JP2013193512A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of exhibiting excellent hydroplaning preventing performance.SOLUTION: A surface of a tread part 3 includes a center land part 8C, a mediate land part 8M, a shoulder land part 8S, a circumferential main groove 91, and a circumferential main groove 92. A cross sectional height He of the center land part 8C in a tire equator CL is larger than a cross sectional height H1i of an inside wall surface of the circumferential main groove 91, and a cross sectional height H1o of an outside wall surface of the circumferential main groove 91 is larger than the cross sectional height H1i of the inside wall surface of the circumferential main groove 91 and a cross sectional height H2i of an inside wall surface of the circumferential main groove 92, and moreover, a cross sectional height H2o of an outside wall surface of the circumferential main groove 92 is equal to or smaller than the cross sectional height H2i of the inside wall surface of the circumferential main groove 92. At the same time, a difference h1 between the cross sectional height He and the cross sectional height H1i, a difference h2 between the cross sectional height H1o and the cross sectional height H2i, and a difference h3 between the cross sectional height H2o and the cross sectional height H2i satisfy a relationship h1>h2>h3≥0.

Description

  The present invention relates to a pneumatic tire capable of exhibiting excellent hydroplaning prevention performance.

  Conventionally, drainage is improved by increasing the groove width and depth of the circumferential main groove, thereby improving the hydroplaning prevention performance. However, when the groove width and groove depth of the circumferential main groove are increased, the rigidity of the land portion is reduced, and the steering stability performance tends to be reduced. Therefore, it is strongly desired to propose a method that can exhibit excellent hydroplaning prevention performance without enlarging the groove width and groove depth of the circumferential main groove.

  In Patent Document 1, the center portion of the center rib has a smooth convex shape toward the outer side in the tire radial direction and bulges from the virtual tread profile line to the outer side in the tire radial direction, and the edge portion of the center rib is the virtual tread profile line. Pneumatic tires that are depressed more radially inward than the tire are described. However, the land portions other than the center rib extend in an arc shape along the virtual tread profile line, and the improvement effect on the hydroplaning prevention performance is not sufficient.

  In Patent Document 2, a plurality of land portions partitioned by a circumferential main groove are provided with protrusions on at least one surface thereof, and the central portion of the land portion is formed in an arc shape outward from the virtual tread surface. A pneumatic radial tire formed to be convex is described. However, if the above-mentioned protrusion is provided on the land located outside the tire width direction, the flow of water to the center of the tread, which is the starting point of hydroplaning, cannot be reduced sufficiently, and drainage outside the ground plane is obstructed. This makes it difficult to prevent hydroplaning.

  Although Patent Documents 3 to 6 describe tires in which various countermeasures are taken with respect to the surface structure of the tread portion, means for effectively improving the hydroplaning prevention performance is disclosed in any of the above documents. Not.

JP 2005-31890 A JP 2009-161001 A JP 11-123909 A JP 2001-287510 A JP 2004-122904 A JP 2006-168638 A

  This invention is made | formed in view of the said situation, The objective is to provide the pneumatic tire which can exhibit the outstanding hydroplaning prevention performance.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention includes, on the surface of the tread portion, a center land portion that passes through the tire equator, a mediate land portion that is located on the outer side in the tire width direction of the center land portion, and the mediate land portion. A shoulder land portion located on the outer side in the tire width direction, a first circumferential main groove that divides the center land portion and the mediate land portion, and a medial land portion and the shoulder land portion. In the pneumatic tire provided with two circumferential main grooves, the sectional height He of the center land portion at the tire equator is larger than the sectional height H1i of the inner wall surface of the first circumferential main groove. The sectional height H1o of the outer wall surface of the first circumferential main groove is determined from the sectional height H1i of the inner wall surface of the first circumferential main groove and the sectional height H2i of the inner wall surface of the second circumferential main groove. Bigger, said The sectional height H2o of the outer wall surface of the second circumferential main groove is equal to or smaller than the sectional height H2i of the inner wall surface of the second circumferential main groove, and the sectional height He and the sectional height H1i Satisfying the relationship of h1> h2> h3 ≧ 0, where h1 is the difference between the cross-section height H1o and the cross-section height H2i, and h3 is the difference between the cross-section height H2o and the cross-section height H2i. It is.

  In this tire, the cross-section height He is larger than the cross-section height H1i and satisfies the relationship of h1> h2> h3. Therefore, in the center land portion, the ground contact length (the tire circumferential direction length on the ground contact surface) is increased and the ground contact is made. Pressure increases. Moreover, since the cross-sectional height 1o is larger than the cross-sectional height H1i and the cross-sectional height H2i, in the mediate land portion, the ground pressure increases on the side close to the center land portion. By these, the flow of the water to the tread center used as the starting point of hydroplaning can be reduced. In addition, since the cross-section height H2o is equal to or smaller than the cross-section height H2i and satisfies the relationship of h1> h2> h3, the ground contact length is shortened at the shoulder land, and drainage outside the ground contact surface is efficient. To be done. As a result, excellent anti-hydroplaning performance is exhibited.

  In the present invention, it is preferable that the cross-sectional height H2o is smaller than the cross-sectional height H2i and satisfies the relationship of h3> 0. Thereby, since the contact length of the shoulder land portion is further shortened, drainage to the outside of the contact surface is further promoted, and the prevention performance of hydroplaning can be effectively improved.

  In the present invention, it is preferable that the surface of the center land portion is formed by an arcuate surface having a vertex at the center in the width direction of the tire equator or the center land portion and protruding outward. According to such a configuration, since the contact pressure at the center in the width direction of the tire equator or the center land portion is increased, the flow of water to the center of the tread can be accurately reduced, and the occurrence of hydroplaning can be effectively suppressed.

  In the present invention, it is preferable that the difference h1 between the cross-sectional height He and the cross-sectional height H1i is in the range of 0.5 to 2.0 mm. By setting the difference h1 to be 0.5 mm or more, the effect of increasing the contact length of the center land portion and increasing the contact pressure of the center land portion is appropriately ensured. In addition, by setting the difference h1 to 2.0 mm or less, the rigidity of the center land portion is appropriately maintained, and deterioration of the steering stability performance and wear resistance performance can be avoided.

  In the present invention, it is preferable that a chamfer of a surface side edge is formed on at least one of the outer wall surface of the first circumferential main groove and the outer wall surface of the second circumferential main groove. By forming the chamfer as described above, the edge effect of the mediate land portion and the shoulder land portion can be enhanced, and the steering stability performance can be improved.

Tire meridian cross-sectional view showing an example of a pneumatic tire according to the present invention Sectional drawing which shows the principal part of the pneumatic tire of FIG. Sectional view schematically showing the center land Sectional view schematically showing the mediate land Sectional view schematically showing the shoulder land Sectional drawing of the tread part which concerns on another embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. A pneumatic tire T shown in FIG. 1 includes a pair of bead portions 1, sidewall portions 2 extending outward in the tire radial direction from each of the bead portions 1, and tire radial direction outer ends of the sidewall portions 2. And a tread portion 3 connected to the front. The carcass layer 4 is provided in a toroidal shape between the pair of bead portions 1 and is wound up so that the end portions sandwich the bead core 1a and the bead filler 1b.

  In the tread portion 3, on the outer side of the carcass layer 4, a belt layer 5 constituted by a plurality of belt plies, a belt reinforcing layer 6 formed by rubber covering a cord extending substantially in the tire circumferential direction, and a tread rubber 7 And are provided. Each belt ply is formed by covering a cord extending obliquely with respect to the tire circumferential direction with rubber, and the cords are laminated so as to cross each other in opposite directions. The belt reinforcing layer 6 may be omitted as necessary. A tread strip 7 a is joined to the side of the tread rubber 7.

  On the surface of the tread portion 3, five land portions and four circumferential main grooves that divide the land portions are formed. Specifically, the center land portion 8C passing through the tire equator CL, which is the center of the tire width, a pair of mediate land portions 8M located on the outer side in the tire width direction of the center land portion 8C, and the tires of the mediate land portion 8M A pair of shoulder land portions 8S located on the outer side in the width direction, a first circumferential main groove 91 that divides the center land portion 8C and the mediate land portion 8M, a mediate land portion 8M, and a shoulder land portion 8S A partitioning second circumferential main groove 92 is formed.

  The circumferential main grooves 91 and 92 each extend continuously in the tire circumferential direction. Although illustration is omitted, in this embodiment, the center land portion 8C is constituted by a rib extending continuously in the tire circumferential direction, and the mediate land portion 8M and the shoulder land portion 8S are constituted by a block row divided by a lateral groove. ing. However, the present invention is not limited to this, and each land portion may be either a rib or a block row. The shoulder land portion 8S includes a ground contact end CE and is located on the outermost side in the tire width direction within the ground contact surface.

  As shown in FIGS. 2 to 5, in this pneumatic tire T, the cross-sectional height He of the center land portion 8 </ b> C at the tire equator CL is larger than the cross-sectional height H <b> 1 i of the inner wall surface of the circumferential main groove 91. The cross-sectional height H1o of the outer wall surface of the main groove 91 is larger than the cross-sectional height H1i of the inner wall surface of the circumferential main groove 91 and the cross-sectional height H2i of the inner wall surface of the circumferential main groove 92. The cross-sectional height H2o of the outer wall surface is the same as or smaller than the cross-sectional height H2i of the inner wall surface of the circumferential main groove 92. In addition, the difference h1 between the sectional height He and the sectional height H1i, the difference h2 between the sectional height H1o and the sectional height H2i, and the difference h3 between the sectional height H2o and the sectional height H2i are h1> h2>. The relationship of h3 ≧ 0 is satisfied.

  In a normal tire, the surface of the tread portion follows an arcuate contour line that smoothly connects the ground contact ends on both sides, whereas the tire T is not formed as such, and the surface of the tread portion 3 is It does not follow the arcuate outline OL. Specifically, the surfaces of the center land portion 8C and the mediate land portion 8M protrude outward from the contour line OL, and the surface of the shoulder land portion 8S is recessed inward from the contour line OL. The contour line OL is an arcuate virtual line that smoothly connects the ground contact ends CE on both sides and the surface side edges E1 and E2 of the inner wall surfaces of the circumferential main grooves 91 and 92.

  The cross-sectional height He is determined as the distance from the groove bottom line BL of the circumferential main groove 91 to the surface of the center land portion 8C as shown in FIG. The groove bottom line BL is a straight virtual line connecting the groove bottoms of the circumferential main grooves 91 on both sides. The cross-sectional heights H1i and H2i correspond to the original groove depths of the circumferential main grooves 91 and 92, respectively, and are set to be equal to each other. Therefore, each of h1, h2, and h3 can be obtained as a cross-sectional height based on the contour line OL.

  The ground contact end CE is the outermost position in the tire axial direction on the ground contact surface. The contact surface refers to the surface of the tread portion 3 that contacts the road surface when a normal load is applied by placing the tire on a normal rim and placing the tire vertically on a flat road surface with normal internal pressure filled. A regular rim is a rim determined for each tire in a standard system including a standard on which a tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, and “Measuring” for ETRTO. Rim ".

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

  Basically, hydroplaning occurs from the center of the tread, which expands outwards and eventually spans the entire tread. Therefore, reducing the flow of water to the center of the tread and increasing the efficiency of draining to the outside of the ground contact surface contribute to the improvement of the hydroplaning prevention performance.

  In the tire T, since the relationship of He> H1i and h1> h2> h3 is satisfied, the contact length becomes longer and the contact pressure becomes higher in the center land portion 8C. Moreover, in order to satisfy | fill the relationship of H1o> H1i and H1o> H2i, in the mediate land part 8M, a contact pressure becomes high in the side close | similar to the center land part 8C (namely, tire width direction inner side). The contact length becomes longer at the mediate land portion 8M after the center land portion 8C. This can reduce the flow of water to the center of the tread that is the starting point for hydroplaning. In addition, in order to satisfy the relationship of H2o ≦ H2i and h1> h2> h3, the shoulder land portion 8S has a shorter ground contact length, and drainage outside the ground contact surface is performed efficiently. As a result, excellent anti-hydroplaning performance is exhibited.

  In the present embodiment, the cross-sectional height H2o is smaller than the cross-sectional height H2i and satisfies the relationship of H2o <H2i, h3> 0. From this, the ground contact length of the shoulder land portion 8S is further shortened, drainage to the outside of the ground contact surface is further promoted, and the hydroplaning prevention performance can be effectively improved.

  As shown in FIG. 3, the surface of the center land portion 8C is formed as an arcuate surface having a vertex at the tire equator CL and protruding outward. Thereby, the flow of water to the center of the tread can be accurately reduced, and the occurrence of hydroplaning can be effectively suppressed. In the present embodiment, the center portion in the width direction of the center land portion 8C is located on the tire equator CL, but these positions may not coincide with each other, and the arc-shaped surface is in the center portion in the width direction of the center land portion 8C. You may have a vertex.

  As shown in FIG. 4, the surface of the mediate land portion 8 </ b> M is formed as an arcuate surface having a vertex at the surface side edge of the outer wall surface of the circumferential main groove 91 and protruding outward. Thereby, the flow of water to the center of the tread can be accurately reduced, and the occurrence of hydroplaning can be effectively suppressed. As shown in FIG. 5, the surface of the shoulder land portion 8S is formed as an arcuate surface having a vertex at the position of the ground contact CE and protruding outward.

  The difference h1 (that is, He-H1i) between the cross-sectional height He and the cross-sectional height H1i is preferably in the range of 0.5 to 2.0 mm. Moreover, the difference h2 (that is, H1o-H2i) between the cross-sectional height H1o and the cross-sectional height H2i is smaller than the difference h1, and is set to, for example, 0.3 to 1.5 mm. A difference h3 (that is, H2i−H2o) between the cross-sectional height H2o and the cross-sectional height H2i is smaller than the difference h2, and is set to 0.2 to 1.0 mm, for example.

  As another embodiment of the present invention, as shown in FIG. 6, it is conceivable to form a chamfer on the surface side edge on at least one of the outer wall surface of the circumferential main groove 91 and the outer wall surface of the circumferential main groove 92. According to this configuration, the edge effect of the mediate land portion 8M and the shoulder land portion 8S can be enhanced, and the steering stability performance can be improved.

  The chamfering is formed by an arc surface having a radius of curvature R of 0.5 to 2.0 mm, for example, but may be formed by an inclined surface instead. In this case, the cross-sectional height H1o is determined on the basis of the intersection of the extension line of the surface of the mediate land portion 8M and the extension line of the outer wall surface of the circumferential main groove 91. Similarly, the cross-sectional height H2o is determined on the basis of the intersection of the extension line of the surface of the shoulder land portion 8S and the extension line of the outer wall surface of the circumferential main groove 92.

  The pneumatic tire of the present invention can be configured in the same manner as a normal pneumatic tire except that the surface of the tread portion is configured as described above, and any conventionally known material, shape, structure, manufacturing method, and the like are included in the present invention. Can be adopted.

  The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention. Therefore, the tread pattern provided in the pneumatic tire of the present invention is not particularly limited as long as the land portion and the circumferential groove described above are provided.

  Examples that specifically show the structure and effects of the present invention will be described below. Each performance evaluation of the tire was performed as follows.

(1) Hydroplaning prevention performance The speed at which hydroplaning occurs when the vehicle travels straight on a road surface having a thin water film was measured. Evaluation is based on an index when the result of Comparative Example 1 is set to 100, and the larger the value, the greater the speed and the better the hydroplaning prevention performance.

(2) Steering stability performance Driving straight and cornering on a dry road surface was evaluated by a driver's sensory test. The result of Comparative Example 1 was evaluated as “4” in seven stages, and the larger the value, the better the steering stability performance.

  The size of the tire used for the evaluation is 205 / 55R16, and the tire structure and the rubber composition in each example are common except for the dimensions of the cross-sectional heights He, H1i, H1o, H2i, and H2o. A 2000 cc front-wheel drive vehicle was used as a test vehicle. The dimensions of the cross-sectional height in each example are shown in Table 1, and the evaluation results are shown in Table 2.

  As shown in Table 1, in Comparative Examples 2 to 4, the hydroplaning prevention performance is relatively low. In Comparative Example 2, h2 is larger than h1, and in Comparative Example 4, since the cross-sectional height H1o is smaller than the cross-sectional height H2i, the flow of water to the center of the tread could not be appropriately reduced. It is done. In Comparative Example 3, it is considered that drainage outside the ground contact surface was not efficiently performed because the cross-sectional height H2o was larger than the cross-sectional height H2i.

  On the other hand, in Examples 1-3, compared with Comparative Examples 1-4, the outstanding hydroplaning prevention performance is exhibited. Among these, in Examples 1 and 2, the effect of maintaining or improving the steering stability performance is also obtained, and h1 is considered to be within a preferable range.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 7 Tread rubber 8C Center land part 8M Mediate land part 8S Shoulder land part 91 1st circumferential main groove 92 2nd circumferential main groove E1 Surface side edge E2 Surface side edge

Claims (5)

On the surface of the tread portion, a center land portion passing through the tire equator, a mediate land portion located on the outer side in the tire width direction of the center land portion, and a shoulder land portion located on the outer side in the tire width direction of the mediate land portion, And a first circumferential main groove that divides the center land portion and the mediate land portion, and a second circumferential main groove that divides the mediate land portion and the shoulder land portion. In the tire,
The cross-sectional height He of the center land portion at the tire equator is larger than the cross-sectional height H1i of the inner wall surface of the first circumferential main groove,
The sectional height H1o of the outer wall surface of the first circumferential main groove is equal to the sectional height H1i of the inner wall surface of the first circumferential main groove and the sectional height of the inner wall surface of the second circumferential main groove. Bigger than H2i,
A sectional height H2o of the outer wall surface of the second circumferential main groove is equal to or smaller than a sectional height H2i of the inner wall surface of the second circumferential main groove;
When the difference between the cross-section height He and the cross-section height H1i is h1, the difference between the cross-section height H1o and the cross-section height H2i is h2, and the difference between the cross-section height H2o and the cross-section height H2i is h3> A pneumatic tire characterized by satisfying a relationship of h2> h3 ≧ 0.   The pneumatic tire according to claim 1, wherein the cross-sectional height H2o is smaller than the cross-sectional height H2i and satisfies a relationship of h3> 0.   The pneumatic according to claim 1 or 2, wherein the surface of the center land portion is formed of an arcuate surface having an apex at a tire equator or a center portion in the width direction of the center land portion and protruding outward. tire.   The pneumatic tire according to any one of claims 1 to 3, wherein a difference h1 between the cross-sectional height He and the cross-sectional height H1i is in a range of 0.5 to 2.0 mm.   The chamfering of the surface side edge is formed in at least one of the outer wall surface of the said 1st circumferential main groove, and the outer wall surface of the said 2nd circumferential main groove. Pneumatic tire.