WO2015167007A1

WO2015167007A1 - Pneumatic tire

Info

Publication number: WO2015167007A1
Application number: PCT/JP2015/063063
Authority: WO
Inventors: 英樹浜中
Original assignee: 横浜ゴム株式会社
Priority date: 2014-05-02
Filing date: 2015-05-01
Publication date: 2015-11-05
Also published as: JP2015212119A; CN106457922B; JP6032240B2; CN106457922A

Abstract

A pneumatic tire (1) is configured in such a manner that the left and right edges of blocks (5), the edges facing circumferential main grooves (21), have a stepped shape, the amplitude of which in the width direction of the tire varies. The front and rear edges of the blocks (5), the edges facing lug grooves (41), have a stepped shape, the amplitude of which in the circumferential direction of the tire varies. The blocks (5) each have sipes extending in the width direction of the tire. Eighty percent of the sipes (51) formed in each of the blocks (5) are semi-closed type sipes, each of which is open at one end to a circumferential main groove (21) and terminates at the other end within the block (5). Also, the projected length (P) of a semi-closed sipe (51) in the circumferential direction of the tire and the length (Wb), in the width direction, of an edge of a block (5), the edge facing a lug groove (41), have the relationship of 0.30 ≤ P/Wb ≤ 0.60.

Description

Pneumatic tire

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

In recent years, studless tires for small trucks employ 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 center 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. The outer circumferential main groove that is the outermost in the tire width direction is referred to as an outermost circumferential main groove, and the land portion on the inner side in the tire width direction defined by the outermost circumferential main groove is a center land portion. When at least one row of the center land portions includes a plurality of lug grooves extending in the tire width direction, and a plurality of blocks defined by the plurality of lug grooves, the circumference of the blocks The left and right edge portions on the direction main groove side have a step shape having an amplitude in the tire width direction, and the front and rear edge portions on the lug groove side of the block have a step shape having an amplitude in the tire circumferential direction. And having the plurality of blocks Each of the hooks has a plurality of sipes extending in the tire width direction, and 80% of the sipes formed in one of the blocks are opened in the circumferential main groove at one end. And a semi-closed sipe that terminates in the block at the other end, and a projection length P of the semi-closed sipe in the tire circumferential direction, and a width of an edge portion of the block on the lug groove side The direction length Wb has a relationship of 0.30 ≦ P / Wb ≦ 0.60.

In the pneumatic tire according to the present invention, the concentration P / Wb of the projected length P of the semi-closed sipe and the length Wb in the width direction of the block is optimized, so that stress concentration at the edge portion of the block is moderated appropriately. In addition, there is an advantage that the rigidity of the block is secured and uneven wear of the center land portion 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 a plan view showing a center land portion of the tread pattern shown in FIG. 4 is a cross-sectional view showing a lug groove in the center land portion shown in FIG. FIG. 5 is a cross-sectional view showing a cutout portion of the block shown in FIG. 3. FIG. 6 is a cross-sectional view showing a sipe of the block shown in FIG. FIG. 7 is an explanatory diagram illustrating an example of a three-dimensional sipe. FIG. 8 is an explanatory diagram illustrating an example of a three-dimensional sipe. FIG. 9 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 10 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 the 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 refers to JIS-A hardness according to 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. 31 to 33 and a plurality of lug grooves 41 to 44 extending in the tire width direction are provided in the tread portion. Reference numeral 23 denotes a circumferential narrow groove.

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 specified rim and filled with the specified 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.

Specified rim means “Applied rim” defined in JATMA, “Design Rim” defined in TRA, or “Measuring Rim” defined in ETRTO. The specified internal pressure means “maximum air pressure” specified by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATIONLPRESSURES” specified by TRA, or “INFLATION PRESSURES” specified by ETRTO. The specified load means the “maximum load capacity” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFUREATION PRESSURES” prescribed by TRA, or “LOAD CAPACITY” prescribed 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 to this, 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). Three or more circumferential main grooves may be arranged (not shown).

[Center land]
FIG. 3 is a plan view showing a center land portion of the tread pattern shown in FIG. The figure shows an enlarged plan view of the block 5 of the center land portion 31.

In the configuration of FIG. 2, the pneumatic tire 1 includes three rows of

center land portions

31 and 32, and these

center land portions

31 and 32 have the same structure. Therefore, in this embodiment, as an example, the center center land portion 31 will be described, and description of the other

center land portions

32, 32 will be omitted.

As described above, in the configuration of FIG. 2, the center land portion 31 (32) has a plurality of lug grooves 41 (42) extending in the tire width direction and a plurality of blocks that are partitioned by these lug grooves 41. And 5. A plurality of lug grooves 41 penetrate the center land portion 31 in the tire width direction and open to the left and right circumferential

main grooves

21 and 21 that define the center land portion 31, respectively. A plurality of lug grooves 41 are arranged at predetermined intervals in the tire circumferential direction. Thereby, the center land portion 31 is divided in the tire circumferential direction by the lug grooves 41 to form a block row composed of a plurality of blocks 5.

In the configuration of FIG. 2, all the land portions 31 to 33 each have a plurality of lug grooves 41 to 44 extending in the tire width direction, and these lug grooves 41 to 44 are land portions 31 to 33. Has an open structure that penetrates through the tire in the tire width direction. For this reason, all the land portions 31 to 33 form a block row.

However, the present invention is not limited to this, and for example, the lug groove 43 of the shoulder land portion 33 may have a semi-closed structure that terminates in the land portion 33 at one end portion (not shown). In this case, the shoulder land portion 33 is a rib continuous in the tire circumferential direction.

Here, as shown in FIG. 3, in the center land portion 31, the left and right edge portions on the circumferential

main grooves

21 and 21 side of the block 5 have a step shape having an amplitude in the tire width direction. Thereby, the traction component of the center land part 31 increases, and the performance on ice and the performance on snow of a tire improve.

For example, in the configuration of FIG. 3, the left and right edge portions on the circumferential

main grooves

21 and 21 side of the block 5 have 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 step-shaped stepped portion (not shown) is 40 [%] or more and 60 [%] or less with respect to the central portion of the block 5 (the circumferential length Lb of the edge portion on the circumferential main groove 21 side of the block 5). In the area). Further, the steps of the edge portions of the

blocks

5 and 5 adjacent in the tire circumferential direction are arranged offset in the tire width direction with the lug groove 41 interposed therebetween. Thereby, the edge part by the side of the circumferential direction main groove 21 of the center land part 31 has the step shape extended in a tire circumferential direction, changing to a step shape in a tire width direction.

In the configuration of FIG. 3, the step amount of the step shape of the block 5 (dimension code omitted) is set to about 2 [mm].

Further, as shown in FIG. 3, the front and rear edge portions on the lug groove 41 side of the block 5 have a step shape having an amplitude in the tire circumferential direction. Thereby, the traction component of the center land part 31 increases, and the performance on ice and the performance on snow of a tire improve.

For example, in the configuration of FIG. 3, the lug groove 41 extends in the tire width direction while being bent, so that the edge portion on the lug groove 41 side of the block 5 has a step shape having two steps (reference numerals omitted). ing. Also, these steps are arranged offset from each other in the groove width direction of the lug groove 41. Further, the step-shaped stepped portion 53 of the block 5 is an area of 40 [%] or more and 60 [%] or less with respect to the central portion of the block 5 (the width direction length Wb of the edge portion of the block 5 on the lug groove 41 side). ).

Further, the lug groove 41 extends while inclining at a predetermined angle in the tire width direction, so that the step-shaped step of the block 5 is inclined with respect to the tire width direction as a whole. At this time, the inclination angle of the lug groove 41 with respect to the tire width direction is preferably in the range of 1 [deg] or more and 30 [deg] or less.

The inclination angle of the lug groove 41 is measured as an angle formed by a straight line passing through the center point of the left and right openings of the lug groove 41 and the tire width direction.

Further, the circumferential length Lb of the edge portion on the circumferential main groove 21 side of the block 5 and the width direction length Wb of the edge portion on the lug groove 41 side of the block 5 are 1.15 ≦ Lb / Wb ≦ 1. .50 relationship. Thereby, the shape of the block 5 is optimized.

The circumferential length Lb of the block 5 is the distance in the tire circumferential direction of the edge portion of the block 5 facing the circumferential main groove 21, and the tire is mounted on the prescribed rim to apply the prescribed internal pressure and to be in an unloaded state. Measured. Moreover, in the structure where the edge part of the block 5 has a chamfer part or a notch part, these are excluded and the circumferential direction length Lb is measured.

The width direction length Wb of the block 5 is a distance in the tire width direction of the edge portion of the block 5 facing the lug groove 41, and is measured as an unloaded state while applying a specified internal pressure by mounting the tire on a specified rim. The Moreover, in the structure which the edge part of the block 5 has a chamfering part or a notch part, these are excluded and the width direction length Wb is measured.

In the configuration of FIG. 3, as described above, the lug groove 41 is inclined with respect to the tire width direction, so that the tread surface of the block 5 has a parallelogram shape as a whole. A chamfered portion (reference numeral omitted) is applied to the acute corner portion of the block 5. Thereby, the intensity | strength of the corner | angular part of the block 5 is ensured, the partial wear of the block 5 is suppressed, and the groove opening part of the lug groove 41 is expanded, and the drainage property is improved.

Further, the width direction length Wb of the edge portion on the lug groove 41 side of the block 5 and the tire ground contact width TW (see FIG. 2) have a relationship of 0.10 ≦ Wb / TW ≦ 0.18. Thereby, the width direction length Wb of the block 5 is optimized.

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

Also, the lug groove 41 opens with a see-through structure to the left and right circumferential

main grooves

21, 21 that define the center land portion 31. The see-through structure refers to a structure in which the other circumferential main groove 21 can be seen from one circumferential main groove 21 via the lug groove 41. Such a see-through structure improves the drainage performance and snow removal performance of the lug groove 41.

Further, the opening width Wl in the tire circumferential direction of the lug groove 41 and the circumferential length Lb of the edge portion on the circumferential main groove 21 side of the block 5 have a relationship of 0.08 ≦ Wl / Lb ≦ 0.18. Preferably, it has a relationship of 0.10 ≦ Wl / Lb ≦ 0.15. Thereby, the opening width Wl of the lug groove 41 is optimized.

The opening width Wl of the lug groove 41 is a distance in the tire circumferential direction of the opening with respect to the circumferential main groove 21 of the lug groove 41, and is measured as a no-load state while attaching the tire to the specified rim and applying the specified internal pressure. The Moreover, in the structure which the edge part of the block 5 has a chamfer part or a notch part, these are excluded and the opening width Wl is measured.

The lug groove 41 generally has a groove width of 1.0 [mm] or more. The groove width of the lug groove 41 is measured by excluding the chamfered part and the notch part at the edge part of the block 5.

FIG. 4 is a cross-sectional view showing the lug groove in the center land portion shown in FIG. This figure shows a cross-sectional view of the lug groove 41 in the groove depth direction.

As shown in FIG. 4, in the center land portion 31, the lug groove 41 has a bottom upper portion 411. The bottom upper part 411 is formed at the groove bottom of the lug groove 41 and partially raises the groove depth of the lug groove 41. Thereby, the rigidity of the block 5 is ensured and uneven wear of the block 5 is suppressed.

In addition, the groove depth DL of the lug groove 41 in the bottom upper portion 411 and the groove depth GD of the circumferential main groove 21 preferably have a relationship of 0.50 ≦ DL / GD ≦ 0.80. It is more preferable to have a relationship of 55 ≦ DL / GD ≦ 0.75. Thereby, the groove depth DL of the lug groove 41 in the bottom upper part 411 is optimized.

For example, in the configuration of FIG. 4, the bottom upper portion 411 of the lug groove 41 is formed at the center of the lug groove 41 in the groove length direction. Further, the groove depth of the lug groove 41 gradually increases from the bottom upper portion 411 toward the circumferential main groove 21, and becomes maximum at the groove opening portion with respect to the circumferential main groove 21. Thereby, the drainage property of the lug groove 41 and the snow drainage property are improved.

[Notch]
FIG. 5 is a cross-sectional view showing a cutout portion of the block shown in FIG. 3. This figure shows a sectional view of the notch 52 in the depth direction.

As shown in FIG. 3, the block 5 of the center land portion 31 has a cutout portion 52 at an edge portion on the circumferential main groove 21 side. Further, the notch 52 is formed in the stepped step portion of the block 5. Thereby, the slip amount of the edge part of the block 5 at the time of tire contact is made uniform, and the uneven wear of the block 5 is suppressed.

For example, in the configuration of FIG. 3, the block 5 of the center land portion 31 has notches 52 at the edge portions on the left and right circumferential

main grooves

21, 21 side. Further, as described above, the left and right edge portions of the block 5 each have a step shape having two steps, and the notch portions 52 are respectively disposed at the step portions of these steps.

In FIG. 3, the circumferential length Lb of the edge portion on the circumferential main groove 21 side of the block 5 and the position Mc of the notch 52 in the edge portion of the block 5 are 0.35 ≦ Mc / Lb ≦ 0. .65, preferably 0.40 ≦ Mc / Lb ≦ 0.60. Thereby, the position Mc of the notch 52 is optimized.

The position Mc of the notch 52 is measured as a distance in the tire circumferential direction between the measurement point of the circumferential length Lb of the block 5 and the center of the notch 52 in a plan view of the block 5.

5, the depth Dc of the notch 52 and the groove depth GD of the circumferential main groove 21 preferably have a relationship of 0.50 ≦ Dc / GD ≦ 0.80, It is more preferable to have a relationship of ≦ Dc / GD ≦ 0.75. Thereby, the depth Dc of the notch 52 is optimized.

The depth Dc of the notch 52 is measured as the maximum depth of the notch 52 with reference to the tread surface of the block 5.

In FIG. 3, the width direction length Wc of the notch 52 and the width direction length Wb of the edge portion on the lug groove 41 side of the block 5 have a relationship of 0.05 ≦ Wc / Wb ≦ 0.25. It is preferable to have. Thereby, the function of the notch 52 is ensured and the rigidity of the block 5 is ensured.

The width direction length Wc of the notch portion 52 is measured as a length in the tire width direction with reference to the step of the edge portion on the circumferential main groove 21 side of the step shape of the block 5.

[Sipe]
FIG. 6 is a cross-sectional view showing a sipe of the block shown in FIG. This figure shows a sectional view of the sipe 51 in the depth direction.

3, the block 5 of the center land portion 31 has a plurality of sipes 51 extending in the tire width direction. Further, an 80% sipe 51 formed in one block 5 is a semi-closed sipe (one-side opening sipe), and opens to the circumferential main groove 21 at one end and the other end. End in block 5 at. Thereby, the edge component of the block 5 increases and the traction performance as a studless tire is improved.

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

For example, in the configuration of FIG. 3, one block 5 has a plurality of semi-closed sipes 51 and a plurality of closed sipes (reference numerals omitted) that terminate inside the block 5 at both ends. Further, the ratio of the semi-closed sipe 51 in one block 5 is set to 80 [%] or more with respect to the total number of sipes. The plurality of semi-closed sipes 51 have a zigzag shape extending in the tire width direction, and are arranged at substantially uniform intervals in the tire circumferential direction. Further, the plurality of semi-closed sipes 51 are equally arranged on the left and right edge portions of the block 5. Thereby, the rigidity of the left and right edge portions of the block 5 is made uniform.

In the configuration of FIG. 3, the block 5 of the center land portion 31 does not have an open sipe that penetrates the block 5. For this reason, the tread surface of the block 5 has a structure which continues in the tire circumferential direction without being divided by sipes. Thereby, the rigidity of the block 5 is improved.

Further, the projection length P of the semi-closed sipe 51 in the tire circumferential direction and the width-direction length Wb of the edge portion on the lug groove 41 side of the block 5 have a relationship of 0.30 ≦ P / Wb ≦ 0.60. Respectively. The ratio P / Wb is preferably in the range of 0.35 ≦ P / Wb ≦ 0.55. Further, the semi-closed sipe 51 that satisfies the condition P / Wb is set to 80 [%] or more with respect to the total number of sipes in one block 5. Thereby, the projection length P of the sipe 51 is optimized.

The sipe projection length P is measured based on the sipe length on the tread surface of the block 5.

In FIG. 6, the sipe depth Ds1 of the semi-closed sipe 51 and the groove depth GD of the circumferential main groove 21 preferably have a relationship of 0.55 ≦ Ds1 / GD ≦ 0.85. It is more preferable to have a relationship of 60 ≦ Ds1 / GD ≦ 0.80. Thereby, the sipe depth Ds1 is optimized.

The sipe depth Ds1 is measured as a distance from the tread surface of the block 5 to the maximum depth position of the sipe 51.

Further, as shown in FIG. 6, the semi-closed sipe 51 has a bottom upper portion 511 at an opening portion with respect to the circumferential main groove 21. Thereby, the stress concentration at the edge portion on the circumferential main groove 21 side of the block 5 is alleviated, the collapse of the block 5 at the time of tire contact is suppressed, and the uneven wear of the block 5 is suppressed.

At this time, the sipe depth Ds2 in the bottom upper portion 511 and the groove depth GD of the circumferential main groove 21 preferably have a relationship of 0.05 ≦ Ds2 / GD ≦ 0.25, and 0.10 ≦ Ds2 It is more preferable to have a relationship of /GD≦0.20. Thereby, the sipe depth Ds2 in the bottom upper part 511 is optimized.

The sipe depth Ds2 at the bottom upper part 511 is measured with reference to the tread surface of the block 5.

In FIG. 6, the arrangement length Ws of the bottom upper portion 511 and the width direction length Wb of the edge portion on the lug groove 41 side of the block 5 have a relationship of 0.05 ≦ Ws / Wb ≦ 0.20. It is preferable. Thereby, the arrangement | positioning area | region of the bottom upper part 511 is optimized.

The arrangement length Ws of the bottom upper part 511 is measured as the length in the tire width direction of the bottom upper part 511 in the plan view of the block 5.

The sipe may be a two-dimensional sipe or a three-dimensional sipe. For example, in the configuration of FIG. 3, all the sipes of the center land portion 31 are three-dimensional sipes.

A two-dimensional sipe is a sipe having a sipe wall surface that is linear in a sectional view (a 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.

A three-dimensional sipe is a sipe having a sipe wall surface that is bent in the sipe width direction in a cross-sectional view with the sipe length direction as the 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. 7 and 8).

7 and 8 are explanatory diagrams showing an example of a three-dimensional sipe. These figures show the sipe wall surface of the three-dimensional sipe.

7, 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 outer side of a 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 51 of FIG. 8, 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.

[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, at least one row of the center land portions 31 includes a plurality of lug grooves 41 extending in the tire width direction and a plurality of blocks 5 defined by the lug grooves 41 (see FIG. 3). Further, the left and right edge portions on the circumferential main groove 21 side of the block 5 have a step shape having an amplitude in the tire width direction. Further, the front and rear edge portions on the lug groove 41 side of the block 5 have a step shape having an amplitude in the tire circumferential direction. The plurality of blocks 5 each have a plurality of sipes extending in the tire width direction. In addition, an 80 [%] sipe 51 formed in one block 5 is a semi-closed sipe that opens into the circumferential main groove 21 at one end and terminates in the block 5 at the other end. is there. Further, the projection length P of the semi-closed sipe 51 in the tire circumferential direction and the width-direction length Wb of the edge portion on the lug groove 41 side of the block 5 have a relationship of 0.30 ≦ P / Wb ≦ 0.60. Respectively.

In such a configuration, the circumferential main groove 21 side of the block 5 and the edge portion of the lug groove 41 have step shapes, so that the edge action of the block 5 is improved and the performance of the tire on ice and snow is improved. Further, since the 80% sipe 51 formed in one block 5 is a semi-closed sipe, stress concentration at the edge portion of the block 5 is relaxed while securing the rigidity of the block 5. Thereby, the collapse of the block 5 at the time of tire contact is suppressed, and there is an advantage that the uneven wear resistance performance of the tire (particularly, the center wear resistance performance of the tire mounted on the drive shaft of the vehicle) is improved.

Further, there is an advantage that the ratio P / Wb between the projection length P of the semi-closed sipe 51 and the width direction length Wb of the block 5 is optimized. That is, by satisfying 0.30 ≦ P / Wb, the projection length P of the semi-closed sipe 51 is secured, and the stress concentration at the edge portion of the block 5 is moderated appropriately. Further, by satisfying P / Wb ≦ 0.60, the rigidity of the block 5 is ensured, and the collapse of the block 5 at the time of tire contact is suppressed.

In the pneumatic tire 1, the sipe depth Ds1 of the semi-closed sipe 51 and the groove depth GD of the circumferential main groove 21 have a relationship of 0.55 ≦ Ds1 / GD ≦ 0.85 (see FIG. 6). Thereby, there exists an advantage by which the sipe depth Ds1 is optimized. That is, by satisfying 0.55 ≦ Ds1 / GD, the sipe depth Ds1 is ensured, and the action of the sipe 51 is appropriately obtained. Further, since Ds1 / GD ≦ 0.85, the rigidity of the block 5 is ensured, and the collapse of the block 5 at the time of tire contact is suppressed.

Moreover, in this pneumatic tire 1, the semi-closed sipe 51 has the bottom upper part 511 in the opening part with respect to the circumferential direction main groove 21 (refer FIG. 6). Moreover, the sipe depth Ds2 in the bottom upper part 511 and the groove depth GD of the circumferential main groove 21 have a relationship of 0.05 ≦ Ds2 / GD ≦ 0.25. In such a configuration, the stress concentration at the edge portion on the circumferential main groove 21 side of the block 5 is alleviated, and the collapse of the block 5 at the time of tire contact is suppressed. Moreover, there exists an advantage by which the sipe depth Ds2 in the bottom upper part 511 is optimized. That is, by satisfying 0.05 ≦ Ds2 / GD, the sipe depth Ds2 is ensured, and the action of the sipe 51 is appropriately obtained. Further, by satisfying Ds2 / GD ≦ 0.25, the rigidity of the block 5 is ensured, and the collapse of the block 5 at the time of tire contact is suppressed.

In this pneumatic tire 1, the left and right edge portions on the circumferential main groove 21 side of the block 5 have notches 52 in the step-shaped step portions (see FIG. 3). Thereby, the slip amount of the edge part of the block 5 at the time of tire contact is equalized, and there is an advantage that uneven wear of the block 5 is suppressed.

Moreover, in this pneumatic tire 1, the circumferential length Lb of the edge portion on the circumferential main groove 21 side of the block 5 and the position Mc of the notch portion 52 in the edge portion are 0.35 ≦ Mc / Lb ≦. The relationship is 0.65 (see FIG. 3). In such a configuration, the notch portion 52 is disposed at the center of the edge portion of the block 5, so that stress concentration at the edge portion of the block 5 is effectively alleviated. Thereby, there exists an advantage by which the partial wear of the block 5 is suppressed effectively.

Further, in this pneumatic tire 1, the depth Dc of the notch 52 and the groove depth GD of the circumferential main groove 21 have a relationship of 0.50 ≦ Dc / GD ≦ 0.80 (see FIG. 5). ). Thereby, there exists an advantage by which the depth Dc of the notch part 52 is optimized. That is, by satisfying 0.50 ≦ Dc / GD, the depth Dc of the notch 52 is ensured, and the action of the notch 52 can be appropriately obtained. Further, since Dc / GD ≦ 0.80, the rigidity of the block 5 is ensured, and the collapse of the block 5 at the time of tire contact is suppressed.

Moreover, in this pneumatic tire 1, the opening width Wl of the lug groove 41 in the tire circumferential direction and the circumferential length Lb of the edge portion on the circumferential main groove 21 side of the block 5 are 0.08 ≦ Wl / Lb. ≦ 0.18 (see FIG. 3). Thereby, there exists an advantage by which the opening width Wl of the lug groove 41 is optimized. That is, by satisfying 0.08 ≦ Wl / Lb, the opening width Wl of the lug groove 41 is ensured, and the drainage performance and snow discharge performance of the lug groove 41 are ensured. In addition, since Wl / Lb ≦ 0.18, the rigidity of the block 5 in the tire circumferential direction is ensured, and the collapse of the block 5 at the time of tire contact is suppressed.

Moreover, in this pneumatic tire 1, the lug groove 41 has the bottom upper part 411 (refer FIG. 4). Further, the groove depth DL of the lug groove 41 in the bottom upper portion 411 and the groove depth GD of the circumferential main groove 21 have a relationship of 0.50 ≦ DL / GD ≦ 0.80. In such a configuration, the lug groove 41 has the bottom upper portion 411, so that the rigidity of the block 5 is ensured and the collapse of the block 5 at the time of tire contact is suppressed. Moreover, there exists an advantage by which ratio DL / GD is optimized. That is, by satisfying 0.50 ≦ DL / GD, the groove depth DL of the lug groove 41 in the bottom upper portion 411 is ensured, and the drainage performance and snow discharge performance of the lug groove 41 are ensured. Further, since DL / GD ≦ 0.80, the reinforcing action of the rigidity of the block 5 by the bottom upper portion 411 is appropriately ensured.

In this pneumatic tire 1, the step-shaped stepped portion 53 at the edge portion of the block 5 on the lug groove 41 side is 40% or more of the widthwise length Wb of the edge portion of the block 5 on the lug groove 41 side. It is in a position of 60% or less (see FIG. 3). In such a configuration, the step-shaped stepped portion 53 is arranged at the center of the edge portion of the block 5, so that stress concentration at the edge portion of the block 5 is effectively alleviated. Thereby, there exists an advantage by which the fall of the block 5 at the time of tire contact is suppressed.

In the pneumatic tire 1, the width direction length Wb (see FIG. 3) of the edge portion on the lug groove 41 side of the block 5 and the tire ground contact width TW (see FIG. 2) are 0.10 ≦ Wb / It has a relationship of TW ≦ 0.18. Thereby, there exists an advantage by which the width direction length Wb of the block 5 is optimized. That is, by satisfying 0.10 ≦ Wb / TW, there is an advantage that the rigidity of the block 5 in the tire width direction is ensured and the collapse of the block 5 at the time of tire contact is suppressed. Further, by satisfying Wb / TW ≦ 0.18, the groove width of the circumferential main groove 21 can be ensured appropriately, and the drainage and snow drainage of the circumferential main groove 21 can be secured.

In this pneumatic tire 1, the circumferential length Lb of the edge portion of the block 5 on the circumferential main groove 21 side and the widthwise length Wb of the edge portion of the block 5 on the lug groove 41 side are 1. 15 ≦ Lb / Wb ≦ 1.50 (see FIG. 3). Thereby, there exists an advantage by which the shape of the block 5 is optimized. That is, by satisfying 1.15 ≦ Lb / Wb, the circumferential length Lb of the block 5 is ensured, and the collapse of the block 5 at the time of tire contact is suppressed. Further, since Lb / Wb ≦ 1.50, the rigidity in the width direction of the block 5 is ensured, and uneven wear of the block 5 is suppressed.

Further, in the pneumatic tire 1, the semi-closed sipe 51 is a three-dimensional sipe (see FIGS. 7 and 8). Thereby, the meshing force of the sipe 51 is increased, and there is an advantage that the collapse of the block 5 at the time of tire contact is suppressed.

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. In such a low-profile tire for a small truck, the ground contact state of the tread portion is likely to change between when the load is loaded and when the load is not loaded. That is, the center area and the shoulder area of the tread portion are uniformly grounded when the load is loaded, but the ground contact area of the shoulder area is reduced when the luggage is not loaded. Then, the land part of a center area | region wears out early and there exists a subject that center wear tends to arise. Therefore, there is an advantage that the effect of suppressing uneven wear can be remarkably obtained by using such a low flat tire for a small truck.

9 and 10 are charts showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

In this performance test, an evaluation was made on the heel and toe wear resistance performance of a plurality of different test tires. In this performance test, a small truck tire having a tire size of 205 / 70R16 is assembled to an applicable rim specified by JATMA, and the highest air 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. Based on this observation result, index evaluation is performed with the conventional example 1 as a reference (100). This value is preferably as large as possible, and if it is 110 or more, it can be said that it is particularly superior to the conventional example.

The test tires of Examples 1 to 18 have the tread pattern shown in FIG. However, in Examples 1 to 10, the block 5 does not have the notch 52. The tread width TW is TW = 160 [mm], and the maximum groove depth GD of the circumferential main groove 21 is GD = 13.5 [mm].

In the test tires of the conventional examples 1 to 5, the shape of the edge portion of the block of the center land portion 31 and the sipe structure are different from the configuration of the first embodiment. However, the total number of sipes and the sipes density are the same as those in the first embodiment.

As shown in the test results, it can be seen that in the test tires of Examples 1 to 18, the uneven wear resistance performance of the tire is improved.

1: Pneumatic tire, 5: Block, 11: Bead core, 12: Bead filler, 13: Carcass layer, 14: Belt layer, 141, 142: Cross belt, 143: Belt cover, 15: Tread rubber, 16: Side wall Rubber, 17: Rim cushion rubber, 21, 22: Circumferential main groove, 31, 32: Center land portion, 33: Shoulder land portion, 41-44: Lug groove, 411: Top bottom, 51: Sipe, 511: Bottom Upper part, 52: Notch part, 53: Step part

Claims

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 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 inner side in the tire width direction defined by the outermost circumferential main groove is referred to as a center land portion.
At least one row of the center land portions includes a plurality of lug grooves extending in the tire width direction, and a plurality of blocks defined by the plurality of lug grooves,
The left and right edge portions on the circumferential main groove side of the block have a step shape having an amplitude in the tire width direction,
The front and rear edge portions on the lug groove side of the block have a step shape having an amplitude in the tire circumferential direction,
The plurality of blocks each have a plurality of sipes extending in the tire width direction,
The sipe of 80 [%] formed in one of the blocks is a semi-closed sipe that opens into the circumferential main groove at one end and terminates in the block at the other end, and,
The projection length P of the semi-closed sipe in the tire circumferential direction and the width direction length Wb of the edge portion on the lug groove side of the block have a relationship of 0.30 ≦ P / Wb ≦ 0.60. A pneumatic tire characterized by that.
The pneumatic tire according to claim 1, wherein a sipe depth Ds1 of the semi-closed sipe and a groove depth GD of the circumferential main groove have a relationship of 0.55 ≦ Ds1 / GD ≦ 0.85.
The semi-closed sipe has a bottom top at an opening to the circumferential main groove; and
The pneumatic tire according to claim 1 or 2, wherein a sipe depth Ds2 at the bottom upper portion and a groove depth GD of the circumferential main groove have a relationship of 0.05≤Ds2 / GD≤0.25.
The pneumatic tire according to any one of claims 1 to 3, wherein left and right edge portions on the circumferential main groove side of the block have notches in the step-shaped stepped portion.
The circumferential length Lb of the edge portion on the circumferential main groove side of the block and the position Mc of the notch portion in the edge portion have a relationship of 0.35 ≦ Mc / Lb ≦ 0.65. 4. The pneumatic tire according to 4.
The pneumatic tire according to claim 4 or 5, wherein a depth Dc of the notch and a groove depth GD of the circumferential main groove have a relationship of 0.50 ≦ Dc / GD ≦ 0.80.
The opening width Wl in the tire circumferential direction of the lug groove and the circumferential length Lb of the edge portion on the circumferential main groove side of the block have a relationship of 0.08 ≦ Wl / Lb ≦ 0.18. Item 7. The pneumatic tire according to any one of Items 1 to 6.
The lug groove has a bottom top; and
The groove depth DL of the lug groove in the bottom upper portion and the groove depth GD of the circumferential main groove have a relationship of 0.50 ≦ DL / GD ≦ 0.80. The pneumatic tire according to one.
The step-shaped step portion at the edge portion on the lug groove side of the block is in a position of 40 [%] or more and 60 [%] or less of the width direction length Wb of the edge portion on the lug groove side of the block. The pneumatic tire according to any one of claims 1 to 8.
The width direction length Wb of the edge portion on the lug groove side of the block and the tire ground contact width TW have a relationship of 0.10 ≦ Wb / TW ≦ 0.18. Pneumatic tire described in 2.
The circumferential length Lb of the edge portion on the circumferential main groove side of the block and the width direction length Wb of the edge portion on the lug groove side of the block are 1.15 ≦ Lb / Wb ≦ 1.50. The pneumatic tire according to any one of claims 1 to 10, which has the following relationship:
The pneumatic tire according to any one of claims 1 to 11, wherein the semi-closed sipe is a three-dimensional sipe.
The pneumatic tire according to any one of claims 1 to 12, wherein the tread rubber has a rubber hardness of 50 to 75.
The pneumatic tire according to any one of claims 1 to 13, wherein the pneumatic 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].