JP6417200B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a land portion sandwiched between circumferential grooves on a tire tread side.

  Pneumatic tires having land portions sandwiched between circumferential grooves on the tire tread side are widely used. In such a pneumatic tire, the land tread has a convex shape, i.e., the center of the land tread is projected over the circumferential groove adjacent portion of the land tread, thereby increasing the contact pressure. A region to be formed is formed at the center of the land portion to improve the steering stability related to the initial steering performance (see, for example, Patent Document 1).

JP2012-116410

  However, when a convex region is formed at the center of the land, a water film easily enters from the periphery of the land, which is not preferable from the viewpoint of drainage. In particular, when turning, this problem becomes prominent because the water film easily enters from the circumferential groove adjacent portions on both sides sandwiching the land surface.

  The present invention has been made in view of the above problems, and provides a pneumatic tire that suppresses the infiltration of a water film from the periphery of the land portion tread while maintaining a high contact pressure at the center of the land portion. Is an issue.

  The pneumatic tire according to the present invention is a pneumatic tire having a land portion sandwiched between circumferential grooves on the tire tread side, wherein the tread surface of the land portion has a convex shape in a cross section in the tire width direction. The height difference in the tire radial direction between the top of the tread and the vehicle mounting inner end of the tread is represented by hi, and the height difference in the tire radial direction between the top of the tread and the vehicle mounted outer end of the tread is represented by ho < The width direction imaginary straight line that satisfies the relationship of hi and passes through the vehicle mounting outer end of the inner circumferential groove adjacent to the vehicle mounting inner side of the land portion of the circumferential groove and extends in the tire radial direction is lo, The width direction end virtual straight line extending in the tire radial direction passing through the vehicle mounting inner end of the circumferential groove is denoted by li, and the intermediate position virtual straight line extending in the tire radial direction passing through an intermediate position between lo and li is denoted by lc, The deepest position of the inner circumferential groove perpendicular to lc Lb is the deepest virtual straight line passing through L, s i is the cross-sectional area of the land surrounded by lo, lb and li, S i is the cross-sectional area of the land surrounded by li, lc and lb, and If the land cross-sectional area of the region corresponding to the region indicating Sii with respect to the outer circumferential groove adjacent to the outer side of the vehicle mounted on the vehicle is defined as Soi, the relationship of Soi <Sio is satisfied.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which suppressed the penetration | invasion of the water film from the periphery of a land part tread can be provided, maintaining the high contact pressure in a land part center.

In the pneumatic tire concerning one embodiment of the present invention, it is a top view for explaining a land part and a circumferential direction groove. It is the sectional view on the AA line of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. The following embodiments are exemplifications for embodying the technical idea of the present invention, and the embodiments of the present invention are described below in terms of the material, shape, structure, arrangement, etc. of the components. It is not limited to. The embodiments of the present invention can be implemented with various modifications without departing from the scope of the invention.

  FIG. 1 is an example of a pneumatic tire according to an embodiment of the present invention (hereinafter referred to as the present embodiment), and is a plan view for explaining a land portion and a circumferential groove, and FIG. FIG. The pneumatic tire of the present embodiment includes a plurality of circumferential grooves (circumferential main grooves) extending in the tire circumferential direction U, and a plurality of land portions defined by these circumferential grooves.

  Hereinafter, in the present embodiment, three ribs 20, 22, 24 are partitioned by the four circumferential grooves 10, 12, 14, 16 into the center region of the tread portion 28, and a pair of left and right ribs 30, An example of a pneumatic tire 34 in which 32 is partitioned into a shoulder region of the tread portion 28 will be described. In the present embodiment, the tire equatorial plane CL passes through the central rib 20 among the three ribs.

  As shown in FIGS. 1 and 2, the tread surface 23 of the rib 22 has a convex shape in the cross section in the tire width direction. Then, the difference in height in the tire radial direction between the vertex 23p of the tread 23 and the vehicle mounting inner end 23i of the tread 23 (tire radial drop height) is hi, and the vehicle mounting outer end 23o of the tread 23p and the tread 23 is the vehicle mounting outer end 23o. If the difference in height in the tire radial direction with respect to is ho, the relationship of hi> ho is satisfied. Note that the vehicle mounting inner end 23i of the tread 23 can be said to be an intersection of the widthwise end of the circumferential groove 10 on the outer side of the vehicle mounting (that is, the vehicle mounting outer end 10o of the circumferential groove 10) and the tread 23. It can be said that the vehicle mounting outer end 23 o is an intersection of the widthwise end of the circumferential groove 14 on the vehicle mounting inner side (that is, the vehicle side wearing inner end 14 i of the circumferential groove 14) and the tread surface 23.

  Further, the circumferential groove 10 extends in the tire radial direction D through the vehicle mounting outer end 10o of the circumferential groove 10 adjacent to the vehicle mounting inner side (IN side) of the rib 22 (hereinafter referred to as the inner circumferential groove 10). Let the width direction virtual imaginary straight line be lo, and let the width direction virtual imaginary straight line that extends in the tire radial direction D through the vehicle wearing inner edge 10i of the inner circumferential groove 10 be li. An intermediate position imaginary straight line passing through an intermediate position between lo and li and extending in the tire radial direction D is defined as lc, and a deepest imaginary straight line orthogonal to lc and passing through the deepest position 10q of the inner circumferential groove 10 is defined as lb. . A rib cross-sectional area surrounded by lo, lc and lb is Sio, and a rib cross-sectional area surrounded by li, lc and lb is Sii. In addition, regarding the circumferential groove 14 (hereinafter referred to as the outer circumferential groove 14) adjacent to the vehicle mounting outside (OUT side) of the rib 22 among the circumferential grooves, the rib cross-sectional area of the region corresponding to the region indicating Sii is represented by Soi. Then, the relationship of Soi <Sio is satisfied.

  Further, in the present embodiment, the relationship of Sio> Sii is satisfied in the inner circumferential groove 10. Regarding the outer circumferential groove 14, assuming that the rib cross-sectional area of the region corresponding to the region indicating Sio is Soo, the relationship of Soi <Soo is satisfied in this embodiment.

  In the present embodiment, in the tire width direction cross section, the inner circumferential groove 10 has a groove bottom surface 10b, a groove wall surface 10w, and a circular arc portion 10r corresponding to a groove bottom corner that connects the two. When the circular arc portion 10r is an outer circular arc portion 10or outside the vehicle mounting and an inner circular arc portion 10ir inside the vehicle mounting in the groove cross section, the minimum curvature radius of the outer circular arc portion 10or is R1, and the minimum curvature radius of the inner circular arc portion 10ir. When R2 is R2, the relationship of R1> R2 is satisfied. Here, the reason why the radius of curvature is the minimum is that the arc portion 10r may be formed by one arc or a plurality of arcs continuously connected.

  Further, in the present embodiment, the angle formed by the groove wall surface 10w and lo at the vehicle mounting outer end 10o of the inner circumferential groove 10 is α, and the groove wall surface 10w and li at the vehicle mounting inner end 10i of the inner circumferential groove 10 is li. If the angle formed by β is β, the relationship α> β is satisfied.

  Furthermore, it is desirable that the groove wall angle (α) on the vehicle mounting outer side is in the range of the groove wall angle (β) on the vehicle mounting inner side + 2 ° to 30 °. If it is less than 2 degrees, it is difficult to achieve the optimum balance between steering stability and drainage, and if it exceeds 30 degrees, the left and right balance may deteriorate in the groove. , Drainage can be at a high level.

  Specifically, when the groove wall angle (β) on the vehicle mounting inner side is set to 10 °, for example, the groove wall angle (α) on the vehicle mounting outer side is preferably set to 12 ° to 40 °. In addition, Preferably it is set as the range of + 2-10 degrees.

(Function, effect)
Hereinafter, the operation and effect of the present embodiment will be described. In the present embodiment, with respect to the drop heights hi and ho of the tread 23 of the rib 22, the drop height (the difference in height in the tire radial direction) ho on the outside of the vehicle is made smaller than the drop height hi on the inside of the vehicle. In addition, it is possible to effectively improve the contact pressure near the center of the ribs and improve the handling stability while suppressing the intrusion from the outside of the vehicle mounting where the water film easily enters between the contact surface and the tread surface 23 when turning. .

  Also, during turning (cornering), a greater lateral force acts on the outer side of each rib mounted on the vehicle than on the inner side of the vehicle. In this embodiment, since the relationship of α> β is satisfied, the groove wall surface on the vehicle mounting outer side of each rib is closer to the tire radial direction than the groove wall surface on the vehicle mounting inner side (that is, the tire diameter). Small angle with the direction). Thereby, the rib deformation by the lateral force at the time of turning can be suppressed effectively.

  And by simply doing the drop height in this way to improve steering stability, the rigidity balance of the ribs 22 differs in the rib width direction W (tire width direction), which may be a concern for uneven wear, In the present embodiment, the rib cross-sectional area Sio on the vehicle-mounted inner circumferential groove 10 (inner circumferential groove 10) side with weak rib rigidity and the vehicle-mounted outer circumferential groove 14 (outer circumferential groove with strong rib rigidity). The rib cross-sectional area Soi on the 14) side satisfies the relationship Soi <Sio, and the rib rigidity is balanced so as to reduce the difference in rigidity between the ribs 22 on both circumferential grooves.

  Therefore, the pneumatic tire 34 can achieve both steering stability on a dry road surface, steering stability when turning on a wet road surface, and uneven wear resistance.

  In the present embodiment, the relationship of Sio> Sii is satisfied. If the rib cross-sectional areas on both sides of the inner circumferential groove 10 are increased (that is, if both Sio and Sii are increased), there is a concern that the drainage performance is lowered, but the rib cross-sectional area only on the side where higher ground pressure is desired to be maintained. By increasing Sio, the drainage can be easily maintained at a high level. The same can be said for the outer circumferential groove 14.

  Further, the relationship of R1> R2 is satisfied, where R1 is the minimum radius of curvature of the outer arcuate portion 10or outside the vehicle and R2 is the minimum radius of curvature of the inner arcuate portion 10ir inside the vehicle. That is, the relationship of Sio> Sii can be easily satisfied by increasing the minimum radius of curvature on the vehicle-mounted outer side as compared with that on the vehicle-side inner side. Further, if the curvature radii of both the outer arc portion 10or and the inner arc portion 10ir corresponding to the corners of the groove bottom are increased, the groove protrudes to the inside of the groove, so that the groove cross-sectional area decreases, that is, the drainage performance decreases. However, in this embodiment, only R1 (the minimum radius of curvature of the outer circular arc portion 10or) is relatively large, so that it is possible to maintain the steering stability at a high level while suppressing a decrease in drainage. it can.

  In addition, the angle formed by the groove wall surface 10w and lo at the vehicle mounting outer end 10o of the inner circumferential groove 10 is α, and the angle formed by the groove wall surface 10w and li at the vehicle mounting inner end 23i of the inner circumferential groove 10 is α. Assuming β, the relationship α> β is satisfied.

  If the outer circular arc portion 10or and the inner circular arc portion 10ir are asymmetric, distortion tends to be concentrated on the small curvature side, which may cause a groove crack or the like. In this embodiment, the groove wall angle (α) on the vehicle mounting outer side satisfies the relationship of the groove wall angle (β) on the vehicle mounting inner side, that is, the groove wall angle β on the vehicle mounting outer side on the side having a smaller curvature radius. However, since it is smaller than the groove wall angle α on the vehicle mounting inner side which is the side with the larger radius of curvature, it is possible to effectively suppress the rib deformation on the outer side of the vehicle mounting on the side with the smaller curvature radius when turning. Strain concentration can be effectively avoided.

  Furthermore, since the rigidity balance on the left and right sides becomes uniform with respect to the groove center, it is possible to achieve both high drainage and groove bottom cracking properties while ensuring steering stability.

  Further, when α is less than β + 2 °, there is a disadvantage that it is difficult to achieve the optimum balance between steering stability and drainage, and when α exceeds β + 30 °, the right and left balance in the groove may be deteriorated. . In the present embodiment, since α is in the range of β + 2 ° to 30 °, steering stability and drainage can be maintained at a high level.

  The (minimum curvature radius) R1 of the outer arc portion 10or is desirably three times or less than the minimum curvature radius R2 of the inner arc portion 10ir. If it exceeds 3 times, the left-right balance in the groove deteriorates, but if it is within 3 times, the influence on the steering stability is small. The outer circumferential groove 14 has the same structure as the inner circumferential groove 10.

  The minimum radius of curvature (R1) of the outer arc portion 10or is preferably 3 mm to 12 mm. This is because if R1 is smaller than 3 mm, it is difficult to ensure steering stability, and if it is larger than 12 mm, the cross-sectional area is reduced, affecting drainage.

  The minimum radius of curvature (R2) of the inner arc portion 10ir is preferably 2 mm to 6 mm. This is because if R2 is smaller than 2 mm, the cracking property is lowered, and if it is larger than 6 mm, the drainage property is affected.

  Also, α (groove wall angle on the vehicle mounting outer side) and β (groove wall angle on the vehicle mounting inner side) are preferably within 0 to 30 °.

  Moreover, satisfying the relationship of hi / ho <Sio / Soi is preferable from the viewpoint of optimum balance. In addition, Sio / Soi is preferably in the range of 2 to 6.

  Further, as shown in FIG. 2, it is preferable that the apex 23p of the tread surface 23 is unevenly distributed on the vehicle mounting outer side in the rib width direction W. As a result, it is possible to further prevent the water film from entering between the ground contact surface and the tread surface 23, and to further improve the steering stability when turning on a wet road surface.

  Hi / ho is preferably in the range of more than 1.0 and 3.5 or less.

  In the above description, the rib 22 and the circumferential groove 10 (inner circumferential groove) and the circumferential groove 14 (outer circumferential groove) adjacent thereto are described in detail, but the same applies to other ribs and circumferential grooves. It is preferable that it is set as this structure. The same applies to a tire in which blocks are arranged instead of ribs as land portions.

  Furthermore, it is preferable that conditions similar to those of the rib 22, that is, relationships such as hi> ho and Soi <Sio are satisfied in the entire land portion on the inner side in the tire width direction from the shoulder land portion (shoulder rib). In this case, it is more preferable that the dimensions of each land portion are adjusted so that the ho becomes smaller toward the land portion outside the vehicle.

DESCRIPTION OF SYMBOLS 10 ... Circumferential groove, inner circumferential groove (circumferential groove), 10b ... groove bottom surface, 10w ... groove wall surface, 10r ... arc portion, 10or ... outer arc portion, 10ir ... inner arc portion, 12 ... circumferential groove, 14 ... circumferential groove, outer circumferential groove (circumferential groove), 16 ... circumferential groove, 20 ... rib (land portion), 22 ... rib (land portion), 23 ... tread surface, 23p ... apex, 23i ... vehicle mounting inside End, 23o ... Outer end of vehicle mounting, 24 ... Rib (land portion), 28 ... Tread portion, 34 ... Pneumatic tire, D ... Tire radial direction

Claims (11)

A pneumatic tire having a land portion sandwiched between circumferential grooves on the tire tread side,
In the tire width direction cross section,
The land surface has a convex shape,
If the height difference in the tire radial direction between the apex of the tread and the vehicle mounting inner end of the tread is hi, and the height difference in the tire radial direction between the apex of the tread and the vehicle mounting outer end of the tread is ho,
ho <hi
Satisfy the relationship
Of the circumferential grooves, the width direction end imaginary straight line extending in the tire radial direction through the vehicle mounting outer end of the inner circumferential groove adjacent to the vehicle mounting inner side of the land portion is lo, the vehicle mounting of the inner circumferential groove An imaginary straight line in the width direction extending in the tire radial direction passing through the inner end is defined as li, an imaginary straight line extending in the tire radial direction passing through an intermediate position between lo and li is defined as lc, and orthogonal to lc. The deepest virtual straight line passing through the deepest position of the circumferential groove is lb , the land section area surrounded by lo, lc, lb is Sio, the land section area surrounded by li, lc, lb is Sii, Of the directional grooves, the land cross-sectional area of the region corresponding to the region indicating Sii with respect to the outer circumferential groove adjacent to the vehicle-mounted outer side of the land portion is defined as Soi.
Soi <Sio
Pneumatic tire that satisfies the relationship. Sio> Sii
The pneumatic tire according to claim 1, wherein the relationship is satisfied.   The pneumatic tire according to claim 1 or 2, wherein hi / ho is in a range of greater than 1.0 and not greater than 3.5. In the tire width direction cross section, each of the inner circumferential groove and the outer circumferential groove has a groove bottom surface, a groove wall surface, and an arc portion corresponding to a groove bottom corner portion connecting both,
When the arc portion is an outer arc portion outside the vehicle mounting and an inner arc portion inside the vehicle mounting in the groove cross section, the minimum radius of curvature of the outer arc portion is R1, and the minimum radius of curvature of the inner arc portion is R2.
R1> R2
The pneumatic tire according to claim 3, satisfying the relationship:   The pneumatic tire according to claim 4, wherein R1 is three times or less of R2. The angle formed by the groove wall surface at the vehicle mounting outer end of the inner circumferential groove and the lo is α, and the angle formed by the groove wall surface at the vehicle mounting inner end of the inner circumferential groove and li is β,
α> β
The pneumatic tire according to claim 4 or 5, satisfying the relationship:   The pneumatic tire according to claim 6, wherein α is in a range of β + 2 ° to 30 °. hi / ho <Sio / Soi
The pneumatic tire according to any one of claims 1 to 7, satisfying the relationship:   The pneumatic tire according to any one of claims 1 to 8, wherein an apex of the tread surface is unevenly distributed on a vehicle mounting outer side in a land portion width direction.   The pneumatic tire according to any one of claims 1 to 9, wherein the tire land portion applied as the land portion is a whole land portion on the inner side in the tire width direction from the shoulder land portion.   The pneumatic tire according to claim 10, wherein the dimensions of each land portion are adjusted so that ho becomes smaller toward a land portion outside the vehicle.

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