JP2013216113A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve wear resistance of a tread surface.SOLUTION: An intersection of extensions of a shoulder-side arc 21b and a side section arc 21d of a tread surface 21 is determined as a reference point P. An angle θ between a straight line A that connects the reference point with a center crown CC for an aspect ratio β, and a straight line B in the tire width direction, passing through the center crown, satisfies 0.02xβ+0.4≤θ≤0.035xβ+1.7. A relationship between a radius of curvature Rc of a central arc 21a and a radius of curvature Rs of the shoulder-side arc satisfies 12≤Rc/Rs≤30. A relationship between a reference development width L and a tread development width TDW from a tire equatorial plane CL to an inner end in the tire width direction of the shoulder-side arc satisfies 0.2≤L/(TDW/2)≤0.7. A belt reinforcement layer 8 that is formed radially outside of at least an outer end in both-tire width direction of a belt layer 7 and has a cord arranged along the tire peripheral direction is disposed within 10% of the tread development width TDW/2 on both lateral sides from a position where a normal line S of the tread surface passing through the reference point P crosses.

Description

  The present invention relates to a pneumatic tire, and in particular, when the use air pressure is increased to reduce rolling resistance for the purpose of reducing fuel consumption, the wear life is deteriorated due to an increase in contact pressure accompanying an increase in diameter growth in the center region. It relates to an improved pneumatic tire.

  Conventionally, a pneumatic tire is known in which the curvature of a profile along a tire width direction of a tread surface is made close to a straight line (for example, see Patent Document 1). In this pneumatic tire, the tread surface is formed of an arc having a plurality of different radii of curvature including at least a central arc positioned at the center in the tire width direction and a shoulder-side arc positioned at the outermost position in the tire width direction. In a pneumatic tire, a tire that extends from the outermost position in the tire width direction of the belt layer to the outer side in the tire radial direction in a cross-sectional view in the tire meridian direction with 5% of the normal internal pressure filled in the normal rim and filled with the internal pressure. The intersection between the virtual line imaginary parallel to the radial direction and the profile of the tread surface is the reference point, the intersection of the tire equator surface and the tread surface profile is the center crown, and the line connecting the reference point and the center crown The angle between the line parallel to the tire width direction is θ, the radius of curvature of the central arc is Rc, the radius of curvature of the shoulder side arc is Rs, and the tire equatorial plane When the reference developed width that is the arc length to the inner end position in the tire width direction of the shoulder side arc is L, and the tread deployed width that is the arc length of the tread surface in the tire width direction is TDW, the tread surface is 1 [°] <θ <4.5 [°], 5 <Rc / Rs <10, and 0.4 <L / (TDW / 2) <0.7.

JP 2008-307948 A

  In recent years, in order to reduce the fuel consumption of a vehicle equipped with a pneumatic tire, in order to reduce the rolling resistance of the pneumatic tire, it has been studied to increase the working air pressure. However, increasing the air pressure used increases the diameter growth on the inner side (center area) in the tire width direction, and as a result, the contact pressure on the inner side in the tire width direction increases, so that the inner side in the tire width direction of the tread surface is easily worn. Become.

  In the pneumatic tire described in Patent Document 1 described above, the wear on the inner side of the tread surface in the tire width direction tends to be improved by bringing the curvature of the profile along the tire width direction of the tread surface closer to a straight line. However, since the contact pressure on the outer side in the tire width direction (shoulder region) increases, the outer side in the tire width direction on the tread surface tends to be easily worn.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can improve the abrasion resistance of a tread surface.

  In order to solve the above-described problems and achieve the object, the pneumatic tire of the present invention includes a carcass layer and a belt layer disposed on the tread portion on the outer side in the tire radial direction of the carcass layer, In the pneumatic tire provided with a belt reinforcing layer having a cord extending along the tire circumferential direction at the outer side in the tire radial direction of at least both tire width direction outer ends of the belt layer, the tread surface of the tread portion is the center in the tire width direction. Is formed by a plurality of arcs having different radii of curvature including at least a central arc positioned at the center and a shoulder-side arc continuous to the outer side in the tire width direction of the central arc, and is incorporated into a normal rim and is 5% of the normal internal pressure. In the tire meridian direction in cross-sectional view, the imaginary extension line of the shoulder side arc and the tire width direction maximum in the tread portion A point of intersection with the virtual extension line of the side arc on the side as a reference point, a point of intersection of the tire equator plane and the profile of the tread surface as a center crown, a straight line connecting the reference point and the center crown, and The angle formed by a straight line passing through the center crown and parallel to the tire width direction is θ, the radius of curvature of the central arc is Rc, the radius of curvature of the shoulder-side arc is Rs, and the shoulder equatorial plane to the shoulder The reference development width which is the arc length to the inner end position in the tire width direction of the side arc is L, and between the points where the reference line passing through the reference point and parallel to the tire equator plane intersects the tread surface. The tread surface is 0.02 × β + 0.4 ≦ θ ≦ 0.035 × β + 1.7 when the tread development width, which is the arc length in the tire width direction, is TDW and the flatness ratio is β. 12 ≦ Rc / Rs ≦ 30, 0.2 ≦ L / (TDW / 2) ≦ 0.7, and the belt reinforcing layer has a normal line of the tread surface passing through the reference point. It is arranged at least in the range of 10% of the tread development width TDW / 2 from the crossing position on both sides in the tire width direction.

  The belt reinforcement layer is disposed at least in a range of 10 [%] of the tread development width TDW / 2 from the position where the normal line of the tread surface passing through the reference point intersects to both sides in the tire width direction. A layer is arrange | positioned so that it may protrude on the tire width direction outer side of a belt layer, and suppresses a deformation | transformation of the said part. As a result, the contact pressure on the outer side (shoulder region) in the tire width direction of the tread surface is reduced, so that local wear at the edge portion of the contact region on the outer side in the tire width direction of the tread surface can be suppressed. In addition, by providing the belt reinforcing layer, an angle θ formed by a straight line connecting the reference point and the center crown and a straight line passing through the center crown and parallel to the tire width direction is 0.02 × β + 0.4 ≦. The angle θ, which is the amount of sagging inward in the tire radial direction from the central arc to the shoulder side arc, can be further reduced so that θ ≦ 0.035 × β + 1.7. Thereby, abrasion of the center area | region of a tread surface can be improved. As a result, the wear resistance of the tread surface can be improved.

  In the pneumatic tire of the present invention, 10% of the tread deployment width TDW / 2 from the position where the normal line of the tread surface passing through the reference point intersects the belt reinforcing layer to the inner side in the tire width direction. ], The rubber gauge tsh of the tread portion, which is the shortest distance to the tread surface, satisfies 5.0 [mm] ≦ tsh ≦ 8.0 [mm], and the standard for the belt reinforcing layer The rubber gauge of the tread portion which is the shortest distance to the tread surface at a position of 10% of the tread development width TDW / 2 from the position where the normal line of the tread surface passing through the point intersects to the outside in the tire width direction tout satisfies 2.0 [mm] ≦ tout ≦ 5.0 [mm].

  By setting the rubber gauge tsh of the tread portion to 5.0 [mm] or more on the inner side in the tire width direction within the above range of the belt reinforcing layer, the wear life can be ensured, and the rubber gauge tsh of the tread portion is 8.0 [ mm] or less, an increase in tire weight that deteriorates rolling resistance can be suppressed. Further, by setting the rubber gauge tout of the tread portion to 2.0 [mm] or more on the outer side in the tire width direction in the above range of the belt reinforcing layer, damage to the tread portion can be suppressed while protecting the belt reinforcing layer. By setting the rubber gauge tout of the tread portion to 5.0 [mm] or less, the contraction force (deformation) in the tire radial direction is suppressed in the portion near the ground contact region near the outer side in the tire width direction of the above-described range of the belt reinforcing layer. In addition, since the contact pressure on the outer side (shoulder region) in the tire width direction of the tread surface is reduced, local wear on the edge portion on the outer side in the tire width direction of the tread surface can be further suppressed.

  In the pneumatic tire of the present invention, in the belt reinforcing layer, 10 [%] of the tread development width TDW / 2 from the position where the normal line of the tread surface passing through the reference point intersects to the inside in the tire width direction. The product of the stiffness coefficient [N] and the number of driven [50 / mm] per 50 [mm] of the cord on the outer side in the tire width direction from the base point is the protruding side ply stiffness coefficient Xsh [ N · line / 50 [mm]], and the product of the stiffness coefficient [N] and the number of driven wires per 50 [mm] [line / 50 [mm]] on the inner cord in the tire width direction from the base point When the ply rigidity coefficient Xce [N · piece / 50 [mm]] is satisfied, 0.40 ≦ Xce / Xsh ≦ 0.90 and 15 ≦ Xsh ≦ 40 are satisfied.

  By making Xce / Xsh in the range of 0.40 or more and 0.90 or less, the rigidity in the range of the belt reinforcing layer is made a more suitable range, and it is easy to obtain the sagging amount from the desired central arc to the shoulder side arc. can do.

  In the pneumatic tire according to the present invention, the cord of the belt reinforcing layer is made of an organic fiber.

  When an organic fiber is used for the cord of the belt reinforcing layer, the rigidity per cord becomes small, and it is easy to obtain a sagging amount from the center arc to the shoulder side arc. Further, when organic fibers are used for the cord of the belt reinforcing layer, the ply rigidity can be increased by the number of driving [50 / mm] per 50 [mm] width in the tire width direction. The volume is reduced and the influence on rolling resistance can be suppressed.

  The pneumatic tire according to the present invention is characterized in that 0.55 ≦ TDW / SW ≦ 0.75 is satisfied when the tire cross-sectional width is SW.

  Even if the tread development width TDW is made relatively small by the regulation of the belt reinforcing layer and the tread surface profile, the effect of improving the wear resistance of the tread surface can be obtained, and the rolling resistance can be further reduced. However, when TDW / SW is less than 0.55, it is difficult to obtain an effect of improving the wear resistance of the tread surface. On the other hand, when TDW / SW exceeds 0.75, it is difficult to obtain an effect of reducing rolling resistance. Therefore, by setting it as the said range, the improvement effect of the abrasion resistance of a tread surface and the reduction effect of rolling resistance can be acquired notably.

  The pneumatic tire of the present invention is characterized by being applied to a pneumatic tire for passenger cars having a high internal pressure.

  In order to reduce the fuel consumption of passenger vehicles equipped with pneumatic tires, it is effective to increase the operating air pressure in order to reduce the rolling resistance of pneumatic tires. In order to increase the input, the diameter growth on the inner side in the tire width direction increases, and the contact pressure on the inner side in the tire width direction increases accordingly, so that the inner side in the tire width direction of the tread surface is easily worn. According to this pneumatic tire, in such a pneumatic tire for passenger cars having a high internal pressure, the effect of improving the wear resistance on the inner side in the tire width direction of the tread surface can be remarkably obtained.

  The pneumatic tire according to the present invention can improve the wear resistance of the tread surface.

FIG. 1 is a meridional sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a partially cut meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 3 is a partially cut meridian cross-sectional enlarged view of the pneumatic tire according to the embodiment of the present invention. FIG. 4 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 5 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 6 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 7 is a chart showing the results of the performance test of the pneumatic tire according to the example 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. FIG. 9 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 10 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 meridional sectional view of a pneumatic tire according to the present embodiment, FIG. 2 is a partially cut meridional sectional view of the pneumatic tire according to the present embodiment, and FIG. It is a partially cut meridian cross-sectional enlarged view of the pneumatic tire which concerns on a form.

  In the following description, the tire radial direction refers to a direction orthogonal to the rotational axis (not shown) of the pneumatic tire, and the tire radial inner side refers to the side toward the rotational axis in the tire radial direction, the tire radial outer side, and 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 (tire equator line) CL 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 CL. The tire equatorial plane CL is a plane that is orthogonal to the rotational axis of the pneumatic tire and passes through the center of the tire width of the pneumatic tire. The tire equator line is a line along the tire circumferential direction of the pneumatic tire on the tire equator plane CL. In the present embodiment, the same sign “CL” as that of the tire equator plane is attached to the tire equator line.

  As shown in FIG. 1, the pneumatic tire according to the present embodiment includes a tread portion 2, shoulder portions 3 on both sides thereof, and a sidewall portion 4 and a bead portion 5 that are sequentially continuous from the shoulder portions 3. Yes. The pneumatic tire includes a carcass layer 6, a belt layer 7, and a belt reinforcing layer 8.

  The tread portion 2 is made of a rubber material (tread rubber), and is exposed at the outermost side in the tire radial direction of the pneumatic tire, and the surface thereof is the contour of the pneumatic tire. 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 provided with a plurality of (four in this embodiment) main grooves 22 that are straight main grooves extending along the tire circumferential direction and parallel to the tire equator line CL. The tread surface 21 extends along the tire circumferential direction by the plurality of main grooves 22, and a plurality of rib-like land portions 23 parallel to the tire equator line CL are formed. Although not shown in the figure, the tread surface 21 is provided with a lug groove that intersects the main groove 22 in each land portion 23. The land portion 23 is divided into a plurality of portions in the tire circumferential direction by lug grooves. Further, the lug groove is formed to open to the outer side in the tire width direction on the outermost side in the tire width direction of the tread portion 2. Note that the lug groove may have either a form communicating with the main groove 22 or a form not communicating with the main groove 22.

  The shoulder portion 3 is a portion on both outer sides in the tire width direction of the tread portion 2. The sidewall portion 4 is exposed at the outermost side in the tire width direction of the pneumatic tire. The bead unit 5 includes a bead core 51 and a bead filler 52. The bead core 51 is formed by winding a bead wire, which is a steel wire, in a ring shape. The bead filler 52 is a rubber material disposed in a space formed by folding the end portion in the tire width direction of the carcass layer 6 at the position of the bead core 51.

  The carcass layer 6 is configured such that each tire width direction end portion is folded back from the tire width direction inner side to the tire width direction outer side by a pair of bead cores 51 and is wound around in a toroidal shape in the tire circumferential direction. It is. This carcass layer 6 has a 90 ° (± 5 °) angle with respect to the tire circumferential direction, and a plurality of carcass cords (not shown) arranged in the tire circumferential direction along the tire meridian direction and covered with a coat rubber. It is. The carcass cord is made of organic fibers (polyester, rayon, nylon, etc.). The carcass layer 6 is provided as at least one layer.

  The belt layer 7 has a multilayer structure in which at least two belts 71 and 72 are laminated, and is disposed on the outer side in the tire radial direction which is the outer periphery of the carcass layer 6 in the tread portion 2 and covers the carcass layer 6 in the tire circumferential direction. It is. The belts 71 and 72 are made by coating a plurality of cords (not shown) arranged in parallel at a predetermined angle (for example, 20 degrees to 30 degrees) with a coat rubber with respect to the tire circumferential direction. The cord is made of steel or organic fiber (polyester, rayon, nylon, etc.). Further, the overlapping belts 71 and 72 are arranged so that the cords intersect each other.

  The belt reinforcing layer 8 is disposed on the outer side in the tire radial direction which is the outer periphery of the belt layer 7 and covers the belt layer 7 in the tire circumferential direction. In the present embodiment, the belt reinforcing layer 8 has reinforcing layers 81 and 82 arranged in at least two layers so as to cover the outer periphery of the belt layer 7. Reinforcing layers 81 and 82 are provided with a plurality of cords 8a arranged in parallel in the tire width direction in parallel to the tire circumferential direction (including an error of 0 degree: ± 5 degrees) in the tire width direction so as to extend along the tire circumferential direction. (See FIG. 3). The cord 8a is made of steel or organic fiber (polyester, rayon, nylon, etc.). The belt reinforcement layer 8 shown in FIG. 1 is arranged so that the reinforcement layer 81 on the belt layer 7 side is formed larger in the tire width direction than the belt layer 7 so as to cover the entire belt layer 7. The outer reinforcing layer 82 is disposed only at the end portion in the tire width direction of the reinforcing layer 81 so as to cover the end portion in the tire width direction of the belt layer 7. The configuration of the belt reinforcing layer 8 is not limited to the above, and is not clearly shown in the drawing, but the reinforcing layers 81 and 82 are both formed larger in the tire width direction than the belt layer 7 and are arranged so as to cover the entire belt layer 7. Alternatively, the reinforcing layers 81 and 82 may be arranged so as to cover only the end portion of the belt layer 7 in the tire width direction. That is, the belt reinforcing layer 8 overlaps at least the end portion in the tire width direction of the belt layer 7. Further, the belt reinforcing layer 8 may be configured by any one of the reinforcing layers 81 and 82. The belt reinforcing layer 8 (reinforcing layers 81 and 82) is provided by winding a strip-like strip material (for example, a width of 10 [mm]) in the tire circumferential direction.

  In the pneumatic tire of the present embodiment, the profile of the tread surface 21 that is the surface of the tread portion 2 is formed by a plurality of arcs having different curvature radii that are convex outward in the tire radial direction. Specifically, as shown in FIG. 2, the tread surface 21 includes a central arc 21a, a shoulder-side arc 21b, a shoulder arc 21c, and a side arc 21d.

  The central arc 21a is located in the center of the tread surface 21 in the tire width direction, includes the tire equator plane CL, and is formed on both sides in the tire width direction with the tire equator plane CL as the center. The central arc 21a is formed with the largest diameter in the tire radial direction of the portion including the tire equatorial plane CL. The shoulder-side arc 21b is formed continuously outside the central arc 21a in the tire width direction. The shoulder arc 21c is formed continuously outside the shoulder arc 21b in the tire width direction. The side portion arc 21d is formed continuously outside the shoulder portion arc 21c in the tire width direction and is located on the outermost side in the tire width direction of the tread portion 2.

  Then, in an unloaded state in which a pneumatic tire is incorporated in a normal rim and filled with 5% of the normal internal pressure, the virtual extension line of the shoulder-side arc 21b is shown in a sectional view in the tire meridian direction shown in FIG. A point of intersection with a virtual extension line of the side arc 21d is defined as a reference point P. The intersection of the tire equatorial plane CL and the profile of the tread surface 21 is a center crown CC, a straight line A connecting the reference point P and the center crown CC, and a straight line passing through the center crown CC and parallel to the tire width direction. The angle formed by B is θ. Further, the radius of curvature of the central arc 21a is Rc. The radius of curvature of the shoulder-side arc 21b is Rs. Further, let L be a reference developed width that is the arc length from the tire equatorial plane CL to the inner end position in the tire width direction of the shoulder-side arc 21b. The tread developed width, which is the arc length in the tire width direction between points where a reference line passing through the reference point P and parallel to the tire equatorial plane CL intersects the tread surface 21, is defined as TDW. Also, let the flatness ratio be β.

In this case, the tread surface 21 of the pneumatic tire of the present embodiment is formed so as to satisfy the following formulas (1) to (3).
0.02 × β + 0.4 ≦ θ ≦ 0.035 × β + 1.7 (1)
12 ≦ Rc / Rs ≦ 30 (2)
0.2 ≦ L / (TDW / 2) ≦ 0.7 (3)

  Here, the regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The flatness ratio is a ratio of the tire cross section height HS to the tire cross section width. The tire cross-sectional width is the width in the tire width direction between the portions located outside the tire width direction in a no-load state in which the tire is assembled on the regular rim and filled with the normal internal pressure, that is, the tire equatorial plane in the tire width direction. It is the distance between the parts farthest from the CL, and is the width excluding the patterns and characters on the side of the tire. The tire cross-section height HS is ½ of the difference between the outer diameter and the rim diameter of the unloaded tire in which the tire is assembled on the regular rim and filled with the regular internal pressure.

  In the pneumatic tire of the present embodiment, as shown in FIGS. 2 and 3, the belt reinforcing layer 8 intersects the normal line S of the tread surface 21 (shoulder portion arc 21 c) passing through the reference point P. It is arranged at least in a range Wsh, Wout of 10% of the tread development width TDW / 2 on both sides in the tire width direction from the position Q. The belt reinforcing layer 8 may be both the reinforcing layers 81 and 82 or one of them.

  Here, the position Q of the belt reinforcing layer 8 at which the normal line S intersects is, as shown in FIG. 3, a straight line and a normal line connecting the outermost radial direction of the cord 8a of the belt reinforcing layer 8 (reinforcing layer 82). The position where S intersects.

  As described above, in the pneumatic tire according to the present embodiment, when the intersection of the extension lines of the shoulder-side arc 21b and the side arc 21d is the reference point P, the reference point P and the center crown CC The angle θ between the straight line A connecting the two and the straight line B in the tire width direction passing through the center crown CC is 0.02 × β + 0.4 ≦ θ ≦ 0.035 × β + 1.7, and the radius of curvature of the central arc 21a Rc and the radius of curvature Rs of the shoulder-side arc 21b are set to 12 ≦ Rc / Rs ≦ 30, and the reference deployment width L and the tread deployment width TDW from the tire equatorial plane CL to the inner end of the shoulder-side arc 21b in the tire width direction are 0.2 ≦ L / (TDW / 2) ≦ 0.7. Further, in the pneumatic tire according to the present embodiment, the belt reinforcing layer 8 having the cord 8a along the tire circumferential direction that is provided on the outer side in the tire radial direction of at least both outer ends in the tire width direction of the belt layer 7 has the reference point P. From the position Q where the normal line S of the tread surface 21 passing through the tire intersects in the tire width direction on both sides in the range Wsh, Wout of 10 [%] of the tread development width TDW / 2.

  According to the pneumatic tire of the present embodiment, the belt reinforcing layer 8 has a tread development width TDW / 2 of 10 at the tire width direction both sides from the position Q where the normal line S of the tread surface 21 passing through the reference point P intersects. By being disposed at least in the [%] ranges Wsh, Wout, the belt reinforcing layer 8 is disposed so as to protrude outward in the tire width direction of the belt layer 7 and suppresses deformation of the portion. As a result, the contact pressure on the outer side (shoulder region) in the tire width direction of the tread surface 21 is reduced, so that local wear on the edge portion of the contact region on the outer side in the tire width direction of the tread surface 21 can be suppressed. It becomes possible.

  Moreover, according to the pneumatic tire of the present embodiment, by providing the belt reinforcing layer 8 as described above, the straight line A connecting the reference point P and the center crown CC and the tire width passing through the center crown CC. The tire θ extends from the central arc 21a to the shoulder arc 21b so that the angle θ formed by the straight line B parallel to the direction is in the range of 0.02 × β + 0.4 ≦ θ ≦ 0.035 × β + 1.7. It is possible to make the angle θ, which is the amount of inward depression, smaller. It is preferable to reduce the angle θ in order to improve wear (center wear) on the inner side (center region) of the tread surface 21 in the tire width direction. However, if the angle θ is too small, the wear of the shoulder region of the tread surface 21 tends to deteriorate, so the above range is set.

  Further, the relationship between the radius of curvature Rc of the central arc 21a and the radius of curvature Rs of the shoulder-side arc 21b is 12 ≦ Rc / Rs ≦ 30, and the position in the tire width direction inner end of the shoulder-side arc 21b from the tire equatorial plane CL is set. The relationship between the reference developed width L that is the arc length of the central arc 21a and the tread developed width TDW is 0.2 ≦ L / (TDW / 2) ≦ 0.7. The shoulder side arc 21b is reached and the arc of the tread surface 21 is closer to a straight line. As a result, since the radial growth of the central arc 21a is suppressed, it is possible to improve the wear of the shoulder region of the tread surface 21 and the wear of the center region of the tread surface 21. That is, it becomes possible to improve the wear of the center region while suppressing the deterioration of the wear of the shoulder region.

  Specifically, when the angle θ is less than “0.02 × β + 0.4”, the amount of sagging from the central arc 21a to the shoulder-side arc 21b is too small, and the effect of suppressing wear of the shoulder region of the tread surface 21 is reduced. Decrease. On the other hand, when the angle θ exceeds “0.035 × β + 1.7”, the amount of sagging from the central arc 21a to the shoulder-side arc 21b is large, and the effect of improving the wear in the center area of the tread surface 21 is reduced. In addition, since the amount of sagging from the central arc 21a to the shoulder arc 21b is optimized by setting the angle θ in the range of 0.025 × β + 0.5 ≦ θ ≦ 0.03 × β + 1.6, the tread The effect of improving the wear of the center region of the tread surface 21 can be significantly obtained while suppressing the wear of the shoulder region of the surface 21.

  Further, when Rc / Rs is less than 12, the diameter growth of the central arc 21a cannot be sufficiently suppressed, and the contact pressure in the center area increases and it becomes difficult to improve the wear of the center area of the tread surface 21. . On the other hand, when Rc / Rs exceeds 30, the effect of suppressing the radial growth of the central arc 21a cannot be sufficiently obtained, and the effect of improving the wear in the center area of the tread surface 21 cannot be expected. In addition, by setting it as the range of 15 <= Rc / Rs <= 25, diameter growth of the center part circular arc 21a is fully suppressed, and the center area | region of the tread surface 21 is suppressed, suppressing the deterioration of the abrasion of the shoulder area of the tread surface 21. It is possible to obtain a remarkable effect of improving the wear of the steel.

  Further, even when L / (TDW / 2) is less than 0.2, the diameter growth of the central arc 21a cannot be sufficiently suppressed, and the contact pressure in the center area increases to cause wear in the center area of the tread surface 21. It becomes difficult to improve. On the other hand, even when L / (TDW / 2) exceeds 0.7, the effect of suppressing the radial growth of the central arc 21a cannot be sufficiently obtained, and the effect of improving the wear of the center region of the tread surface 21 cannot be expected. . In addition, by setting it as the range of 0.4 <= L / (TDW / 2) <= 0.5, the diameter growth of the center part circular arc 21a is fully suppressed, and the deterioration of the abrasion of the shoulder area of the tread surface 21 is suppressed. However, the effect of improving the wear of the center area of the tread surface 21 can be significantly obtained.

  As a result, according to the pneumatic tire of the present embodiment, the wear resistance of the tread surface 21 is improved by improving the wear of the center region of the tread surface 21 while suppressing the deterioration of the wear of the shoulder region of the tread surface 21. It becomes possible to improve the property.

  Here, the center area of the tread surface 21 is a range from the tire equator plane CL to the outer side in the tire width direction to a position of 70% of TDW / 2 in the contact area on the tread surface 21. Further, the shoulder region of the tread surface 21 is TDW / 2 from the position of 70% of TDW / 2 (outermost position in the tire width direction in the center region) outward from the tire equator surface CL in the tire width direction in the ground contact region. The range is up to the position of 90 [%]. The ground contact area refers to the tire width direction and tire in which the tread surface 21 contacts the road surface when a pneumatic tire is assembled on a regular rim, filled with a regular internal pressure, and 70% of the regular load is applied. It is a region in the circumferential direction. The normal load is “maximum load capacity” defined by JATMA, a maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  Further, as shown in FIGS. 2 and 3, the pneumatic tire of the present embodiment has a tire width from a position Q where the normal S of the tread surface 21 passing through the reference point P intersects the belt reinforcing layer 8. The rubber gauge tsh of the tread portion 2 that is the shortest distance to the tread surface 21 is 5.0 [mm] ≦ tsh ≦ 8.0 [mm at a position Qsh of 10 [%] of the tread development width TDW / 2 on the inner side in the direction. ], And a position Qout of 10 [%] of the tread development width TDW / 2 from the position Q where the normal S of the tread surface 21 passing through the reference point P intersects the belt reinforcing layer 8 to the outer side in the tire width direction. The rubber gauge tout of the tread portion 2 that is the shortest distance to the tread surface 21 preferably satisfies 2.0 [mm] ≦ tout ≦ 5.0 [mm].

  Here, the position Qsh and the position Qout of the belt reinforcing layer 8 are positions on a straight line connecting the outermost radial direction outer sides of the cord 8a of the belt reinforcing layer 8 (reinforcing layer 82), as shown in FIG.

  By setting the rubber gauge tsh of the tread portion 2 to 5.0 [mm] or more at the position Qsh of the belt reinforcing layer 8, it becomes possible to ensure the wear life, and the rubber gauge tsh of the tread portion 2 is set to 8.0 [mm]. mm] or less, it is possible to suppress an increase in tire weight that deteriorates rolling resistance. In order to obtain this effect more remarkably, it is preferable that 6.0 [mm] ≦ tsh ≦ 7.5 [mm]. Further, by setting the rubber gauge tout of the tread portion 2 to 2.0 [mm] or more at the position Qout of the belt reinforcing layer 8, it is possible to prevent the tread portion 2 from being damaged while protecting the belt reinforcing layer 8. Thus, by setting the rubber gauge tout of the tread portion 2 to 5.0 [mm] or less, the contraction force (deformation) in the tire radial direction is suppressed in the portion near the ground contact region in the vicinity of the position Qout, and the tread surface 21 Since the contact pressure on the outer side (shoulder region) in the tire width direction is reduced, it is possible to further suppress local wear on the edge portion on the outer side in the tire width direction of the tread surface 21. In order to obtain this effect more remarkably, it is preferable that 3.0 [mm] ≦ tout ≦ 4.5 [mm].

  2 and 3, the pneumatic tire according to the present embodiment has a tire width direction from a position Q where the normal line S of the tread surface 21 passing through the reference point P intersects in the belt reinforcing layer 8. The base Q is the position Qsh of 10% of the tread development width TDW / 2, and the stiffness coefficient [N] of the cord 8a on the outer side in the tire width direction from the base point is the number of driven [50/50] per 50 [mm]. The product of [mm]] is the protruding-side ply rigidity coefficient Xsh [N · line / 50 [mm]], and the rigidity coefficient [N] in the cord 8a on the inner side in the tire width direction from the base point is about 50 [mm]. When the product of the number of driven wires [number / 50 [mm]] is the center-side ply stiffness coefficient Xce [N / number], 0.40 ≦ Xce / Xsh ≦ 0.90, 15 ≦ Xsh ≦ 40 Prefer to meet There.

  Here, the ply stiffness coefficient Xi (i = sh, ce) is defined by Xi = Ki [kN] × Ni [lines / 50 [mm]], and Ki [N] is a cord per cord 8a. It is a stiffness coefficient (calculated from a load elongation of 5 [N] or more and 50 [N] or less), and Ni is the number of driving per 50 [mm] width in the tire width direction of the belt reinforcing layer 8 (reinforcing layers 81 and 82). [Book / 50 [mm]]. In addition, the cord stiffness coefficient is a tensile test based on the JIS L1017-2002 chemical fiber tire cord test method (in this case, the tensile test should be carried out within 3 minutes after collecting the cord from the pneumatic tire). The tensile stiffness coefficient K of the cord K = 34.2 / (e2-e1) × 100 where e1 [%] when loaded with 9.8 [N] and e2 [%] when loaded with 44 [N] is loaded. It is calculated from the following formula.

  By setting Xce / Xsh in the range of 0.40 or more and 0.90 or less, the rigidity in the ranges Wsh and Wout of the belt reinforcing layer 8 can be set to a more suitable range from the desired central arc 21a to the shoulder arc 21b. It becomes possible to make it easy to obtain the amount of depression. If Xsh is too small, the rigidity of the belt reinforcing layer 8 in the ranges Wsh and Wout tends to be insufficient, and the shoulder is reduced due to the reduction in deformation due to the contraction force on the outer side in the tire width direction from the vicinity of the outer edge in the tire width direction. There is a tendency that the wear improvement effect of the region is reduced. Also, if Xce is too large, the tensile strength tends to be large, and the belt layer 7 tends to bite inward in the tire radial direction at the time of the vulcanization lift, which may cause a vulcanization failure. Tend to be. Therefore, it is preferable to satisfy 15 ≦ Xsh ≦ 40. In order to obtain the above effects remarkably, it is more preferable to satisfy 0.55 ≦ Xce / Xsh ≦ 0.75 and 20 ≦ Xsh ≦ 35.

  In the pneumatic tire of the present embodiment, the cord 8a of the belt reinforcing layer 8 is preferably made of organic fibers.

  When an organic fiber is used for the cord 8a, the rigidity per cord 8a is reduced, and a desired amount of depression from the central arc 21a to the shoulder-side arc 21b is easily obtained. Further, when an organic fiber is used for the cord 8a, the ply rigidity can be increased by the number of driving [50 / mm] per 50 [mm] width in the tire width direction, in which case the rubber volume between the cords 8a is increased. It becomes possible to suppress the influence on rolling resistance.

  Further, the pneumatic tire of the present embodiment is preferably formed so as to satisfy 0.55 ≦ TDW / SW ≦ 0.75 when the tire cross-sectional width is SW. Here, the tire cross-sectional width is a dimension at a position where the width is the largest in the tire width direction.

  By defining the profile of the belt reinforcing layer 8 and the tread surface 21, even when the tread development width TDW is relatively small, the effect of improving the wear resistance of the tread surface 21 can be obtained, and the rolling resistance can be further reduced. Become. However, when TDW / SW is less than 0.55, it is difficult to obtain the effect of improving the wear resistance of the tread surface 21. On the other hand, when TDW / SW exceeds 0.75, it is difficult to obtain an effect of reducing rolling resistance. Therefore, by setting it as the above-mentioned range, it becomes possible to remarkably obtain the effect of improving the wear resistance of the tread surface 21 and the effect of reducing the rolling resistance. In order to obtain the above effect remarkably, it is more preferable to satisfy 0.60 ≦ TDW / SW ≦ 0.70.

  Moreover, it is preferable that the pneumatic tire of this Embodiment is applied to the pneumatic tire for passenger cars with a high internal pressure. Here, the high internal pressure indicates an internal pressure in a range of 280 [kPa] to 350 [kPa].

  In order to reduce the fuel consumption of passenger vehicles equipped with pneumatic tires, it is effective to increase the operating air pressure in order to reduce the rolling resistance of pneumatic tires. In order to increase the input, the diameter growth of the center region, which is the center in the tire width direction, increases, and if the contact pressure in the center region increases accordingly, the center region of the tread surface 21 is likely to be worn. According to this pneumatic tire, in the pneumatic tire for passenger cars having such a high internal pressure, it is possible to significantly obtain the effect of improving the wear resistance in the center region of the tread surface 21.

  In this example, performance tests on tire performance (wear life, shoulder wear, rolling resistance) were performed on a plurality of types of pneumatic tires having different conditions (see FIGS. 4 to 10).

  In this performance test, a pneumatic tire with a tire size of 215 / 55R17 was assembled on a rim of a 17 × 7J aluminum wheel and filled with the air pressure (230 [kPa] or 300 [kPa]) applied to each example. (3000 [cc] front engine rear drive sedan passenger car).

  In the wear life evaluation method, the remaining groove amount (groove depth) at the maximum groove depth position in the center region when the test vehicle travels 10,000 [km] on the dry test road is measured. Then, based on the measurement result, index evaluation is performed with the conventional example 1 as a reference (100). This index evaluation indicates that the larger the numerical value, the better the wear life performance.

  In the shoulder wear evaluation method, the remaining groove amount (groove depth) at the maximum groove depth position in the shoulder region when the test vehicle travels 10,000 [km] on the dry test road is measured. Then, based on the measurement result, index evaluation is performed with the conventional example 1 as a reference (100). This index evaluation indicates that the larger the value, the better the shoulder wear resistance.

  In the rolling resistance evaluation method, the above test tire to which a load (4.2 [kN]) was applied was pre-run for 20 [min] at a speed of 80 [km / h] on a steel drum type rolling resistance tester. The rolling resistance is measured. Then, based on the measurement result, index evaluation is performed with the conventional example 1 as a reference (100). This index evaluation indicates that the larger the value, the lower the rolling resistance and the better.

  4 to 10, the pneumatic tires of Conventional Example 1 and Conventional Example 2 are the pneumatic tires of Patent Document 1 (Japanese Patent Application No. 2008-307948), and the pneumatic tire of Conventional Example 1 has an internal pressure. 230 [kPa], and the pneumatic tire of Conventional Example 2 had an internal pressure of 300 [kPa].

  In FIG. 4, the pneumatic tires of Comparative Example 1 and Comparative Example 2 have the prescribed belt reinforcing layer, but the tread surface profile (θ, Rc / Rs, L / (TDW / 2): the same applies hereinafter. ) Out of the specified range. On the other hand, the pneumatic tires of Examples 1 to 9 had a specified belt reinforcing layer, had a tread surface profile within a specified range, and varied θ. Note that the pneumatic tire of this performance test has a flatness ratio of 55, and the prescribed range of θ is 1.5 or more and 3.625 or less, preferably 1.85 or more and 3.25 or less.

  In FIG. 5, the pneumatic tires of Comparative Example 3 and Comparative Example 4 have the specified belt reinforcing layer, but Rc / Rs in the profile of the tread surface is out of the specified range. On the other hand, the pneumatic tires of Examples 10 to 16 had a specified belt reinforcing layer, had a tread surface profile within a specified range, and changed Rc / Rs.

  In FIG. 6, the pneumatic tires of Comparative Example 5 and Comparative Example 6 have the specified belt reinforcing layer, but L / (TDW / 2) in the profile of the tread surface is out of the specified range. . On the other hand, the pneumatic tires of Examples 17 to 23 had the specified belt reinforcing layer, the tread surface profile was set to the specified range, and L / (TDW / 2) was changed.

  In FIG. 7, the pneumatic tire of Comparative Example 7 has a tread surface profile within a specified range, but does not have a specified belt reinforcing layer. The pneumatic tire of Comparative Example 8 has a tread surface profile within a specified range and has a belt reinforcing layer, but is not a specified belt reinforcing layer. On the other hand, the pneumatic tires of Examples 24 to 32 had a tread surface profile in a specified range, a specified belt reinforcing layer, and a rubber gauge in a specified range.

  In FIG. 8, the pneumatic tire of Comparative Example 9 has a tread surface profile within a specified range and has a belt reinforcing layer, but is not a specified belt reinforcing layer. On the other hand, the pneumatic tires of Example 33 to Example 42 had the tread surface profile in a specified range, had a specified belt reinforcing layer, and had Xce / Xsh and Xsh in the specified range. In the pneumatic tires of Examples 34 to 42, the rubber gauge was further set in a specified range. In the pneumatic tires of Examples 33 to 42, the cord type of the belt reinforcing layer was an organic fiber.

  In FIG. 9, the pneumatic tire of Comparative Example 10 has a tread surface profile within a specified range and has a belt reinforcing layer, but is not a specified belt reinforcing layer. On the other hand, the pneumatic tires of Examples 43 to 50 had the tread surface profile in a specified range, the specified belt reinforcing layer, and TDW / SW in the specified range. In addition, the pneumatic tires of Example 44 and Examples 46 to 50 were further provided with a rubber gauge within a specified range. Further, in the pneumatic tires of Example 45 to Example 50, Xce / Xsh and Xsh were set within the specified ranges. Further, in the pneumatic tires of Examples 45 to 50, the cord type of the belt reinforcing layer was organic fiber.

  In FIG. 10, the pneumatic tire of Comparative Example 11 has an internal pressure of 300 [kPa], has a tread surface profile within a specified range, and has a belt reinforcing layer. Absent. On the other hand, the pneumatic tires of Examples 51 to 56 have an internal pressure of 300 [kPa], have a tread surface profile in a specified range, and have a specified belt reinforcing layer. In the pneumatic tires of Example 52, Example 53, Example 55, and Example 56, the rubber gauge was further set in a specified range. Further, in the pneumatic tires of Example 53 and Example 56, Xce / Xsh and Xsh were set within the specified ranges. Further, in the pneumatic tires of Example 53 and Example 56, the cord of the belt reinforcing layer was made of organic fibers. In the pneumatic tires of Examples 54 to 56, TDW / SW was set within a specified range.

  As shown in the test results of FIGS. 4 to 10, it can be seen that the pneumatic tires of Examples 1 to 56 have improved wear life, shoulder wear, and rolling resistance.

2 Tread portion 21 Tread surface 21a Center portion arc 21b Shoulder side arc 21c Shoulder portion arc 21d Side portion arc 6 Carcass layer 7 Belt layer 8 Belt reinforcement layer 8a Cord 8b Coat rubber CC Center crown CL Tire equatorial plane (tire equatorial line)
L Reference development width P Reference point S Normal Rc Curvature radius of central arc Rs Curvature radius of shoulder side arc SW Tire cross-section width TDW Tread development width β Flatness θ Angle

Claims (6)

A carcass layer, and a belt layer disposed on the outer side in the tire radial direction of the carcass layer at the tread portion, and provided on the outer side in the tire radial direction of at least both outer ends in the tire width direction of the belt layer. In a pneumatic tire provided with a belt reinforcing layer having a cord along the direction,
The tread surface of the tread portion is formed of an arc having a plurality of different radii of curvature including at least a central arc located at the center in the tire width direction and a shoulder side arc continuous to the outer side in the tire width direction of the central arc. In the state in which 5% of the normal internal pressure is assembled by being incorporated in the normal rim and filled with the internal pressure, in the sectional view in the tire meridian direction, the virtual extension line of the shoulder side arc and the outermost side portion in the tire width direction in the tread portion The intersection between the virtual extension line of the arc is the reference point, the intersection between the tire equator plane and the profile of the tread surface is the center crown, and a straight line connecting the reference point and the center crown passes through the center crown. The angle between the straight line parallel to the tire width direction is θ, the radius of curvature of the central arc is Rc, and the radius of curvature of the shoulder-side arc is s, and L is a reference development width that is an arc length from the tire equator plane to the position in the tire width direction inner end of the shoulder side arc, and a reference line that passes through the reference point and is parallel to the tire equator plane is When the tread deployment width, which is the arc length in the tire width direction between the points intersecting the tread surface, is TDW and the flatness is β,
The tread surface is
0.02 × β + 0.4 ≦ θ ≦ 0.035 × β + 1.7,
12 ≦ Rc / Rs ≦ 30,
0.2 ≦ L / (TDW / 2) ≦ 0.7,
Formed to meet the
The belt reinforcing layer is disposed at least in a range of 10 [%] of the tread development width TDW / 2 on both sides in the tire width direction from a position where the normal line of the tread surface passing through the reference point intersects. A featured pneumatic tire.   From the position where the normal line of the tread surface passing through the reference point intersects the belt reinforcing layer to the tread surface at a position of 10% of the tread deployment width TDW / 2 inward in the tire width direction. A normal line of the tread surface that the rubber gauge tsh of the tread portion that is the shortest distance satisfies 5.0 [mm] ≦ tsh ≦ 8.0 [mm] and passes through the reference point with respect to the belt reinforcing layer. The rubber gauge tout of the tread portion, which is the shortest distance to the tread surface, at a position of 10% of the tread development width TDW / 2 from the position where the tires cross in the tire width direction is 2.0 [mm] ≦ The pneumatic tire according to claim 1, wherein tout ≦ 5.0 [mm] is satisfied. In the belt reinforcing layer, the position of 10% of the tread development width TDW / 2 is set as a base point on the inner side in the tire width direction from the position where the normal line of the tread surface passing through the reference point intersects, and the tire starts from the base point. The product of the stiffness coefficient [N] in the outer cord in the width direction and the number of driven wires per 50 [mm] [lines / 50 [mm]] is the protruding side ply stiffness coefficient Xsh [N · lines / 50 [mm]] The product of the stiffness coefficient [N] and the number of driving per 50 [mm] in the cord in the tire width direction from the base point [number / 50 [mm]] is the center side ply stiffness coefficient Xce [N · number / 50 [Mm]]
0.40 ≦ Xce / Xsh ≦ 0.90,
15 ≦ Xsh ≦ 40,
The pneumatic tire according to claim 1, wherein:   The pneumatic tire according to any one of claims 1 to 3, wherein the cord of the belt reinforcing layer is made of an organic fiber.   The pneumatic tire according to any one of claims 1 to 4, wherein when the tire cross-sectional width is SW, 0.55≤TDW / SW≤0.75 is satisfied.   The pneumatic tire according to any one of claims 1 to 5, which is applied to a pneumatic tire for a passenger car having a high internal pressure.

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