JP6530683B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  The tread portion of the pneumatic tire is provided with a plurality of main grooves extending in the tire circumferential direction, and a land groove sectioned by the main grooves is provided with a lateral groove, 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, blocks may be provided with sipes 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 reduced, and the falling of the block is increased, so that the braking performance is likely to be reduced and uneven wear is easily generated.

JP, 2004-058838, A JP, 2011-240773, A

  The present invention, in view of the above points, in a tire having a block pattern, it is possible to improve braking performance and uneven wear resistance by suppressing decrease in block rigidity and block collapse due to the provision of sipes. The purpose is to provide a tire.

  The pneumatic tire according to the present embodiment is a pneumatic tire including a plurality of main grooves extending in the circumferential direction of the tire and a plurality of land portions divided 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 spaced in the tire circumferential direction are disposed in the tire circumferential direction, and at least one of the block rows is a block provided with sipes Block, wherein the sipe density in the first region on one side in the tire circumferential direction is formed larger than the sipe density in the second region on the other side in the tire circumferential direction with the line passing through the tire circumferential direction center of the block as a boundary Of the side walls of the block in the tire circumferential direction, the side walls on the side of the first region, and the side walls on the side of the second region, which largely project into the lateral groove 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 falling of the block due to the provision of the sipes.

BRIEF DESCRIPTION OF THE DRAWINGS The developed view which shows the tread pattern of the pneumatic tire concerning one Embodiment. Width direction sectional drawing which shows a part of same 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. FIG. 5 is a cross-sectional view taken along the line V-V of FIG. 3; Sectional drawing of the horizontal groove which concerns on other embodiment. Sectional drawing of the horizontal groove which concerns on other embodiment. Sectional drawing of the horizontal groove 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 taken along the tire width direction W (meridial 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 and 1. The tread portion 10 is an outer end in the tire radial direction K of the left and right sidewall portions 1 and 1 It is provided to connect the parts. In the figure, CL indicates the tire equatorial plane, which corresponds to the center of the width direction W of the tire.

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

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

  A plurality of land portions are defined in the tread portion 10 by the main groove 12. In detail, in the tread portion 10, a central land portion 14 formed between a pair of left and right center main grooves 12A, 12A, and a pair of left and right intermediate 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, in each land portion 14, 16, 18, a plurality of lateral grooves 20 extending in a direction intersecting with the tire circumferential direction CD are provided at intervals in the tire circumferential direction CD. The lateral groove 20A provided in the central land portion 14 and the lateral groove 20B provided in the intermediate land portion 16 are grooves for dividing the land portions 14 and 16 from each other. Therefore, the central land portion 14 and the intermediate land portion 16 are configured as a block row in which a plurality of blocks 22 and 24 partitioned by the lateral grooves 20A and 20B are disposed in the tire circumferential direction CD. Thus, 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. Therefore, in the blocks 22 and 24 constituting the block row of the central land portion 14 and the intermediate land portion 16, the ground plane 26 is formed in a parallelogram by the inclination of the lateral grooves 20A and 20B. The lateral grooves 20A and 20B may be provided in parallel to the tire width direction W, in which 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, and can take various shapes such as a trapezoidal shape or a shape in which a block end is curved.

  Each land portion 14, 16, 18 is provided with a sipe 28 in order to improve the snow performance and the wet performance. Here, the sipe 28 refers to a cut formed on 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 which 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 manner in FIG. 3, the block 24 has a sipe density in the first region 32 on one side of the tire circumferential direction CD with the line 30 passing through the tire circumferential direction center of the block 24 as the boundary. It is formed larger than the sipe density in the second region 34 on the other side of the CD. That is, when the block 24 is divided forward and backward with the line 30 as a boundary, the block 24 is composed of the first region 32 on one side in the tire circumferential direction and the second region 34 on the other side, and in the first region 32 The sipe density is greater 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 sipes 28C are provided in the second region 34. The sipes 28A and 28B of the first region 32 are unevenly distributed on one side in the tire width direction W of the block 24. In this example, both of the two sipes 28A and 28B are at the outer edge of the block 24 in the tire width direction. It is opened, extends in the tire width direction W, and terminates in the block 24. As a result, it is unevenly distributed so that the sipe density on the tire width direction outer side becomes high. The sipe 28C of the second region 34 is unevenly distributed on the other side of the block 24 in the tire width direction W. In this example, the sipe 28C is opened at the edge of the block 24 in the tire width direction (equator CL side). 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 so as to be high.

Here, the sipe density (mm / mm ² ) is the total length (mm) of the sipe 28 present in the area per square of the area 32, 34 in the block ground plane 26 (mm ² ). The total length is the length of the sipe when there is one sipe in that region, and the total length of the plurality of sipe when there are a plurality of sipe.

  Further, the line 30 passing through the center in the tire circumferential direction is a line connecting the center positions of the blocks 24 in the tire circumferential direction CD at the respective positions in the width direction throughout the 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 contact surface 26 of the block 24 is bisected in area. In the example shown in FIG. 3, since the edges on both sides in the tire circumferential direction of the block 24 are inclined in a straight line due to the inclination of the lateral grooves 20B, the line 30 is also inclined with respect to the tire width direction W so as to be parallel to the edges. It is a straight line.

  In the block row of the intermediate land portion 16, between the blocks 24, 24 adjacent in the tire circumferential direction CD, the first region 32 with high sipe density and the second region 34 with low sipe density are adjacent via the lateral groove 20B. Provided in In this example, as shown in FIG. 1 and FIG. 3, the first area 32 and the second area 34 are formed by arranging the blocks 24 consisting of the first area 32 and the second area 34 in parallel in the tire circumferential direction CD. Are alternately provided in the tire circumferential direction CD.

  Of the side walls 36 and 38 on both sides in the tire circumferential direction CD of the block 24 constituting the intermediate land portion 16, the side groove 36 on the side of the first region 32 has a lateral groove 20B compared to the side wall 38 on the side of the second region 34. A projecting portion 40 that protrudes largely inward is provided. In this example, the side wall 38 on the side of the second region 34 is also provided with the protrusion 42 protruding into the lateral groove 20B, and the amount of protrusion of the protrusion 40 of the side wall 36 on the side of the first region 32 is the second region The protrusion amount of the protrusion 42 of the side wall 38 on the side 34 is set to be larger.

  In detail, the protrusion 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. The protrusion 40 projects into the lateral groove 20B so as to reduce the cross-sectional area of the lateral groove 20B as shown in FIG. 5 with respect to the basic cross-sectional shape of the lateral groove 20B shown in FIG. With respect to a straight line La connecting the ground end) and the lower end 36B (end on the groove bottom side), it has a shape projecting in the lateral groove 20B. Thus, the protrusions 40 do not extend the ground plane 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, as shown in FIG. 5, the cross-sectional shape of the protrusion 40 is trapezoidal with the straight line La as a base.

  The same applies to the protrusion 42 of the side wall 38 on the second region 34 side, and the protrusion 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 projects 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 the upper end 38A (grounding end) of the side wall 38 and the lower end 38B (groove bottom side) With respect to a straight line Lb connecting with the end), it has a shape projecting in the lateral groove 20B. Thus, the protrusions 42 do not extend the ground plane 26 of the block 24. The protrusion 42 is formed over the entire height direction of the side wall 38. In this example, the cross-sectional shape of the protrusion 42 is a trapezoidal shape whose base is the straight line La.

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

  These protrusions 40 and 42 may be provided on the entire length of the side walls 36 and 38 (length of the lateral groove 20B) J, but in this example, the protrusions 40 on part of the length of the side walls 36 and 38 , 42 are provided. Specifically, in the first region 32 with 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 on the other side in the tire width direction W 40 and 42 are not provided.

  Further, in the side wall 36 on the side of the first region 32 and the side wall 38 on the side of the second region 34 facing each other across the lateral groove 20B, the projecting portions 40 and 42 provided on both side walls 36 and 38 face in the tire circumferential direction CD. In position. That is, in the side walls 36 and 38 facing each other across the lateral groove 20B, the projecting portions 40 and 42 extending in the tire width direction W are provided so as to overlap with each other as 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 (remaining groove width) of the lateral groove 20B.

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

  Between the blocks 24 adjacent to each other in the tire circumferential direction CD, the first region 32 having a large sipe density and the second region 34 having a small 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 side of the first region 32 and the side wall 38 on the side of the second region 34, the protruding portions 40 and 42 provided on both side walls 36 and 38 are provided at positions facing the tire circumferential direction CD. The effects and effects of That is, the projecting portions 40 and 42 of the side walls 36 and 38 opposed to each other across the lateral groove 20B contact and support each other by heavy load load at the time of tire braking, thereby suppressing falling of the block 24. From this point as well, the improvement effect of the braking performance and the uneven wear resistance can be enhanced.

  Although the amount of protrusion of the protrusions 40 and 42 provided on the side walls 36 and 38 is not particularly limited, the amount Ta of protrusion 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% of. Further, the amount Tb of protrusion 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. When the protrusion amount Ta is 30% or more and the protrusion amount Tb is 10% or more, the reinforcing effect of the block rigidity can be enhanced, and the protrusions 40 and 42 can be in contact under heavy load. Can improve the fall control effect. When the protrusion amount Ta is 40% or less and the protrusion amount Tb is 20% or less, an adverse effect on the wet performance and the snow performance due to the void of the lateral groove 20B becoming too small can be suppressed.

  Although the groove width G of the lateral groove 20B is not particularly limited, it is preferably 6 mm or less, more preferably 5 mm or less, from the viewpoint of facilitating the contact of the protrusions 40 and 42 under heavy load. The lateral groove 20B is a groove that is thicker than the sipe, and the groove width G is preferably 2 mm or more, and more preferably 3 mm or more. More specifically, the lateral groove 20B is preferably a narrow groove having a groove width such that the protrusions 40 and 42 provided on the side walls 36 and 38 on both sides can be in contact under heavy load such as braking.

  Moreover, since the protrusions 40 and 42 are provided not on the entire length J of the side walls 36 and 38 but on a part of them, the reinforcement effect of the block is enhanced while securing the wet performance and the snow performance, and the braking performance is improved. It 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 damping | braking performance by the improvement of block rigidity can be heightened. Further, by setting the content to 50% or less, an adverse effect of the wet performance and the snow performance due to the void of the lateral groove 20B becoming too small can be suppressed.

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

  In addition, as a cross-sectional shape of the protrusion parts 40 and 42, it is not limited to a trapezoidal shape as was shown by FIG. For example, as shown in FIG. 6, it may be shaped to project in an arc shape in cross section. Further, as shown in FIG. 7, a cross-sectional shape in which a straight line and a curve are combined may be used. Furthermore, as shown in FIG. 8, the projecting apexes 40A and 42A of the projecting portions 40 and 42 are shaped to be biased from the depth center of the lateral groove 20B toward the ground contact surface 26, and the lower end 36B of the side walls 36 and 38 is obtained. , 38B may be provided with inclined surface portions 40B and 42B in which the amount of protrusion gradually increases toward the protruding apexes 40A and 42A, whereby the releasability from the mold at the time of tire vulcanization molding can also be improved. .

  In the above embodiment, the projecting 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 not all the blocks 24 need to be adopted. May be Also, the projecting configuration may adopt the same projecting configuration in other land parts such as the central land part 14 instead of or in addition to the middle land part 16. Although the case where four main grooves 12 are provided has been described, the number of main grooves is not limited to four, and may be three or five, for example.

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

  In the present specification, the width of the sipe or the lateral groove, the protrusion amount of the protrusion, and the like are those in a non-loaded normal state in which a pneumatic tire is mounted on a normal rim and filled with normal internal pressure. The normal rim is the "standard rim" in the JATMA standard, the "Design Rim" in the TRA standard, or the "Measuring Rim" in the ETRTO standard. The normal internal pressure is the "maximum air pressure" in the JATMA standard, the "maximum value" described in the "TIRE LOAD LIMITS AT VARIOUS COLD INFlation PRESSURES" in the TRA standard, or the "INFLATION PRESSURE" in the ETRTO standard.

  While certain embodiments have been described above, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention.

  In order to demonstrate the effect of the said embodiment, the pneumatic radial tire (size: 215/55 R17) for passenger cars of Example 1 and Comparative Examples 1 and 2 was produced as an experiment. The tire of Example 1 is a tire of the above-mentioned embodiment shown in Drawings 1-5, in block 24 of middle land part 16, the side wall 36 by the side of the 1st field 32 with large sipe density is the 2nd with small sipe density It projects more than the side wall 38 on the region 34 side. The amount of protrusion Ta of the protrusion 40 of the side wall 36 on the first region side is 1.6 mm, and the amount of protrusion Tb of the protrusion 42 of the side wall 38 on the second region side is 0.8 mm. Is 50% of the entire length J of the side walls 36, 38. The groove width G of the lateral grooves was 4 mm.

  The comparative example 1 is an example in which the protrusions 40 and 42 are not provided in the first embodiment. Comparative Example 2 is an example in which the amount of protrusion of the protrusion 40 of the side wall 36 on the side of the first region and the protrusion 42 of the side wall 38 on the side of the second region are the same value with respect to Example 1 (Ta = Tb = 1.2 mm). The other configurations of the comparative examples 1 and 2 are the same as those of the first embodiment.

  These tires were mounted on regular rims, and were fitted to vehicles as regular internal pressure, and the partial abrasion 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 15,000 km on a dry road was measured, and the uneven wear ratio in the block = (minimum wear / maximum wear) was calculated. The larger the uneven wear ratio, the better the uneven wear resistance.

  -Wet performance: A sensory evaluation of the steering stability by the panelists was carried out by running (starting, accelerating, turning) on a road surface of a 1 mm water film as a wet road surface. The evaluation result of Comparative Example 1 is represented by an index of 100, 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, measure the stopping distance when performing full braking from the braking start position, and for the reciprocal of stopping distance, set the value of Comparative Example 1 to 100 And was evaluated by the index. The larger the index, the better the dry braking performance.

  The results are as shown in Table 1. With respect to Comparative Example 1 which is the control, Example 1 was able to improve the partial abrasion resistance and the braking performance while suppressing the decrease in the wet performance. On the other hand, in Comparative Example 2, the block rigidity is considered to be improved by providing the protruding portion on the side wall of the block, but the protrusion amount of the side wall on both sides in the tire circumferential direction is the same. As compared with Example 1, the effect of improving the uneven wear resistance and the braking performance was small.

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

Claims (4)

In a pneumatic tire including a plurality of main grooves extending in the tire circumferential direction and a plurality of land portions divided by the main grooves in a tread portion,
The at least one land portion is a block row in which a plurality of blocks partitioned by lateral grooves spaced in the tire circumferential direction are disposed in the tire circumferential direction,
At least one of the block rows is a block provided with sipes, and the sipe density in the first region on one side in the tire circumferential direction is the other in the tire circumferential direction with the line passing through the tire circumferential direction center of the block as the boundary. Containing blocks formed larger than the sipe density in the second region of the side,
Out of the side walls on both sides in the tire circumferential direction of the block, the side wall on the first area side is provided with a projecting portion that largely protrudes into the lateral groove compared to the side wall on the second area side.
Pneumatic tire.   The side wall on the second region side is also provided with a protrusion projecting into the lateral groove, and the protrusion amount of the protrusion on the side wall on the first region side is more than the protrusion amount of the 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 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 lateral groove interposed therebetween, and the lateral groove interposed therebetween The pneumatic tire according to claim 2, wherein the protruding portions provided on both side walls of the side wall on the side of the first region facing each other and the side wall on the side of the second region are at positions facing each other in the tire circumferential direction.   The protrusion amount of the protrusion provided on the side wall of the first region is 30 to 40% of the groove width of the lateral groove, and the protrusion amount of the protrusion provided on the side wall of the second region is the groove width of the lateral groove The pneumatic tire according to claim 2 or 3, which is 10 to 20% of.

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