JP2013173448A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving wet performance, while securing partial abrasion resistant performance of the tire.SOLUTION: A pneumatic tire 1 includes blocks 5 formed by being partitioned by circumferential directional main grooves 21 and 22 and lug grooves 42 and 43. The block 5 has at least one circumferential directional groove part 51 arranged on a wall surface on the circumferential directional main groove 21(22) side of the block 5, extending along the circumferential directional main grooves 21(22) and opening in both end parts of the block 5. The groove cross-sectional area S of the circumferential directional groove part 51 becomes a maximum value S1 in one opening end part of the circumferential directional groove part 51, and becomes a minimum value S2 in the other opening end part.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of improving wet performance while ensuring uneven wear resistance performance of the tire.

  In recent pneumatic tires, in a configuration having a block pattern, the block has a groove on the wall surface on the circumferential main groove side in order to improve drainage of the circumferential main groove and improve the wet performance of the tire. . As a conventional pneumatic tire employing such a configuration, a technique described in Patent Document 1 is known.

JP 2006-137239 A

  On the other hand, a pneumatic tire has a problem to improve uneven wear resistance.

  Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire that can improve wet performance while ensuring uneven wear resistance performance of the tire.

  In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire having a block defined by a circumferential main groove and a lug groove, wherein the block is the circumferential main groove of the block. The groove has at least one circumferential groove that is arranged on the wall surface on the groove side and extends along the circumferential main groove and opens at both ends of the block, and the groove sectional area S of the circumferential groove Is a maximum value S1 at one opening end of the circumferential groove and a minimum value S2 at the other opening end.

  In the pneumatic tire according to the present invention, since the block has the circumferential groove portion on the wall surface on the circumferential main groove side, the groove cross-sectional area of the circumferential groove portion is increased and the drainage performance of the circumferential main groove is improved. Thereby, there exists an advantage which the wet performance of a tire improves. Further, since the groove cross-sectional area S of the circumferential groove portion has the maximum value S1 at one opening end portion and the minimum value S2 at the other opening end portion, the edge on the side where the groove cross-sectional area S becomes the maximum value S1 The rigidity of the block in the part is lower than the rigidity of the block in the other edge part. Then, when the pneumatic tire is attached to the vehicle with the groove cross-sectional area S of the circumferential groove portion having the maximum value S1 as the tire rotation direction, the rigidity at the edge portion on the stepping side of the block is reduced, The rigidity at the edge portion on the kicking side of the block is increased. This improves the uneven wear resistance (heel and toe wear resistance) of the tire.

FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a plan view showing a tread surface of the pneumatic tire depicted in FIG. 1. FIG. 3 is an explanatory view showing a circumferential groove portion of the block of the pneumatic tire shown in FIG. 1. FIG. 4 is an explanatory view showing a circumferential groove of the block of the pneumatic tire shown in FIG. FIG. 5 is an explanatory view showing a circumferential groove portion of the block of the pneumatic tire shown in FIG. 1. FIG. 6 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. FIG. 7 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. FIG. 8 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. FIG. 9 is an explanatory view illustrating a modified example of the pneumatic tire depicted in FIG. 1. FIG. 10 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. FIG. 11 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. FIG. 12 is an explanatory diagram illustrating a modification of the pneumatic tire depicted in FIG. 1. FIG. 13 is an explanatory view illustrating a modified example of the pneumatic tire depicted in FIG. 1. FIG. 14 is an explanatory view showing a modified example of the pneumatic tire depicted in FIG. 1. FIG. 15 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. FIG. 16 is an explanatory diagram illustrating a modification of the pneumatic tire depicted in FIG. 1. FIG. 17 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 18 is an explanatory view showing the pneumatic tire of Comparative Example 1. FIG. 19 is an explanatory view showing the pneumatic tire of Comparative Example 2.

  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 1 according to an embodiment of the present invention. The figure shows a radial tire for a passenger car as an example of the pneumatic tire 1. Reference sign CL is a tire equator plane.

  The pneumatic tire 1 includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16, and a pair. Rim cushion rubbers 17 and 17 (see FIG. 1).

  The pair of bead cores 11 and 11 has an annular structure 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 has a single-layer structure and is bridged in a toroidal shape between the left and right bead cores 11 and 11 to constitute 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 coating a plurality of carcass cords made of steel or an organic fiber material (for example, nylon, polyester, rayon, etc.) with a coating rubber and rolling them, and has an absolute value of 85 [deg] or more and 95. [Deg] The following carcass angle (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 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 having a belt angle of 10 [deg] or more and 30 [deg] or less in absolute value. 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 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.

  FIG. 2 is a plan view showing a tread surface of the pneumatic tire 1 shown in FIG. 1. This figure shows a general block pattern.

  The pneumatic tire 1 includes four circumferential main grooves 21 and 22 extending in the tire circumferential direction, five rows of land portions 31 to 33 partitioned by the circumferential main grooves 21 and 22, and these The tread portion includes a plurality of lug grooves 41 to 43 that cross the land portions 31 to 33 in the tire width direction (see FIG. 2).

  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 and 22 define a center land portion 31, left and right second land portions 32 and 32, and left and right shoulder land portions 33 and 33. Moreover, all the land parts 31-33 each have the several lug grooves 41-43 extended in a tire width direction. These lug grooves 41 to 43 have an open structure that crosses the land portions 31 to 33 in the tire width direction, and are arranged at predetermined intervals in the tire circumferential direction. Thereby, all the land parts 31-33 become the block row | part divided into the some block 5. FIG.

  The circumferential main groove refers to a circumferential groove having a groove width of 3 [mm] or more. The lug groove refers to a lateral groove having a groove width of 1 [mm] or more.

[Specify rotation direction]
Moreover, this pneumatic tire 1 has designation | designated of a tire rotation direction. The tire rotation direction refers to a rotation direction that is frequently used when the tire is used, for example, a rotation direction when the vehicle moves forward. The designation of the rotation direction is displayed by, for example, marks or irregularities attached to the sidewall portion of the tire. In this embodiment, on the basis of the designation of the rotation direction, the stepping side of the block 5 (the side that comes in contact first when the tire rolls in the designated rotation direction) and the kicking side (the opposite side to the stepping side) ) Is defined (see FIG. 2).

[Block groove]
3-5 is explanatory drawing which shows the circumferential direction groove part 51 of the block 5 of the pneumatic tire 1 described in FIG. In these drawings, FIG. 3 shows a perspective view of the block 5 of the second land portion 32 and the block 5 of the shoulder land portion 33. 4 and 5 schematically show a plan view (FIG. 4) and a sectional view taken along the line XX (FIG. 5) of the wall surface of the block 5 on the circumferential main groove 21 side.

  In this pneumatic tire 1, the block 5 has a circumferential groove 51 (see FIGS. 2 and 3). The circumferential groove 51 is disposed on the wall surface of the block 5 on the circumferential main groove 21 (22) side, extends along the circumferential main groove 21 (22), and opens at both ends of the block 5. The block 5 may have at least one circumferential groove 51 on at least one wall surface. Further, only some of the blocks 5 may have the circumferential groove 51. For example, only each block 5 in the block row that is likely to cause heel and toe wear may have the circumferential groove 51.

  For example, in the configuration of FIGS. 2 and 3, all the blocks 5 each have a circumferential groove 51. Further, the center land portion 31 and the left and right second land portions 32 and 32 have circumferential groove portions 51 on the wall surfaces on the left and right circumferential main grooves 21 and 22 side, respectively. Further, the left and right shoulder land portions 33, 33 have the circumferential groove portion 51 only on the wall surface on the circumferential main groove 22 side. Accordingly, the circumferential groove 51 is not formed in the outer region of the tire ground contact surface.

  Further, the distance D1 from the groove bottom of the circumferential main groove 21 (22) to the circumferential groove 51 and the groove depth D of the circumferential main groove 21 (22) are 0.10 ≦ D1 / D ≦ 0. 60 relationships (see FIG. 3). The groove depth D of the circumferential main grooves 21 and 22 is measured as the distance from the tread surface of the block 5 to the maximum groove depth position of the circumferential main grooves 21 and 22. The distance D1 of the circumferential groove 51 is measured as the distance from the groove bottom of the circumferential main groove 21 (22) to the groove center line of the circumferential groove 51.

  As shown in FIG. 4, the groove cross-sectional area S of the circumferential groove 51 takes a maximum value S1 at the opening end of one of the circumferential grooves 51 (the stepping side in the tire rotation direction) and the other (tire rotation). The minimum value S2 is taken at the opening end of the direction kicking side. At this time, it is preferable that the groove cross-sectional area S of the circumferential groove 51 increases monotonously from one opening end of the circumferential groove 51 toward the other opening end. The concept of monotonic increase includes a case where the groove cross-sectional area S is constant in part. The groove cross-sectional area S is measured in a cross-sectional view perpendicular to the tire circumferential direction.

  The maximum value S1 and the minimum value S2 of the groove cross-sectional area S of the circumferential groove 51 are preferably in the range of 1.1 ≦ S1 / S2 ≦ 15, and 2.5 ≦ S1 / S2 ≦ 8.0. It is preferable to be within the range. Thereby, the ratio S1 / S2 between the maximum value S1 and the minimum value S2 of the groove cross-sectional area S is optimized.

  For example, in the configuration of FIG. 4, the groove depth A of the circumferential groove 51 is constant, and the groove width B of the circumferential groove 51 is changed from the opening end on the kicking side in the tire rotation direction to the opening end on the stepping side. It is increasing monotonously. Further, the groove width B of the circumferential groove 51 takes a minimum value B2 at the opening end on the kicking side and takes a maximum value B1 on the opening end on the stepping side. As a result, the groove cross-sectional area S of the circumferential groove 51 becomes the maximum value S1 at the opening end on the stepping side in the tire rotation direction, and becomes the minimum value S2 at the opening end on the kick-out side in the tire rotation direction. Yes.

  In such a configuration, since the block 5 has the circumferential groove 51 on the wall surface on the circumferential main groove 21 (22) side (see FIG. 3), the groove cross-sectional area of the circumferential groove 51 increases and the circumferential main groove 21, The drainage of 22 is improved. Thereby, the wet performance of a tire improves.

  Further, since the groove cross-sectional area S of the circumferential groove 51 is the maximum value S1 at one opening end and the minimum value S2 at the other opening end (see FIG. 4), the groove cross-sectional area S is the maximum value. The rigidity of the block 5 at the edge portion on the side that becomes S1 is lower than the rigidity of the block 5 at the other edge portion. Then, when the pneumatic tire 1 is attached to the vehicle with the groove cross-sectional area S of the circumferential groove portion having the maximum value S1 as the tire rotation direction, the rigidity at the stepped-side edge portion of the block 5 is reduced. This improves the riding comfort and noise resistance of the tire. On the other hand, the rigidity at the edge portion on the kick-out side of the block 5 is increased, and the uneven wear resistance (heel and toe wear resistance) of the tire is improved.

  In this pneumatic tire 1, the maximum value B1 and the minimum value B2 of the groove width of the circumferential groove 51 and the groove depth D of the circumferential main groove 21 (22) are 0.10 ≦ B1 / D ≦. 0.35 and 0.05 ≦ B2 / D ≦ 0.25. Further, the maximum value A1 and the minimum value A2 of the groove depth of the circumferential groove 51 and the groove width W of the circumferential main groove 21 (22) are 0.10 ≦ A1 / W ≦ 0.30 and 0.05. ≦ A2 / W ≦ 0.20.

  Moreover, the block 5 has the width direction groove part 52 (refer FIG. 2 and FIG. 3). The width direction groove portion 52 is disposed on the wall surface of the block 5 on the lug grooves 41 to 43 side, extends along the lug grooves 41 to 43, and communicates with the circumferential groove portion 51.

  For example, in the configuration of FIG. 2, each block 5 of the center land portion 31 and each block 5 of the left and right second land portions 32, 32 are respectively provided with circumferential groove portions 51 on the wall surfaces on the left and right circumferential main grooves 21, 22 side. Have. Each block 5 of the shoulder land portion 33 has a circumferential groove portion 51 only on the wall surface on the circumferential main groove 22 side.

  Further, as shown in FIG. 3, the width direction in which the block 5 (the block 5 of the center land portion 31 and the second land portion 32) having the circumferential groove portions 51 on the left and right wall surfaces connects the left and right circumferential groove portions 51, 51. A groove portion 52 is provided, and the widthwise groove portion 52 is provided on both the stepping side wall surface and the kicking side wall surface. On the other hand, the block 5 (the block 5 of the shoulder land portion 33) having the circumferential groove 51 only on the wall surface on one side is extended from the circumferential groove 51 along the lug grooves 41 to 43 by one widthwise groove 52. The width direction groove portion 52 is provided on both the stepping side wall surface and the kicking side wall surface. Further, these width direction groove portions 52 have a constant groove depth and a groove width, thereby having a constant groove cross-sectional area.

  Further, the groove sectional area of the widthwise groove 52 on the stepping side (the side where the groove sectional area S of the circumferential groove 51 becomes the maximum value S1) is the same as the kicking side (the groove sectional area S of the circumferential groove 51). It is larger than the groove cross-sectional area of the width direction groove portion 52 of the wall surface on the side of the minimum value S2.

  For example, in the configuration of FIG. 3, the left and right circumferential groove portions 51, 51 of the block 5 have the same shape. And the groove cross-sectional area S of these circumferential direction groove parts 51 and 51 has the same maximum value S1 in the open end part of the step-on side of the block 5, and is the same in the open end part on the kicking side It has a minimum value S2. As a result, a difference is provided between the groove cross-sectional area of the widthwise groove 52 on the stepping side and the groove cross-sectional area of the widthwise groove 52 on the kicking side.

  6-8 is explanatory drawing which shows the modification of the pneumatic tire 1 described in FIG. These drawings show a plan view of the wall surface of the block 5 on the circumferential main groove 21 side.

  3 to 5, as described above, the groove depth A of the circumferential groove 51 is constant, and the groove width B of the circumferential groove 51 is stepped on from the opening end on the kicking side in the tire rotation direction. It increases monotonously toward the opening end on the side. Further, the groove width B of the circumferential groove portion 51 is a minimum value B2 at the opening end portion on the kicking side, and is a maximum value B1 at the opening end portion on the stepping side. Thereby, the groove cross-sectional area S of the circumferential groove 51 becomes the maximum value S1 at the opening end on the kicking side in the tire rotation direction, and becomes the minimum value S2 at the opening end on the stepping side in the tire rotation direction. Yes.

  However, the present invention is not limited to this, and the groove width B of the circumferential groove 51 is constant, and the groove depth A of the circumferential groove 51 extends from the opening end on the kicking side in the tire rotation direction to the opening end on the stepping side. May be monotonously increased (not shown). Further, both the groove depth A and the groove width B of the circumferential groove 51 may monotonously increase from the opening end on the kicking side in the tire rotation direction toward the opening end on the stepping side (not shown). . Similar effects can be obtained with these configurations.

  In addition, the groove cross-sectional area S (groove depth A, groove width B) of the circumferential groove 51 may be increased or decreased midway (not shown). Therefore, it is sufficient that at least the groove cross-sectional area S of the circumferential groove 51 is the maximum value S1 at the opening end on the kicking side and the minimum value S2 at the opening end on the stepping side in the tire rotation direction.

  4, the left and right groove walls of the circumferential groove 51 have a linear shape inclined in the height direction of the block 5 in a plan view of the wall surface of the block 5. The width B monotonously increases from the opening end on the kicking side toward the opening end on the stepping side.

  However, the present invention is not limited thereto, and the left and right groove walls of the circumferential groove 51 may change the inclination angle in the middle from the kicking side to the stepping side. For example, as shown in FIG. 6, on the way from the kicking side to the stepping side, the left and right groove walls of the circumferential groove 51 are parallel, and the groove width B (groove cross-sectional area S) of the circumferential groove 51 is constant. It may be. Moreover, as shown in FIG. 7, the left and right groove walls of the circumferential groove 51 may be curved in a parabolic shape.

  In the configuration of FIG. 4, the block 5 has one circumferential groove 51 on the wall surface of one circumferential groove 51.

  However, the present invention is not limited to this, and the block 5 may have a plurality of circumferential groove portions 51 on the wall surface of one circumferential groove portion 51. For example, as shown in FIG. 8, two circumferential groove portions 51 may be arranged on the wall surface of one circumferential groove portion 51 and run side by side from the kicking side of the block 5 toward the stepping side.

  9-14 is explanatory drawing which shows the modification of the pneumatic tire 1 described in FIG. These drawings show sectional views of the circumferential groove 51.

  In the configuration of FIG. 5, the circumferential groove 51 has a substantially trapezoidal cross-sectional shape with a groove width narrowed toward the groove bottom side.

  However, the present invention is not limited to this, and the circumferential groove 51 may have an arbitrary cross-sectional shape (see FIGS. 9 to 14). For example, in the modification of FIG. 9, the circumferential groove 51 has a rectangular cross-sectional shape, and in the modification of FIG. 10, the circumferential groove 51 has a semicircular cross-sectional shape. 11 and 12, the circumferential groove 51 has a triangular cross-sectional shape. At this time, the triangle of the cross-sectional shape may be an isosceles triangle having the groove opening side as a base (see FIG. 11), or a triangle whose apex is directed to the groove bottom side of the circumferential main groove 21 (22). (Refer to FIG. 12) or a triangle (not shown) directed toward the groove opening side of the circumferential main groove 21 (22). Moreover, like the modified examples of FIGS. 13 and 14, the circumferential groove 51 may have a cross-sectional shape having a convex portion at the groove bottom. At this time, it is a requirement that the groove bottom of the circumferential groove portion 51 does not protrude from the wall surface of the block 5 into the circumferential main groove 21 (22) (does not become a protrusion).

  FIG. 15 and FIG. 16 are explanatory views showing a modification of the pneumatic tire 1 shown in FIG. These drawings show perspective views of the block 5 of the second land portion 32 and the block 5 of the shoulder land portion 33.

  As described above, in the configuration of FIG. 3, the block 5 has the width direction groove portions 52 on the kick-out wall surface and the stepping-side wall surface, respectively.

  However, the present invention is not limited to this, and the block 5 may have the width direction groove 52 only on the wall surface on the stepping side as in the modification of FIG. 15, or the width direction groove 52 as in the modification of FIG. May be omitted.

[effect]
As described above, the pneumatic tire 1 includes the block 5 that is divided into the circumferential main grooves 21 and 22 and the lug grooves 41 to 43 (see FIG. 2). In addition, the block 5 is disposed on the wall surface of the block 5 on the circumferential main groove 21 (22) side and extends along the circumferential main groove 21 (22) and opens at both ends of the block 5. There are two circumferential grooves 51 (see FIG. 3). Further, the groove cross-sectional area S of the circumferential groove 51 is a maximum value S1 at one opening end of the circumferential groove 51 and a minimum S2 at the other opening end (see FIG. 4).

  In such a configuration, since the block 5 has the circumferential groove 51 on the wall surface on the circumferential main groove 21 (22) side (see FIG. 3), the groove cross-sectional area of the circumferential groove 51 increases and the circumferential main groove 21, The drainage of 22 is improved. Thereby, there exists an advantage which the wet performance of a tire improves.

  Further, since the groove cross-sectional area S of the circumferential groove 51 is the maximum value S1 at one opening end and the minimum value S2 at the other opening end (see FIG. 4), the groove cross-sectional area S is the maximum value. The rigidity of the block 5 at the edge portion on the side that becomes S1 is lower than the rigidity of the block 5 at the other edge portion. Then, when the pneumatic tire 1 is attached to the vehicle with the groove cross-sectional area S of the circumferential groove portion having the maximum value S1 as the tire rotation direction, the rigidity at the stepped-side edge portion of the block 5 is reduced. Thereby, there exists an advantage which the riding comfort and noise resistance of a tire improve. On the other hand, there is an advantage that the rigidity at the edge portion on the kick-out side of the block 5 is increased, and the uneven wear resistance (heel and toe wear resistance) of the tire is improved.

  Moreover, in this pneumatic tire 1, the groove cross-sectional area S of the circumferential groove 51 increases monotonously from one opening end of the circumferential groove to the other opening end (see FIGS. 3 and 4). . Thereby, the groove cross-sectional area S of the circumferential direction groove part 51 is optimized.

  Moreover, in this pneumatic tire 1, the groove width B of the circumferential groove 51 increases monotonously from one opening end of the circumferential groove 51 toward the other opening end (see FIG. 4). Thereby, the groove width B of the circumferential groove 51 is optimized.

  In this pneumatic tire 1, the groove depth A of the circumferential groove 51 may monotonously increase from one opening end of the circumferential groove 51 toward the other opening end (not shown). Thereby, the groove depth A of the circumferential groove 51 is optimized.

  In this pneumatic tire 1, the block 5 is arranged on the wall surface on the side of the lug groove 41 (42, 43) side of the block 5 and the groove cross-sectional area S of the circumferential groove portion 51 is the maximum value S 1, and the lug It has the width direction groove part 52 extended along the groove | channel 41 (42, 43) and connected to the circumferential direction groove part 51 (refer FIG. 3). In such a configuration, the width-direction groove 52 reduces the rigidity of the block 5 at the edge portion on the side where the groove cross-sectional area S becomes the maximum value S1. Then, when the pneumatic tire 1 is attached to the vehicle with the groove cross-sectional area S of the circumferential groove portion having the maximum value S1 as the tire rotation direction, the rigidity at the stepped-side edge portion of the block 5 is reduced. Thereby, there exists an advantage which the riding comfort and noise resistance of a tire improve.

  Moreover, in this pneumatic tire 1, the block 5 has the width direction groove parts 52 and 52 in the wall surface of the lug grooves 41 and 41 (42, 42; 43, 43) side before and behind the block 5, respectively (refer FIG. 3). . Further, the groove cross-sectional area of the widthwise groove 52 on the side where the groove cross-sectional area S of the circumferential groove 51 becomes the maximum value S <b> 1 is larger than the groove cross-sectional area of the other widthwise groove 52. In such a configuration, the rigidity of the block 5 at the edge portion on the side where the groove cross-sectional area S is the maximum value S1 is low, and the rigidity of the other block 5 is high. As a result, when the pneumatic tire 1 is attached to the vehicle with the groove cross-sectional area S of the circumferential groove portion having the maximum value S1 as the tire rotation direction, the rigidity of the front and rear edge portions of the block 5 is optimized. Thus, there is an advantage that the riding comfort, noise resistance and uneven wear resistance of the tire are improved.

  Further, in this pneumatic tire 1, the distance D1 from the groove bottom of the circumferential main groove 21 (22) to the circumferential groove 51 and the groove depth D of the circumferential main groove 21 (22) are 0.10. ≦ D1 / D ≦ 0.60 (see FIG. 3). Thereby, there exists an advantage by which the relationship between the groove width of the circumferential groove part 51 and the groove depth D of the circumferential main groove 21 (22) is optimized.

  In the pneumatic tire 1, the maximum value B1 and the minimum value B2 of the groove width B of the circumferential groove 51 and the groove depth D of the circumferential main groove 21 (22) are 0.10 ≦ B1 / D. ≦ 0.35 and 0.05 ≦ B2 / D ≦ 0.25 (see FIGS. 3 and 4). Further, the maximum value A1 and the minimum value A2 of the groove depth A (see FIG. 5) of the circumferential groove 51 and the groove width W of the circumferential main groove 21 (22) are 0.10 ≦ A1 / W ≦ 0. .30 and 0.05 ≦ A2 / W ≦ 0.20. Thereby, there is an advantage that the relationship between the groove width B and the groove depth A of the circumferential groove 51 and the groove depth D and the groove width W of the circumferential main groove 21 (22) is optimized.

  In addition, the pneumatic tire 1 has a designation to be mounted on the vehicle with the side where the groove cross-sectional area S of the circumferential groove 51 is the maximum value S1 as the tire rotation direction (see FIGS. 3 and 4). Thereby, the rigidity of the edge part before and behind the block 5 is optimized, and there exists an advantage which the riding comfort, noise resistance, and uneven wear resistance of a tire improve.

  FIG. 17 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. 18 and 19 are explanatory views showing the pneumatic tires of Comparative Examples 1 and 2. FIG.

  In this performance test, evaluations on (1) wet performance, (2) riding comfort performance and noise resistance performance, and (3) uneven wear resistance performance were performed on a plurality of different pneumatic tires (FIG. 17). reference). In this performance test, a pneumatic tire having a tire size of 215 / 60R16 95H is assembled to an applicable rim specified by JATMA, and an air pressure of 220 [kPa] and a maximum load specified by JATMA are applied to the pneumatic tire. The pneumatic tire is mounted on a passenger car having a displacement of 2500 [cc], which is a test vehicle.

(1) In the evaluation on wet performance, the test vehicle travels on a test course with a water depth of 10 ± 1 [mm] and a turning radius of 100 [m], and the travel speed of the test vehicle is measured when the maximum lateral acceleration of the tire occurs. To do. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation is more preferable as the numerical value is larger, and if it is 105 or more, it is recognized that there is an advantage.

  (2) In the evaluation on ride performance and noise resistance, the test vehicle runs on the dry road evaluation course, and a specialized test driver performs sensory evaluation. This evaluation is performed by index evaluation using the conventional example as a reference (100), and the larger the value, the better. Moreover, if evaluation is 105 or more, it will be recognized that there exists an advantage.

  (3) In the evaluation on the uneven wear resistance, the heel and toe wear amount of the block after the test vehicle travels 8000 [km] is measured. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation is preferable as the numerical value increases. Moreover, if evaluation is 100 or more, it can be said that the partial wear-proof performance is ensured appropriately.

  The pneumatic tires 1 of Examples 1 to 6 have the configurations of FIGS. 1 to 5, and all the blocks 5 have a circumferential groove 51 and a width groove 52. Further, the pneumatic tire 1 is mounted on the test vehicle with the side where the groove cross-sectional area S of the circumferential groove 51 is the maximum value S1 as the tire rotation direction. Moreover, the groove depth D (refer FIG. 3) of the circumferential direction main grooves 21 and 22 is D = 8.0 [mm]. Moreover, the position D1 of the circumferential direction groove part 51 and the width direction groove part 52 is D1 = 0.8-4.8 [mm]. Moreover, in the pneumatic tire 1 of Example 7, in the structure of Example 1, the block 5 has the width direction groove part 52 only on the stepping side (refer FIG. 15). Moreover, in the pneumatic tire 1 of Example 8, the block 5 does not have the width direction groove part 52 in the structure of Example 1 (refer FIG. 16).

  In the conventional pneumatic tire, in the configuration of Example 1, the block 5 does not have either the circumferential groove 51 or the width groove 52 (not shown). The pneumatic tire of Comparative Example 1 has a circumferential groove portion having an equal width in the configuration of the conventional example (see FIG. 18). In the pneumatic tire of Comparative Example 2, the block has a non-penetrating circumferential groove in the configuration of the conventional example (see FIG. 19).

  As shown in the test results, in the pneumatic tires 1 of Examples 1 to 8, it is understood that the wet performance can be improved while ensuring the uneven wear resistance performance of the tire. It can also be seen that the riding comfort performance and noise resistance performance can be improved.

  DESCRIPTION OF SYMBOLS 1 Pneumatic tire, 21, 22 Circumferential main groove, 31-33 Land part, 41-43 Lug groove, 5 blocks, 51 Circumferential groove part, 52 Width direction groove part, 11 Bead core, 12 Bead filler, 13 Carcass layer, 14 Belt layer, 141, 142 Cross belt, 15 tread rubber, 16 side wall rubber, 17 rim cushion rubber

Claims (9)

A pneumatic tire having a block divided into a circumferential main groove and a lug groove,
The block has at least one circumferential groove that is disposed on a wall surface of the block on the circumferential main groove side and extends along the circumferential main groove and opens at both ends of the block. and,
A pneumatic tire characterized in that a groove cross-sectional area S of the circumferential groove portion has a maximum value S1 at one opening end portion of the circumferential groove portion and a minimum value S2 at the other opening end portion.   The pneumatic tire according to claim 1, wherein a groove cross-sectional area S of the circumferential groove portion monotonously increases from one opening end portion of the circumferential groove portion toward the other opening end portion.   The pneumatic tire according to claim 1 or 2, wherein a groove width of the circumferential groove portion monotonously increases from one opening end portion of the circumferential groove portion toward the other opening end portion.   The pneumatic tire according to any one of claims 1 to 3, wherein a groove depth of the circumferential groove portion monotonously increases from one opening end portion of the circumferential groove portion toward the other opening end portion.   The block is disposed on the wall surface on the lug groove side of the block and on the side where the groove cross-sectional area S of the circumferential groove portion has a maximum value S1, and extends along the lug groove to the circumferential groove portion. The pneumatic tire as described in any one of Claims 1-4 which has the width direction groove part connected.   The block has the widthwise groove portion on the wall surface on the lug groove side before and after the block, and the groove cutting of the widthwise groove portion on the side where the groove cross-sectional area S of the circumferential groove portion becomes the maximum value S1. The pneumatic tire according to claim 5, wherein the area is larger than a groove cross-sectional area of the other widthwise groove portion.   The distance D1 from the groove bottom of the circumferential main groove to the circumferential groove and the groove depth D of the circumferential main groove have a relationship of 0.10 ≦ D1 / D ≦ 0.60. The pneumatic tire as described in any one of -6.   The maximum value B1 and minimum value B2 of the groove width of the circumferential groove portion and the groove depth D of the circumferential main groove are 0.10 ≦ B1 / D ≦ 0.35 and 0.05 ≦ B2 / D ≦. The maximum value A1 and the minimum value A2 of the groove depth of the circumferential groove portion and the groove width W of the circumferential main groove are 0.10 ≦ A1 / W ≦ 0. The pneumatic tire according to any one of claims 1 to 7, having a relationship of .30 and 0.05 ≦ A2 / W ≦ 0.20.   The pneumatic tire according to any one of claims 1 to 8, wherein the pneumatic tire has a designation to be mounted on a vehicle with a side where the groove cross-sectional area S of the circumferential groove portion is a maximum value S1 as a tire rotation direction.

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