JP2021154805A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire which further improves ice performance and suppresses uneven wear.SOLUTION: A tire includes a plurality of main grooves extending in a tire circumferential direction and a center land and a shoulder land segmented by the main grooves. The shoulder land is disposed on an outer side in a tire width direction from the main groove on the outermost side in the tire width direction among the plurality of main grooves. The center land is disposed on an inner side in the tire width direction from the shoulder land. The center land and the shoulder land each have sub grooves, a plurality of blocks segmented by the sub grooves, and sipes. When a sipe area ratio Ace is a ratio of the area on the tread face in the sipe to the land area on the tread face in the center land, and a sipe area ratio Ash is a ratio of the area on the tread face in the sipe to the land area on the tread face in the shoulder land, both are 2% or more and 15% or less, and satisfy a relation of Ace>Ash.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to pneumatic tires.

Studless tires that ensure running performance (ice performance) on icy roads with a low coefficient of friction are known. For example, Patent Document 1 has a plurality of blocks as a tread land partitioned by a main groove and a slit, and a sipe provided in each block. The ice performance is enhanced by the edge effect and water removal effect of the sipe, and the ice performance is further enhanced by the traction effect of the slit.

If the number of sipes is increased to improve the ice performance too much, uneven wear may occur.

Japanese Unexamined Patent Publication No. 2012-250610

The present disclosure provides pneumatic tires in pursuit of improved ice performance and suppression of uneven wear.

The pneumatic tire of the present disclosure includes a plurality of main grooves extending in the tire circumferential direction, and a center land and a shoulder land classified by the main grooves, and the shoulder land is the tire width of the plurality of main grooves. The center land is arranged outside the main groove arranged in the outermost direction in the tire width direction, the center land is arranged inside the shoulder land in the tire width direction, and each of the center land and the shoulder land is a sub. The sipe area ratio Ace, which is the ratio of the area on the tread of the sipe to the land area on the tread on the center land, and the shoulder The sipe area ratio Ash, which is the ratio of the area of the sipe to the land area on the tread on land, is 2% or more and 15% or less, and satisfies the relationship of Ace> Ash.

The development view which shows an example of the tread surface of the pneumatic tire of 1st Embodiment. An enlarged development view showing a shoulder block, a quarter block, and a center block according to the first embodiment. An enlarged development view schematically showing the land area and the sipe area of the first embodiment. FIG. 5 is a cross-sectional view showing a block in the tire meridian cross section of the first and second embodiments. The perspective view which shows the land in the state which the sipe of 1st Embodiment is not provided. The perspective view which shows the land in the state which the sipe of 1st Embodiment is provided. The development view which shows an example of the tread surface of the pneumatic tire of 2nd Embodiment. Enlarged development view showing the shoulder block, the quarter block and the center block of the second embodiment. An enlarged development view schematically showing the land area and the sipe area of the second embodiment. The perspective view which shows the land in the state which the sipe of 2nd Embodiment is not provided. The perspective view which shows the land in the state which the sipe of the 2nd Embodiment is provided.

<First Embodiment>
Hereinafter, the first embodiment of the present disclosure will be described with reference to the drawings.

FIG. 1 is a development view of a tread surface Tr included in the pneumatic tire PT of the first embodiment (hereinafter, also simply referred to as “tire PT”). 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-shaped pattern in which a plurality of blocks partitioned by a main groove and a sub-groove 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.

The tread surface Tr of the tire PT is provided with four main grooves 61, 61, 62, 62 extending continuously in the tire circumferential direction CD. In the present embodiment, the number of main grooves is four, but the present invention is not limited to this. The number of main grooves can be three or more. In the present embodiment, the shoulder main groove 62 on the outermost side of the tire width direction WD and the center main groove 61 arranged inside the tire width direction WD of the shoulder main groove 62 are provided. Further, the main groove is not particularly limited, but may have, for example, a groove width of 3% or more of the distance between the ground contact ends CE and CE (dimension of WD in the tire width direction). Further, the main groove is not particularly limited, but may have a groove width of 7.0 mm or more, for example. The main groove is not particularly limited, but for example, it is continuous with the CD in the tire circumferential direction, the groove depth is the deepest in the tread surface Tr, and the inside of the groove is a TWI (tread wear indicator) indicating the usage limit due to wear. ) May be provided.

As used herein, a slit means a groove that is narrower than the main groove and wider than the sipe. Sipe means a groove with a width of less than 1.5 mm. The sub-groove means a groove extending in the tire width direction WD, opening at the land end on the first side in the tire width direction and the land end on the second side in the tire width direction, and dividing the land into the tire circumferential direction CD. Sub-grooves include slits and sipes.

The ground contact end CE is the outermost position of the ground contact surface in the tire width direction when the tire PT is rim-assembled on the regular rim, the tire PT is placed vertically on a flat road surface with the regular internal pressure charged, and a regular load is applied. Is. The following sipe area ratio and sipe volume ratio are measured under the condition that the tire PT is rim-assembled on a regular rim, the tire PT is placed vertically on a flat road surface with the regular internal pressure charged, and a regular load is applied.

A regular rim is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, JATMA is a standard rim, and TRA and ETRTO are "Measuring Rim". The regular internal pressure is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure, and for TRA, the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". If it is the maximum value described in "ETRTO", it is "INFLATION PRESSURE". If the tire is for a passenger car, the value is 180 kPa, and if the tire is described as Extra Load or Reinforced, the value is 220 kPa. The normal load is the load defined for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum load capacity, for TRA, the maximum value listed in the above table. If it is ETRTO, it is "LOAD CAPACITY", but if the tires are for passenger cars, it is 88% of the corresponding load of the internal pressure.

<Shoulder land 1>
As shown in FIGS. 1 and 2, the tire PT has a shoulder land 1 extending in the tire circumferential direction CD at both ends of the tread surface Tr in the tire width direction. The shoulder land 1 is arranged outside the outermost main groove 62 in the tire width direction WD. The shoulder land 1 is divided into the outermost main groove 62 in the tire width direction WD and the ground contact end CE. The shoulder land 1 has a plurality of fully open slits 16 and a plurality of shoulder blocks 17 arranged in a tire circumferential direction CD. Shoulder land 1 constitutes a block row. The fully open slit 16 is open to the main groove 62 and the ground contact end CE, and divides the shoulder block 17 into the tire circumferential direction CD. The shoulder block 17 has at least one semi-open slit 18. The semi-open slit 18 has a first end and a second end, the first end opens to any block end in the tire width direction WD, and the second end closes in the shoulder block 17. In the present embodiment, the semi-open slit 18 includes a long semi-open slit 18a that opens to the inner block end 1a in the tire width direction WD and a short semi that opens to the inner block end 1a or the ground contact end CE in the tire width direction WD. Includes an open slit 18b (also called a notch). The fully open slit 16 is a secondary groove. As shown in FIGS. 1 and 2, the shoulder land 1 has a dividing sipe 51 that opens into a long semi-open slit 18a and a short semi-open slit 18b. The semi-open slit 18 (long semi-open slit 18a, short semi-open slit 18b) and the dividing sipe 51 form an auxiliary groove. The sub-groove divides the shoulder land 1 into shoulder blocks 17.

<Center Land 2>
The tire PT has a center land 2 extending in the tire circumferential direction CD at the central portion of the tread surface Tr in the tire width direction. Center land 2 is the land closest to the tire equator TE. The center land 2 is divided into a pair of main grooves 61, 61. The center land 2 has a plurality of fully open slits 26 and a plurality of center blocks 27 arranged in a tire circumferential direction CD. Center land 2 constitutes a block row. The fully open slit 26 opens in the main groove 61 and divides the center block 27 into the tire circumferential direction CD. The center block 27 has at least one semi-open slit 28. The semi-open slit 28 has a first end and a second end, the first end opens to any block end in the tire width direction WD, and the second end closes in the center block 27. The fully open slit 26 is a secondary groove.

<Slit in Quarter Land 3>
The tire PT has a quarter land 3 extending in the tire circumferential direction CD between the shoulder land 1 and the center land 2. The quarter land 3 is divided into a pair of main grooves 61 and 62. The quarter land 3 has a plurality of fully open slits 36 and a plurality of quarter blocks 37 arranged in a tire circumferential direction CD. Quarter land 3 constitutes a block row. The full open slit 36 opens in the main grooves 61 and 62, and divides the quarter block 37 into the tire circumferential direction CD. The quarter block 37 has at least one semi-open slit 38. The semi-open slit 38 has a first end and a second end, the first end opens to any block end in the tire width direction WD, and the second end closes in the quarter block 37. The fully open slit 36 is a secondary groove.

<Sipe>
As shown in FIGS. 1 and 2, a plurality of sipes are formed on each land of the shoulder land 1, the center land 2, and the quarter land 3. The sipe is formed by notches less than 1.5 mm wide. Each land 1, 2, 3 has a circumferential sipe 52, a closed sipe 53, and a semi-open sipe 54.

As shown in FIGS. 1 and 2, the circumferential sipe 52 is a sipe having a wavy tread shape, and is a fully open slit extending in the tire circumferential direction CD at the center of each of the land 1, 2 and 3 in the tire width direction. It opens in 16, 26, 36 or a semi-open slit 18, and divides land 1, 2, and 3 into left and right blocks in the tire width direction WD. Therefore, in the present embodiment, from the viewpoint of suppressing the movement of the divided blocks and reducing uneven wear, the circumferential sipe 52 has a wavy tread shape and the shape changes along the depth direction. It is a three-dimensional sipe that includes the part to be used. However, the present invention is not limited to this, and the circumferential sipe 52 may be a two-dimensional sipe whose shape does not change along the depth direction. As shown in FIG. 2, the slit width narrow portions 26a and 36a are inclined with respect to the tire circumferential direction CD and the tire width direction WD. The circumferential sipe 52 that opens in the slit width narrow portions 26a and 36a is inclined with respect to the tire circumferential direction CD and the tire width direction WD. The circumferential sipe 52 and the slit width narrow portions 26a and 36a are inclined in opposite directions with respect to the tire circumferential direction CD and the tire width direction WD. This is to suppress uneven wear by making the corners of the block formed by the narrow slit width portions 26a and 36a and the circumferential sipe 52 at right angles or substantially right angles without making them acute. The substantially right angle here means 60 degrees or more and less than 90 degrees. Specifically, as shown in FIG. 2, the slit width narrow portions 26a and 36a are the tire circumferential direction first side CD1 and the tire width direction second side WD2 to the diamond circumferential direction second side CD2 and the tire width direction first. Head to the side WD1. The circumferential sipe 52 formed on the center land 2 and the quarter land 3 goes from the tire circumferential direction first side CD1 and the tire width direction first side WD1 to the timetable circumferential direction second side CD2 and the second side WD2.
The closed sipe 53 is a sipe having a wavy tread shape, extends in the tire width direction WD, and closes within each land 1, 2, and 3.
The semi-open sipe 54 is a sipe having a wavy tread shape and extends in the tire width direction WD at the central portion in the tire circumferential direction. The semi-open sipe 54 has a first end 54a that closes within each land 1, 2, 3 and a second end 54b that opens at the land end of each land 1, 2, 3.

The closed sipe 53 and the semi-open sipe 54 have a wavy tread shape, but the tread shape is not limited to this and may be a straight line. Further, the closed sipe 53 and the semi-open sipe 54 are two-dimensional sipe whose shape does not change along the depth direction, but may be a three-dimensional sipe including a portion whose shape changes along the depth direction. ..

As shown in FIGS. 1 and 2, the shoulder land 1 is divided into two pseudo small blocks adjacent to the tire circumferential CD by the dividing sipe 51 of the shoulder land 1.
As shown in FIGS. 1 and 2, each land 2 and 3 is divided into small blocks on the left and right sides of the tire width direction WD by the circumferential sipe 52, and the small blocks are further simulated as a tire circumferential CD by the semi-open sipe 54. Is divided. As a result, a plurality of pseudo small blocks (four in the center land 2 and the quarter land 3) divided into the tire circumferential CDs are formed in one block 27 and 37. Thereby, the traction element or the skid resistance element can be increased by the pseudo small block smaller than one block 27, 37, and the ice performance can be improved. Nevertheless, since the closed sipe 53 is provided and the semi-open sipe 54 is provided at the center of the blocks 27 and 37 in the tire circumferential direction, the rigidity in a plurality of small blocks (four in the center land 2 and the quarter land 3) is provided. It is possible to increase the traction elements while maintaining the balance, and it is possible to improve the ice performance while suppressing the occurrence of uneven wear.
Although not particularly limited, it is preferable that the tread shape of the circumferential sipe 52 is wavy. The wall surfaces of the circumferential sipes 52 come into contact with each other, and excessive movement of the small blocks can be suppressed.

As shown in FIG. 1, the block closest to the grounding end CE, which is divided by the circumferential sipe 52, is easily affected by the lateral force, so that all the sipe is only the closed sipe 53.

From the viewpoint of improving ice performance and suppressing the occurrence of uneven wear, the width Wo of the split sipe 51 and the circumferential sipe 52 is thicker than the width Ws of the semi-open sipe 54, and the width Ws of the semi-open sipe 54 is the closed sipe. It is preferably thicker than the width Wc of 53. Wo> Ws> Wc. By making the width Wo of the open sipe (divided sipe 51, circumferential sipe 52) relatively thick, it is possible to improve the ice performance while ensuring the rigidity of the land compared to the block pattern composed of grooves. Become. By making the width Wc of the closed sipe 53 relatively thin, it is possible to suppress the movement of the block and reduce the factors of wear or uneven wear. By setting the width of the semi-open sipe 54 to an intermediate width between the open sipe (divided sipe 51, circumferential sipe 52) and the closed sipe 53, it is possible to balance the block rigidity and the ice performance. Of course, if these viewpoints are not a problem, the widths of all sipes may be the same, and the magnitude relationship of the widths can be changed in various ways.

The depth of the sipe in the present specification is preferably 50% or more and 80% or less of the depth of the main groove. If the depth of the sipe is shallower than 50% of the depth of the main groove, the ice performance as a winter tire will be insufficient. If the depth of the sipe is deeper than 80% of the depth of the main groove, the rigidity of the land will decrease, which will cause uneven wear.

<Sipe area ratio>
As shown in FIG. 3, the sipe area ratio Ace of the center land 2 and the sipe area ratio Ash of the shoulder land 1 are preferably 2% or more and 15% or less. This is to suppress deterioration of ice performance and accelerated wear of the entire block.
Further, the sipe area ratio Ace of the center land 2 and the sipe area ratio Ash of the shoulder land 1 are preferably 5% or more and 10% or less.
If the sipe area ratio Ace and Ash are less than 2%, the effect of sipe absorbing the water film between the tire and the ice-snow road surface becomes small, which causes a decrease in ice performance.
When the sipe area ratios Ace and Ash are larger than 15%, the block rigidity is lowered and the wear of the entire block is promoted.

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

Further, it is preferable to satisfy the relationship of Ace> Ash. As a result, since the sipe area ratio Ace of the center land 2 is larger than the sipe area ratio Ash of the shoulder land 1, the water absorption effect of water between the tread and the ice / snow road is enhanced in the center land 2 where the ground pressure is relatively high. It is possible to improve the ice performance. Further, it is possible to secure the block rigidity of the shoulder land 1 which is more susceptible to lateral force than the center land 2 and which is more likely to cause uneven wear, and suppress the occurrence of uneven wear. Therefore, it is possible to improve the ice performance and suppress the occurrence of uneven wear.

The sipe area ratio Ace of the center land 2 indicates the ratio of the sipe area A22 to the land area A21 on the tread in the center land 2. In the formula, it is expressed as Ace = A22 / A21. The land area A21 is the area on the tread of the center land 2 in the state where the sipe is not provided, as shown by being filled with vertical lines in FIG. The sipe area A22 is the total area of the areas filled with diagonal lines in FIG. 3, and is the total area of sipe on the tread surface of the center land 2. The sipe here means all sipe in the center land 2. Specifically, the circumferential sipe 52, the closed sipe 53, and the semi-open sipe 54 are included.

The sipe area ratio Ash of the shoulder land 1 indicates the ratio of the sipe area A12 to the land area A11 on the tread of the shoulder land 1. In the formula, it is expressed as Ash = A12 / A11. The block 17 is partitioned by a main groove 62 and a sub groove (semi-open slit 18, dividing sipe 51). The land area A11 is the area on the tread of the shoulder land 1 in the state where the sipe is not provided, as shown by being filled with vertical lines in FIG. Although the recess 55 is formed in the central portion of the block 17, the recess 55 is not included in the land area A11. The area A12 of the sipe is the total area of the areas filled with diagonal lines in FIG. 3, and is the total area of the sipe on the tread surface of the shoulder land 1. The sipe here means all sipe. Specifically, the divided sipe 51, the circumferential sipe 52, the closed sipe 53, and the semi-open sipe 54 are included.

The sipe area ratio Ame of the quarter land 3 (quarter block 37) is not particularly limited, but it is preferable that the relationship of Ace> Ame ≧ Ash is satisfied. As a result, uneven wear of the quarter land 3 can be suppressed. If Ame> Ash, it is possible to give the quarter land 3 a role of both improving ice performance and suppressing uneven wear.

The sipe area ratio Ame of the quarter land 3 indicates the ratio of the sipe area A32 to the land area A31 on the tread in the quarter land 3. In the formula, it is expressed as Ame = A32 / A31. The land area A31 is the area on the tread of the quarter land 3 in the state where the sipes are not provided, as shown by being filled with vertical lines in FIG. Although the recess 55 is formed in the central portion of the block 37, the recess 55 is not included in the land area A31. The area A32 of the sipe is the total area of the areas filled with diagonal lines in FIG. 3, and is the total area of the sipe on the tread surface of the quarter land 3. The sipe here means all sipe. Specifically, the circumferential sipe 52, the closed sipe 53, and the semi-open sipe 54 are included.

<Sipe volume ratio>
FIG. 4 is a cross-sectional view showing the volumes of the shoulder land 1, the center land 2, and the quarter land 3 in the tire meridian cross section. FIG. 5A is a perspective view showing a shoulder land 1, a center land 2, and a quarter land 3 in a state where no sipes are provided. FIG. 5B is a perspective view showing a shoulder land 1, a center land 2, and a quarter land 3 in a state where a sipe is provided. As shown in FIGS. 3, 4, 5A and 5B, the sipe volume ratio Vce of the center land 2 and the sipe volume ratio Vsh of the shoulder land 1 are not particularly limited, but are 1% or more and 12% or less. Is preferable. This is to suppress deterioration of ice performance and accelerated wear of the entire block.
Further, the sipe volume ratio Vce of the center land 2 and the sipe volume ratio Vsh of the shoulder land 1 are preferably 2% or more and 8% or less.
If the sipe volume ratio Vce and Vsh are less than 1%, the effect of sipe absorbing the water film between the tire and the ice-snow road surface becomes small, which causes a decrease in ice performance.
When the sipe volume ratios Vce and Vsh are larger than 12%, the block rigidity is lowered and the wear of the entire block is promoted.

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

Further, although not particularly limited, it is preferable to satisfy the relationship of Vce> Vsh. As a result, since the sipe volume ratio Vce of the center land 2 is larger than the sipe volume ratio Vsh of the shoulder land 1, the water absorption effect of water between the tread and the ice and snow road is enhanced in the center land 2 where the ground pressure is relatively high. It is possible to improve the ice performance. Further, it is possible to secure the block rigidity of the shoulder land 1 which is more susceptible to lateral force than the center land 2 and which is more likely to cause uneven wear, and suppress the occurrence of uneven wear. Therefore, it is possible to improve the ice performance and suppress the occurrence of uneven wear.

As shown in FIGS. 4, 5A and 5B, the sipe volume ratio Vce of the center land 2 indicates the ratio of the sipe volume V22 to the land volume V21 from the tread Tr to the main groove bottom 60 in the center land 2. In the formula, it is expressed as Vce = V22 / V21. The land volume V21 is the volume of the land 2 in a state where the sipe is not provided, as shown by being filled with diagonal lines in FIG. 4 and shown in FIG. 5A. The land volume V21 includes a region outside the tire radial direction with respect to the boundary line Li and inside with respect to the bottom of the sipe and slit in the tire radial direction. The sipe volume V22 is the total volume of the sipe filled with diagonal lines in FIG. 3, and is the total volume of the sipe in the center land 2. The sipe here means all sipe. Specifically, the circumferential sipe 52, the closed sipe 53, and the semi-open sipe 54 are included.

As shown in FIG. 4, the boundary line Li inside the tire radial direction RD for defining the land volumes V11, V21, and V31 is composed of a single or a plurality of arcs in the tire meridian cross section. The arc has a single radius of curvature that passes through at least three main groove bottoms 60.

As shown in FIGS. 4, 5A and 5B, the sipe volume ratio Vsh of the shoulder land 1 indicates the ratio of the sipe volume V12 to the land volume V11 from the tread Tr to the main groove bottom 60 in the shoulder land 1. In the formula, it is expressed as Vsh = V12 / V11. The land volume V11 is the volume of the land 2 in a state where the sipe is not provided, as shown by being filled with diagonal lines in FIG. 4 and shown in FIG. 5A. The land volume V11 includes a region outside the tire radial direction with respect to the boundary line Li and inside with respect to the bottom of the sipe and slit in the tire radial direction. The sipe volume V12 is the total volume of the sipe painted with diagonal lines in FIG. 3, and is the total volume of the sipe of the shoulder land 1. The sipe here means all sipe. Specifically, the divided sipe 51, the circumferential sipe 52, the closed sipe 53, and the semi-open sipe 54 are included.

The sipe volume ratio Vme of the quarter land 3 is not particularly limited, but it is preferable that the relationship of Vce> Vme ≧ Vsh is satisfied. As a result, uneven wear of the quarter land 3 can be suppressed. If Vme> Vsh, it is possible to give the quarter land 3 a role of both improving ice performance and suppressing uneven wear.

As shown in FIGS. 4, 5A and 5B, the sipe volume ratio Vme of the quarter land 3 indicates the ratio of the sipe volume V32 to the land volume V31 from the tread Tr to the main groove bottom 60 in the quarter land 3. In the formula, it is expressed as Vme = V32 / V31. The land volume V31 is the volume of the land 3 in a state where the sipe is not provided, as shown by being filled with diagonal lines in FIG. 4 and shown in FIG. 5A. The land volume V31 includes a region outside the tire radial direction with respect to the boundary line Li and inside with respect to the bottom of the sipe and slit in the tire radial direction. The sipe volume V32 is the total volume of the sipe filled with diagonal lines in FIG. 3, and is the total volume of the sipe of the quarter land 3. The sipe here means all sipe. Specifically, the circumferential sipe 52, the closed sipe 53, and the semi-open sipe 54 are included.

<Relationship between sipe area ratio and sipe volume ratio>
The sipe volume ratio Vce at the center land 2, the sipe volume ratio Vsh at the shoulder land 1, the sipe area ratio Ace at the center land 2, and the sipe area ratio Ash at the shoulder land 1 are in the relationship of (Vce / Vsh)> (Ace / Ash). It is preferable to satisfy. As a result, it is possible to effectively improve the ice performance in consideration of the ground contact pressure and at least one of the performance improvement of suppressing uneven wear.
If the relationship of (Vce / Vsh)> (Ace / Ash) is satisfied, (1) the land volume of the shoulder land 1 is increased compared to the area, or (2) the sipe volume of the center land 2 is compared to the area. It will be either increasing or at least one of them.
(1) When the land volume of the shoulder land 1 is larger than the area, the sub-grooves (16, 18, 51) of the shoulder land 1 become the sub-grooves (full open slit 26) of the center land 2. Compared to this, it becomes relatively shallow, and uneven wear can be suppressed.
(2) When the sipe volume of the center land 2 is larger than the area, the sipe of the center land 2 is relatively deeper than the sipe of the shoulder land 1, and the center land 2 has a high contact pressure. It is possible to improve the ice performance by enhancing the water absorption effect of.

<Second Embodiment>
The second embodiment is the same as the first embodiment with respect to the ground contact end, the sipe area ratio, the sipe volume ratio, the circumferential sipe 52, the closed sipe 53, and the semi-open sipe 54, only the tread pattern is different. The same components are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 6, the tread pattern formed on the tread surface Tr is a block-shaped pattern in which a plurality of blocks partitioned by a main groove and a sub-groove are arranged in the tire circumferential direction. As used herein, a slit means a groove that is narrower than the main groove and wider than the sipe. Sipe means a groove with a width of less than 1.5 mm. The sub-groove means a groove extending in the tire width direction WD, opening at the land end on the first side in the tire width direction and the land end on the second side in the tire width direction, and dividing the land into the tire circumferential direction CD. Sub-grooves include slits and sipes.

<Shoulder land 1>
As shown in FIGS. 6 and 7, the shoulder land 1 has a plurality of first slits 11 and a plurality of second slits 12. The first slit 11 opens at the land end 1a (ground contact end CE) of the first side WD1 in the tire width direction WD, and is separated from the land end 1b (main groove 62) of the second side WD2 in the tire width direction WD. It is blocked in the shoulder land 1. The second slit 12 opens at the land end 1b (main groove 62) of the second side WD2 in the tire width direction WD, and is separated from the land end 1a (ground contact end CE) of the first side WD1 in the tire width direction WD. It is blocked in the shoulder land 1. The first slit 11 and the second slit 12 have different positions of the tire circumferential CDs from each other, and are alternately arranged in the tire circumferential CDs. The shoulder land 1 has a notch 14 and a dividing sipe 15. The notch 14 and the dividing sipe 15 are provided corresponding to the first slit 11 and the second slit 12, respectively. The first slit 11, the notch 14, and the dividing sipe 15 form an auxiliary groove, and the second slit 12, the notch 14, and the dividing sipe 15 form an auxiliary groove. The sub-groove divides the shoulder land 1 into tire circumferential CDs and the shoulder land 1 into shoulder blocks 17. The notch 14 is a kind of slit, but the length of the WD in the tire width direction is shorter than that of the first slit 11 and the second slit 12.

<Center Land 2>
As shown in FIGS. 6 and 7, the center land 2 has a plurality of first slits 21 and a plurality of second slits 22. The first slit 21 opens at the land end 2a (main groove 61) of the first side WD1 in the tire width direction WD, and is separated from the land end 2b (main groove 61) of the second side WD2 in the tire width direction WD. It is blocked in the center land 2. The second slit 22 opens at the land end 2b (main groove 61) of the second side WD2 in the tire width direction WD, and is separated from the land end 2a (main groove 61) of the first side WD1 in the tire width direction WD. , It is blocked in the center land 2. The first slit 21 and the second slit 22 have different positions of the tire circumferential CDs from each other, and are alternately arranged in the tire circumferential CDs. The center land 2 has a notch 24 and a dividing sipe 25. The notch 24 and the dividing sipe 25 are provided corresponding to the first slit 21 and the second slit 22, respectively. The first slit 21, the notch 24, and the dividing sipe 25 form an auxiliary groove, and the second slit 22, the notch 24, and the dividing sipe 25 form an auxiliary groove. The sub-groove divides the center land 2 into the tire circumferential CD and the center land 2 into the center block 27. The notch 24 is a type of slit, but the length of the WD in the tire width direction is shorter than that of the first slit 21 and the second slit 22.

<Quarter Land 3>
As shown in FIGS. 6 and 7, the quarter land 3 has a plurality of first slits 31 and a plurality of second slits 32. The first slit 31 opens at the land end 3a (main groove 62) of the first side WD1 in the tire width direction WD, and is separated from the land end 3b (main groove 61) of the second side WD2 in the tire width direction WD. It is blocked in Quarter Land 3. The second slit 32 opens at the land end 3b (main groove 61) of the second side WD2 in the tire width direction WD, and is separated from the land end 3a (main groove 62) of the first side WD1 in the tire width direction WD. , It is blocked in the quarter land 3. The first slit 31 and the second slit 32 have different positions of the tire circumferential CDs from each other, and are alternately arranged in the tire circumferential CDs. The quarter land 3 has a notch 34 and a dividing sipe 35. The notch 34 and the dividing sipe 35 are provided corresponding to the first slit 31 and the second slit 32, respectively. The first slit 31, the notch 34 and the dividing sipe 35 form an auxiliary groove, and the second slit 32, the notch 34 and the dividing sipe 35 form an auxiliary groove. The sub-groove divides the quarter land 3 into tire circumferential CDs and the quarter land 3 into quarter blocks 37. The notch 34 is a type of slit, but the length of the WD in the tire width direction is shorter than that of the first slit 31 and the second slit 32.

In FIG. 6, the shoulder land 1 and the quarter land 3 on the left side are described with reference numerals, but the shoulder land 1 and the quarter land 3 on the right side of the figure are obtained by reversing the pattern by rotation. ..

<Sipe>
As shown in FIG. 7, a plurality of sipes are formed on each of the shoulder land 1, the center land 2, and the quarter land 3. The sipe is formed by notches less than 1.5 mm wide. Each land 1, 2, 3 has a circumferential sipe 52, a closed sipe 53, and a semi-open sipe 54.

As shown in FIG. 7, the circumferential sipe 52 is a sipe having a wavy tread shape, and extends in the tire circumferential direction CD at the central portion in the tire width direction of each land 1, 2, and 3, and has a secondary groove (first slit). It opens in 11,21,31 and the second slits 12,22,32) and divides the land 1,2,3 into the left and right in the tire width direction WD. The closed sipe 53 and the semi-open sipe 54 are the same as those in the first embodiment.

<Sipe area ratio>
As shown in FIG. 8, the sipe area ratio Ace of the center land 2 and the sipe area ratio Ash of the shoulder land 1 are preferably 2% or more and 15% or less.
Further, Ace and Ash are preferably 5% or more and 10% or less.
Further, it is preferable to satisfy the relationship of Ace> Ash.

The land area A21 of the center land 2 is the area of the tread of the center land 2 in the state where the sipe is not provided, as shown by being filled with vertical lines in FIG. The sipe area A22 is the total area of the areas filled with diagonal lines in FIG. 8, and is the total area of sipe on the tread surface of the center land 2.

The land area A11 of the shoulder land 1 is the area of the tread of the shoulder land 1 in a state where the sipe is not provided, as shown by being filled with vertical lines in FIG. Although the recess 55 is formed in the central portion of the block 17, the recess 55 is not included in the land area A11. The area A12 of the sipe is the total area of the areas filled with diagonal lines in FIG. 8, and is the total area of the sipe on the tread surface of the shoulder land 1.

The sipe area ratio Ame of the quarter land 3 is not particularly limited, but it is preferable that the relationship of Ace> Ame ≧ Ash is satisfied.

The land area A31 of the quarter land 3 is the area of the tread of the quarter land 3 in a state where no sipes are provided, as shown by filling in with vertical lines in FIG. Although the recess 55 is formed in the central portion of the block 37, the recess 55 is not included in the land area A31. The area A32 of the sipe is the total area of the areas filled with diagonal lines in FIG. 3, and is the total area of the sipe on the tread surface of the quarter land 3.

<Sipe volume ratio>
FIG. 4 is a cross-sectional view showing the volumes of the shoulder land 1, the center land 2, and the quarter land 3 in the tire meridian cross section, and is the same as the first embodiment. FIG. 9A is a perspective view showing a shoulder land 1, a center land 2, and a quarter land 3 in a state where no sipes are provided. FIG. 9B is a perspective view showing a shoulder land 1, a center land 2, and a quarter land 3 in a state where a sipe is provided. As shown in FIGS. 4, 8, 9A and 9B, the sipe volume ratio Vce of the center land 2 and the sipe volume ratio Vsh of the shoulder land 1 are not particularly limited, but are 1% or more and 12% or less. Is preferable.
Further, the sipe volume ratio Vce of the center land 2 and the sipe volume ratio Vsh of the shoulder land 1 are preferably 2% or more and 8% or less.
Further, although not particularly limited, it is preferable to satisfy the relationship of Vce> Vsh.

As shown in FIGS. 4, 9A and 9B, the land volume V21 of the center land 2 is shown by being shaded in FIG. 4, and as shown in FIG. 9A, the volume of the land 2 in the state where the sipe is not provided. Is. The land volume V21 includes a region outside the tire radial direction with respect to the boundary line Li and inside with respect to the bottom of the sipe and slit in the tire radial direction. The sipe volume V22 is the total volume of the sipe filled with diagonal lines in FIG. 8, and is the total volume of the sipe in the center land 2. The sipe here means all sipe. Specifically, the divided sipe 25, the circumferential sipe 52, the closed sipe 53, and the semi-open sipe 54 are included.

As shown in FIGS. 4, 9A and 9B, the land volume V11 of the shoulder land 1 is shown by being shaded in FIG. 4, and as shown in FIG. 9A, the volume of the land 1 in the state where the sipe is not provided. Is. The land volume V11 includes a region outside the tire radial direction with respect to the boundary line Li and inside with respect to the bottom of the sipe and slit in the tire radial direction. The sipe volume V12 is the total volume of the sipe painted with diagonal lines in FIG. 8, and is the total volume of the sipe of the shoulder land 1. The sipe here means all sipe. Specifically, the divided sipe 15, the circumferential sipe 52, the closed sipe 53, and the semi-open sipe 54 are included.

The sipe volume ratio Vme of the quarter land 3 is not particularly limited, but it is preferable that the relationship of Vce> Vme ≧ Vsh is satisfied. As shown in FIGS. 4, 9A and 9B, the land volume V31 of the quarter land 3 is shown by being shaded in FIG. 4, and as shown in FIG. 9A, the volume of the land 3 in the state where the sipe is not provided. Is. The land volume V31 includes a region outside the tire radial direction with respect to the boundary line Li and inside with respect to the bottom of the sipe and slit in the tire radial direction. The sipe volume V32 is the total volume of the sipe filled with diagonal lines in FIG. 8, and is the total volume of the sipe of the quarter land 3. The sipe here means all sipe. Specifically, the divided sipe 35, the circumferential sipe 52, the closed sipe 53, and the semi-open sipe 54 are included.

<Relationship between sipe area ratio and sipe volume ratio>
The sipe volume ratio Vce at the center land 2, the sipe volume ratio Vsh at the shoulder land 1, the sipe area ratio Ace at the center land 2, and the sipe area ratio Ash at the shoulder land 1 are not particularly limited, but (Vce / Vsh)> ( It is preferable to satisfy the relationship of Ace / Ash).

As described above, the pneumatic tire PT of the first embodiment or the second embodiment has a plurality of main grooves 61 and 62 extending in the tire circumferential direction CD, and the center land 2 and shoulders classified by the main grooves 61 and 62. The land 1 is provided, the shoulder land 1 is arranged outside the main groove 62 arranged in the outermost part of the tire width direction WD among the plurality of main grooves, and the center land 2 is arranged outside the shoulder land 1 in the tire width direction. Arranged inside in the tire width direction, each of the center land 2 and the shoulder land 1 has a sub-groove (16, 26, 18, 51, 11, 12, 14, 15, 21, 22, 24, 25,). , A plurality of blocks 17 (27) classified by a secondary groove and sipes (52, 53, 54) are provided, and the ratio of the area A22 on the tread Tr of the sipe to the area A21 on the tread Tr at the center land 2 A certain sipe area ratio Ace and a sipe area ratio Ash, which is the ratio of the area A12 on the tread of the sipe to the area A11 on the tread on the shoulder land 1, are 2% or more and 15% or less, and the relationship of Ace> Ash. It is preferable to meet.

As described above, when the sipe area ratio Ace and the sipe area ratio Ash are 2% or more and 15% or less, it is possible to suppress deterioration of ice performance and promotion of wear of the entire block.
Further, since the sipe area ratio Ace of the center land 2 is larger than the sipe area ratio Ash of the shoulder land 1, the water absorption effect of water between the tread and the ice / snow road is enhanced in the center land 2 where the ground pressure is relatively high, and the ice ice. It is possible to improve the performance. Further, it is possible to secure the block rigidity of the shoulder land 1 which is more susceptible to lateral force than the center land 2 and which is more likely to cause uneven wear, and suppress the occurrence of uneven wear.
Therefore, it is possible to improve the ice performance and suppress the occurrence of uneven wear.

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

As described above, when the sipe volume ratio Vce and the sipe volume ratio Vsh are 1% or more and 12% or less, it is possible to suppress deterioration of ice performance and promotion of wear of the entire block.
Further, since the sipe volume ratio Vce of the center land 2 is larger than the sipe volume ratio Vsh of the shoulder land 1, the water absorption effect of water between the tread and the ice / snow road is enhanced in the center land 2 where the ground pressure is relatively high, and the ice ice. It is possible to improve the performance. Further, it is possible to secure the block rigidity of the shoulder land 1 which is more susceptible to lateral force than the center land 2 and which is more likely to cause uneven wear, and suppress the occurrence of uneven wear.
Therefore, it is possible to improve the ice performance and suppress the occurrence of uneven wear.

As in the first embodiment or the second embodiment, the sipe volume ratio Vce of the center land 2, the sipe volume ratio Vsh of the shoulder land 1, the sipe area ratio Ace of the center land 2, and the sipe area ratio Ash of the shoulder land 1 are , (Vce / Vsh)> (Ace / Ash) is preferably satisfied.

Therefore, it is possible to effectively improve the ice performance in consideration of the ground contact pressure and at least one of the performance improvement of suppressing uneven wear.

As in the first or second embodiment, the sipe includes a first sipe (circumferential sipe 52), a second sipe (closed sipe 53), and a third sipe (semi-open sipe 54). , The first sipe (circumferential sipe 52) extends in the tire circumferential direction CD at the central portion of the block 17 (27; 37) in the tire width direction and divides the block 17 (27; 37) into the tire width direction WD. The 3 sipe (closed sipe 53) extends in the tire width direction WD and closes in the block 17 (27; 37), and the 4th sipe (semi-open sipe 54) extends around the tire of the block 17 (27; 37). Having a first end 54a extending in the tire width direction WD at the center of the direction and closing in the block 17 (27; 37) and a second end 54b opening in the tire width direction end of the block 17 (27; 37). Is preferable.

As a result, each block 27 (37) is divided into small blocks on the left and right sides of the tire width direction WD by the circumferential sipe 52, and the small blocks are further divided into tire circumferential CDs by the semi-open sipe 54. As a result, a plurality of pseudo small blocks (four in the center land 2 and the quarter land 3) divided into the tire circumferential CDs are formed in one block 27 and 37. Thereby, the traction element or the skid resistance element can be increased by the pseudo small block smaller than the block 27 (37), and the ice performance can be improved. Nevertheless, since the closed sipe 53 is provided and the semi-open sipe 54 is provided at the center of the blocks 27 and 37 in the tire circumferential direction, the rigidity in a plurality of small blocks (four in the center land 2 and the quarter land 3) is provided. It is possible to increase the traction elements while maintaining the balance, and it is possible to improve the ice performance while suppressing the occurrence of uneven wear.
Although not particularly limited, it is preferable that the tread shape of the circumferential sipe 52 is wavy. The wall surfaces of the circumferential sipes 52 come into contact with each other, and excessive movement of the small blocks can be suppressed.

In the above, the circumferential sipe 52, the closed sipe 53 and the semi-open sipe 54 are applied in combination to one block, but the present invention is not limited to this. For example, each sipe can be applied on land alone or in combination with any other sipe. For example, when the circumferential sipe 52 is adopted, the block can be divided into left and right in the tire width direction to make a pseudo small block. When the semi-open sipe 54 is adopted, the traction element can be increased while maintaining the rigidity balance in these small blocks while dividing into two small blocks adjacent to the tire circumferential CD, and uneven wear occurs. It is possible to improve the ice performance while suppressing the problem.

As in the first or second embodiment, the width Wo of the dividing sipe 51 and the circumferential sipe 52 (first sipe) is thicker than the width Ws of the semi-open sipe 54 (third sipe), and the semi-open sipe. The width Ws of 54 (third sipe) is preferably thicker than the width Wc of closed sipe 53 (second sipe). This makes it possible to improve the ice performance and suppress the occurrence of uneven wear.

Although the embodiments of the present disclosure have been described above with reference to the drawings, it should be considered that the specific configuration is not limited to these embodiments. The scope of the present disclosure is shown not only by the description of the above-described embodiment but also by the scope of claims, and further includes all modifications within the meaning and scope equivalent to the scope of claims.

<Modification example>
In the embodiment shown in FIGS. 1 and 6, the center land 2 is provided on the tire equator TE, but is not limited thereto. For example, when there are three main grooves and the middle main groove is arranged on the tire equator TE, a pair of adjacent center lands are arranged at positions sandwiching the middle main groove.

It is possible to adopt the structure adopted in each of the above embodiments in any other embodiment. The specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present disclosure.

It is possible to adopt the structure adopted in each of the above embodiments in any other embodiment.

1 ... Shoulder land, 2 ... Center land, 17, 27 ... Block, 16, 26, 36 ... Full open slit (secondary groove), 18 ... Semi-open slit (secondary groove), 51 ... Dividing sipe (secondary groove), 11 , 22, 32 ... 1st slit (secondary groove), 12, 22, 32 ... 2nd slit (secondary groove), 14, 24, 34 ... notch (secondary groove), 15, 25, 35 ... ), 52 ... Circumferential sipe (sipe, 1st sipe), 53 ... Closed sipe (sipe, 2nd sipe), 54 ... Semi-open sipe (sipe, 3rd sipe), 61, 62 ... Main groove

Claims (5)

A plurality of main grooves extending in the tire circumferential direction and a center land and a shoulder land classified by the main grooves are provided.
The shoulder land is arranged outside in the tire width direction with respect to the outermost main groove in the tire width direction among the plurality of main grooves.
The center land is arranged inside the tire width direction with respect to the shoulder land.
Each of the center land and the shoulder land includes a sub-groove, a plurality of blocks separated by the sub-groove, and a sipe.
The sipe area ratio Ace, which is the ratio of the area on the tread of the sipe to the land area on the tread on the center land, and the sipe area, which is the ratio of the area on the tread of the sipe to the land area on the tread on the shoulder land. A pneumatic tire having a ratio of Ash of 2% or more and 15% or less and satisfying the relationship of Ace> Ash. The sipe volume ratio Vce, which is the ratio of the volume of the sipe to the land volume from the tread to the bottom of the main groove on the center land, and the ratio of the volume of the sipe to the land volume from the tread to the bottom of the main groove on the shoulder land. The pneumatic tire according to claim 1, wherein the sipe volume ratio Vsh is 1% or more and 12% or less, and satisfies the relationship of Vce> Vsh. The sipe volume ratio Vce on the center land, the sipe volume ratio Vsh on the shoulder land, the sipe area ratio Ace on the center land, and the sipe area ratio Ash on the shoulder land are:
The pneumatic tire according to claim 2, which satisfies the relationship of (Vce / Vsh)> (Ace / Ash). The sipe includes a first sipe, a second sipe, and a third sipe.
The first sipe extends in the tire circumferential direction at the central portion of the block in the tire width direction and divides the block in the tire width direction.
The second sipe extends in the tire width direction and is blocked in the block.
The third sipe has a first end extending in the tire width direction at the central portion of the block in the tire circumferential direction and closing in the block and a second end opening in the tire width direction end of the block. The pneumatic tire according to any one of 1 to 3. The pneumatic tire according to claim 4, wherein the width of the first sipe is thicker than the width of the third sipe, and the width of the third sipe is thicker than the width of the second sipe.

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