JP2017056767A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the brake performance and uneven wear resistance of a tire having a block pattern by restraining deterioration of block rigidity and collapsing of a block due to provided sipes, in the tire.SOLUTION: A pneumatic tire in this invention is equipped with plural blocks 24 partitioned by the lateral grooves 20B arranged at intervals in a tire circumferential direction CD. The sipes 28 are provided on the block 24 with a sipe density in a first area 32 of one side in a tire circumferential direction higher than that in a second area 34 of the other side by using a line 30 passing through a center in the tire circumferential direction of the block as a boundary. The protrusions 40 considerably protruding in the lateral grooves 20B compared to the sidewall 38 of the second area 34 side are provided on the sidewall 36 of the first area 32 side among the sidewalls 36, 38 of both sides of the block 24 in the tire circumferential direction CD.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a pneumatic tire.

  A block in which a plurality of main grooves extending in the tire circumferential direction are provided in a tread portion of the pneumatic tire, a horizontal groove is provided in a land portion defined by the main grooves, and a block row including a plurality of blocks is provided. Pattern tires are also known (see, for example, Patent Documents 1 and 2).

  In a tire having such a tread pattern, a sipe may be provided in the block in order to improve performance on snowy and snowy road surfaces (snow performance) and performance on wet road surfaces (wet performance). However, when the sipe density is increased, the block rigidity is lowered and the collapse of the block is increased, so that the braking performance is liable to be lowered and uneven wear is liable to occur.

JP 2004-058838 A JP 2011-240773 A

  In view of the above points, the present invention provides an air that can improve braking performance and uneven wear resistance in a tire having a block pattern by suppressing a decrease in block rigidity and a collapse of the block due to provision of sipes. An object is to provide a tire entering.

  The pneumatic tire according to the present embodiment is a pneumatic tire provided with a plurality of main grooves extending in the tire circumferential direction and a plurality of land portions partitioned by the main grooves in a tread portion. At least one of the land portions is provided. Is a block row in which a plurality of blocks partitioned by lateral grooves arranged at intervals in the tire circumferential direction are arranged in the tire circumferential direction, and at least one of the block rows is a block provided with sipes. The sipe density in the first region on one side in the tire circumferential direction is larger than the sipe density in the second region on the other side in the tire circumferential direction, with a line passing through the tire circumferential center of the block as a boundary. Among the side walls on both sides in the tire circumferential direction of the block, the side wall on the first region side protrudes greatly into the lateral groove compared to the side wall on the second region side. One in which out portion is provided.

  According to the present embodiment, it is possible to improve the braking performance and the uneven wear resistance by suppressing the decrease in block rigidity and the collapse of the block due to the provision of sipes.

The expanded view which shows the tread pattern of the pneumatic tire which concerns on one Embodiment. The width direction sectional view showing a part of the pneumatic tire. The top view of two blocks adjacent to the tire peripheral direction of the pneumatic tire. IV-IV sectional view taken on the line of FIG. VV sectional view taken on the line of FIG. Sectional drawing of the transverse groove which concerns on other embodiment. Sectional drawing of the horizontal groove | channel which concerns on other embodiment. Sectional drawing of the horizontal groove | channel which concerns on other embodiment.

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

  FIG. 1 is a plan view of a tread portion 10 of a pneumatic tire according to an embodiment, and FIG. 2 is a cross-sectional view along the tire width direction W (meridian direction) showing the periphery of the tread portion 10. The pneumatic tire includes a tread portion 10 and a pair of left and right bead portions (not shown) and sidewall portions 1, 1, and the tread portion 10 is an outer end in the tire radial direction K of the left and right sidewall portions 1, 1. It is provided so that parts may be connected. In the figure, CL indicates the tire equator plane and corresponds to the center in the width direction W of the tire.

  A carcass 2 composed of at least one carcass ply extending across a pair of bead portions is embedded in the pneumatic tire. On the outer peripheral side of the carcass 2 in the tread portion 10, a belt 3, a belt reinforcing layer 4, and a tread rubber 5 are laminated in this order, and the tread rubber 5 forms a surface of the tread portion 10 that constitutes a tire contact surface. ing.

  A plurality of (four in this example) straight main grooves 12 extending in the tire circumferential direction CD are provided on the surface of the tread portion 10. In this example, the main groove 12 is disposed on the outer side of the pair of center main grooves 12A and 12A on both sides of the tire equatorial plane CL and the pair of center main grooves 12A and 12A in the tire width direction W. And a pair of shoulder main grooves 12B, 12B.

  A plurality of land portions are defined in the tread portion 10 by the main grooves 12. Specifically, the tread portion 10 includes a central land portion 14 formed between the pair of left and right center main grooves 12A and 12A, and a pair of left and right intermediate portions formed between the center main groove 12A and the shoulder main groove 12B. Land portions 16, 16 and a pair of left and right shoulder land portions 18, 18 formed on the outer side in the tire width direction W of the pair of left and right shoulder main grooves 12B, 12B are provided.

  As shown in FIG. 1, each land portion 14, 16, 18 is provided with a plurality of lateral grooves 20 extending in a direction intersecting with the tire circumferential direction CD at intervals in the tire circumferential direction CD. A transverse groove 20A provided in the central land portion 14 and a transverse groove 20B provided in the intermediate land portion 16 are grooves that divide the land portions 14 and 16. Therefore, the central land portion 14 and the intermediate land portion 16 are each configured as a block row in which a plurality of blocks 22 and 24 partitioned by the lateral grooves 20A and 20B are arranged in the tire circumferential direction CD. As a result, the tire according to the present embodiment is a tire having a block-based tread pattern.

  The lateral grooves 20A and 20B are straight grooves inclined with respect to the tire width direction W. For this reason, in the blocks 22 and 24 constituting the block row of the central land portion 14 and the intermediate land portion 16, the ground contact surface 26 is formed in a parallelogram shape due to the inclination of the lateral grooves 20A and 20B. The lateral grooves 20A and 20B may be provided in parallel with the tire width direction W. In this case, the ground contact surface of the block has a rectangular shape. The shape of the block is not limited to a parallelogram shape or a rectangular shape, but can take various shapes such as a trapezoidal shape or a shape in which the block end is curved.

  Each land portion 14, 16, 18 is provided with a sipe 28 in order to improve snow performance and wet performance. Here, the sipe 28 refers to a cut formed in a land portion such as a block, and has a minute groove width. The groove width of the sipe 28 is not particularly limited, and may be, for example, 0.1 to 1.5 mm, 0.2 to 1.0 mm, or 0.3 to 0.8 mm.

  In the intermediate land portion 16 that is a block row, a plurality of sipes 28A, 28B, and 28C are provided in each block 24 constituting the block row. As shown in an enlarged view in FIG. 3, the block 24 has a sipe density in the first region 32 on one side in the tire circumferential direction CD with the line 30 passing through the tire circumferential center of the block 24 as a boundary. It is formed larger than the sipe density in the second region 34 on the other side of the CD. That is, the block 24 includes a first region 32 on one side in the tire circumferential direction and a second region 34 on the other side in the first region 32 when the block 24 is divided forward and backward with the line 30 as a boundary. The sipe density is larger than the sipe density in the second region 34. Therefore, the first area 32 is less rigid than the second area 34.

  In this example, two long sipes 28A and 28B are provided in the first region 32, and one short sipe 28C is provided in the second region 34. The sipes 28A and 28B in the first region 32 are unevenly distributed on one side of the block 24 in the tire width direction W. In this example, both the two sipes 28A and 28B are on the outer edge of the block 24 in the tire width direction. It opens, extends in the tire width direction W therefrom, and terminates in the block 24, thereby being unevenly distributed so that the sipe density on the outer side in the tire width direction is increased. The sipe 28C in the second region 34 is unevenly distributed on the other side in the tire width direction W of the block 24. In this example, the sipe 28C opens at the edge on the inner side (equator CL side) in the tire width direction of the block 24, and from there By extending in the width direction W and terminating in the block 24, the sipe density on the inner side in the tire width direction is unevenly distributed.

Here, the sipe density (mm / mm ² ) is the total length (mm) of the sipe 28 existing in the area per area (mm ² ) of each area 32, 34 on the block ground surface 26. The total length is the length of the sipe when there is one sipe in the area, and the total length of the sipe when there are a plurality of sipes.

  Further, the line 30 passing through the center in the tire circumferential direction is a line connecting the center positions in the tire circumferential direction CD of the block 24 in the respective width direction positions over the entire tire width direction W of the block 24. Therefore, when the block 24 is divided in the tire circumferential direction CD with the line 30 as a boundary, the area of the ground contact surface 26 of the block 24 is divided into two. In the example shown in FIG. 3, since the edge on both sides in the tire circumferential direction of the block 24 is inclined due to the inclination of the lateral groove 20B, the line 30 is also inclined with respect to the tire width direction W so as to be parallel to the edge. Straight line.

  In the block row of the intermediate land portion 16, between the blocks 24 and 24 adjacent in the tire circumferential direction CD, the first region 32 having a high sipe density and the second region 34 having a low sipe density are adjacent to each other across the lateral groove 20B. Is provided. In this example, as shown in FIGS. 1 and 3, the first region 32 and the second region 34 are formed by arranging the block 24 including the first region 32 and the second region 34 side by side in the tire circumferential direction CD. Are alternately provided in the tire circumferential direction CD.

  In the block 24 constituting the intermediate land portion 16, the lateral groove 20 </ b> B in the side wall 36 on the both sides in the tire circumferential direction CD is compared with the side wall 36 on the first region 32 side compared to the side wall 38 on the second region 34 side. A projecting portion 40 that projects greatly inside is provided. In this example, the side wall 38 on the second region 34 side is also provided with a protrusion 42 that protrudes into the lateral groove 20B, and the amount of protrusion of the protrusion 40 on the side wall 36 on the first region 32 side is the second region. It is set larger than the protruding amount of the protruding portion 42 of the side wall 38 on the 34 side.

  Specifically, the protruding portion 40 is formed by the side wall 36 facing the lateral groove 20B in the first region 32 protruding in the tire circumferential direction CD. 4, the protrusion 40 protrudes into the lateral groove 20B so as to reduce the cross-sectional area of the lateral groove 20B as shown in FIG. 5, and the upper end 36A ( It has a shape projecting into the lateral groove 20B with respect to a straight line La connecting the grounding end) and the lower end 36B (end on the groove bottom side). Therefore, the protrusion 40 does not extend the grounding surface 26 of the block 24. The protrusion 40 is formed over the entire height direction of the side wall 36, that is, a protrusion having a cross-sectional shape with the entire straight line La as a base. In this example, the cross-sectional shape of the protruding portion 40 is a trapezoidal shape with the straight line La as the base, as shown in FIG.

  The same applies to the protruding portion 42 of the side wall 38 on the second region 34 side, and the protruding portion 42 is formed by the side wall 38 facing the lateral groove 20B in the second region 34 protruding in the tire circumferential direction CD. The protrusion 42 protrudes into the lateral groove 20B so as to reduce the cross-sectional area of the lateral groove 20B with respect to the basic cross-sectional shape of the lateral groove 20B, and has an upper end 38A (grounding end) and a lower end 38B (on the groove bottom side) It has a shape projecting into the lateral groove 20B with respect to the straight line Lb connecting the end). Therefore, the protrusion 42 does not extend the grounding surface 26 of the block 24. The protrusion 42 is formed over the entire height of the side wall 38. In this example, the cross-sectional shape of the protrusion 42 is a trapezoid with the straight line La as the base.

  By forming the protrusions 40 and 44 in such a manner, as shown in FIG. 5, the cross-sectional shape of the lateral groove 20B is such that the groove width is narrowed by the protrusion 40 from the wide groove bottom, and the opening surface (grounding surface 26). Are formed in an undercut shape in which the groove width widens.

  These protrusions 40 and 42 may be provided on the entire length of the side walls 36 and 38 (the length of the lateral groove 20B) J, but in this example, the protrusions 40 are formed on a part of the length of the side walls 36 and 38. , 42 are provided. Specifically, in the first region 32 having low rigidity, the protrusions 40 and 42 are provided on one side in the tire width direction W where the sipes 28A and 28B are unevenly distributed, and the protrusions are provided on the other side in the tire width direction W. 40 and 42 are not provided.

  Further, in the side wall 36 on the first region 32 side and the side wall 38 on the second region 34 side facing each other across the lateral groove 20B, the protruding portions 40, 42 provided on both side walls 36, 38 face the tire circumferential direction CD. In position. That is, the protruding portions 40 and 42 extending in the tire width direction W are provided on the side walls 36 and 38 facing each other across the lateral groove 20B so as to overlap each other when viewed from the tire circumferential direction CD. Therefore, at the position where the protrusions 40 and 42 are provided, the gap between the protrusions 40 and 42 becomes the width of the horizontal groove 20B (remaining groove width).

  According to the present embodiment, among the side walls 36, 38 on both sides in the tire circumferential direction CD of the block 24, the side wall 36 on the first region 32 side where the sipe density is large is compared with the side wall 38 on the second region 34 side. Since the protrusion 40 having a large protrusion amount is provided, the block rigidity can be effectively increased in the first region 32 having a low rigidity. More specifically, a protruding portion 40 having a large protruding amount is provided on the side wall 36 on the first region 32 side having a high sipe density and low rigidity, and protruding on the side wall 38 on the second region 34 side having a low sipe density and high rigidity. By providing the protrusion 42 with a small amount, it is possible to improve the effective block rigidity according to the sipe density. That is, as compared with the case where the protruding portions are evenly provided on both side walls 36, 38 of the block 24, the effect of improving the block rigidity can be further enhanced even if the protruding portions have the same volume. Therefore, while maintaining the wet performance and the snow performance, the block rigidity can be improved to suppress the collapse of the block, and the braking performance and the uneven wear resistance can be improved.

  Between the blocks 24, 24 adjacent to the tire circumferential direction CD, the first region 32 having a high sipe density and the second region 34 having a low sipe density are adjacent to each other with the lateral groove 20B interposed therebetween, and are opposed to each other with the lateral groove 20B interposed therebetween. In the side wall 36 on the first region 32 side and the side wall 38 on the second region 34 side, the protrusions 40 and 42 provided on the both side walls 36 and 38 are provided at positions facing the tire circumferential direction CD. The effect of is produced. That is, the protrusions 40 and 42 of the side walls 36 and 38 that face each other across the lateral groove 20B come into contact with each other and support each other due to a heavy load load during tire braking, so that the collapse of the block 24 can be suppressed. From this point as well, the effect of improving braking performance and uneven wear resistance can be enhanced.

  Here, the amount of protrusion of the protrusions 40 and 42 provided on the side walls 36 and 38 is not particularly limited, but the amount of protrusion Ta of the protrusion 40 provided on the side wall 36 on the first region 32 side is the groove width G of the lateral groove 20B. It is preferable that it is 30 to 40%. In addition, the protrusion amount Tb of the protrusion 42 provided on the side wall 38 on the second region 34 side is preferably 10 to 20% of the groove width G of the lateral groove 20B. Thereby, the remaining groove width (that is, the gap between the protrusions 40 and 42) Gr of the lateral groove 20B can be set to 40 to 60% of the groove width G of the lateral groove 20B. The protrusion amount Ta is 30% or more and the protrusion amount Tb is 10% or more, so that the effect of reinforcing the block rigidity can be enhanced and the protrusions 40 and 42 can be contacted under heavy load. Thus, the fall-in suppressing effect can be enhanced. When the protrusion amount Ta is 40% or less and the protrusion amount Tb is 20% or less, adverse effects on wet performance and snow performance due to excessively small voids in the lateral grooves 20B can be suppressed.

  The groove width G of the lateral groove 20B is not particularly limited, but is preferably 6 mm or less, and more preferably 5 mm or less from the viewpoint of making the protrusions 40 and 42 easy to contact when a heavy load is applied. The lateral groove 20B is a thicker groove than the sipe, and the groove width G is preferably 2 mm or more, more preferably 3 mm or more. More specifically, the lateral groove 20B is preferably a narrow groove having such a groove width that the protruding portions 40 and 42 provided on the side walls 36 and 38 on both sides can come into contact with each other when a heavy load such as braking is applied.

  Further, since the protruding portions 40 and 42 are provided not on the entire length J of the side walls 36 and 38 but on a part thereof, the reinforcing effect of the block is enhanced while the braking performance is improved while ensuring the wet performance and the snow performance. Can be improved. Here, the range Jt in which the protrusions 40 and 42 are provided is preferably 30 to 50% with respect to the entire length J of the side walls 36 and 38. By being 30% or more, the improvement effect of the braking performance by the improvement of block rigidity can be heightened. Moreover, when it is 50% or less, it is possible to suppress adverse effects on wet performance and snow performance due to voids in the lateral grooves 20B becoming too small.

  Further, by providing the protrusions 40 and 42 on one side in the tire width direction where the sipes 28B and 28C are unevenly distributed as described above, the block rigidity can be more efficiently increased.

  The cross-sectional shape of the protrusions 40 and 42 is not limited to the trapezoidal shape as shown in FIG. For example, as shown in FIG. 6, it is good also as a shape protruded in circular arc shape in cross section. Moreover, as shown in FIG. 7, it is good also as a cross-sectional shape which combined the straight line and the curve. Further, as shown in FIG. 8, the projecting vertices 40A, 42A of the projecting portions 40, 42 are shaped so as to be biased toward the grounding surface 26 side from the depth center of the lateral groove 20B, and then the lower ends 36B of the side walls 36, 38 , 38B may be provided with inclined surface portions 40B, 42B in which the amount of protrusion gradually increases toward the protruding vertices 40A, 42A, thereby improving the mold release from the mold during tire vulcanization molding. .

  In the above embodiment, the protruding configuration of the side walls 36 and 38 is adopted in all the blocks 24 constituting the block row of the intermediate land portion 16, but it is not necessary to be all the blocks 24, and is adopted in some blocks. May be. In addition, instead of adopting the projecting configuration in the intermediate land portion 16, or in addition to the intermediate land portion 16, a similar projecting configuration may be employed in other land portions such as the central land portion 14. Moreover, although the case where the four main grooves 12 were provided was demonstrated, the number of main grooves is not limited to four, For example, three or five may be sufficient.

  Examples of the pneumatic tire according to the present embodiment include tires for various vehicles such as tires for passenger cars, tires for heavy loads such as trucks and buses, and particularly, applications such as summer tires, winter tires, and all-season tires. It is not limited. As a preferred embodiment, it is used for all-season tires because it has a block-based pattern and is excellent in braking performance on a dry road surface while ensuring snow performance and wet performance.

  In the present specification, the width of the sipe and the lateral groove, the protruding amount of the protruding portion, and the like are those in a normal state with no load in which a pneumatic tire is mounted on a normal rim and filled with a normal internal pressure. The regular rim is “standard rim” in JATMA standard, “Design Rim” in TRA standard, or “Measuring Rim” in ETRTO standard. The normal internal pressure is “maximum air pressure” in the JATMA standard, “maximum value” described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, or “INFLATION PRESSURE” in the ETRTO standard.

  Although some embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

  In order to show the effect of the above embodiment, pneumatic radial tires for passenger cars of Example 1 and Comparative Examples 1 and 2 (size: 215 / 55R17) were prototyped. The tire of Example 1 is the tire of the above-described embodiment shown in FIGS. 1 to 5, and in the block 24 of the intermediate land portion 16, the side wall 36 on the side of the first region 32 having a high sipe density is replaced with the second sipe density having a low sipe density. It protrudes larger than the side wall 38 on the region 34 side. Protrusion amount Ta of the projection 40 on the side wall 36 on the first region side is 1.6 mm, and the projection amount Tb of the projection 42 on the side wall 38 on the second region side is 0.8 mm. Is 50% of the overall length J of the side walls 36,38. The groove width G of the lateral groove was 4 mm.

  The comparative example 1 is an example in which the protruding portions 40 and 42 are not provided with respect to the first embodiment. Comparative Example 2 is an example in which the protruding amounts of the protruding portion 40 of the side wall 36 on the first region side and the protruding portion 42 of the side wall 38 on the second region side are set to the same value as in Example 1 (Ta = Tb = 1.2 mm). In Comparative Examples 1 and 2, other configurations are the same as those in the first embodiment.

  These tires were attached to regular rims and assembled to the vehicle as regular internal pressure, and uneven wear resistance, wet performance, and dry braking performance were evaluated. Each evaluation method is as follows.

  Uneven wear resistance: The amount of tire wear after traveling 15000 km on the dry road was measured, and the uneven wear ratio in the block = (minimum wear amount / maximum wear amount) was calculated. It means that it is excellent in uneven wear resistance, so that a partial wear ratio is large.

  -Wet performance: By running (starting, accelerating, turning) on a 1 mm water film road surface as a wet road surface, sensory evaluation of steering stability by a paneler was performed. The evaluation result of Comparative Example 1 is displayed as an index, and the larger the index, the better the wet performance.

  Dry braking performance: Entering a dry asphalt road surface at a speed of 100 km / h, measuring the stopping distance when full braking is performed from the braking start position, and using the value of Comparative Example 1 as the reciprocal of the stopping distance. The index was evaluated. The larger the index, the better the dry braking performance.

  The results are as shown in Table 1. As compared with Comparative Example 1 as a control, Example 1 was able to improve uneven wear resistance and braking performance while suppressing a decrease in wet performance. On the other hand, in Comparative Example 2, it is considered that the block rigidity was improved by providing the protruding portion on the side wall of the block. However, since the protruding amount of the side wall on both sides in the tire circumferential direction was the same, the effect of the block rigidity was Therefore, compared with Example 1, the improvement effect of uneven wear resistance and braking performance was slight.

DESCRIPTION OF SYMBOLS 10 ... Tread part, 16 ... Middle land part, 20B ... Cross groove, 24 ... Block, 28, 24A-C ... Sipe, 30 ... Line passing through the tire circumferential center of a block, 32 ... 1st area | region, 34 ... 2nd area | region , 36 ... side wall on the first area side, 38 ... side wall on the second area side, 40, 42 ... projection, CD ... tire circumferential direction

Claims (4)

In a pneumatic tire provided with a plurality of main grooves extending in the tire circumferential direction and a plurality of land portions partitioned by the main grooves in a tread portion,
At least one of the land portions is a block row in which a plurality of blocks partitioned by lateral grooves arranged at intervals in the tire circumferential direction are arranged in the tire circumferential direction,
At least one of the block rows is a block provided with sipes, and a sipe density in the first region on one side of the tire circumferential direction is defined by the other side in the tire circumferential direction with a line passing through the tire circumferential center of the block as a boundary. A block formed larger than the sipe density in the second region on the side,
Of the side walls on both sides in the tire circumferential direction of the block, the side wall on the first region side is provided with a protruding portion that protrudes greatly in the lateral groove compared to the side wall on the second region side,
Pneumatic tire.   The side wall on the second region side is also provided with a protrusion that protrudes into a lateral groove, and the amount of protrusion of the protrusion on the side wall on the first region side is larger than the amount of protrusion on the side wall on the second region side. The pneumatic tire according to claim 1, which is large.   In the at least one block row, between the blocks adjacent to each other in the tire circumferential direction, the first region having a high sipe density and the second region having a low sipe density are adjacent to each other with a horizontal groove interposed therebetween. 3. The pneumatic tire according to claim 2, wherein the protruding portions provided on both side walls are in positions facing each other in the tire circumferential direction on the side wall on the first region side and the side wall on the second region side facing each other.   The protruding amount of the protruding portion provided on the side wall on the first region side is 30 to 40% of the groove width of the lateral groove, and the protruding amount of the protruding portion provided on the side wall on the second region side is the groove width of the horizontal groove. The pneumatic tire according to claim 2 or 3, which is 10 to 20% of the tire.

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