JP2013216271A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire configured to improve uneven wear resistance of the tire.SOLUTION: A pneumatic tire 1 includes blocks 51-53 each having sipes 61-63. Three blocks 51-53 adjacent to each other in a tire circumferential direction have different contact areas S1, S2, and S3, respectively. Each of the blocks 51-53 has a sipe formed of either or both two-dimensional sipe component and three-dimensional sipe component. In the blocks 51-53, a block 53 having larger contact area Sk has longer sipe lengths L1, L2, and L3, and larger ratios A1, A2, and A3 of the two-dimensional sipe component to the sipe length Lk.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of improving the uneven wear resistance performance of the tire.

  In recent pneumatic tires, a pitch variation structure in which a plurality of blocks adjacent to each other in the tire circumferential direction have different circumferential lengths (pitch lengths) is employed for the purpose of reducing tire pattern noise. In such a configuration, since the rigidity of each block is different, there is a problem that uneven wear tends to occur in the block. As a conventional pneumatic tire related to such a problem, a technique described in Patent Document 1 is known.

JP 2009-119922 A

  Therefore, the present invention has been made in view of the above, and an object thereof is to provide a pneumatic tire capable of improving the uneven wear resistance performance of the tire.

  In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire including a plurality of blocks each having a sipe, and a predetermined number N of blocks adjacent to each other in the tire circumferential direction are different from each other. Each of the N blocks has an area Sk (k = 1, 2,..., N) and a sipe composed of one or both of a two-dimensional sipe component and a three-dimensional sipe component. The block having the ground contact area Sk has a longer sipe length Lk (k = 1, 2,..., N) and a ratio Ak (k = 1, 2) of the two-dimensional sipe component to the sipe length Lk. ,..., N) are large.

  In the pneumatic tire according to the present invention, of the N blocks adjacent in the tire circumferential direction, the smaller the sipe length Lk, the smaller the sipe length Lk, and the smaller the two-dimensional sipe component ratio Ak relative to the sipe length Lk. The larger the block, the longer the sipe length Lk, and the larger the two-dimensional sipe component ratio Ak relative to the sipe length Lk. Therefore, there is an advantage that the rigidity of each block is made uniform and the uneven wear resistance performance of the tire is improved.

FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a plan view showing a tread surface of the pneumatic tire depicted in FIG. 1. FIG. 3 is an explanatory diagram illustrating an example of a three-dimensional sipe component. FIG. 4 is an explanatory diagram illustrating an example of a three-dimensional sipe component. FIG. 5 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire 1 according to an embodiment of the present invention. The figure shows a radial tire for a passenger car as an example of the pneumatic tire 1. Reference sign CL is a tire equator plane.

  The pneumatic tire 1 is applied to, for example, a studless tire, a summer tire, and the like. The pneumatic tire 1 includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, and a pair of sidewall rubbers 16, 16. A pair of bead rubbers 17 and 17 is provided (see FIG. 1).

  The pair of bead cores 11 and 11 has an annular structure and constitutes the core of the left and right bead portions. The pair of bead fillers 12 and 12 are disposed on the outer periphery in the tire radial direction of the pair of bead cores 11 and 11 to reinforce the bead portion.

  The carcass layer 13 has a single-layer structure and is bridged in a toroidal shape between the left and right bead cores 11 and 11 to constitute a tire skeleton. Further, both end portions of the carcass layer 13 are wound and locked outward in the tire width direction so as to wrap the bead core 11 and the bead filler 12. The carcass layer 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material (for example, nylon, polyester, rayon, etc.) with a coating rubber and rolling them, and has an absolute value of 85 [deg] or more and 95. [Deg] The following carcass angle (inclination angle in the fiber direction of the carcass cord with respect to the tire circumferential direction).

  The belt layer 14 is formed by laminating a pair of cross belts 141 and 142 and a belt cover 143, and is arranged around the outer periphery of the carcass layer 13. The pair of cross belts 141 and 142 is formed by rolling a plurality of belt cords made of steel or organic fiber material with a coating rubber, and having a belt angle of 10 [deg] or more and 30 [deg] or less in absolute value. Have. Further, the pair of cross belts 141 and 142 have belt angles with different signs from each other (inclination angle of the fiber direction of the belt cord with respect to the tire circumferential direction), and are laminated so that the fiber directions of the belt cords cross each other. (Cross ply structure). The belt cover 143 is formed by rolling a plurality of belt cords made of steel or organic fiber material with a coat rubber, and has a belt angle of 10 [deg] or more and 45 [deg] or less in absolute value. Further, the belt cover 143 is disposed so as to be laminated on the outer side in the tire radial direction of the cross belts 141 and 142.

  The tread rubber 15 is disposed on the outer circumference in the tire radial direction of the carcass layer 13 and the belt layer 14 to constitute a tread portion of the tire. The pair of side wall rubbers 16 and 16 are respectively arranged on the outer side in the tire width direction of the carcass layer 13 to constitute left and right side wall portions. The pair of bead rubbers 17, 17 are arranged on the outer sides in the tire width direction of the left and right bead cores 11, 11 and the bead fillers 12, 12 to constitute left and right bead portions.

  FIG. 2 is a plan view showing a tread surface of the pneumatic tire 1 shown in FIG. 1. The figure schematically shows a general block pattern. Note that the symbol T indicates a tire ground contact end.

  The pneumatic tire 1 includes a plurality of circumferential main grooves 2 extending in the tire circumferential direction, a plurality of land portions 31 and 32 partitioned by the circumferential main grooves 2, and a tire width direction. The tread portion includes a plurality of lug grooves 4 crossing the land portions 31 and 32 (see FIG. 2).

  For example, in the configuration of FIG. 2, the two circumferential main grooves 2 and 2 are arranged symmetrically about the tire equatorial plane CL. The circumferential main grooves 2 and 2 define a row of center land portions 31 and a pair of left and right shoulder land portions 32 and 32. All the land portions 31 and 32 have a plurality of lug grooves 4 extending in the tire width direction. The lug grooves 4 have an open structure that crosses the land portions 31 and 32 in the tire width direction, and are arranged at predetermined intervals in the tire circumferential direction. Thereby, all the land parts 31 and 32 become the block row | line | column divided | segmented into the some blocks 51-53.

  Each of the blocks 51 to 53 has a plurality of sipes 61 to 63 (see FIG. 2). Further, each sipe 61 to 63 has a grown structure that terminates in the blocks 51 to 53. However, the present invention is not limited to this, and each of the sipes 61 to 63 may have an open structure that penetrates the blocks 51 to 53, or may have a semi-closed structure that terminates in the blocks 51 to 53 at one end. It may be done (not shown).

  In addition, the circumferential direction main groove means the circumferential direction groove | channel which has a groove width of 3.0 [mm] or more. The lug groove means a lateral groove having a groove width of 1.6 [mm] or more. These groove widths are measured excluding notches and chamfers formed in the groove openings. A sipe is a cut formed in a land portion and generally has a sipe width of less than 1.5 [mm].

[Block contact area and sipe length]
Further, in this pneumatic tire 1, a predetermined number N (N = 3 in FIG. 2) of blocks 51 to 53 arranged in the same land portion 31 (32) and adjacent in the tire circumferential direction are different from each other. It has a ground contact area Sk (k = 1, 2,..., N).

  The ground contact area Sk of the blocks 51 to 53 is obtained when the tire is mounted on the specified rim and applied with the specified internal pressure, and is placed perpendicular to the flat plate in a stationary state and applied with a load corresponding to the specified load. It is measured at the contact surface between the tire and the flat plate.

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

  For example, in the configuration of FIG. 2, the center land portion 31 and the left and right shoulder land portions 32, 32 have unit patterns each including three types (N = 3) of blocks 51 to 53. Are repeatedly arranged in the tire circumferential direction. Further, the three types of blocks 51 to 53 in one unit pattern have different ground contact areas S1 to S3. Specifically, the three types of blocks 51 to 53 have different circumferential lengths (pitch lengths) P1 to P3, and are arranged in the order of small blocks, medium blocks, and large blocks. Thereby, a block pattern having a pitch variation is formed.

  In the configuration of FIG. 2, the circumferential lengths P1, P2, and P3 of the blocks 51 to 53 adjacent in the tire circumferential direction are set within a range of 15 [mm] to 40 [mm].

  Moreover, in this pneumatic tire 1, in the N blocks 51 to 53 adjacent in the tire circumferential direction, the sipe length Lk (k = 1, 2,..., N) is increased as the block having a larger ground contact area Sk. Is long (see FIG. 2). Thereby, the relationship between the ground contact areas S1 to S3 of the blocks 51 to 53 and the sipe lengths L1 to L3 is optimized, and the block rigidity is made uniform.

  The sipe length Lk of the block is calculated as the total length of the sipe within the contact surface of the block. Therefore, when one block has a plurality of sipes, the total length of sipes in this block is calculated as the sipe length Lk of the block. The length of the sipe is measured as a distance between both ends of the sipe on the block tread. In addition, the sipe length Lk of each block 51-53 can be suitably selected according to the specification of a tire, etc.

  Further, the contact area Sk (k = 1, 2,..., N) in an arbitrary block and the sipe length Lk (k = 1, 2,..., N) of the sipe in the contact surface of the block. ) And the ratio Lk / Sk is called the sipe density.

  At this time, the ratio between the maximum value and the minimum value of the sipe density Lk / Sk of each of the blocks 51 to 53 adjacent in the tire circumferential direction is preferably in the range of 1.0 or more and 2.0 or less. Thereby, the sipe density Lk / Sk of each block 51-53 is made more uniform, and the rigidity of each block 51-53 is made uniform. In addition, the sipe density Lk / Sk of each block 51-53 can be suitably selected according to the specification etc. of a tire.

  For example, in the configuration of FIG. 2, in three types of blocks 51 to 53 adjacent in the tire circumferential direction, the sipe lengths L1 to L3 are set to be longer as the ground contact areas S1 to S3 are larger. That is, the sipe length L2 of the middle block 52 is longer than the sipe length L1 of the small block 51, and the sipe length L3 of the large block 53 is longer than the sipe length L2 of the middle block 52 (S1 < S2 <S3 and L1 <L2 <L3). Specifically, each block 51 to 53 has the number of sipes 61 to 63 corresponding to the circumferential lengths P1 to P3, whereby the circumferential lengths P1 to P3 and the sipe length L1 of each block 51 to 53 are determined. The relationship with ~ L3 is adjusted.

  At this time, the sipe density L1 / S1 of the block 51 having the circumferential length P1, the sipe density L2 / S2 of the block 52 having the circumferential length P2, and the sipe density L3 / S3 of the block 53 having the circumferential length P3 Is set within the above range (1.0 or more and 2.0 or less) and is made uniform. Thereby, the rigidity of each block 51-53 is equalized (L1 / S1 = L2 / S2 = L3 / S3). Further, the center land portion 31 and the left and right shoulder land portions 32 and 32 have the above-described configuration, so that the rigidity of the blocks 51 to 53 is made uniform for each land portion 31 and 32.

[Distribution ratio of 2D and 3D sipes]
In the pneumatic tire 1, as described above, the rigidity of the blocks 51 to 53 is substantially uniformed by uniformizing the sipe density Lk / Sk of the blocks 51 to 53 adjacent to each other in the tire circumferential direction. Yes.

  However, even between the blocks 51 to 53 in the same land portion 31 (32), the rigidity of each of the blocks 51 to 53 can be appropriately equalized only by uniformizing the sipe density Lk / Sk. Is difficult. This is because the influence of the rigidity difference between the blocks 51 to 53 is large. On the other hand, if the sipe density Lk / Sk of each of the blocks 51 to 53 is not uniform, it is not preferable because it becomes more difficult to make the block rigidity uniform.

  Therefore, in this pneumatic tire 1, the sipe density Lk / Sk of each block 51 to 53 is made uniform as described above, and the rigidity of each block 51 to 53 is appropriately made uniform by adopting the following configuration. (See FIG. 2).

  First, in the pneumatic tire 1, the sipes 61 to 63 of the respective blocks 51 to 53 are composed of one or both of a two-dimensional sipe component and a three-dimensional sipe component. In FIG. 2, the thin lines of the sipes 61 to 63 indicate the two-dimensional sipe part, and the thick lines indicate the three-dimensional sipe part.

  The two-dimensional sipe component is a sipe component having a straight sipe wall surface in a cross-sectional view perpendicular to the sipe length direction. The three-dimensional sipe component is a sipe component having a sipe wall surface that is bent in the sipe width direction in a cross-sectional view perpendicular to the sipe length direction. Compared with the two-dimensional sipe component, the three-dimensional sipe component has an action of reinforcing the rigidity of the block because the meshing force between the opposing sipe wall surfaces is strong.

  For example, in the configuration of FIG. 2, each of the land portions 31 and 32 is a block row, and all the blocks 51 to 53 include sipes 61 to 63 having both a two-dimensional sipe component and a three-dimensional sipe component, respectively. ing.

  Further, in the blocks 51 to 53 of the center land portion 31, the sipes 61 to 63 have a two-dimensional sipe component at the center portion and three-dimensional sipe components at both ends. And each sipe 61-63 is extended in a tire width direction on the blocks 51-53, and the three-dimensional sipe component of each sipe 61-63 is the circumferential direction main groove 2 side of the blocks 51-53. It is arranged along the edge part. Thereby, the rigidity of the left and right edge parts of each block 51-53 is improved.

  Further, in the blocks 51 to 53 of the shoulder land portion 32, the sipes 61 to 63 have a structure in which a two-dimensional sipe component and a three-dimensional sipe component are connected in series. Each sipe 61-63 extends in the tire width direction with the end on the three-dimensional sipe component side in the tire width direction, so that the three-dimensional sipe component of each sipe 61-63 becomes a block 51-53. Are arranged along the edge portion on the circumferential main groove 2 side. Thereby, the rigidity of the edge part of each block 51-53 in a ground surface is improved.

  In the configuration of FIG. 2, the blocks 51 to 53 adjacent to each other in the tire circumferential direction respectively include only sipes 61 to 63 each having both a two-dimensional sipe component and a three-dimensional sipe component. However, the present invention is not limited to this, and each of the blocks 51 to 53 may include a sipe having only a two-dimensional sipe component or a sipe having only a three-dimensional component (not shown). Further, only a sipe having only a two-dimensional sipe component may be arranged in one block, or only a sipe having only a three-dimensional component may be arranged (not shown).

  Further, the present invention is not limited to the above, and the sipes 61 to 63 may have a three-dimensional sipe component at the center and a two-dimensional sipe component at both ends or one end (not shown).

  Next, in this pneumatic tire 1, the ratio Ak (k = 1, 2,..., N) of the two-dimensional sipe component to the sipe length Lk is larger in the block 53 having a larger ground contact area Sk (FIG. 2). reference). In other words, the block 53 having the larger ground contact area Sk has a smaller ratio of the three-dimensional sipe component to the sipe length Lk.

  The two-dimensional sipe component ratio Ak is calculated as Ak = (length of two-dimensional sipe component) / (sipe length Lk). At this time, the sipe length Lk is equal to Lk = (length of the two-dimensional sipe component) + (length of the three-dimensional sipe component) because the sipe is composed of one or both of the two-dimensional sipe component and the three-dimensional sipe component. )). Further, the length of the two-dimensional sipe component and the length of the three-dimensional sipe component are measured as distances between both ends of each sipe component on the block tread.

  For example, in the configuration of FIG. 2, in the three types of blocks 51 to 53 adjacent in the tire circumferential direction, the two-dimensional sipe component ratios A1 to A3 with respect to the sipe lengths L1 to L3 increase as the ground contact areas S1 to S3 increase. Is set to That is, the two-dimensional sipe component ratio A2 in the middle block 52 is larger than the two-dimensional sipe component ratio A1 in the small block 51, and the two-dimensional sipe component ratio in the large block 53 is larger than the two-dimensional sipe component ratio A2 in the middle block 52. A3 is larger (S1 <S2 <S3 and A1 <A2 <A3). Specifically, the blocks 51 to 53 have two-dimensional sipe component ratios A1 to A3 corresponding to the circumferential lengths P1 to P3, so that the circumferential lengths P1 to P3 and the two-dimensional shapes of the blocks 51 to 53 are two-dimensional. The relationship with the sipe component ratios A1 to A3 is adjusted. Each sipe 61 to 63 has a certain sipe depth.

  The ratio Ak of the two-dimensional sipe component can be set as appropriate depending on the tire specifications. At this time, the ratio Amax / Amin between the maximum value Amax and the minimum value Amin of the two-dimensional sipe component ratio Ak of the blocks 51 to 53 adjacent in the tire circumferential direction is in a range of 1.1 ≦ Amax / Amin ≦ 2.0. It is preferable to be within. Thereby, the range of the two-dimensional sipe component ratio Ak is optimized.

  Further, as the three-dimensional sipe components of the above sipe 61 to 63, configurations as shown in FIGS. 3 and 4 can be adopted. FIG. 3 and FIG. 4 show a transparent perspective view of one side wall surface of the three-dimensional sipe component.

  The three-dimensional sipe shown in FIG. 3 has an opening that is linear or arcuate in plan view of the tread surface of the land. In addition, the three-dimensional sipe has a wave-like shape that repeats bending or bending from one end to the other while gradually increasing the swing width as the sipe depth increases from this opening to at least 80% wear position of the land. Have. Also, at a predetermined sipe depth position, a perpendicular line is drawn from each end of the three-dimensional sipe to the center line passing through the center of the wavy shape of the three-dimensional sipe, and the distance between the legs of these perpendicular lines is sipe. The length is L (not shown). At this time, the sipe length L decreases as the sipe depth increases. In addition, the peripheral length (actual length) of the sipe on the tread of the land portion is M0 [mm], the sipe length L at the 80% wear position is L80 [mm], and the sipe length at the 80% wear position is L80 [mm]. The peripheral length is M80 [mm] (not shown). At this time, the ratio L80 / M0 and the ratio M80 / M0 satisfy the conditions of 0.85 ≦ L80 / M0 ≦ 0.90 and 1.0 ≦ M80 / M0 ≦ 1.15. As such a three-dimensional sipe, for example, a technique described in JP 2006-56502 A is known.

  In addition, the three-dimensional sipe shown in FIG. 4 includes a first offset portion projecting to one side in the sipe width direction and a second offset projecting to the other side in the sipe width direction at a position on the inner side in the tire radial direction from the first offset portion. Part. Further, the sipe length L1 (not shown) when the tire is new and the sipe length L2 (not shown) when 80% wear is substantially the same (0.95 ≦ L2 / L1 ≦ 1.05). ). Further, the sipe peripheral length M1 (not shown) when the tire is new and the sipe peripheral length M2 (not shown) when worn 80% are 1.10 ≦ M2 / M1 ≦ 1.50. Have a relationship. Moreover, the planar shape of the sipe at the time of 80% wear has a parallel portion with respect to the planar shape of the sipe in a new tire. Further, the total length P2 (not shown) of the parallel portion and the sipe length L1 when the tire is new have a relationship of 0.20 ≦ P2 / L1 ≦ 0.80. As such a three-dimensional sipe, for example, a technique described in Japanese Patent Application Laid-Open No. 2009-255688 is known.

[effect]
As described above, the pneumatic tire 1 includes a plurality of blocks 51 to 53 each having sipes 61 to 63 (see FIG. 2). Further, a predetermined number N (N = 3 in FIG. 2) of blocks 51 to 53 adjacent in the tire circumferential direction have different ground contact areas Sk (k = 1, 2,..., N). Further, these blocks 51 to 53 respectively have sipes composed of one or both of a two-dimensional sipe component and a three-dimensional sipe component. In these blocks 51 to 53, the sipe length Lk (k = 1, 2,..., N) is longer in the block 53 having the larger ground contact area Sk, and the two-dimensional sipe with respect to the sipe length Lk. The component ratio Ak (k = 1, 2,..., N) is large.

  In such a configuration, in the N blocks 51 to 53 adjacent in the tire circumferential direction, the smaller the sipe length Lk, the smaller the sipe length Lk, and the smaller the two-dimensional sipe component ratio Ak to the sipe length Lk. The larger the block 53, the longer the sipe length Lk, and the larger the two-dimensional sipe component ratio Ak with respect to the sipe length Lk. Therefore, there is an advantage that the rigidity of the small block 51 is secured and the dry performance of the tire is improved. Moreover, the rigidity of each block 51-53 is equalized, and there is an advantage that the uneven wear resistance performance of the tire is improved.

  In particular, in the above configuration, since both the sipe length Lk and the two-dimensional sipe component ratio Ak of each block 51 to 53 are adjusted according to the ground contact area Sk of each block 51 to 53, each block 51 to 53 is adjusted. There is an advantage that the rigidity of the is more uniform.

  Moreover, in this pneumatic tire 1, the ratio between the maximum value and the minimum value of the sipe density Lk / Sk in the blocks 51 to 53 adjacent in the tire circumferential direction is within a range of 1.0 or more and 2.0 or less. Yes (see FIG. 2). In such a configuration, there is an advantage that the rigidity of each block 51 to 53 is effectively equalized by equalizing the sipe density Lk / Sk of the blocks 51 to 53 adjacent in the tire circumferential direction.

  In the pneumatic tire 1, the ratio Amax / Amin between the maximum value Amax and the minimum value Amin of the two-dimensional sipe component ratio Ak in the blocks 51 to 53 adjacent in the tire circumferential direction is 1.1 ≦ Amax. /Amin≦2.0 (see FIG. 2). In such a configuration, the two-dimensional sipe component ratio Ak of each of the blocks 51 to 53 is made uniform, so that there is an advantage that the dry performance and uneven wear resistance performance of the tire are effectively improved. That is, since 1.1 ≦ Amax / Amin, a difference occurs in the two-dimensional sipe component ratio Ak of each of the blocks 51 to 53, and the rigidity of each of the blocks 51 to 53 can be made uniform appropriately. Further, when Amax / Amin ≦ 2.0, the block rigidity is appropriately ensured and the tire dry performance is ensured.

  In the pneumatic tire 1, the circumferential length Pk (k = 1, 2,..., N) of the blocks 51 to 53 adjacent in the tire circumferential direction is 15 [mm] ≦ Pk ≦ 40. It is in the range of [mm] (see FIG. 2). In such a configuration, since the range of the circumferential length Pk of the blocks 51 to 53 is optimized, there is an advantage that the dry performance and uneven wear resistance performance of the tire are appropriately ensured.

  Moreover, in this pneumatic tire 1, the sipes 61 to 63 have both a two-dimensional sipe component and a three-dimensional sipe component, and have a three-dimensional sipe component at least at one end (see FIG. 2). In such a configuration, the sipe 61 to 63 has a three-dimensional sipe component at the end, so that the three-dimensional sipe component is arranged on the edge side of the blocks 51 to 53. Thereby, the rigidity of the blocks 51-53 is improved and there exists an advantage which the dry performance of a tire improves.

  FIG. 5 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  In this performance test, evaluations on (1) dry performance and (2) uneven wear resistance performance were performed on a plurality of different pneumatic tires (see FIG. 5). In this performance test, a pneumatic tire having a tire size of 225 / 40R18 is assembled to a rim having a rim size of 18 × 7.5 J, and an air pressure of 260 [kPa] and a maximum load specified by JATMA are applied to the pneumatic tire. The pneumatic tire is mounted on a test vehicle of a displacement 2.0 [L], a front engine front drive (FF) and a hatchback type.

  (1) In the evaluation on dry performance, the test vehicle runs on the test course at a traveling speed of up to 200 km / h, and a specialized test driver evaluates the driving stability such as lane change performance and cornering performance. Do. This evaluation is performed by index evaluation using the conventional example as a reference (100), and the larger the value, the better.

  (2) In the evaluation regarding the uneven wear resistance performance, the test vehicle travels 500 laps at the maximum lateral acceleration 0.8 [G] of the turning place on the 8-turn circuit of 90 [m] per lap. Thereafter, the amount of uneven wear of the tire is measured and index evaluation is performed. This evaluation is performed by index evaluation using the conventional example as a reference (100), and the larger the value, the better.

  The pneumatic tire 1 of Examples 1 to 7 has the configuration shown in FIGS. 1 and 2, and the center land portion 31 and the left and right shoulder land portions 32 and 32 are large, medium, and small adjacent in the tire circumferential direction. Three types of blocks 51 to 53 are each configured as a unit pattern. Moreover, the sipe depth of each sipe 61-63 is 3 [mm]. Also, in the pneumatic tire 1 of Example 8, each sipe 61 to 63 has a three-dimensional sipe component at the center and a two-dimensional sipe component at the end as compared with the pneumatic tire of Example 1. It is different in having.

  In the pneumatic tire of the conventional example, in the configuration of FIGS. 1 and 2, all sipes are composed only of two-dimensional sipe components. In the pneumatic tire of Comparative Example 1, in the configuration of FIGS. 1 and 2, all sipes are composed only of a three-dimensional sipe component.

  As the test results show, in the pneumatic tires 1 of Examples 1 to 8, it can be seen that the dry performance and uneven wear resistance performance of the tire are improved.

  DESCRIPTION OF SYMBOLS 1 Pneumatic tire, 2 circumferential direction main groove, 31, 32 Land part, 4 Lug groove, 51-53 block, 61-63 Sipe, 11 Bead core, 12 Bead filler, 13 Carcass layer, 14 Belt layer, 141, 142 Intersection Belt, 143 Belt cover, 15 tread rubber, 16 side wall rubber, 17 bead rubber

Claims (5)

A pneumatic tire comprising a plurality of blocks each having a sipe,
The predetermined number N of blocks adjacent to each other in the tire circumferential direction have different ground contact areas Sk (k = 1, 2,..., N) and one of the two-dimensional sipe component and the three-dimensional sipe component. Or each has a sipe consisting of both,
In the N blocks, the sipe length Lk (k = 1, 2,..., N) is longer as the block having a larger ground contact area Sk, and the two-dimensional sipe component with respect to the sipe length Lk. A pneumatic tire characterized in that the ratio Ak (k = 1, 2,..., N) is large. When the ratio Lk / Sk between the contact area Sk of any block and the sipe length Lk of the sipe in the contact surface of the block is referred to as sipe density,
The pneumatic tire according to claim 1, wherein a ratio between a maximum value and a minimum value of the sipe density Lk / Sk in the N blocks is in a range of 1.0 or more and 2.0 or less.   The ratio Amax / Amin between the maximum value Amax and the minimum value Amin of the ratio Ak of the two-dimensional sipe components in the N blocks is in a range of 1.1 ≦ Amax / Amin ≦ 2.0. 2. The pneumatic tire according to 2.   The circumferential length Pk (k = 1, 2,..., N) of the N blocks is in a range of 15 [mm] ≦ Pk ≦ 40 [mm]. The pneumatic tire according to one.   The pneumatic tire according to any one of claims 1 to 4, wherein the sipe has both the two-dimensional sipe component and the three-dimensional sipe component and has the three-dimensional sipe component at at least one end. .