JP2018203053A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire capable of improving durability performance of a block.SOLUTION: A pneumatic tire 1 comprises a main groove 2 and land parts 3 partitioned by the main groove 2 (especially, blocks 5 partitioned in a tire circumferential direction) (refer to Fig. 2). The land part 3 comprises a circumferential narrow groove 6 extended in a tire circumferential direction and plural sipings 7 arranged on at least one area out of the land part 3 partitioned by the circumferential narrow groove 6 (refer to Fig. 3). In addition, a groove cross section of the circumferential narrow groove 6 is varied as approaching to the tire circumferential direction. When a point Pn on a groove center line where the groove cross section area of the circumferential narrow groove 6 becomes maximum, and a point Ps on an end part on the circumferential narrow groove 6 on the siping 7 are defined, a position of the point Pn of the circumferential narrow groove 6 in the tire circumferential direction is between points Ps, Ps of the sipings 7 adjacent in the tire circumferential direction (refer to Fig. 4).SELECTED DRAWING: Figure 3

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can improve the durability of a block.

  In recent studless tires, in order to make the contact pressure of the whole block uniform and improve the durability performance (especially load durability performance) of the block, the circumferential narrow groove is arranged particularly in the central portion of the shoulder block. As a conventional pneumatic tire employing such a configuration, a technique described in Patent Document 1 is known.

Japanese Patent No. 2812999

  However, even in the above configuration, the ground contact pressure at the center portion still tends to be high when comparing the ground contact pressure between the center portion of the ground contact area of the shoulder block and the left and right edge portions. In particular, this tendency becomes significant in a configuration in which a plurality of sipes do not communicate with the circumferential narrow groove.

  Therefore, the present invention has been made in view of the above, and an object thereof is to provide a pneumatic tire capable of improving the durability performance of a block.

  In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire including a main groove and a land portion defined in the main groove, and the land portion extends in a tire circumferential direction. A circumferential narrow groove, and a plurality of sipes disposed in at least one region of the land portion partitioned by the circumferential narrow groove, the groove cross-sectional area of the circumferential narrow groove being in the tire circumferential direction. Defining a point Pn on the groove center line at which the groove cross-sectional area of the circumferential narrow groove is maximized, and a point Ps at the end of the sipe on the circumferential narrow groove side, The position of the circumferential narrow groove point Pn in the tire circumferential direction is between the sipe points Ps and Ps adjacent to each other in the tire circumferential direction.

  In the pneumatic tire according to the present invention, the groove cross-sectional area of the circumferential narrow groove has a maximum value between the points Ps and Ps at the ends of the adjacent sipes, and therefore, between the adjacent sipes and the circumferential narrow grooves. The ground contact pressure on the tread of the block is effectively distributed. Thereby, the ground contact pressure of the whole block is effectively equalized, and there exists an advantage which the durable performance of a block improves.

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 enlarged view showing the block shown in FIG. FIG. 4 is an enlarged plan view showing the circumferential narrow grooves and sipes described in FIG. 3. FIG. 5 is a cross-sectional view showing the circumferential narrow grooves and sipes described in FIG. 3. FIG. 6 is an explanatory diagram illustrating a modification of the circumferential narrow groove illustrated in FIG. 4. FIG. 7 is an explanatory diagram illustrating a modification of the circumferential narrow groove illustrated in FIG. 4. FIG. 8 is an explanatory view showing a modified example of the circumferential narrow groove described in FIG. 4. FIG. 9 is an explanatory view showing a modification of the circumferential narrow groove shown in FIG. FIG. 10 is an explanatory view showing a modification of the circumferential narrow groove shown in FIG. FIG. 11 is an explanatory view showing a modification of the circumferential narrow groove shown in FIG. FIG. 12 is an explanatory view showing a modification of the circumferential narrow groove shown in FIG. FIG. 13 is an explanatory view showing a modification of the circumferential narrow groove shown in FIG. 3. FIG. 14 is an explanatory diagram illustrating a modification of the circumferential narrow groove illustrated in FIG. 3. FIG. 15 is an explanatory diagram illustrating a modification of the circumferential narrow groove illustrated in FIG. 3. FIG. 16 is an explanatory diagram illustrating a modification of the circumferential narrow groove illustrated in FIG. 3. FIG. 17 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 passenger car studless tire 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, 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 has an annular structure in which one or a plurality of bead wires made of steel are wound in multiple layers, and are embedded in the bead portions to constitute the cores 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 A carcass angle (defined as the inclination angle of the carcass cord in the longitudinal direction 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 intersecting belts 141 and 142 have belt angles with different signs (defined as inclination angles in the longitudinal direction of the belt cord with respect to the tire circumferential direction), and intersect the longitudinal directions of the belt cords with each other. (So-called cross-ply structure). The belt cover 143 is configured by covering a belt cord made of steel or an organic fiber material with a coat rubber, and has a belt angle of 0 [deg] or more and 10 [deg] or less in absolute value. The belt cover 143 is, for example, a strip material formed by coating one or a plurality of belt cords with a coat rubber. The strip material is applied to the outer circumferential surface of the cross belts 141 and 142 a plurality of times in the tire circumferential direction. In addition, it is configured to be spirally wound.

  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 arranged 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 a rim fitting surface of the bead portion.

[Tread pattern]
FIG. 2 is a plan view showing a tread surface of the pneumatic tire depicted in FIG. 1. This figure shows a typical block pattern. In the figure, the tire circumferential direction refers to the direction around the tire rotation axis. Further, the symbol T is a tire ground contact end, and the dimension symbol TW is a tire ground contact width.

  As shown in FIG. 2, the pneumatic tire 1 includes a plurality of circumferential main grooves 2 extending in the tire circumferential direction, a plurality of land portions 3 partitioned by the circumferential main grooves 2, and the land A plurality of lug grooves 4 arranged in the portion 3 are provided on the tread surface.

  The main groove is a groove having a duty of displaying the wear indicator defined in JATMA, and has a groove width of 3.0 [mm] or more and a groove depth of 5.0 [mm] or more. The lug groove is a lateral groove extending in the tire width direction, has a groove width of 1.0 [mm] or more and a groove depth of 3.0 [mm] or more, and is opened when the tire contacts the ground. Functions as a groove.

  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. When the land part has a notch or chamfered part at the edge part, the groove width with the intersection of the tread tread and the extension line of the groove wall as a measurement point in a cross-sectional view with the groove length direction as the normal direction Is measured. Further, 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 using the center line of the amplitude of the groove wall as a measurement point.

  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.

  Of the two or more circumferential main grooves (including the circumferential main grooves arranged on the tire equator plane CL) arranged in one region with the tire equator plane CL as a boundary, the tire width direction The outermost circumferential main groove is defined as the outermost circumferential main groove. The outermost circumferential main grooves are respectively defined in left and right regions with the tire equatorial plane CL as a boundary. The distance from the tire equatorial plane CL to the outermost circumferential main groove (dimensional symbol omitted in the figure) is in the range of 20% to 35% of the tire ground contact width TW.

  The tire ground contact width TW is the contact surface between the tire and the flat plate when the tire is mounted on the specified rim to apply 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. It is measured as the maximum linear distance in the tire axial direction.

  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.

  Further, the land portion 3 on the outer side in the tire width direction defined by the outermost circumferential main groove 2 is defined as a shoulder land portion. The shoulder land portion 3 is the outermost land portion in the tire width direction and is located on the tire ground contact edge T.

  In the configuration of FIG. 2, each land portion 3 includes a plurality of lug grooves 4 as described above. The lug grooves 4 have an open structure that penetrates the land portion 3 and are arranged at predetermined intervals in the tire circumferential direction. Thereby, all the land portions 3 are divided by the lug grooves 4 in the tire circumferential direction, and a block row including a plurality of blocks 5 is formed. However, the present invention is not limited to this, and the land portion 3 may be a rib that continues in the tire circumferential direction (not shown).

  In FIG. 2, it is preferable that the ground contact width Wb of the block 5 and the tire ground contact width TW have a relationship of 0.15 ≦ Wb / TW. Thereby, the ground contact width Wb of the block 5 is ensured appropriately.

  The contact width Wb of the block is the contact between the block and the flat plate when the tire is mounted on the specified rim to apply the specified internal pressure and the load corresponding to the specified load is applied in a stationary state perpendicular to the flat plate. It is measured as the maximum linear distance in the tire axial direction on the surface.

  In the configuration of FIG. 2, the circumferential main grooves 2 and the lug grooves 4 are arranged in a lattice pattern to form a rectangular block 5. However, the block 5 can have any shape. For example, the circumferential main groove 2 may have a zigzag shape having an amplitude in the tire width direction, and the lug groove 4 may have a bent or curved shape (not shown). Further, for example, the pneumatic tire 1 is adjacent to 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 2 and the lug grooves 4 in FIG. 2. You may provide the lug groove which makes an inclination main groove communicate, and the some block comprised by these inclination main groove and lug groove (illustration omitted). In these configurations, the block may have a long and complex shape.

[Block circumferential grooves and sipes]
FIG. 3 is an enlarged view showing the block shown in FIG. The figure shows a plan view of a single block 5 in the shoulder land portion 3.

  As shown in FIG. 3, the block 5 includes one circumferential narrow groove 6 and a plurality of sipes 7.

  The circumferential narrow groove 6 is a narrow groove extending in the tire circumferential direction. At the time of tire contact, the contact pressure in the central portion of the block 5 is reduced by the circumferential narrow groove 6 and the contact pressure of the entire block 5 is made uniform. Thereby, the durability performance of the block 5 improves.

  For example, in the configuration of FIG. 3, one block 5 includes a single circumferential narrow groove 6. However, the present invention is not limited to this. For example, when the block 5 has a long structure, one block 5 may include a plurality of circumferential narrow grooves 6 (not shown). The circumferential narrow groove 6 will be described in detail later.

  The sipe 7 is an incision formed in the tread surface, and has a sipe width of less than 1.0 [mm] and a sipe depth of 2.0 [mm] or more, and closes when the tire contacts the ground. A plurality of sipes 7 are arranged in at least one region of the block 5 defined by the circumferential narrow grooves 6. When the tire is in contact with the ground, the sipe 7 absorbs and removes the water film on the icy road surface, thereby improving the adhesion (so-called adhesion frictional force) of the tread surface of the block 5 to the icy road surface. Thereby, the performance on ice of a tire improves.

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

  The sipe depth is measured as the maximum value of the distance from the tread surface to the sipe bottom in a no-load state in which a tire is mounted on a specified rim and filled with a specified internal pressure. Further, in the configuration in which the sipe has a partially uneven portion at the groove bottom, the sipe depth is measured excluding these.

  For example, in the configuration of FIG. 3, the sipe 7 has a zigzag shape extending in the tire width direction and having an amplitude in the tire circumferential direction. However, the present invention is not limited to this, and the sipe 7 may have a straight shape. In the configuration of FIG. 3, the plurality of sipes 7 are respectively disposed in the left and right regions of the block 5 partitioned by the circumferential narrow grooves 6. These sipes 7 are arranged in parallel to each other in the tire circumferential direction.

  Further, as shown in FIG. 3, it is preferable that the plurality of sipes 7 do not communicate with the circumferential narrow groove 6. Thereby, the rigidity of the block 5 is ensured and the durability performance of the block is ensured. The positional relationship between the sipe 7 and the circumferential narrow groove 6 will be described in detail later.

  Further, in the configuration of FIG. 3, all sipes 7 are terminated inside the block 5 without opening at the edge portion on the circumferential main groove 2 side of the block 5 or the tire ground contact end T. However, the present invention is not limited to this, and part or all of the sipes 7 may be opened at the edge portion of the block 5 or the tire ground contact end T (not shown).

[Branch of circumferential narrow groove]
In recent studless tires, in order to improve the durability of the block by making the contact pressure of the entire block uniform, the circumferential narrow groove is arranged particularly at the center of the shoulder block.

  However, even in the above configuration, the ground contact pressure at the center portion still tends to be high when comparing the ground contact pressure between the center portion of the ground contact area of the shoulder block and the left and right edge portions. In particular, this tendency becomes significant in a configuration in which a plurality of sipes do not communicate with the circumferential narrow groove.

  Therefore, this pneumatic tire adopts the following configuration in order to make the contact pressure of the entire block uniform.

  4 and 5 are an enlarged plan view (FIG. 4) and a cross-sectional view (FIG. 5) showing the circumferential narrow grooves and sipes described in FIG. 3.

  As shown in FIG. 3, the circumferential narrow groove 6 has a main portion 61 and a plurality of branch portions 62.

  The main portion 61 is a groove portion extending in the tire circumferential direction and constitutes a main body of the circumferential narrow groove 6.

  The opening width Wn1 (see FIG. 4) of the main portion 61 is preferably in the range of 0.5 [mm] ≦ Wn1 ≦ 3.0 [mm], and 1.0 [mm] ≦ Wn1 ≦ 1. More preferably, it is in the range of 5 [mm]. Thereby, the opening width Wn1 of the main part 61 is optimized.

  The opening width Wn1 of the main part is measured as the maximum value of the distance between the left and right groove walls in the opening of the main part in a no-load state in which the tire is mounted on the specified rim and filled with the specified internal pressure. In the configuration in which the circumferential narrow groove has a notch portion or a chamfered portion at the edge portion, in a cross-sectional view in which the groove length direction is a normal direction, the intersection of the tread surface and the extension line of the groove wall is used as a measurement point. The opening width Wn1 of the main part is measured. Therefore, the notch portion and the chamfered portion are excluded, and the opening width Wn1 of the main portion is measured.

  Further, the maximum depth Hn1 (see FIG. 5) of the main portion 61 and the maximum groove depth H0 (not shown) of the main groove 2 have a relationship of 0.05 ≦ Hn1 / H0 ≦ 0.40. Preferably, it has a relationship of 0.10 ≦ Hn1 / H0 ≦ 0.20. The maximum depth Hn1 of the main portion 61 is preferably in the range of 0.3 [mm] ≦ Hn1 ≦ 2.0 [mm]. Thereby, the maximum depth Hn1 of the main part 61 is optimized. In the configuration of FIG. 5, the maximum depth Hn1 of the main portion 61 is shallower than the maximum depth Hs of the sipe 7 and has a relationship of 0.10 ≦ Hn1 / Hs ≦ 0.40.

  The maximum depth of the main portion 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.

  For example, in the configuration of FIG. 3, the block 5 includes a single circumferential narrow groove 6, and the main portion 61 of the circumferential narrow groove 6 is disposed at the center of the block 5 in the tire width direction. Specifically, the relationship between the distance W1 from the measurement point of the ground contact width Wb of the block 5 to the groove center line of the main portion 61 and the ground contact width Wb of the block 5 is 0.40 ≦ W1 / Wb ≦ 0.60. It is preferable to have. Thereby, the contact pressure at the center of the block 5 is effectively relieved by the circumferential narrow groove 6.

  In the configuration of FIG. 3, the main portion 61 of the circumferential narrow groove 6 has a straight shape. However, the present invention is not limited to this, and the main portion 61 has, for example, a zigzag shape or a wavy shape having an amplitude in the tire width direction, a bent shape or an arc shape protruding in the tire width direction, a shape having a step-like bent portion, or the like. You may have (illustration omitted).

  In the configuration of FIG. 3, the main portion 61 of the circumferential narrow groove 6 has a constant opening width Wn1 (see FIG. 4). However, the present invention is not limited to this, and the opening width Wn1 of the main portion 61 may change as it goes in the tire circumferential direction (not shown). For example, the opening width Wn1 of the main portion 61 may increase monotonously or decrease monotonously in the tire circumferential direction.

  In the configuration of FIG. 3, the main portion 61 of the circumferential narrow groove 6 is opened to the front and rear edge portions of the block 5 in the tire circumferential direction at both ends. Therefore, the block 5 is penetrated in the tire circumferential direction. Thereby, the drainage of the block 5 is enhanced by the circumferential narrow groove 6. However, the present invention is not limited to this, and the main portion 61 of the circumferential narrow groove 6 opens at the edge portion in the tire circumferential direction of the block 5 at one end portion and ends inside the block 5 at the other end portion. (Not shown). The main portion 61 of the circumferential narrow groove 6 may be terminated inside the block 5 at both ends (not shown). In such a configuration, the main portion 61 of the circumferential narrow groove 6 does not penetrate the block 5, whereby the rigidity of the edge portion of the block 5 in the tire circumferential direction is ensured.

  The branch part 62 branches from the main part 61 in the tire width direction and enlarges the opening width Wn (see FIG. 4) of the circumferential narrow groove 6. Thereby, the groove | channel cross-sectional area of the circumferential direction fine groove 6 is partially expanded by the some branch part 62, and changes as it goes to a tire circumferential direction.

  Further, the maximum depth Hn2 (see FIG. 5) of the branch part 62 and the maximum depth Hn1 of the main part 61 preferably have a relationship of 0.10 ≦ Hn2 / Hn1 ≦ 0.50, and 0.20 It is more preferable to have a relationship of ≦ Hn2 / Hn1 ≦ 0.45. The maximum depth Hn2 of the branch part 62 is preferably in the range of 0.1 [mm] ≦ Hn2 ≦ 1.0 [mm]. Thereby, the maximum depth Hn2 of the branch part 62 is optimized.

  Here, as shown in FIG. 4, a point Pn on the groove center line where the groove cross-sectional area of the circumferential narrow groove 6 is maximized and a point Ps at the end of the sipe 7 on the circumferential narrow groove 6 side are defined. .

  The groove cross-sectional area of the circumferential narrow groove is measured in a tire in an unloaded state in which the tire is mounted on the specified rim and filled with the specified internal pressure, or in a cross-sectional view with the circumferential direction as the normal direction. Further, in the configuration in which the circumferential narrow groove has a chamfered portion or a notch (including the branch portion 62 described above), the area of the region occupied by these is also included in the groove cross-sectional area of the circumferential narrow groove.

  The groove center line of the circumferential narrow groove is defined as a set of midpoints of left and right measurement points of the opening width Wn1 of the main portion 61.

  The sipe end point Ps is defined as the sipe end point on the tread of the block.

  At this time, the position in the tire circumferential direction of the point Pn of the circumferential narrow groove 6 is between the sipes adjacent to the tire circumferential direction and the points Ps and Ps of 7. That is, the groove cross-sectional area of the circumferential narrow groove 6 increases at the position of the branch portion 62 and takes a maximum value between the points Ps and Ps at the ends of the sipes 7 and 7 adjacent in the tire circumferential direction.

  In the above configuration, (1) since the groove cross-sectional area of the circumferential narrow groove 6 takes a maximum value between the points Ps, Ps at the ends of the adjacent sipes 7, 7, the circumferential direction of the adjacent sipes 7, 7 The ground contact pressure on the tread surface of the block 5 between the narrow groove 6 (the main portion 61 thereof) is effectively dispersed. Thereby, the entire ground pressure of the block 5 is effectively equalized, and the durability performance of the block 5 is improved.

  Further, (2) since the circumferential narrow groove 6 has a plurality of branch portions 62, the blocks 62 against the ice road surface are absorbed by the branch portion 62 by absorbing and removing the water film on the surface road surface when traveling on the ice road surface. The tread surface adhesion (so-called adhesion frictional force) is improved. Thereby, the performance on ice of a tire improves.

  Further, as shown in FIG. 4, in the configuration in which the circumferential narrow groove 6 and the sipe 7 are separated from each other, the tire width direction from the branch portion 62 of the circumferential narrow groove 6 to the point Ps at the end of the sipe 7. The distance D2 and the distance D1 in the tire width direction from the main portion 61 of the circumferential narrow groove 6 to the point Ps at the end of the sipe 7 preferably have a relationship of 0 ≦ D2 / D1 ≦ 0.80. It is more preferable to have a relationship of 0.50 ≦ D2 / D1 ≦ 0.70. Therefore, it is preferable that the branch portion 62 of the circumferential narrow groove 6 and the point Ps at the end of the sipe 7 do not wrap in the tire width direction. The distance D1 in the tire width direction between the main portion 61 of the circumferential narrow groove 6 and the point Ps of the sipe 7 is preferably in the range of 0.5 [mm] ≦ D1 ≦ 2.0 [mm]. Accordingly, the distance D2 in the tire width direction between the branch portion 62 of the circumferential narrow groove 6 and the sipe 7 is optimized.

  In FIG. 4, tires at a distance L2 in the tire circumferential direction from the tip of the branch 62 to the point Ps at the end of the sipe 7 and at points Ps and Ps at the ends of the sipes 7 and 7 adjacent in the tire circumferential direction. The distance L1 in the circumferential direction preferably has a relationship of 0.40 ≦ L2 / L1 ≦ 0.60. That is, it is preferable that the branch portion 62 of the circumferential narrow groove 6 is disposed at the center portion between the points Ps and Ps at the ends of the adjacent sipes 7 and 7. Thereby, the distance L2 of the tire circumferential direction of the branch part 62 of the circumferential direction narrow groove 6 and the edge part of the sipe 7 is optimized.

  The tip of the branch portion is defined as the maximum protruding position of the branch portion in the tire width direction from the main portion of the circumferential narrow groove.

  In FIG. 4, the opening width Wn2 (see FIG. 4) of the branch part 62 and the points Ps of the sipes 7 and 7 adjacent in the tire circumferential direction, and the distance L1 in the tire circumferential direction of Ps are 0.20 ≦ Wn2. /L1≦0.60 is preferable, and 0.30 ≦ Wn2 / L1 ≦ 0.40 is more preferable. Further, the opening width Wn2 of the branch part 62 is preferably in the range of 0.5 [mm] ≦ Wn2 ≦ 3.0 [mm], and 0.8 [mm] ≦ Wn2 ≦ 1.5 [mm]. More preferably, it is in the range. Thereby, the opening width Wn2 of the branch part 62 is optimized.

  The opening width Wn2 of the branch portion is measured as the maximum width of the branch portion in the tire circumferential direction in a no-load state in which the tire is mounted on the specified rim and filled with the specified internal pressure.

[Modification]
6-10 is explanatory drawing which shows the modification of the circumferential direction fine groove described in FIG. In these drawings, the same components as those described in FIG.

  In the configuration of FIG. 4, the branch portion 62 of the circumferential narrow groove 6 has a rectangular shape as a whole. However, the present invention is not limited to this, and the branch portion 62 may have an arc-shaped end portion (see FIG. 6) or a stepped shape with a narrowed end portion side (see FIG. 7). . Further, the branch part 62 may have a parallelogram shape (see FIG. 8) inclined in the tire circumferential direction, or a triangular shape (see FIG. 9 and FIG. 10) with a narrowed tip side. good.

  In the configuration of FIG. 6, the branch portion 62 of the circumferential narrow groove 6 has a chamfered portion (reference numeral omitted in the drawing) at the opening. Specifically, a chamfered portion shallower than the maximum depth Hn2 (see FIG. 5) of the branch portion 62 is formed over the entire circumference of the opening portion of the branch portion 62. Thereby, when traveling on a snowy road surface, snow clogging to the branch portion 62 is suppressed, and the snow performance of the tire is improved.

  Moreover, in the structure of FIG. 4, the branch parts 62 and 62 adjacent to the tire circumferential direction are spaced apart from each other. However, the present invention is not limited to this, and as shown in FIG. 10, branch portions 62 and 62 adjacent in the tire circumferential direction may be continuous with each other.

  FIG. 11 and FIG. 12 are explanatory views showing a modification of the circumferential narrow groove shown in FIG. In these drawings, the same components as those described in FIG. 5 are denoted by the same reference numerals, and the description thereof is omitted.

  In the configuration of FIG. 5, the branch part 62 of the circumferential narrow groove 6 is a notch part extending in the tire width direction from the main part 61, and has a bottom part extending with a predetermined step with respect to the tread surface of the block 5. doing. However, the present invention is not limited thereto, and the entire branch portion 62 may be a C chamfer (see FIG. 11) or an R chamfer (see FIG. 12) formed in the main portion 61.

  13-16 is explanatory drawing which shows the modification of the circumferential direction fine groove described in FIG. In these drawings, the same components as those described in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

  In the configuration of FIG. 3, the block 5 is a shoulder block and is on the tire ground contact edge T. However, the present invention is not limited to this, and the block 5 may be partitioned into the left and right circumferential main grooves 2 and 2 as shown in FIG.

  In the configuration of FIG. 3, the branch portion 62 of the circumferential narrow groove 6 has a constant width Wn2 (see FIG. 4). On the other hand, in the configuration of FIG. 14, the circumferential narrow groove 6 has a first branch portion 62a and a second branch portion 62b having an opening area larger than that of the first branch portion 62a. And the 2nd branch part 62b is arrange | positioned in the center part of the tire circumferential direction of the block 5 rather than the 1st branch part 62a. The center portion in the tire circumferential direction of the block 5 has a higher contact pressure than the edge portion in the tire circumferential direction. Therefore, the second branch portion 62b having a large opening area is disposed at the center portion of the block 5 in the tire circumferential direction, so that the ground contact pressure of the block 5 is dispersed and uniformed in the tire circumferential direction.

  In the configuration of FIG. 3, the circumferential narrow groove 6 has a plurality of branch portions 62 at the left and right edge portions in the tire width direction. Further, the left and right branch portions 62 of the circumferential narrow groove 6 are arranged at the same position in the tire circumferential direction. However, the present invention is not limited thereto. For example, as shown in FIG. 15, in the configuration in which the left and right sipe groups 7 of the circumferential narrow groove 6 are arranged offset in the tire circumferential direction, the left and right branches of the circumferential narrow groove 6 The part 62 may be arranged offset in the tire circumferential direction according to the position of the sipe 7.

  3, the circumferential narrow groove 6 penetrates the block 5 in the tire circumferential direction, and the sipe 7 terminates inside the block 5 without opening to the main groove 2 or the tire ground contact end T. Yes. However, the present invention is not limited to this, and as shown in FIG. 16, the circumferential narrow groove 6 may terminate inside the block 5 at one end, and a part or all of the sipes 7 may be the main groove. 2 or the tire ground contact end T may be opened.

[effect]
As described above, the pneumatic tire 1 includes the main groove 2 and the land portion 3 (particularly, the block 5 partitioned in the tire circumferential direction) defined in the main groove 2 (see FIG. 2). Further, the land portion 3 includes a circumferential narrow groove 6 extending in the tire circumferential direction, and a plurality of sipes 7 disposed in at least one region of the land portion 3 partitioned by the circumferential narrow groove 6 ( (See FIG. 3). Further, the groove cross-sectional area of the circumferential narrow groove 6 changes as it goes in the tire circumferential direction. Further, when defining the point Pn on the groove center line where the groove cross-sectional area of the circumferential narrow groove 6 is maximum and the point Ps at the end of the sipe 7 on the circumferential narrow groove 6 side, The position of the point Pn in the tire circumferential direction is between the points Ps and Ps of the sipe 7 adjacent in the tire circumferential direction (see FIG. 4).

  In such a configuration, since the groove cross-sectional area of the circumferential narrow groove 6 takes a maximum value between the points Ps, Ps at the ends of the adjacent sipes 7, 7, the adjacent sipes 7, 7 and the circumferential narrow groove 6 ( The ground contact pressure on the tread surface of the block 5 with the main portion 61) is effectively dispersed. Thereby, there is an advantage that the entire ground pressure of the block 5 is effectively equalized and the durability performance of the block 5 is improved. In particular, in the studless tire, the rubber hardness of the tread rubber 15 is low and the durability performance of the block 5 is relatively low because the block 5 has a large number of sipes as compared with a general summer tire. Therefore, by applying the above configuration to the studless tire, the effect of improving the durability performance can be remarkably obtained.

  In the pneumatic tire 1, the opening width Wn of the circumferential narrow groove 6 (defined as the entire opening width of the circumferential narrow groove 6 including the branch portion 62) is a maximum value at the position of the point Pn. (See FIG. 4). Thereby, there exists an advantage which can adjust the groove cross-sectional area of the circumferential direction fine groove 6 with opening width Wn.

  In the pneumatic tire 1, the circumferential narrow groove 6 extends in the tire width direction from the main portion 61 extending in the tire circumferential direction, and widens the opening width of the circumferential narrow groove 6. And a branch portion 62 (see FIG. 4). In such a configuration, the adhesion of the tread surface of the block 5 to the ice road surface (so-called adhesion frictional force) is improved by the branch portion 62 absorbing and removing the water film on the surface of the road surface when traveling on the ice road surface. Thereby, there exists an advantage which the performance on ice of a tire improves.

  In this pneumatic tire 1, the opening width Wn1 (see FIG. 4) of the main portion 61 is in the range of 0.5 [mm] ≦ Wn1 ≦ 3.0 [mm]. Thereby, there exists an advantage by which the groove opening width Wn1 of the main part 61 is optimized. That is, by the above lower limit, the effect of reducing the contact pressure of the block 5 by the circumferential narrow groove 6 is appropriately ensured. Moreover, the ground contact area of the block 5 is ensured appropriately by the upper limit.

  In the pneumatic tire 1, the maximum depth Hn1 (see FIG. 5) of the main portion 61 and the maximum groove depth H0 (not shown) of the main groove 2 are 0.05 ≦ Hn1 / H0 ≦ 0. There are 40 relationships. Thereby, there exists an advantage by which the maximum depth Hn1 of the main part 61 is optimized. That is, by the above lower limit, the effect of reducing the contact pressure of the block 5 by the circumferential narrow groove 6 is appropriately ensured. Moreover, the rigidity of the block 5 is ensured appropriately by the upper limit.

  Further, in the pneumatic tire 1, the maximum depth Hn2 (see FIG. 5) of the branch portion 62 and the maximum depth Hn1 of the main portion 61 have a relationship of 0.10 ≦ Hn2 / Hn1 ≦ 0.50. . Thereby, there exists an advantage by which the maximum depth Hn2 of the branch part 62 is optimized. That is, the water film removing action of the surface road surface by the branch part 62 is appropriately ensured by the above lower limit. Moreover, the rigidity of the block 5 is ensured appropriately by the upper limit.

  Further, in the pneumatic tire 1, the maximum depth Hn2 (see FIG. 5) of the branch portion 62 is in a range of 0.1 [mm] ≦ Hn2 ≦ 1.0 [mm]. Thereby, there exists an advantage by which the maximum depth Hn2 of the branch part 62 is optimized. That is, the water film removing action of the surface road surface by the branch part 62 is appropriately ensured by the above lower limit. Moreover, the rigidity of the block 5 is ensured appropriately by the upper limit.

  In the pneumatic tire 1, the distance W1 from the measurement point of the ground contact width Wb of the land portion 3 to the groove center line of the main portion 61 and the ground contact width Wb of the land portion 3 are 0.40 ≦ W1 / Wb. ≦ 0.60 (see FIG. 3). Thereby, the circumferential direction narrow groove 6 is arrange | positioned in the center part of the tire width direction of the land part 3, and there exists an advantage by which the contact area of the land part 3 in the right and left of the circumferential direction narrow groove 6 is equalized.

  In the pneumatic tire 1, the main portion 61 and the branch portion 62 of the circumferential narrow groove 6 and the sipe 7 are separated from each other (see FIG. 3). Such a configuration has an advantage that the rigidity of the block is ensured and the durability of the block is ensured, compared to a configuration (not shown) in which the sipe 7 communicates with the circumferential narrow groove 6.

  Further, in this pneumatic tire 1, a distance D2 in the tire width direction from the tip of the branch portion 62 to the point Ps of the sipe 7 and a distance D1 in the tire width direction from the main portion 61 to the point Ps of the sipe 7 are It has a relationship of 0 ≦ D2 / D1 ≦ 0.80 (see FIG. 4). Thereby, there exists an advantage by which the distance D2 from the branch part 62 to the sipe 7 is optimized. That is, the rigidity of the block is appropriately ensured by the lower limit and the lower limit.

  In the pneumatic tire 1, the distance D1 (see FIG. 4) in the tire width direction from the main portion 61 to the point Ps of the sipe 7 is in the range of 0.5 [mm] ≦ D1 ≦ 2.0 [mm]. It is in. Thereby, there exists an advantage by which the distance D1 from the main part 61 to the sipe 7 is optimized. That is, the lower limit ensures adequate block rigidity. Moreover, the extension length of the sipe 7 is ensured by the said upper limit.

  Further, in the pneumatic tire 1, the distance L2 in the tire circumferential direction from the tip of the branch portion 62 to the point Ps of the sipe 7 and the points Ps and Ps of the sipes 7 and 7 adjacent in the tire circumferential direction in the tire circumferential direction. The distance L1 has a relationship of 0.40 ≦ L2 / L1 ≦ 0.60 (see FIG. 4). Thereby, the front-end | tip of the branch part 62 is arrange | positioned in the center part of the edge part of the sipes 7 and 7 which adjoin, and there exists an advantage by which the rigidity of the tire circumferential direction of the land part 3 is optimized.

  Further, in this pneumatic tire 1, the opening width Wn2 of the branch portion 62 and the point Ps of the sipe 7 adjacent in the tire circumferential direction and the distance L1 in the tire circumferential direction of Ps are 0.20 ≦ Wn2 / L1 ≦ 0. .60 (see FIG. 4). Thereby, there exists an advantage by which the opening width Wn2 of the branch part 62 is optimized. That is, the opening width Wn2 of the branch part 62 is secured by the lower limit, and the function of the branch part 62 is secured. Further, the above upper limit suppresses a decrease in rigidity of the block 5 due to the problem of the opening width Wn2 of the branch portion 62.

  Moreover, in this pneumatic tire 1, the branch part 62 has a chamfering part (a code | symbol abbreviation | omission in a figure) in an opening part (refer FIG. 6). Accordingly, there is an advantage that the snow performance of the tire is improved by suppressing snow clogging to the branch portion 62 when traveling on a snowy road surface.

  Moreover, in this pneumatic tire 1, the branch part 62 has an opening part of a step shape (refer FIG. 7). With such a configuration, there is an advantage that the rigidity of the block can be secured by the narrow portion having the stepped shape while securing the edge component of the branch portion 62.

  Moreover, in this pneumatic tire 1, the branch part 62 has a rectangular or triangular opening (refer FIG. 4, FIG. 8-FIG. 10). Thereby, the edge effect | action of the branch part 62 improves and there exists an advantage which the snow performance of a tire improves.

  Moreover, in this pneumatic tire 1, the land portion 3 is the block 5, and the circumferential narrow groove 6 is a first branch portion 62a and a second opening area having a larger opening area than the first branch portion 62a. The second branch portion 62b is arranged at the center portion of the block 5 in the tire circumferential direction with respect to the first branch portion 62a (see FIG. 14). In such a configuration, the second branch portion 62b having a large opening area is arranged in the center portion of the block 5 in the tire circumferential direction, whereby the ground contact pressure of the block 5 is distributed and uniformed in the tire circumferential direction. There is.

  FIG. 17 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, (1) on-ice braking performance and (2) durability performance were evaluated for a plurality of types of test tires. A test tire having a tire size of 195 / 65R15 91Q is assembled to a rim having a rim size of 15 × 6J.

  (1) In the evaluation on braking performance on ice, the test tire is mounted on an SUV (Sport Utility Vehicl) with a displacement of 1.5 [L], which is a test vehicle, and a front engine front drive (FF) system. An internal pressure of kPa] and a specified load of JATMA are applied. Further, the test vehicle travels on a predetermined ice road surface, and the braking distance from the traveling speed of 40 [km / h] is measured. Based on this measurement result, index evaluation is performed with the conventional example 1 as a reference (100). This evaluation is preferable as the numerical value increases.

  (2) In the evaluation on durability performance, an indoor drum tester (drum diameter: 1707 mm) is used, and the ambient temperature is set to 38 ± 3 [° C.]. Further, an internal pressure of 180 [kPa] and a load load corresponding to 88% of the maximum load specified by JATMA are applied to the test tire. Further, the vehicle is allowed to travel for 2 hours at a speed of 81 [km / h], and then the load time is increased by 13 [%] every 2 hours, and the travel time when the test tire breaks is measured. Based on this measurement result, index evaluation is performed with the conventional example 1 as a reference (100). This evaluation is preferable as the numerical value increases.

  The test tires of Examples 1 to 13 have the configurations shown in FIGS. The tread width TW is TW = 150 [mm], the width Wb of the block 5 is Wb = 25 [mm], and the ratio W1 / Wb = 0.50. The distance L1 between the ends of the adjacent sipes 7, 7 is L1 = 3.5 [mm]. The depth H0 of the main groove 2 is H0 = 9.0 [mm], and the depth Hs of the sipe 7 is Hs = 6.5 [mm].

  In the test tires of Conventional Examples 1 and 2, in the configuration of FIGS. 1 to 5, the circumferential narrow groove 6 includes only the main portion 61 and does not have the branch portion 62.

  As shown in the test results, it can be seen that in the test tires of Examples 1 to 13, both the braking performance on ice and the durability performance of the tire are compatible.

  1: pneumatic tire, 11: bead core, 12: bead filler, 13: carcass layer, 14: belt layer, 141, 142: cross belt, 143: belt cover, 15: tread rubber, 16: sidewall rubber, 17: Rim cushion rubber, 2: circumferential main groove, 3: land portion, 4: lug groove, 5: block, 6: circumferential narrow groove, 61: main portion, 62, 62a, 62b: branch portion, 7: sipe

Claims (17)

A pneumatic tire comprising a main groove and a land portion partitioned into the main groove,
The land portion includes a circumferential narrow groove extending in a tire circumferential direction, and a plurality of sipes disposed in at least one region of the land portion partitioned by the circumferential narrow groove,
The groove cross-sectional area of the circumferential narrow groove changes as it goes in the tire circumferential direction,
Defining a point Pn on the groove center line where the groove cross-sectional area of the circumferential narrow groove is maximized, and a point Ps of the end of the sipe on the circumferential narrow groove side
The pneumatic tire is characterized in that the position of the circumferential narrow groove point Pn in the tire circumferential direction is between the sipe points Ps and Ps adjacent to each other in the tire circumferential direction.   The pneumatic tire according to claim 1, wherein the opening width of the circumferential narrow groove takes a maximum value at the position of the point Pn.   The said circumferential narrow groove has a main part extended in a tire circumferential direction, and a branch part which branches in the tire width direction from the said main part, and widens the opening width of the said circumferential narrow groove. Pneumatic tire described in 2.   The pneumatic tire according to claim 3, wherein an opening width Wn1 of the main part is in a range of 0.5 [mm] ≤ Wn1 ≤ 3.0 [mm].   The pneumatic tire according to claim 3 or 4, wherein the maximum depth Hn1 of the main portion and the maximum groove depth H0 of the main groove have a relationship of 0.05≤Hn1 / H0≤0.40.   The air according to any one of claims 3 to 5, wherein the maximum depth Hn2 of the branch portion and the maximum depth Hn1 of the main portion have a relationship of 0.10 ≦ Hn2 / Hn1 ≦ 0.50. Enter tire.   The pneumatic tire according to any one of claims 3 to 6, wherein a maximum depth Hn2 of the branch portion is in a range of 0.1 [mm] ≤ Hn2 ≤ 1.0 [mm].   The distance W1 from the measurement point of the contact width of the land portion to the groove center line of the main portion and the contact width Wb of the land portion have a relationship of 0.40 ≦ W1 / Wb ≦ 0.60. The pneumatic tire according to any one of 3 to 7.   The pneumatic tire according to any one of claims 3 to 8, wherein the main portion and the branch portion of the circumferential narrow groove and the sipe are separated from each other.   The distance D2 in the tire width direction from the tip of the branch portion to the sipe point Ps and the distance D1 in the tire width direction from the main portion to the sipe point Ps are 0 ≦ D2 / D1 ≦ 0.80. The pneumatic tire according to claim 9, having the relationship:   The pneumatic tire according to claim 9 or 10, wherein a distance D1 in a tire width direction from the main part to the sipe point Ps is in a range of 0.5 [mm] ≤ D1 ≤ 2.0 [mm].   The distance L2 in the tire circumferential direction from the tip of the branch portion to the sipe point Ps and the distance L1 in the tire circumferential direction of the sipe points Ps and Ps adjacent to each other in the tire circumferential direction are 0.40 ≦ L2 / The pneumatic tire according to any one of claims 3 to 11, which has a relationship of L1? 0.60.   The opening width Wn2 of the branch portion and the distance L1 in the tire circumferential direction between the sipe points Ps and Ps adjacent in the tire circumferential direction have a relationship of 0.20 ≦ Wn2 / L1 ≦ 0.60. The pneumatic tire as described in any one of -12.   The pneumatic tire according to any one of claims 3 to 13, wherein the branch portion has a chamfered portion at an opening.   The pneumatic tire according to claim 3, wherein the branch portion has a stepped opening.   The pneumatic tire according to any one of claims 3 to 15, wherein the branch portion has a rectangular or triangular opening. The land portion is a block,
The circumferential narrow groove has the first branch and a second branch having an opening area larger than the first branch; and
The pneumatic tire according to any one of claims 3 to 16, wherein the second branch portion is disposed at a central portion in the tire circumferential direction of the block rather than the first branch portion.

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