JP5521755B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can suppress uneven wear of a shoulder portion due to a road surface cant.

  For example, roads in North America are provided with a road surface cant having an inclination of about 1.5 [deg] to 2 [deg] from the center of the road toward both roads in order to improve drainage of the road surface. When the vehicle travels on such a road, there is a problem that uneven wear occurs in the shoulder portion of the tread portion of the pneumatic tire.

  In the United States and the like where the vehicle runs on the right side of the road, the road surface cant is inclined so as to descend from the left side to the right side with respect to the traveling direction of the vehicle. In such a case, the left and right pneumatic tires mounted on the front axle of the vehicle go straight against the road surface cant, and are therefore inclined to the upper side (mountain side) of the road surface cant by operating the vehicle handle. A slip angle is given in the direction. On the other hand, the ground contact surface of the pneumatic tire is elastically deformed in a downward direction of inclination, and a force (lateral force) to the road surface cant lower side (valley side) is generated. For this reason, polygonal wear occurs in which the shoulder portions on the lower side of the road surface can be worn unevenly in the left and right pneumatic tires. When uneven wear occurs in the shoulder portion in this way, the lateral force toward the lower side of the road surface cant increases, and a slip angle is further imparted in order to go straight on the road surface against the lateral force. This repetition is considered to increase the wear rate and shorten the life of the pneumatic tire. As a result, the pneumatic tire is replaced despite having sufficient grooves.

  In the problem caused by the road surface cant, in the conventional pneumatic tire, a narrow groove extending along the tire circumferential direction is formed on the non-contact surface of the shoulder rib on the lower side of the road surface cant. Some attempt to suppress uneven wear of ribs (see, for example, Patent Document 1). In addition, in the conventional pneumatic tire, the main groove extending in the tire circumferential direction is formed so as to incline toward the upper side of the road surface toward the traveling direction of the vehicle, thereby canceling the lateral force and reducing the shoulder rib. Some attempt to suppress uneven wear (for example, see Patent Document 2).

JP 2006-8022 A JP 2006-137244 A

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can suppress the uneven wear of the shoulder rib by a road surface cant.

  In order to solve the above-described problems and achieve the object, a pneumatic tire according to the present invention includes a pair of left and right bead cores, a bead filler disposed on the outer side in the tire radial direction of the bead core, and a pair of left and right bead cores. A carcass disposed; a belt layer disposed on the outer side in the tire radial direction of the carcass; and a tread portion including at least two circumferential main grooves provided along the tire circumferential direction. The length of the carcass periphery from the intersection of the tire equator line and the carcass to the intersection of the upper surface of the bead core on one side of the tire equator line and the carcass on the inner circumferential side of the tire in the meridian section of the tire is Pa From the intersection of the tire equator line and the carcass to the intersection of the extension line on the upper surface of the bead core on the other side of the tire equator line and the carcass on the tire inner circumference side Characterized in that it is a Pa <Pb when the carcass peri ferri length was Pb.

  According to this pneumatic tire, the outermost shoulder rib in the tire width direction on one side of the tire equator line suppresses the occurrence of polygonal wear that wears unevenly and travels at the wear rate of polygonal wear. Can be delayed with respect to distance. Thereby, the partial wear of the shoulder rib by a road surface cant can be suppressed. The reason for this is that when the internal pressure is applied by making the carcass peripheral length Pa on one side bordered by the tire equator line smaller than the carcass peripheral length Pb on the other side bordered by the tire equator line, The carcass tension can be made larger on one side of the equator line than on the other side of the tire equator line. In this way, by producing a difference in tension, when traveling straight on a road surface having a road surface cant, a force toward the other side of the tire equator line is generated on the tread surface that contacts the road surface so as to increase the inclination. This is because the lateral force that is elastically deformed is suppressed when going to one side of the tire equator line as a boundary so as to go down the slope.

  As described above, the pneumatic tire of the present invention has a carcass peripheral length Pb on one side bordered on the tire equator line and a carcass peripheral length Pb on the other side bordered on the tire equator line in the tire meridional section. However, it is desirable to adopt the following mode. That is, in the pneumatic tire of the present invention, the carcass is a tire meridian cross-sectional view, the carcass radius from the shoulder portion to the tire maximum width position on one side of the tire equator line is RUa, the tire equator line RUa> RUb when the carcass radius is RUb from the shoulder portion to the tire maximum width position on the other side of the tire, and the tire on the one side bordered by the tire equator line in the tire meridional section view RLa> RLb, where RLa is the carcass radius from the maximum width position to the highest position of the hard bead filler, and RLb is the carcass radius from the tire maximum width position to the highest position of the hard bead filler on the other side of the tire equator line. It can be.

  According to this pneumatic tire, the shoulder ribs due to the road surface cant are made relatively small by reducing the carcass radius on one side of the tire equator line from the shoulder part to the tire bead part through the maximum position of the tire. The uneven wear can be suppressed.

  In the pneumatic tire of the present invention, the tread portion is on the tire equator line side by 20% of the half width TW of the tread deployment width from the shoulder end on one side of the tire equator line as viewed from the tire meridian cross section. At the position of, the tread rubber gauge from the tread tread to the outermost layer of the belt is La, and the tire equator is 20% of the half width TW of the tread deployment width from the shoulder end on the other side of the tire equator line. When the tread rubber gauge from the tread tread surface to the belt outermost layer at the position on the line side is Lb, it is desirable that La> Lb. According to this pneumatic tire, in the tire tread portion, the tire rigidity on the same side is increased by relatively increasing the tread rubber gauge on one side of the tire equator line, and the shoulder rib by the road surface cant The uneven wear can be further suppressed.

  In the pneumatic tire of the present invention, the tread portion is a tread rubber from the shoulder side circumferential main groove bottom to the belt outermost layer on one side of the tire equator line in the tire meridional section view. It is desirable that Ua> Ub, where Ua is the gauge and Ub is the tread rubber gauge from the shoulder-side circumferential main groove bottom to the belt outermost layer on the other side of the tire equator line. According to this pneumatic tire, in the tire tread portion, the tire rigidity on the same side is increased by relatively increasing the tread rubber gauge on one side of the tire equator line, and the shoulder rib by the road surface cant The uneven wear can be further suppressed.

  Further, in the pneumatic tire of the present invention, the belt layer has at least two belts adjacent to each other with cords intersecting in a tire meridional cross-sectional view, and the tire inner circumferential side of at least two belts. The belt width from the tire equator line to the belt end on one side bordered by the tire equator line is BLa, and the belt from the tire equator line to the belt end on the other side bordered by the tire equator line When the width is BLb, BLa> BLb, and of the at least two belts, the belt on the tire outer peripheral side is a belt extending from the tire equator line to the belt end portion on one side of the tire equator line. It is desirable that BUa> BUb when the width is BUa and the belt width from the tire equator line to the belt end on the other side of the tire equator line is BUb. According to this pneumatic tire, for each of a plurality of intersecting belts, the belt width from the tire equator line to the belt end is relatively increased on one side of the tire equator line, so that the same side The tire rigidity in the tire can be increased, and uneven wear of the shoulder ribs due to the road surface cant can be further suppressed.

  Further, in the pneumatic tire of the present invention, in the tire meridian cross-sectional view, from one side of the tire equator line to the carcass from the shoulder end to the carcass, from the carcass outer surface to the maximum width belt inner surface Ta> Tb, where Ta is the rubber gauge, and Tb is the rubber gauge from the outer surface of the carcass to the inner surface of the maximum width belt when the perpendicular from the shoulder end to the carcass is lowered from the tire equator line. Is desirable. According to this pneumatic tire, by increasing the rubber gauge on one side of the tire equator line in the vicinity of the shoulder, the tire rigidity on the same side is increased, and the shoulder rib is biased by the road surface cant. Wear can be further suppressed.

  Further, in the pneumatic tire of the present invention, in the tire meridional section view, the rubber gauge from the carcass outer surface to the sidewall surface at the tire maximum width position on one side of the tire equator line is Sa, the tire equator When the rubber gauge from the outer surface of the carcass at the tire maximum width position on the other side of the line to the sidewall surface is Sb, Sa> Sb is desirable. According to this pneumatic tire, by increasing the rubber gauge on one side of the tire equator line in the vicinity of the maximum tire width position, the tire rigidity on the same side is increased, and the shoulder rib by the road surface cant The uneven wear can be further suppressed.

  Further, in the pneumatic tire of the present invention, the bead filler is a carcass of a carcass along a perpendicular extending from the carcass winding height position to the carcass main body on one side of the tire equator line in a tire meridian cross-sectional view. The bead filler gauge from the hoisting height position to the carcass body is BFa, and the carcass hoisting height position from the carcass hoisting position along the vertical line extending from the carcass hoisting height position to the carcass body on the other side of the tire equator line When the bead filler gauge to the main body is BFb, it is desirable that BFa> BFb. According to this pneumatic tire, the bead filler size on one side of the tire equator line is made relatively large, so that the tire rigidity on the same side is increased and the uneven wear of the shoulder ribs due to the road surface cant is further suppressed. can do.

  Furthermore, the pneumatic tire of the present invention can have a symmetrical profile on the left and right with respect to the tire equator line in a tire meridian cross-sectional view. According to such a means, not only can the entire outer shape of the tire be aesthetically pleasing, but there is no need to provide a dedicated mold when manufacturing the tire, so that the tire can be manufactured inexpensively and easily. it can.

  In addition, the pneumatic tire of the present invention is preferably applied to a heavy duty pneumatic tire. The heavy-duty pneumatic tire is used for trucks and buses that run on a road surface provided with a road surface cant for a long time at high speeds, and therefore, uneven wear of shoulder ribs due to the road surface cant tends to occur. For this reason, there exists an advantage by which the uneven wear suppression effect of the shoulder rib by a road surface cant is acquired more notably by making a heavy-duty pneumatic tire applicable.

  Moreover, it is preferable that the pneumatic tires of the present invention are mounted in pairs on the left and right of the vehicle steering axis. By mounting in pairs on the left and right of the vehicle's steer shaft, the force toward the upper side of the road surface cant is generated in a pair of left and right sides, so there is an advantage that the effect of suppressing uneven wear of the shoulder ribs by the road surface cant can be obtained more remarkably. is there.

  The pneumatic tire according to the present invention can suppress uneven wear of the shoulder rib due to the road surface cant.

FIG. 1 is a meridional sectional view of a pneumatic tire according to this embodiment. FIG. 2 is a schematic view of the pneumatic tire according to this embodiment mounted on a vehicle. FIG. 3 is a meridional sectional view of the pneumatic tire according to the present embodiment. FIG. 4 is a meridian enlarged cross-sectional view of the pneumatic tire according to the present embodiment. FIG. 5 is a meridian enlarged cross-sectional view of the pneumatic tire according to the present embodiment. FIG. 6 is a meridian enlarged cross-sectional view of the pneumatic tire according to the present embodiment. FIG. 7 is a meridian enlarged cross-sectional view of the pneumatic tire according to the present embodiment. FIG. 8 is a meridional sectional view of the pneumatic tire according to the present embodiment.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following description. In addition, constituent elements in the following description include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. Moreover, the structure disclosed below can be combined suitably.

  FIG. 1 is a meridional sectional view of a pneumatic tire 1 according to this embodiment. In the following description, the tire radial direction refers to a direction orthogonal to the rotational axis of the pneumatic tire 1, the tire radial inner side refers to the side toward the rotational axis in the tire radial direction, and the tire radial outer side refers to the tire diameter. The side away from the rotation axis in the direction. The tire width direction means a direction parallel to the rotation axis, the inner side in the tire width direction means the side toward the tire equator plane (tire equator line) C in the tire width direction, and the outer side in the tire width direction means the tire width. The side away from the tire equatorial plane C in the direction. The tire circumferential direction is a circumferential direction with the rotation axis as a central axis. The tire equatorial plane C is a plane that is orthogonal to the rotation axis of the pneumatic tire 1 and passes through the center of the tire width of the pneumatic tire 1. The tire equator line is a line on the tire equator plane C and along the circumferential direction of the pneumatic tire 1. In the present embodiment, the same sign “C” as that of the tire equator plane is attached to the tire equator line.

  As shown in FIG. 1, the pneumatic tire 1 according to the present embodiment includes a tread portion 2, sidewall portions 3 on both sides thereof, and bead portions 4. Further, the pneumatic tire 1 has a carcass 5 and a belt layer 6. When the pneumatic tire 1 shown in FIG. 1 is attached to the tire, the right side in the figure in the tire width direction is one side (the road surface cant lower side (valley side)) with the tire equator line as a boundary. The left side in the figure is the other side (road surface cant upper side (mountain side)) with the tire equator line as a boundary. Here, the lower side of the road surface cant is a direction in which the height in the vertical direction decreases in the direction orthogonal to the traveling direction of the vehicle. Further, the upper side of the road surface cant is a direction in which the height in the vertical direction increases in the direction orthogonal to the traveling direction of the vehicle. That is, the pneumatic tire 1 is mounted on a vehicle that runs on a road surface that is inclined so that the height in the vertical direction decreases from the upper side of the road surface toward the lower side of the cant.

  The tread portion 2 has a plurality of circumferential main grooves 22 extending in the tire circumferential direction on the outer circumferential surface thereof, that is, a tread surface 21 that comes into contact with the road surface during traveling, and a plurality of sections formed by the circumferential main grooves 22. And a rib 23 forming a land portion. For example, in this embodiment, four circumferential main grooves 22 are formed, and five ribs 23 are formed by these circumferential main grooves 22. The outermost ribs 23 in the tire width direction form shoulder ribs 23a.

  The sidewall portion 3 is exposed to both outer sides in the tire width direction of the pneumatic tire 1 continuously with the tread portion 2. The side wall part 3 prevents trauma generated in the side wall part 3 from reaching the carcass 5.

  The bead portion 4 includes a bead core 41 and a bead filler 42. The bead core 41 is formed by winding a bead wire, which is a steel wire, in a ring shape. The bead core 41 supports the tension of the carcass 5 generated by the internal pressure of the pneumatic tire 1. The bead filler 42 includes a hard bead filler 42a and a soft bead filler 42b, and is disposed in a space formed by folding the carcass 5 outward in the tire width direction at the position of the bead core 41. The bead filler 42 fixes the carcass 5 at the position of the bead core 41 and adjusts the shape of the bead portion 4. Further, the bead filler 42 increases the rigidity of the bead portion 4.

  The carcass 5 continuously straddles the tread portion 2, both sidewall portions 3, and both bead portions 4, and both side ends in the tire width direction are rewound around the pair of bead portions 4, and the toroid is formed in the tire circumferential direction. It is wound around in a shape to form a tire skeleton. The carcass 5 is a carcass cord such as organic fiber (nylon, polyester, rayon, etc.) or steel covered with a rubber material. A plurality of carcass cords of the carcass 5 are arranged in parallel in the tire circumferential direction while being orthogonal to the tire equator line C of the pneumatic tire 1 and along the tire meridian direction (radial direction). The angle of the carcass cord with respect to the tire equator line C (tire circumferential direction) in the carcass 5 is substantially 90 [°], and from −5 [°] with respect to 90 [°] with respect to the tire equator line C. Includes angles in the range of +5 [°]. The carcass 5 serves as a pressure vessel when the pneumatic tire 1 is filled with air and supports a load applied to the pneumatic tire 1 by the internal pressure.

  The carcass 5 has a shape in which the shape on the lower side of the road surface cant and the shape on the upper side of the road surface cant are different, that is, an asymmetrical shape, when the tire equator line C is a symmetric axis in the tire meridian cross-sectional view. Here, in each of the left and right sides of the tire equator line C, the length from the intersection point X of the carcass 5 to the tire equator line C to the intersection point Ya of the upper surface of one of the bead cores 41 of the carcass 5 is expressed as carcass peri. The length from the intersection X with the tire equator line C of the carcass 5 to the intersection Yb with the extension line of the upper surface of the other bead core 41 of the carcass 5 is defined as a carcass peripheral length Pb. Here, one bead core 41 and the intersection point Ya are arranged below the road surface cant from the other bead core 41 and the intersection point Yb. Therefore, the carcass peripheral length Pa is the carcass peripheral length below the road surface cant. Further, the other bead core 41 and the intersection point Yb are arranged on the road surface cant upper side than the one bead core 41 and the intersection point Ya. Therefore, the carcass peripheral length Pb is the carcass peripheral length on the upper side of the road surface cant. In the carcass 5, the relationship between the carcass peripheral length Pa and the carcass peripheral length Pb is Pa <Pb.

  The belt layer 6 is provided outside the carcass 5 in the tire radial direction in the tread portion 2, and covers the carcass 5 in the tire circumferential direction in the tread portion 2. The belt layer 6 has a belt in which a cord such as organic fiber (nylon, polyester, rayon, etc.) or steel is covered with a rubber material, and a plurality of these belts are laminated. In the present embodiment, a four-layer structure in which belts 61, 62, 63, and 64 are laminated is formed. Further, the belts 61 to 64 are arranged with a predetermined angle with respect to the tire circumferential direction, that is, the tire equator line C. The belt layer 6 gives a tightening force to the carcass 5 to increase the rigidity, and at the time of traveling of the vehicle on which the pneumatic tire 1 is mounted, the impact is reduced and trauma generated in the tread portion 2 reaches the carcass 5. To prevent that.

  FIG. 2 is a schematic view of the pneumatic tire according to this embodiment mounted on a vehicle. The pneumatic tire 1 is mounted on each of the left and right sides of the vehicle steering axis S and travels straight on a road surface having a road surface cant. The road surface cant is generally an inclination of about 1.5 [deg] to 2 [deg] formed from the center of the road toward both roads in order to improve the drainage of the road surface R. This road surface cant, for example, on an American road on which the vehicle runs on the right side, has an inclination in which the road surface R descends from the left side to the right side as shown in FIG.

  Here, as described above, in both the wheels, the tire 1 has a carcass peripheral length Pa that is lower than the carcass peripheral length Pa and a carcass peripheral length Pb that is higher than the cant. It is installed. Thereby, in the pneumatic tire 1, the carcass peripheral length Pa on the lower side of the cant is shorter than the carcass peripheral length Pb on the upper side of the cant. With the above-described configuration, the pneumatic tire 1 suppresses occurrence of polygonal wear in which the outermost shoulder rib 23a in the tire width direction on the lower side of the road surface cant is worn unevenly, and the wear speed of the polygonal wear is determined by the travel distance. Therefore, uneven wear of the shoulder rib 23a due to the road surface cant can be suppressed.

  The reason for this is that the tire 1 has a carcass periphery length of Pa <Pb, so that when it comes in contact with the road surface in the state of being mounted on the vehicle, This is because a force F that pushes the tire 1 in the direction from the lower side of the road surface cant to the upper side of the road surface cant can be generated. More specifically, by setting each carcass peripheral length to Pa <Pb, when an internal pressure is applied, the carcass tension TL acting on the lower portion of the road surface cant of the tire is a portion on the upper side of the road surface cant of the tire. It becomes larger than the carcass tension TU acting on the. That is, the relationship between the tension TL and the tension TU is TU <TL. Thus, by generating a difference in the carcass tension acting on the tire between the upper side of the road surface cant and the lower side of the road surface cant, the force F is generated, and uneven wear can be suppressed as described above.

  Here, in the pneumatic tire, the carcass preferably has a shape in which the carcass peripheral length Pa and the carcass peripheral length Pb satisfy 0.90 ≦ Pa / Pb <0.98. By setting the ratio Pa / Pb of the carcass periphery length Pa and the carcass periphery length Pb to 0.90 or more, a good tire shape can be ensured. By setting the ratio Pa / Pb to less than 0.98, the force F generated on the tire can be a certain level or more. This is because by setting the ratio Pa / Pb to be less than 0.98, the difference between the carcass tension acting on the upper portion of the road surface cant of the tire and the carcass tension acting on the lower portion of the road surface cant of the tire is constant. This is thought to be due to the above. From the above, the pneumatic tire can suppress uneven wear more appropriately by setting 0.90 ≦ Pa / Pb <0.98.

  Next, a more preferable shape of the pneumatic tire will be described with reference to FIG. Here, FIG. 3 is a meridional sectional view of the pneumatic tire according to the present embodiment. The carcass 5 of the pneumatic tire shown in FIG. 3 includes a carcass radius (curvature radius) RUa from a predetermined position TSa of the shoulder portion to the tire maximum width position Ma, and a carcass from a predetermined position TSb of the shoulder portion to the tire maximum width position Mb. The relationship with radius (radius of curvature) RUb is RUa> RUb. In the pneumatic tire, the predetermined position TSa, the maximum tire width position Ma, and the carcass radius RUa are the parts below the road surface cant, and the predetermined position TSb, the maximum tire width position Mb, and the carcass radius RUb are the parts above the road surface cant. It becomes.

  The carcass is a relationship between the carcass radius RLa from the tire maximum width position Ma to the highest position BFUa of one hard bead filler 42a and the carcass radius RLb from the tire maximum width position Mb to the highest position BFUb of the other hard bead filler 42a. Becomes RLa> RLb. In the same manner as described above, one hard bead filler 42a, highest position BFUa, and carcass radius RLa are the parts below the road surface cant, and the other hard bead filler 42b, highest position BFUb, and carcass radius RLb are the parts above the road surface cant. .

  When the pneumatic tire has a shape in which each carcass radius of the carcass satisfies the above relationship, uneven wear of the shoulder ribs 23a due to the road surface cant can be more appropriately suppressed. The pneumatic tire preferably has a shape that satisfies both RUa> RUb and RLa> RLb, but may have a shape that satisfies only one of RUa> RUb and RLa> RLb.

  The relationship between the carcass radius RUa and the carcass radius RUb preferably satisfies 1.0 <RUa / RUb ≦ 1.5. The relationship between the carcass radius RLa and the carcass radius RLb is preferably 1.0 <RLa / RLb ≦ 1.5. By setting 1.0 <RUa / RUb or 1.0 <RLa / RLb, the magnitude of the force toward the upper side of the road surface cant can be increased to a certain level so as to increase the slope, and RUa / RUb ≦ 1. 5 or RLa / RLb ≦ 1.5 can ensure a good tire shape.

  Next, another example of a more preferable shape of the pneumatic tire will be described with reference to FIG. FIG. 4 is a meridian enlarged cross-sectional view of the pneumatic tire according to the present embodiment. The tread portion of the pneumatic tire shown in FIG. 4 is a belt whose vertical line is lowered from the tread tread surface 21 at a position on the tire equator line C side by 20% of the half width TW of the tread development width from the shoulder end portion below the road surface cant. The tread rubber gauge (tread thickness) La up to the outermost layer and the vertical line from the tread tread 21 at the position on the tire equator line C side by 20% of the half width TW of the tread deployed width from the shoulder end on the road surface cant. The relationship with the tread rubber gauge (tread thickness) Lb up to the outermost layer of the belt is La> Lb. Since the rigidity of the shoulder rib on the lower side of the road surface cant in the tread portion can be made higher than the rigidity of the shoulder rib on the upper side of the road surface cant, uneven wear of the shoulder rib 23a due to the road surface cant can be further suppressed.

  The relationship between the tread rubber gauge La and the tread rubber gauge Lb is preferably 1.0 <La / Lb ≦ 1.3. By setting the tread rubber gauge ratio La / Lb in the vicinity of the shoulder end of the road surface cant lower side and the road surface cant upper side to be more than 1.0, the rigidity of the shoulder rib on the road surface cant lower side of the shoulder rib on the road surface cant upper side is increased. By setting the ratio La / Lb to 1.3 or less while sufficiently increasing the rigidity, it is possible to secure a good tire shape and to obtain an appropriate rigidity difference.

  Next, another example of a more preferable shape of the pneumatic tire will be described with reference to FIG. FIG. 5 is a meridian enlarged cross-sectional view of the pneumatic tire according to the present embodiment. The pneumatic tire shown in FIG. 5 includes a tread rubber gauge (tread thickness) Ua from the bottom of the circumferential main groove 22a on the shoulder side to the outermost layer of the belt on the lower side of the road surface cant, and a shoulder side on the upper side of the road surface cant. The relationship with the tread rubber gauge (tread thickness) Ub from the bottom of the circumferential main groove 22a to the outermost layer of the belt is Ua> Ub. By setting the shape of the tread portion to the above shape, the rigidity of the shoulder portion on the lower side of the road surface cant can be increased, and uneven wear of the shoulder rib 23a due to the road surface cant can be further suppressed.

  The relationship between the tread rubber gauge Ua and the tread rubber gauge Ub is preferably 1.0 <Ua / Ub ≦ 1.5. By setting the tread rubber gauge ratio Ua / Ub below the circumferential main groove 22a on the shoulder side for the lower side of the road surface cant and the upper side of the road surface cant to be more than 1.0, the rigidity of the shoulder portion on the lower side of the road surface cant is increased. By making the ratio Ua / Ub 1.5 or less while sufficiently increasing the rigidity of the upper shoulder portion, it is possible to secure a good tire shape and to make an appropriate rigidity difference.

  Next, another example of a more preferable shape of the pneumatic tire will be described with reference to FIG. FIG. 6 is a meridian enlarged cross-sectional view of the pneumatic tire according to the present embodiment. The pneumatic tire shown in FIG. 6 has at least two belts with cords crossing adjacent to each other, in the figure, belts 62, 63 of the four belts 61, 62, 63, 64 constituting the belt layer 6. For each of these, the belt width from the tire equator line C to the belt end is different on the left and right with respect to the tire equator line C.

  Specifically, for the belt 62 on the tire inner peripheral side, BLa> BLb is satisfied when the belt width on the lower side of the road surface cant is BLa, and the belt width on the upper side of the road surface cant is BLb, and the belt 63 on the outer peripheral side of the tire. As for BU, the belt width below the road surface cant is BUa, and the belt width above the road surface cant is BUb, so that BUa> BUb. According to this embodiment, an asymmetric belt layer shape can be obtained with the tire equator line C as a boundary, and as a result, the rigidity of the shoulder part on the lower side of the road surface cant can be made higher than the rigidity of the shoulder part on the upper side of the road surface cant. It is possible to further suppress uneven wear of the shoulder rib 23a due to the road surface cant.

  In the example shown in FIG. 6, belts 62 and 63 are adjacent belts where the cords cross each other, but the belt is not limited to these, for example, a combination of belts 61 and 62 or a combination of belts 63 and 64. You can also. Further, when the total number of belt layers is 2, 3, or 5 or more, any belt combination can be selected as long as it is at least two belts adjacent to each other with cords intersecting.

  The relationship between the belt width BLa and the belt width BLb is preferably 1.1 <BLa / BLb ≦ 1.5. The relationship between the belt width BUa and the belt width BUb is preferably 1.0 <BUa / BUb ≦ 1.5. By making the ratio BLa / BLb and ratio BUa / BUb of the belt width below the road surface cant and the belt width above the road surface cant exceed 1.1, the rigidity of the shoulder portion below the road surface cant is increased to the shoulder above the road surface cant This can be sufficiently higher than the rigidity of the part. Further, by setting the ratios BLa / BLb and BUa / BUb to 1.5 or less, it is possible to ensure appropriate belt rigidity.

  Next, another example of a more preferable shape of the pneumatic tire will be described with reference to FIG. FIG. 7 is a meridian enlarged cross-sectional view of the pneumatic tire according to the present embodiment. In this embodiment, as shown in the figure, the rubber gauge from the outer surface of the carcass to the inner surface of the maximum width belt 62 when the perpendicular is lowered from the shoulder end portion to the carcass is different on the left and right with respect to the tire equator line C.

  Specifically, Ta> Tb when the rubber gauge below the road surface cant is Ta and the rubber gauge above the road surface cant is Tb. By making Ta> Tb the relationship between the rubber gauge Ta and the rubber gauge Tb, the rigidity of the shoulder part on the lower side of the road surface cant can be made higher than the rigidity of the shoulder part on the upper side of the road surface cant. Wear can be further suppressed.

  The relationship between the rubber gauge Ta and the rubber gauge Tb is preferably 1.0 <Ta / Tb ≦ 1.5. By setting the rubber gauge ratio Ta / Tb near the end of the maximum width belt for the lower side of the road surface cant and the upper side of the road surface cant to be more than 1.0, the rigidity of the shoulder portion on the lower side of the road surface cant This can be sufficiently higher than the rigidity. In addition, by setting the ratio Ta / Tb to 1.5 or less, it is possible to secure a good tire shape and obtain an appropriate rigidity difference.

  Next, another example of a more preferable shape of the pneumatic tire will be described with reference to FIG. FIG. 8 is a meridional sectional view of the pneumatic tire according to the present embodiment. In the pneumatic tire shown in FIG. 8, the rubber gauge from the outer surface of the carcass to the surface of the sidewall portion at the tire maximum width position is different on the left and right with respect to the tire equator line C.

  Specifically, Sa> Sb, where Sa is the rubber gauge at the tire maximum width position below the road surface cant and Sb is the rubber gauge at the tire maximum width position above the road surface cant. Thereby, since the rigidity of the shoulder part below a road surface cant can be made higher than the rigidity of the shoulder part above a road surface cant, the uneven wear of the shoulder rib 23a by a road surface cant can further be suppressed.

  The relationship between the rubber gauge Sa and the rubber gauge Sb is preferably 1.0 ≦ Sa / Sb <2.0. By setting the ratio Sa / Sb between the rubber gauge near the tire maximum width position below the road surface cant and the rubber gauge near the tire maximum width position above the road surface cant to be 1.0 or more, the rigidity of the shoulder portion below the road surface cant is increased. The rigidity of the shoulder portion on the upper side of the road surface cant can be sufficiently increased. In addition, by setting the ratio Sa / Sb to less than 2.0, it is possible to secure a good tire shape and obtain an appropriate rigidity difference.

  In the pneumatic tire shown in FIG. 8, the gauge of the bead filler 42 from the carcass hoisting height position to the carcass main body along the perpendicular line from the height position of the carcass hoisting part 52 to the carcass main body 51 is the tire equator. The line C is different on the left and right.

  Specifically, when the bead filler gauge on the lower side of the road surface cant is BFa and the bead filler gauge on the upper side of the road surface cant is BFb, BFa> BFb. Thereby, the rigidity of the shoulder part below the road surface cant can be made higher than the rigidity of the shoulder part above the road surface cant, and uneven wear of the shoulder ribs 23a due to the road surface cant can be further suppressed.

  The relationship between the bead filler gauge BFa and the bead filler gauge BFb is preferably 1.0 ≦ BFa / BFb <1.5. By setting the ratio BFa / BFb between the bead filler gauge near the winding height position of the carcass below the road surface cant and the bead filler gauge near the winding height position of the carcass above the road surface cant to be 1.0 or more, The rigidity of the shoulder part on the lower side of the road surface cant can be sufficiently higher than the rigidity of the shoulder part on the upper side of the road surface cant. In addition, by setting the ratio BFa / BFb to less than 1.5, it is possible to ensure a good tire shape and obtain an appropriate rigidity difference.

  In the pneumatic tire 1 of the present embodiment described above, it is preferable that the profile of the outer surface (surface exposed to the outside) be symmetric with respect to the tire equator line C as an axis of symmetry in the tire meridian cross-sectional view. By making the profile of the outer surface symmetrical in this way, not only can the overall outer shape of the tire be aesthetically pleasing, but there is no need to provide a dedicated mold when manufacturing the tire, making the tire cheaper And it can be manufactured easily.

  Here, as described above, the pneumatic tire 1 is such that the relationship between the carcass peripheral lengths Pa and Pb is set to Pa <Pb for the carcass 5. Therefore, by making the profile of the outer surface symmetrical, it is possible to easily increase the rubber amount of the side wall portion below the road surface cant than the rubber amount of the side wall portion above the road surface cant. Thereby, the force which pushes the tire 1 with respect to the road surface mentioned above to the direction which goes to a road surface cant upper side from a road surface cant upper side can be made into a force more than fixed. The pneumatic tire preferably has a profile symmetrical shape on at least the outer surface of the sidewall portion, and more preferably has a profile symmetrical shape on the outer surface of the sidewall portion and the shoulder portion.

  Moreover, it is preferable that the pneumatic tire 1 of this embodiment is applied to a heavy duty pneumatic tire. That is, it is preferably used as a tire to be mounted on a truck or bus that travels at high speed for a long time. In such an application, uneven wear of the shoulder rib due to the road surface cant is likely to occur. Therefore, there is an advantage that the effect of suppressing the uneven wear of the shoulder rib described above can be obtained more remarkably.

  In addition, as shown in FIG. 2, the pneumatic tire 1 of the present embodiment is preferably mounted in pairs on the left and right sides of the vehicle steering axis S. Since the left and right sides of the vehicle steering axis S are mounted in pairs, a force that pushes the tire 1 in the direction from the lower side of the road surface cant to the upper side of the road surface can be generated on the road surface. There is an advantage that the effect of suppressing the uneven wear of the shoulder rib can be obtained more remarkably.

[Evaluation]
Pneumatic tires according to the present embodiment, conventional examples, and comparative examples were produced and evaluated. The embodiment according to the present embodiment is an example. The comparative example does not indicate a conventional example.

  Carcass periphery length ratio Pa / Pb, carcass radius ratio RUa / RUb, carcass radius ratio RLa / RLb, tread rubber gauge ratio La / Lb, tread rubber gauge ratio Ua / Ub, belt width ratio BLa / BLb, belt width ratio BUa / BUb, rubber gauge ratio Ta / Tb, rubber gauge ratio Sa / Sb, and bead filler gauge ratio BFa / BFb were set as shown in Table 1, and air according to Examples 1 to 7, conventional examples, and comparative examples Each tire was prepared. These parameters are based on those described with reference to FIGS.

  About the pneumatic tire which concerns on Examples 1-7, a prior art example, and a comparative example, the performance test regarding the uneven wear resistance of a shoulder rib was done. In this performance test, a pneumatic tire with a tire size of 11R22.5 was mounted on a regular rim, filled with regular internal pressure, and mounted on the left and right sides of the steer shaft of a test vehicle (a biaxial trailer with a 4x2 tractor). .

  Here, 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 for uneven wear resistance, the above-mentioned test vehicle traveled on a paved road having a road surface cant, and the running distance where uneven wear (dent amount: 1 [mm]) began to occur was evaluated based on the conventional example. did. This evaluation is indicated by an index value based on the conventional pneumatic tire as a reference (100), and the larger the index value, the better the uneven wear resistance. The results for uneven wear resistance are also shown in Table 1.

  As is clear from Table 1, in the pneumatic tires according to Examples 1 to 7 within the scope of the present invention (Pa <Pb), both are superior to the conventional example (Pa = Pb). It can be seen that it shows wear. On the other hand, it can be seen that the pneumatic tire according to the comparative example outside the scope of the present invention (Pa> Pb) does not show the uneven wear resistance superior to the conventional example (Pa = Pb).

  Further, considering each of Examples 1 to 7, first, in Examples 1 and 2, as specific means for setting Pa / Pb to 0.97 and 0.98, respectively, RUa / RUb is set to 1.1, 1.1 and RLa / RLb are 1.1 and 1.0. In Examples 1 and 2, La / Lb is 1.3, and the evaluation values of uneven wear resistance are 105 and 103, respectively. For this reason, it can be said that uneven wear resistance is improved by changing only the ratio of the carcass periphery length Pa / Pb.

  Furthermore, about Examples 1-7, it turns out that what increased the kind of said parameter (Pa / Pb etc.) shows the outstanding wear resistance.

  As described above, the pneumatic tire according to the present invention is useful for suppressing uneven wear of the shoulder rib of the tread portion due to the road surface cant.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 21 Tread surface 22 Circumferential main groove 22a Shoulder side circumferential main groove 23 Rib 23a Shoulder rib 3 Side wall part 4 Bead part 41 Bead core 41a Bead wire 42 Bead filler 42a Hard bead filler 42b Soft bead filler 5 Carcass 6 Belt Layers 61, 62, 63, 64 Belt BFa, BFb Bead filler gauge BFUa, BFUb Hard bead filler 42a highest position BLa, BLb, BUa, BUb Belt width C from equator line C Tire equator plane (tire equator line)
F Force La, Lb Tread rubber gauge Ma, Mb Maximum tire width position R Road surface RLa, RLb, RUa, RUb Carcass radius S Steer shaft Sa, Sb, Ta, Tb Rubber gauge TL Tension when filling with internal pressure under road surface cant TU road surface Tension TSa, TSb Shoulder portion predetermined position TW Tread developed width half width Ua, Ub Tread rubber gauge X Intersection Ya of carcass 5 and tire equator line C, extension line of upper surface of bead core Intersection with

Claims (10)

A pair of left and right bead cores;
A bead filler disposed on the outer side in the tire radial direction of the bead core; and a carcass disposed between the pair of left and right bead cores;
A belt layer disposed on the outer side in the tire radial direction of the carcass;
A tread portion including at least two circumferential main grooves provided along the tire circumferential direction,
The carcass is a carcass periphery from the intersection of the tire equator line and the carcass to the intersection of the bead core upper surface on one side of the tire equator line and the carcass on the inner circumference side of the tire in the tire meridian cross-sectional view. When the length is Pa, and the carcass peripheral length from the intersection of the tire equator line to the carcass to the intersection of the extension line on the other side of the bead core and the carcass on the inner circumference side of the tire equator line is Pb Pa <Pb der Ri in,
And, in the tire meridian cross-sectional view, the carcass radius from one side of the tire equator line to the maximum tire width position is RUa, and the other side of the tire equator line is the tire from the shoulder part. RUa> RUb when the carcass radius is RUb up to the maximum width position,
And, in the tire meridian section, RLa is the carcass radius from the tire maximum width position to the highest position of the hard bead filler on the one side of the tire equator line, and the tire maximum width on the other side of the tire equator line a pneumatic tire characterized by RLa> RLb der Rukoto when the carcass radius of up to the highest position of the hard bead filler was RLb from the position. The tread portion is perpendicular to the tread tread surface at a position on the tire equator line side by 20% of the half width TW of the tread deployment width from the shoulder end on one side of the tire equator line as viewed from the tire meridian section. The tread rubber gauge up to the outermost layer of the lowered belt is La, and from the tread tread at the position on the tire equator line side by 20% of the half width TW of the tread deployment width from the shoulder end on the other side of the tire equator line. the pneumatic tire according to claim 1, characterized in that the tread rubber gauge to the belt outermost layer a perpendicular line is dropped when the Lb is La> Lb. The tread portion has a tread rubber gauge Ua from the circumferential main groove bottom on the shoulder side to the belt outermost layer on the one side with the tire equator line as a boundary in the tire meridional section, and the tire equator line as a boundary. 3. The pneumatic tire according to claim 1, wherein Ua> Ub when the tread rubber gauge from the shoulder-side circumferential main groove bottom to the belt outermost layer is defined as Ub. The belt layer has at least two belts adjacent to each other with cords intersecting in a tire meridian cross-sectional view,
Of the at least two belts, the belt on the inner circumference side of the tire has a width of BLa from the tire equator line to the belt end on one side of the tire equator line, and the tire equator line from the tire equator line. BLa> BLb, where BLb is the belt width to the belt end on the other side of the boundary,
Of the at least two belts, the belt on the outer periphery side of the tire has a belt width from the tire equator line to the belt end on one side of the tire equator line as BUa, and from the tire equator line to the tire equator line. the pneumatic tire according to any one of claims 1 to 3, characterized in that the BUa> BUb when the belt width to the belt end portion on the other side was BUb you. In the tire meridian cross-sectional view, Ta is the rubber gauge from the outer surface of the carcass to the inner surface of the maximum width belt when the vertical line is lowered from the shoulder end to the carcass on one side of the tire equator line, and the tire equator line is the boundary. any were on the other side, from the carcass outer surface of the case of a perpendicular line is drawn from the shoulder end to the carcass of the rubber gauge of up to the maximum width belt inner surface of claim 1, characterized in that the Ta> Tb when the Tb 4 The pneumatic tire according to claim 1. In the tire meridional section, the rubber gauge from the outer surface of the carcass to the surface of the sidewall at the tire maximum width position on the one side with the tire equator line as the boundary is Sa, and the tire on the other side with the tire equator line as the boundary. The pneumatic tire according to any one of claims 1 to 5 , wherein Sa> Sb when a rubber gauge from the outer surface of the carcass to the surface of the sidewall portion at a large position is Sb. The bead filler is a bead filler extending from the carcass hoisting height position to the carcass main body along the vertical line extending from the carcass hoisting height position to the carcass main body on one side of the tire meridian section as viewed from the tire meridional section. When the gauge is BFa and the bead filler gauge from the carcass hoisting height position to the carcass main body along the perpendicular line from the carcass hoisting height position to the carcass main body on the other side of the tire equator line is BFb the pneumatic tire according to any one of claims 1 6, characterized in that the BFa> BFb to. The pneumatic tire according to any one of claims 1 to 7 , wherein, in a tire meridional section, the profile is symmetrical on the left and right with respect to the tire equator line. The pneumatic tire according to any one of claims 1 to 8 , wherein the pneumatic tire is applied to a heavy duty pneumatic tire. The pneumatic tire according to any one of claims 1 to 9 , wherein the pneumatic tire is mounted in a pair on the left and right sides of a vehicle steering axis.

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