JP2014097697A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve compatibility between running performance on ice road surfaces and stability on dry road surfaces.SOLUTION: In a pneumatic tire having rib-shaped land parts divided by a plurality of main grooves extending in the tire circumferential direction and/or block-shaped land parts 31 divided by a plurality of lug grooves intersecting the main grooves and the main grooves on the tread surface 11, there are provided sipings 5 which are opened to the tread surface 11 in the land parts 31, extend in a direction intersecting the tire circumferential direction and having diameter expanded parts 6 whose diameter is expanded wider than the siping width W2 in the inner end 5a in the tire radial direction. The diameter expanded parts 6 are opened at least in a side wall outside the land parts 31 in the tire width direction and formed at positions shifted gradually, outward in the tire radial direction, from the inner end in the tire width direction to the outer end in the tire width direction.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that achieves both running performance on an icy road surface and steering stability performance on a dry road surface.

  In pneumatic tires, it is common to improve the water removal effect of receiving water between the tread surface and the road surface by placing the sipe on the land to improve the running performance on the road surface on ice. . On the other hand, if a large number of sipes are arranged, the rigidity of the land portion decreases and the handling stability on the dry road surface decreases. For this reason, there exists a subject which makes compatible the running performance on the road surface on ice, and the steering stability performance on the dry road surface.

  For example, Patent Document 1 discloses a pneumatic tire in which a sipe has an enlarged portion in the depth direction. This pneumatic tire has an enlarged portion, thereby increasing the amount of water stored in the sipe and increasing the water absorption performance and drainage performance.

  For example, Patent Document 2 discloses a pneumatic tire in which a sipe has an enlarged diameter portion, and the diameter of the enlarged diameter portion increases as the side wall of the land portion is approached. In this pneumatic tire, the enlarged diameter portion is formed at the inner end in the tire radial direction, so that crack generation is suppressed when a load is input to the sipe during rolling of the tire, and when traveling on an icy road surface Get the drainage effect. Further, in this pneumatic tire, since the diameter-expanded portion becomes larger toward the side wall of the land portion, absorbed water flows toward the both end sides and is discharged.

  Further, for example, Patent Document 3 is provided with an enlarged diameter portion formed by increasing the sipe width at the tire radial direction inner end of the sipe, and the bottom of the sipe has the largest sipe at the center in the longitudinal direction of the sipe. A pneumatic tire is shown in which a shallow bottom portion having a shallow depth is provided, and the diameter-expanded portion extends from the shallow bottom portion toward the side wall of the land portion and increases in diameter from the shallow bottom portion toward the side wall of the land portion. This pneumatic tire improves the absorption function of absorbing water between the ice road surface and the tread surface within the enlarged diameter portion. Further, in this pneumatic tire, the water accumulated in the center part in the longitudinal direction of the sipe is likely to flow from the shallow bottom part toward the side wall of the land part. Further, in this pneumatic tire, since the enlarged diameter portion becomes larger from the shallow bottom portion toward the side wall of the land portion, the diameter of the central portion in the longitudinal direction of the enlarged diameter portion becomes narrower than both ends, so that sipes are reduced. When absorbing water, the water pressure at the center is higher than at both ends, and the absorbed water flows toward both ends and is discharged.

  Further, for example, in Patent Document 4, an enlarged sub-portion is provided in a region of 20 [%] or more and 90 [%] or less of the maximum depth of the siping-shaped narrow groove from the ground contact surface. A pneumatic tire whose length in the direction expands from the center side in the width direction of the land portion toward the side edge side is shown. This pneumatic tire effectively absorbs water from the road surface and improves running performance on icy and snowy roads.

JP-A-1-101205 JP 2011-88468 A JP 2011-105180 A Japanese Patent No. 4299804

  As in the pneumatic tires described in Patent Document 1 to Patent Document 4 described above, the water absorption amount of water is improved by partially widening the groove width of the sipe. However, if the width of the sipe groove is widened, the rigidity of the land portion decreases, and the steering stability particularly on the dry road surface decreases.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can make compatible the driving performance on an ice surface, and the steering stability performance on a dry road surface.

  In order to solve the above-described problems and achieve the object, the pneumatic tire according to the first aspect of the present invention is a rib-like land portion defined by a plurality of main grooves extending in the tire circumferential direction on the tread surface, And / or a pneumatic tire having a block-shaped land portion defined by a plurality of lug grooves intersecting the main groove and the main groove, wherein the land portion opens in the tread surface and extends in the tire circumferential direction. The sipe extends in the intersecting direction and has a sipe having an enlarged diameter portion that is larger than the sipe width at an inner end in the tire radial direction, and the enlarged diameter portion includes at least a sidewall on the outer side in the tire width direction of the land portion. And the position is gradually changed from the inner end in the tire width direction toward the outer end in the tire width direction toward the outer end in the tire radial direction.

  According to this pneumatic tire, the water removal effect and edge effect of receiving water between the tread surface and the tread surface into the groove by sipe are obtained, and the water removal performance is improved by storing water in the enlarged diameter portion. Can do. Moreover, according to this pneumatic tire, the diameter-enlarged portion opens at least on the side wall on the outer side in the tire width direction of the land portion, so that the water received in the groove of the sipe is drained to the outer side in the tire width direction on the land portion. Can do. In particular, according to this pneumatic tire, the enlarged diameter portion is formed by gradually changing the position from the inner end in the tire width direction toward the outer end in the tire width direction toward the outer end in the tire radial direction. Since drainage is received under the action of the accompanying centrifugal force, drainage can be improved. For this reason, the running performance on an ice surface can be maintained. On the other hand, the rigidity of the land portion tends to decrease due to the arrangement of the sipe, but according to this pneumatic tire, the enlarged diameter portion is located on the outer side in the tire radial direction from the inner end in the tire width direction toward the outer end in the tire width direction. Is formed so that the groove depth of the sipe is shallower on the outer side in the tire width direction on the land portion than on the outer side in the tire width direction, and the rigidity on the outer side in the tire width direction on the land portion is greater than that on the inner side in the tire width direction. Also gets higher. For this reason, the steering stability on the dry road surface can be maintained. Therefore, according to this pneumatic tire, it is possible to achieve both running performance on an ice road surface and steering stability performance on a dry road surface.

  The pneumatic tire according to a second aspect of the present invention is the pneumatic tire according to the first aspect, wherein the sipe is a tire radial dimension D1 at an inner end in the tire width direction of the diameter-expanded portion up to the tread surface, and the tire radial dimension. The tire radial direction dimension D2 at the outer end in the tire width direction of the enlarged diameter portion passing through the outermost radial position of D1 to the reference plane orthogonal to the tire equator plane is 0.3 ≦ D2 / D1 ≦ 0. .7 relationship is satisfied.

  When D2 / D1 is 0.3 or more, the capacity for receiving sipe water tends to be improved. On the other hand, when D2 / D1 is 0.7 or less, the drainage effect of the enlarged diameter portion due to centrifugal force tends to be improved. According to this pneumatic tire, by satisfying the relationship of 0.3 ≦ D2 / D1 ≦ 0.7, it is possible to obtain the drainage effect of the enlarged diameter portion while maintaining the capacity of the sipe, and traveling on the road surface on ice. The performance can be maintained.

  In the pneumatic tire according to a third aspect of the present invention, in the first or second aspect, the sipe has a width W1 of the enlarged diameter portion and a sipe width W2 other than the enlarged diameter portion of 2.0. ≦ W1 / W2 ≦ 5.0 is satisfied.

  When W1 / W2 is 2.0 or more, the water removal effect and the drainage effect tend to be improved. On the other hand, when W1 / W2 is 5.0 or less, the rigidity of the land portion tends to be improved. According to this pneumatic tire, the dewatering effect and the drainage effect can be maintained, and the rigidity can be suppressed, the steering stability on the dry road surface can be maintained, and the edge effect can be maintained by suppressing the collapse of the sipe. .

  In the pneumatic tire according to a fourth aspect, in the third aspect, the sipe has a tire radial direction dimension D3 of the enlarged diameter portion and a sipe width W2 other than the enlarged diameter portion is 2.0. ≦ D3 / W2 ≦ 5.0 is satisfied.

  When D3 / W2 is 2.0 or more, the water removal effect and the drainage effect tend to be improved. On the other hand, when D3 / W2 is 5.0 or less, the rigidity of the land portion tends to improve. According to this pneumatic tire, the dewatering effect and the drainage effect can be maintained, and the rigidity can be suppressed, the steering stability on the dry road surface can be maintained, and the edge effect can be maintained by suppressing the collapse of the sipe. .

  The pneumatic tire according to a fifth aspect of the present invention is the pneumatic tire according to any one of the first to fourth aspects, wherein the diameter-enlarged portion gradually changes in diameter from the inner end in the tire width direction toward the outer end in the tire width direction. It is characterized by being formed.

  According to this pneumatic tire, the drainage effect in the enlarged diameter portion can be remarkably obtained.

  The pneumatic tire according to a sixth aspect of the present invention is the pneumatic tire according to any one of the first to fifth aspects, wherein the rotational direction with respect to the forward direction of the vehicle is specified when the vehicle is mounted, and the sipe is It is formed with an angle of 10 [°] or more and 40 [°] or less with respect to the tire width direction so that the outer end in the tire width direction in the extending direction is located behind the inner end in the tire width direction. It is characterized by that.

  According to this pneumatic tire, the drainage effect is improved by utilizing the rotational force of the tire by setting the sipe angle to 10 [°] or more. On the other hand, the edge effect in the tire circumferential direction is improved by setting the sipe angle to 40 [°] or less. For this reason, the running performance on an icy road surface can be improved.

  The pneumatic tire according to a seventh aspect of the present invention is the pneumatic tire according to any one of the first to sixth aspects, wherein the enlarged diameter portion is formed by terminating the inner end in the tire width direction within the land portion. And

  According to this pneumatic tire, since the rigidity of the land portion is improved by terminating the inner end in the tire width direction of the enlarged diameter portion in the land portion, it is possible to improve the steering stability on the dry road surface.

  In the pneumatic tire according to an eighth aspect of the present invention, in any one of the first to seventh aspects, the sipe is formed at least on the outermost land portion in the tire width direction.

  When traveling on a dry road surface, the force in the tire width direction is applied to the outermost land portion in the tire width direction. Therefore, by providing a sipe at least on the outermost land portion in the tire width direction and maintaining the rigidity of the land portion, the effect of maintaining the steering stability on the dry road surface can be remarkably obtained.

  The pneumatic tire according to the present invention can achieve both running performance on an icy road surface and steering stability performance on a dry road surface.

FIG. 1 is a plan view of a tread surface in a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a partial meridional sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 3 is a plan view of a tread surface of another example in the pneumatic tire according to the embodiment of the present invention. FIG. 4 is a perspective view of a land portion in the pneumatic tire according to the embodiment of the present invention. FIG. 5 is a perspective view of another example land portion of the pneumatic tire according to the embodiment of the present invention. FIG. 6 is a perspective view of another example land portion of the pneumatic tire according to the embodiment of the present invention. FIG. 7 is a partially enlarged meridional sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 8 is a perspective view of another example land portion in the pneumatic tire according to the embodiment of the present invention. FIG. 9 is a plan view of a tread surface of another example in the pneumatic tire according to the embodiment of the present invention. FIG. 10 is a perspective view of another example land portion of the pneumatic tire according to the embodiment of the present invention. FIG. 11 is a perspective view of another example land portion of the pneumatic tire according to the embodiment of the present invention. FIG. 12 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. Further, a plurality of modifications described in this embodiment can be arbitrarily combined within the scope obvious to those skilled in the art.

  FIG. 1 is a plan view of a tread surface in a pneumatic tire according to the present embodiment, FIG. 2 is a partial meridional sectional view of the pneumatic tire according to the present embodiment, and FIG. It is a top view of the tread surface of the other example in the pneumatic tire which concerns.

  In the following description, the tire radial direction refers to a direction orthogonal to the rotational axis (not shown) of the pneumatic tire, and the tire radial inner side refers to the side toward the rotational axis in the tire radial direction, the tire radial outer side, and Means the side away from the rotation axis in the tire radial direction. The tire width direction refers to a direction parallel to the rotation axis, the inner side in the tire width direction is the side toward the tire equatorial plane CL in the tire width direction, and the outer side in the tire width direction is the tire equatorial plane in the tire width direction. The side away from CL. The tire circumferential direction is a circumferential direction with the rotation axis as a central axis. The tire equatorial plane CL is a plane that is orthogonal to the rotational axis of the pneumatic tire and passes through the center of the tire width of the pneumatic tire.

  The pneumatic tire of the present embodiment is suitable as a studless tire or an all-season tire used on icy and snowy road surfaces. As shown in FIGS. 1 and 2, the pneumatic tire has a tread portion 1. The tread portion 1 is made of a rubber material, and is exposed at the outermost side in the tire radial direction of the pneumatic tire, and its surface (hereinafter referred to as a tread surface) 11 becomes the contour of the pneumatic tire. In the present embodiment, the tread surface 11 becomes a tread surface that comes into contact with the road surface when a vehicle (not shown) equipped with a pneumatic tire travels.

  As shown in FIGS. 1 to 3, the tread surface 11 includes a plurality of main grooves 2 extending in the tire circumferential direction and arranged in parallel in the tire width direction. Extending along the tire circumferential direction includes having an angle of ± 5 degrees or less (substantially 0 degrees) with respect to the tire circumferential direction. The main groove 2 refers to a groove whose width opened to the tread surface 11 is defined as 3 [mm] or more and a groove depth is defined as 4 [mm] or more on the basis of a new tire. The tread surface 11 extends along the tire circumferential direction by a plurality of main grooves 2, and a plurality of rib-like land portions 3 parallel to the tire equator surface are formed (see FIG. 3).

  Further, as shown in FIG. 1, the tread surface 11 is provided with a plurality of lug grooves 4 that are provided so as to intersect (communicate with) the main groove 2 and have edge components in the tire circumferential direction. . The lug groove 4 is provided parallel to the tire width direction or having a predetermined angle. In addition, the lug groove 4 may be bent or curved. The lug groove 4 refers to a main groove 2 or a groove depth that does not belong to the sipe 5 described later and has a groove depth equal to or less than the groove depth of the main groove 2 when the tire is new. The tread surface 11 is provided with a plurality of lug grooves 4 communicating with the main grooves 2 adjacent to each other in the tire width direction, so that the plurality of main grooves 2 and the plurality of lug grooves 4 form a rib-like land portion. 3 is formed as a plurality of block-like land portions 31. In FIG. 1, the block-shaped land portion 31 is illustrated. In addition, when the lug groove 4 is provided so as to communicate with only one of the main grooves 2 adjacent in the tire width direction, the rib-shaped land portion 3 is formed.

  A sipe 5 is formed on the tread surface 11 which is the surface of the land portion 3 (31) described above. The sipe 5 is opened in the tread surface 11, intersects in the tire circumferential direction, extends mainly in the tire width direction, and is cut into a narrow groove shape. In the present embodiment, as shown in FIGS. 1 to 3, the sipe 5 has the land portions 3 (31) on the outermost side in the tire width direction and the 3 (31) adjacent thereto in the tire width direction. It is provided as an opening sipe that penetrates the portion 3 (31) in the tire width direction. In the present embodiment, as shown in FIGS. 1 to 3, in the sipe 5, in the land portion 3 (31) at the center in the tire width direction, only the outer end in the tire width direction is set to the land portion 3 (31). It is provided as a one-sided open sipe that penetrates in the direction and is closed by closing the inner end in the tire width direction in the land portion 3 (31). Although not clearly shown in the figure, the sipe 5 may be provided as a closed sipe having both ends terminated in the land portion 3 (31) and closed. This sipe 5 is for improving the water removal effect of receiving water between the tread surface 11 and the tread surface 11 in the groove and the edge effect. One sipe land 3 or block land It is preferable that a plurality of 31 is formed. Note that the sipe 5 has a groove width of 1.2 [mm] or less opened on the tread surface 11 and a groove depth not more than the groove depth of the lug groove 4 on the basis of when the tire is new. Say.

  In the present embodiment, the sipe 5 is shown as a one-dimensional sipe in a one-dimensional shape formed linearly in the tire circumferential direction and the tire radial direction in FIGS. 1 and 3. Other than this one-dimensional sipe, although not shown in the figure, a two-dimensional sipe with a two-dimensional cut surface such as one that is bent or curved only in the tire circumferential direction or one that is bent or curved only in the tire radial direction. Alternatively, there is a three-dimensional sipe (three-dimensional sipe) in which the cut surfaces facing each other in the tire circumferential direction mesh with each other by bending or bending in the tire circumferential direction and the tire radial direction.

  4 is a perspective view of a land portion in the pneumatic tire according to the present embodiment, and FIGS. 5 and 6 are perspective views of another example land portion in the pneumatic tire according to the present embodiment. FIG. 7 is a partially enlarged meridional sectional view of the pneumatic tire according to the present embodiment.

  4 to 6, the block-shaped land portion 31 is shown, but the rib-shaped land portion 3 may be used. As shown in FIGS. 4 to 6, the land portion 31 is provided with a sipe 5 that opens in the tread surface 11 and extends in a direction intersecting the tire circumferential direction. The sipe 5 has an enlarged diameter portion 6 that is larger than the sipe width W2 at the groove bottom that becomes the tire radial direction inner end 5a.

  The enlarged diameter portion 6 opens at least on the side wall of the land portion 31 on the outer side in the tire width direction. That is, you may open to the side wall of the land part 31 inside the tire width direction. The diameter-enlarged portion 6 is formed by gradually changing the position outward in the tire radial direction from the inner end in the tire width direction toward the outer end in the tire width direction.

  As shown in FIG. 4, the enlarged diameter portion 6 is formed by gradually changing the position from the inner end in the tire width direction toward the outer end in the tire width direction toward the outer end in the tire width direction. There is a form in which it is inclined linearly outward in the tire radial direction toward the outer end in the tire width direction. In addition, as shown in FIG. 5, there is a form in which the enlarged diameter portion 6 is formed to be inclined in a curved shape outward in the tire radial direction from the inner end in the tire width direction toward the outer end in the tire width direction. Further, as shown in FIG. 6, the enlarged diameter portion 6 is partially formed along the tire width direction from the inner end in the tire width direction toward the outer end in the tire width direction, and the tip thereof is inclined outward in the tire radial direction ( There is a form that is formed in a straight line shape or a curved shape. That is, the diameter-enlarged portion 6 has no element extending from the tire width direction inner end toward the tire width direction outer end toward the tire radial direction inner side, and is formed by gradually changing the position only on the tire radial direction outer side.

  As described above, the pneumatic tire of the present embodiment intersects the tread surface 11 with the rib-like land portion 3 and / or the main groove 2 defined by the plurality of main grooves 2 extending in the tire circumferential direction. In a pneumatic tire having a block-like land portion 31 defined by a plurality of lug grooves 4 and main grooves 2, the land portions 3, 31 open to the tread surface 11 and intersect the tire circumferential direction. The sipe 5 has a sipe 5 having an enlarged diameter portion 6 that is larger than the sipe width W2 at the groove bottom that is the inner end 5a in the tire radial direction, and the enlarged diameter portion 6 includes at least the land portions 3 and 31. An opening is formed in the side wall on the outer side in the tire width direction, and the position is gradually changed from the inner end in the tire width direction to the outer end in the tire width direction toward the outer side in the tire radial direction.

  According to this pneumatic tire, a water removal effect and an edge effect for receiving water between the tread surface 11 and the tread surface 11 by the sipe 5 are obtained, and water removal performance is achieved by storing water in the enlarged diameter portion 6. It becomes possible to improve. Further, according to this pneumatic tire, the diameter-enlarged portion 6 opens at least on the side wall on the outer side in the tire width direction of the land portions 3, 31, so that the water received in the groove of the sipe 5 It becomes possible to drain to the outside in the tire width direction. In particular, according to this pneumatic tire, the diameter-expanded portion 6 is formed by gradually changing the position from the tire width direction inner end toward the tire width direction outer end toward the tire radial direction outer side. Since the water is drained by the action of the centrifugal force, the drainage can be improved. For this reason, it becomes possible to maintain the driving performance on the road surface on ice. On the other hand, the rigidity of the land portions 3 and 31 tends to decrease due to the arrangement of the sipe 5, but according to this pneumatic tire, the enlarged diameter portion 6 is tired from the inner end in the tire width direction toward the outer end in the tire width direction. Since the position is gradually changed to the outer side in the radial direction, the groove depth of the sipe 5 is shallower than the outer side in the tire width direction on the outer side in the tire width direction of the land portions 3, 31. The rigidity on the outer side in the tire width direction is higher than that on the inner side in the tire width direction. For this reason, it becomes possible to maintain the steering stability on the dry road surface. Therefore, according to this pneumatic tire, it is possible to achieve both running performance on an ice road surface and steering stability performance on a dry road surface.

  In addition, it is preferable to apply the above-described two-dimensional sipe and three-dimensional sipe in the sipe 5 because the rigidity of the land portions 3 and 31 can be maintained by supporting each of the facing cut surfaces.

  In the pneumatic tire of the present embodiment, the sipe 5 includes the tire radial direction dimension D1 at the inner end in the tire width direction of the enlarged diameter portion 6 and the tire radial direction dimension D2 at the outer end in the tire width direction of the enlarged diameter portion 6. Preferably satisfies the relationship of 0.3 ≦ D2 / D1 ≦ 0.7.

  When D2 / D1 is 0.3 or more, the capacity for receiving the water of the sipe 5 tends to be improved. On the other hand, when D2 / D1 is 0.7 or less, the drainage effect of the enlarged diameter portion 6 due to centrifugal force tends to be improved. According to this pneumatic tire, by satisfying the relationship of 0.3 ≦ D2 / D1 ≦ 0.7, it is possible to obtain the drainage effect of the enlarged diameter portion 6 while maintaining the capacity of the sipe 5, and on the road surface on ice. It is possible to maintain the running performance of the vehicle.

  In general, as shown in FIG. 2, the tread surface 11 is formed with a predetermined curvature gradually inward in the tire radial direction toward the outer side in the tire width direction, with the position of the tire equatorial plane CL being the outermost side in the tire radial direction. Yes. In particular, the outermost land portions 3 and 31 in the tire width direction are formed with a smaller curvature than the inner side in the tire width direction, as shown in FIG. Including such a case, the tire radial dimension D1 and the tire radial dimension D2 are defined as follows.

  That is, as shown in FIG. 7, the tire radial direction dimension D1 at the inner end in the tire width direction of the enlarged diameter portion 6 up to the tread surface 11 and the tire radial direction outermost position (tread surface 11) of the tire radial direction dimension D1. The tire radial direction dimension D2 at the outer end in the tire width direction of the enlarged diameter portion 6 up to the reference plane S orthogonal to the tire equatorial plane CL satisfies the relationship of 0.3 ≦ D2 / D1 ≦ 0.7.

  Moreover, in the pneumatic tire of this embodiment, as shown in FIG. 4, the sipe 5 has a width W1 of the enlarged diameter portion 6 and a sipe width W2 other than the enlarged diameter portion 6 of 2.0 ≦ W1 /. It is preferable to satisfy the relationship of W2 ≦ 5.0.

  When W1 / W2 is 2.0 or more, the water removal effect and the drainage effect tend to be improved. On the other hand, when W1 / W2 is 5.0 or less, the rigidity of the land portions 3 and 31 tends to be improved. According to this pneumatic tire, it is possible to maintain the dewatering effect and drainage effect, as well as maintain the steering stability on the dry road surface by suppressing the rigidity reduction and the edge effect by suppressing the collapse of the sipe. become.

  In the pneumatic tire of the present embodiment, as shown in FIG. 4, the sipe 5 has a tire radial direction dimension D3 of the enlarged diameter portion 6 and a sipe width W2 other than the enlarged diameter portion 6 of 2.0. It is preferable to satisfy the relationship of ≦ D3 / W2 ≦ 5.0.

  When D3 / W2 is 2.0 or more, the water removal effect and the drainage effect tend to be improved. On the other hand, when D3 / W2 is 5.0 or less, the rigidity of the land portions 3 and 31 tends to be improved. According to this pneumatic tire, it is possible to maintain the dewatering effect and drainage effect, as well as maintain the steering stability on the dry road surface by suppressing the rigidity reduction and the edge effect by suppressing the collapse of the sipe. become.

  FIG. 8 is a perspective view of another example land portion of the pneumatic tire according to the present embodiment. As shown in FIG. 8, in the pneumatic tire of the present embodiment, it is preferable that the enlarged diameter portion 6 is formed with a diameter that gradually increases from the inner end in the tire width direction toward the outer end in the tire width direction.

  According to this pneumatic tire, the drainage effect in the enlarged diameter portion 6 can be remarkably obtained.

  FIG. 9 is a plan view of a tread surface of another example in the pneumatic tire according to the present embodiment. As shown in FIG. 9, in the pneumatic tire of this embodiment, the rotational direction R with respect to the forward direction of the vehicle is specified when the vehicle is mounted, and the sipe 5 is on the outer side in the tire width direction in the extending direction. It is preferable that the angle is 10 [°] or more and 40 [°] or less with respect to the tire width direction so that the end is on the rear side in the rotation direction with respect to the inner end in the tire width direction.

  In addition, in FIG. 9, although it is a pneumatic tire which has the lug groove 4 and has the block-shaped land part 31, it is angle similarly about the pneumatic tire which has the rib-shaped land part 3 as shown in FIG. It is preferable to form with θ. FIG. 9 is viewed from above when the vehicle is mounted. The designation of the rotation direction R can be displayed by, for example, a mark or unevenness provided on the sidewall portion of the tire, or a catalog attached to the tire.

  According to this pneumatic tire, the drainage effect is improved by using the rotational force of the tire by setting the angle θ of the sipe 5 to 10 [°] or more. On the other hand, the edge effect in the tire circumferential direction is improved by setting the angle θ of the sipe 5 to 40 [°] or less. For this reason, it becomes possible to improve the running performance on the road surface on ice.

  10 and 11 are perspective views of other land portions of the pneumatic tire according to this embodiment. As shown in FIGS. 10 and 11, the enlarged diameter portion 6 is preferably formed by terminating the inner end in the tire width direction within the land portions 3 and 31.

  FIG. 10 shows a form in which the inner end of the sipe 5 itself in the tire width direction is terminated in the land portions 3 and 31. Further, in FIG. 11, the inner end in the tire width direction of the sipe 5 penetrates the inner side in the tire width direction of the land portions 3 and 31, but the inner end in the tire width direction of the enlarged diameter portion 6 is within the land portions 3 and 31. The form formed by terminating is shown.

  According to this pneumatic tire, since the rigidity of the land portions 3, 31 is improved by terminating the inner end in the tire width direction of the enlarged diameter portion 6 within the land portions 3, 31, steering stability on a dry road surface It becomes possible to improve.

  In the pneumatic tire of the present embodiment, the sipe 5 is preferably formed at least on the outermost land portions 3 and 31 in the tire width direction.

  When traveling on a dry road surface, the force in the tire width direction is applied to the outermost land portions 3 and 31 in the tire width direction. Therefore, by providing the sipe 5 at least on the outermost land portions 3 and 31 in the tire width direction and maintaining the rigidity of the land portions 3 and 31, the effect of maintaining the steering stability on the dry road surface is remarkably obtained. It becomes possible.

  In this example, performance tests on ice road running performance and dry road handling stability performance were performed for a plurality of types of pneumatic tires with different conditions (see FIG. 12).

  In this performance test, a pneumatic tire having a tire size of 195 / 65R15 is assembled to a regular rim (15 × 6J), filled with a regular internal pressure (230 [kPa]), and applied to a test vehicle (domestic 1.4-liter FF vehicle). Installed.

  The regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO.

  In the evaluation method of the icy road surface running performance, the time required for the vehicle to make a steady turn on a circle with a radius of 30 [m] on the icy test road is measured by the test vehicle. Then, based on the measurement result, index evaluation using the conventional example as a reference (100) is performed. In this evaluation, the index is preferably 96 or more, and the larger the index, the higher the running performance on the road surface on ice.

  In the dry road surface steering stability evaluation method, the driver evaluates the initial responsiveness when the driving lane is changed while driving the test road of a straight dry road surface at 60 [km / h] with the above test vehicle by sensory evaluation. did. In this case, an index evaluation is performed with an average of evaluations by five drivers as an evaluation point and a conventional example as a reference (100). In this evaluation, the index is preferably 98 or more, and the larger the index is, the higher the steering stability performance on the dry road surface is.

  In FIG. 12, the conventional example, the comparative example, and the pneumatic tires of Examples 1 to 16 are provided with a sipe having an enlarged diameter portion at the inner end in the tire radial direction on the tread surface of the land. In the sipe, the tire radial direction dimension D1 at the inner end in the tire width direction of the enlarged diameter portion to the tread surface is 7.5 [mm], and the sipe width W2 is 0.4 [mm].

  In the conventional pneumatic tire, the diameter-expanded portion opens on the side walls on both sides of the land width direction of the land portion, and the position is constant in the tire radial direction from the inner end in the tire width direction toward the outer end in the tire width direction. Has been. Further, in the pneumatic tire of the comparative example, the enlarged diameter portion is formed by opening in the sidewalls on both sides of the land portion in the tire width direction and inclining inward in the tire radial direction from the inner end in the tire width direction toward the outer end in the tire width direction. Has been.

  On the other hand, in the pneumatic tires of Examples 1 to 16, the diameter-enlarged portion opens on the side wall on the outer side in the tire width direction of the land portion, and the outer side in the tire radial direction from the inner end in the tire width direction toward the outer end in the tire width direction. It is formed to be inclined. In the pneumatic tires of Examples 1 to 12 and Example 14, the diameter-expanded portion is formed to open on the side walls on both sides in the tire width direction of the land portion (see FIG. 4). In the pneumatic tires of Examples 1 to 13, sipes are arranged in land portions other than the outermost side in the tire width direction in FIG. In the pneumatic tires of Examples 3 to 16, D2 / D1 is within a specified range. In the pneumatic tires of Examples 6 to 16, W1 / W2 and D3 / W2 are within the specified ranges. In the pneumatic tires of Examples 9, 12, 14, and 16, the diameter-expanded portion is formed so that the diameter gradually increases toward the outer side in the tire radial direction (see FIG. 8). In the pneumatic tires of Examples 10 to 16, the sipe angle is in a predetermined arrangement and range. The pneumatic tires of Examples 13, 15, and 16 are formed by terminating the inner end in the tire width direction of the enlarged diameter portion in the land portion. In the pneumatic tires of Examples 14 to 16, sipes are arranged in the outermost land portion in the tire width direction in FIG.

  As shown in the test results of FIG. 12, it can be seen that the pneumatic tires of Examples 1 to 16 have improved on-ice road running performance and dry road handling stability.

DESCRIPTION OF SYMBOLS 1 Tread part 11 Tread surface 2 Main groove 3,31 Land part 4 Lug groove 5 Sipe 5a Tire radial direction inner side end 6 Diameter expansion part

Claims (8)

A rib-shaped land portion defined by a plurality of main grooves extending in the tire circumferential direction on the tread surface and / or a block defined by a plurality of lug grooves and the main grooves intersecting the main grooves. In a pneumatic tire having a land portion of a shape,
The land portion includes a sipe having an enlarged diameter portion that is open to the tread surface and extends in a direction intersecting the tire circumferential direction, and has a diameter larger than the sipe width at an inner end in the tire radial direction,
The enlarged-diameter portion is formed at least at the side wall on the outer side in the tire width direction of the land portion, and is formed by gradually changing the position on the outer side in the tire radial direction from the inner end in the tire width direction toward the outer end in the tire width direction. A pneumatic tire characterized by that.   The sipe passes through the tire radial direction dimension D1 at the inner end in the tire width direction of the enlarged diameter portion to the tread surface and the tire radial direction outermost position of the tire radial direction dimension D1 and is orthogonal to the tire equator plane. 2. The air according to claim 1, wherein a tire radial direction dimension D <b> 2 at an outer end in the tire width direction of the enlarged diameter portion to the reference surface satisfies a relationship of 0.3 ≦ D2 / D1 ≦ 0.7. Enter tire.   The sipe is characterized in that a width W1 of the enlarged diameter portion and a sipe width W2 other than the enlarged diameter portion satisfy a relationship of 2.0 ≦ W1 / W2 ≦ 5.0. 2. The pneumatic tire according to 2.   In the sipe, a tire radial direction dimension D3 of the enlarged diameter portion and a sipe width W2 other than the enlarged diameter portion satisfy a relationship of 2.0 ≦ D3 / W2 ≦ 5.0. Item 4. The pneumatic tire according to Item 3.   The pneumatic diameter according to any one of claims 1 to 4, wherein the diameter-enlarged portion is formed by gradually changing the diameter from the inner end in the tire width direction toward the outer end in the tire width direction. tire.   When the vehicle is mounted, the rotation direction with respect to the forward direction of the vehicle is specified, and the sipe is such that the outer end in the tire width direction in the extending direction is located behind the inner end in the tire width direction. The pneumatic tire according to claim 1, wherein the pneumatic tire is formed at an angle of 10 ° to 40 ° with respect to the tire width direction.   The pneumatic tire according to any one of claims 1 to 6, wherein the enlarged-diameter portion is formed by terminating a tire width direction inner end in the land portion.   The pneumatic tire according to claim 1, wherein the sipe is formed at least on the outermost land portion in the tire width direction.

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