion disappear at the same time as the thin shallow grooves 7 as the tire wear progresses. Thereby, there is an advantage that a sufficient contact area of the tread portion can be ensured when the surface of the contact area of the tread rubber is worn and a sufficient function is exhibited.

  Moreover, in this pneumatic tire 1, 70 [%] or more of the recessed part 8 arrange | positioned at a tread part shoulder area | region has the depth Hd larger than the average value Hdce of the depth of the recessed part 8 in a tread part center area | region ( (See FIG. 2). Thereby, the installation number of the deep recessed part 8 in a tread part shoulder region is ensured, and there exists an advantage by which the function of the deep recessed part 8 is ensured appropriately.

  Moreover, in this pneumatic tire 1, land part 31-33 is provided with several types of recessed part 8 (81, 82) which has mutually different volume by having mutually different inner wall surface shape (refer FIG. 13). Moreover, 70 [%] or more of the recessed part 8 arrange | positioned in a tread part shoulder area | region has a volume larger than the average value Hdc of the volume of the recessed part 8 in a tread part center area | region. Thereby, the installation number of the large volume recessed parts 8 in a tread part shoulder region is ensured, and there exists an advantage by which the function of the deep recessed part 8 is ensured appropriately.

  Further, in this pneumatic tire 1, 70 [%] or more of the recesses 8 arranged in the entire tread portion is a column shape (for example, a cylindrical shape in FIG. 8) or a column shape in which the bottom side of the recess 8 is narrowed. It has an inner wall surface shape (for example, a two-stage cylindrical shape in FIG. 10 and a cylindrical shape in which the bottom side in FIGS. 11 and 12 is conical or hemispherical) and −85 [deg] ≦ α ≦ 95. It has a wall angle α (see FIG. 13) in the range of [deg]. Thereby, there exists an advantage which the edge effect | action and water absorption of the recessed part 8 improve effectively.

  Moreover, in this pneumatic tire 1, the depth of the recessed part 8 (81, 82) exists in the range of 0.10 [mm] or more and less than 2.0 [mm]. Thereby, there exists an advantage by which the depth of the recessed part 8 is optimized. That is, the function of the concave portion 8 is appropriately secured by the lower limit of the numerical range, and the rigidity of the land portions 31 to 33 is appropriately secured by the upper limit of the numerical range.

  Further, in this pneumatic tire 1, the arrangement density Da of the recesses 8 over the entire area of one continuous ground contact surface is 0.8 [piece / cm ^ 2] ≦ Da ≦ 4.0 [piece / cm ^ 2]. Is in range. Thereby, there exists an advantage by which the arrangement density of the recessed part 8 is optimized. That is, when 0.8 [pieces / cm ^ 2] ≦ Da, the number of the recessed portions 8 is ensured, and the water film removing action is appropriately secured in the recessed portions 8. In addition, since Da ≦ 4.0 [pieces / cm 2], the ground contact areas of the land portions 31 to 33 are appropriately secured.

  In addition, the pneumatic tire 1 includes four or more circumferential main grooves 21 and 22 and five or more rows of land portions 31 to 33 defined by the circumferential main grooves 21 and 22 (see FIG. 2). ). The distance between the left and right outermost main grooves 22 and 22 and the tire equatorial plane CL is in the range of 28 [%] to 38 [%] of the tire ground contact width. Further, the volume ratio V1 of the concave portion 8 in the land portion 31 (see FIG. 2) on the tire equator plane CL or the land portion (not shown) partitioned in the circumferential main groove on the tire equator plane CL, and the outermost periphery The volume ratio V2 of the concave portion 8 in the land portion 32 on the inner side in the tire width direction partitioned by the direction main groove 22 and the volume ratio V3 of the concave portion 8 in the land portion 33 on the outer side in the tire width direction partitioned by the outermost circumferential direction main groove 22. Have a relationship of V1 <V2 and V3 <V2. In general, the second land portion 32 greatly contributes to the braking performance and driving performance of the tire. Therefore, by setting the volume ratio V2 of the concave portion 8 in the second land portion 32 to be high, there is an advantage that the water absorption action of the concave portion 8 is effectively exhibited and the braking performance on ice of the tire is effectively improved.

  In addition, the pneumatic tire 1 includes four or more circumferential main grooves 21 and 22 and five or more rows of land portions 31 to 33 defined by the circumferential main grooves 21 and 22 (see FIG. 2). ). The distance between the left and right outermost main grooves 22 and 22 and the tire equatorial plane CL is in the range of 28 [%] to 38 [%] of the tire ground contact width. Further, the volume ratio V1 of the concave portion 8 in the land portion 31 (see FIG. 2) on the tire equator plane CL or the land portion (not shown) partitioned in the circumferential main groove on the tire equator plane CL, and the outermost periphery The volume ratio V3 of the concave portion 8 in the land portion 33 on the outer side in the tire width direction partitioned by the direction main groove 22 has a relationship of V1 <V3. In general, in the shoulder land portion 33, compared to the center land portion 31, the contact pressure is relatively high and a water film tends to be easily generated on the ice road surface. Therefore, as shown in FIG. 2, the volume ratio V3 of the recess 8 of the shoulder land portion 33 is set to be relatively higher than the volume ratio V1 of the recess 8 of the center land portion 31 (V1 <V3). There is an advantage that the water removal performance of the portion 33 is efficiently enhanced and the braking performance on ice of the tire is improved. Further, as described above, the opening area ratio Sin of the concave portion 8 in the inner region in the vehicle width direction is set to be relatively higher (Sout <Sin) than the opening area ratio Sout of the concave portion 8 in the outer region in the vehicle width direction. When the tire is mounted on a vehicle having a negative camber, there is an advantage that the braking performance on ice is improved. By these synergistic actions, there is an advantage that the braking performance on ice of the tire is effectively improved.

  FIG. 34 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  In this performance test, evaluations on (1) on-ice braking performance and (2) on-ice turning performance were performed for a plurality of types of test tires. Further, a test tire having a tire size of 195 / 65R15 is assembled to an applicable rim defined by JATMA, and an air pressure of 230 [kPa] and a maximum load defined by JATMA are applied to the test tire. Further, the test tire is mounted on a sedan having a displacement of 1600 [cc] and a front engine front drive (FF) system, which is a test vehicle.

  (1) In the evaluation on the on-ice braking performance, the test vehicle travels on a predetermined ice road surface, and the braking distance from the traveling speed 40 [km / h] is measured. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation is preferable as the numerical value increases.

  (2) In the evaluation relating to the turning performance on ice, the test vehicle performs turning along a circle having a radius of 4 [m], and the traveling time is measured. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation is preferable as the numerical value increases.

  34, the test tires of Examples 1 to 8 have the configurations of FIGS. 1 and 2, and the blocks 5 of the land portions 31 to 33 have sipes 6, thin shallow grooves 7, and recesses 8, respectively. The depth of the sipe 6 is 6.0 [mm]. Further, as shown in FIG. 4, linear thin shallow grooves 7 are arranged in parallel while being inclined in the tire circumferential direction and penetrate the block 5. The arrangement interval of the narrow shallow grooves 7 is P = 1.2 [mm]. Moreover, all the recessed parts 8 in a tread surface have a circular opening part, and have a fixed (3.2 [mm ^ 2]) opening area. Further, the arrangement density Dce of the recesses 8 in the tread part center region is equal to the arrangement density Dsh of the recesses 8 in the tread part shoulder region (Nce = Nsh). In addition, the average value of the arrangement density Da of the recesses 8 in the entire tread is 2.0 [pieces / cm 2]. Moreover, all the recessed parts 8 have a cylindrical shape (refer FIG. 8) inner wall surface shape. Further, the volume ratio Vce of the concave portion 8 in the tread portion center region and the volume ratio Vsh of the concave portion 8 in the tread portion shoulder region have a relationship of Vce <Vsh. In the test tire of Example 8, in the configuration of Example 2, the tread surface of the block 5 was replaced with the thin shallow groove 7 and the surface processed portion 9 having an average arithmetic roughness Ra of 20 [μm] (FIGS. 28 to 28). 33). In the table, “CE” indicates a tread portion center region, and “SH” indicates a tread portion shoulder region.

  In the test tire of the conventional example, in the configuration of FIG. 2, the block 5 has only the sipe 6 and the thin shallow groove 7, and does not have the concave portion 8.

  As shown in the test results, it can be seen that in the test tires of Examples 1 to 8, the braking performance on ice and the turning performance on ice are improved.

  1: Pneumatic tire, 21, 22: circumferential main groove, 23: circumferential narrow groove, 31-33: land portion, 311: notch portion, 41-43: lug groove, 5: block, 6: sipe, 7 : Thin shallow groove, 8: Recessed part, 9: Surface processed part, 11: Bead core, 12: Bead filler, 13: Carcass layer, 14: Belt layer, 141, 142: Cross belt, 143: Belt cover, 15: Tread rubber , 16: side wall rubber, 17: rim cushion rubber

Claims (15)

In a pneumatic tire provided with a land part having a rib or a plurality of blocks on a tread surface,
The land portion is provided with a plurality of types of recesses on the ground plane having different volumes by having three-dimensional shapes in different depth directions,
Defining the ratio of the sum of the volumes of the recesses in a predetermined area and the contact area of the land as the volume ratio of the recesses; and
A pneumatic tire characterized in that a volume ratio Vce of the recess in the tread center region and a volume ratio Vsh of the recess in the tread shoulder region have a relationship of Vce <Vsh.   2. The pneumatic tire according to claim 1, wherein a volume ratio Vce of the recess in the tread portion center region and a volume ratio Vsh of the recess in the tread shoulder region have a relationship of 1.10 ≦ Vsh / Vce.   The opening area ratio Sce of the concave portion in the tread portion center region and the opening area ratio Ssh of the concave portion in the tread portion shoulder region have a relationship of 0.90 ≦ Ssh / Sce ≦ 1.10. 2. The pneumatic tire according to 2. Defining the ratio of the number of the recessed portions arranged in a predetermined region and the contact area of the land portion as the placement density of the recessed portions; and
The arrangement density Dce of the concave portions in the tread portion center region and the arrangement density Dsh of the concave portions in the tread portion shoulder region have a relationship of 0.90 ≦ Dsh / Dce ≦ 1.10. The pneumatic tire according to any one of the above.   The maximum value A_max and the minimum value A_min of the opening area of the recesses arranged in the entire tread portion have a relationship of 1.00 ≦ A_max / A_min ≦ 1.10. The described pneumatic tire. The land portion includes a plurality of types of the recesses having different volumes by having different depths, and
The average value Hdce of the depth of the recessed portion in the tread portion center region and the average value Hdsh of the depth of the recessed portion in the tread portion shoulder region have a relationship of Hdce <Hdsh. The pneumatic tire according to one.   The average value Hdce of the depth of the concave portion in the tread portion center region and the average value Hdsh of the depth of the concave portion in the tread portion shoulder region have a relationship of 1.10 ≦ Hdsh / Hdce. The described pneumatic tire. The land portion includes a plurality of shallow grooves,
10 or 7 of the concave portion disposed in the center region of the tread portion has a depth of 50% or more and 150% or less with respect to a depth of the narrow shallow groove. Pneumatic tire described in 2.   The depth of 70 [%] or more of the said recessed part arrange | positioned at the said tread part shoulder region has a depth larger than the average value Hdce of the depth of the said recessed part in the said tread part center area | region. Pneumatic tire described in one. The land portion includes a plurality of types of the recesses having mutually different volumes by having mutually different inner wall surface shapes, and
The 70% or more of the recesses arranged in the tread shoulder region have a volume larger than an average value of the recesses in the tread center region. Pneumatic tires.   70 [%] or more of the recesses arranged in the entire tread portion have a columnar shape or a columnar inner wall shape constricted on the bottom side of the recess, and −85 [deg] ≦ α ≦ 95 [ The pneumatic tire according to any one of claims 1 to 10, which has a wall angle α in a range of deg].   The pneumatic tire according to any one of claims 1 to 11, wherein a depth of the recess is in a range of 0.10 [mm] or more and less than 2.0 [mm].   The arrangement density Da of the concave portions over the entire area of one continuous ground contact surface is in the range of 0.8 [pieces / cm ^ 2] ≦ Da ≦ 4.0 [pieces / cm ^ 2]. The pneumatic tire according to any one of the above. Comprising four or more circumferential main grooves and five or more rows of land portions defined by the circumferential main grooves; and
The left and right circumferential main grooves on the outermost side in the tire width direction are defined as outermost circumferential main grooves,
The distance between the left and right outermost circumferential main grooves and the tire equatorial plane is in the range of 28 [%] to 38 [%] of the tire ground contact width;
The volume ratio V1 of the concave portion in the land portion on the tire equator plane or the land portion on the tire equator plane, and the tire width direction on the outermost circumferential main groove. The volume ratio V2 of the recess in the land portion on the inner side and the volume ratio V3 of the recess in the land portion on the outer side in the tire width direction defined in the outermost circumferential main groove satisfy V1 <V2 and V3 <V2. The pneumatic tire according to any one of claims 1 to 13, which has a relationship. Comprising four or more circumferential main grooves and five or more rows of land portions defined by the circumferential main grooves; and
The left and right circumferential main grooves on the outermost side in the tire width direction are defined as outermost circumferential main grooves,
The distance between the left and right outermost circumferential main grooves and the tire equatorial plane is in the range of 28 [%] to 38 [%] of the tire ground contact width;
The volume ratio V1 of the concave portion in the land portion on the tire equator plane or the land portion on the tire equator plane, and the tire width direction on the outermost circumferential main groove. The pneumatic tire according to any one of claims 1 to 14, wherein a volume ratio V3 of the concave portion in the outer land portion has a relationship of V1 <V3.

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