JP5521730B2 - 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-mentioned problems and achieve the object, the pneumatic tire of the present invention has at least two circumferential main grooves provided along the tire circumferential direction in the tread portion, and the traveling direction is In the designated pneumatic tire, when mounted on a vehicle, the traveling direction is designated in such a manner that one side of the tire equatorial plane is positioned above the road surface cant and the other side is positioned below the road surface cant, the boundary of a tire equatorial plane, the tread rigidity of the one side and SU, the tread rigidity of the other side when the SL, comprising a tread pattern of the asymmetric as the SU <SL, the boundary of the tire equatorial plane, wherein When the groove area ratio on one side is AU and the groove area ratio on the other side is AL, AU> AL .

  According to this pneumatic tire, since the tread rigidity SL on the other side of the tire equator plane is larger than the tread rigidity SU on the one side, when mounted on a vehicle, one side is the road surface cant upper side, By setting the other side to the lower side of the road surface cant, when driving straight on a road surface having a road surface cant, a force that moves upward on the road surface cant is generated on the tread surface that contacts the road surface so as to increase the inclination, and the road surface to decrease the inclination. The lateral force that elastically deforms can be suppressed when facing down the cant. 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.

Also, according to this pneumatic tire, the groove area ratio AU on one side of the tire equator plane is made larger than the groove area ratio AL on the other side. Since the tread rigidity SL on the lower side of the road surface cant is larger than the tread rigidity SU on the upper side of the road surface cant, the uneven wear of the shoulder rib due to the road surface cant is suppressed. be able to. Further, according to this pneumatic tire, 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 effects described above can be obtained as appropriate.

Further, in the pneumatic tire of the present invention, in the circumferential main grooves by each shoulder rib formed on the outermost side in the tire width direction, the tire widthwise dimension of the shoulder rib of the one side was the boundary of the tire equatorial plane WU If the tire width direction dimension of the shoulder rib of the other side was WL, characterized in that it is a WU <WL.

  According to this pneumatic tire, the tire width direction dimension WL of the other side shoulder rib with the tire equatorial plane as a boundary is larger than the tire width direction dimension WU of the one side shoulder rib. In this case, by setting one side as the road surface cant upper side and the other side as the road surface cant lower side, the tread rigidity SL on the road surface cant lower side becomes larger than the tread rigidity SU on the road surface cant upper side. The uneven wear can be suppressed.

Further, the present invention in the pneumatic tire, the groove wall angle in the tire width direction outer side of each of the circumferential main groove in the tire width direction outermost side of the circumferential main grooves of the one side was the boundary of the tire equatorial plane the groove wall angle .theta.u If, and the groove wall angle of the circumferential main grooves of the other side and .theta.L, characterized in that it is a .theta.u <.theta.L.

  According to this pneumatic tire, the groove wall angle θL of the circumferential main groove on the other side of the tire equatorial plane is made larger than the groove wall angle θU of the circumferential main groove on the one side. When mounted, one side is the road surface cant upper side, and the other side is the road surface cant lower side, the rigidity of the shoulder ribs on the road surface cant lower side is increased, and the tread rigidity SL on the road surface cant lower side is the road surface cant upper side Therefore, uneven wear of the shoulder rib due to the road surface cant can be suppressed.

Further, in the pneumatic tire of the present invention, the circumferential main groove sipes have been formed on the tread of the formed ribs by a boundary of the tire equatorial plane, said one ρU a density of the sipes side, the other When the density of the sipes on the side is ρL, ρU> ρL.

  According to this pneumatic tire, the density ρU on one side of the tire equatorial plane is made larger than the density ρL on the other side, so when mounted on a vehicle, one side is on the road surface Since the tread rigidity SL on the lower side of the road surface cant is larger than the tread rigidity SU on the upper side of the road surface cant, the uneven wear of the shoulder rib due to the road surface cant can be suppressed. it can.

  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 a plan view of the pneumatic tire according to the embodiment of the present invention. FIG. 4 is a plan view of the pneumatic tire according to the embodiment of the present invention. FIG. 5 is a plan 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 a plan view of the pneumatic tire according to the embodiment of the present invention. FIG. 8 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 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 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 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 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. When the pneumatic tire 1 in the present embodiment having the above-described configuration is mounted on a vehicle, the traveling direction is specified 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. When the vehicle travels straight on a road surface having a road surface cant, the tire tread stiffness on the upper side of the road surface cant is defined by SU. When the tread rigidity on the other side of the road surface under the cant is SL, an asymmetric tread pattern of SU <SL is provided.

  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 this pneumatic tire 1, when the tire equatorial plane C is the boundary, the tread rigidity SL on the lower side of the road surface cant is larger than the tread rigidity SU on the upper side of the road surface cant, and therefore when traveling straight on the road surface having the road surface cant The tread 21 that contacts the road surface generates a force P toward the upper side of the road surface cant so as to increase the inclination, and the lateral force that is elastically deformed when the lower surface of the road surface cant is lowered so as to decrease the inclination is suppressed. 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 shown in FIG. 3, the asymmetric tread pattern with respect to the tire equatorial plane C is defined as AU with the groove area ratio on the upper side of the road surface cant and AU with the groove area ratio on the lower side of the road surface cant as shown in FIG. In this case, AU> AL.

  The groove area ratio is the ratio of the grooves on the surface of the tread portion 2 over the entire circumference of the tire, that is, the total groove area with respect to the ground contact area of the tire (the area of the tread surface 21 of the rib 23) 22 and the ratio of the opening area of grooves (not shown) other than the circumferential main groove 22. Further, as means for varying the groove area ratio with the tire equatorial plane C as a boundary, the total groove area is changed by increasing the groove width and the number of grooves on the road surface cant upper side than on the road surface cant lower side. As another means for changing the groove area ratio, the ground contact area is changed by increasing the rib width on the lower side of the road surface than the upper side of the road surface.

  According to the pneumatic tire 1, the groove area ratio AU on the upper side of the road surface cant is larger than the groove area ratio AL on the lower side of the road surface cant, with the tire equatorial plane C as a boundary, so that the tread rigidity on the lower side of the road surface cant is reduced. Since SL becomes larger than the tread rigidity SU 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.

  The relationship AU> AL is preferably in the range of 0 <(AU−AL) ≦ + 10 [%]. When the value obtained by subtracting the groove area ratio AL below the road surface cant from the groove area ratio AU above the road surface cant exceeds +10 [%], the force P toward the road surface upper side is increased so that the rigidity difference is too large and the slope rises. It will occur.

  Further, as an asymmetric tread pattern with the tire equatorial plane C as a boundary, as shown in FIG. 4 and FIG. 5, in each shoulder rib 23a, the tire width direction dimension of the shoulder rib 23a above the road surface cant is WU, and the road surface under the cant When the tire width direction dimension of the side shoulder rib 23a is WL, WU <WL.

  As means for varying the tire width direction dimension of each shoulder rib 23a with respect to the tire equatorial plane C, the groove width, groove position, and number of grooves are changed. Specifically, in the case of the circumferential main groove 22, the number of grooves is the same, and the groove width is increased above the road surface cant from the lower surface of the road surface (see FIGS. 4 and 5), or the number of grooves is the same. Whether the groove position is provided closer to the tire equatorial plane C than the upper side of the road surface cant (see FIGS. 4 and 5), or the number of grooves is increased above the lower side of the road surface cant with the same groove width. (Refer to FIG. 5), these means are combined.

  According to this pneumatic tire 1, with the tire equatorial plane C as a boundary, the tire width direction dimension WL of the shoulder rib 23a on the lower side of the road surface cant is made larger than the tire width direction dimension WU of the shoulder rib 23a on the upper side of the road surface cant. Thus, since the tread rigidity SL on the lower side of the road surface cant becomes larger than the tread rigidity SU 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.

  The relationship of WU <WL is preferably in the range of 0 <WL / WU ≦ 1.3. If the ratio of the tire width direction dimension WL of the shoulder rib 23a below the road surface cant to the tire width direction dimension WU of the shoulder rib 23a above the road surface cant exceeds 1.3, the difference in rigidity is too large to increase the inclination. Force P toward the upper side of the road surface is generated.

  In addition, when changing the groove number of the circumferential direction main groove 22, it is preferable that the difference of a road surface cant lower side and a road surface cant upper side is set to one with the tire equatorial plane C as a boundary. If the difference is 2 or more, 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.

  When the tire width direction dimension of each shoulder rib 23a is made different from the tire equatorial plane C as a boundary, the groove area ratio AU above the road surface cant and the groove area ratio AL below the road cant from the tire equatorial plane C The relationship is preferably AU ≧ AL. This is because if AU <AL, the effect of the shoulder rib 23a is canceled out by the groove area ratio.

  Moreover, as an asymmetric tread pattern with the tire equator plane C as a boundary, as shown in FIG. 6, at the groove wall angle on the outer side in the tire width direction of each circumferential main groove 22 on the outermost side in the tire width direction, When the groove wall angle of the circumferential main groove 22 is θU and the groove wall angle of the circumferential main groove 22 below the road surface cant is θL, θU <θL.

  Here, the groove wall angle refers to the angle of the groove wall of the circumferential main groove 22 with respect to the normal line of the surface of the tread portion 2.

  According to this pneumatic tire 1, the groove wall angle θL of the circumferential main groove 22 on the lower side of the road surface cant is made larger than the groove wall angle θU of the circumferential direction main groove 22 on the upper side of the road surface cant. The shoulder rib 23a on the side becomes higher, and the tread rigidity SL on the lower side of the road surface cant becomes larger than the tread rigidity SU on the upper side of the road surface cant, so that uneven wear of the shoulder rib 23a due to the road surface cant can be suppressed. Become.

  When the groove wall of the circumferential main groove 22 has a constant angle in the tire circumferential direction, the groove wall angles are θU and θL. When the angle of the groove wall of the circumferential main groove 22 changes in the tire circumferential direction, the average groove wall angle in the tire circumferential direction is defined as θU and θL. Also, one of the groove wall of the circumferential main groove 22 on the lower side of the road surface cant and the groove wall of the circumferential main groove 22 on the upper side of the road surface cant has a constant angle in the tire circumferential direction, and the other has an angle change in the tire circumferential direction. In this case, according to the above, constant groove wall angles are set as θU and θL, and average groove wall angles at which the angles change are set as θU and θL.

  The relationship of θU <θL is preferably in a range of 0 <(θL−θU) ≦ + 20 [°]. When the value obtained by subtracting the groove wall angle θU of the circumferential main groove 22 on the upper side of the road surface cant from the groove wall angle θL of the circumferential main groove 22 on the lower side of the road surface cant exceeds +20 [°], the difference in rigidity is too large and the inclination is increased. A force P is generated toward the upper side of the road surface so as to go up.

  When the groove wall angle of the circumferential main groove 22 is varied, the relationship between the groove area ratio AU on the upper surface of the road surface cant and the groove area ratio AL on the lower side of the road surface cant is AU ≧ AL. It is preferable that This is because if AU <AL, the effect of the groove wall angle is canceled out by the groove area ratio. Further, when the groove wall angle of the circumferential main groove 22 is varied, the relationship between the tire width direction dimension WU of the shoulder rib 23a on the upper side of the road surface cant and the tire width direction dimension WL of the shoulder rib 23a on the lower side of the road surface cant is It is preferable to satisfy WU ≦ WL. This is because if WU> WL, the effect of the groove wall angle is canceled by the tire width direction dimension of the shoulder rib 23a.

  As an asymmetric tread pattern with the tire equatorial plane C as a boundary, a sipe 24 extending substantially in the tire width direction is formed on the tread surface 21 of the rib 23 formed by the circumferential main groove 22 as shown in FIG. When the density of the sipe 24 on the upper side of the road surface cant is ρU and the density of the sipe 24 on the lower side of the road surface cant is ρL with respect to the tire equatorial plane C, ρU> ρL.

  As means for changing the density of the sipe 24 at the tire equator plane C, the number (number), width (groove width), length (groove length), and depth (groove depth) of the sipe 24 are changed. . Specifically, the number of the sipe 24 on the upper side of the road surface cant is increased or the width of the sipe 24 on the upper side of the road surface cant is made larger than that of the sipe 24 on the lower side of the road surface cant. Alternatively, the length of the sipe 24 on the upper side of the road surface cant is made longer than the sipe 24 on the lower side of the road surface cant (including increasing the length of the sipe 24 by bending or bending), or the sipe 24 on the lower side of the road surface cant. Also, the depth of the sipe 24 on the upper side of the road surface cant is increased or these means are combined.

  According to this pneumatic tire 1, the density ρU of the sipe 24 on the upper side of the road surface cant is made larger than the density ρL of the sipe 24 on the lower side of the road surface cant, so that the tread rigidity SL on the lower side of the road surface cant is increased on the upper side of the road surface cant. Therefore, uneven wear of the shoulder ribs 23a due to the road surface cant can be suppressed.

  The relationship of ρU> ρL is preferably in the range of 0 <ρU / ρL ≦ 2.0. If the ratio of the density ρU of the sipe 24 on the road surface cant to the density ρL of the sipe 24 on the lower side of the road surface cant exceeds 2.0, a force P is generated toward the upper side of the road surface cant so that the rigidity difference is too large and the slope rises. End up.

  When the density of the sipes 24 is different, the relationship between the groove area ratio AU on the road surface cant upper side and the groove area ratio AL on the road surface lower side on the tire equatorial plane C is preferably AU ≧ AL. . This is because if AU <AL, the effect of the density of the sipe 24 is canceled out by the groove area ratio. Further, when the densities of the sipes 24 are made different, the relationship between the tire width direction dimension WU of the shoulder rib 23a on the upper side of the road surface cant and the tire width direction dimension WL of the shoulder rib 23a on the lower side of the road surface cant is WU ≦ WL. It is preferable. This is because if WU> WL, the effect of the density of the sipe 24 is canceled out in the tire width direction dimension of the shoulder rib 23a. Further, when the densities of the sipes 24 are made different, the relationship between the groove wall angle θU of the circumferential main groove 22 on the upper side of the road surface cant and the groove wall angle θL of the circumferential main groove 22 on the lower side of the road surface cant is expressed as θU ≦ θL. It is preferable that This is because if θU> θL, the effect of the density of the sipe 24 is canceled out at the groove wall angle of the circumferential main groove 22. Further, when the groove area ratio, the tire width direction dimension of the shoulder rib 23a, and the groove wall angle of the circumferential main groove 22 are made different, the density ρU of the sipe 24 on the upper side of the road surface cant and the sipe 24 on the lower side of the road surface cant. The relationship with the density ρL is preferably ρU ≧ ρL. This is because if ρU <ρL, other effects are canceled out by the density of the sipe 24.

  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, heavy duty pneumatic tires are particularly 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. It is in. 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.

  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 this pneumatic tire, a pair of left and right sides of the vehicle steering axis S are mounted so that a force toward the upper side of the road surface cant is generated in left and right pairs. There is an advantage that the 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. 8).

  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 conventional pneumatic tire has a groove area ratio difference (AU−AL) [%], a shoulder rib tire width direction dimension (WU / WL), a groove wall angle difference (θL−θU) [°], and All of the sipe densities (ρU / ρL) are outside the specified range.

  In the pneumatic tire of the comparative example, the difference (AU−AL) [%] in the groove area ratio is −5, which is outside the specified range.

  On the other hand, in the pneumatic tires of Examples 1 and 2, the difference in groove area ratio (AU-AL) [%] is within the specified range, and the pneumatic tire of Example 3 is the tire width of the shoulder rib. The directional dimension (WU / WL) is within a specified range, and the pneumatic tires of Examples 4 and 5 have a groove wall angle difference (θL−θU) [°] within a specified range. This pneumatic tire has a sipe density (ρU / ρL) within a specified range.

  As shown in the test results of FIG. 8, it can be seen that the pneumatic tires of Examples 1 to 6 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 24 Sipe 3 Side wall part 4 Bead part 41 Bead core 41a Bead wire 42 Bead filler 5 Carcass 6 Belt layers 61, 62, 63, 64 Belt C Tire equator Surface (tire equator line)
P Force R Road surface S Steer shaft SL Tread rigidity under the road surface cant SU Tread rigidity above the road surface cant AL Groove area ratio under the road surface cant AU Groove area ratio above the road surface cant WL Tire width of the shoulder rib under the road surface cant Directional dimension WU Tire width dimension of shoulder rib on upper side of road surface cant θL Groove wall angle of main groove on lower side of road surface cant θU Wall angle of main groove on upper side of road surface cant ρL Density of sipe on lower side of road surface ρU The density of the sipe above the road surface cant

Claims (6)

In a pneumatic tire having at least two circumferential main grooves provided along the tire circumferential direction in the tread portion and having a designated traveling direction,
When mounted on a vehicle, the direction of travel is specified in such a manner that one side of the tire equator plane is located above the road surface cant and the other side is located below the road surface cant,
The boundary of the tire equatorial plane, the tread rigidity of the one side and SU, if the tread rigidity of the other side was SL, comprising a tread pattern of the asymmetric as the SU <SL,
A pneumatic tire characterized in that AU> AL when the groove area ratio on the one side is AU and the groove area ratio on the other side is AL, with the tire equatorial plane as a boundary . In the circumferential main grooves by each shoulder rib formed on the outermost side in the tire width direction, WU tire width direction dimension of the shoulder rib of the one side was the boundary of a tire equatorial plane, the other side of the shoulder rib of the tire width The pneumatic tire according to claim 1 , wherein WU <WL when the directional dimension is WL. In the groove wall angle in the tire width direction outer side of each of the circumferential main groove in the tire width direction outermost side, a groove wall angle of the circumferential main grooves of the one side was the boundary of the tire equatorial plane .theta.u, the other side If the .theta.L the groove wall angle of the circumferential main grooves, the pneumatic tire according to claim 1 or 2, characterized in that a .theta.u <.theta.L. The circumferential main grooves and sipes are formed in the tread of the formed ribs by a boundary of the tire equatorial plane, said one ρU a density of the sipes side, and the density of the sipes of the other side and ρL The pneumatic tire according to claim 1 , wherein ρU> ρL. The pneumatic tire according to any one of claims 1 to 4 , wherein the pneumatic tire is applied to a heavy duty pneumatic tire. The pneumatic tire according to any one of claims 1 to 5 , wherein the pneumatic tire is mounted in a pair on the left and right sides of a vehicle steering axis.

Images