JP2012153215A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the belt durability while securing an uneven wear resistance of a shoulder part.SOLUTION: Belt cushion rubber 81, belt edge cushion rubber 82, and edge cover rubber 83 are equally sized in a tire radial direction on each tire width outer side in a meridional cross section, and a loss tangent tanδ measured at 60(°C) on one tire width side is formed to be smaller than on the other tire width side, for at least one of the belt cushion rubber 81, belt edge cushion rubber 82, and edge cover rubber 83. Furthermore, a belt edge reinforcing layer 9 for covering a tire radial outer side of the edge cover rubber 83 is provided only on one tire width direction side.

Description

  The present invention relates to a pneumatic tire that improves belt durability while ensuring uneven wear resistance.

  For example, when transporting by a large truck or bus, in order to improve transport efficiency, it is desired to reduce fuel consumption and weight. For this reason, there is an increasing demand for pneumatic tires mounted on drive shafts and trailer shafts to be single mounted from conventional dual mounted. However, since a single-mounted pneumatic tire has a larger load load per pneumatic tire than a dual-mounted pneumatic tire, heat generation of the tire increases. In addition, the heat dissipation of the brake heat and engine heat is particularly poor at the vehicle inner side when the vehicle is mounted, compared to the vehicle outer side, and therefore, separation tends to occur at the belt edge portion inside the vehicle.

  Conventionally, for example, in the pneumatic tire described in Patent Document 1, in order to improve durability, it is between the carcass and the surface of the belt layer positioned on the innermost side in the tire radial direction, and the belt layer in the tire width direction. The rubber layer is provided at least at the positions of the belt end portions at both ends, and the thickness of the rubber layer is formed so that the belt end side on the vehicle inner side is thicker than the belt end side on the vehicle outer side when the vehicle is mounted. Yes. In the pneumatic tire described in Patent Document 1, in Invention Example 4, the tan δ (60 [° C.]) of the rubber layer on the vehicle inner side when the vehicle is mounted is smaller than that on the vehicle outer side.

JP 2007-161142 A

  The pneumatic tire described in Patent Literature 1 described above is formed such that the belt end side on the vehicle inner side is thicker than the belt end side on the vehicle outer side when the vehicle is mounted, and the tan δ (60 [° C.]) is smaller than the outside of the vehicle, so that durability is improved.

  However, if the belt end portion on the vehicle inner side is thicker than the belt end portion on the vehicle outer side when the vehicle is mounted, the rigidity of the belt end portion on the vehicle outer side and the vehicle inner side when the tire is mounted is caused by the carcass. Inflation profiles tend to be different. For this reason, there is a possibility that uneven wear may occur in the shoulder portion.

  By the way, in recent years, there is a high demand for pneumatic tires for low-floor low-flat single mounting in which the vehicle floor is lowered with a low flatness (for example, flatness 55%), and the above-described problems due to heat generation and heat dissipation are prominent. .

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can improve belt durability, ensuring the partial wear resistance of a shoulder part.

  In order to solve the above-described problems and achieve the object, the pneumatic tire of the present invention has a cord disposed at a predetermined angle with respect to the tire circumferential direction on the outer side in the tire radial direction of the carcass layer of the tread portion. A belt layer including at least a pair of cross belts is disposed, and a belt cushion rubber provided between the carcass layer and the belt layer at both ends in the tire width direction of the belt layer, and between the cross belts A pneumatic tire comprising: a belt edge cushion rubber provided on the belt layer; and a sheet-like edge cover rubber provided from the outer side in the tire radial direction of the belt layer to the outer side in the tire width direction of the belt layer. The belt edge cushion rubber and the edge cover rubber have a tire radial dimension in the meridional section. Loss tangent measured at 60 [° C.] on one side of the tire width direction with respect to at least one of the belt cushion rubber, the belt edge cushion rubber, and the edge cover rubber. A tan δ is formed smaller than the other side in the tire width direction, and a belt edge reinforcing layer that covers the outer side in the tire radial direction of the edge cover rubber is provided only on one side in the tire width direction.

  According to this pneumatic tire, the loss tangent tan δ in at least one of the belt cushion rubber, the belt edge cushion rubber, and the edge cover rubber is determined from the other side in the tire width direction at the shoulder portion that is the outer side in the tire width direction. Since one side is made smaller, one side of the tire width direction is reduced in heat generation, so that the belt durability of the belt layer can be improved. In addition, by providing a belt edge reinforcing layer only on one side in the tire width direction, it is possible to prevent uneven wear resistance from being lowered due to lower rigidity of the shoulder due to low heat generation and to ensure the uneven wear resistance. Can do.

  In the pneumatic tire of the present invention, the belt cushion rubber has a loss tangent tan δ measured at 60 [° C.] of 0.02 or more and 0.06 or less, and one side and the other side of the tire width direction. The belt edge cushion rubber and the edge cover rubber have a loss tangent tan δ measured at 60 [° C.] of 0.08 or more and 0.16 or less, and the tire width. The ratio between one side of the direction and the other side is set to be 1/2 or more and less than 1.

  Since belt edge cushion rubber and edge cover rubber absorb the movement of the end of the cross belt in the tire width direction, it is necessary to ensure elongation at break. However, excessively low tan δ reduces the elongation at break. I will let you. According to this pneumatic tire, by appropriately defining the range of the loss tangent tan δ of the belt cushion rubber, the belt edge cushion rubber, and the edge cover rubber on one side in the tire width direction, it is possible to prevent a decrease in breaking elongation and Elongation can be secured.

  In the pneumatic tire of the present invention, a circumferential main groove extending in the tire circumferential direction is formed on the tread surface of the tread portion, and the tire width direction of the circumferential main groove on the outermost side in the tire width direction is formed. The inner edge in the tire width direction of the belt edge reinforcing layer is disposed in the range of 0 [mm] to 10 [mm] on the outer side in the tire width direction with respect to the normal passing through the outer edge, and the tire width of the tread portion The outer edge in the tire width direction of the belt edge reinforcing layer is arranged in a range of ± 5 [mm] in the tire width direction with respect to the normal passing through the direction outer edge.

  When the inner edge in the tire width direction of the belt edge reinforcing layer is disposed within a range of 0 [mm] or more on the outer side in the tire width direction with respect to the normal passing through the outer edge in the tire width direction of the circumferential main groove, Contributes to improving the rigidity of the shoulder. On the other hand, the inner edge in the tire width direction of the belt edge reinforcing layer is disposed within a range of 10 mm or less on the outer side in the tire width direction with respect to the normal passing through the outer edge in the tire width direction of the circumferential main groove. And the effect of the rigidity improvement of a shoulder part is acquired notably. Further, when the outer edge of the belt edge reinforcing layer in the tire width direction is disposed within a range of 5 mm or less on the inner side in the tire width direction with respect to the normal passing through the outer edge in the tire width direction of the tread portion, The effect of improving the rigidity of the shoulder portion is remarkably obtained. When the outer edge in the tire width direction of the belt edge reinforcing layer is disposed within a range of 5 mm or less on the outer side in the tire width direction with respect to the normal passing through the outer edge in the tire width direction of the tread portion, Occurrence of failure (for example, separation) of a part is suppressed. Therefore, according to this pneumatic tire, it is possible to prevent a decrease in uneven wear resistance accompanying a decrease in rigidity of the shoulder portion due to low heat generation, and to obtain the effect of ensuring the uneven wear resistance.

  In the pneumatic tire according to the present invention, the belt edge reinforcing layer has a wire angle with respect to a tire circumferential direction larger than a wire angle with respect to the tire circumferential direction of the cross belt.

  If the wire angle of the belt edge reinforcing layer is larger than that of the cross belt, the tagging effect is not increased more than necessary, so that the occurrence of a belt end failure (for example, separation) is suppressed. Therefore, according to this pneumatic tire, it is possible to prevent a decrease in uneven wear resistance accompanying a decrease in rigidity of the shoulder portion due to low heat generation, and to obtain the effect of ensuring the uneven wear resistance.

  The pneumatic tire of the present invention is characterized in that the belt edge reinforcing layer has a wire diameter equal to or smaller than the smallest wire diameter of the belt layer.

  When the wire diameter of the belt edge reinforcing layer is set to be equal to or smaller than the smallest wire diameter of the belt layer, the tagging effect is not increased more than necessary, so that occurrence of failure (for example, separation) of the belt end is suppressed. Therefore, according to this pneumatic tire, it is possible to prevent a decrease in uneven wear resistance accompanying a decrease in rigidity of the shoulder portion due to low heat generation, and to obtain the effect of ensuring the uneven wear resistance.

  In the pneumatic tire of the present invention, the belt edge reinforcing layer has a wire diameter × number of ends that is equal to or less than the smallest wire diameter × end number of the belt layer.

  By reducing the tension load on the belt edge reinforcing layer, the occurrence of failure (for example, separation) at the end of the belt edge reinforcing layer is suppressed. Therefore, according to this pneumatic tire, it is possible to prevent a decrease in uneven wear resistance accompanying a decrease in rigidity of the shoulder portion due to low heat generation, and to obtain the effect of ensuring the uneven wear resistance.

  The pneumatic tire of the present invention is a heavy-duty single-equipped tire having a cross-sectional width of 355 [mm] or more, an oblateness of 55 [%] or less, and a mounting rim diameter of 17.5 [inch] or more. And

  Heavy load single tires have a large load load per pneumatic tire, so the tires generate a lot of heat, and depending on the running conditions of the vehicle being mounted, heat dissipation is possible either inside the vehicle or outside the vehicle. It tends to be damaged, and separation tends to occur at the belt end on the side with poor heat dissipation. For this reason, by attaching to the vehicle the side with poor heat dissipation as one side in the tire width direction, it is possible to prevent the uneven wear resistance from decreasing due to the reduced rigidity of the shoulder due to low heat generation. The effect to ensure is acquired. Therefore, by applying a single tire for heavy load as an application target, it is possible to prevent a decrease in uneven wear resistance accompanying a decrease in rigidity of the shoulder due to low heat generation, and to obtain a remarkable effect of ensuring the uneven wear resistance. it can.

  Further, when the pneumatic tire of the present invention is mounted on a vehicle, the orientation with respect to the inside and outside of the vehicle is specified, one side of the tire width direction is the vehicle inside, and the other of the tire width direction is The side is outside the vehicle.

  In particular, since the heat dissipation of brake heat and engine heat is worse on the inner side of the vehicle when the vehicle is mounted than on the outer side of the vehicle, separation tends to occur at the belt end on the inner side of the vehicle. Therefore, by setting one side of the tire width direction as the vehicle inner side and the other side of the tire width direction as the vehicle outer side, it is possible to prevent a decrease in uneven wear resistance due to a reduction in rigidity of the shoulder portion due to low heat generation. The effect of ensuring uneven wear resistance can be remarkably obtained.

  The pneumatic tire according to the present invention can improve belt durability while ensuring uneven wear resistance of the shoulder portion.

FIG. 1 is a partially cut meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 3 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.

  FIG. 1 is a partially cut meridian cross-sectional view of a pneumatic tire according to the present embodiment. 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. Means the side away from the rotation axis in the tire radial direction. Further, the tire circumferential direction refers to a direction around the rotation axis as a central axis. Further, 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 C (tire equator line) in the tire width direction, and the outer side in the tire width direction means the tire width direction. Is the side away from the tire equatorial plane C. The tire equator plane C is a plane that is orthogonal to the rotation axis and passes through the center of the tire width of the pneumatic tire 1. The tire width is the width in the tire width direction between the portions located outside in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane C in the tire width direction. 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. In the meridional section (FIG. 1) when the pneumatic tire 1 is cut on a plane passing through the rotation axis of the pneumatic tire 1, the central portion in the tire width direction is omitted, and only both outer portions in the tire width direction are omitted. Indicates.

  As shown in FIG. 1, the pneumatic tire 1 includes a tread portion 2, shoulder portions 3 on both sides of the tread portion 2, sidewall portions 4 and bead portions (not shown) sequentially continuing from the shoulder portions 3. It is configured. Further, the pneumatic tire 1 has a carcass layer 6 and a belt layer 7.

  The tread portion 2 is exposed to the outside of the pneumatic tire 1, and the surface thereof is the contour of the pneumatic tire 1. A tread surface 21 is formed on the outer peripheral surface of the tread portion 2, that is, on the tread surface that contacts the road surface during traveling. The tread surface 21 is formed with a plurality of circumferential main grooves 22 extending in the tire circumferential direction and a plurality of ribs 23 forming a plurality of land portions defined by the circumferential main grooves 22.

  The shoulder portion 3 is a portion on both outer sides in the tire width direction of the tread portion 2. The sidewall portions 4 are exposed on both outer sides in the tire width direction of the pneumatic tire 1. Although not shown in the figure, the bead portion is formed by folding a bead core, which is a steel wire, into a ring shape, and the carcass layer 6 being folded back outward in the tire width direction at the position of the bead core. And a bead filler disposed in the open space.

  In the tire width direction, the carcass layer 6 continuously straddles the tread portion 2, both sidewall portions 4, and both bead portions, and both side ends in the tire width direction are wound back around the pair of bead portions. The skeleton of the tire is configured by being toroidally wound in the circumferential direction. The carcass layer 6 is a wire formed of steel covered with a rubber material. A plurality of wires 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 wire in the carcass layer 6 with respect to the tire equator line C (tire circumferential direction) 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 layer 6 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 7 is provided on the outer side in the tire radial direction than the carcass layer 6 in the tread portion 2. The belt layer 7 is a wire formed of steel covered with rubber, and covers the carcass layer 6 along the tire circumferential direction. In the present embodiment, the belt layer 7 includes a first belt 71, a second belt 72, a third belt 73, a fourth belt 74, and a fifth belt 75 from the inner side in the tire radial direction of the carcass layer 6 toward the outer side in the tire radial direction. It has a five-layer structure laminated in this order.

  The No. 2 belt 72 and the No. 4 belt 74 are arranged so that the wire covered with rubber has an angle of 10 [°] or more and 30 [°] or less with respect to the tire circumferential direction, that is, the tire equator line C. ing. In addition, the second belt 72 and the fourth belt 74 form a cross belt in which wires that form an angle with respect to the tire circumferential direction are arranged to cross each other between the stacked belts.

  The first belt 71 is a so-called high angle in which the wire covered with rubber is disposed with an angle of 45 [°] or more and 90 [°] or less with respect to the tire circumferential direction, that is, the tire equator line C. Has a belt. The first belt 71 is formed to have a smaller size in the tire width direction than a belt (second belt 72 in the present embodiment) having a large size in the tire width direction in the crossing belt.

  The third belt 73 is a so-called tire circumference in which a wire covered with rubber is disposed with an angle of 0 [°] or more and 5 [°] or less with respect to the tire circumferential direction, that is, the tire equator line C. The circumferential reinforcing layer is substantially 0 [°] with respect to the direction. The third belt 73 is formed to have a smaller dimension in the tire width direction than the second belt 72 and the fourth belt 74 which are crossing belts. Although the circumferential reinforcing layer is described as the third belt 73 between the cross belts (second belt 72 and fourth belt 74), the outer side of the cross belt in the tire radial direction or the inner side of the cross belt in the tire radial direction. May be arranged.

  The fifth belt 75 is a so-called protective belt in which a wire covered with rubber is disposed with an angle of 10 [°] or more and 30 [°] or less with respect to the tire circumferential direction, that is, the tire equator line C. I am doing. The fifth belt 75 is formed to have a smaller dimension in the tire width direction than the second belt 72 and the fourth belt 74 which are cross belts.

Further, rubber compositions 8 are disposed at both ends of the belt layer 7 in the tire width direction. The rubber composition 8 includes a belt cushion rubber 81, a belt edge cushion rubber 82, and an edge cover rubber 83. The belt cushion rubber 81, the belt edge cushion rubber 82, and the edge cover rubber 83 have the same dimension (gauge) and cross-sectional area in the tire radial direction in the meridional section, and are configured equally on the outer sides in the tire width direction. Note that “equivalent” means that the belt cushion rubber 81, the belt edge cushion rubber 82, and the edge cover rubber 83 have equivalent functions on the outer sides in the tire width direction. It is assumed that the difference in dimension in the tire radial direction in the cross section includes a range of ± 1.0 [mm] with respect to 0 [mm], and the difference in cross-sectional area is ± 0.5 with respect to 0 [cm ² ]. The range of [cm ² ] is included.

  The belt cushion rubber 81 is provided between the carcass layer 6 and the belt layer 7. In the present embodiment, the belt cushion rubber 81 is provided between the carcass layer 6 and the end of the first belt 71 in the tire width direction and the end of the second belt 72 in the tire width direction.

  The belt edge cushion rubber 82 is provided between the second belt 72 and the fourth belt 74 which are crossing belts. In the present embodiment, the belt edge cushion rubber 82 is provided so as to reach the end in the tire width direction of the third belt 73 disposed between the second belt 72 and the fourth belt 74.

  The edge cover rubber 83 is formed in a sheet shape, and is provided from the outer side in the tire radial direction of the belt layer 7 to the outer side in the tire width direction of the belt layer 7. In the present embodiment, the edge cover rubber 83 extends from the position in the tire width direction end of the No. 5 belt 75 to the tire width direction end portion of the No. 2 belt 72 that is an intersecting belt, and the tire width direction end of the belt edge cushion rubber 82. The belt 4 is provided so as to cover the end of the belt No. 4 in the tire width direction and a part of the belt cushion rubber 81.

  In the pneumatic tire 1 of the present embodiment, at least one of the belt cushion rubber 81, the belt edge cushion rubber 82, and the edge cover rubber 83 was measured at 60 [° C.] on one side in the tire width direction. The loss tangent tan δ is formed smaller than the other side in the tire width direction. Further, the pneumatic tire 1 includes a belt edge reinforcing layer 9 that covers the outer side in the tire radial direction of the edge cover rubber 83 only on one side in the tire width direction. The loss tangent tan δ here is a frequency 20 [Hz], initial strain 10 [%], dynamic strain ± 2 [%], temperature 60 [° C.] using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho). The value when measured under the conditions.

  In the present embodiment, the belt edge reinforcing layer 9 includes an end portion in the tire width direction of the fifth belt 75 and is provided so as to cover an outer side in the tire radial direction of the edge cover rubber 83. The belt edge reinforcing layer 9 is a steel wire covered with rubber, and the wire is 45 [°] or more and 90 [°] with respect to the tire circumferential direction, that is, the tire equator line C. They are arranged with the following angles.

  According to this pneumatic tire 1, since the loss tangent tan δ of the rubber composition 8 on one side in the tire width direction is smaller than that on the other side in the shoulder portion 3 that is the outer side in the tire width direction, Since the side heat generation is reduced, the belt durability of the belt layer 7 can be improved. Moreover, by providing the belt edge reinforcing layer 9 only on one side in the tire width direction, it is possible to prevent the uneven wear resistance from being lowered due to the reduced rigidity of the shoulder portion 3 due to low heat generation and to ensure the uneven wear resistance. It becomes possible to do. In addition, in the vehicle inner side at the time of vehicle mounting | wearing, the heat dissipation of brake heat or engine heat is bad compared with the vehicle outer side, and when this is remarkable, the vehicle inner side is set to one side in the tire width direction. On the other hand, on the outside of the vehicle when the vehicle is mounted, the road surface temperature is high and the heat radiation is poor due to sunshine compared to the inside of the vehicle. When this is significant, the outside of the vehicle is set to one side in the tire width direction.

  In the pneumatic tire 1 of the present embodiment, the belt cushion rubber 81 has a loss tangent tan δ measured at 60 [° C.] of 0.02 or more and 0.06 or less, and one side in the tire width direction. The ratio to the other side (one side / other side) is 1/3 or more and less than 1. Further, the belt edge cushion rubber 82 and the edge cover rubber 83 have a loss tangent tan δ measured at 60 [° C.] of 0.08 or more and 0.16 or less and between one side and the other side in the tire width direction. The ratio (one side / other side) is ½ or more and less than one.

  Since the belt edge cushion rubber 82 and the edge cover rubber 83 have a role of absorbing the movement of the end portions in the tire width direction of the cross belts (second belt 72 and fourth belt 74), it is necessary to ensure elongation at break. However, excessively low tan δ reduces the elongation at break. According to this pneumatic tire 1, by appropriately defining the ranges of the loss tangent tan δ of the belt cushion rubber 81, the belt edge cushion rubber 82, and the edge cover rubber 83 on one side in the tire width direction, the elongation at break is reduced. It is possible to prevent and ensure the elongation at break.

  Further, in the pneumatic tire 1 of the present embodiment, a circumferential main groove 22 extending in the tire circumferential direction is formed on the tread surface 21 of the tread portion 2, and the outer circumferential main groove in the tire width direction is the outermost. The inner edge in the tire width direction of the belt edge reinforcing layer 9 is arranged in a range S1 of 0 [mm] or more and 10 [mm] or less on the outer side in the tire width direction with respect to the normal line L1 passing through the 22 outer edges 22a in the tire width direction. ing. Further, the outer edge in the tire width direction of the belt edge reinforcing layer 9 is arranged in a range S2 of ± 5 [mm] in the tire width direction with respect to the normal line L2 passing through the outer edge 2a in the tire width direction of the tread portion 2. .

  If the inner edge in the tire width direction of the belt edge reinforcing layer 9 is disposed within the range S1 of 0 [mm] or more on the outer side in the tire width direction with respect to the normal line L1, it contributes to the improvement in the rigidity of the shoulder portion 3. On the other hand, when the inner edge in the tire width direction of the belt edge reinforcing layer 9 is disposed within the range S1 of 10 [mm] or less on the outer side in the tire width direction with respect to the normal L1, the effect of improving the rigidity of the shoulder portion 3 is achieved. Is remarkably obtained. Further, when the outer edge of the belt edge reinforcing layer 9 in the tire width direction is disposed in the range S2 of 5 [mm] or less on the inner side in the tire width direction with respect to the normal L2, the effect of improving the rigidity of the shoulder portion 3 is achieved. Is remarkably obtained. If the outer edge in the tire width direction of the belt edge reinforcing layer 9 is disposed within a range S2 of 5 [mm] or less on the outer side in the tire width direction with respect to the normal L2, the belt end failure (for example, separation) Suppresses the occurrence of Therefore, according to this pneumatic tire 1, it is possible to prevent a decrease in uneven wear resistance due to a decrease in rigidity of the shoulder portion 3 due to low heat generation, and to obtain a remarkable effect of ensuring the uneven wear resistance. .

  Further, in the pneumatic tire 1 of the present embodiment, the belt edge reinforcing layer 9 has a wire angle with respect to the tire circumferential direction that is greater than a wire angle with respect to the tire circumferential direction of the cross belts (second belt 72 and fourth belt 74). large.

  If the wire angle of the belt edge reinforcing layer 9 is larger than the cross belt (No. 2 belt 72 and No. 4 belt 74), the tagging effect will not increase more than necessary, so that the belt end failure (for example, separation) is suppressed. Is done. Therefore, according to this pneumatic tire 1, it is possible to prevent a decrease in uneven wear resistance due to a decrease in rigidity of the shoulder portion 3 due to low heat generation, and to obtain a remarkable effect of ensuring the uneven wear resistance. .

  Further, in the pneumatic tire 1 of the present embodiment, the belt edge reinforcing layer 9 has a wire diameter equal to or smaller than the smallest wire diameter of the belt layer 7. In addition, a wire diameter means the outer diameter of the whole twisted, when a strand is twisted together.

  If the wire diameter of the belt edge reinforcing layer 9 is less than or equal to the smallest wire diameter of the belt layer 7 (for example, No. 1 belt 71 or No. 5 belt 75), the tagging effect does not increase more than necessary. For example, the occurrence of separation is suppressed. Therefore, according to this pneumatic tire 1, it is possible to prevent a decrease in uneven wear resistance due to a decrease in rigidity of the shoulder portion 3 due to low heat generation, and to obtain a remarkable effect of ensuring the uneven wear resistance. .

  Further, in the pneumatic tire 1 of the present embodiment, the belt edge reinforcing layer 9 has a wire diameter × number of ends [lines / 50 mm], but the smallest wire diameter of the belt layer 7 × number of ends (for example, No. 1 belt). 71 or No. 5 belt 75) [pieces / 50 mm] or less.

  By reducing the tension load of the belt edge reinforcing layer 9, the occurrence of a failure (for example, separation) at the end of the belt edge reinforcing layer 9 is suppressed. Therefore, according to this pneumatic tire 1, it is possible to prevent a decrease in uneven wear resistance due to a decrease in rigidity of the shoulder portion 3 due to low heat generation, and to obtain a remarkable effect of ensuring the uneven wear resistance. .

  Further, the pneumatic tire 1 of the present embodiment is a single tire for heavy loads having a cross-sectional width of 355 [mm] or more, an oblateness of 55 [%] or less, and a mounting rim diameter of 17.5 [inch] or more. .

  Here, the flatness ratio represents the tire height with respect to the total width in the tire width direction as a ratio. The total width in the tire width direction is the widest portion in the tire width direction in the pneumatic tire 1, and the distance between the outermost portions in the tire width direction among the sidewall portions 4 at both ends, that is, a pair of sidewall portions 4 is the distance between the parts farthest from the tire equatorial plane C. The tire height is the tire cross-sectional height along the tire radial direction from the inner end (rim base position) in the tire radial direction of the bead portion to the tread surface 21 (crown center) on the outermost side in the tire radial direction. The cross-sectional width is a distance in the tire width direction excluding patterns and characters on the tire side surface from the total width in the tire width direction. The mounting rim is a rim (regular rim) suitable for effectively demonstrating the performance of the tire. The “standard rim” defined in JATMA, the “Design Rim” defined in TRA, or the ETRTO “Measuring Rim”.

  Since the heavy load single-equipped tire has a large load load per pneumatic tire, the heat generation of the tire increases. Depending on the running condition of the vehicle to be mounted, heat dissipation is performed either on the vehicle inside or on the vehicle outside. Tends to be damaged, and separation tends to occur at the belt end on the side with poor heat dissipation. For this reason, by attaching to the vehicle the side with poor heat dissipation as one side in the tire width direction, it is possible to prevent a decrease in uneven wear resistance due to a decrease in rigidity of the shoulder portion 3 due to low heat generation, and the uneven wear resistance. The effect of ensuring is obtained. Therefore, by applying a single tire for heavy load to be applied, it is possible to prevent a decrease in uneven wear resistance associated with a decrease in rigidity of the shoulder portion 3 due to low heat generation, and to obtain a remarkable effect of ensuring the uneven wear resistance. Is possible.

  Further, when the pneumatic tire 1 of the present embodiment is mounted on a vehicle, the orientation with respect to the inside and outside of the vehicle is specified, one side of the tire width direction is the vehicle inside, and the tire width The other side of the direction is the outside of the vehicle.

  Here, the designation of the direction is not clearly shown in the drawing, but is indicated by, for example, an index provided on a sidewall portion which is a tire side surface.

  In particular, since the heat dissipation of brake heat and engine heat is worse on the inner side of the vehicle when the vehicle is mounted than on the outer side of the vehicle, separation tends to occur at the belt end on the inner side of the vehicle. Therefore, by setting one side of the tire width direction as the vehicle inner side and the other side of the tire width direction as the vehicle outer side, it is possible to prevent a decrease in uneven wear resistance accompanying a reduction in rigidity of the shoulder portion 3 due to low heat generation, The effect of ensuring the uneven wear resistance can be remarkably obtained.

  In the present embodiment, performance tests on belt durability (separation resistance) and uneven wear resistance were performed on a plurality of types of pneumatic tires having different conditions (see FIGS. 2 and 3).

  In this performance test, a pneumatic tire (see FIG. 2) with a tire size of 445 / 50R22.5 and a pneumatic tire with a tire size of 295 / 75R22.5 (see FIG. 3) are assembled to a regular rim as test tires. Used by filling the internal pressure. The regular rim here refers to “standard rim” defined in JATMA, “Design Rim” defined in TRA, or “Measuring Rim” defined in ETRTO. The normal internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO.

  In the belt durability performance test, the test tire was tested with a drum-type durability performance tester at a running speed of 45 [km / h] per hour from the normal load to 10 [normal load] every step (every 24 hours). %], And the distance traveled until the tire breaks is measured. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation shows that the greater the index, the longer the travel distance and the better the belt durability.

  In the case of the above test tire having a tire size of 445 / 50R22.5, the performance test of uneven wear resistance is 4 for each of the 6 × 4 drive shaft and the two trailer shafts of the heavy load test vehicle having a shaft weight of 10 [t]. In the case of the above-mentioned test tires with 8 tires installed and one tire size of 295 / 75R22.5, the 6 × 4 drive shaft and the 2 trailer shafts of the heavy duty test vehicle with the axle load of 10 [t] are used. Eight each (16 mounted), and the difference in the amount of wear on the tread surface between the shoulder portion inside the vehicle and the center portion (near the tire equator line) after traveling 100,000 km is measured. Then, the reciprocals of the measurement results are compared, and index evaluation is performed with the conventional example as a reference (100). This evaluation indicates that uneven wear resistance is secured when the index is 95 or more.

  As shown in FIG. 2, the pneumatic tire of the conventional example has a belt layer of No. 1 belt to No. 5 belt, and the belt cushion rubber, belt edge cushion rubber, and edge cover rubber are 60 [° C.]. The measured loss tangent tan δ is the same between the vehicle inner side and the vehicle outer side, and no belt edge reinforcing layer is provided. Further, the pneumatic tire of Comparative Example 1 has a belt layer of No. 1 belt to No. 5 belt, and loss tangent measured at 60 [° C.] of belt cushion rubber, belt edge cushion rubber, and edge cover rubber. Tan δ is the same between the vehicle inner side and the vehicle outer side, and has a belt edge reinforcing layer. In the pneumatic tire of Comparative Example 2, the loss tangent tan δ measured at 60 [° C.] of the belt cushion rubber, the belt edge cushion rubber, and the edge cover rubber is reduced on the vehicle inner side, but the belt edge reinforcing layer Does not have.

  As shown in FIG. 2, in the pneumatic tires of Examples 1 to 7, the belt layer has No. 1 belt to No. 5 belt, and belt cushion rubber, belt edge cushion rubber, and edge cover rubber are used. The loss tangent tan δ measured at 60 [° C.] is reduced inside the vehicle and has a belt edge reinforcing layer. In the pneumatic tires of Example 2 and Example 3, the loss tangent tan δ of the belt cushion rubber is set to 0.02 or more and 0.06 or less, and the ratio between the vehicle inner side and the vehicle outer side in the tire width direction is 1/3. The loss tangent tan δ of the belt edge cushion rubber and the edge cover rubber is 0.08 or more and 0.16 or less, and the ratio between the vehicle inner side and the vehicle outer side in the tire width direction is 1/2 or more and 1 Less than. Further, in the pneumatic tire except Example 4, the inner edge position in the tire width direction and the outer edge position in the tire width direction of the belt edge reinforcing layer are within the specified range. In the pneumatic tire except Example 1, the wire angle of the belt edge reinforcing layer is made larger than the wire angle of the cross belt. In the pneumatic tires of Example 6 and Example 7, the belt diameter of the belt edge reinforcing layer × the number of ends is set to be equal to or less than the smallest wire diameter of the belt layer × the number of ends.

  As shown in FIG. 3, in the pneumatic tires of Examples 8 to 10, the belt layer has No. 1 belt to No. 4 belt, and the No. 2 belt and No. 3 belt are crossed belts. Loss tangent tan δ measured at 60 [° C.] of rubber, belt edge cushion rubber, and edge cover rubber is reduced inside the vehicle and has a belt edge reinforcing layer. In the pneumatic tires of Example 9 and Example 10, the loss tangent tan δ of the belt cushion rubber is set to 0.02 or more and 0.06 or less, and the ratio between the vehicle inner side and the vehicle outer side in the tire width direction is 1/3. The above is less than 1. Further, in the pneumatic tires of Example 9 and Example 10, the loss tangent tan δ of the belt edge cushion rubber and the edge cover rubber is set to 0.08 or more and 0.16 or less, and between the vehicle inner side and the vehicle outer side in the tire width direction. The ratio is set to 1/2 or more and less than 1. In the pneumatic tires of Example 9 and Example 10, the inner edge position in the tire width direction and the outer edge position in the tire width direction of the belt edge reinforcing layer are within the specified range. Furthermore, in the pneumatic tires of Example 9 and Example 10, the wire angle of the belt edge reinforcing layer is made larger than the wire angle of the cross belt. In the pneumatic tire of Example 10, the wire diameter of the belt edge reinforcing layer × the number of ends is set to be equal to or smaller than the smallest wire diameter of the belt layer × the number of ends.

  As shown in the test results of FIGS. 2 and 3, it can be seen that the pneumatic tires of Examples 1 to 10 ensure the uneven wear resistance of the shoulder portion and improve the belt durability.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 2a Tire width direction outer edge 21 Tread surface 22 Circumferential main groove 22a Tire width direction outer edge 23 Rib 3 Shoulder part 4 Side wall part 6 Carcass layer 7 Belt layer 71 1st belt 72 2nd belt (Cross belt)
73 No. 3 belt 74 No. 4 belt (cross belt)
75 No. 5 belt 8 Rubber composition 81 Belt cushion rubber 82 Belt edge cushion rubber 83 Edge cover rubber 9 Belt edge reinforcement layer C Tire equator surface (tire equator line)
L1 Normal passing through the outer edge in the tire width direction of the circumferential main groove L2 Normal passing through the outer edge in the tire width direction of the tread portion

Claims (8)

A belt layer including at least a pair of intersecting belts having cords arranged at a predetermined angle with respect to the tire circumferential direction is arranged outside the tire radial direction of the carcass layer of the tread portion, and the belt layer in the tire width direction is arranged. At both ends, a belt cushion rubber provided between the carcass layer and the belt layer, a belt edge cushion rubber provided between the intersecting belts, and the belt layer from the outer side in the tire radial direction of the belt layer In a pneumatic tire provided with a sheet-like edge cover rubber provided to the outside in the tire width direction,
The belt cushion rubber, the belt edge cushion rubber, and the edge cover rubber are configured to have the same dimension in the tire radial direction in the meridian cross section on each outer side in the tire width direction, and the belt cushion rubber and the belt edge cushion rubber. For at least one of the edge cover rubbers, a loss tangent tan δ measured at 60 [° C.] on one side in the tire width direction is formed smaller than the other side in the tire width direction. A pneumatic tire comprising a belt edge reinforcing layer that covers the outer side in the tire radial direction of the edge cover rubber only on the side.   The belt cushion rubber has a loss tangent tan δ measured at 60 [° C.] of 0.02 or more and 0.06 or less, and a ratio of one side of the tire width direction to the other side of 1/3 or more and less than 1. The belt edge cushion rubber and the edge cover rubber have a loss tangent tan δ measured at 60 [° C.] of 0.08 or more and 0.16 or less, and one side and the other side in the tire width direction. The pneumatic tire according to claim 1, wherein the ratio of ½ is less than 1.   A circumferential main groove extending in the tire circumferential direction is formed on the tread surface of the tread portion, and with respect to a normal passing through the tire width direction outer edge of the circumferential main groove on the outermost side in the tire width direction, With respect to the normal line in which the inner edge in the tire width direction of the belt edge reinforcing layer is disposed in the range of 0 [mm] to 10 [mm] on the outer side in the tire width direction and passes through the outer edge in the tire width direction of the tread portion The pneumatic tire according to claim 1 or 2, wherein an outer end in the tire width direction of the belt edge reinforcing layer is arranged in a range of ± 5 [mm] in the tire width direction.   The pneumatic tire according to claim 1, wherein the belt edge reinforcing layer has a wire angle with respect to a tire circumferential direction larger than a wire angle with respect to the tire circumferential direction of the cross belt.   The pneumatic tire according to any one of claims 1 to 4, wherein the belt edge reinforcing layer has a wire diameter equal to or smaller than a smallest wire diameter of the belt layer.   The pneumatic tire according to claim 1, wherein the belt edge reinforcing layer has a wire diameter × number of ends that is equal to or less than a smallest wire diameter of the belt layer × number of ends.   7. The heavy load single-mounted tire having a cross-sectional width of 355 [mm] or more, a flatness of 55 [%] or less, and a mounting rim diameter of 17.5 [inch] or more. The pneumatic tire according to one.   When mounted on a vehicle, the direction with respect to the inside and outside of the vehicle is specified, one side of the tire width direction is the vehicle inside, and the other side of the tire width direction is the vehicle outside The pneumatic tire according to any one of claims 1 to 7.

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