JP5521752B2 - 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 shoulder ribs of a tread 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 on the shoulder rib 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 ribs 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 rib in this way, the lateral force toward the lower side of the road surface cant increases, and a slip angle is further imparted to try to travel straight on the road surface cant against this 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, when the pneumatic tire of the present invention is mounted on a vehicle, one side of the tire equatorial plane is located on the upper side of the road surface and the other side is on the lower side of the road surface. The rubber is placed on the outside of the carcass at a symmetrical position with the tire equatorial plane as a boundary, and the traveling direction is specified in a manner located at When the rubber hardness of GU is GU and the rubber hardness of the other side is GL, GU <GL.

  According to this pneumatic tire, the rubber hardness GL on the other side is made higher than the rubber hardness GU on the one side at a symmetrical position with respect to the tire equatorial plane. Since it is larger than the rubber rigidity, when mounted on a vehicle, when one side is the road surface cant upper side and the other side is the road surface cant lower side, when running straight on the road surface having the road surface cant, the tread surface that contacts the road surface In addition, a force toward the upper side of the road surface cant is generated so as to go up the slope, and a lateral force that is elastically deformed when going down to the lower side of the road surface cant so as to go down the slope is suppressed. As a result, the occurrence of polygonal wear in which the outermost shoulder rib in the tire width direction on the lower side of the cant of the pneumatic tire is worn unevenly and the wear speed of the polygonal wear are delayed with respect to the travel distance. The uneven wear of the shoulder rib due to can be suppressed.

  In the pneumatic tire of the present invention, the tread portion has at least three ribs formed by at least two circumferential main grooves provided along the tire circumferential direction, and at least two types of rubber in the tire width direction. Concerning the cap tread rubber of the shoulder rib formed at least on the outermost side in the tire width direction, the rubber hardness on the other side of the tire equatorial plane is the boundary. It is characterized by a high.

  According to this pneumatic tire, the rubber hardness on the other side is higher than the rubber hardness on the other side of the tire equatorial plane, at least for the shoulder rib cap tread rubber formed on the outermost side in the tire width direction. When mounted on a vehicle, the rubber stiffness on the lower side of the road surface cant is greater than the rubber stiffness on the upper side of the road surface cant because one side is the upper side of the road surface cant and the other side is the lower side of the road surface cant. The uneven wear of the shoulder rib due to can be suppressed.

  In the pneumatic tire of the present invention, the tread portion has at least three ribs formed by at least two circumferential main grooves provided along the tire circumferential direction, and at least two types of rubber in the tire width direction. Concerning the under tread rubber of the shoulder rib, which is configured to have an under tread rubber of hardness and is formed at least on the outermost side in the tire width direction, the rubber hardness on the other side than the rubber hardness on one side with the tire equator plane as a boundary It is characterized by a high.

  According to this pneumatic tire, at least the shoulder rib undertread rubber formed on the outermost side in the tire width direction has a higher rubber hardness on the other side than the rubber hardness on the one side bordered by the tire equatorial plane. When mounted on a vehicle, the rubber stiffness on the lower side of the road surface cant is greater than the rubber stiffness on the upper side of the road surface cant because one side is the upper side of the road surface cant and the other side is the lower side of the road surface cant. The uneven wear of the shoulder rib due to can be suppressed.

  Further, in the pneumatic tire of the present invention, the tread portion is configured to have at least three ribs formed by at least two circumferential main grooves provided along the tire circumferential direction and to have an undertread rubber. The undertread rubber of the shoulder rib formed at least on the outermost side in the tire width direction is characterized in that the area on one side is made larger than the area on the other side of the tire meridian section at the tire equatorial plane. .

  According to this pneumatic tire, for either one or both of the cap tread rubber and the under tread rubber, the rubber hardness on the other side is higher than the rubber hardness on the other side of the tire equatorial plane, and the under tread rubber Since the tire meridian cross-sectional area is larger on one side than the other side of the tire equatorial plane, when mounted on a vehicle, one side is the road surface cant upper side and the other side is the road surface cant lower side. By doing so, since the rubber rigidity on the lower side of the road surface cant becomes larger than the rubber rigidity on the upper side of the road surface cant, uneven wear of the shoulder ribs due to the road surface cant can be suppressed.

  The pneumatic tire of the present invention is characterized in that the rubber hardness on the other side is higher than the rubber hardness on the one side with respect to the tire equatorial plane as to the side rubber of each sidewall portion on both sides in the tire width direction. .

  According to this pneumatic tire, since the rubber hardness on the other side is higher than the rubber hardness on the other side with respect to the tire equatorial plane, the side rubber of each sidewall portion on both sides in the tire width direction is attached to the vehicle. In this case, by setting one side as the upper surface of the road surface cant and the other side as the lower surface of the road surface cant, the rubber rigidity of the lower surface of the road surface cant is greater than the rubber rigidity of the upper surface of the road surface cant. Since the side wall portion is less bent on the side, and the tread surface that contacts the road surface generates a force toward the upper side of the road surface cant so as to increase the slope, uneven wear of the shoulder rib due to the road surface cant can be suppressed.

  In the pneumatic tire of the present invention, the bead filler at each bead portion on both sides in the tire width direction is characterized in that the rubber hardness on the other side is higher than the rubber hardness on the one side with the tire equatorial plane as a boundary.

  According to this pneumatic tire, the bead filler on each bead portion on both sides in the tire width direction has a rubber hardness on the other side higher than the rubber hardness on the other side with respect to the tire equatorial plane. By setting one side as the road surface cant upper side and the other side as the road surface cant lower side, the rubber rigidity on the lower side of the road surface cant becomes larger than the rubber rigidity on the upper side of the road surface cant. Can be suppressed.

  The pneumatic tire of the present invention is characterized by being applied to a heavy duty pneumatic tire.

  According to this pneumatic tire, a heavy duty pneumatic tire is used for a truck or a bus that travels at a high speed for a long time, particularly on a road surface provided with a road surface cant. By setting the other side to the lower side of the road surface cant, uneven wear of the shoulder ribs due to the road surface cant tends to occur. Therefore, there is an advantage that the effect of suppressing the uneven wear of the shoulder ribs by the road surface cant can be obtained more significantly by making the heavy duty pneumatic tire applicable.

  In addition, the pneumatic tire of the present invention is mounted in pairs on the left and right of the vehicle steering axis.

  According to this pneumatic tire, by mounting in pairs on the left and right of the vehicle's steering shaft, when mounted on a vehicle, one side is the road surface cant upper side, the other side is the road surface cant lower side, Since the force directed to the upper side of the road surface cant is generated in left and right pairs, there is an advantage that the effect of suppressing the uneven wear of the shoulder rib by the road surface cant can be obtained more remarkably.

  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 an embodiment of the present invention. FIG. 2 is a schematic view of a pneumatic tire according to an embodiment of the present invention mounted on a vehicle. FIG. 3 is an enlarged meridian cross-sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 4 is an enlarged meridian cross-sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 5 is an enlarged meridian cross-sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 6 is a meridian enlarged cross-sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 7 is an enlarged meridian cross-sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 8 is an enlarged meridian cross-sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 9 is an enlarged meridian cross-sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 10 is an enlarged meridian cross-sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 11 is an enlarged meridian cross-sectional view of the pneumatic tire according to the embodiment of the present invention. FIG. 12 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

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

  In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire radial direction outer side. The term “side away from the rotation axis” in the tire radial 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 and bead portions 4 on both sides thereof. Further, the pneumatic tire 1 has a carcass 5 and a belt layer 6.

  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 the circumferential main grooves 22. The outermost ribs 23 in the tire width direction form shoulder ribs 23a.

  The tread portion 2 includes a cap tread rubber 2 a that forms the tread 21, and an under tread rubber provided on the inner side in the tire radial direction of the cap tread rubber 2 a and between the cap tread rubber 2 a and the belt layer 6. 2b.

  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 sidewall portion 3 is formed of a side rubber 3 a that forms the outer peripheral surface of the sidewall portion 3 and is provided outside the carcass 5. 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 41a, 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 is a rubber material 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 bead filler 42 is configured by being divided into a hard rubber 42a provided along the tire radial direction outside of the bead core 41 and a soft rubber 42b provided outside the hard rubber 42a in the tire radial direction, or Although not clearly shown in the figure, the whole is composed of a single hard rubber. The bead filler 42 is disposed outside the carcass 5 except for the folded portion of the carcass 5, and in this embodiment, the bead filler 42 is defined as being disposed outside the carcass 5.

  The carcass 5 has a tread portion 2, both sidewall portions 3, and both bead portions 4 that are continuously straddled, with both ends in the tire width direction being wound around the pair of bead portions 4 and a toroid 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 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 belt layer 6 is disposed 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 a pneumatic tire according to an embodiment of the present invention mounted on a vehicle. The pneumatic tire 1 in the present embodiment having the above-described configuration has a symmetrical profile with respect to the tire equatorial plane C. And as shown in FIG. 2, when attaching to a vehicle, the advancing direction is designated in the tire circumferential direction. The designation of the traveling direction is not clearly shown in the figure, but is indicated by, for example, an index provided on the side wall. The pneumatic tire 1 is mounted on each of the left and right sides of the vehicle steering axis S, and when traveling straight on a road surface having a road surface cant, rubber (tread rubber 2a, 2b, side rubber 3a, or At least one of the bead fillers 42) is symmetric with respect to the tire equatorial plane C, and the rubber hardness (JIS-A hardness) on the upper side of the road surface cant is GU, and the lower side of the road surface cant is on the other side. When the rubber hardness (JIS-A hardness) is GL, GU <GL.

  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.

  According to the pneumatic tire 1, the rubber hardness GL on the lower side of the road surface cant is higher than the rubber hardness GU on the upper side of the road surface cant at a symmetrical position with respect to the tire equatorial plane C. Since the rigidity is greater than the rubber rigidity on the upper side of the road surface cant, when the vehicle travels straight on the road surface having the road surface cant, a force P directed toward the upper side of the road surface cant is generated on the tread surface 21 in contact with the road surface so as to increase the inclination. The lateral force that is elastically deformed is suppressed when it goes to the lower side of the road surface. As a result, the occurrence of polygonal wear in which the outermost shoulder rib 23a in the tire width direction below the road surface cant of the pneumatic tire 1 wears unevenly, and the wear rate of the polygonal wear are delayed with respect to the travel distance. It is possible to suppress uneven wear of the shoulder rib 23a due to the road surface cant.

  As means for changing the rubber hardness at the symmetrical position with respect to the tire equatorial plane C, as shown in FIGS. 3 to 6, the tread portion 2 is a cap tread rubber 2a having at least two types of rubber hardness in the tire width direction. For the cap tread rubber 2a of the shoulder rib 23a formed at least on the outermost side in the tire width direction, the rubber hardness below the road surface cant is made higher than the rubber hardness above the road surface cant.

  Specifically, as illustrated in FIG. 3, the cap tread rubber 2a is divided into two on the tire equatorial plane C, the JIS-A rubber hardness on the upper side of the road surface cant is set to 63 degrees, for example, and the JIS on the lower side of the road surface cant. -A By setting the rubber hardness to, for example, 69 degrees, at least the cap tread rubber 2a of the shoulder rib 23a formed on the outermost side in the tire width direction, the rubber hardness below the road surface cant than the rubber hardness above the road surface cant To increase.

  Further, as illustrated in FIG. 4, the cap tread rubber 2 a is divided into two under the outermost circumferential main groove 22 in the tire width direction on the upper side of the road surface cant, and the JIS-A rubber hardness on the upper side of the road surface cant is set to 63, for example. [Degree], and by setting the JIS-A rubber hardness on the lower side of the road surface cant to 69 degrees, for example, at least the cap tread rubber 2a of the shoulder rib 23a formed on the outermost side in the tire width direction, The rubber hardness under the road surface cant is made higher than the rubber hardness.

  In addition, as illustrated in FIG. 5, the cap tread rubber 2 a is divided into three at each second rib position from the outer side in the tire width direction, and the JIS-A rubber hardness on the upper side of the road surface cant is set to 63 [degrees], for example. Cap tread of shoulder rib 23a formed at least on the outermost side in the tire width direction by setting the JIS-A rubber hardness to 66 [degrees] and the JIS-A rubber hardness below the road surface cant to 69 [degrees], for example. For the rubber 2a, the rubber hardness at the lower side of the road surface cant is made higher than the rubber hardness at the upper side of the road surface cant.

  Further, as illustrated in FIG. 6, the cap tread rubber 2 a is divided into two under the outermost circumferential main groove 22 in the tire width direction on the lower side of the road surface cant, and the JIS-A rubber hardness on the upper side of the road surface cant is, for example, 63 [degrees] and the JIS-A rubber hardness on the lower side of the road surface cant is 69 [degrees], for example, so that at least the cap tread rubber 2a of the shoulder rib 23a formed on the outermost side in the tire width direction is on the upper side of the road surface cant The rubber hardness on the lower side of the road surface cant is made higher than the rubber hardness.

  According to this pneumatic tire 1, at least for the cap tread rubber 2a of the shoulder rib 23a formed on the outermost side in the tire width direction, the rubber hardness on the road surface cant lower side is made higher than the rubber hardness on the road surface cant upper side, Since the rubber rigidity on the lower side of the road surface cant is larger than the rubber rigidity on the upper side of the road surface cant, it is possible to suppress uneven wear of the shoulder ribs 23a due to the road surface cant.

  When the rubber hardness on the lower side of the road surface cant is made higher than the rubber hardness on the upper side of the road surface for the cap tread rubber 2a, the relationship of GU <GL is 0 [degree] <(GL−GU) ≦ + 15 [degree]. It is preferable to set it as the range. When the rubber hardness of the cap tread rubber 2a on the upper side of the road surface cant exceeds +15 [degrees] from the rubber hardness of the cap tread rubber 2a on the lower side of the road surface cant, the force toward the upper side of the road surface cant is increased so that the difference in rigidity is too large P is generated.

  Further, as means for varying the rubber hardness at the symmetrical position with respect to the tire equatorial plane C, as shown in FIGS. 7 to 10, the tread portion 2 is an under tread having at least two types of rubber hardness in the tire width direction. For the under-tread rubber 2b of the shoulder rib 23a that is configured to have the rubber 2b and is formed at least on the outermost side in the tire width direction, the rubber hardness on the lower side of the road surface cant is made higher than the rubber hardness on the upper side of the road surface cant.

  Specifically, as illustrated in FIG. 7, the undertread rubber 2b is divided into two on the tire equatorial plane C, the JIS-A rubber hardness on the upper side of the road surface cant is set to 56 degrees, for example, and the JIS on the lower side of the road surface cant. -A By setting the rubber hardness to 67 degrees, for example, at least the under tread rubber 2b of the shoulder rib 23a formed on the outermost side in the tire width direction, the rubber hardness below the road surface cant than the rubber hardness above the road surface cant To increase.

  Further, as illustrated in FIG. 8, the under-tread rubber 2b is divided into two under the outermost circumferential main groove 22 in the tire width direction on the upper side of the road surface cant, and the JIS-A rubber hardness on the upper side of the road surface cant is set to 56, for example. [Degree], and by setting the JIS-A rubber hardness on the lower side of the road surface cant to, for example, 67 [degree], at least the undertread rubber 2b of the shoulder rib 23a formed on the outermost side in the tire width direction is on the upper side of the road surface cant. The rubber hardness under the road surface cant is made higher than the rubber hardness.

  Further, as illustrated in FIG. 9, the under tread rubber 2b is divided into three at each second rib position from the outer side in the tire width direction, and the JIS-A rubber hardness on the upper surface of the road surface cant is set to 56 [degrees], for example. By setting the JIS-A rubber hardness to, for example, 64 [degrees] and the JIS-A rubber hardness below the road surface cant to, for example, 67 [degrees], the under tread of the shoulder rib 23a formed at least on the outermost side in the tire width direction. Regarding the rubber 2b, the rubber hardness on the lower side of the road surface cant is made higher than the rubber hardness on the upper side of the road surface cant.

  Further, as illustrated in FIG. 10, the under tread rubber 2b is divided into two under the circumferential main groove 22 on the outermost side in the tire width direction on the lower side of the road surface cant, and the JIS-A rubber hardness on the upper side of the road surface cant is, for example, By setting the JIS-A rubber hardness on the lower side of the road surface cant to, for example, 67 [degrees], the upper surface of the road surface cant on the undertread rubber 2b of the shoulder rib 23a formed at least on the outermost side in the tire width direction. The rubber hardness on the lower side of the road surface cant is made higher than the rubber hardness.

  According to this pneumatic tire 1, at least for the under tread rubber 2b of the shoulder rib 23a formed on the outermost side in the tire width direction, by making the rubber hardness on the lower side of the road surface cant higher than the rubber hardness on the upper side of the road surface cant, Since the rubber rigidity on the lower side of the road surface cant is larger than the rubber rigidity on the upper side of the road surface cant, it is possible to suppress uneven wear of the shoulder ribs 23a due to the road surface cant.

  When the rubber hardness on the lower side of the road surface cant is made higher than the rubber hardness on the upper side of the road surface for the undertread rubber 2b, the relationship of GU <GL is 0 [degree] <(GL−GU) ≦ + 15 [degree]. It is preferable to set it as the range. If the rubber hardness of the undertread rubber 2b below the road surface cant exceeds +15 [degrees] from the rubber hardness of the undertread rubber 2b below the road surface cant, the force toward the upper surface of the road surface cant rises so that the difference in rigidity is too large P is generated.

  Further, as the rubber hardness at the symmetrical position with respect to the tire equatorial plane C, as shown in FIG. 11, the tread portion 2 is configured to have an under tread rubber 2b and is formed at least on the outermost side in the tire width direction. For the under tread rubber 2b of the shoulder rib 23a, the area on the upper side of the road surface cant is made larger than the area on the lower side of the road surface cant in the meridian section of the tire.

  Further, when the area of the tire tread section of the undertread rubber 2b is made larger on the upper side of the road surface cant than on the lower side of the road surface cant, as described above, either one or both of the cap tread rubber 2a and the undertread rubber 2b. The rubber hardness on the lower side of the road surface cant is made higher than the rubber hardness on the upper side of the road surface cant (see FIGS. 3 to 10).

  According to this pneumatic tire 1, the rubber hardness of the lower side of the road surface cant is made higher than the rubber hardness of the upper side of the road surface cant and either the cap tread rubber 2a or the under tread rubber 2b, and the under tread rubber 2b. By increasing the area of the tire meridional section above the road surface cant from the road surface lower side, the rubber rigidity at the lower side of the road surface cant becomes larger than the rubber rigidity at the upper side of the road surface cant. It becomes possible to suppress the uneven wear of 23a.

  When the area of the under tread rubber 2b in the tire meridional section is made larger on the upper side of the road surface cant than on the lower side of the road surface cant, the maximum tire radial dimension T1 of the under tread rubber 2b and the minimum tire at the position of the shoulder rib 23a. The difference (T1−T2) from the radial dimension T2 is preferably in the range of 0 [mm] <(T1−T2) ≦ 10 [mm]. When (T1-T2) exceeds 10 [mm], the difference in rigidity is too large and a force P is generated toward the upper side of the road surface cant so as to increase the slope.

  Further, as means for varying the rubber hardness at the symmetric position with respect to the tire equatorial plane C, as shown in FIG. 1, the rubber hardness on the road surface cant upper side of the side rubber 3a of each sidewall portion 3 on both sides in the tire width direction is shown. Increase the rubber hardness under the road surface cant.

  According to the pneumatic tire 1, the side rubber 3 a of each sidewall portion 3 on both sides in the tire width direction has a rubber hardness on the lower side of the road surface cant that is higher than the rubber hardness on the upper side of the road surface cant. Since the rubber rigidity is greater than the rubber rigidity on the upper side of the road surface cant, the deflection of the sidewall portion 3 is smaller on the lower side than the upper side of the road surface cant, and the road surface cant so as to increase the inclination to the tread surface 21 in contact with the road surface. Since the upward force P is generated, it is possible to suppress uneven wear of the shoulder rib 23a due to the road surface cant.

  When the rubber hardness on the lower side of the road surface cant is higher than the rubber hardness on the upper side of the road surface cant for the side rubber 3a, the rubber hardness on the upper side of the road surface cant (JIS-A hardness) with respect to the rubber hardness on the lower side of the road surface cant (JIS-A). The relationship of (A hardness) GU is preferably in the range of 0 [degree] <(GL-GU) ≦ + 10 [degree]. When the rubber hardness of the side rubber 3a on the upper side of the road surface cant exceeds +10 [degrees] with respect to the rubber hardness of the side rubber 3a on the lower side of the road surface cant, a force P directed toward the upper side of the road surface cant is generated so End up.

  Further, as means for varying the rubber hardness at the symmetrical position with respect to the tire equatorial plane C, as shown in FIG. 1, with respect to the bead filler 42 of each bead portion 4 on both sides in the tire width direction, the rubber hardness above the road surface cant Also increase the rubber hardness under the road surface cant.

  According to this pneumatic tire 1, the bead filler 42 of each bead portion 4 on both sides in the tire width direction has a rubber hardness on the lower side of the road surface cant lower than that on the upper side of the road surface cant. Since the rigidity is greater than the rubber rigidity on the upper side of the road surface cant, it is possible to suppress uneven wear of the shoulder rib 23a due to the road surface cant.

  In the case of the bead filler 42, when the rubber hardness below the road surface cant is higher than the rubber hardness above the road surface cant, the rubber hardness above the road surface cant (JIS-A hardness) GL relative to the rubber hardness below the road surface cant (JIS-A). The relationship of (A hardness) GU is preferably in the range of 0 [degrees] <(GL-GU) ≦ + 20 [degrees]. When the rubber hardness of the bead filler 42 on the upper side of the road surface cant exceeds +20 [degrees] relative to the rubber hardness of the bead filler 42 on the lower side of the road surface cant, a force P is generated toward the upper side of the road surface cant so as to increase the inclination because the difference in rigidity is too large. End up.

  When the bead filler 42 is configured by being divided into a hard rubber 42a provided along the tire radial direction outer side of the bead core 41 and a soft rubber 42b provided on the outer side of the hard rubber 42a in the tire radial direction, By changing the rubber hardness of at least the hard rubber 42a, the effect of suppressing uneven wear of the shoulder rib 23a by the road surface cant can be obtained more remarkably.

  Further, in the pneumatic tire 1 of the present embodiment, when mounted on a vehicle, the traveling direction is such that one side of the tire equator plane C is located on the upper side of the road surface cant and the other side is located on the lower side of the road surface cant. It is specified.

  According to this pneumatic tire 1, when mounted on a vehicle, the traveling direction is specified in such a manner that one side of the tire equator plane is positioned above the road surface cant and the other side is positioned below the road surface cant. Thus, the above-described effects can be obtained as appropriate.

  Moreover, it is preferable that the pneumatic tire 1 of this Embodiment is applied to the heavy load pneumatic tire.

  According to this pneumatic tire 1, since 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 a high speed, uneven wear of the shoulder ribs 23a due to the road surface cant occurs. It tends to be easy. Therefore, there is an advantage that the effect of suppressing the uneven wear of the shoulder ribs 23a by the road surface cant can be obtained more significantly by using the heavy duty pneumatic tire as an application target.

  Moreover, it is preferable that the pneumatic tire 1 of the present embodiment is mounted in a pair on the left and right of the vehicle steering axis S.

  According to the pneumatic tire 1, the pair of left and right sides of the vehicle steering axis S are mounted to generate a force P directed to the upper side of the road surface cant. There is an advantage that the uneven wear suppression effect can be obtained more remarkably.

  In this example, a performance test on uneven wear resistance of shoulder ribs was performed on a plurality of types of pneumatic tires having different conditions (see FIG. 12).

  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). .

  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. To do. This evaluation is indicated by an index value based on the conventional pneumatic tire as a reference (100). The larger the index value, the better the uneven wear resistance.

  The pneumatic tire of the conventional example has a difference in hardness of the cap tread rubber (GL-GU) [degree], a difference in hardness of the under tread rubber (GL-GU) [degree], and a difference in the tire radial dimension of the under tread rubber of the shoulder rib. All of (T1-T2) [mm], side rubber hardness difference (GL-GU) [degree], and bead filler hardness difference (GL-GU) [degree] are outside the specified ranges.

  In the pneumatic tire of the comparative example, the hardness difference (GL-GU) [degree] of the cap tread rubber is −5, which is outside the specified range.

  In contrast, in the pneumatic tires of Examples 1 to 3, the hardness difference (GL-GU) [degree] of the cap tread rubber is within the specified range. In the pneumatic tires of Examples 4 to 6, the hardness difference (GL-GU) [degree] of the undertread rubber is within the specified range. In the pneumatic tires of Example 7 and Example 8, the hardness difference (GL-GU) [degree] of the cap tread rubber and the tire radial direction dimension difference (T1-T2) [mm] of the under tread rubber of the shoulder rib are defined. Is within the range. In the pneumatic tires of Example 9 and Example 10, the hardness difference (GL-GU) [degree] of the under tread rubber and the tire radial dimension difference (T1-T2) [mm] of the under tread rubber of the shoulder rib are defined. Is within the range. In the pneumatic tire of Example 11, the difference in hardness (GL-GU) [degrees] of the side rubber is within the specified range. In the pneumatic tire of Example 12, the hardness difference (GL−GU) [degree] of the bead filler is within a specified range.

  As shown in the test results of FIG. 12, it can be seen that the pneumatic tires of Examples 1 to 12 are excellent in uneven wear resistance.

  As described above, the pneumatic tire according to the present invention is suitable 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 23 Rib 23a Shoulder rib 2a Cap tread rubber 2b Under tread rubber 3 Side wall part 3a Side rubber 4 Bead part 41 Bead core 41a Bead wire 42 Bead filler 42a Hard rubber 42b Soft rubber 5 Carcass 6 Belt layer 61, 62, 63, 64 Belt C Tire equator surface (tire equator line)
P Force R Road surface S Steer shaft GL Rubber hardness under the road surface cant GU Rubber hardness above the road surface cant T1 Maximum tire radial direction dimension of under tread rubber of shoulder rib T2 Minimum tire radial direction dimension of under tread rubber of shoulder rib

Claims (8)

When mounted on a vehicle, the direction of travel is specified in such a manner that one side of the tire equatorial plane is located above the road surface cant and the other side is located below the road surface cant, and the direction of travel is specified with respect to the tire equatorial plane. For a rubber having a profile and arranged on the outside of the carcass, when the rubber hardness on one side is GU and the rubber hardness on the other side is GL at a symmetrical position with the tire equatorial plane as a boundary, GU <GL air-filled tire it said that there. The tread portion has at least three ribs formed by at least two circumferential main grooves provided along the tire circumferential direction and has a cap tread rubber having at least two types of rubber hardness in the tire width direction. And
The rubber hardness on the other side of the cap tread rubber of the shoulder rib formed at least on the outermost side in the tire width direction is made higher than the rubber hardness on the other side of the tire equatorial plane. The described pneumatic tire. The tread portion has at least three ribs formed by at least two circumferential main grooves provided along the tire circumferential direction, and has an under tread rubber having at least two types of rubber hardness in the tire width direction. And
The rubber hardness on the other side of the undertread rubber of the shoulder rib formed at least on the outermost side in the tire width direction is made higher than the rubber hardness on the other side with respect to the tire equatorial plane. 2. The pneumatic tire according to 2. The tread portion has at least three ribs formed by at least two circumferential main grooves provided along the tire circumferential direction, and has an undertread rubber.
The undertread rubber of the shoulder rib formed at least on the outermost side in the tire width direction is characterized in that the area on one side is made larger than the area on the other side of the tire meridian section with the tire equatorial plane as a boundary. Item 4. The pneumatic tire according to Item 2 or 3.   The side rubber of each sidewall portion on both sides in the tire width direction has a rubber hardness on the other side higher than the rubber hardness on one side with the tire equatorial plane as a boundary. Pneumatic tire described in 2.   The bead filler of each bead part on both sides in the tire width direction has a higher rubber hardness on the other side than a rubber hardness on the other side with respect to the tire equatorial plane. The described pneumatic tire. The pneumatic tire according to claim 1 , wherein the pneumatic tire is applied to a heavy duty pneumatic tire. The pneumatic tire according to any one of claims 1 to 7 , wherein the pneumatic tire is mounted in pairs on the left and right sides of a vehicle steering axis.

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