JP6667281B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  A pneumatic tire is known in which a plurality of main grooves extending in a tire circumferential direction are provided in a tread portion and a land portion is sandwiched between two main grooves. In this pneumatic tire, as described in Patent Literatures 1 to 3, it has been proposed to make the land portion protrude outward in the tire radial direction more than conventional ones. The position of the apex of the protrusion is located at the center side in the tire width direction in Patent Document 1, located inside when the vehicle is mounted in Patent Document 2, and located at the edge of the land in Patent Document 3.

JP 2013-189121 A JP 2005-263180 A JP 2010-12978 A

  By the way, there is a pneumatic tire in which the inclination angle with respect to the normal direction of the reference profile line of the land is different between the side wall on one side and the side wall on the other side of the land sandwiched between the two main grooves. When the pneumatic tire comes in contact with the ground, the contact pressure near the edge of the land where the inclination angle is larger becomes higher than the contact pressure near the other edge, and the contact pressure distribution on the land becomes uneven. It is known. If the distribution of contact pressure on the land becomes uneven, steering stability and rolling resistance will be adversely affected.

  Therefore, the present invention provides a pneumatic tire in which the inclination angle with respect to the normal direction of the reference profile line of the land is different between the side wall surface on one side and the side wall surface on the other side of the land portion, It is an object of the present invention to provide a product in which the non-uniformity is eliminated.

The pneumatic tire of the present embodiment has at least two land portions sandwiched between two main grooves extending in the tire circumferential direction on the tread portion, and in each of the land portions, one side of the land portion In a pneumatic tire having a different inclination angle with respect to a normal direction of a reference profile line of the land portion between a wall surface and the side wall surface on the other side, in each of the land portions, the entire land portion is a reference profile line of the land portion. more projects to the outer side in the tire radial direction, the apex of the projecting, from the center position in the width direction of the land portion, Ri sidewall surface near towards the inclined angle is small, for each of the land portions, whereas the side side The difference between the inclination angle of the wall surface and the inclination angle of the other side wall surface is different, and the larger the difference between the inclination angle of the one side wall surface and the inclination angle of the other side wall surface is, the more the land portion protrudes. Is the distance from the top of Hear, wherein the larger height of the projection.

  In the pneumatic tire of the present embodiment, the land portion having a different inclination angle between the one side wall surface and the other side wall surface projects outward in the tire radial direction from the reference profile line, and the vertex of the protrusion has the smaller inclination angle. , The non-uniformity of the contact pressure distribution is eliminated.

FIG. 2 is a cross-sectional view in the width direction of the pneumatic tire 10 of the embodiment. The width direction sectional view of mediate land part 32. (A) The width direction sectional view of mediate land part 132 of comparative example 1. (B) The width direction sectional view of mediate land part 232 of comparative example 2.

  The pneumatic tire 10 of the present embodiment will be described with reference to the drawings. The drawings may be exaggerated for the sake of explanation.

  The pneumatic tire 10 of the present embodiment shown in FIG. 1 has the same cross-sectional structure as that of the conventional tire except for a tread portion 20. The pneumatic tire 10 has a pair of bead portions on both sides in the tire width direction. The bead portion has a bead core in which rubber is coated on a bundled steel wire, and a bead filler which is a rubber member provided outside the bead core in the tire radial direction. Further, the pneumatic tire 10 includes a carcass ply that forms a skeleton of the tire between a pair of bead portions. The carcass ply is a sheet formed by covering a plurality of ply cords arranged in parallel with rubber. A plurality of belts are stacked outside the carcass ply in the tire radial direction. The belt is formed in a sheet shape by covering a plurality of cords arranged in parallel with rubber. Further, a belt reinforcing layer is provided outside the belt in the tire radial direction, and a rubber tread portion 20 is provided outside the belt reinforcing layer in the tire radial direction. The surface of the tread portion 20 is the ground plane 14. An inner liner is provided inside the tire of the carcass ply. Further, sidewalls 12 are provided on both sides in the tire width direction of the carcass ply. Rubber chafers are provided at positions on both sides of the carcass ply in the tire width direction and outside the bead portions in the tire width direction. The upper part of the rubber chafer is in contact with the lower part of the sidewall 12. The rim touches the surface of the rubber chafer.

  As shown in FIG. 1, the tread portion 20 is provided with four main grooves 21, 22, 23, and 24 extending in the tire circumferential direction. And the center land portion 30 sandwiched between the two main grooves 22 and 23 on the center side in the tire width direction, and the left side sandwiched between the main groove 22 on the center left side in the tire width direction and the main groove 21 on the left side in the tire width direction. Mediate land portion 31, right mediate land portion 32 sandwiched between a main groove 23 on the right side in the tire width direction and a main groove 24 on the right side in the tire width direction, and main grooves 21, 24 on both sides in the tire width direction. Shoulder land portions 33 and 34 which are further outside in the tire width direction are formed. The center land portion 30 and the mediate land portions 31 and 32 are, for example, ribs that are continuous in the tire circumferential direction without being separated by a lateral groove.

  In the mediate land portion 31 on the left side and the mediate land portion 32 on the right side of FIG. 1, one side wall surface and the other side wall surface have an inclination angle (hereinafter simply referred to as “inclination”) with respect to the normal direction of the reference profile line L. Corners) are different. The entire land portion protrudes outward in the tire radial direction from the reference profile line L, and the apex of the protrusion is closer to the side wall surface having the smaller inclination angle.

  First, the mediate land portion 32 on the right side shown in FIG. 2 will be described. The mediate land portion 32 is formed by a left side wall surface 41, a right side wall surface 42, and the ground plane 14. The left side wall surface 41 is also a surface forming the left main groove 23 of the mediate land portion 32, and the right side wall surface 42 is also a surface forming the right main groove 24 of the mediate land portion 32. In the mediate land portion 32, the inclination angle α of the left side wall surface 41 is larger than the inclination angle β of the right side wall surface 42. Here, the inclination angle is an inclination angle of the mediate land portion 32 with respect to the normal direction of the reference profile line L.

  Note that the reference profile line L of the land portion is defined as follows on the cross section in the tire width direction (see FIG. 1). First, in the center land portion 30, which is a land portion having a tire equator, both edges c and d in the width direction of the center land portion 30 and edges b and e of the mediate land portions 31 and 32 facing these are obtained. Of the arc passing through the edges b, c and d and the arc passing through the edges c, d and e, the arc having the larger radius of curvature is defined as the reference profile line L.

  Further, in a land portion located outside the tire equator in the tire width direction (hereinafter referred to as the land portion), both edges of the land portion and the land portion on the tire equator side when viewed from the land portion are referred to as the land portion side. An arc passing through the edge is defined as a reference profile line L. Specifically, in the left side of the mediate land portion 31, both edges a and b in the width direction of the mediate land portion 31 and the edge c of the center land portion 30 on the side of the mediate land portion 31 are obtained. , B, and c are defined as reference profile lines L. In the right side of the mediate land portion 32, both edges e and f in the width direction of the mediate land portion 32 and the edge d of the center land portion 30 on the mediate land portion 32 side are obtained, and the edges d, e, f Is defined as a reference profile line L.

  The entire mediate land portion 32 (except for both edges e and f) protrudes outward from the reference profile line L in the tire radial direction. The portion protruding from the reference profile line L is mountain-shaped. Therefore, there is a protrusion vertex 44 which is the point that protrudes the highest from the reference profile line L in the normal direction.

  The vertex 44 of the protrusion is closer to the right side wall surface 42, which is the side wall surface having a smaller inclination angle, than the center position 46 of the mediate land portion 32 in the width direction. Note that, although different from the embodiment of FIG. 2, when the inclination angle of the left side wall surface 41 is smaller, the apex 44 of the protrusion comes closer to the left side wall surface 41 side.

In the embodiment of FIG. 2, the distance along the reference profile line L between the protrusion vertex 44 and the center position 46 in the width direction of the mediate land portion 32 is X (mm), and the width of the mediate land portion 32 (edge e, The length along the reference profile line L between f) is W (mm), the inclination angle of the left side wall surface 41 is α (degree), the inclination angle of the right side wall surface 42 is β (degree), and the coefficient is t. Then
Equation 1: X = t × (W / 2) × (α−β) / (α + β) (where 0.8 ≦ t ≦ 1.2)
It is desirable that the following relationship be established. According to Equation 1, the distance X increases as the difference between the inclination angle α of the left side wall surface 41 and the inclination angle β of the right side wall surface 42 increases. Note that the coefficient t is set arbitrarily.

When the height of the protrusion vertex 44 (more precisely, the height of the protrusion vertex 44 from the reference profile line L in the normal direction) is Y (mm) and the coefficient is u,
Formula 2: Y = u × 0.5 mm × {1- (β / α)} (where 0.8 ≦ u ≦ 1.2)
It is desirable that the following relationship be established. According to Expression 2, as the inclination angle β of the right side wall surface 42 is smaller than the inclination angle α of the left side wall surface 41, the height Y of the apex 44 of the protrusion increases. Note that the coefficient u is set arbitrarily. For example, when the coefficient u is 1.0, the height Y of the protrusion vertex 44 does not exceed 0.5 mm.

  By the way, when the inclination angles α and β of the left and right side wall surfaces 41 and 42 are slightly different from each other, the mediate land portion 32 may be protruded so that the vertex 44 of the protrusion may be shifted to the side wall surface 42 having the smaller inclination angle. good. Also, only when the difference between the inclination angles α and β of the left and right side wall surfaces 41 and 42 is equal to or greater than a certain value, the mediate land portion 32 protrudes and the protrusion vertex 44 is moved toward the side wall surface 42 having the smaller inclination angle. You may come close. Preferably, when the difference between the inclination angles α and β of the left and right side wall surfaces 41 and 42 is 3 degrees or more, the mediate land portion 32 is protruded, and the protrusion apex 44 is positioned on the side of the side wall surface 42 having the smaller inclination angle. Let me approach.

  Next, the mediate land portion 31 on the left side will be briefly described. The left mediate land portion 31 is also formed by the left side wall surface 51, the right side wall surface 52, and the ground plane 14. The inclination angle of the right side wall surface 52 is larger than the inclination angle of the left side wall surface 51. The definitions of the inclination angle and the reference profile line are as described above. The entire mediate land portion 31 protrudes outward in the tire radial direction from the reference profile line. Is closer to the left side wall surface 51 side. The details are the same as those of the mediate land portion 32 on the right side.

  Here, when the difference between the inclination angles of the right and left side wall surfaces 41 and 42 in the right mediate land portion 32 and the difference between the inclination angles of the left and right side wall surfaces 51 and 52 in the left mediate land portion 31 are different. The distance X and the height Y may be larger in the mediate land portion where the difference between the inclination angles of the left and right side wall surfaces is larger than in the other mediate land portion. For that purpose, for example, in determining the distance X and the height Y in the mediate land portion 31 and the mediate land portion 32, the coefficient t and the coefficient u are the same for the two mediate land portions 31 and 32. Equations 1 and 2 are calculated as values.

  In the center land portion 30, the left side wall surface 54 and the right side wall surface 55 have the same inclination angle. The land portion having no difference in the inclination angle between the left and right side walls may or may not protrude outward in the tire radial direction from the reference profile line.

  As described above, since the inclination angles of the right side wall surface and the left side wall surface of the mediate land portions 31 and 32 are different from each other, the ground pressure near the edge portion on the side wall surface side where the inclination angle is small becomes intact. The contact pressure becomes lower than the contact pressure near the edge portion on the side wall surface side where the corner is large, and the contact pressure distribution becomes non-uniform. However, in the pneumatic tire 10 of the present embodiment, the mediate land portions 31 and 32 project outward in the tire radial direction from the reference profile line, and the apex of the projection is on the side of the side wall surface having the smaller inclination angle. As a result, the contact pressure near the edge portion on the side wall surface side where the inclination angle is small is high. As a result, in the mediate land portions 31 and 32, the contact pressure near both edges in the width direction is balanced, and the uneven contact pressure distribution is eliminated.

  Here, as the difference between the inclination angles of the left and right side walls is larger, the nonuniformity of the contact pressure distribution becomes larger in the mediate land portion in which the reference profile line L does not protrude outward in the tire radial direction. However, the mediate land portions 31 and 32 protrude outward in the tire radial direction from the reference profile line L, and the distance X between the top of the protrusion and the center position of the mediate land portions 31 and 32 in the width direction is calculated according to the above equation (1). If the length is increased according to the difference between the inclination angles of the left and right side walls, the unevenness of the ground pressure distribution caused by the difference between the inclination angles of the left and right side walls is successfully solved.

  If the height Y of the peak of the protrusion is increased in accordance with the difference between the inclination angles of the left and right side walls according to the above equation 2, the ground pressure distribution resulting from the difference between the inclination angles of the left and right side walls is not correct. Uniformity is successfully resolved. In addition, if the height Y of the protruding apex is about 0.5 mm at the maximum according to the above equation 2, the height Y of the protruding apex may be too high, which may cause unevenness of the contact pressure distribution. Can be prevented.

  When the difference between the inclination angles of the left and right side walls is 3 degrees or more, the non-uniformity of the contact pressure distribution of the mediate land portions 31 and 32 is likely to occur as it is, so that the mediate land portions 31 and 32 are not formed. The effect of projecting outward in the tire radial direction from the reference profile line L and having the apex of the projection on the side of the side wall surface having the smaller inclination angle is significant.

  Various changes, substitutions, omissions, and the like can be made to the present embodiment without departing from the spirit of the invention. For example, the number of main grooves is not limited to four, and may be any number as long as it is plural. Therefore, the number of land portions sandwiched between the two main grooves is not limited to three. Also, in any land portion sandwiched between the two main grooves, if the inclination angle is different between the side wall surface on one side and the side wall surface on the other side, the mediate land portions 31 and 32 in the above embodiment are different from each other. It can be similarly protruded. In the case of projecting a plurality of land portions, the larger the difference in inclination angle between the side wall surface on one side and the other side wall surface, the greater the distance between the top of the protrusion and the center position of the land portion in the width direction, and The height may be increased.

  The steering stability and rolling resistance of the pneumatic tires of Comparative Examples and Examples shown in Table 1 were evaluated. In each of the pneumatic tires, there was a difference in the inclination angles of the left and right side walls of the mediate land portion. The inclination of the left side wall was 15 degrees, and the inclination of the right side wall was 8 degrees. Each of the mediate land portions had a width of 22 mm. In each of the mediate land portions, the whole protruded outward in the tire radial direction from the reference profile line, and there was an apex of the protrusion.

  In the pneumatic tire of Comparative Example 1 shown in FIG. 3A, the position of the protrusion apex 144 is the center position in the width direction of the mediate land portion 132, and the height of the protrusion apex 144 is the inclination of the left and right side wall surfaces. It was a fixed value of 5 mm or less irrespective of the angle difference. In the pneumatic tire of Comparative Example 2, the position of the protrusion apex 244 in the mediate land portion 232 is the edge of the side wall surface side with a small inclination angle, and the height of the protrusion apex 244 is the height of the inclination angle of the left and right side wall surfaces. It was a fixed value of 5 mm or less irrespective of the difference. In the pneumatic tire of Example 1, the position of the peak of the protrusion was the position according to the above formula 1, and the height of the peak of the protrusion was the height according to the above formula 2.

  In the evaluation, the pneumatic tire was set at an appropriate air pressure and mounted on an appropriate rim. Here, the appropriate air pressure and the appropriate rim are the internal pressure and the standard rim specified in the standards such as JATMA, TRA, and ETRTO. Regarding the driving stability, the pneumatic tire was assembled to the vehicle, and the driver drove and evaluated the feeling. Then, the evaluation results were indexed. The larger the index, the better the steering stability. Regarding the rolling resistance, a rolling resistance coefficient was measured using a rolling resistance tester. And the result was indexed. The smaller the index is, the better the rolling resistance is.

  Table 1 shows the results. In Example 1 included in the above embodiment, both the steering stability and the rolling resistance were better than Comparative Example 1. This is because the pneumatic tire of Comparative Example 1 has non-uniformity in the contact pressure distribution of the mediate land portion 132, whereas the pneumatic tire of Example 1 has eliminated the non-uniformity of the contact pressure distribution. It is considered to be. On the other hand, in Comparative Example 2, both the steering stability and the rolling resistance were worse than Comparative Example 1. One of the causes is considered to be that the difference in the contact length in the tire circumferential direction between the left and right edges of the mediate land portion 232 has increased.

L: Reference profile line 10: Pneumatic tire, 12: Side wall, 14: Ground contact surface, 20: Tread portion, 21, 22, 23, 24: Main groove, 30: Center land portion, 31, 32: Mediate land Part, 33, 34 ... shoulder land part, 41, 42 ... side wall surface, 44 ... vertex, 46 ... center position, 51, 52, 54, 55 ... side wall surface, 132 ... mediate land part, 144 ... vertex, 232 ... Mediate Land, 244 ... top

Claims (3)

The tread portion has at least two land portions sandwiched between two main grooves extending in the tire circumferential direction. In each of the land portions, one side wall surface and the other side wall surface of the land portion are provided. In a pneumatic tire having a different inclination angle with respect to a normal direction of the land portion reference profile line,
In each of the land portions, the entire land portion protrudes outward in the tire radial direction from the reference profile line of the land portion, and a vertex of the protrusion has a smaller inclination angle than a center position in the width direction of the land portion. rectangular side wall surface near of is,
For each land portion, a difference between the inclination angle of the one side wall surface and the inclination angle of the other side wall surface is different,
The larger the difference between the inclination angle of the one side wall surface and the inclination angle of the other side wall surface is, the larger the distance from the top of the protrusion to the center of the land portion in the width direction and the height of the protrusion is larger. ,
Pneumatic tire. The distance between the apex of the protrusion and the center of the land portion in the width direction is X (mm), the width of the land portion is W (mm), and the inclination angle of the side wall surface having the larger inclination angle is α ( Degree), the inclination angle of the side wall surface having the smaller inclination angle is β (degree), and the coefficient is t.
X = t × (W / 2) × (α−β) / (α + β) (0.8 ≦ t ≦ 1.2)
The pneumatic tire according to claim 1, wherein: The height of the apex of the protrusion from the reference profile line of the land portion is Y (mm), the inclination angle of the side wall surface with the larger inclination angle is α (degree), and the side wall surface with the smaller inclination angle is α. Is β (degrees) and the coefficient is u,
Y = u × 0.5 mm × {1- (β / α)} (0.8 ≦ u ≦ 1.2)
The pneumatic tire according to claim 1, wherein the following holds.

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