JP6612587B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  When the tread rubber is grounded on the road surface, the pneumatic tire is deformed so that the curved tire surface becomes flat. As a result, a force called an in-plane contraction force acting from the outer side in the tire width direction toward the center in the tire width direction acts on the contact surface of the tread rubber.

  Due to the in-plane contraction force as described above, the tread rubber undergoes deformation called wiping deformation along the tire width direction. As a result, the road surface followability decreases and the driving stability on the dry road surface (dry driving stability) Performance) deteriorates.

  Therefore, a pneumatic tire provided with a plurality of three-dimensional sipes on a tread rubber is known (for example, Patent Documents 1 and 2). This three-dimensional sipe has a sipe wall surface that is bent in the sipe width direction in a cross-sectional view perpendicular to the sipe length direction on the tread rubber, and can enhance the rigidity of the tread rubber while ensuring the edge effect and water removal effect. Therefore, wiping deformation of the shoulder region of the tread rubber can be suppressed.

JP 2013-79015 A JP 2013-79017 A

  However, if a three-dimensional sipe as described above is provided, in the center region of the tread rubber, the rigidity of the tread rubber becomes too high due to the three-dimensional sipe described above, and the ground contact area becomes small, so braking performance on ice road surface (ice braking performance) Decreases.

  Then, an object of this invention is to provide the pneumatic tire which can improve dry steering stability performance and ice braking performance.

The pneumatic tire according to the present invention includes a tread rubber, and the tread rubber includes a plurality of first three-dimensional sipes and a plurality of second three-dimensional sipes, and the first three-dimensional sipes have a sipe width of sipe. A sipe wall surface having a shape that is fixed in the depth direction and is bent in the sipe width direction in a cross-sectional view perpendicular to the sipe length direction, wherein the second three-dimensional sipe has a sipe width wider than the surface of the tread rubber. Of the first three-dimensional sipe in a pair of shoulder regions located on the outer side in the tire width direction when the ground contact surface is divided into four equal parts in the tire width direction. The total length is longer than the total surface length of the second three-dimensional sipe, and the total surface length of the second three-dimensional sipe is the center region located between the shoulder regions. Longer than the surface length sum of the first three-dimensional sipes, the rubber hardness of the tread rubber in the shoulder region, a pneumatic tire is greater than a rubber hardness of the tread rubber of the center region, the tread rubber, the tire A plurality of main grooves extending in the circumferential direction; and a plurality of land portions partitioned by the main grooves and provided in the center region, wherein the land portion provided in the center region is the first three-dimensional sipe The second ratio comprising the ratio of the total surface length of the second three-dimensional sipe to the sum of the total surface length of the second three-dimensional sipe is close to the center in the tire width direction. It is a pneumatic tire that is larger in the land.

  According to the present invention, it is possible to improve dry steering stability performance and ice braking performance.

FIG. 1 is a cross-sectional view taken along the tire radial direction of a pneumatic tire according to an embodiment. FIG. 2 is a development view of a main part of the tread rubber surface of the pneumatic tire according to the embodiment. FIG. 3 is a perspective view of the land portion having the first three-dimensional sipe, and is a view cut along the bottom surface of the sipe. FIG. 4 is a side view of a land portion having a first three-dimensional sipe. FIG. 5 is a perspective view of a land portion having a second three-dimensional sipe, cut along the bottom surface of the sipe. FIG. 6 is a side view of a land portion having a second three-dimensional sipe. FIG. 7 is a perspective view of a land portion having a plane sipe and cut along the bottom surface of the sipe. FIG. 8 is a perspective view of a land portion having a sipe according to a modified example, and is a view cut along the bottom surface of the sipe. FIGS. 9A to 9C are developments of main parts of the tread rubber surface illustrating the shoulder region and the center region of the tread rubber. FIG. 10 is a development of a main part of the tread rubber surface of the pneumatic tire according to the example and the comparative example.

  Hereinafter, a pneumatic tire according to an embodiment of the present invention will be described with reference to FIGS. In each figure (the same applies to FIGS. 8 to 10), the dimensional ratio in the drawing does not necessarily match the actual dimensional ratio.

  As shown in FIG. 1, a pneumatic tire (hereinafter also simply referred to as “tire”) 1 according to the present embodiment is a pneumatic radial tire for passenger cars, and includes a tread portion 2 and radially inward from both ends thereof. A pair of left and right sidewall portions 12 that extend and a pair of left and right bead portions 11 provided on the radially inner side of the sidewall portion 12 are provided. An annular bead core 11 a is embedded in the pair of bead portions 11. In the tire 1, at least one carcass ply 13 extending between a pair of bead portions 11 is embedded. In the figure, reference sign S1 indicates a tire equator plane which is a virtual plane passing through the center in the tire width direction B, and reference sign CE indicates a ground contact end.

  The carcass ply 13 extends from the tread portion 2 through the sidewall portion 12 to the bead portion 11, and the bead portion 11 is folded around the bead core 11 a from the inner side to the outer side in the tire axial direction and locked. The carcass ply 13 is formed by arranging carcass cords made of organic fiber cords or the like substantially perpendicular to the tire circumferential direction A. Between the main body of the carcass ply 13 and the folded portion thereof, a bead filler 11b made of hard rubber having a triangular cross section is disposed on the radially outer peripheral side of the bead core 11a.

  An inner liner layer 15 for maintaining air pressure is provided on the tire inner surface side of the carcass ply 13. The inner liner layer 15 is provided over the entire inner surface of the tire.

  A belt 14 is provided on the outer peripheral side (outer side in the tire radial direction) of the carcass ply 13 in the tread portion 2. The belt 14 is provided so as to overlap the outer periphery of the crown portion of the carcass ply 13 and is composed of at least two belt plies.

  The tread portion 2 is provided with a tread rubber 3 that forms a ground contact surface 3a in contact with the road surface. The tread rubber 3 is partitioned into a shoulder region Rs and a center region Rc in the tire width direction B. The shoulder region Rs is a region located on the outer side in the tire width direction when the ground contact surface 3a is equally divided in the tire width direction so that the lengths in the tire width direction B are equal (that is, a region including the ground contact edge CE). And present at both ends in the tire width direction B, respectively. The center region Rc is a region located between a pair of shoulder regions Rs provided at both ends in the tire width direction B (that is, a region including the tire equatorial plane S1), and the length in the tire width direction B is in contact with the center region Rc. An area that is half the length in the tire width direction B of the ground 3a.

  In the tread rubber 3, the tread rubber 3s in the shoulder region Rs and the tread rubber 3c in the center region Rc are formed of rubber compositions having different hardness. Specifically, the rubber hardness (Hs) of the tread rubber 3s in the shoulder region Rs is larger than the rubber hardness (Hc) of the tread rubber 3c in the center region Rc. As an example, the rubber hardness (Hs) of the tread rubber 3s in the shoulder region Rs may be 46 to 70, for example. The rubber hardness (Hc) of the tread rubber 3c in the center region Rc may be 45 to 60, for example. The difference (Hs−Hc) between the two is preferably 1 or more and 15 or less.

  Here, the rubber hardness is a value (durometer hardness) measured with a type A durometer in a 23 ° C. atmosphere in accordance with JIS K6253.

  A method for providing such a hardness difference is not particularly limited. For example, in the rubber composition for forming the tread rubber 3c in the center region Rc and the tread rubber 3s in the shoulder region Rs, the type of rubber component used may be changed. Further, the rubber hardness may be increased by increasing the amount of filler such as carbon black or silica. Moreover, you may raise rubber hardness by increasing a vulcanizing agent or a vulcanization accelerator.

  In this example, as shown in FIG. 1, the tread rubber 3s in the shoulder region Rs is provided so as to approach the belt 14 as the boundary surface with the tread rubber 3c in the center region Rc goes inward in the tire width direction. The tread rubber 3c in the center region Rc is provided so that the boundary surface with the tread rubber 3s in the shoulder region Rs approaches the ground contact surface 3a as it goes outward in the tire width direction. As described above, the boundary surface between the tread rubber 3s and the tread rubber 3c may be provided over both regions across the boundary between the shoulder region Rs and the center region Rc.

  Although not particularly illustrated, a base rubber made of a rubber composition of a different type from the tread rubber 3 may be provided on the inner side in the tire radial direction of the tread rubber 3 over substantially the entire tire width direction.

  The tread rubber 3 has a ground contact surface 3a in which the tire 1 is assembled to the regular rim 100, the tire is placed vertically on a flat road surface filled with the regular internal pressure, and the tread portion that contacts the road surface when a regular load is applied. 2 and the contact point CE is the outermost position in the tire width direction on the contact surface of the tread portion 2 at that time.

  The regular rim is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, a standard rim is used for JATMA, “Design Rim” for TRA, and “Measuring” for ETRTO. Rim ".

  The normal internal pressure is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. If JATMA, the maximum air pressure is measured. If TRA, the table "TIRE LOAD LIMITS AT VARIOUS COLOR PRESSURESURES" If the tire is for a passenger car, it is 180 KPa. In addition, the normal load is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. If it is JATMA, it is the maximum load capacity, and if it is TRA, the maximum load described in the above table. If the value is ETRTO, it is “LOAD CAPACITY”, but if the tire is for a passenger car, the load is 85% of the corresponding load with an internal pressure of 180 KPa.

  The tread rubber 3 includes a plurality of grooves 4 that open to the ground contact surface 3 a and a plurality of land portions 5 that are defined by the grooves 4.

  Specifically, as shown in FIG. 1 and FIG. 2, the tread rubber 3 is provided with four main grooves 4a, 4a, 4b, 4b extending in the tire circumferential direction A at intervals in the tire width direction B. It has been. The main grooves 4a, 4a are center main grooves located in the center region Rc and disposed on both sides of the tire equatorial plane S1. The main grooves 4b and 4b are shoulder main grooves 4b and 4b disposed on the shoulder region Rs on the outer side in the tire width direction of the center main grooves 4a and 4a. Thus, the tread rubber 3 is provided with five land portions 5a, 5b, 5b, 5c, and 5c extending in the tire circumferential direction A.

  Of the five land portions 5a, 5b, 5b, 5c and 5c, the land portion 5a defined between the center main grooves 4a and 4a extends over both sides of the tire equatorial plane S1 so as to straddle the center in the tire width direction B. The center land portion 5a is provided. The center land portion 5a is provided in the center region Rc.

  The land portions 5b and 5b defined between the center main grooves 4a and 4a and the shoulder main grooves 4b and 4b are a pair of mediate land portions 5b and 5b provided outside the center land portion 5a in the tire width direction. . The pair of mediate land portions 5b and 5b are provided over the center region Rc and the shoulder region Rs, and an inner mediate land portion 5b1 provided in the center region Rc and an outer mediate land portion 5b2 provided in the shoulder region Rs It is composed of

  The land portions 5c and 5c defined between the shoulder main grooves 4b and 4b and the ground contact end CE are a pair of shoulder land portions 5c and 5c provided on the outer side in the tire width direction of the outer mediate land portion 5b2. The pair of shoulder land portions 5c, 5c is provided in the shoulder region Rs.

  The land portions 5a, 5b, 5b, 5c, 5c provided in the tread rubber 3 are provided with a plurality of lateral grooves 4c extending in a direction intersecting with the tire circumferential direction A with an interval in the tire circumferential direction A. Yes. The land portions 5a, 5b, 5b, 5c, 5c are divided in the tire circumferential direction A by the lateral grooves 4c, and a plurality of blocks form a block row arranged in the tire circumferential direction A.

  In the tread rubber 3, a plurality of sipes 6 extending in a direction intersecting the tire circumferential direction A are provided on the land portion 5. In the present embodiment, the groove 4 is a recess having a width (gap) on the surface (ground surface 3a) of the tread rubber 3 of 1.8 mm or more, and the sipe 6 is a sipe width (gap) on the surface of the tread rubber 3. Is a recess of less than 1.8 millimeters.

  In the present embodiment, the land portion 5 is provided with a plurality of types of sipes 6, in this example, three types of sipes 6, a first three-dimensional sipes 7, a second three-dimensional sipes 8, and a planar sipes 9. Yes.

  As shown in FIGS. 3 and 4, the first three-dimensional sipe 7 includes a pair of facing sipe wall surfaces 71 and 72 and a sipe bottom surface 73. One sipe wall surface 71 includes a convex portion 71a, and the other sipe wall surface 72 includes a concave portion 72a that is formed so as to accommodate the convex portion 71a while maintaining a constant distance from the convex portion 71a. .

  As a result, the first three-dimensional sipe 7 is provided with a sipe width W11 to W14 constant over the sipe depth direction Z (see FIG. 4), and is perpendicular to the sipe length direction (direction in which the sipe extends in the ground contact surface 3a) X. The curved portion 7 a bent in the sipe width direction Y is formed by the sipe wall surfaces 71 and 72 in a simple cross-sectional view. In this example, the first three-dimensional sipe 7 has an opening opening on the surface of the tread rubber 3 extending in a waveform in the sipe length direction X, and a curved portion 7a provided inside the tread rubber 3 is substantially perpendicular. It is formed to be bent.

  The first three-dimensional sipe 7 has a land portion because the convex portion 71a and the concave portion 72a are engaged with each other between the pair of sipe wall surfaces 71 and 72 facing each other when a load is applied to the tire 1. 5 can be suppressed. Thereby, the rigidity of the land part 5 provided in the tread rubber 3 can be increased.

  The sipe widths W11 to W14 of the first three-dimensional sipe 7 are constant over the sipe depth direction Z, not only when the sipe widths W11 to W14 are all equal, but also to the sipe widths W12 to W14 inside the tread rubber 3. Also included is a case where the sipe width W11 of the surface of the tread rubber 3 is changed within a range of 50% to 150%, preferably within a range of 95% to 105%.

  As shown in FIGS. 5 and 6, the second three-dimensional sipe 8 includes a pair of sipe wall surfaces 81 and 82 that face each other, and a sipe bottom surface 83. One sipe wall surface 81 includes two recesses 81a and 81b, and the other sipe wall surface 82 includes one recess 82a.

  Thereby, the 2nd solid sipe 8 is provided with the wide part 8a-8c of the sipe width W22-W24 wider than the sipe width W21 of the surface of the tread rubber 3 inside the tread rubber 3 (refer FIG. 6). .

  The sipe widths W22 to W24 of the wide portions 8a to 8c are, for example, 150% or more of the sipe width W21 of the surface of the tread rubber 3, and preferably 200% or more. In the present embodiment, the sipe widths W22 to W24 of the wide portions 8a to 8c are all set at equal intervals.

  In this example, the second three-dimensional sipe 8 includes a tread rubber 3 having an opening opening on the surface of the tread rubber 3 extending in a waveform in the sipe length direction X and being not bent in the sipe depth direction Z. It extends linearly in a direction perpendicular to the surface of the tire (tire radial direction).

  In such a second three-dimensional sipe 8, since the wide portions 8a to 8c are provided inside the tread rubber 3, the rigidity of the land portion 5 is lowered and the land portion 5 is easily bent. Moreover, since the deformation | transformation by this load is absorbed by the wide parts 8a-8c when the load acts on the tire 1, the 2nd three-dimensional sipe 8 is that the sipe width W21 of the surface of the tread rubber 3 becomes narrow. Can be suppressed. Thereby, the edge effect and the water removal effect can be ensured.

  As shown in FIG. 7, the plane sipe 9 includes a pair of facing sipe wall surfaces 91 and 92 and a sipe bottom surface 93. The pair of sipe wall surfaces 91 and 92 extend linearly in a direction (tire radial direction) perpendicular to the surface of the tread rubber 3 in a cross-sectional view perpendicular to the sipe length direction X. Further, the pair of sipe wall surfaces 91 and 92 are arranged so as to be parallel to each other. Accordingly, the plane sipe 9 is formed so that the sipe widths W31 and W32 are constant over the sipe depth direction Z.

  The land portion located in the center region Rc of the tread rubber 3, in this example, the center land portion 5 a and the pair of inner mediate land portions 5 b 1 and 5 b 1, has a second three-dimensional sipe 8 that reduces the rigidity of the land portion 5. However, more than the 1st three-dimensional sipe 7 which raises the rigidity of the land part 5 is provided.

  On the other hand, in the land portion located in the shoulder region Rs of the tread rubber, in this example, the pair of outer mediate land portions 5b2, 5b2 and the pair of shoulder land portions 5c, 5c, the first three-dimensional body that increases the rigidity of the land portion 5 is provided. More sipes 7 are provided than the second three-dimensional sipes 8 that reduce the rigidity of the land portion 5.

  Furthermore, at least one of the first three-dimensional sipe 7 and the second three-dimensional sipe 8 and the plane sipe 9 can be provided in the land portion 5 provided in the tread rubber 3. In that case, it is preferable that the total of the first three-dimensional sipe 7 and the second three-dimensional sipe 8 is larger than the planar sipe 9.

  Here, the first three-dimensional sipe 7, the second three-dimensional sipe 8, and the planar sipe 9 provided on the land portion 5 are compared by the total sum of the surface lengths of the sipe. The sum total of the sipe surface length is a sum total of the sipe lengths on the surface of the tread rubber 3 for each sipe.

  Specifically, the lengths of the openings opened on the surface of the tread rubber 3 are measured for all the first three-dimensional sipes 7 provided in the land portions 5a, 5b1, and 5b1 located in the center region Rc of the tread rubber 3. The total length of the measured values is defined as the total surface length L1c of the first three-dimensional sipe 7 in the center region Rc.

  The sum of the surface length of the second three-dimensional sipe 8 and the surface length of the planar sipe 9 in the center region Rc is the land portion 5a, 5b1 located in the center region Rc of the tread rubber 3, as in the first three-dimensional sipe 7. The lengths of the openings opened on the surface of the tread rubber 3 were measured for all the second three-dimensional sipes 8 and the flat sipes 9 provided in 5b1, and all the measured values of the second three-dimensional sipes 8 were added. The length is the total surface length L2c of the second three-dimensional sipe 8 in the center region Rc, and the total length of all the measured values of the planar sipe 9 is the total surface length L3c of the planar sipe 9 in the center region Rc. .

  Further, the sum L1s of the surface lengths of the first three-dimensional sipes 7 in the shoulder region Rs, the sum L2s of the surface lengths of the second three-dimensional sipes 8, and the sum L3s of the surface lengths of the plane sipes 9 are also the center region Rc. As in the case of the sipe, the first three-dimensional sipe 7, the second three-dimensional sipe 8, and the plane sipe 9 provided in the land portions 5b2, 5b2, 5c, and 5c located in the shoulder region Rs of the tread rubber 3. The total length of the surface length L1s of the first three-dimensional sipe 7 in the shoulder region Rs is obtained by measuring the length of the opening that opens on the surface of the tread rubber 3 and adding all the measured values of the first three-dimensional sipe 7. And the total length of the surface of the second three-dimensional sipe 8 in the shoulder region Rs is defined as the total length L2s of the second three-dimensional sipe 8, and the planar sipe 9 is measured. The surface length sum L3s planar sipe 9 and the combined length plus all in the shoulder region Rs.

  As described above, in the tread rubber 3c in the center region Rc, the total surface length L2c of the second three-dimensional sipe 8 is larger than the total surface length L1c of the first three-dimensional sipe 7, and the second three-dimensional sipe 8 is More than one three-dimensional sipe 7 is provided.

  The total surface length L2c of the second solid sipe 8 in the center region Rc of the tread rubber 3 is the sum of the total surface length L1c of the first solid sipe 7 and the total surface length L2c of the second solid sipe 8. It is preferable that it is 51%-100% with respect to (L1c + L2c).

  Further, in the present embodiment, the center land portion 5a and the pair of inner mediate land portions 5b1 and 5b1 provided in the center region Rc have a three-dimensional sipe (provided in the land portion closer to the tire equatorial plane S1). The ratio of the second three-dimensional sipe 8 in the first three-dimensional sipe and the second three-dimensional sipe is large.

  That is, the ratio ρ2a of the second three-dimensional sipe 8 occupying the three-dimensional sipe in the center land portion 5a closest to the tire equator plane S1 is larger than the ratio ρ2b1 and ρ2b1 in the inner mediate land portions 5b1 and 5b1. In that case, it is preferable that the difference (ρ2a−ρ2b1) of the above-described ratio between the land portions adjacent to each other in the tire width direction B is within a range of 5 to 15%.

  Further, the ratio ρ2a of the second three-dimensional sipes 8 occupying the three-dimensional sipes in the center land portion 5a is 100%, that is, only the second three-dimensional sipes of the first three-dimensional sipes 7 and the second three-dimensional sipes are center land portions. 5a is preferably provided. In that case, in addition to the 2nd three-dimensional sipe 8, you may provide the plane sipe 9 in the center land part 5a.

  Here, the ratio ρ2a and the ratio ρ2b1 are expressed by the following equations.

ρ2a = L2ca / (L1ca + L2ca)
ρ2b1 = L2cb1 / (L1cb1 + L2cb1)

  L1ca is the total surface length of the first three-dimensional sipe 7 in the center land portion 5a, L2ca is the total surface length of the second three-dimensional sipe 8 in the center land portion 5a, and L1cb1 is the inner mediate land portion 5b1. The total surface length of the first three-dimensional sipe 7 at L2cb1 is the total surface length of the second three-dimensional sipe 8 in the inner mediate land portion 5b1.

  In the tread rubber 3s in the shoulder region Rs, the total surface length L1s of the first three-dimensional sipe 7 is larger than the total surface length L2s of the second three-dimensional sipe 8, and the first three-dimensional sipe 7 is the second three-dimensional sipe 7. More than sipes 8 are provided.

  The total surface length L1s of the first three-dimensional sipe 7 in the shoulder region Rs of the tread rubber 3 is the sum of the total surface length L1s of the first three-dimensional sipe 7 and the total surface length L2s of the second three-dimensional sipe 8. It is preferable that it is 70%-100% with respect to (L1s + L2s).

  Further, in the present embodiment, the outer mediate land portions 5b2, 5b2 and the shoulder land portions 5c, 5c provided in the shoulder region Rs are closer to the land portion closer to the ground contact CE than the three-dimensional sipes ( The ratio of the first three-dimensional sipe 7 in the first three-dimensional sipe and the second three-dimensional sipe is large.

  That is, the ratio ρ1c of the first three-dimensional sipe 7 occupying the three-dimensional sipe in the shoulder land portions 5c, 5c closest to the ground contact CE is the ratio of the first three-dimensional sipe 7 occupying the three-dimensional sipe in the outer mediate land portion 5b2. Larger than the ratio ρ1b2. In that case, it is preferable that the difference (ρ1c−ρ1b2) between the land portions adjacent to each other in the tire width direction B is within a range of 5 to 15%.

  Here, the ratio ρ1c and the ratio ρ1b2 are expressed by the following equations.

ρ1c = L1sc / (L1sc + L2sc)
ρ1b2 = L1sb2 / (L1sb2 + L2sb2)

  L1sc is the total surface length of the first three-dimensional sipe 7 in the shoulder land portions 5c and 5c, L2sc is the total surface length of the second three-dimensional sipe 8 in the shoulder land portions 5c and 5c, and L1sb2 is the outside The total surface length of the first three-dimensional sipe 7 in the mediate land portion 5b2, and L2sb2 is the total surface length of the second three-dimensional sipe 8 in the outer mediate land portion 5b2.

  In the present embodiment, in the center region Rc and the shoulder region Rs, the sum of the surface lengths of the three-dimensional sipes 7 and 8 (L1c + L1s + L2c + L2s) is larger than the sum of the surface lengths of the plane sipe 9 (L3c + L3s). The total surface length of the three-dimensional sipes 7 and 8 is preferably 80% to 100% with respect to the sum of the total surface length of the three-dimensional sipes 7 and 8 and the total surface length of the planar sipes 9.

  In the tire 1 of the present embodiment described above, the land portion located in the center region Rc of the tread rubber 3 in addition to the rubber hardness of the tread rubber 3s in the shoulder region Rs being larger than the rubber hardness of the tread rubber 3c in the center region Rc. 5 a, 5 b 1, 5 b 1 are provided with more second solid sipes 8 than the first three-dimensional sipes 7 for reducing the land portion rigidity, and the land portions 5 b 2, 5 b 2, 5 c, 5 c located in the shoulder region Rs of the tread rubber 3. The first three-dimensional sipe 7 that increases the rigidity of the land portion is provided more than the second three-dimensional sipe 8. Therefore, as described below, the handling stability on the dry road surface and the braking performance on the ice road surface can be improved.

  That is, the wiping deformation in which the tread rubber 3 is deformed along the tire width direction when the tire 1 is brought into contact occurs more greatly in the shoulder region Rs than in the center region Rc. However, in the tire 1 of the present embodiment, as described above, Since the rigidity of the land portions 5b2, 5b2, 5c, 5c provided in the region Rs is enhanced, the land portion can be effectively prevented from falling due to wiping deformation. Therefore, in the tire 1 of this embodiment, road surface followability can be improved, and steering stability on a dry road surface can be improved.

  Moreover, the wiping deformation occurs more greatly in the land portion closer to the ground contact end CE, but in the tire 1 of the present embodiment, the land portion closer to the ground contact end CE occupies the three-dimensional sipes 7 and 8 provided in the land portion. Since the ratio of the second three-dimensional sipe 8 is set to be large and the rigidity of the land portion is increased, the steering stability on the dry road surface can be further improved.

  Further, even when the land portions 5b2, 5b2, 5c, 5c provided in the shoulder region Rs are formed of blocks divided in the tire circumferential direction A by the lateral grooves 4d as in the present embodiment, the book as described above. In the tire 1 of the embodiment, since the falling of the land portions 5b2, 5b2, 5c, and 5c is suppressed, uneven wear (heel and toe) in which a large difference in wear amount between the kicking side and the stepping side of the block occurs. Wear) can be suppressed.

  Further, in the tire 1 of the present embodiment, since the rigidity of the land portions 5a, 5b1, and 5b1 provided in the center region Rc is low, the ground contact area in the center region Rc can be increased. In addition, since the center region Rc is less susceptible to in-plane contraction force than the shoulder region Rs, even if the land portions 5a, 5b1, and 5b1 of the center region Rc are provided with many second three-dimensional sipes 8 to reduce the rigidity. Less susceptible to in-plane contraction force and less likely to cause wiping deformation.

  Further, the second three-dimensional sipe 8 absorbs the deformation of the land portion by the wide portions 8a to 8c, and the sipe width W21 on the surface of the tread rubber 3 is not easily reduced, so that the land portions 5a, 5b1, and 5b1 are bent. Edge effect and water removal effect can be ensured. That is, in the tire 1 of the present embodiment, the ground contact area in the center region Rc can be increased while leaving the edge effect and the water removal effect by the sipe 6 during braking, so that the braking performance on the ice road surface can be improved. .

  Moreover, in the tire 1 of the present embodiment, the land portion closer to the tire equatorial plane S1 and less susceptible to the in-plane contraction force has the second three-dimensional sipes 8 occupying the three-dimensional sipes 7 and 8 provided on the land portion. Since the ratio is increased to reduce the land portion rigidity, the contact area can be further increased and the braking performance on the ice road surface can be improved.

(Example of change)
In the above-described embodiment, as illustrated in FIGS. 3, 5, and 7, the case has been described in which a series of sipes 7, 8, and 9 are formed of the same type of sipes throughout the sipe length direction X. The present invention is not limited to this, and the type of sipe may change in the sipe length direction X as illustrated in FIG. That is, in the case of FIG. 8, the land portion 5 is provided with the plane sipes 9 connected to both ends in the sipe length direction X of the first three-dimensional sipe 7. Although not shown, a sipe that connects the first three-dimensional sipe 7 and the second three-dimensional sipe 8 is provided in the land portion 5, or a sipe that connects the second three-dimensional sipe 8 and the planar sipe 9 is provided in the land portion 5. You may connect and provide.

  Thus, when there are multiple types of sipes in one continuous sipe, the sum of the surface lengths of the sipe is divided into one sipe for each type, and the surface length of the divided sipe is set for each sipe. It can be obtained by adding each sipe.

  In the embodiment described above, the center land portion 5a and the pair of inner mediate land portions 5b1 are provided in the center region Rc, and the pair of outer mediate land portions 5b2 and the pair of shoulder land portions 5c are provided in the shoulder region Rs. However, the present invention is not limited to this, and the land portion 5 can be provided in the center region Rc and the shoulder region Rs as illustrated in FIGS.

  In addition, although it is suitable to apply the tire 1 of this embodiment to a studless tire (winter tire), it can also be applied to an all-season tire or a summer tire. The use of the tire is not limited to the tire for a passenger car as in the present embodiment, but may be a heavy load tire used for a truck or a bus.

  As mentioned above, although embodiment of this invention was described, this embodiment is shown as an example and is not intending limiting the range of invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention.

  In order to confirm the effect of the above embodiment, the ice braking performance, dry steering stability performance, and uneven wear resistance were evaluated for the tires of the examples and comparative examples (tire size: 195 / 65R15, air pressure: 220 KPa). .

  As shown in FIG. 10, the tires of Examples 1 to 4 and Comparative Examples 1 to 6 have a groove 40a provided on the tire equatorial plane S1 extending in the tire circumferential direction, and a tire having a groove 40a in the center region Rc. A pair of grooves 40b, 40b provided in the tire circumferential direction provided on the outer side in the width direction, and a tire circumference provided at the boundary between the center region Rc and the shoulder region Rs on the outer side in the tire width direction of the pair of grooves 40b, 40b. The tread rubber 3 is provided with a pair of grooves 40c, 40c extending in the direction.

  In the tires of Examples 1 to 4 and Comparative Examples 1 to 6, the pair of center land portions 50a and 50a partitioned between the groove 40a and the pair of grooves 40b and 40b, the pair of grooves 40b and 40b, and the pair of tires A pair of mediate land portions 50b, 50b defined between the grooves 40c, 40c are provided in the center region Rc, and a pair of shoulder land defined between the pair of grooves 40c, 40c and the ground contact CE. Portions 50c and 50c are provided in the shoulder region Rs.

  In the tires of Examples 1 to 4 and Comparative Examples 1 to 6, the first three-dimensional sipe 7 shown in FIG. 3, the second three-dimensional sipe 8 shown in FIG. 5, and the flat sipe 9 shown in FIG. The rubber hardness of the tread rubber 3c in the center region Rc and the tread rubber 3s in the shoulder region Rs set to the rubber hardness shown in Table 1 below is provided in each land portion 50a, 50a, 50b, 50b, 50c, 50c at the ratio shown. Has been.

  The tires of Examples 1 to 4 and Comparative Examples 1 to 6 have different ratios of the first three-dimensional sipe 7, the second three-dimensional sipe 8, and the planar sipe 9, and the rubber hardness constituting the tread rubber 3. However, all other configurations were the same. Further, the internal structures of the tires of Examples 1 to 4 and Comparative Examples 1 to 6 were the same as those of the tire 1 of the above embodiment shown in FIGS. 1 and 2.

  Each evaluation method is as follows.

<Ice braking performance>
The tires of Examples 1 to 4 and Comparative Examples 1 to 6 were mounted on a test vehicle (1500 cc, 4WD middle sedan vehicle) to run on the ice road surface, and the ABS was operated by applying a braking force at a speed of 40 km / h. The reciprocal of the braking distance was evaluated. The result of Comparative Example 1 is shown as an index with the value 100, and the larger the value, the better the braking performance on the ice road surface.

<Dry maneuvering stability>
A test vehicle (1500 cc, 4WD middle sedan vehicle) is mounted with the tires of Examples 1 to 4 and Comparative Examples 1 to 6 on a dry road surface, and the sensory evaluation points of acceleration, braking, turning, and lane change are compared. The result of Example 1 was expressed as an index, with the result being 100. The larger the value, the better the steering stability performance on the dry road surface.

<Uneven wear resistance>
After mounting the tires of Examples 1 to 4 and Comparative Examples 1 to 6 on a test vehicle (1500 cc, 4WD middle sedan vehicle) and running 12,000 km test, stepping on the kicking side of the blocks constituting the shoulder land portions 50c and 50c The difference in level was measured as the uneven wear amount (heel and toe wear amount), and the reciprocal of the uneven wear amount was displayed as an index with the conventional example being 100. The larger the index, the smaller the uneven wear amount and the better.

  In Table 1, the ratio of the plane sipe is the surface length of the plane sipe 9 with respect to the sum of the surface lengths of all the sipes 7, 8, 9 provided in the land portions 50a, 50a, 50b, 50b, 50c, 50c. It is the ratio of the total sum. The ratio of the three-dimensional sipes is the sum of the surface lengths of the three-dimensional sipes 7, 8 with respect to the sum of the surface lengths of all the sipes 7, 8, 9 provided in the land portions 50a, 50a, 50b, 50b, 50c, 50c. It is a ratio. The ratio of the first three-dimensional sipes 7 and the second three-dimensional sipes 8 in the center land portions 50a, 50a, the mediate land portions 50b, 50b and the shoulder land portions 50c, 50c is the first three-dimensional sipes provided in each land portion. 7 and the ratio of the surface length of the second solid sipe 8 to the total sum.

The results are as shown in Table 1. Comparative Example 1 in which only the plane sipe 9 is provided without providing the three-dimensional sipes 7 and 8, or the plane sipe 9 and the first three-dimensional sipe 7 without providing the second three-dimensional sipe 8. Comparative Examples 2 and 3 provided with the first three-dimensional sipe 7, Comparative Examples 4 and 5 provided with the flat sipe 9 and the second three-dimensional sipe 8, and the tread rubber 3c in the center region Rc as the shoulder region Rs. The rubber hardness of the tread rubber 3s in the shoulder region Rs is larger than the rubber hardness of the tread rubber 3c in the center region Rc in the first to fourth and sixth examples compared to the comparative example 6 in which the rubber hardness is the same as that of the tread rubber 3s. In addition, the center land portions 50a and 50a and the mediate land portions 50b and 50b located in the center region Rc are provided with more second solid sipes 8 than the first solid sipes 7, and the shoulder regions. Since there are more first three-dimensional sipes 7 than the second three-dimensional sipes 8 in the shoulder land portions 50c, 50c located at Rs, braking performance on ice road surfaces, steering stability on dry road surfaces, and uneven wear The performance could be improved.

  DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 2 ... Tread part, 3 ... Tread rubber, 3a ... Grounding surface, 4 ... Groove, 4a ... Center main groove, 4b ... Shoulder main groove, 4c ... Horizontal groove, 5 ... Land part, 5a ... Center land Part, 5b ... mediate land part, 5b1 ... inner mediate land part, 5b2 ... outer mediate land part, 5c ... shoulder land part, 6 ... sipe, 7 ... first solid sipe, 7a ... curved part, 8 ... second 3D sipe, 8a ... wide part, 8b ... wide part, 8c ... wide part, 9 ... plane sipe, 11 ... bead part, 11a ... bead, 12 ... side wall part, 13 ... carcass layer, 14 ... belt layer, 71 ... Sipe wall surface, 71a ... convex portion, 71b ... flat surface portion, 72 ... sipe wall surface, 72a ... concave portion, 72b ... flat surface portion, 73 ... sipe bottom surface, 81 ... sipe wall surface, 81a ... concave portion, 81b ... concave portion, 82 ... sipe wall surface, 82a Recess, 83 ... sipe bottom, 91 ... sipe wall surface, 92 ... sipe wall surface, 93 ... sipe bottom, 100 ... rim, S1 ... tire equatorial plane, Rc ... center region, Rs ... shoulder region,

Claims (6)

With tread rubber,
The tread rubber includes a plurality of first three-dimensional sipes and a plurality of second three-dimensional sipes,
The first three-dimensional sipe is provided with a sipe wall surface having a sipe width that is constant over the sipe depth direction and is bent in the sipe width direction in a cross-sectional view perpendicular to the sipe length direction.
The second three-dimensional sipe includes a wide portion having a sipe width wider than the surface of the tread rubber inside the tread rubber,
The tread rubber has a total surface length of the first three-dimensional sipe in a pair of shoulder regions located on the outer side in the tire width direction when the ground contact surface is divided into four equal parts in the tire width direction. The sum of the surface lengths of the second three-dimensional sipes is longer than the sum of the surface lengths of the first three-dimensional sipes in the center region located between the shoulder regions, and is longer than the sum of the lengths. A pneumatic tire having a rubber hardness of the tread rubber larger than that of the tread rubber in the center region ,
The tread rubber includes a plurality of main grooves extending in the tire circumferential direction, and a plurality of land portions defined by the main grooves and provided in the center region,
The land portion provided in the center region has a total surface length of the second solid sipe with respect to a sum of a total surface length of the first solid sipe and a total surface length of the second solid sipe. A pneumatic tire having a second ratio that is greater in the land portion closer to the center in the tire width direction. The tread rubber includes a plurality of main grooves extending in the tire circumferential direction, and a plurality of land portions defined by the main grooves and provided in the shoulder region,
The land portion provided in the shoulder region has a total surface length of the first three-dimensional sipe with respect to a sum of a total surface length of the first three-dimensional sipe and a total surface length of the second three-dimensional sipe. 2. The pneumatic tire according to claim 1 , wherein the first ratio including the ratio is larger toward the land portion closer to the ground contact end. 2. The pneumatic tire according to claim 1 , wherein the land portion provided in the center region has a difference in the second ratio between the land portions adjacent to each other in the tire width direction within a range of 5 to 15%. The pneumatic tire according to claim 2 , wherein the land portion provided in the shoulder region has a difference in the first ratio between the land portions adjacent to each other in the tire width direction within a range of 5 to 15%. The tread rubber includes a plurality of planar sipes,
The plane sipe comprises a straight sipe wall surface in a cross-sectional view perpendicular to the sipe length direction,
The sum of the surface length the sum of the said surface length sum of the first three-dimensional sipes second three-dimensional sipes, the longer claim 1 any one of 4 than the surface length sum of said planar sipe The described pneumatic tire. The tread rubber includes a plurality of main grooves extending in the tire circumferential direction, and a center land portion provided in the center region so as to straddle the center in the tire width direction, which is partitioned by the main grooves,
The pneumatic tire according to any one of claims 1 to 5 , wherein only the second three-dimensional sipe is provided in the center land portion among the first three-dimensional sipe and the second three-dimensional sipe.

Images