JP5915505B2 - Pneumatic tire - Google Patents

Description

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

  In a small truck studless tire, there is a problem to improve the performance on the ice and the performance on the snow, and a traction pattern including a plurality of block rows having sipes is employed. As conventional pneumatic tires related to such problems, techniques described in Patent Documents 1 and 2 are known.

JP 2009-214775 A JP 2009-96220 A

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

In order to achieve the above object, a pneumatic tire according to the present invention includes at least four circumferential main grooves extending in the tire circumferential direction and a plurality of land portions defined by the circumferential main grooves. In the pneumatic tire, the left and right circumferential main grooves on the outermost side in the tire width direction are called outermost circumferential main grooves, the land portion closest to the tire equatorial plane is called a center land portion, and the outermost When the land portion on the outer side in the tire width direction defined by the outer circumferential main groove is referred to as a shoulder land portion, the edge on the outer side in the tire width direction of the center land portion extends continuously from the tread end in the tire width direction. A plurality of first lug grooves that open in the circumferential main groove that divides a portion, and the center land portion that penetrates in the tire width direction and that are arranged in a staggered manner in the tire circumferential direction with respect to the first lug groove A plurality of second lug grooves, Yoruda land portion or said is disposed on the land portion adjacent to the shoulder land portion and a circumferential narrow groove extending in the tire circumferential direction, and, on the intersection of the said center land portion first lug grooves The edge portion of the center land portion has a step portion offset in the tire width direction .

  In the pneumatic tire according to the present invention, since the first lug groove continuously extends from the tread end to the circumferential main groove defining the center land portion, the drainage in the tire width direction and the snow drainage on the sherbet road surface Improves. Thereby, there exists an advantage which the performance on ice and the performance on snow of a tire improve.

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 a tread surface of the pneumatic tire shown in FIG. 2. FIG. 4 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 5 is an explanatory view showing a conventional pneumatic tire.

  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. This figure shows one side region in the tire radial direction. The figure shows a small truck studless tire as an example of a pneumatic tire. In the figure, the symbol CL is the tire equator plane. The tire width direction means a direction parallel to a tire rotation axis (not shown), 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 periphery in the tire radial direction of the pair of bead cores 11 and 11 to reinforce the bead portion.

  The carcass layer 13 is bridged in a toroidal shape between the left and right bead cores 11 and 11 to form a tire skeleton. 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 layer 13 is formed by rolling 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 has an absolute value of 80 [deg]. A carcass angle of 95 [deg] or less (inclination angle in the fiber direction of the carcass cord with respect to the tire circumferential direction).

  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 40 [deg] or less. Have. Further, the pair of cross belts 141 and 142 have belt angles with different signs from each other (inclination angle of the fiber direction of the belt cord with respect to the tire circumferential direction), and are laminated so that the fiber directions of the belt cords cross each other. (Cross ply structure). The belt cover 143 is formed by rolling a plurality of belt cords made of steel or organic fiber material coated with a coat rubber, and has a belt angle of 45 [deg] or more and 70 [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 and 17 are arranged on the outer sides in the tire width direction of the left and right bead cores 11 and 11 and the bead fillers 12 and 12, respectively, and constitute left and right bead portions.

  The tread rubber 15 preferably has a rubber hardness of 60 or more and 75 or less, and more preferably 65 or more and 70 or less. Rubber hardness means JIS-A hardness based on JIS-K6263, and is measured under the condition of 20 [° C.].

[Tread pattern]
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 a tread surface of the pneumatic tire shown in FIG. 2. In these drawings, FIG. 2 shows a traction pattern of a studless tire. FIG. 3 shows a one-sided region with the tire equatorial plane CL as a boundary. In these drawings, the tire circumferential direction refers to the direction around the tire rotation axis. Moreover, the code | symbol T is a tire grounding end.

  The pneumatic tire 1 includes at least four circumferential main grooves 21 and 22 extending in the tire circumferential direction, and a plurality of land portions 31 to 33 that are partitioned by the circumferential main grooves 21 and 22. Provided in the tread portion (see FIG. 2).

  The circumferential main groove refers to a circumferential groove having a groove width of 1.0 [mm] or more. The groove width of the circumferential groove is measured excluding notches and chamfers formed in the groove opening of the tread surface.

  In this embodiment, the left and right circumferential main grooves 22 and 22 on the outermost side in the tire width direction are referred to as outermost circumferential main grooves. The land portion 31 closest to the tire equatorial plane CL is called a center land portion. At this time, when there is a land portion on the tire equatorial plane CL (see FIG. 2), this land portion becomes the center land portion, and when there is a circumferential main groove on the tire equatorial plane CL (not shown). The left and right land portions sandwiching the circumferential main groove are the center land portions. Further, the land portions 33, 33 on the outer side in the tire width direction divided into the left and right outermost circumferential main grooves 22, 22 are referred to as shoulder land portions. The land portion 32 between the center land portion 31 and the shoulder land portion 33 is referred to as a second land portion.

  For example, in the configuration of FIG. 2, the four circumferential main grooves 21 and 22 are arranged symmetrically about the tire equatorial plane CL. The circumferential main grooves 21, 22 divide a row of center land portions 31 on the tire equatorial plane CL, and a pair of left and right second land portions 32, 32 and a pair of left and right shoulder land portions 33. , 33 are partitioned.

  The pneumatic tire 1 includes a plurality of first lug grooves 41 and a plurality of second lug grooves 42 (see FIG. 2).

  The first lug groove 41 is a main groove that extends in the tire width direction from the tread end and terminates in the center land portion 31. That is, the first lug groove 41 extends in the tire width direction from the tread end, penetrates the shoulder land portion 33 and the second land portion 32, and continuously extends to the center land portion 31. Terminate internally. For this reason, the first lug groove 41 intersects all the circumferential main grooves 21 and 22 between the center land portion 31 and the shoulder land portion 33.

  Here, the first lug groove 41 continuously extending means that the first lug groove with respect to the circumferential main groove 21 (22) at the intersection of the first lug groove 41 and the circumferential main groove 21 (22). It means that the left and right openings of 41 face each other without being offset in the tire circumferential direction. In such a configuration, the first lug groove 41 communicates in the tire width direction as an apparent single main groove from the tread end to the terminal end of the center land portion 31. This improves drainage in the tire width direction and snow drainage on the sherbet road surface.

  The tread end portion refers to both end portions of a tread pattern portion of the tire when the tire is mounted on a specified rim to apply a specified internal pressure and to be in an unloaded state.

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

  The second lug groove 42 is a main groove that penetrates the center land portion 31 in the tire width direction. The second lug groove 42 extends in the tire width direction without intersecting the first lug groove 41 inside the center land portion 31 and opens to the left and right circumferential main grooves 21, 21.

  The lug groove refers to a lateral groove having a groove width of 2.0 [mm] or more. The groove width of the lug groove is measured excluding notches and chamfers formed in the groove opening of the tread surface.

  For example, in the configuration of FIG. 2, the plurality of first lug grooves 41 are arranged at predetermined intervals in the tire circumferential direction, and are arranged in the left and right regions with the tire equatorial plane CL as a boundary. Further, these first lug grooves 41 extend continuously from the tread end in the tire width direction and terminate in the center land portion 31 without intersecting the tire equatorial plane CL. For this reason, the 1st lug grooves 41 and 41 of a right-and-left area | region are arrange | positioned without mutually crossing. In addition, when these first lug grooves 41 terminate in the center land portion 31, notches by the first lug grooves 41 are formed in the left and right edge portions of the center land portion 31. Further, by these first lug grooves 41, the left and right shoulder land portions 33, 33 and the second land portions 32, 32 are divided in the tire circumferential direction to form a block row.

  As shown in FIG. 3, the first lug groove 41 is inclined in one direction of the tire circumferential direction from the tread end toward the tire equatorial plane CL. Specifically, the first lug groove 41 has an arc shape as a whole, is curved in one direction without being meandering, and extends in the tire width direction. Further, the first lug groove 41 in one region and the first lug groove 41 in the other region with respect to the tire equatorial plane CL are inclined in mutually different directions with respect to the tire circumferential direction. Specifically, the first lug groove 41 in the left region of FIG. 3 is inclined upward in the drawing as it goes toward the tire equatorial plane CL, and the first lug groove 41 in the right region of FIG. As it goes to the surface CL, the surface is inclined downward.

  In addition, the inclination angle β of the first lug groove 41 with respect to the tire width direction increases from the tread end toward the tire equatorial plane CL. The maximum value βmax of the inclination angle β is preferably in the range of 1 [deg] ≦ βmax ≦ 30 [deg], and more preferably in the range of 5 [deg] ≦ βmax ≦ 30 [deg]. preferable. This inclination angle β is measured as an angle formed by the groove center line of the first lug groove 41 and the tire width direction. Further, the first lug groove 41 widens the groove width toward the outer side in the tire width direction. As a result, the snow drainage of the first lug groove 41 is enhanced.

  Further, in the configuration of FIG. 2, the plurality of second lug grooves 42 are arranged at a predetermined interval in the tire circumferential direction, and penetrate only the center land portion 31 and the left and right circumferential main grooves 21, 21. It is terminated. Moreover, the center land portion 31 is divided in the tire circumferential direction by these second lug grooves 42 to form a block row. A pair of left and right first lug grooves 41, 41 extend from the left and right regions of the tire and terminate between the second lug grooves 42, 42 adjacent in the tire circumferential direction. For this reason, in the center land portion 31, the left and right first lug grooves 41, 41 and the second lug grooves 42 are arranged in a staggered manner in the tire circumferential direction. Moreover, each block of the center land part 31 has the notch part by the left-and-right 1st lug grooves 41 and 41 in the circumferential direction main grooves 21 and 21 side edge part, respectively.

  The pneumatic tire 1 also includes a pair of left and right circumferential narrow grooves 23 and 23 (see FIG. 2).

  The circumferential narrow groove 23 is a narrow groove disposed in the shoulder land portion 33 and extending in the tire circumferential direction. The circumferential narrow groove 23 extends inside the shoulder land portion 33 in the tire circumferential direction without opening to the outermost circumferential main groove 22 and the tread end, and divides the shoulder land portion 33 into two in the tire width direction. .

  The circumferential narrow groove 23 has a bent shape and extends while meandering in the tire circumferential direction. This bent shape includes both a refractive shape (for example, zigzag shape) and a curved shape (for example, sinusoidal shape). At this time, the configuration in which the circumferential narrow groove 23 has a refractive shape is preferable in that the edge component of the shoulder land portion 33 is increased and the traction of the tire is improved.

  The circumferential narrow groove refers to a circumferential groove having a groove width of 1.0 [mm] or more and less than the groove width of the circumferential main groove. The groove width of the narrow groove is measured as a distance between opposing groove wall surfaces. Therefore, for a groove having an amplitude such as a wavy shape or a zigzag shape, the groove width is measured regardless of the amplitude to determine whether the groove is a circumferential narrow groove.

  For example, in the configuration of FIG. 2, the left and right shoulder land portions 33, 33 each have one circumferential narrow groove 23. Further, as shown in FIG. 3, the circumferential narrow groove 23 has a zigzag shape having an amplitude in the tire width direction, and has at least one bent portion in each block of the shoulder land portion 33. . At this time, the number of bent portions of the circumferential narrow groove 23 in one block may be one or two in order to reduce snow clogging in the circumferential narrow groove 23 and improve the escape of the snow column. preferable. The maximum value αmax of the bending angle α of the circumferential narrow groove 23 is preferably in the range of 1 [deg] ≦ αmax ≦ 30 [deg], and the range of 5 [deg] ≦ αmax ≦ 25 [deg]. More preferably, it is within.

  The bending angle α is measured with reference to the groove center line of the circumferential narrow groove 23. Further, in the configuration in which the circumferential narrow groove 23 has a wave shape, it is measured as an angle formed by an imaginary line connecting adjacent inflection points.

  In the configuration of FIG. 2, the maximum groove depth Hs of the circumferential narrow groove 23 and the maximum groove depth H of the outermost circumferential main groove 22 have a relationship of 0.40 ≦ Hs / H ≦ 0.80. Preferably, it has a relationship of 0.50 ≦ Hs / H ≦ 0.80. The groove depth is measured excluding the notch of the groove opening and the upper bottom of the groove bottom.

  Further, the distance Ls from the tire equatorial plane CL to the circumferential narrow groove 23 and the distance L from the tire equatorial plane CL to the tire ground contact edge T have a relationship of 0.70 ≦ Ls / L ≦ 0.90. Is preferred.

  The tire ground contact end T is a tire and a flat plate when the tire is mounted on a specified rim and applied with a 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. The maximum width position in the tire axial direction on the contact surface.

  In the pneumatic tire 1, as described above, the center land portion 31, the second land portion 32, and the shoulder land portion 33 include the circumferential main grooves 21, 22, the first lug groove 41, and the second lug groove 42. It is divided into a block row. These block rows are configured to be point-symmetric about a point on the tire equatorial plane CL in a tread plan view. Such a point-symmetric pattern is preferable because convenience during tire rotation is improved.

  Further, in the configuration of FIG. 3, the edge portion of the center land portion 31 has a step portion that is offset in the tire width direction at the intersection position with the first lug groove 41. That is, the edge portion on the circumferential main groove 21 side of the center land portion 31 is divided into two in the tire circumferential direction by the first lug groove 41, and one edge portion and the other edge portion are displaced in the tire width direction. Are arranged. The step W1 of the edge portion is preferably in the range of 1 [mm] ≦ W1 ≦ 4 [mm].

  Further, at the intersection of the circumferential main groove 21 on the outer side in the tire width direction of the center land portion 31 and the second lug groove 42, the land portion on the outer side in the tire width direction of the center land portion 31 (in FIG. The edge portion of the land portion 32) on the center land portion 31 side is flush (step W2 = 0 [mm]) and has no step. Therefore, the circumferential main groove 21 between the center land portion 31 and the second land portion 32 has a step shape at the groove opening portion on the center land portion 31 side, and is formed on the groove opening portion on the second land portion 32 side. And has a straight shape.

  Also, at the intersection of the outermost circumferential main groove 22 and the first lug groove 41, the left and right land portions 32, 33 facing each other with the outermost circumferential main groove 22 interposed therebetween are edge portions offset in the tire width direction. Have. Specifically, in the second land portion 32 and the shoulder land portion 33, the edge portions of the blocks adjacent in the tire circumferential direction are arranged at different positions in the tire width direction at the opening of the first lug groove 41. . Moreover, the edge part by the side of the outermost peripheral direction main groove 22 of each block has a level | step-difference part which changes to a tire width direction at step shape, respectively. Moreover, the edge part of the block which opposes on both sides of the outermost periphery direction main groove 22 has the step part which changes mutually in the same direction, and the groove width of the outermost periphery direction main groove 22 is maintained substantially constant. . As a result, the outermost circumferential main groove 22 extends in substantially the same groove width in the tire circumferential direction while being bent stepwise in the tire width direction.

  Moreover, in this pneumatic tire 1, as shown in FIG.2 and FIG.3, the block of each land part 31-33 has the some sipe 5, respectively. Thereby, the edge component of a block is reinforced and the traction performance as a studless tire is improved.

  Sipe refers to a cut having a sipe width of less than 1.0 [mm]. The sipe may be a plane sipe having a straight sipe wall surface in a cross-sectional view perpendicular to the sipe length direction, or bent in a sipe width direction in a cross-sectional view perpendicular to the sipe length direction. A three-dimensional sipe having a shaped sipe wall surface may be used. The three-dimensional sipe has an action of reinforcing the rigidity of the land portion because the meshing force of the opposing sipe wall surfaces is stronger than that of the two-dimensional sipe.

[Modification]
In the configuration of FIG. 2, the first lug groove 41 extends to the center land portion 31 and terminates inside the center land portion 31. In such a configuration, the notch by the first lug groove 41 is formed at the edge portion of the center land portion 31. Then, the edge component of the center land part 31 increases and it is preferable at the point which the traction property of a tire improves.

  However, the present invention is not limited to this, and the first lug groove 41 may open to the circumferential main groove 21 that defines the outer edge portion of the center land portion 31 in the tire width direction and terminate at this position (not shown). . That is, the first lug groove 41 may not extend to the center land portion 31. At this time, it is necessary that the opening of the first lug groove 41 and the opening of the second lug groove 42 in the circumferential main groove 21 are at different positions in the tire circumferential direction.

  Further, in the configuration of FIG. 2, the circumferential narrow groove 23 is disposed only in the shoulder land portion 33. Such a configuration is preferable in that the edge component of the shoulder land portion 33 is improved and the turning performance of the tire is improved. Further, compared with the configuration in which the circumferential main groove 21 is disposed in the center land portion 31 or the second land portion 32, the rigidity of the tread portion center region is ensured, so that the stop and go performance of the tire is improved. Moreover, it is preferable at the point by which generation | occurrence | production of centerware is suppressed.

  However, the present invention is not limited thereto, and the circumferential narrow groove 23 may be disposed in a land portion (second land portion 32) adjacent to the shoulder land portion 33 (not shown). However, as described above, the distance Ls from the tire equatorial plane CL to the circumferential narrow groove 23 and the distance L from the tire equatorial plane CL to the tire ground contact edge T are 0.70 ≦ Ls / L ≦ 0.90. (See FIG. 2).

  In the configuration of FIG. 3, the circumferential narrow groove 23 has a zigzag shape having a linear component. Further, the circumferential narrow groove 23 has at least one bent portion inside the block. In such a configuration, when the circumferential narrow groove 23 is closed when the tire is in contact with the tire, the opposing groove walls of the circumferential narrow groove 23 are engaged to ensure the rigidity of the block. Thereby, it is preferable at the point by which the traction property of a tire is ensured.

  However, the present invention is not limited to this, and the circumferential narrow groove 23 may have a wavy shape or may not have a bent portion inside the block (not shown).

  In the configuration of FIG. 3, in the blocks adjacent to the tire circumferential direction of the shoulder land portion 33, the opening of the circumferential narrow groove 23 in one block and the opening of the circumferential narrow groove 23 in the other block are The circumferential narrow groove 23 and the first lug groove 41 are disposed at the same position in the tire width direction (opposite to each other) at the intersection position. Therefore, one circumferential narrow groove 23 is continuously arranged in the tire circumferential direction. Such a configuration is preferable in that the occurrence of uneven wear in each block can be suppressed.

  However, the present invention is not limited to this, and adjacent openings of the circumferential narrow groove 23 may be arranged offset (shifted in the groove length direction of the first lug groove 41) (not shown).

[effect]
As described above, the pneumatic tire 1 includes at least four circumferential main grooves 21 and 22 extending in the tire circumferential direction, and a plurality of land divided by the circumferential main grooves 21 and 22. Part 31-33 (refer FIG. 2). The pneumatic tire 1 has a plurality of first lugs that continuously extend in the tire width direction from the tread end and open to the circumferential main grooves 21 that define the outer edge portions of the center land portion 31 in the tire width direction. The groove 41, the plurality of second lug grooves 42 penetrating the center land portion 31 in the tire width direction and arranged in a staggered manner in the tire circumferential direction with respect to the first lug groove 41, and the shoulder land portion 33 are disposed. And a circumferential narrow groove 23 extending in the tire circumferential direction.

  In this configuration, (1) since the first lug groove 41 continuously extends from the tread end to the circumferential main groove 21 that defines the center land portion 31, drainage in the tire width direction and drainage on the sherbet road surface are performed. Snowiness improves. Thereby, there exists an advantage which the performance on ice and the performance on snow of a tire improve.

  Further, (2) the first lug groove 41 and the second lug groove 42 are arranged in a staggered manner in the tire circumferential direction (see FIG. 3), whereby the opening of the first lug groove 41 with respect to the circumferential main groove 21. And the opening of the second lug groove 42 are arranged so as to be displaced from each other in the tire circumferential direction. In such a configuration, the traction component in the tread portion center region is increased as compared with a configuration (not shown) in which the second lug groove is disposed on the extended line of the first lug groove. Thereby, there exists an advantage which the performance on ice and the performance on snow of a tire improve. Further, there is an advantage that the uneven wear resistance performance of the tire is maintained by distributing the ground pressure.

  Further, (3) the circumferential narrow groove 23 is disposed in the shoulder land portion 33 that receives a large contact pressure when the vehicle is turning, so that the traction component in the tire width direction is increased, and the turning performance of the tire is improved. There is an advantage to improve. Further, compared with a configuration in which sipes are arranged in place of the circumferential narrow grooves 23 (not shown), the shear force in snow increases due to an increase in the groove volume of the shoulder land portion 33, and the on-ice performance of the tire and on the snow are increased. There is an advantage that the performance is improved.

  In the pneumatic tire 1, the first lug groove 41 extends continuously to the center land portion 31 without intersecting the second lug groove 42 and ends inside the center land portion 31 (FIG. 2). And FIG. 3). In such a configuration, the notch by the first lug groove 41 is formed at the edge portion of the center land portion 31, and the edge component of the center land portion 31 increases. Thereby, there exists an advantage which the traction property of a tire improves and the performance on ice and performance on snow of a tire improve.

  In the pneumatic tire 1, the shoulder land portion 33 has a block that is partitioned into a pair of first lug grooves 41 and 41 adjacent to each other in the tire circumferential direction and an outermost circumferential main groove 22. The circumferential narrow groove 23 has at least one bent portion inside the block (see FIG. 3). Thereby, the edge component of the shoulder land part 33 increases, and there exists an advantage which the performance on ice and the performance on snow of a tire improve. Further, since the circumferential narrow groove 23 has a bent portion inside the block, compared to a configuration in which the circumferential narrow groove has a straight shape (not shown), the collapse of the block is suppressed, and the anti-bias resistance of the tire is reduced. There is an advantage that wear resistance is improved.

  Moreover, in this pneumatic tire 1, the maximum value αmax of the bending angle α of the bent portion of the circumferential narrow groove 23 is in the range of 1 [deg] ≦ αmax ≦ 30 [deg] (see FIG. 3). Thereby, there exists an advantage by which the bending angle (alpha) of the circumferential direction fine groove 23 is optimized. That is, when 1 [deg] ≦ αmax, an effect of increasing the edge component due to the bent portion is obtained, and when αmax ≦ 30 [deg], the snow drainage property in the circumferential narrow groove 23 is ensured. The

  In the pneumatic tire 1, the relationship between the maximum groove depth Hs of the circumferential narrow groove 23 and the maximum groove depth H of the outermost circumferential main groove 22 is 0.40 ≦ Hs / H ≦ 0.80. Have Thereby, there exists an advantage by which the groove depth Hs of the circumferential direction fine groove 23 is optimized. That is, when 0.40 ≦ Hs / H, the shearing force in the snow due to the circumferential narrow groove 23 is ensured, and when Hs / H ≦ 0.80, the circumferential narrow groove 23 at the end of tire wear. The action is ensured properly.

  In this pneumatic tire 1, the distance Ls from the tire equatorial plane CL to the circumferential narrow groove 23 and the distance L from the tire equatorial plane CL to the tire ground contact edge T are 0.70 ≦ Ls / L ≦ 0. .90 (see FIG. 2). Thereby, there exists an advantage by which the position of the tire width direction of the circumferential direction narrow groove 23 is optimized. For example, by setting the arrangement of the circumferential narrow grooves 23 as described above, the circumferential narrow grooves 23 can be disposed in the ground contact surface even when the tire ground contact width is small when the vehicle is empty. Thereby, there is an advantage that the function of the circumferential narrow groove 23 can be appropriately ensured regardless of the loading condition of the vehicle.

  Moreover, in this pneumatic tire 1, the edge part of the center land part 31 has the level | step-difference part offset in the tire width direction in the crossing position of the center land part 31 and the 1st lug groove 41 (refer FIG. 3). . Thereby, the traction component of the center land part 31 increases, and there exists an advantage which the on-ice performance and on-snow performance of a tire improve.

  In the pneumatic tire 1, the land on the outer side in the tire width direction of the center land portion 31 at the intersection of the circumferential main groove 21 and the second lug groove 42 on the outer side in the tire width direction of the center land portion 31. The edge portion on the center land portion 31 side of the portion (second land portion 32 in FIG. 2) is flush (step W2 = 0 [mm]) (see FIG. 3). In such a configuration, there is an advantage that in the tread portion center region, the snow drainage can be secured by the edge portion of the second land portion 32 that is flush with the step portion of the center land portion 31 as described above.

  Moreover, in this pneumatic tire 1, the level | step difference W1 of the above-mentioned level | step-difference part exists in the range of 1 [mm] <= W1 <= 4 [mm] (refer FIG. 3). Thereby, there exists an advantage by which the level | step difference W1 of a level | step-difference part is optimized. That is, when 1 [mm] ≦ W1, a traction effect by the stepped portion is obtained, and when W1 ≦ 4 [mm], snow drainage at the stepped portion is ensured.

  Further, in the pneumatic tire 1, the maximum value βmax of the inclination angle β of the first lug groove 41 with respect to the tire width direction is within a range of 1 [deg] ≦ βmax ≦ 30 [deg] (see FIG. 3). Thereby, there exists an advantage by which the inclination | tilt angle (beta) of the 1st lug groove 41 is optimized. That is, when 1 [deg] ≦ βmax, the drainage performance of the first lug groove 41 in the tire width direction and the snow drainage performance on the sherbet road surface are improved. Further, by satisfying βmax ≦ 30 [deg], an edge component in the tire circumferential direction is ensured, the traction performance of the tire is ensured, and the uneven wear resistance under the stop-and-go use condition is ensured. The

  In the pneumatic tire 1, the first lug groove 41 is inclined in one direction in the tire circumferential direction from the tread end toward the tire equatorial plane CL (see FIGS. 2 and 3). Thereby, there exists an advantage which the drainage performance and snow drainage performance of the 1st lug groove 41 improve. For example, a configuration in which the first lug groove extends in the tire width direction while meandering (not shown) is not preferable because the drainage performance and snow removal performance of the first lug groove 41 cannot be sufficiently obtained.

  Moreover, in this pneumatic tire 1, the land parts 31-33 have the some sipe 5 (refer FIG. 2 and FIG. 3). Thereby, an edge component increases and there exists an advantage which the traction performance of a tire improves.

  In the pneumatic tire 1, the left and right land portions 32 and 33 that are opposed to each other across the outermost circumferential main groove 22 at the intersection of the outermost circumferential main groove 22 and the first lug groove 41 have tire widths. It has an edge portion offset in the direction (see FIG. 3). Thereby, there is an advantage that the traction component is increased and the on-ice performance and on-snow performance of the tire are improved.

  In the pneumatic tire 1, the tread rubber 15 has a rubber hardness of 60 to 75. Thereby, there exists an advantage by which the rigidity of a tread part is ensured appropriately.

[Applicable to]
The pneumatic tire 1 is preferably applied to a small truck tire having a JATMA prescribed maximum air pressure in a range of 350 [kPa] to 600 [kPa]. Since small truck tires are mainly used for local travel, center wear is likely to occur due to repeated stop-and-go. In this respect, in the pneumatic tire 1, the circumferential narrow groove 23 is disposed in the shoulder land portion 33, and therefore, compared with a configuration (not shown) in which the circumferential narrow groove is disposed in the center land portion or the second land portion. Thus, the rigidity of the center area of the tread portion is ensured. As a result, there is an advantage that the stop and go performance of the tire is improved and the occurrence of center wear is suppressed.

  FIG. 4 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 5 is an explanatory view showing a conventional pneumatic tire.

  In this performance test, evaluations on (1) uneven wear resistance, (2) performance on ice, and (3) performance on snow were performed on a plurality of different pneumatic tires (see FIG. 4). In this performance test, a pneumatic tire (small truck studless tire) with a tire size of 205 / 85R16 117 / 115L is assembled to an applicable rim specified by JATMA, and this pneumatic tire is given the highest pneumatic pressure and maximum load specified by JATMA. The Pneumatic tires are mounted on all wheels of a 3-ton truck that is a test vehicle.

  (1) In the evaluation on uneven wear resistance performance, the test vehicle travels on a paved road of 50,000 [km] at an average speed of 60 [km / h], and uneven wear generated on each land block is observed. . Then, based on the observation result, index evaluation using the conventional example as a reference (100) is performed. A larger value is preferable.

  (2) In the evaluation on the performance on ice, the test vehicle travels on the ice road surface and the braking distance from 40 [km / h] is measured. Then, based on the measurement result, index evaluation using the conventional example as a reference (100) is performed. A larger value is preferable.

  (3) In the evaluation on the performance on snow, the test vehicle travels on the snow road surface, and the braking distance from 40 [km / h] is measured. Then, based on the measurement result, index evaluation using the conventional example as a reference (100) is performed. A larger value is preferable.

  The pneumatic tire 1 of Example 1 has the configuration described in FIGS. The pneumatic tire 1 of Examples 2 to 8 is a modification of the pneumatic tire 1 of Example 1. The distance L from the tire equatorial plane CL to the ground contact end T is L = 156 [mm]. Further, the maximum groove depth H of the outermost circumferential main groove 22 is H = 13.0 [mm]. Further, the inclination angle β of the first lug groove 41 with respect to the tire width direction is β = 0 [deg] at the tread end, and increases toward the inner side in the tire width direction, and reaches the maximum value βmax at the end portion. Take.

  The conventional pneumatic tire has the configuration shown in FIG.

  As shown in the test results, in the pneumatic tires 1 of Examples 1 to 8, it is understood that the uneven wear resistance performance, the performance on ice, and the performance on snow are improved.

  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, 21: circumferential main groove, 22: outermost circumferential main groove, 23: circumferential narrow groove, 31: center land portion, 32: second land portion, 33: shoulder land portion, 41: first lug groove , 42: second lug groove, 5: sipe

Claims (14)

A pneumatic tire comprising at least four circumferential main grooves extending in a tire circumferential direction and a plurality of land portions defined by the circumferential main grooves,
The left and right circumferential main grooves on the outermost side in the tire width direction are referred to as outermost circumferential main grooves, and the land portion closest to the tire equator plane is referred to as a center land portion, and is divided into the outermost circumferential main grooves. When the land portion outside the tire width direction is called a shoulder land portion,
A plurality of first lug grooves that continuously extend from the tread end in the tire width direction and open to the circumferential main groove that defines the outer edge portion of the center land portion in the tire width direction;
A plurality of second lug grooves that pass through the center land portion in the tire width direction and are arranged in a staggered manner in the tire circumferential direction with respect to the first lug groove,
A circumferential narrow groove disposed in the shoulder land portion or the land portion adjacent to the shoulder land portion and extending in the tire circumferential direction ; and
The pneumatic tire according to claim 1, wherein an edge portion of the center land portion has a step portion offset in a tire width direction at an intersection position between the center land portion and the first lug groove .   2. The pneumatic tire according to claim 1, wherein the first lug groove extends continuously to the center land portion without intersecting the second lug groove and terminates inside the center land portion. The shoulder land portion has a block that is partitioned into a pair of the first lug grooves adjacent in the tire circumferential direction and the outermost circumferential main groove, and
The pneumatic tire according to claim 1, wherein the circumferential narrow groove has at least one bent portion inside the block.   The pneumatic tire according to claim 3, wherein a maximum value αmax of the bending angle α of the bending portion is in a range of 1 [deg] ≦ αmax ≦ 30 [deg].   5. The maximum groove depth Hs of the circumferential narrow groove and the maximum groove depth H of the circumferential main groove have a relationship of 0.40 ≦ Hs / H ≦ 0.80. The pneumatic tire according to one.   The distance Ls from the tire equatorial plane to the circumferential narrow groove and the distance L from the tire equatorial plane to the tire ground contact edge have a relationship of 0.70 ≦ Ls / L ≦ 0.90. The pneumatic tire according to any one of the above. At the intersection of the circumferential main groove and the second lug groove on the outer side in the tire width direction of the center land portion, on the center land portion side of the land portion on the outer side in the tire width direction of the center land portion. The pneumatic tire according to any one of claims 1 to 6 , wherein the edge portion is flush. The pneumatic tire according to any one of claims 1 to 7, wherein a step W1 of the stepped portion is in a range of 1 [mm] ≤ W1 ≤ 4 [mm]. The pneumatic value according to any one of claims 1 to 8 , wherein a maximum value βmax of an inclination angle β with respect to the tire width direction of the first lug groove is in a range of 1 [deg] ≤ βmax ≤ 30 [deg]. tire. The pneumatic tire according to claim 9 , wherein the first lug groove is inclined in one direction of the tire circumferential direction from the tread end toward the tire equatorial plane. The land portion, the pneumatic tire according to any one of claims 1-10 having a plurality of sipes. The left and right land portions facing each other across the outermost circumferential main groove at the intersection of the outermost circumferential main groove and the first lug groove have edge portions offset in the tire width direction. The pneumatic tire according to any one of 11 to 11 . The pneumatic tire according to any one of claims 1 to 12 , wherein the tread rubber has a rubber hardness of 60 to 75. The pneumatic tire according to any one of claims 1 to 13 , wherein the tire is applied to a small truck tire having a maximum air pressure defined by JATMA within a range of 350 [kPa] to 600 [kPa].

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