JP2021187262A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire capable of inhibiting wear of adjacent-block-integrated-type block, as well as, improving linearity of steering stability.SOLUTION: At least one sipe 34 extending in a tire width direction is arranged in each block-shaped land portion 32 of a shoulder land portion, and each block-shaped land portion 32 is divided into a plurality of small blocks 35 by each sipe 34. When a number of the small blocks 35 on a tire circumference is defined to be X, and division distances Si (i=1 to X) of the small blocks 35 in a tire circumference direction at a reference position P of 50% from an inner end Es toward a ground contact end E in a tire width direction of the sipe 34 are defined to be S1, S2,...SX sequentially along the tire circumferential direction, the small blocks 35 that satisfy a relationship of 1.00≤max (Si, Si+1)/min (S i), Si+1)≤1.10 account for 50% or more of the X small blocks on the tire circumference.SELECTED DRAWING: Figure 3

Description

The present invention relates to a pneumatic tire having a block-based shoulder land portion in the tread portion, and more specifically, a pneumatic tire capable of suppressing wear of an adjacent block integrated type and improving the linearity of steering stability. Regarding.

In a pneumatic tire having a block-based shoulder land portion in the tread portion, pitch variation is adopted in the tread pattern in order to reduce pattern noise (see, for example, Patent Documents 1 to 5). In such a pneumatic tire, a difference in rigidity is generated between blocks adjacent to each other in the tire circumferential direction. If the difference in rigidity between blocks adjacent to each other in the tire circumferential direction is excessive, the linearity of steering stability deteriorates due to the fluctuation of the block rigidity in the ground contact surface. That is, the linear feeling in the correspondence between the steering wheel steering and the reaction of the vehicle is disturbed.

On the other hand, in an area where a running pattern with almost no acceleration / deceleration is frequently repeated, a special form of wear (hereinafter referred to as a form of wear) in which blocks adjacent to the tire circumferential direction are integrally worn at the shoulder portion inside the vehicle mounting of pneumatic tires. , "Adjacent block integrated wear") may occur. Such adjacent block integrated wear tends to be promoted when the difference in rigidity between adjacent blocks in the tire circumferential direction is large.

Japanese Unexamined Patent Publication No. 7-156615 Japanese Unexamined Patent Publication No. 7-156614 Japanese Unexamined Patent Publication No. 8-20205 Japanese Unexamined Patent Publication No. 10-166817 Japanese Unexamined Patent Publication No. 2015-120449

An object of the present invention is to provide a pneumatic tire capable of suppressing wear of an integral block of adjacent blocks and improving the linearity of steering stability.

The pneumatic tire of the present invention for achieving the above object is provided with a shoulder land portion divided by a circumferential groove having a groove width of 3 mm or more in a tread portion, and the groove width of 2 mm or more extending in the tire width direction. In a pneumatic tire containing a plurality of lug grooves and a plurality of block-shaped land portions partitioned by these lug grooves.
At least one sipe extending in the tire width direction is arranged in each block-shaped land portion of the shoulder land portion, and each block-shaped land portion is divided into a plurality of small blocks by the at least one sipe, and the small blocks are divided into a plurality of small blocks. _{Let X be the number on the tire circumference, and the division distance S i} (i = 1 to X) in the tire circumference direction of the small block at a reference position of 50% from the inner end in the tire width direction of the sipe toward the ground contact end of the tire. _{When S 1} , S ₂ , ... S _X are set in order along the circumferential direction, 1.00 ≤ max (S _i , S _{i + 1} ) / min (S _i , S _{i + 1} ) ≤ 1. It is characterized in that the number of small blocks satisfying the relationship of 10 is 50% or more of the X small blocks on the tire circumference.

In the present invention, at least one sipe extending in the tire width direction is arranged in each block-shaped land portion of the shoulder land portion, and each block-shaped land portion is divided into a plurality of small blocks by the sipes, and the tire circumference of the small block is formed. _{Let X be the number of tires, and set the division distance S i} (i = 1 to X) in the tire circumferential direction of the small block at a reference position of 50% from the inner end in the tire width direction of the sipe toward the ground contact end along the tire circumferential direction. When S ₁ , S ₂ , ... S _X are set in order, the relationship of 1.00 ≤ max (S _i , S _{i + 1} ) / min (S _i , S _{i + 1} ) ≤ 1.10 is satisfied. Since the small blocks to be formed are 50% or more of the X small blocks on the tire circumference, the rigidity of the small blocks constituting the block-shaped land portion of the shoulder land portion is made uniform, and the specific small blocks are preferentially worn. Since this is suppressed, it is possible to suppress the wear of the adjacent block integrated type. In addition, by subdividing the block-shaped land part of the shoulder land part into small blocks and equalizing the rigidity of these small blocks, the rigidity fluctuation of the shoulder land part in the ground plane is suppressed and the linearity of steering stability is improved. can do.

In the present invention, S _i / min (S _i-1 , S _{i + 1} ) ≤ 1.10. It is preferable to satisfy the relationship of. As a result, the uniformity of the rigidity of the small blocks is enhanced, so that the wear of the adjacent blocks integrated can be effectively suppressed, and the linearity of the steering stability can be effectively improved.

It is preferable that the ratio S _max / S _{min of the maximum value S max} and the minimum value S _min of the division distance in the tire circumferential direction of the small block is in _{the range of S max} / S _{min ≤ 1.50.} As a result, the non-uniformity of the rigidity of the small blocks is avoided as much as possible, so that the wear of the adjacent blocks integrated can be effectively suppressed and the linearity of the steering stability can be effectively improved.

The number on the tire periphery of the block-shaped land portion and N, P ₁ sequentially circumferential length of the block-shaped land portion in the reference position P _i to (i = 1 to N) along the tire circumferential direction, P _2, ... when the P _N, it is preferable to satisfy the relationship of _{1.00 ≦ P i / min (P} i-1, P i + 1) ≦ 1.30. By defining in this way the circumferential length P _i of the block-shaped land portions adjacent in the tire circumferential direction, reducing the rigidity difference in units of block-shaped land portion, to suppress the adjacent blocks integrated wear can. In addition, it is possible to suppress fluctuations in the rigidity of the shoulder land portion in the ground contact patch and improve the linearity of steering stability.

Further, the number on the tire periphery of the block-shaped land portion and N, P ₁ in order to block-shaped land portion of the circumferential length P _{i (i} = 1~N) at the reference position along the tire circumferential direction, P ₂ , ... P _N, and the number of block-shaped land parts satisfying _{P i} / min (P _i-1 , P _{i + 1 ) ≤ 0.95 is M 1,} and 2 P _i / (P _i-1 + P). When the number of block-shaped land parts satisfying _{i + 1 ) ≤ 0.95 is M 2} and the index R is R = (M ₁ · M ₂ ) ^1/2 / N, the index R is 0 ≤ R ≤ 0. It is preferably in the range of .2. A _{block-shaped land portion that satisfies P i} / min (P _i-1 , P _{i + 1} ) ≤ 0.95 is likely to be the starting point of abnormal wear, and 2P _i / (P _i-1 + P _{i + 1} ) ≤ 0.95. Since abnormal wear tends to progress in the block-shaped land portion that satisfies the condition, by reducing the index R, it is possible to effectively suppress the wear integrated with the adjacent blocks.

The ratio P _max / P _{min of the maximum value P max} and the minimum value P _min of the circumferential length of the block-shaped land is in the range of 1.2 ≤ P _max / P _min ≤ 1.8, and P _i < _{P min · (P max / P} min) 1/3 the sum of the circumferential length of the block-shaped land portion that satisfies the PL, satisfies _{P i> P min · (P} max / P min) 2/3 When the sum of the circumferential lengths of the block-shaped land is PH, the following mathematical formulas (1) and (2) can be satisfied, and the relationship of 0.4 ≦ PH / PL ≦ 3.0 can be satisfied. preferable.

As a result, the circumferential length of the block-shaped land portion is dispersed so as not to be biased to a specific circumferential length, so that the adjacent block integrated wear can be enjoyed while enjoying the effect of improving noise performance based on the pitch variation. It is possible to improve the linearity of steering stability while suppressing the noise.

It is preferable that the lug groove on the shoulder land portion does not communicate with the circumferential groove. As a result, the rigidity of each block-shaped land portion of the shoulder land portion is increased, so that the wear of the adjacent block integrated can be suppressed.

The JIS-A hardness of the cap tread rubber layer arranged in the tread portion is in the range of 60 to 80, and the number of sipes arranged in each block-shaped land portion of the shoulder land portion is preferably 4 or less. As a result, the rigidity of each block-shaped land portion of the shoulder land portion is increased, so that the linearity of steering stability can be effectively improved.

In the present invention, the ground contact end of the tread portion is a tire shaft in a ground contact shape measured under the condition that the tire is rim-assembled on a regular rim, placed vertically on a flat surface with a regular internal pressure applied, and a regular load is applied. This is the outermost position in the direction. A "regular rim" is a rim defined for each tire in a standard system including a standard on which a tire is based. For example, a standard rim for JATTA, "DesignRim" for TRA, or ETRTO. If so, it is set to "Measuring Rim". The "normal internal pressure" is 230 kPa. The "regular load" is a load equivalent to 75% of the maximum load capacity defined for each tire in the standard system including the standard on which the tire is based.

It is a cross-sectional view of the meridian which shows the pneumatic tire which comprises embodiment of this invention. It is a developed view which shows the tread pattern of the pneumatic tire of FIG. It is a top view which shows the main part of FIG. 2 in an enlarged manner. FIG. 3 is a cross-sectional view taken along the line IV-IV in FIG. It is a side view which shows the typical adjacent block integrated wear which occurs in the block-shaped land part.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 4 show a pneumatic tire according to an embodiment of the present invention. In FIG. 1, CL is the tire center position. In FIG. 2, E is the grounding end.

As shown in FIG. 1, the pneumatic tire of the present embodiment has a tread portion 1 extending in the tire circumferential direction and forming an annular shape, and a pair of sidewall portions 2 and 2 arranged on both sides of the tread portion 1. And a pair of bead portions 3 and 3 arranged inside the sidewall portions 2 in the tire radial direction.

A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the radial direction of the tire, and is folded back from the inside to the outside of the tire around the bead core 5 arranged in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross section is arranged on the outer periphery of the bead core 5.

On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to intersect each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set to, for example, in the range of 10 ° to 40 °. As the reinforcing cord of the belt layer 7, a steel cord is preferably used. At least one belt cover layer 8 having reinforcing cords arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is arranged on the outer peripheral side of the belt layer 7 for the purpose of improving high-speed durability. There is. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

The above-mentioned tire internal structure shows a typical example of a pneumatic tire, but is not limited thereto. Further, a cap tread rubber layer 1A is arranged in the tread portion 1, a sidewall rubber layer 2A is arranged in each of the sidewall portions 2, and a rim cushion rubber layer 3A is arranged in each of the bead portions 3. ..

As shown in FIG. 2, a plurality of main grooves 10 extending in the tire circumferential direction are formed in the tread portion 1. The main groove 10 is a circumferential groove having a groove width of 3 mm or more, preferably 4 mm or more and 10 mm or less, and a groove depth of 6 mm or more and 11 mm or less. The main groove 10 includes a center main groove 11 located in the vicinity of the tire center position CL and a pair of shoulder main grooves 12 and 12 located on the outermost side in the tire width direction. As a result, the tread portion 1 has a pair of center land portions 20 and 20 located in the center region between the shoulder main grooves 12 and 12 and a pair of center land portions 20 and 20 located in the outer shoulder region of the shoulder main grooves 12 and 12. The shoulder treads 30 and 30 are partitioned.

In each of the center land portions 20, a plurality of closed grooves 21 having one end communicating with the shoulder main groove 12 and the other end ending in the center land portion 20 are formed at intervals in the tire circumferential direction. On the other hand, in each of the shoulder land portions 30, a plurality of lug grooves 31 extending in the tire width direction without communicating with the shoulder main groove 12 are formed at intervals in the tire circumferential direction. The groove width of the lug groove 31 is in the range of 2 mm or more, preferably 3 mm or more and 6 mm or less. Further, the groove depth of the lug groove 31 is preferably in the range of 2 mm or more and 6 mm or less, or in the range of 30% or more and 80% or less of the main groove depth. A plurality of block-shaped land portions 32 are partitioned on the shoulder land portion 30 by the lug groove 31 that satisfies such a dimensional requirement. The block-shaped land portion 32 may be completely divided by the lug groove 31. In particular, it is preferable that the lug groove 31 exists in at least 70% of the region from the inner end Eg in the tire width direction to the ground contact end E of the shoulder land portion 30 on the ground contact end E side. Further, the shoulder land portion 30 is optionally provided with a narrow groove 33 having a groove width of 1 mm or more and 2 mm or less and a groove depth of 10% or more and less than 50% of the maximum depth of the lug groove 31 and extending in the tire circumferential direction. It is formed.

In the above-mentioned pneumatic tire, as shown in FIGS. 3 and 4, at least one sipes 34 extending in the tire width direction are arranged in each block-shaped land portion 32 of the shoulder land portion 30, and each block-shaped land portion is arranged. The portion 32 is divided into a plurality of small blocks 35 by the sipes 34.

Here, a position 50% from the inner end Es in the tire width direction of the sipe 34 toward the ground contact end E, that is, the midpoint of the distance L from the inner end Es in the tire width direction of the sipe 34 to the ground contact end E is the reference position P. And. _{Then, let X be the number of small blocks 35 on the tire circumference, and the division distance S i in} the tire circumference direction of the small block 35 at the reference position P of 50% from the inner end Es in the tire width direction of the sipes 34 toward the ground contact end E. When (i = 1 to X) is S ₁ , S ₂ , ... S _{X in} order along the tire circumferential direction, 1.00 ≤ max (S _i , S _{i + 1} ) / min (S _i). , S _{i + 1} ) The small blocks 35 satisfying the relationship of ≦ 1.10 are set to be 50% or more of the X small blocks 35 on the tire circumference. When i = 1, i-1 = X, and when i = X, i + 1 = 1. Further, the division distance S _i of the small block 35 is specified based on both ends of the block-shaped land portion 32 in the tire circumferential direction and the center line of the sipe 34. For example, when the sipe 34 has a zigzag shape, the division distance S _i of the small block 35 is specified based on the center line of its amplitude.

In the above-mentioned pneumatic tire, at least one sipes 34 extending in the tire width direction are arranged in each block-shaped land portion 32 of the shoulder land portion 30, and each block-shaped land portion 32 is formed into a plurality of small blocks 35 by the sipes 34. The number of small blocks 35 on the tire circumference is X, and the division distance S in the tire circumference of the small block 35 at the reference position P of 50% from the inner end Es in the tire width direction of the sipes 34 toward the ground contact end E. _{When i} (i = 1 to X) is S ₁ , S ₂ , ... S _{X in} order along the tire circumferential direction, 1.00 ≤ max (S _i , S _{i + 1} ) / min (S). _i , S _{i + 1} ) Since the small blocks 35 satisfying the relationship of ≤ 1.10 are 50% or more of the X small blocks 35 on the tire circumference, the block-shaped land portion 32 of the shoulder land portion 30 is formed. Since the rigidity of the constituent small blocks 35 is made uniform and the specific small blocks 35 are prevented from being preferentially worn, it is possible to suppress the wear of the adjacent blocks integrated. Further, by subdividing the block-shaped land portion 32 of the shoulder land portion 30 into small blocks 35 and equalizing the rigidity of these small blocks 35, the rigidity fluctuation of the shoulder land portion 30 in the ground plane is suppressed and the steering is stable. The linearity of sex can be improved.

FIG. 5 shows typical adjacent block integrated wear that occurs in the block-shaped land portion 32. FIG. 5 shows changes over time in _{the wear states W 1 to} W ₅ of the peripheral profile of the block-shaped land portion 32. As shown in FIG. 5, the peripheral profile of the block-shaped land portion 32 _{gradually changes from the wear state W 1} at the time of new product to the wear state W _{5 at the} late stage of wear, but the block-shaped land portion adjacent to the tire circumferential direction. A special form of wear (adjacent block integrated wear) in which the 32s are integrally worn may occur. In the above-mentioned pneumatic tire, the block-shaped land portion 32 of the shoulder land portion 30 is subdivided into small blocks 35, the rigidity of these small blocks 35 is made uniform, and the specific small blocks 35 are suppressed from being preferentially worn. As a result, the wear of the adjacent block is suppressed.

Here, the maximum value max (S _i , S _{i + 1} ) and the minimum value min (S _i , S _{) of the division distances S i} , S _{i + 1} in the tire peripheral direction of the pair of small blocks 35 adjacent to each other in the tire peripheral direction. _If the ratio max (S _i , S _{i + 1} ) / min (S _i , S _{i + 1} ) to i + 1) satisfies the above range, it is less than 50% of the X small blocks 35. Since the effect of equalizing the rigidity of the small block 35 becomes insufficient, the effect of suppressing the wear of the adjacent block integrated is insufficient, and the effect of improving the linearity of steering stability is also insufficient.

In particular, within a specified region of 30% to 70% from the inner end Es in the tire width direction of the sipe 34 toward the ground contact end E (that is, 40% of the distance L from the inner end Es in the tire width direction of the sipe 34 to the ground contact end E). _{It is preferable that the relationship of S i} / min (S _i-1 , S _{i + 1} ) ≤ 1.10 is satisfied at any position of the band-shaped region having a corresponding width and centered on the reference position P). As a result, the uniformity of the rigidity of the small block 35 is enhanced, so that the wear of the adjacent blocks integrated can be effectively suppressed, and the linearity of the steering stability can be effectively improved.

Here, the minimum value min (S _i-1 , _{S i + 1 of the division distance S i in} the tire circumferential direction of any small block 35 _{and the division distance S i-1} and S i + 1 in the tire peripheral direction of the small blocks 35 before and after it. If S i _{+ 1)} the ratio of the _{S i / min (S i-} 1, S i + 1) is outside the above range, the effect of equalizing the rigidity of the small block 35 is lowered, the adjacent blocks integrated wear The effect of suppressing the tires is reduced, and the effect of improving the linearity of steering stability is reduced.

In the above pneumatic tire, the ratio S _max / S _min of _{the maximum value S max} and the minimum value S _min of the division distance in the tire circumferential direction of the small block 35 should be in the range of _{S max} / S _{min ≤ 1.50.} .. In order to achieve such a ratio S _max / S _min , the number of sipes 34 to be arranged in each block-shaped land portion 32 is appropriately determined, and the block-shaped land portion 32 divided into two and the block-shaped portion divided into three. It is good to mix with the land part 32. As a result, the non-uniformity of the rigidity of the small block 35 is avoided as much as possible, so that the wear of the adjacent blocks integrated can be effectively suppressed and the linearity of the steering stability can be effectively improved.

Here, if the ratio S _max / S _{min of the maximum value S max} and the minimum value S _min of the division distance in the tire circumferential direction of the small block 35 deviates from the above range, the effect of equalizing the rigidity of the small block 35 decreases. Therefore, the effect of suppressing the wear of the adjacent block integrated type is reduced, and the effect of improving the linearity of steering stability is reduced.

In the pneumatic tire, the number on the tire periphery of the block-shaped land portion 32 is N, the circumferential length of the block-shaped land portion 32 at the reference position P P _i a (i = 1 to N) along the tire circumferential direction When P ₁ , P ₂ , ... P _N are set in _{order, the relationship of 1.00 ≤ P i} / min (P _i-1 , P _{i + 1} ) ≤ 1.30 should be satisfied. By defining in this way the circumferential length P _i of the block-shaped land portion 32 adjacent in the tire circumferential direction, reducing the rigidity difference in units of block-shaped land portion 32, suppresses neighboring blocks integrated wear be able to. In addition, it is possible to suppress the rigidity fluctuation of the shoulder land portion 30 in the ground contact patch and improve the linearity of steering stability. When i = 1, i-1 = N, and when i = N, i + 1 = 1.

Here, the circumferential length P _i-1 of the circumferential length P _i and the preceding and succeeding blocks shaped land portion 32 of any of the block-shaped land portion 32, P i _{+ 1} of the minimum value min (P _i-1, If P i _{+ 1)} the ratio of the _{P i / min (P i-} 1, P i + 1) is outside the above range, the rigidity difference in units of block-shaped land portion 32 is increased, the adjacent blocks integrated The effect of suppressing wear is reduced, and the effect of improving the linearity of steering stability is reduced.

In the above pneumatic tire, the number on the tire periphery of the block-shaped land portion 32 is N, circumferential length P _{i (i} = 1~N) the tire circumferential direction of the block-shaped land portion 32 at the reference position P _{P 1} , P ₂ , ... P _N are set in order along the above, and the number of block-shaped land parts satisfying _{P i} / min (P _i-1 , P _{i + 1 ) ≤ 0.95 is set to M 1} . When the number of block-shaped land parts satisfying _{2P i} / (P _i-1 + P _{i + 1 ) ≤ 0.95 is M 2} , and the index R is R = (M ₁ · M ₂ ) ^1/2 / N. It is preferable that the index R is in the range of 0 ≦ R ≦ 0.2. When i = 1, i-1 = N, and when i = N, i + 1 = 1.

The index R defined in this way adjusts, for example, _{the ratio of the circumferential length P i} of the adjacent block-shaped land portions 32, or adjusts the number of levels _{of the circumferential length P i} of the block-shaped land portion 32. It can be controlled by changing the arrangement of the block-shaped land portions 32.

A _{block-shaped land portion that satisfies P i} / min (P _i-1 , P _{i + 1} ) ≤ 0.95 is likely to be the starting point of abnormal wear, and 2P _i / (P _i-1 + P _{i + 1} ) ≤ 0.95. Since abnormal wear tends to progress in the block-shaped land portion that satisfies the condition, by reducing the index R, it is possible to effectively suppress the wear integrated with the adjacent blocks. In particular, it is desirable that 0 ≦ R ≦ 0.15. It is also effective to set _{M 2 / N ≦ 0.2.} By reducing M ₂ , the progress of abnormal wear can be effectively suppressed.

In the above pneumatic tire, the ratio P _max / P _{min of the maximum value P max} and the minimum value P _min of the circumferential length of the block-shaped land portion 32 is in the range of 1.2 ≤ P _max / P _min ≤ 1.8. The sum of the circumferential lengths of the block-shaped land 32 that satisfies P _i <P _min · (P _max / P _min ) ^1/3 _{is PL, and P i} > P _min · (P _max / P). _min ) When ^{the sum of the circumferential lengths of the block-shaped land portion 32 satisfying 2/3} is PH, the following mathematical formulas (1) and (2) are satisfied, and 0.4 ≦ PH / PL ≦ 3. It is good to satisfy the relationship of 0.0.

In this way, when applying the pitch variation to the block-shaped land portion 32 of the shoulder land portion 30, the circumferential length of the block-shaped land portion 32 is dispersed so as not to be biased to a specific circumferential length. While enjoying the effect of improving noise performance based on variations, it is possible to suppress wear integrated with adjacent blocks and improve the linearity of steering stability.

Here, the sum total of the circumferential lengths of the block-shaped land portion 32 satisfying _{P i} <P _min · (P _max / P _min ) ^1/3 _{or P i} > P _min · (P _max / P _min ) ^{2 If the total PH of the circumferential length of the block-shaped land portion 32 satisfying / 3} is too large or too small with respect to the whole, the distribution of the circumferential length of the block-shaped land portion 32 becomes biased, which is described above. The improvement effect is reduced. Similarly, when the PH / PL value deviates from the above range, the distribution of the circumferential length of the block-shaped land portion 32 is biased, and the above-mentioned improvement effect is reduced. In particular, it is desirable to satisfy the relationship of 0.7 ≦ PH / PL ≦ 2.0.

In the pneumatic tire, the lug groove 31 of the shoulder land portion 30 is preferably non-communication with the shoulder main groove 12 (circumferential groove having a groove width of 3 mm or more). As a result, the rigidity of each block-shaped land portion 32 of the shoulder land portion 30 is increased, so that wear of the adjacent block integrated type can be suppressed. In FIG. 2, the lug groove 31 communicates with the fine groove 33, but the groove width of the fine groove 33 is 1 mm to 2 mm.

In the pneumatic tire, the JIS-A hardness of the cap tread rubber layer 1A arranged in the tread portion 1 is in the range of 60 to 80, and the sipe 34 arranged in each block-shaped land portion 32 of the shoulder land portion 30. The number is preferably 4 or less. As a result, the rigidity of each block-shaped land portion 32 of the shoulder land portion 30 is increased, so that the linearity of steering stability can be effectively improved.

Here, if the JIS-A hardness of the cap tread rubber layer 1A is less than 60, the effect of improving the linearity of steering stability is reduced due to the decrease in rigidity of the block-shaped land portion 32, and conversely, if it is more than 80, the grip property is reduced. And quietness will decrease. JIS-A hardness is a durometer hardness measured under the condition of a temperature of 20 ° C. using an A type durometer in accordance with JIS-K6253. Further, if the number of sipes 34 arranged in each block-shaped land portion 32 of the shoulder land portion 30 exceeds 4, the effect of improving the linearity of steering stability is reduced due to the decrease in rigidity of the block-shaped land portion 32.

A tire size of 225 / 55R17, the tread portion is provided with a shoulder land portion partitioned by a circumferential groove having a groove width of 3 mm or more, and the shoulder land portion extends in the tire width direction and has a plurality of lug grooves having a groove width of 2 mm or more. _{Max (S i} , S _{i + 1} ) / min (S _i , S _{i + 1} ), S _max / S _min , P _{i in} pneumatic tires including multiple block treads partitioned by lug grooves. / Min (P _i-1 , P _{i + 1} ), index R, P _max / P _min , value of formula (1), value of formula (2), PH / PL, communication of lug groove to shoulder main groove or The tires of the conventional example and Examples 1 to 11 in which the hardness (JIS-A hardness) of the non-communication cap tread rubber layer was set as shown in Table 1 were manufactured.

For these test tires, the linearity of uneven wear resistance and steering stability was evaluated by the following test method, and the results are also shown in Table 1.

Uneven wear resistance:
After assembling each test tire to a wheel with a rim size of 17 x 7.5J and mounting it on a front-wheel drive vehicle with a displacement of 2 liters, setting the air pressure to 220 kPa and running 20,000 km on a dry road surface, the inside of each of the four wheels The circumference profile at the reference position was measured for the land part of the shoulder, the points where the adjacent block integrated wear occurred, and the total number of four wheels was calculated. The evaluation results are shown by an index of 100 in the conventional example using the reciprocal of the total number of wear occurrence points. The larger this index value is, the less the places where the adjacent block integrated wear is generated, which means that the uneven wear resistance is excellent.

Linearity of steering stability:
Each test tire is attached to a wheel with a rim size of 17 x 7.5J, mounted on a front-wheel drive vehicle with a displacement of 2 liters, filled with the specified air pressure of the vehicle, and a running test is conducted by a panelist on a test course consisting of paved roads. Then, a sensory evaluation was performed on the linearity of steering stability. The evaluation results are shown by an index of 100 in the conventional example. The larger the index value, the better the linearity of steering stability.

As can be seen from Table 1, in the tires of Examples 1 to 11, the adjacent block integrated wear was suppressed and the linearity of steering stability was improved in comparison with the conventional example.

1 Tread part 2 Side wall part 3 Bead part 10 Main groove (circumferential groove)
11 Center main groove 12 Shoulder main groove 20 Center land part 21 Closing groove 30 Shoulder land part 31 Rug groove 32 Block-shaped land part 33 Fine groove 34 Sipe 35 Small land part Es Sipe tire width inner end E Grounding end P Reference position

Claims (8)

The tread portion is provided with a shoulder land portion partitioned by a circumferential groove having a groove width of 3 mm or more, and the shoulder land portion extends in the tire width direction and has a plurality of lug grooves having a groove width of 2 mm or more and a plurality of lug grooves partitioned by these lug grooves. In pneumatic tires, including block-shaped land areas
At least one sipe extending in the tire width direction is arranged in each block-shaped land portion of the shoulder land portion, and each block-shaped land portion is divided into a plurality of small blocks by the at least one sipe, and the small blocks are divided into a plurality of small blocks. _{Let X be the number on the tire circumference, and the division distance S i} (i = 1 to X) in the tire circumference direction of the small block at a reference position of 50% from the inner end in the tire width direction of the sipe toward the ground contact end of the tire. _{When S 1} , S ₂ , ... S _X are set in order along the circumferential direction, 1.00 ≤ max (S _i , S _{i + 1} ) / min (S _i , S _{i + 1} ) ≤ 1. A pneumatic tire characterized in that the number of small blocks satisfying the relationship of 10 is 50% or more of the X small blocks on the tire circumference. The relationship of S _i / min (S _i-1 , S _{i + 1} ) ≤ 1.10. The pneumatic tire according to claim 1, wherein the tire is satisfied. Claim 1 is characterized in that the ratio S _max / S _{min of the maximum value S max} and the minimum value S _min of the division distance in the tire circumferential direction of the small block is in the range of S _max / S _{min ≤ 1.50.} Or the pneumatic tire according to 2. It said block-shaped land portion, the number on the tire circumference is N in, P ₁ the block-shaped land portion of the circumferential length P _i at the reference position (i = 1 to N) in sequence along the tire circumferential direction, Claims 1 to 3 satisfying the relationship of 1.00 ≤ P _i / min (P _i-1 , P _{i + 1} ) ≤ 1.30 when P ₂ , ... P _N. Pneumatic tires listed in any of. It said block-shaped land portion, the number on the tire circumference is N in, P ₁ the block-shaped land portion of the circumferential length P _i at the reference position (i = 1 to N) in sequence along the tire circumferential direction, P ₂ , ... P _N, and the number of block-shaped land parts satisfying _{P i} / min (P _i-1 , P _{i + 1 ) ≤ 0.95 is M 1,} and 2 P _i / (P _i-1). When the number of block-shaped land parts satisfying + P _{i + 1 ) ≤ 0.95 is M 2} and the index R is R = (M ₁ · M ₂ ) ^1/2 / N, the index R is 0 ≤ R. The pneumatic tire according to any one of claims 1 to 4, wherein the tire is in the range of ≦ 0.2. The ratio P _max / P _{min of the maximum value P max} and the minimum value P _min of the circumferential length of the block-shaped land portion is in the range of 1.2 ≤ P _max / P _{min ≤ 1.8, and}
Let PL be the sum of the circumferential lengths of the block-shaped land that satisfies P _i <P _min · (P _max / P _min ) ^1/3 _{, and P i} > P _min · (P _max / P _min ) ^2/3. When the total length of the block-shaped land portion in the circumferential direction is PH, the following mathematical formulas (1) and (2) are satisfied, and the relationship of 0.4 ≦ PH / PL ≦ 3.0 is satisfied. The pneumatic tire according to any one of claims 1 to 5, characterized in that.

The pneumatic tire according to any one of claims 1 to 6, wherein the lug groove of the shoulder land portion does not communicate with the circumferential groove. The JIS-A hardness of the cap tread rubber layer arranged in the tread portion is in the range of 60 to 80, and the number of sipes arranged in each block-shaped land portion of the shoulder land portion is 4 or less. The pneumatic tire according to any one of claims 1 to 7.

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