CN113442660B

CN113442660B - Pneumatic tire

Info

Publication number: CN113442660B
Application number: CN202110224503.7A
Authority: CN
Inventors: 藤冈刚史
Original assignee: Toyo Tire Corp
Current assignee: Toyo Tire Corp
Priority date: 2020-03-26
Filing date: 2021-03-01
Publication date: 2022-11-08
Anticipated expiration: 2041-03-01
Also published as: CN113442660A; JP2021154805A; JP7422582B2

Abstract

The invention provides a pneumatic tire which pursues the improvement of the performance on ice and the suppression of the uneven wear. The tire is provided with: a plurality of main grooves extending in the tire circumferential direction; and a center land portion and a shoulder land portion, which are divided by the main groove. The shoulder land portion is disposed further toward the outer side in the tire width direction than a main groove disposed on the outermost side in the tire width direction among the plurality of main grooves. The center land portion is disposed further toward the inner side in the tire width direction than the shoulder land portions. The center land portion and the shoulder land portion are respectively provided with a sub-groove, a plurality of pattern blocks divided by the sub-groove, and a sipe. The ratio of the area of the sipes on the tread surface of the center land portion to the area of the land portion on the tread surface, that is, the sipe area ratio Ace, and the ratio of the area of the sipes on the tread surface of the shoulder land portion to the area of the land portion on the tread surface, that is, the sipe area ratio Ash, are 2% to 15%, and satisfy the relationship Ace > Ash.

Description

Pneumatic tire

Technical Field

The present invention relates to a pneumatic tire.

Background

Studless tires that ensure running performance on ice roads with a low coefficient of friction (on-ice performance) are known. For example, patent document 1 includes: a plurality of pattern blocks which are divided by the main grooves and the slits and are used as tread land parts; and sipes provided to the respective blocks. The performance on ice can be improved by the edge effect of the sipe and the water removal effect, and further, the performance on ice can be improved by the traction effect of the slit.

If the number of sipes provided increases to make the on-ice performance too high, partial wear may be caused.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2012-250610

Disclosure of Invention

The invention provides a pneumatic tire which pursues the improvement of the performance on ice and the suppression of the uneven wear.

A pneumatic tire of the present invention includes: a plurality of main grooves extending in the tire circumferential direction; and a center land portion and a shoulder land portion that are divided by the main grooves, the shoulder land portion being disposed further toward the tire width direction outer side than a main groove disposed at the tire width direction outermost side among the plurality of main grooves, the center land portion being disposed further toward the tire width direction inner side than the shoulder land portion, the center land portion and the shoulder land portion being respectively provided with a sub-groove, a plurality of blocks divided by the sub-groove, and a sipe, a sipe area ratio Ace that is a ratio of an area of the sipe on a tread surface of the center land portion to an area of a land portion on the tread surface, and a sipe area ratio Ash that is a ratio of an area of the sipe on the tread surface of the shoulder land portion to an area of the land portion on the tread surface being 2% or more and 15% or less, and satisfying a relationship of Ace > Ash.

Drawings

Fig. 1 is a development view showing an example of a tread surface of a pneumatic tire according to embodiment 1.

Fig. 2 is an enlarged expanded view showing the shoulder blocks, quarter-blocks, and center blocks of embodiment 1.

Fig. 3 is an enlarged developed view schematically showing the land area and the sipe area in embodiment 1.

Fig. 4 is a cross-sectional view showing blocks in a meridian section of the tire according to embodiment 1 and embodiment 2.

Fig. 5A is a perspective view showing a land portion in a state where no sipe is provided according to embodiment 1.

Fig. 5B is a perspective view showing a land portion in a state where sipes are provided in embodiment 1.

Fig. 6 is a development view showing an example of a tread surface of the pneumatic tire of embodiment 2.

Fig. 7 is an enlarged expanded view showing the shoulder blocks, quarter-blocks, and center blocks of embodiment 2.

Fig. 8 is an enlarged developed view schematically showing the land area and the sipe area in embodiment 2.

Fig. 9A is a perspective view showing a land portion in a state where no sipe is provided according to embodiment 2.

Fig. 9B is a perspective view showing a land portion in a state where sipes are provided in embodiment 2.

Description of the reference numerals

1 \ 8230and a tire shoulder land part; 2 8230where, the central land part; 17. 27 \ 8230and pattern blocks; 16. 26, 36, 8230, full open slit (secondary groove); 18 \ 8230and a semi-open slit (secondary groove); 51 \ 8230and a split sipe (secondary groove); 11. 22, 32 \8230a1 st slit (secondary groove); 12. 22, 32 \8230aNo. 2 slit (secondary groove); 14. 24, 34 \8230anotch (secondary groove); 15. 25, 35, 8230and cutting sipes (auxiliary grooves); 52 8230a circumferential sipe (sipe, 1 st sipe); 53 \ 8230a closed sipe (sipe, 2 nd sipe); 54 \ 8230and half-open sipes (sipe, no. 3 sipe); 61. 62\8230anda main ditch.

Detailed Description

< embodiment 1 >

Hereinafter, embodiment 1 of the present invention will be described with reference to the drawings.

Fig. 1 is a developed view of a tread surface Tr provided in a pneumatic tire PT (hereinafter, also simply referred to as a "tire PT") according to embodiment 1. The vertical direction in fig. 1 corresponds to the tire circumferential direction CD, and the horizontal direction in fig. 1 corresponds to the tire width direction WD. As shown in fig. 1, the tread pattern formed on the tread surface Tr is a block-like pattern in which a plurality of blocks partitioned by main grooves and sub grooves are arranged in the tire circumferential direction. The tire PT of the present embodiment is a heavy duty tire mounted on a truck or a bus.

On the tread surface Tr of the tire PT, 4

main grooves

61, 62 continuously extending in the tire circumferential direction CD are provided. In the present embodiment, the number of main grooves is 4, but the present invention is not limited thereto. The number of the main grooves may be 3 or more. In the present embodiment, the present invention includes: a shoulder main groove 62 located on the outermost side in the tire width direction WD; and a center main groove 61 disposed inside the shoulder main groove 62 in the tire width direction WD. The main groove is not particularly limited to this, and may be configured as follows, for example: the groove width is 3% or more of the distance (the dimension in the tire width direction WD) between the ground contact edges CE and CE. The main groove is not particularly limited to this, and may be configured as follows, for example: has a groove width of 7.0mm or more. The main groove is not particularly limited to this, and may be configured as follows, for example: continuously in the tire circumferential direction CD, the groove depth is largest in the tread surface Tr, and a TWI (tread wear indicator) indicating a wear-based use limit is provided in the groove.

In the present specification, the slit means: the groove has a width smaller than the main groove and a width larger than the sipe. The sipe refers to: a trench having a width of less than 1.5 mm. The minor groove means: grooves extending in the tire width direction WD, opening to the land end on the 1 st side in the tire width direction and the land end on the 2 nd side in the tire width direction, and dividing the land portion in the tire circumferential direction CD. The secondary groove includes a slit and a sipe.

The ground terminal CE is: the tire PT is vertically placed on a flat road surface in a state where the tire PT is assembled to a regular rim and filled with a regular internal pressure, and is applied to an outermost position in the tire width direction of a contact surface when a regular load is applied. The following sipe area ratio and sipe volume ratio are measured under a condition where the tire PT is vertically placed on a flat road surface with a regular load applied thereto in a state where the tire PT is assembled to a regular rim and filled with a regular internal pressure.

The regular rim is: in a specification system including specifications under which tires are based, according to the specifications, a rim determined for each tire is, for example, a standard rim in the case of JATMA, or a "measurement rim" in the case of TRA and ETRTO. The normal internal pressure is: in a specification system including the specification to which the tire is subjected, the air pressure determined for each tire in accordance with each specification is the highest air pressure in case of JATMA, the maximum value described in "tire load limit under various cold inflation pressures" in case of TRA, and the "inflation pressure" in case of ETRTO. Further, in the case where the tire is used for a passenger vehicle, the normal air pressure is set to 180kPa, and further, in the case where it is described as an overloaded or reinforced tire, the normal air pressure is set to 220kPa. The normal load is: in a specification system including the specification to which the tire conforms, the load specified for each tire in accordance with each specification is the maximum load capacity if JATMA, the maximum value described in the above table if TRA, or "load capacity" if ETRTO, and is 88% of the load corresponding to the internal pressure when the tire is used in a passenger vehicle.

< shoulder land part 1 >

As shown in fig. 1 and 2, the tire PT has shoulder land portions 1 extending in the tire circumferential direction CD at both ends in the tire width direction of the tread surface Tr. The shoulder land portions 1 are disposed further outward than the outermost main grooves 62 in the tire width direction WD. The shoulder land portion 1 is divided by the outermost main groove 62 and the ground contact edge CE in the tire width direction WD. The shoulder land portion 1 has a plurality of fully-opened slits 16 and a plurality of shoulder blocks 17 arranged in the tire circumferential direction CD. The shoulder land portions 1 constitute block rows. The full-open slit 16 is open to the main groove 62 and the ground edge CE, and divides the shoulder block 17 in the tire circumferential direction CD. Shoulder blocks 17 have at least 1 half-slit 18. The half slit 18 has a1 st end and a2 nd end, the 1 st end being open at any block end in the tire width direction WD, and the 2 nd end being closed in the shoulder block 17. In the present embodiment, the half slit 18 includes: a long half-open slit 18a that opens at the block end 1a on the inner side in the tire width direction WD; and a short half-open slit 18b (also referred to as a notch) that opens at the block end 1a or the ground end CE on the inner side in the tire width direction WD. The full open slit 16 is a sub-groove. As shown in fig. 1 and 2, the shoulder land portion 1 has divided sipes 51 that open into the long half-open slits 18a and the short half-open slits 18 b. The half slit 18 (long half slit 18a, short half slit 18 b) and the divided sipe 51 constitute a sub groove. The sub-grooves divide the shoulder land portion 1 into shoulder blocks 17.

< center land 2 >

The tire PT has a center land portion 2 extending in the tire circumferential direction CD at a tire width direction center portion of the tread surface Tr. The center land portion 2 is a land portion closest to the tire equator TE. The central land portion 2 is divided by a pair of

main grooves

61, 61. The center land portion 2 has: a plurality of full open slits 26, and a plurality of center blocks 27 arranged in the tire circumferential direction CD. The central land portion 2 constitutes a block row. The full-open slit 26 opens in the main groove 61, and divides the center block 27 in the tire circumferential direction CD. The center block 27 has at least 1 half-open slit 28. The half-open slit 28 has a1 st end and a2 nd end, the 1 st end being open at an arbitrary block end in the tire width direction WD, and the 2 nd end being closed inside the center block 27. The full open slit 26 is a sub-groove.

Slit of < quarter land portion 3 >

The tire PT has a quarter land portion 3 extending in the tire circumferential direction CD between the shoulder land portion 1 and the center land portion 2. The quarter land portion 3 is divided by a pair of

main grooves

61, 62. The quarter land portion 3 has a plurality of full open slits 36 and a plurality of quarter blocks 37 arrayed in the tire circumferential direction CD. The quarter land portion 3 constitutes a block array. The all-open slit 36 opens in the

main grooves

61, 62, and divides the quarter blocks 37 in the tire circumferential direction CD. The quarter-block 37 has at least 1 half-open slit 38. The half-open slit 38 has a1 st end and a2 nd end, the 1 st end being open at any block end in the tire width direction WD, and the 2 nd end being closed inside the quarter-block 37. The full open slit 36 is a sub-groove.

< sipe >

As shown in fig. 1 and 2, a plurality of sipes are formed in each of the shoulder land portion 1, the center land portion 2, and the quarter land portion 3. The sipes are formed by incisions having a width of less than 1.5 mm. Each

land portion

1, 2, 3 has a circumferential sipe 52, a closed sipe 53, and a half-open sipe 54.

The tread is a surface that contacts the road surface. As shown in fig. 1 and 2, the circumferential sipe 52 is a sipe having a wavy tread surface shape, extends in the tire circumferential direction CD at the tire width direction central portion of each of the

land portions

1, 2, 3, opens in the full-

open slits

16, 26, 36 or the half-open slit 18, and divides the

land portion

1, 2, 3 into blocks in the tire width direction WD. Therefore, in the present embodiment, the circumferential sipe 52 is a sipe having a wavy tread surface shape and is a three-dimensional sipe including a portion whose shape changes in the depth direction, from the viewpoint of suppressing the movement of the block after the division to reduce the uneven wear. However, the circumferential sipe 52 is not limited to this, and may be a two-dimensional sipe in which the shape does not change in the depth direction. As shown in fig. 2, the slit narrow-

width portions

26a and 36a are inclined with respect to the tire circumferential direction CD and the tire width direction WD. The circumferential sipes 52 opened in the slit

narrow portions

26a, 36a are inclined with respect to the tire circumferential direction CD and the tire width direction WD. The circumferential sipes 52 and the slit narrow-

width portions

26a, 36a are inclined in opposite directions with respect to the tire circumferential direction CD and the tire width direction WD. This is to form the corner portions of the blocks formed by the slit narrow-

width portions

26a, 36a and the circumferential sipe 52 not to be acute angles but to be right angles or nearly right angles to suppress uneven wear. The term "approximately perpendicular angle" as used herein means 60 degrees or more and less than 90 degrees. Specifically, as shown in fig. 2, the slit

narrow portions

26a and 36a are directed from the 1 st side CD1 in the tire circumferential direction and the 2 nd side WD2 in the tire width direction toward the 2 nd side CD2 in the tire circumferential direction and the 1 st side WD1 in the tire width direction. The circumferential sipes 52 formed in the center land portion 2 and the quarter land portion 3 extend from the 1 st side CD1 in the tire circumferential direction and the 1 st side WD1 in the tire width direction to the 2 nd side CD2 in the tire circumferential direction and the 2 nd side WD2 in the tire circumferential direction.

The closed sipe 53 is a sipe having a wavy tread surface shape, extends in the tire width direction WD, and is closed in each

land portion

1, 2, 3.

The half-open sipe 54 is a sipe having a wavy tread surface shape, and extends in the tire width direction WD at the tire circumferential direction center portion. The half-open sipe 54 has: a1 st end 54a closed within each

land portion

1, 2, 3; and a2 nd end 54b opening at the land end of each

land portion

1, 2, 3.

The closed sipe 53 and the half-open sipe 54 have a wavy tread surface shape, but the tread surface shape is not limited thereto, and may be a straight line. The closed sipe 53 and the half-open sipe 54 are two-dimensional sipes having a shape that does not change in the depth direction, but may be three-dimensional sipes having a portion having a shape that changes in the depth direction.

As shown in fig. 1 and 2, the shoulder land portion 1 is divided into 2 virtual small blocks adjacent to each other in the tire circumferential direction CD by the divided sipes 51 of the shoulder land portion 1.

As shown in fig. 1 and 2, each

land portion

2, 3 is divided into small blocks in the tire width direction WD from left to right by the circumferential sipes 52, and the small blocks are further divided into virtual blocks in the tire circumferential direction CD by the half-open sipes 54. Thus, a plurality of (4 in the center land portion 2 and the quarter land portion 3) virtual small blocks divided in the tire circumferential direction CD are formed in the 1

block

27, 37. This makes it possible to increase the traction element or the anti-skid element by a virtual small block smaller than the 1

block

27, 37, thereby improving the on-ice performance. However, since the closed sipe 53 is provided and the half-open sipe 54 is provided in the tire circumferential direction central portion of the

block

27, 37, the traction element can be increased while maintaining the rigidity balance in a plurality of (4 in the center land portion 2, the quarter land portion 3) small blocks, and the on-ice performance can be improved while suppressing the generation of uneven wear.

The tread surface shape of the circumferential sipe 52 is preferably a wave shape, but is not particularly limited thereto. The wall surfaces of the circumferential sipes 52 contact each other, so that excessive movement of the small blocks can be suppressed.

Further, as shown in fig. 1, the block closest to the ground contact edge CE divided by the circumferential sipe 52 is easily affected by a lateral force, and therefore, all sipes are only closed sipes 53.

From the viewpoint of improvement in the on-ice performance and suppression of generation of uneven wear, it is preferable that the width Wo of the divided sipe 51 and the circumferential sipe 52 is larger than the width Ws of the half-open sipe 54, and the width Ws of the half-open sipe 54 is larger than the width Wc of the closed sipe 53. Wo > Ws > Wc. By setting the width Wo of the open sipe (the divided sipe 51, the circumferential sipe 52) to be relatively large, it is possible to improve the on-ice performance while ensuring the rigidity of the land portion, as compared to the block pattern constituted by the grooves. By setting the width Wc of the closed sipe 53 to be relatively small, the movement of the block can be suppressed, and the cause of wear or uneven wear can be reduced. By setting the width of the half open sipe 54 to the intermediate width between the open sipe (the divided sipe 51, the circumferential sipe 52) and the closed sipe 53, the balance of the block rigidity and the on-ice performance can be achieved. Of course, when these points do not pose a problem, the widths of all the sipes may be made the same, and the magnitude relationship of the widths may be variously changed.

The depth of the sipe in the present specification is preferably 50% to 80% of the depth of the main groove. If the depth of the sipe is less than 50% of the depth of the main groove, the on-ice performance as a winter tire becomes insufficient. If the depth of the sipe is greater than 80% of the depth of the main groove, the rigidity of the land portion is lowered, which causes uneven wear.

< sipe area ratio >

As shown in fig. 3, the sipe area ratio Ace of the center land portion 2 and the sipe area ratio Ash of the shoulder land portion 1 are preferably 2% to 15%. This is to suppress the reduction of ice performance and the promotion of wear of the entire block.

Further, the sipe area ratio Ace of the center land portion 2 and the sipe area ratio Ash of the shoulder land portion 1 are preferably 5% to 10%.

If the sipe area ratio Ace, ash is less than 2%, the effect of the sipe to absorb the water film between the tire and the icy or snowy road surface is reduced, which causes a reduction in the on-ice performance.

If the sipe area ratio Ace, ash is greater than 15%, the block rigidity may decrease to promote wear of the block as a whole.

Since the sipe area ratio is a ratio, it may be calculated based on an area measured at 1 pitch (minimum repeating unit of the pattern) or based on an area measured over the entire circumference of the tire.

Further, the relationship Ace > Ash is preferably satisfied. Thus, since the sipe area ratio Ace of the center land portion 2 is larger than the sipe area ratio Ash of the shoulder land portion 1, the effect of absorbing water between the tread surface of the center land portion 2 and the ice and snow road having a relatively high ground contact pressure is improved, thereby enabling to improve the on-ice performance. Further, the block rigidity of the shoulder land portion 1, which is more likely to be affected by a lateral force than the center land portion 2 and to cause uneven wear, can be secured, and the occurrence of uneven wear can be suppressed. Therefore, it is possible to improve the on-ice performance and suppress the generation of uneven wear.

The sipe area ratio Ace of the center land portion 2 represents a ratio of the sipe area a22 of the center land portion 2 to the land area a21 on the tread surface. Expressed as Ace = a22/a21 in the mathematical formula. The land area a21 is an area on the tread surface of the center land portion 2 in a state where no sipe is provided, as shown by filling with a vertical line in fig. 3. The sipe area a22 is the total area of the regions filled with oblique lines in fig. 3, and is the total value of the sipe areas on the tread surface of the center land portion 2. The sipe referred to herein means all sipes of the center land portion 2. Specifically, the sipe includes a circumferential sipe 52, a closed sipe 53, and a half-open sipe 54.

The sipe area ratio Ash of the shoulder land portion 1 represents a ratio of the sipe area a12 of the shoulder land portion 1 to the land area a11 on the tread surface. Expressed in the mathematical formula as Ash = a12/a11. The block 17 is divided by the main groove 62 and the sub groove (half slit 18, split sipe 51). The land area a11 is an area on the tread surface of the shoulder land portion 1 in a state where no sipe is provided, as shown by filling with a vertical line in fig. 3. In addition, a concave portion 55 is formed in the center portion of the block 17, and the concave portion 55 is not included in the land portion area a11. The sipe area a12 is the total area of the regions filled with oblique lines in fig. 3, and is the total value of the sipe areas on the tread surface of the shoulder land portion 1. The term sipe as used herein refers to all sipes. Specifically, the sipe includes a divided sipe 51, a circumferential sipe 52, a closed sipe 53, and a half-open sipe 54.

The sipe area ratio Ame of the quarter land portion 3 (quarter block 37) is not particularly limited to this, but preferably satisfies the relationship Ace > Ame ≧ Ash. This can suppress uneven wear of the quarter land portion 3. If Ame > Ash, the quarter land portion 3 can be made to have both effects of improving on-ice performance and suppressing partial wear.

The sipe area ratio Ame of the quarter land portion 3 represents a ratio of the sipe area a32 of the quarter land portion 3 to the land portion area a31 on the tread surface. Expressed in the mathematical formula as Ame = a32/a31. The land portion area a31 is an area on the tread surface of the quarter land portion 3 in a state where no sipe is provided as shown by filling with a vertical line in fig. 3. Further, the concave portion 55 is formed in the central portion of the block 37, but the concave portion 55 is not included in the land portion area a31. The sipe area a32 is the total area of the areas filled with oblique lines in fig. 3, and is the total value of the sipe areas on the tread surface of the quarter land portion 3. The sipe referred to herein means all sipes. Specifically, the sipe includes a circumferential sipe 52, a closed sipe 53, and a half-open sipe 54.

< volume ratio of sipe >

Fig. 4 is a cross-sectional view showing the volumes of the shoulder land portion 1, the center land portion 2, and the quarter land portion 3 in the tire meridian section. Fig. 5A is a perspective view showing the shoulder land portion 1, the center land portion 2, and the quarter land portion 3 in a state where no sipe is provided. Fig. 5B is a perspective view showing the shoulder land portion 1, the center land portion 2, and the quarter land portion 3 in a state where sipes are provided. As shown in fig. 3, 4, 5A and 5B, the sipe volume ratio Vce of the center land portion 2 and the sipe volume ratio Vsh of the shoulder land portion 1 are not particularly limited thereto, but are preferably 1% or more and 12% or less. This is to suppress the reduction of ice performance and the promotion of wear of the entire block.

Further, the sipe volume ratio Vce of the center land portion 2 and the sipe volume ratio Vsh of the shoulder land portion 1 are preferably 2% to 8%.

If the sipe volume ratio Vce, vsh is less than 1%, the sipe causes a reduction in on-ice performance due to a reduction in the effect of absorbing a water film between the tire and the icy or snowy road surface.

If the sipe volume ratio Vce, vsh is greater than 12%, the block rigidity will decrease to promote wear of the block as a whole.

Further, since the sipe volume ratio is a ratio, it may be calculated based on an area measured at 1 pitch (minimum repeating unit of the pattern), or may be calculated based on an area measured over the entire circumference of the tire.

Further, although not particularly limited thereto, it is preferable that Vce > Vsh be satisfied. Accordingly, since the sipe volume ratio Vce of the center land portion 2 is set to be larger than the sipe volume ratio Vsh of the shoulder land portion 1, the water absorption effect between the tread surface of the center land portion 2 and the ice and snow road having a relatively high ground contact pressure is improved, and the on-ice performance can be improved. Further, the block rigidity of the shoulder land portion 1, which is more likely to be affected by a lateral force and to cause uneven wear than the center land portion 2, can be secured, and the occurrence of uneven wear can be suppressed. Therefore, it is possible to improve the on-ice performance and suppress the generation of uneven wear.

As shown in fig. 4, 5A and 5B, the sipe volume ratio Vce of the center land portion 2 indicates a ratio of the sipe volume V22 of the center land portion 2 to the land portion volume V21 of the tread Tr to the main groove bottom 60. Expressed in the mathematical formula as Vce = V22/V21. The land portion volume V21 is the volume of the land portion 2 in a state where no sipe is provided as shown by diagonal filling in fig. 4 and as shown in fig. 5A. The land volume V21 includes a region located further toward the tire radial direction outer side than the boundary line Li and further toward the tire radial direction inner side than the sipe or slit bottom. The sipe volume V22 is the total volume of the sipes filled by oblique lines in fig. 3, and is the total value of the volume of the sipes of the center land portion 2. The term sipe as used herein refers to all sipes. Specifically, the sipe includes a circumferential sipe 52, a closed sipe 53, and a half-open sipe 54.

As shown in fig. 4, the boundary line Li inside the tire radial direction RD for defining the land portion volumes V11, V21, V31 is constituted by a single or a plurality of circular arcs in the tire meridian section. The circular arc has a single radius of curvature through at least 3 of the major trench bottoms 60.

As shown in fig. 4, 5A and 5B, the sipe volume ratio Vsh of the shoulder land portion 1 represents a ratio of the sipe volume V12 of the shoulder land portion 1 to the land portion volume V11 from the tread Tr to the main groove bottom 60. Represented in the mathematical formula as Vsh = V12/V11. The land portion volume V11 is the volume of the land portion 2 in a state where no sipe is provided as shown by diagonal filling in fig. 4 and as shown in fig. 5A. The land volume V11 includes a region located further outward in the tire radial direction than the boundary line Li and further inward in the tire radial direction than the bottom portions of the sipes and slits. The sipe volume V12 is the total volume of the sipes filled with oblique lines in fig. 3, and is the total value of the sipe volumes of the shoulder land portion 1. The sipe referred to herein means all sipes. Specifically, the sipe includes a divided sipe 51, a circumferential sipe 52, a closed sipe 53, and a half-open sipe 54.

The sipe volume ratio Vme of the quarter land portion 3 is not particularly limited thereto, but preferably satisfies the relationship Vce > Vme ≧ Vsh. This can suppress uneven wear of the quarter land portion 3. If Vme > Vsh, the quarter land portion 3 can be made to have both effects of improving the on-ice performance and suppressing uneven wear.

As shown in fig. 4, 5A and 5B, the sipe volume ratio Vme of the quarter land portion 3 represents a ratio of the sipe volume V32 of the quarter land portion 3 to the land portion volume V31 of the tread Tr to the main groove bottom 60. Expressed in the mathematical formula as Vme = V32/V31. The land portion volume V31 is a volume of the quarter land portion 3 in a state where no sipe is provided as shown in fig. 5A and as shown by diagonal filling in fig. 4. The land volume V31 includes a region located further toward the tire radial direction outer side than the boundary line Li and further toward the tire radial direction inner side than the sipe or slit bottom. The sipe volume V32 is the total volume of the sipes filled with oblique lines in fig. 3, and is the total value of the volume of the sipes of the quarter land portion 3. The sipe referred to herein means all sipes. Specifically, the sipe includes a circumferential sipe 52, a closed sipe 53, and a half-open sipe 54.

< relationship between sipe area ratio and sipe volume ratio >

The sipe volume ratio Vce of the center land portion 2, the sipe volume ratio Vsh of the shoulder land portion 1, the sipe area ratio Ace of the center land portion 2, and the sipe area ratio Ash of the shoulder land portion 1 preferably satisfy the relationship (Vce/Vsh) > (Ace/Ash). This can improve at least one of the performance on ice and the performance of suppressing uneven wear in consideration of the ground contact pressure.

If the relationship (Vce/Vsh) > (Ace/Ash) is satisfied, at least either (1) the land portion volume of the shoulder land portions 1 is increased as compared with the area or (2) the sipe volume of the center land portion 2 is increased as compared with the area is satisfied.

In the case of (1) the shoulder land portion 1 having a land portion volume larger than the area, the sub-grooves (16, 18, 51) of the shoulder land portion 1 are relatively shallower than the sub-grooves (full-open slits 26) of the center land portion 2, and uneven wear can be suppressed.

In the case where the sipe volume of the center land portion 2 is increased as compared with the area in the above-described (2), the sipe of the center land portion 2 is relatively deeper than the sipe of the shoulder land portion 1, so that the water absorbing effect of the center land portion 2 having a high ground contact pressure can be improved, whereby the on-ice performance can be improved.

< embodiment 2 >

The embodiment 2 is different only in the tread pattern, and is the same as the embodiment 1 with respect to the ground contact edge, the sipe area ratio, the sipe volume ratio, the circumferential sipe 52, the closed sipe 53, and the half open sipe 54. The same components are denoted by the same reference numerals, and description thereof is omitted.

As shown in fig. 6, the tread pattern formed on the tread surface Tr is a pattern in the shape of a block formed by arranging a plurality of blocks partitioned by main grooves and sub grooves in the tire circumferential direction. In the present specification, the slit means a groove having a width smaller than the main groove and a width larger than the sipe. The sipes are grooves having a width of less than 1.5 mm. The sub-groove is a groove extending in the tire width direction WD, opening at a land end on the 1 st side in the tire width direction and a land end on the 2 nd side in the tire width direction, and dividing a land portion in the tire circumferential direction CD. The auxiliary groove includes a slit and a sipe.

< shoulder land part 1 >

As shown in fig. 6 and 7, the shoulder land portion 1 has a plurality of 1 st slits 11 and a plurality of 2 nd slits 12. The 1 st slit 11 is open at a land end 1a (ground end CE) of the 1 st side WD1 in the tire width direction WD, is separated from a land end 1b (main groove 62) of the 2 nd side WD2 in the tire width direction WD, and is closed within the shoulder land portion 1. The 2 nd slit 12 is open at the land end 1b (main groove 62) of the 2 nd side WD2 in the tire width direction WD, is separated from the land end 1a (ground end CE) of the 1 st side WD1 in the tire width direction WD, and is closed within the shoulder land portion 1. The 1 st slit 11 and the 2 nd slit 12 are different from each other in position in the tire circumferential direction CD, and the 1 st slit 11 and the 2 nd slit 12 are alternately arranged in the tire circumferential direction CD. The shoulder land portion 1 has a notch 14 and a divided sipe 15. The notches 14 and the divided sipes 15 are provided corresponding to the 1 st slit 11 and the 2 nd slit 12, respectively. The 1 st slit 11, the notch 14 and the divided sipe 15 constitute a sub-groove, and the 2 nd slit 12, the notch 14 and the divided sipe 15 constitute a sub-groove. The sub-groove divides the shoulder land portion 1 in the tire circumferential direction CD, thereby dividing the shoulder land portion 1 into shoulder blocks 17. The notch 14 is a kind of slit, but has a shorter length in the tire width direction WD than the 1 st slit 11 and the 2 nd slit 12.

< center land 2 >

As shown in fig. 6 and 7, the center land portion 2 has a plurality of 1 st slits 21 and a plurality of 2 nd slits 22. The 1 st slit 21 is open at the land end 2a (main groove 61) on the 1 st side WD1 in the tire width direction WD, is separated from the land end 2b (main groove 61) on the 2 nd side WD2 in the tire width direction WD, and is closed within the center land portion 2. The 2 nd slit 22 is open at the land end 2b (main groove 61) of the 2 nd side WD2 in the tire width direction WD, is separated from the land end 2a (main groove 61) of the 1 st side WD1 in the tire width direction WD, and is closed within the center land portion 2. The 1 st slit 21 and the 2 nd slit 22 are different from each other in position in the tire circumferential direction CD, and the 1 st slit 21 and the 2 nd slit 22 are alternately arranged in the tire circumferential direction CD. The central land portion 2 has a notch 24 and a divided sipe 25. The notches 24 and the divided sipes 25 are provided corresponding to the 1 st slit 21 and the 2 nd slit 22, respectively. The 1 st slit 21, the notch 24 and the divided sipe 25 constitute a sub-groove, and the 2 nd slit 22, the notch 24 and the divided sipe 25 constitute a sub-groove. The sub-grooves divide the center land portion 2 in the tire circumferential direction CD, thereby dividing the center land portion 2 into center blocks 27. The notch 24 is a kind of slit, but has a shorter length in the tire width direction WD than the 1 st slit 21 and the 2 nd slit 22.

< one quarter land portion 3 >

As shown in fig. 6 and 7, the quarter land portion 3 has a plurality of 1 st slits 31 and a plurality of 2 nd slits 32. The 1 st slit 31 is open at the land end 3a (main groove 62) on the 1 st side WD1 in the tire width direction WD, is separated from the land end 3b (main groove 61) on the 2 nd side WD2 in the tire width direction WD, and is closed within the quarter land portion 3. The 2 nd slit 32 is open at the land end 3b (main groove 61) on the 2 nd side WD2 in the tire width direction WD, is separated from the land end 3a (main groove 62) on the 1 st side WD1 in the tire width direction WD, and is closed within the quarter land portion 3. The 1 st slit 31 and the 2 nd slit 32 are different from each other in position in the tire circumferential direction CD, and the 1 st slit 31 and the 2 nd slit 32 are alternately arranged in the tire circumferential direction CD. The quarter land portion 3 has a notch 34 and a partitioning sipe 35. The notch 34 and the divided sipe 35 are provided corresponding to the 1 st slit 31 and the 2 nd slit 32, respectively. The 1 st slit 31, the notch 34 and the divided sipe 35 constitute a sub-groove, and the 2 nd slit 32, the notch 34 and the divided sipe 35 constitute a sub-groove. The sub-grooves divide the quarter land portion 3 in the tire circumferential direction CD, thereby dividing the quarter land portion 3 into quarter blocks 37. The notch 34 is a kind of slit, but has a shorter length in the tire width direction WD than the 1 st slit 31 and the 2 nd slit 32.

In fig. 6, the left shoulder land portion 1 and the quarter land portion 3 are denoted by reference numerals, and the right shoulder land portion 1 and the quarter land portion 3 are obtained by reversing the pattern by rotation.

< sipe >

As shown in fig. 7, a plurality of sipes are formed in each of the shoulder land portion 1, the center land portion 2, and the quarter land portion 3. The sipes are formed by incisions having a width of less than 1.5 mm. Each

land portion

As shown in fig. 7, the circumferential sipe 52 is a sipe having a wavy tread surface shape, extends in the tire circumferential direction CD at the tire width direction center portion of each of the

land portions

1, 2, 3, opens in the sub-grooves (the 1 st slits 11, 21, 31 and the 2 nd slits 12, 22, 32), and divides the

land portions

1, 2, 3 into left and right portions in the tire width direction WD. The closed sipe 53 and the half open sipe 54 are the same as those of embodiment 1.

< sipe area ratio >

As shown in fig. 8, the sipe area ratio Ace of the center land portion 2 and the sipe area ratio Ash of the shoulder land portion 1 are preferably 2% to 15%.

Furthermore, ace and Ash are preferably 5% to 10%.

Further, the relationship Ace > Ash is preferably satisfied.

The land portion area a21 of the center land portion 2 is an area on the tread surface of the center land portion 2 in a state where no sipe is provided as shown by vertical line filling in fig. 8. The sipe area a22 is the total area of the regions filled with oblique lines in fig. 8, and is the total value of the sipe areas on the tread surface of the center land portion 2.

The land portion area a11 of the shoulder land portion 1 is an area on the tread surface of the shoulder land portion 1 in a state where no sipe is provided, as shown by the vertical line filling in fig. 8. Further, a concave portion 55 is formed in the central portion of the block 17, but the concave portion 55 is not included in the land portion area a11. The sipe area a12 is the total area of the regions filled with oblique lines in fig. 8, and is the total value of the sipe areas on the tread surface of the shoulder land portion 1.

The sipe area ratio Ame of the land portion 3 is not particularly limited to this, but preferably satisfies the relationship Ace > Ame ≧ Ash.

The land portion area a31 of the quarter land portion 3 is an area on the tread surface of the quarter land portion 3 in a state where no sipe is provided as shown by filling with a vertical line in fig. 8. Further, a concave portion 55 is formed in the central portion of the block 37, but the concave portion 55 is not included in the land portion area a31. The sipe area a32 is the total area of the regions filled with oblique lines in fig. 3, and is the total value of the sipe areas on the tread surface of the quarter land portion 3.

< volume ratio of sipe >

Fig. 4 is a cross-sectional view showing the volumes of the shoulder land portion 1, the center land portion 2, and the quarter land portion 3 in the tire meridian cross section, similar to embodiment 1. Fig. 9A is a perspective view showing the shoulder land portion 1, the center land portion 2, and the quarter land portion 3 in a state where no sipe is provided. Fig. 9B is a perspective view showing the shoulder land portion 1, the center land portion 2, and the quarter land portion 3 in a state where sipes are provided. As shown in fig. 4, 8, 9A, and 9B, the sipe volume ratio Vce of the center land portion 2 and the sipe volume ratio Vsh of the shoulder land portion 1 are not particularly limited to these, but are preferably 1% or more and 12% or less.

Further, although not particularly limited thereto, it is preferable that Vce > Vsh be satisfied.

As shown in fig. 4, 9A, and 9B, the land portion volume V21 of the center land portion 2 is the volume of the land portion 2 in a state where no sipe is provided as shown by diagonal filling in fig. 4 and as shown in fig. 9A. The land volume V21 includes a region located further outward in the tire radial direction than the boundary line Li and further inward in the tire radial direction than the bottom portions of the sipes and the slits. The sipe volume V22 is the total volume of the sipes filled with oblique lines in fig. 8, and is the total value of the sipe volumes of the center land portion 2. The sipe referred to herein means all sipes. Specifically, the sipe includes a divided sipe 25, a circumferential sipe 52, a closed sipe 53, and a half-opened sipe 54.

As shown in fig. 4, 9A, and 9B, the land volume V11 of the shoulder land portion 1 is the volume of the land portion 1 in a state where no sipe is provided as shown in fig. 9A and as shown by the diagonal filling in fig. 4. The land volume V11 includes a region located further outward in the tire radial direction than the boundary line Li and further inward in the tire radial direction than the bottom portions of the sipes and slits. The sipe volume V12 is the total volume of the sipes filled with oblique lines in fig. 8, and is the total value of the sipe volumes of the shoulder land portion 1. The sipe referred to herein means all sipes. Specifically, the sipe includes a divided sipe 15, a circumferential sipe 52, a closed sipe 53, and a half-opened sipe 54.

The sipe volume ratio Vme of the quarter land portion 3 is not particularly limited to this, but a relationship of Vce > Vme ≧ Vsh is preferable. As shown in fig. 4, 9A and 9B, the land portion volume V31 of the quarter land portion 3 is the volume of the land portion 3 in a state where no sipe is provided as shown by diagonal filling in fig. 4 and as shown in fig. 9A. The land volume V31 includes a region located further toward the tire radial direction outer side than the boundary line Li and further toward the tire radial direction inner side than the sipe or slit bottom. The sipe volume V32 is the total volume of the sipes filled by oblique lines in fig. 8, and is the total value of the volume of the sipe of the quarter land portion 3. The sipe referred to herein means all sipes. Specifically, the sipe includes a divided sipe 35, a circumferential sipe 52, a closed sipe 53, and a half-opened sipe 54.

< relationship between sipe area ratio and sipe volume ratio >

The sipe volume ratio Vce of the center land portion 2, the sipe volume ratio Vsh of the shoulder land portion 1, the sipe area ratio Ace of the center land portion 2, and the sipe area ratio Ash of the shoulder land portion 1 are not particularly limited to these, but preferably satisfy the relationship (Vce/Vsh) > (Ace/Ash).

As described above, the pneumatic tire PT according to embodiment 1 or 2 preferably includes: a plurality of main grooves 61, 62 extending in the tire circumferential direction CD; and a center land portion 2 and a shoulder land portion 1 which are partitioned by the main grooves 61, 62, the shoulder land portion 1 being disposed further toward the tire width direction outer side than a main groove 62 disposed on the outermost side in the tire width direction WD among the plurality of main grooves, the center land portion 2 being disposed further toward the tire width direction inner side than the shoulder land portion 1, the center land portion 2 and the shoulder land portion 1 each including: secondary grooves (16, 26, 18, 51, 11, 12, 14, 15, 21, 22, 24, 25); a plurality of blocks 17 (27) divided by the sub-grooves; and sipes (52, 53, 54), wherein a sipe area ratio Ace which is a ratio of a sipe area A22 on the tread surface Tr of the center land portion 2 to an area A21 on the tread surface Tr, and a sipe area ratio Ash which is a ratio of a sipe area A12 on the tread surface of the shoulder land portion 1 to an area A11 on the tread surface are 2% to 15%, and satisfy the relationship of Ace > Ash.

In this way, if the sipe area ratio Ace and the sipe area ratio Ash are 2% to 15%, it is possible to suppress the reduction in the performance on ice and the acceleration of the wear of the entire block.

In addition, since the sipe area ratio Ace of the center land portion 2 is greater than the sipe area ratio Ash of the shoulder land portion 1, the effect of absorbing water between the tread surface of the center land portion 2 and the ice and snow road where the ground contact pressure is relatively high is improved, whereby the on-ice performance can be improved. Further, the block rigidity of the shoulder land portion 1, which is more likely to be affected by a lateral force than the center land portion 2 and to cause uneven wear, can be secured, and the occurrence of uneven wear can be suppressed.

Therefore, it is possible to improve the on-ice performance and suppress the generation of uneven wear.

As in embodiment 1 or embodiment 2, it is preferable that the sipe volume ratio Vce, which is the ratio of the sipe volume V22 of the center land portion 2 to the land portion volume V21 of the tread surface Tr to the main groove bottom 60, and the sipe volume ratio Vsh, which is the ratio of the sipe volume V22 of the shoulder land portion 1 to the land portion volume V21 of the tread surface Tr to the main groove bottom 60, be 1% or more and 12% or less, and that Vce > Vsh be satisfied.

Thus, if the sipe volume ratio Vce and the sipe volume ratio Vsh are 1% or more and 12% or less, it is possible to suppress the reduction in performance on ice and the acceleration of wear of the entire block.

In addition, since the sipe volume ratio Vce of the center land portion 2 is greater than the sipe volume ratio Vsh of the shoulder land portion 1, the effect of absorbing water between the tread surface of the center land portion 2 and the ice and snow road where the ground contact pressure is relatively high is improved, whereby the on-ice performance can be improved. Further, the block rigidity of the shoulder land portion 1, which is more likely to be affected by a lateral force and to cause uneven wear than the center land portion 2, can be secured, and the occurrence of uneven wear can be suppressed.

Therefore, it is possible to improve the on-ice performance and suppress the generation of partial wear.

As in embodiment 1 or embodiment 2, it is preferable that the sipe volume ratio Vce of the center land portion 2, the sipe volume ratio Vsh of the shoulder land portion 1, the sipe area ratio Ace of the center land portion 2, and the sipe area ratio Ash of the shoulder land portion 1 satisfy the relationship of (Vce/Vsh) > (Ace/Ash).

Therefore, at least one of the improvement of the effective on-ice performance and the improvement of the performance of suppressing the uneven wear can be achieved in consideration of the ground contact pressure.

As in the 1 st embodiment or the 2 nd embodiment, preferably, the sipe includes a1 st sipe (circumferential sipe 52), a2 nd sipe (closed sipe 53) and a3 rd sipe (half-opened sipe 54), the 1 st sipe (circumferential sipe 52) extending in the tire circumferential direction CD at the tire width direction central portion of the block 17 (27) and dividing the block 17 (27) in the tire width direction WD, the 3 rd sipe (closed sipe 53) extending in the tire width direction WD and being closed in the block 17 (27), the 4 th sipe (half-opened sipe 54) extending in the tire width direction central portion of the block 17 (27 37) and having a1 st end 54a closed in the block 17 (27 37) and a2 nd end 54b opened in the tire width direction end of the block 17 (27 WD.

Thus, each block 27 (37) is divided into small blocks in the tire width direction WD from side to side by the circumferential sipes 52, and the small blocks are further divided in the tire circumferential direction CD by the half sipes 54. Thus, a plurality of (4 in the center land portion 2 and the quarter land portion 3) virtual small blocks divided in the tire circumferential direction CD are formed in the 1

block

27, 37. This makes it possible to increase the traction element or the anti-skid element by a virtual small block smaller than the block 27 (37), thereby improving the on-ice performance. However, since the closed sipe 53 is provided and the half-open sipe 54 is provided in the tire circumferential direction central portion of the

block

27, 37, it is possible to increase the traction element while maintaining the rigidity balance in a plurality of (4 in the center land portion 2, the quarter land portion 3) small blocks, thereby making it possible to improve the on-ice performance while suppressing the generation of uneven wear.

The circumferential sipes 52 are not particularly limited thereto, and preferably have a wavy tread shape. The wall surfaces of the circumferential sipes 52 contact each other, so that excessive movement of the small blocks can be suppressed.

As described above, the circumferential sipe 52, the closed sipe 53, and the half open sipe 54 are applied to 1 land portion in combination, but the present invention is not limited thereto. For example, each sipe may be applied to the land portion alone or in combination with any other sipe. For example, when the circumferential sipes 52 are employed, the blocks may be divided into virtual small blocks on the left and right in the tire width direction. In the case of using the half-open sipe 54, it is possible to divide the block into 2 small blocks adjacent in the tire circumferential direction CD, and it is possible to increase the traction element while maintaining the rigidity balance in these small blocks, and it is possible to improve the on-ice performance while suppressing the occurrence of uneven wear.

As in the embodiment 1 or the embodiment 2, it is preferable that the width Wo of the divided sipe 51 and the circumferential sipe 52 (the 1 st sipe) is larger than the width Ws of the half-opened sipe 54 (the 3 rd sipe), and the width Ws of the half-opened sipe 54 (the 3 rd sipe) is larger than the width Wc of the closed sipe 53 (the 2 nd sipe). This can improve the on-ice performance and suppress the occurrence of uneven wear.

While the embodiments of the present invention have been described above with reference to the drawings, it should be understood that the specific configurations are not limited to these embodiments. The scope of the present invention is defined not by the description of the above embodiments but by the claims, and includes all modifications within the meaning and scope equivalent to the claims.

< modification example >

In the embodiment shown in fig. 1 and 6, the center land portion 2 is provided on the tire equator TE, but the present invention is not limited thereto. For example, when 3 main grooves are provided and the center main groove is disposed on the tire equator TE, a pair of center land portions adjacent to each other are disposed at positions that are separated by the center main groove.

The configurations employed in the above embodiments may be applied to any other embodiments. The specific configuration of each part is not limited to the above embodiment, and various modifications may be made without departing from the spirit of the present invention.

The configurations employed in the above embodiments may be applied to any other embodiments.

Claims

1. A pneumatic tire, wherein,

the pneumatic tire is provided with: a plurality of main grooves extending in the tire circumferential direction; and a center land portion and a shoulder land portion divided by the main groove,

the shoulder land portion is disposed further toward the outer side in the tire width direction than a main groove disposed on the outermost side in the tire width direction among the plurality of main grooves,

the center land portion is disposed further toward the tire width direction inner side than the shoulder land portion,

the center land portion and the shoulder land portion are respectively provided with a sub groove, a plurality of pattern blocks divided by the sub groove, and a sipe,

a sipe area ratio Ace which is a ratio of an area of the sipe on the tread surface of the center land portion to an area of the land portion on the tread surface, and a sipe area ratio Ash which is a ratio of an area of the sipe on the tread surface of the shoulder land portion to an area of the land portion on the tread surface are 2% or more and 15% or less, and satisfy a relationship of Ace > Ash,

a sipe volume ratio Vce which is a ratio of a volume of the sipe in the center land portion to a volume of the land portion from the tread surface to the main groove bottom, and a sipe volume ratio Vsh which is a ratio of a volume of the sipe in the shoulder land portion to a volume of the land portion from the tread surface to the main groove bottom are 1% or more and 12% or less, and a relationship of Vce > Vsh is satisfied,

the sipe volume ratio Vce of the center land portion, the sipe volume ratio Vsh of the shoulder land portion, the sipe area ratio Ace of the center land portion, and the sipe area ratio Ash of the shoulder land portion satisfy the following relationship:

(Vce/Vsh)＞(Ace/Ash)。

2. a pneumatic tire, wherein,

the sipes include a1 st sipe, a2 nd sipe, and a3 rd sipe,

the 1 st sipe extends in a tire circumferential direction at a tire width direction central portion of the block and divides the block in the tire width direction,

the 2 nd sipe extends in the tire width direction and is closed in the block,

the 3 rd sipe extends in the tire width direction at the tire circumferential direction central portion of the block, and has a1 st end closed inside the block and a2 nd end opened at the tire width direction end of the block,

the width of the 1 st sipe is larger than the width of the 3 rd sipe, and the width of the 3 rd sipe is larger than the width of the 2 nd sipe.