JP5835399B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can improve uneven wear resistance of a tire.

  In recent years, a small truck studless tire employs a traction pattern including a plurality of block rows having sipes in order to improve the performance on ice and the performance on snow. As such a conventional pneumatic tire, a technique described in Patent Document 1 is known.

JP 2009-12671 A

  On the other hand, in the configuration having the traction pattern as described above, there is a problem that uneven wear (particularly, heel and toe wear) of the block should be suppressed.

  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 uneven wear resistance of the tire.

In order to achieve the above object, a pneumatic tire according to the present invention includes a plurality of circumferential main grooves extending in the tire circumferential direction, and a plurality of land portions defined by the circumferential main grooves. In the tire, the circumferential main groove on the outermost side in the tire width direction is referred to as an outermost circumferential main groove, and the land portion on the outer side in the tire width direction defined by the outermost circumferential main groove is a shoulder land portion. The shoulder land portion has one circumferential narrow groove extending in the tire circumferential direction, and extends inward in the tire width direction from the circumferential narrow groove and opens into the outermost circumferential main groove. A plurality of inner lug grooves, a plurality of outer lug grooves extending from the circumferential narrow groove to the tire width direction outside and reaching the tire ground contact end, the outermost circumferential main groove, the circumferential narrow groove, and the plurality A plurality of inner blocks that are partitioned into inner lug grooves of A plurality of outer blocks that are partitioned into the circumferential narrow groove, the tire ground contact edge, and the plurality of outer lug grooves, and the inner block and the outer block are centered on the circumferential narrow groove. Staggered arrangement in the circumferential direction, the edge portion on the outermost circumferential main groove side of the inner block has a step shape with amplitude in the tire width direction, and the inner block has a notch in the step shape step And the step-shaped stepped portion has a tread surface continuous in the tire circumferential direction .

  In the pneumatic tire according to the present invention, the inner block and the outer block are arranged in a zigzag manner in the tire circumferential direction with the circumferential narrow groove as a center. And the outer block continuously mesh in the tire circumferential direction. Thereby, there is an advantage that rigidity in the tire circumferential direction of the shoulder land portion is ensured, and uneven wear of the block (particularly, heel and toe wear) is suppressed.

FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a plan view showing a tread surface of the pneumatic tire depicted in FIG. 1. FIG. 3 is an explanatory diagram illustrating a shoulder land portion of the tread pattern illustrated in FIG. 2. FIG. 4 is an explanatory view showing a shoulder land portion of the tread pattern shown in FIG. FIG. 5 is an explanatory diagram illustrating an example of a three-dimensional sipe. FIG. 6 is an explanatory diagram illustrating an example of a three-dimensional sipe. FIG. 7 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. 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 (particularly cap rubber constituting the tread surface) preferably has a rubber hardness of 50 or more and 75 or less, and more preferably 60 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. The figure shows the traction pattern of the studless tire. In FIG. 2, the tire circumferential direction refers to the direction around the tire rotation axis. Moreover, the code | symbol T is a tire grounding end.

  As shown in FIG. 2, the pneumatic tire 1 includes a plurality of circumferential main grooves 21 and 22 extending in the tire circumferential direction, and a plurality of land portions defined by the circumferential main grooves 21 and 22. The tread portion includes 31 to 33 and a plurality of lug grooves 41 to 44 extending in the tire width direction.

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

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

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

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

  Here, 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 portions 31 and 32 located on the inner side in the tire width direction from the left and right outermost circumferential main grooves 22 and 22 are referred to as center land portions. Further, the land portions 33, 33 located on the outer side in the tire width direction from the left and right outermost circumferential main grooves 22, 22 are referred to as shoulder land portions.

  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 three rows of center land portions 31, 32 and 32 and a pair of left and right shoulder land portions 33 and 33. Further, left and right shoulder land portions 33 and 33 are disposed on the left and right tire ground contact ends T and T, respectively.

  However, the present invention is not limited thereto, and the circumferential main grooves 21 and 22 may be arranged asymmetrically about the tire equatorial plane CL (not shown). Further, the circumferential main groove may be disposed on the tire equatorial plane CL (not shown). In addition, three or more circumferential main grooves may be arranged (not shown).

[Shoulder land]
3 and 4 are explanatory views showing a shoulder land portion of the tread pattern shown in FIG. In these drawings, FIG. 3 shows an enlarged plan view of one shoulder land portion 33, and FIG. 4 shows an enlarged sectional view of the shoulder land portion 33 in the tire meridian direction.

  As shown in FIG. 2 and FIG. 3, in the pneumatic tire 1, the shoulder land portion 33 includes one circumferential narrow groove 23, a plurality of inner lug grooves 43 and a plurality of outer lug grooves 44, and A plurality of inner blocks 331 and a plurality of outer blocks 332 defined by the grooves 23, 43, 44 are provided.

  The circumferential narrow groove 23 is a narrow groove extending in the tire circumferential direction (see FIGS. 2 and 3). The circumferential narrow groove 23 is disposed in the ground contact surface of the shoulder land portion 33. Further, the circumferential narrow groove 23 may have a straight shape, or may have a bent shape or a wavy shape.

  For example, in the configuration of FIG. 2, one circumferential narrow groove 23 is disposed in each of the left and right shoulder land portions 33 and 33. Moreover, the circumferential direction narrow groove 23 is arrange | positioned in the area | region between the outermost periphery direction main groove 22 and the tire grounding end T, and has divided the grounding surface of the shoulder land part 33 into the tire width direction.

  Further, as shown in FIG. 3, the circumferential narrow groove 23 has a bent shape having a plurality of bending points (points indicated by “◯” in the drawing), and has an amplitude in the tire width direction and the tire circumference. Zigzag extends in the direction. In such a configuration, the circumferential narrow groove 23 is closed when the tire is in contact with the ground, and the opposing groove walls of the circumferential narrow groove 23 mesh with each other in the tire circumferential direction. Thereby, the rigidity in the tire circumferential direction of the shoulder land portion 33 is ensured.

  3, the bending angle α of the bent shape of the circumferential narrow groove 23 is preferably in the range of 1 [deg] ≦ α ≦ 30 [deg], and 5 [deg] ≦ α ≦ 25 [deg]. ] Is more preferable. Thereby, the bending angle α of the circumferential narrow groove 23 is optimized.

  The bend angle α is an angle formed by the groove center line at the bending point of the bent shape of the circumferential narrow groove 23 and the tire circumferential direction, and is measured with the tire mounted on the specified rim to apply the specified internal pressure and in the no-load state. Is done.

  3, the groove width W2 of the circumferential narrow groove 23 is preferably in the range of 1.0 [mm] ≦ W2 ≦ 3.0 [mm], and 1.7 [mm] ≦ W2 ≦. More preferably within the range of 2.3 [mm]. Thereby, the groove width W2 of the circumferential narrow groove 23 is optimized.

  The groove width W2 of the circumferential narrow groove 23 is a distance between the facing groove walls in the groove opening, and is measured while a tire is mounted on a specified rim to apply a specified internal pressure and in an unloaded state. 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.

  In FIG. 4, it is preferable that the groove depth H2 of the circumferential narrow groove 23 and the groove depth H1 of the outermost circumferential main groove 22 have a relationship of 0.40 ≦ H2 / H1 ≦ 0.70. . Thereby, the groove depth H2 of the circumferential narrow groove 23 is optimized.

  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. As a result, the position of the circumferential narrow groove 23 in the tire contact surface is optimized.

  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.

  The inner lug groove 43 is a lateral groove that extends inward in the tire width direction from the circumferential narrow groove 23 and opens to the outermost circumferential main groove 22 (see FIGS. 2 and 3). That is, the inner lug groove 43 is disposed in a region between the outermost circumferential main groove 22 and the circumferential narrow groove 23 and extends in the tire width direction. The inner lug groove 43 opens to the circumferential narrow groove 23 at one end, and opens to the outermost circumferential main groove 22 at the other end. As a result, the outermost circumferential main groove 22 and the circumferential narrow groove 23 communicate with each other via the inner lug groove 43. A plurality of inner lug grooves 43 are arranged at predetermined intervals in the tire circumferential direction.

  The outer lug groove 44 is a lateral groove extending from the circumferential narrow groove 23 to the tire width direction outer side and reaching the tire ground contact end T (see FIGS. 2 and 3). That is, the outer lug groove 44 is disposed at least in a region between the circumferential narrow groove 23 and the tire ground contact edge T and extends in the tire width direction. The outer lug groove 44 opens into the circumferential narrow groove 23 at one end, and reaches at least the tire ground contact end T at the other end. A plurality of outer lug grooves 44 are arranged at predetermined intervals in the tire circumferential direction. The outer lug groove 44 preferably extends beyond the tire ground contact end T to the tread end. Thereby, the drainage of the shoulder land portion 33 is improved.

  The tread ends refer to both end portions of the 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.

  For example, in the configuration of FIG. 3, the inner lug grooves 43 and the outer lug grooves 44 are arranged in a staggered manner in the tire circumferential direction with the circumferential narrow groove 23 as the center. In other words, the inner lug grooves 43 and the outer lug grooves 44 are alternately offset in the tire circumferential direction. Moreover, the opening part of the inner side lug groove 43 with respect to the circumferential direction fine groove 23 and the opening part of the outer side lug groove 44 are in mutually different positions, and are arrange | positioned alternately at right and left in the tire circumferential direction.

  Further, as described above, the circumferential narrow groove 23 has a bent shape extending in a zigzag shape in the tire circumferential direction. The inner lug groove 43 and the outer lug groove 44 are connected to the bending point of the circumferential narrow groove 23 from the convex side. Thereby, the edge part by the side of the circumferential direction fine groove 23 of the inner side block 331 and the outer side block 332 becomes convex shape, and the rigidity of the inner side block 331 and the outer side block 332 is improved.

  In FIG. 3, the groove width W2 of the circumferential narrow groove 23, the groove width W3 of the inner lug groove 43, and the groove width W4 of the outer lug groove 44 are 0.10 ≦ W2 / W3 ≦ 0.50 and 0. It is preferable to have a relationship of 10 ≦ W2 / W4 ≦ 0.50.

  The groove width W4 of the outer lug groove 44 is measured as the maximum value of the groove width in the tire contact surface.

  In FIG. 4, the groove depth H3 of the inner lug groove 43 and the groove depth H4 of the outer lug groove 44 and the groove depth H1 of the outermost circumferential main groove 22 are 0.30 ≦ H3 / H1 ≦ 0. .60 and 0.30 ≦ H4 / H1 ≦ 0.60, preferably 0.40 ≦ H3 / H1 ≦ 0.50 and 0.40 ≦ H4 / H1 ≦ 0.50 Is more preferable. Further, the groove depth H3 of the inner lug groove 43 and the groove depth H4 of the outer lug groove 44 and the groove depth H2 of the circumferential narrow groove 23 have a relationship of H3 <H2 and H4 <H2. . Therefore, the inner lug groove 43 and the outer lug groove 44 are shallower than the outermost circumferential main groove 22 and the circumferential narrow groove 23. Thereby, the groove depths H3 and H4 of the lug grooves 43 and 44 of the shoulder land portion 33 are optimized.

  The plurality of inner blocks 331 are divided into a circumferential main groove 22, a circumferential narrow groove 23, and a plurality of inner lug grooves 43 (see FIGS. 2 and 3). These inner blocks 331 are arranged in a row in the tire circumferential direction in a region between the circumferential main groove 22 and the circumferential narrow groove 23.

  The plurality of outer blocks 332 are divided into a circumferential narrow groove 23, a tire ground contact end T, and a plurality of outer lug grooves 44 (see FIGS. 2 and 3). These outer blocks 332 are arranged in a row in the tire circumferential direction in a region between the circumferential narrow groove 23 and the tire ground contact edge T.

  As shown in FIG. 2, the inner block 331 and the outer block 332 are arranged in a staggered manner in the tire circumferential direction with the circumferential narrow groove 23 as the center. That is, as described above, the inner lug groove 43 and the outer lug groove 44 are offset in the tire circumferential direction and are alternately connected to the circumferential narrow groove 23 on the left and right sides. 332 are alternately arranged on the left and right sides while shifting the position in the tire circumferential direction around the circumferential narrow groove 23. Therefore, the shoulder land portion 33 includes two rows of blocks including the inner block 331 and the outer block 332. In such a configuration, the circumferential narrow groove 23 has a bent shape, and the circumferential narrow groove 23 is closed by the ground external force, whereby the inner block 331 and the outer block 332 are engaged with each other in the tire circumferential direction. Thereby, the rigidity in the tire circumferential direction of the shoulder land portion 33 at the time of tire contact is ensured.

  Moreover, as shown in FIG. 3, the inner block 331 and the outer block 332 have a tread surface that is continuous in the tire circumferential direction. That is, the inner block 331 and the outer block 332 are not provided with narrow grooves or sipes penetrating the blocks 331 and 332 and are not divided in the tire circumferential direction. Thereby, the rigidity in the tire circumferential direction of the blocks 331 and 332 is ensured, and the collapse of the block at the time of tire contact is suppressed.

  In particular, in the configuration of FIG. 3, the edge portion on the circumferential narrow groove 23 side of the inner block 331 and the edge portion on the circumferential narrow groove 23 side of the outer block 332 are respectively continuous in the tire circumferential direction. . In such a configuration, the inner block 331 and the outer block 332 are compared when the circumferential narrow groove 23 is closed at the time of tire contact, as compared with a configuration (not shown) in which the narrow grooves and sipes are opened in the circumferential narrow groove 23. The meshing force increases. Thereby, the fall of the block at the time of tire grounding is suppressed effectively.

  Moreover, as shown in FIG. 3, the edge part by the side of the circumferential direction main groove 22 of the inner side block 331 has a step shape which has an amplitude in a tire width direction. Thereby, the traction component of the shoulder land portion 33 is increased, and the performance on ice and the performance on snow of the tire are enhanced.

  For example, in the configuration of FIG. 3, the edge portion on the circumferential main groove 22 side of the inner block 331 has a step shape having two steps (reference numerals omitted). Further, these steps have a linear shape substantially parallel to the tire circumferential direction on the block tread surface, and are arranged offset from each other in the tire width direction. Further, the steps of the edge portions of the inner blocks 331 and 331 adjacent in the tire circumferential direction are arranged offset in the tire width direction with the inner lug groove 43 interposed therebetween. Thereby, the edge part by the side of the circumferential direction main groove 22 of the shoulder land part 33 has the step shape extended in a tire circumferential direction, changing to a step shape in a tire width direction.

  In FIG. 3, the minimum width W1_min of the inner block 331 based on the step of the edge portion having the step shape, and the distance D1 from the measurement point on the circumferential main groove 22 side of the minimum width W1_min to the tire ground contact end T However, it is preferable to have a relationship of 0.40 ≦ W1_min / D1 ≦ 0.60. Thereby, the width | variety of the inner side block 331 is optimized.

  The minimum width W1_min of the inner block 331 is the minimum value of the distance in the tire width direction of the inner block 331 with reference to the straight portion (step) of the edge portion on the block tread surface. It is applied and measured as a no-load condition.

  The distance D1 is the minimum value of the ground contact width of the shoulder land portion 33, and is measured as a no-load state while applying a specified internal pressure by mounting a tire on a specified rim.

  In the configuration of FIG. 3, the step-shaped step amount D2 of the inner block 331 is set to about 2 [mm].

  Moreover, as shown in FIG. 3, it is preferable that the inner block 331 has the notch part 6 in the step-shaped step part. Thereby, the slip amount of the edge part of the block 331 is equalized. For example, in the configuration of FIG. 3, the edge portion on the circumferential main groove 22 side of the inner block 331 has a step shape having two steps, and the connecting portion (step portion) of these steps extends in the tire width direction. One existing notch 6 is formed.

  Further, in FIG. 3, the width D3 of the notch 6 and the minimum width W1_min of the inner block 331 on the basis of the step of the edge portion having the step shape are 0.05 ≦ D3 / W1_min ≦ 0.25. Cost. Thereby, the function of a notch part is ensured and the rigidity of the inner block 331 is ensured.

[Sipe]
In the configuration of FIG. 3, the inner block 331 and the outer block 332 each have a plurality of sipes 5. Further, these sipes 5 have a zigzag shape extending in the tire width direction, and are arranged at predetermined intervals in the tire circumferential direction. As a result, the edge components of the blocks 331 and 332 are increased, and the traction performance as a studless tire is enhanced.

  Moreover, as shown in FIG. 3, the sipe 5 of the inner block 331 and the outer block 332 has a semi-closed structure. Specifically, the sipe 5 of the inner block 331 terminates in the inner block 331 at one end, extends outward in the tire width direction, and forms the outermost circumferential main groove 22 at the other end. It is open. For this reason, the edge part by the side of the circumferential direction fine groove 23 of the inner side block 331 has a structure continuous in a tire circumferential direction, without being divided | segmented into the sipe 5. As shown in FIG. Further, the sipe 5 of the outer block 332 terminates in the outer block 332 at one end, extends outward in the tire width direction, and terminates at the tire ground contact end T. For this reason, it has the structure where the edge part by the side of the circumferential direction fine groove 23 of the outer side block 332 continues in the tire circumferential direction, without being divided | segmented into the sipe 5. FIG. Thereby, the rigidity of the tire circumferential direction of the blocks 331 and 332 is improved.

  Sipe refers to a cut having a sipe width of less than 1.0 [mm].

  The sipe 5 may be a two-dimensional sipe or a three-dimensional sipe. For example, in the configuration of FIG. 3, the sipes 5 of the shoulder land portion 33 are all three-dimensional sipes.

  The two-dimensional sipe is a sipe having a straight sipe wall surface in a cross-sectional view (a cross-sectional view including a sipe width direction and a sipe depth direction) with the sipe length direction as a normal direction. The two-dimensional sipe may have a straight shape on the tread surface, a zigzag shape, a wave shape, or an arc shape.

  The three-dimensional sipe is a sipe having a sipe wall surface that is bent in the sipe width direction in a cross-sectional view in which the sipe length direction is a normal direction. Compared to the two-dimensional sipe, the three-dimensional sipe has a strong meshing force between the opposing sipe wall surfaces, so that the collapse of the block at the time of tire contact is effectively suppressed. The three-dimensional sipe may have a straight shape on the tread surface, a zigzag shape, a wave shape, or an arc shape. Examples of such a three-dimensional sipe include the following (see FIGS. 5 and 6).

  5 and 6 are explanatory diagrams illustrating an example of a three-dimensional sipe. These figures show the sipe wall surface of the three-dimensional sipe.

  In the three-dimensional sipe 5 of FIG. 5, the sipe wall surface has a structure in which a triangular pyramid and an inverted triangular pyramid are connected in the sipe length direction. In other words, the sipe wall surface has a zigzag shape on the tread surface side and a zigzag shape on the bottom side that are shifted in pitch in the tire width direction, and unevenness that faces each other between the zigzag shapes on the tread surface side and the bottom side. Have Further, the sipe wall surface is an unevenness when viewed in the tire rotation direction among these unevennesses, between the convex bending point on the tread surface side and the concave bending point on the bottom side, the concave bending point on the tread surface side and the bottom side Between the convex bend points of the tread surface and the convex bend points on the tread surface side, and adjacent convex bend points that are adjacent to each other with ridge lines, and the ridge lines between the ridge lines in order in the tire width direction. It is formed by connecting in a plane. In addition, one sipe wall surface has an uneven surface in which convex triangular pyramids and inverted triangular pyramids are arranged alternately in the tire width direction, and the other sipe wall surface alternates between concave triangular pyramids and inverted triangular pyramids. Have uneven surfaces arranged in the tire width direction. And the sipe wall surface has the uneven | corrugated surface arrange | positioned at least at the outermost both ends of the sipe toward the outside of the block. As such a three-dimensional sipe, for example, a technique described in Japanese Patent No. 3894743 is known.

  Further, in the three-dimensional sipe 5 of FIG. 6, the sipe wall surface has a structure in which a plurality of prisms having a block shape are connected in the sipe depth direction and the sipe length direction while being inclined with respect to the sipe depth direction. In other words, the sipe wall surface has a zigzag shape on the tread surface. Further, the sipe wall surface has a bent portion that is bent in the tire circumferential direction at two or more locations in the tire radial direction inside the block and continues in the tire width direction, and has an amplitude in the tire radial direction at the bent portion. It has a zigzag shape. In addition, while the sipe wall surface makes the tire circumferential amplitude constant, the inclination angle in the tire circumferential direction with respect to the normal direction of the tread surface is made smaller at the sipe bottom side part than the tread surface side part and bent. The amplitude of the tire in the tire radial direction is made larger at the sipe bottom side than at the tread surface side. As such a three-dimensional sipe, for example, a technique described in Japanese Patent No. 4316452 is known.

[Center land]
As shown in FIG. 2, in the pneumatic tire 1, the center land portions 31 and 32 include a plurality of lug grooves 41 and 42. The lug grooves 41 and 42 extend in the tire width direction, pass through the center land portions 31 and 32, and the left and right circumferential main grooves 21 and 22; Each has an opening. A plurality of lug grooves 41 and 42 are arranged at predetermined intervals in the tire circumferential direction. Thereby, each center land part 31 and 32 is divided | segmented into the tire circumferential direction by the several lug grooves 41 and 42, and becomes a block row | line | column.

  Further, as shown in FIG. 2, the edge portion of the block of the center land portion 32 partitioned by the outermost circumferential main groove 22 has a step shape corresponding to the edge portion of the inner block 331 of the shoulder land portion 33. Yes. Specifically, the edge part on the outermost circumferential direction main groove 22 side of the block of the center land part 32 has a step shape having two steps. Further, these steps have a linear shape substantially parallel to the tire circumferential direction on the block tread surface, and are arranged offset from each other in the tire width direction. Further, the phase of the step shape is synchronized so that the edge portion of the block of the center land portion 32 and the edge portion of the inner block 331 of the shoulder land portion 33 have a constant groove width of the outermost circumferential main groove 22. Are arranged. Accordingly, the outermost circumferential main groove 22 extends in the tire circumferential direction with a constant groove width while being bent in a step shape in the tire width direction.

[effect]
As described above, the pneumatic tire 1 includes a plurality of circumferential main grooves 21 and 22 that extend in the tire circumferential direction, and a plurality of land portions 31 that are partitioned by the circumferential main grooves 21 and 22. To 33 (see FIG. 2). Further, the shoulder land portion 33 has one circumferential narrow groove 23 extending in the tire circumferential direction and a plurality of openings extending inward in the tire width direction from the circumferential narrow groove 23 to the outermost circumferential main groove 22. Inner lug grooves 43, a plurality of outer lug grooves 44 extending outward in the tire width direction from the circumferential narrow grooves 23 to the tire contact end, the outermost circumferential main groove 22, the circumferential narrow grooves 23, and the plural A plurality of inner blocks 331 defined by inner lug grooves 43 and a plurality of outer blocks 332 defined by circumferential narrow grooves 23, tire ground contact ends T and a plurality of outer lug grooves 44 are provided (see FIG. 3). ). Further, the inner block 331 and the outer block 332 are arranged in a staggered manner in the tire circumferential direction with the circumferential narrow groove 23 as the center.

  In such a configuration, the shoulder land portion 33 includes the circumferential narrow groove 23, and thus there is an advantage that the performance on the snow and ice of the tire is improved.

  On the other hand, in the configuration including the circumferential narrow groove 23, there is a problem that the block rigidity of the shoulder land portion 33 is reduced, and heel and toe wear is likely to occur in the block.

  In this regard, in the above configuration, the inner block 331 and the outer block 332 are arranged in a zigzag manner in the tire circumferential direction around the circumferential narrow groove 23, so that the circumferential narrow groove 23 is closed when the tire is in contact with the ground. As a result, the inner block 331 and the outer block 332 continuously mesh in the tire circumferential direction. Then, the rigidity in the tire circumferential direction of the shoulder land portion 33 is ensured, and the collapse of the blocks 331 and 332 at the time of tire contact is suppressed. Accordingly, there is an advantage that uneven wear (particularly heel and toe wear) of the blocks 331 and 332 is suppressed.

  Moreover, in this pneumatic tire 1, the edge part by the side of the outermost circumferential direction main groove 22 of the inner side block 331 has a step shape which has an amplitude in a tire width direction (refer FIG. 3). Thereby, the traction component of the shoulder land portion 33 is increased, and there is an advantage that the performance on the ice and the performance on the snow of the tire are improved.

  Further, in the pneumatic tire 1, the minimum width W1_min of the inner block 331 based on the step of the step shape, and the distance D1 from the measurement point on the outermost circumferential main groove 22 side of the minimum width W1_min to the tire ground contact end T However, it has a relationship of 0.40 <= W1_min / D1 <= 0.60 (refer FIG. 3). In such a configuration, since the circumferential narrow groove 23 is disposed substantially at the center of the shoulder land portion 33, the rigidity of the left and right blocks 331 and 332 of the circumferential narrow groove 23 is made uniform. Thereby, there exists an advantage by which the partial wear of the blocks 331 and 332 is suppressed.

  Moreover, in this pneumatic tire 1, the inner block 331 has the notch part 6 in the step-shaped step part of an edge part (refer FIG. 3). Thereby, there is an advantage that the slip amount of the edge portion of the block 331 is made uniform, and uneven wear of the block 331 is suppressed.

  In the pneumatic tire 1, the groove width W2 of the circumferential narrow groove 23, the groove width W3 of the inner lug groove 43, and the groove width W4 of the outer lug groove 44 are 0.10 ≦ W2 / W3 ≦ 0. 50 and 0.10 ≦ W2 / W4 ≦ 0.50 (see FIG. 3). Thereby, there exists an advantage by which the groove width W2 of the circumferential direction fine groove 23 is optimized. That is, when the lower limit of the groove width W2 of the circumferential narrow groove 23 is within the above range, the effect of improving the performance on ice and snow by the circumferential narrow groove 23 is appropriately ensured. In addition, since the upper limit of the groove width W2 of the circumferential narrow groove 23 is within the above range, the circumferential narrow groove 23 is properly closed when the tire is in contact with the ground, and the meshing forces of the left and right blocks 331 and 332 are appropriately Secured. Thereby, falling of the blocks 331 and 332 is suppressed, and uneven wear of the block 331 is suppressed.

  Further, in the pneumatic tire 1, the edge portion on the circumferential narrow groove 23 side of the inner block 331 and the edge portion on the circumferential narrow groove 23 side of the outer block 332 are respectively continuous in the tire circumferential direction (see FIG. 3). . In such a configuration, when the circumferential narrow groove 23 is closed at the time of tire contact, the inner block 331 and the outer block 332 are compared with a configuration in which narrow grooves and sipes are opened at the edge of the block (not shown). The meshing force increases. Thereby, there exists an advantage by which the fall of the block at the time of tire contact is suppressed effectively.

  In the pneumatic tire 1, the inner block 331 terminates in the inner block 331 at one end, extends outward in the tire width direction, and forms the outermost circumferential main groove 22 at the other end. It has the sipe 5 which opens (refer FIG. 3). Thereby, there is an advantage that the edge component of the block 331 increases and the performance of the tire on snow and ice is improved. Further, since the sipe 5 does not penetrate the block 331, the meshing force between the inner block 331 and the outer block 332 when the circumferential narrow groove 23 is blocked increases, and the collapse of the block at the time of tire contact is effective. Has the advantage of being suppressed.

  Further, in this pneumatic tire 1, the outer block 332 has a sipe 5 that terminates in the outer block 332 at one end and extends outward in the tire width direction to reach the tire ground contact end T (FIG. 3). reference). Thereby, there is an advantage that the edge component of the block 332 increases and the performance of the tire on snow and ice is improved. Further, since the sipe 5 does not penetrate the block 332, the meshing force between the inner block 331 and the outer block 332 when the circumferential narrow groove 23 is blocked increases, and the collapse of the block at the time of tire contact is effective. Has the advantage of being suppressed.

  In the pneumatic tire 1, the groove depth H2 of the circumferential narrow groove 23 and the groove depth H1 of the outermost circumferential main groove 22 have a relationship of 0.40 ≦ H2 / H1 ≦ 0.70. (See FIG. 4). Thereby, there exists an advantage by which the groove depth H2 of the circumferential direction fine groove 23 is optimized. That is, by satisfying 0.40 ≦ H2 / H1, the groove depth H2 of the circumferential narrow groove 23 is ensured, and the effect of improving the performance on ice and snow by the circumferential narrow groove 23 is appropriately obtained. Moreover, by being H2 / H1 <= 0.70, the rigidity of the shoulder land part 33 is ensured appropriately, and the partial wear of the blocks 331 and 332 is suppressed.

  Further, in the pneumatic tire 1, the groove depth H3 of the inner lug groove 43 and the groove depth H4 of the outer lug groove 44 and the groove depth H1 of the outermost circumferential main groove 22 are 0.30 ≦ H3 / H1 ≦ 0.60 and 0.30 ≦ H4 / H1 ≦ 0.60 (see FIG. 4). Thereby, there exists an advantage by which groove depth H3, H4 of the lug grooves 43 and 44 is optimized. That is, by satisfying 0.30 ≦ H3 / H1 and 0.30 ≦ H4 / H1, the groove depths H3 and H4 of the lug grooves 43 and 44 are ensured, and the performance of the tire on snow and ice is ensured. In addition, since H3 / H1 ≦ 0.60 and H4 / H1 ≦ 0.60, the rigidity of the shoulder land portion 33 is ensured appropriately, and uneven wear of the blocks 331 and 332 is suppressed.

  In the pneumatic tire 1, the circumferential narrow groove 23 has a bent shape having a plurality of bending points (see FIG. 3). In such a configuration, the circumferential narrow groove 23 is closed when the tire is in contact with the ground, and the opposing groove walls of the circumferential narrow groove 23 mesh with each other in the tire circumferential direction. As a result, the blocks 331 and 332 are prevented from falling due to a grounding external force, and there is an advantage that uneven wear of the shoulder land portion 33 is effectively suppressed.

  In the pneumatic tire 1, the inner lug groove 43 and the outer lug groove 44 communicate with the bending point of the circumferential narrow groove 23 (see FIG. 3). Thereby, the fall of the blocks 331 and 332 at the time of tire contact is suppressed, and there is an advantage that uneven wear of the land portion 33 is effectively suppressed.

  Further, in the pneumatic tire 1, the bending angle α of the bent portion of the circumferential narrow groove 23 is in the range of 1 [deg] ≦ α ≦ 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] ≦ α, the engagement force of the groove wall of the circumferential narrow groove 23 at the time of tire contact is formed, and the action of suppressing the collapse of the blocks 331 and 332 is obtained. Further, by satisfying α ≦ 30 [deg], the snow drainage property in the circumferential narrow groove 23 is ensured.

  Moreover, in this pneumatic tire 1, the groove width W2 of the circumferential narrow groove 23 is in the range of 1.0 [mm] ≦ W2 ≦ 3.0 [mm] (see FIG. 3). Thereby, there exists an advantage by which the groove width W2 of the circumferential direction fine groove 23 is optimized. That is, when the lower limit of the groove width W2 of the circumferential narrow groove 23 is within the above range, the effect of improving the performance on ice and snow by the circumferential narrow groove 23 is appropriately ensured. In addition, since the upper limit of the groove width W2 of the circumferential narrow groove 23 is within the above range, the circumferential narrow groove 23 is properly closed when the tire is in contact with the ground, and the meshing forces of the left and right blocks 331 and 332 are appropriately Secured. Thereby, falling of the blocks 331 and 332 is suppressed, and uneven wear of the block 331 is suppressed.

  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, the function of the circumferential narrow groove 23 can be appropriately ensured regardless of the loading condition of the vehicle.

  In the pneumatic tire 1, the tread rubber 15 has a rubber hardness of 50 or more and 75 or less. Thereby, there exists an advantage by which the rigidity of a tread part is ensured appropriately.

[Applicable to]
The pneumatic tire 1 is applied to a low flat tire having a flat rate of 70 [%] or less, and particularly a small size having a maximum air pressure defined by JATMA within a range of 350 [kPa] to 600 [kPa]. It is preferable to apply truck tires. Since light truck tires are mainly used for local travel, heel and toe wear is likely to occur due to repeated stop and go. Therefore, there is an advantage that the effect of suppressing heel-and-toe wear can be remarkably obtained by making such a small truck tire applicable.

  FIG. 7 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, a plurality of different test tires were evaluated for anti-heel and toe wear performance. In this performance test, a small truck tire having a tire size of 205 / 85R16 117 / 115L is assembled to an applicable rim defined by JATMA, and the highest tire pressure and maximum load specified by JATMA are applied to the test tire.

  In addition, test tires are mounted on all wheels of a 3-ton truck, which is a test vehicle, and the test vehicle runs on a paved road of 50,000 [km] at an average speed of 60 [km / h]. Uneven wear generated on the 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.

  The test tires of Examples 1 to 12 have the configurations described in FIGS. Further, the distance L from the tire equatorial plane CL to the tire ground contact edge T is L = 80 [mm], and the maximum groove depth H1 of the outermost circumferential main groove 22 is H1 = 13.5 [mm].

  In the test tire of the conventional example, in the configuration of Example 1, the shoulder land portion 33 is not provided with the circumferential narrow groove 23 and is formed of one block row. In the test tire of the comparative example, in the configuration of Example 1, the inner block 331 and the outer block 332 are not in a staggered arrangement, but in a lattice arrangement (arranged positions in the tire circumferential direction and the tire width direction).

  As shown in the test results, it can be seen that in the test tires of Examples 1 to 12, the uneven wear resistance performance, on-ice performance, and on-snow performance of the tire 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, 22: circumferential main groove, 23: circumferential narrow groove, 31, 32: center land portion, 33: shoulder land portion, 331: inner block, 332: outer block, 41, 42: lug groove 43: inner lug groove, 44: outer lug groove, 5: sipe, 6: notch

Claims (16)

A pneumatic tire comprising a plurality of circumferential main grooves extending in the tire circumferential direction and a plurality of land portions defined by the circumferential main grooves,
When the outer circumferential direction main groove on the outermost side in the tire width direction is referred to as an outermost circumferential direction main groove, and the land portion on the outer side in the tire width direction defined by the outermost circumferential direction main groove is referred to as a shoulder land portion,
The shoulder land portion is
One circumferential narrow groove extending in the tire circumferential direction;
A plurality of inner lug grooves extending inward in the tire width direction from the circumferential narrow groove and opening in the outermost circumferential main groove;
A plurality of outer lug grooves extending from the circumferential narrow grooves to the tire grounding end and extending outward in the tire width direction;
A plurality of inner blocks defined by the outermost circumferential main groove, the circumferential narrow groove, and the plurality of inner lug grooves;
The circumferential narrow groove, Bei example a plurality of outer blocks comprising partitioned into tire ground contact end and the plurality of outer lug grooves,
The inner block and the outer block are arranged in a staggered manner in the tire circumferential direction around the circumferential narrow groove ,
An edge part of the innermost block on the outermost circumferential direction main groove side has a step shape having an amplitude in the tire width direction,
The inner block has a notch in the stepped step, and
The pneumatic tire characterized in that the step-shaped stepped portion has a tread surface continuous in the tire circumferential direction . The minimum width W1_min of the inner block based on the step of the step shape and the distance D1 from the measurement point on the outermost circumferential main groove side of the minimum width W1_min to the tire ground contact edge are 0.40 ≦ W1_min / D1. The pneumatic tire according to claim 1 , having a relationship of ≦ 0.60. The groove width W2 of the circumferential narrow groove, the groove width W3 of the inner lug groove, and the groove width W4 of the outer lug groove are 0.10 ≦ W2 / W3 ≦ 0.50 and 0.10 ≦ W2 / W4. the pneumatic tire according to claim 1 or 2 having a relationship ≦ 0.50. The air according to any one of claims 1 to 3 , wherein an edge portion on the circumferential narrow groove side of the inner block and an edge portion on the circumferential narrow groove side of the outer block are respectively continuous in the tire circumferential direction. Enter tire. The inner block has a sipe that terminates in the inner block at one end, extends outward in the tire width direction, and opens into the outermost circumferential main groove at the other end. 4. The pneumatic tire according to any one of 4 above. The air according to any one of claims 1 to 5 , wherein the outer block has a sipe that terminates in the outer block at one end and extends outward in the tire width direction to reach a tire ground contact end. Enter tire. A groove depth H2 of the circumferential narrow groove, wherein the groove depth H1 of the outermost circumference direction main grooves, any one of claims 1 to 6 having a relation of 0.40 ≦ H2 / H1 ≦ 0.70 Pneumatic tire described in one. The groove depth H3 of the inner lug groove and the groove depth H4 of the outer lug groove and the groove depth H1 of the outermost circumferential main groove are 0.30 ≦ H3 / H1 ≦ 0.60 and 0.30. The pneumatic tire according to any one of claims 1 to 7 , having a relationship of ≦ H4 / H1 ≦ 0.60. The circumferential narrow groove is, the pneumatic tire according to any one of claims 1-8 having a bent shape with a plurality of bent points. The pneumatic tire according to claim 9 , wherein the inner lug groove and the outer lug groove communicate with the bending point of the circumferential narrow groove. The pneumatic tire according to claim 9 or 10 , wherein a bending angle α at the bending point of the circumferential narrow groove is in a range of 1 [deg] ≦ α ≦ 30 [deg]. The pneumatic tire according to any one of claims 1 to 11 , wherein a groove width W2 of the circumferential narrow groove is in a range of 1.0 [mm] ≤ W2 ≤ 3.0 [mm]. And 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 end, according to claim 1 to 12 having a relation of 0.70 ≦ Ls / L ≦ 0.90 The pneumatic tire according to any one of the above. The pneumatic tire according to any one of claims 1 to 13 , wherein the tread rubber has a rubber hardness of 50 to 75. The pneumatic tire according to any one of claims 1 to 14 , 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].   A plurality of semi-closed sipes in which one inner block terminates in the inner block at one end and extends outward in the tire width direction and opens into the outermost circumferential main groove at the other end And a closed sipe that terminates inside the inner block at both ends, and the closed sipe and the notch are disposed at the same position in the tire circumferential direction within the block. The pneumatic tire according to any one of 1 to 15.

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