JP2013166416A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire improving riding comfort while suppressing wear of a tread surface.SOLUTION: In a tread surface, an angle θ between a straight line A for connecting a reference point and a center crown CC and a straight line B of a tire width direction passing the center crown, in relation to an aspect ratio β, satisfies a relation of 0.04×β+2.0≤θ≤0.06×β+3.5, a curvature radius Rc of a center portion arc 21a and a curvature radius Rs of a shoulder side arc satisfy a relation of 12≤Rc/Rs≤30, a reference developed width L from a tire equatorial plane CL up to a tire width direction inside end of the shoulder side arc and a tread developed width TDW satisfy a relation of 0.2≤L/(TDW/2)≤0.7, the tread developed TDW and a tire cross-sectional width SW satisfy a relation of 0.55≤TDW/SW≤0.65, a tire radial direction dimension a from a tire radial direction outermost side position up to a pattern end E and a tire cross-sectional height SH satisfy a relation of 0.21≤a/SH≤0.32, and an effective belt width BW and the tread developed width TDW satisfy a relation of 1.00≤BW/TDW≤1.10.

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. The present invention relates to a pneumatic tire that suppresses and improves ride comfort.

  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, it is incorporated in a normal rim and filled with 5% of the normal internal pressure, and the cross-sectional view in the tire meridian direction from the outermost position in the tire width direction of the belt layer to the outer side in the tire radial direction The intersection of the imaginary line parallel to the tire 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 Is the angle formed by the line parallel to the tire width direction, θ, the radius of curvature of the central arc is Rc, the radius of curvature of the shoulder side arc is Rs, and from 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, when the air pressure used is increased, the diameter growth of the center region, which is the center in the tire width direction, is increased, and if the contact pressure in the center region is increased accordingly, the tread surface is easily worn.

  In the pneumatic tire described in Patent Document 1 described above, the wear of the center region of the tread surface tends to be improved by bringing the curvature of the profile along the tire width direction of the tread surface close to a straight line. However, when the working air pressure is increased, the amount of deflection decreases, and the longitudinal (tire radial direction) spring rises accordingly, and the riding comfort tends to deteriorate.

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

  In order to solve the above-described problems and achieve the object, in the pneumatic tire of the present invention, a belt layer is disposed on the outer side in the tire radial direction of the carcass layer in the tread portion, and the tread surface of the tread portion is a tire. In a pneumatic tire formed of a plurality of arcs of different curvature radii including at least a central arc positioned in the center in the width direction and a shoulder-side arc continuous to the outside in the tire width direction of the central arc, In a state where 5% of the normal internal pressure is incorporated and the internal pressure is filled, in the sectional view in the tire meridian direction, the imaginary extension line of the shoulder-side arc and the outermost side arc of the tire width direction in the tread portion The intersection point of the virtual extension line is a reference point, the intersection point of the tire equator plane and the profile of the tread surface is a center crown, and the reference point and the center An angle formed by a straight line connecting the round and a straight line passing through the center crown and parallel to the tire width direction is θ, the curvature radius of the central arc is Rc, and the curvature radius of the shoulder arc is Rs. And a reference development width which is an arc length from the tire equator plane to the inner end position in the tire width direction of the shoulder side arc is L, and a reference line passing through the reference point and parallel to the tire equator plane is The tread deployment width, which is the arc length in the tire width direction between the points intersecting the tread surface, is TDW, the flatness is β, the tire cross-section width is SW, the tire cross-section height is SH, and the tire radial direction outermost side When the tire radial dimension from the position to the pattern end is a and the effective belt width in the belt layer is BW, the tread surface is 0.04 × β + 2.0 ≦ θ ≦ 0.0. × β + 3.5, 12 ≦ Rc / Rs ≦ 30, 0.2 ≦ L / (TDW / 2) ≦ 0.7, 0.55 ≦ TDW / SW ≦ 0.65, 0.21 ≦ a / SH ≦ 0 .32, 1.00 ≦ BW / TDW ≦ 1.10.

  According to this pneumatic tire, the tread deployment width TDW is defined to be narrower than that of a general pneumatic tire (0.55 ≦ TDW / SW ≦ 0.65), and the effective belt width BW and the tread deployment width are defined. BW / TDW, which is the ratio of TDW, is in the range of 1.00 ≦ BW / TDW ≦ 1.10, and the tire radial dimension a from the tire radial outermost position to the pattern end E with respect to the tire cross-section height SH Is defined to be larger as a range of 0.21 ≦ a / SH ≦ 0.32. For this reason, in the buttress part between the part of the tread part on both outer sides in the tire width direction and the part exposed on the outermost side in the tire width direction, a flexible region becomes larger and the lateral (tire width direction) spring decreases. Since the vertical (tire radial direction) spring is reduced while suppressing the above, the ride comfort can be improved.

  In addition, the angle θ is set to a relatively large range of 0.04 × β + 2.0 ≦ θ ≦ 0.06 × β + 3.5 in accordance with the relatively narrow tread development width TDW. Thus, the amount of depression from the central arc to the shoulder-side arc is optimized, so that center wear can be improved while suppressing deterioration of wear in the shoulder region of the tread surface. Further, the relationship between the curvature radius Rc of the central arc and the curvature radius Rs of the shoulder-side arc is 12 ≦ Rc / Rs ≦ 30, and the relationship between the reference development width L and the tread development width TDW is 0.2 ≦ L / ( By setting TDW / 2) ≦ 0.7, the radial growth of the central arc is sufficiently suppressed, and the deterioration of the shoulder region of the tread surface is suppressed, and the wear of the center region of the tread surface is improved. be able to.

  Further, in the pneumatic tire of the present invention, the curvature radius SHR of the shoulder portion arc in which one end portion is in contact with the shoulder side arc and the other end portion is in contact with the outermost side arc in the tire width direction of the tread portion is set. 32 ≦ SHR ≦ 40.

  By setting the radius of curvature SHR to 32 or more, shoulder wear can be more suitably suppressed, and by setting it to 45 or less, center wear can be preferably suppressed. Therefore, according to this pneumatic tire, the rolling resistance can be reduced and the effect of suppressing the wear on the tread surface can be significantly obtained.

  The pneumatic tire according to the present invention is characterized in that an average thickness of rubber on the outer side of the tire near the pattern end is 2 [mm] or more and 7 [mm] or less.

  By setting the average thickness T of the rubber to 2 [mm] or more, a reduction in cut resistance can be suppressed, and by setting it to 7 [mm] or less, an effect of reducing the vertical spring can be obtained.

  In the pneumatic tire of the present invention, at least two main grooves extending in the tire circumferential direction are provided in the tread portion in the tire width direction, and a plurality of land portions are defined in the tire width direction on the tread surface. A plurality of sub-grooves extending in the tire circumferential direction are arranged in parallel in the tire circumferential direction at least on the outermost shoulder land portion in the tire width direction, and the number of sub-grooves in one shoulder land portion is It is characterized by being 90 or more and 160 or less.

  In one shoulder land portion, the number of sub-grooves is 90 or more, so that the stress of the shoulder land portion can be reduced and rolling resistance can be further reduced. By setting the number to 160 or less, the shoulder region of the tread surface Can be more suitably suppressed.

  In the pneumatic tire of the present invention, all the sub-grooves of the shoulder land portion are formed as lug grooves, and the number of the lug grooves in one shoulder land portion is 75 or more and 100 or less. Features.

  When all the sub-grooves of the shoulder land portion are lug grooves, the number of the shoulder land portions is 75 or more so that the stress of the shoulder land portion can be reduced and the rolling resistance can be further reduced. By setting the number to the number of pieces or less, it is possible to more suitably suppress wear of the shoulder region of the tread surface.

  In the pneumatic tire of the present invention, at least two main grooves extending in the tire circumferential direction are provided in the tread portion in the tire width direction, and the outermost shoulder land portion in the tire width direction is provided on the tread surface. A center land portion on the inner side in the tire width direction of the shoulder land portion is sectioned, and a plurality of sub-grooves extending in the direction intersecting the main groove are juxtaposed in the tire circumferential direction in each of the land portions. The number of the sub grooves in the center land portion is smaller than the number of the sub grooves in one shoulder land portion.

  One center land portion has fewer sub-grooves than one shoulder land portion, so that the rigidity on the center land portion side can be increased and steering stability can be improved.

  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 of the center region, which is the center in the tire width direction, increases, and when the contact pressure in the center region increases, the center region 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 riding comfort can be obtained remarkably while suppressing wear on the tread surface.

  The pneumatic tire according to the present invention can improve riding comfort while suppressing wear on 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 chart showing the results of the performance test of the pneumatic tire according to the example 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. FIG. 11 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 12 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 13 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, and FIG. 2 is a partially cut meridional sectional view of the pneumatic tire according to the present embodiment.

  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 has a land portion formed by a plurality of grooves. As an example, in the pneumatic tire according to the present embodiment, the tread surface 21 is provided with a plurality of (at least two) main grooves 22 extending along the tire circumferential direction, as shown in FIG. . Here, the main groove 22 indicates a groove extending in the tire circumferential direction having a groove width of 4.0 [mm] or more. The tread surface 21 extends along the tire circumferential direction by a plurality of main grooves 22, and rib-shaped land portions 23 parallel to the tire equator line CL are defined. In the present embodiment, five land portions 23 are provided on the tread surface 21 with the main groove 22 as a boundary, and three center land portions provided on the inner side in the tire width direction of the outermost main groove 22 in the tire width direction. 23a and two shoulder land portions 23b provided on the outer side in the tire width direction of the outermost main groove 22 in the tire width direction. That is, the shoulder land portion 23b is formed on the outermost side in the tire width direction of the tread surface 21, and the center land portion 23a is formed on the inner side in the tire width direction of the shoulder land portion 23b.

  Further, the tread surface 21 is provided with a sub-groove 24 that intersects the main groove 22 in each land portion 23. The secondary groove 24 includes a sipe and a lug groove. Here, sipe indicates a groove extending in a direction intersecting the tire circumferential direction with a groove width of 1 [mm] or less. A lug groove shows the groove | channel extended in the direction which cross | intersects with respect to a tire peripheral direction exceeding 1 [mm] except groove | channel. The sipe has a shape in which both ends penetrate the land portion 23, a shape in which only one end penetrates the land portion 23, and a shape in which both ends terminate in the land portion 23. The lug groove has a shape in which both ends penetrate the land portion 23 and a shape in which only one end penetrates the land portion 23. In the present embodiment, the sub-groove 24 may have a sipe and a lug groove, or may have only a lug groove.

  Further, the tread surface 21 is an imaginary line that continues in the tire circumferential direction with reference to this end portion at the end portion where the lug groove, which is the sub groove 24 provided in the shoulder land portion 23b, extends to the outermost side in the tire width direction. The position where is subtracted is defined as a pattern end E (see FIG. 2).

  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. 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. The reinforcing layers 81 and 82 are made by coating a plurality of cords (not shown) arranged in parallel in the tire width direction (± 5 degrees) in the tire circumferential direction with a coat rubber. The cord 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 only needs to overlap at least the end portion in the tire width direction of the belt layer 7. 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, a virtual extension line of the shoulder-side arc 21b in a cross-sectional view in the tire meridian direction shown in FIG. 2 in a no-load state in which a pneumatic tire is incorporated in a normal rim and filled with 5% of the normal internal pressure. And the intersection of the imaginary extension line of the side portion 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 be β. The tire cross-sectional width is SW. The tire cross-sectional height is SH. Further, a dimension in the tire radial direction from the outermost position in the tire radial direction (in this embodiment, the center crown CC) to the pattern end E is a. The effective belt width in the belt layer 7 is BW.

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 (6).
0.04 × β + 2.0 ≦ θ ≦ 0.06 × β + 3.5 (1)
12 ≦ Rc / Rs ≦ 30 (2)
0.2 ≦ L / (TDW / 2) ≦ 0.7 (3)
0.55 ≦ TDW / SW ≦ 0.65 (4)
0.21 ≦ a / SH ≦ 0.32 (5)
1.00 ≦ BW / TDW ≦ 1.10 (6)

  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 is the ratio of the tire cross-sectional height to the tire cross-sectional 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 is ½ of the difference between the outer diameter and the rim diameter of an unloaded tire in which the tire is assembled on a regular rim and filled with a regular internal pressure. The effective belt width BW of the belt layer 7 is a tire width direction dimension of a belt (belt 72 in the present embodiment) having the shortest tire width direction dimension in the belt layer 7.

  As described above, in the pneumatic tire according to the present embodiment, when the intersection point of the extension lines of the shoulder-side arc 21b and the side-part arc 21d is the reference point P, the reference point and the center crown CC are defined with respect to the flatness β. The angle θ between the connecting straight line A and the straight line B passing through the center crown CC in the tire width direction is 0.04 × β + 2.0 ≦ θ ≦ 0.06 × β + 3.5, and the radius of curvature Rc of the central arc 21a And the radius of curvature Rs of the shoulder-side arc 21b is 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, and the tire radial direction dimension a from the tire radial direction outermost position to the pattern end E and the tire cross-section height SH are 0.21 ≦ a / SH. ≦ 0. It is 2, and the effective belt width BW and the tread width TDW is the 1.00 ≦ BW / TDW ≦ 1.10.

  In the pneumatic tire of the present embodiment, the tread development width TDW is defined narrower than that of a general pneumatic tire (0.55 ≦ TDW / SW ≦ 0.65), and the effective belt width BW and the tread are defined. BW / TDW, which is the ratio of the development width TDW, is in the range of 1.00 ≦ BW / TDW ≦ 1.10, and the tire radial direction from the outermost position in the tire radial direction to the pattern end E with respect to the tire cross-section height SH The dimension a is defined to be larger as a range of 0.21 ≦ a / SH ≦ 0.32. For this reason, in the buttress part between the shoulder part 3 and the side wall part 4, a flexible area becomes large, and the longitudinal (tire radial direction) spring is reduced while suppressing a decrease in the lateral (tire width direction) spring. Therefore, it becomes possible to improve the ride comfort. In addition, since the tread deployment width TDW is narrow, the contact length (tire circumferential direction dimension at the time of contact) tends to increase, so that it is possible to secure the contact length at high pressure and improve the operability. .

  And when TDW / SW is less than 0.55, the width of the belt layer 7 becomes narrow and the durability is lowered. On the other hand, when TDW / SW exceeds 0.65, it becomes equivalent to a general pneumatic tire, and the balance between the vertical spring and the horizontal spring decreases. Further, in a / SH, when the pattern end E approaches the outer side in the tire radial direction, the rubber thickness of the buttress portion becomes relatively thick, so that it is difficult to obtain the effect of reducing the vertical spring. For this reason, by setting it as the range of 0.21 <= a / SH <= 0.32, the balance of a vertical spring and a horizontal spring can be improved, a vertical spring can be reduced, and riding comfort can be improved. Note that it is preferable that the range of 0.24 ≦ a / SH ≦ 0.28 is obtained because the effect of improving the riding comfort can be remarkably obtained.

  Further, the angle θ is set to a relatively large range of 0.04 × β + 2.0 ≦ θ ≦ 0.06 × β + 3.5 in accordance with the relatively narrow tread development width TDW. When the angle θ is less than “0.04 × β + 2.0”, the amount of sagging from the central arc 21a to the shoulder-side arc 21b is too small, and wear of the shoulder region GS (shoulder wear) is likely to occur. On the other hand, when the angle θ exceeds “0.045 × β + 2.5”, the amount of sagging from the central arc 21a to the shoulder-side arc 21b is large, and wear of the center region GC of the tread surface 21 (center wear) is improved. It becomes difficult. Since the amount of sagging from the central arc 21a to the shoulder arc 21b is optimized by setting the angle θ to a range of 0.045 × β + 2.2 ≦ θ ≦ 0.065 × β + 3.2, the tread The effect of improving the center wear can be remarkably obtained while suppressing the deterioration of the wear of the shoulder region GS of the surface 21, which is preferable.

  In addition, when Rc / Rs is less than 12, the diameter growth of the central arc 21a cannot be sufficiently suppressed, and it is difficult to improve the wear of the center region GC of the tread surface 21 by increasing the contact pressure of the center region GC. It becomes. 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 of the center region GC of the tread surface 21 cannot be expected. In addition, by setting it as the range of 15 <= Rc / Rs <= 25, the diameter growth of the center part circular arc 21a is fully suppressed, the deterioration of wear of the shoulder region GS of the tread surface 21 is suppressed, and the center of the tread surface 21 is suppressed. The effect of improving the wear of the region GC can be remarkably obtained, which is preferable.

  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 of the center region GC increases and the center region GC of the tread surface 21 increases. It becomes difficult to improve wear. 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 GC of the tread surface 21 can be expected. Disappear. 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 wear of the shoulder region GS of the tread surface 21 is suppressed. However, the effect of improving the wear of the center region GC of the tread surface 21 can be remarkably obtained, which is preferable.

  As a result, according to the pneumatic tire of the present embodiment, it is possible to improve rolling comfort while reducing rolling resistance and suppressing wear of the tread surface 21.

  Here, the center region GC of the tread surface 21 is a range from the tire equator surface CL to the outer side in the tire width direction to a position of 45 [%] of TDW / 2 in the ground contact region G of the tread surface 21. Further, the shoulder region GS of the tread surface 21 is within the range from the tire equator surface CL to the position 90% of TDW / 2 on the outer side in the tire width direction in the ground contact region G, and in the tire width direction of the center region GC. The range is from the outer edge to the outer side in the tire width direction. The ground contact area G refers to the tire width direction in which the tread surface 21 contacts the road surface when a pneumatic tire is assembled on a normal rim, filled with a normal internal pressure and 70% of the normal load is applied. This is a region in the tire 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.

  In the pneumatic tire according to the present embodiment, one end is in contact with the shoulder-side arc 21b (arc having a radius of curvature Rs), and the other end is the outermost side portion of the tread portion 2 in the tire width direction. It is preferable that the curvature radius SHR of the shoulder portion arc 21c in contact with the arc 21d (arc having an curvature radius of SCR) satisfies 32 ≦ SHR ≦ 40.

  By setting the curvature radius SHR to 32 or more, the wear of the shoulder region GS of the tread surface 21 can be more suitably suppressed, and by setting it to 40 or less, the wear of the center region GC of the tread surface 21 is preferably improved. can do. The curvature radius SHR is more preferably 35 ≦ SHR ≦ 37. It is preferable that the curvature radius SHR is 35 ≦ SHR ≦ 37 because the above effect can be further improved.

  In the pneumatic tire of the present embodiment, as shown in FIG. 2, the average thickness T of the rubber on the tire outer side near the pattern end E is preferably 2 [mm] or more and 7 [mm] or less.

  Here, the vicinity of the pattern end E indicates a buttress portion between the shoulder portion 3 and the sidewall portion 4, and specifically, as shown in FIG. The range H is within 12% of the tire cross-section height SH on both sides. The thickness of the rubber is the dimension of the normal line from the tire surface of the buttress portion to the cord. The average rubber thickness T is an average value of rubber thicknesses measured at a position obtained by dividing the range H into five equal parts in the tire radial direction. By setting the average thickness T of the rubber to 2 [mm] or more, a reduction in cut resistance can be suppressed, and by setting it to 7 [mm] or less, an effect of reducing the vertical spring can be obtained. The average thickness T of the rubber is preferably 3 [mm] or more and 4 [mm] or less because the above effect can be further improved.

  In the pneumatic tire of the present embodiment, the number of sub-grooves 24 in one shoulder land portion 23b is preferably 90 or more and 160 or less.

  By setting the number of sub-grooves 24, that is, lug grooves and sipes, to 90 or more in one shoulder land portion 23b, the stress of the shoulder land portion 23b can be reduced, and the rolling resistance can be further reduced. By setting it to not more than the number, wear of the shoulder region GS of the tread surface 21 can be more suitably suppressed.

  Further, in the pneumatic tire of the present embodiment, all the sub-grooves 24 of the shoulder land portion 23b are formed as lug grooves, and the number of lug grooves in one shoulder land portion 23b is 75 or more and 100 or less. Is this.

  When all the sub-grooves 24 of the shoulder land portion 23b are lug grooves, the number of the shoulder land portions 23b is 75 or more, thereby reducing the stress of the shoulder land portion 23b and further reducing the rolling resistance. When the number is 100 or less, wear of the shoulder region GS of the tread surface 21 can be more suitably suppressed.

  In the pneumatic tire of the present embodiment, it is preferable that the number of sub grooves 24 in one center land portion 23a is smaller than the number of sub grooves 24 in one shoulder land portion 23b.

  The sub-groove 24 includes a case including a lug groove and a sipe, and a case where all the lug grooves are present, and in both, one center land portion 23a has fewer sub-grooves 24 than one shoulder land portion 23b. It becomes possible to improve the steering stability by increasing the rigidity on the center land portion 23a side.

  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 GC, which is the center in the tire width direction, increases, and when the contact pressure of the center region GC increases accordingly, the center region GC of the tread surface 21 is likely to be worn. According to this pneumatic tire, in such a pneumatic tire for passenger cars having a high internal pressure, it is possible to significantly reduce the rolling resistance and suppress the wear of the tread surface 21 while significantly improving the riding comfort. It becomes possible.

  In this example, performance tests on tire performance (riding comfort, center wear, wear life, rolling resistance) were performed on a plurality of types of pneumatic tires having different conditions (see FIGS. 3 to 13).

  In this performance test, a pneumatic tire having a tire size of 195 / 65R15 was assembled to a rim of a 15 × 6 JJ aluminum wheel and filled with air pressure (230 [kPa] or 300 [kPa]) applied to each example. (1500 [cc] front engine front drive passenger car).

  In the performance test of ride comfort (flat road), the above test vehicle runs on a flat test course at 60 [km / h], and one expert driver performs a five-step sensory evaluation on running vibration. went. This evaluation shows an average of three times as an index based on the conventional example as a reference (100), and the higher this index, the better the ride comfort.

  In the center abrasion 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 and the maximum in the shoulder region. The ratio of the groove depth position to the remaining groove amount (groove depth) is measured. Then, based on the measurement result, index evaluation using the conventional example as a reference (100) is performed. This index evaluation indicates that the larger the value, the better the center wear resistance performance.

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

  In the rolling resistance evaluation method, the above test tire to which a load (4.2 [kN]) was applied was preliminarily run for 20 [seconds] 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.

  3 to 13, 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]. The pneumatic tires of Comparative Examples 1 to 18 had an internal pressure of 230 [kPa]. On the other hand, the pneumatic tires of Examples 1 to 60 had an internal pressure of 230 [kPa], and the pneumatic tires of Examples 61 to 64 had an internal pressure of 300 [kPa].

  In FIG. 3, the pneumatic tires of Comparative Example 1 and Comparative Example 2 are tread surface profiles of θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, BW / TDW. θ was outside the specified range. The pneumatic tire of Comparative Example 3 was outside the specified range except for L / (TDW / 2). On the other hand, in the pneumatic tires of Examples 1 to 7, the tread surface profile θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, and BW / TDW are within the specified ranges. , Θ was changed. The pneumatic tire of this performance test has an aspect ratio of 65, and the prescribed range of θ is 4.6 or more and 7.4 or less, and preferably 5.1 or more and 7.1 or less.

  In FIG. 4, the pneumatic tires of Comparative Example 4 and Comparative Example 5 are tread surface profiles of θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, and BW / TDW. Rc / Rs was out of the specified range. The pneumatic tire of Comparative Example 6 was outside the specified range except for θ and L / (TDW / 2). On the other hand, in the pneumatic tires of Examples 8 to 14, the tread surface profile θ, Rc / Rs, L / (TDW / 2), a / SH, and BW / TDW are within the specified ranges, and Rc / Rs. Changed.

  In FIG. 5, the pneumatic tires of Comparative Example 7 and Comparative Example 8 are tread surface profiles of θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, BW / TDW. L / (TDW / 2) was out of the specified range. The pneumatic tire of Comparative Example 9 was outside the specified range except for θ. On the other hand, the pneumatic tires of Examples 15 to 21 have tread surface profiles θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, and BW / TDW as specified ranges. , L / (TDW / 2) was changed.

  In FIG. 6, the pneumatic tires of Comparative Example 10 and Comparative Example 11 are the tread surface profile θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, BW / TDW. TDW / SW was out of the specified range. The pneumatic tire of Comparative Example 12 was outside the specified range except for θ and L / (TDW / 2). On the other hand, the pneumatic tires of Examples 22 to 27 have the tread surface profile θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, and BW / TDW as specified ranges. , TDW / SW was changed.

  In FIG. 7, the pneumatic tires of Comparative Example 13 and Comparative Example 14 are the tread surface profile θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, BW / TDW. a / SH was out of the specified range. The pneumatic tire of Comparative Example 15 was outside the specified range except for θ and L / (TDW / 2). On the other hand, the pneumatic tires of Examples 28 to 33 have tread surface profiles of θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, and BW / TDW as specified ranges. , A / SH was changed.

  In FIG. 8, the pneumatic tires of Comparative Example 16 and Comparative Example 17 are the tread profile of θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, BW / TDW. BW / TDW was out of the specified range. The pneumatic tire of Comparative Example 18 was outside the specified range except for θ and L / (TDW / 2). On the other hand, in the pneumatic tires of Examples 34 to 37, the tread surface profile θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, and BW / TDW are within the specified ranges. BW / TDW was changed.

  In FIG. 9, the pneumatic tires of Examples 38 to 41 are in addition to the tread surface profile θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, and BW / TDW. SHR was within the specified range.

  In FIG. 10, the pneumatic tire of Example 42 has a tread surface profile of θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, BW / TDW, and in the vicinity of the pattern end. The rubber thickness was within the specified range. In the pneumatic tires of Examples 43 to 47, SHR was also in a specified range.

  In FIG. 11, the pneumatic tire of Example 48 has a tread surface profile of θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, BW / TDW, in addition to the shoulder land portion. The number of minor grooves was within the specified range. In the pneumatic tire of Example 49, SHR was also within a specified range. In the pneumatic tires of Examples 50 to 53, the rubber thickness in the vicinity of the pattern end was set within a specified range.

  In FIG. 12, the pneumatic tire of Example 54 corresponds to the shoulder land portion in addition to the tread profile θ, Rc / Rs, L / (TDW / 2), TDW / SW, a / SH, BW / TDW. The number of minor grooves in the center land was set as the specified range. In the pneumatic tire of Example 55, SHR was also in a specified range. In the pneumatic tire of Example 56, the number of sub-grooves in the shoulder land portion was also in a specified range. In the pneumatic tires of Example 57 to Example 60, the number of sub-grooves in the shoulder land portion was also in a specified range.

  In FIG. 13, the pneumatic tires of Examples 61 to 64 had an internal pressure of 300 [kPa].

  As shown in the test results of FIGS. 3 to 13, it can be seen that the pneumatic tires of Examples 1 to 64 have improved riding comfort, center wear, wear life, and rolling resistance, respectively.

2 Tread portion 21 Tread surface 21a Center portion arc 21b Shoulder side arc 21c Shoulder portion arc 21d Side portion arc 22 Main groove 23 Land portion 23a Center land portion 23b Shoulder land portion 24 Sub groove 6 Carcass layer 7 Belt layer a Tire radial direction maximum Tire radial dimension from outer position to pattern end BW Effective belt width CC Center crown CL Tire equatorial plane (tire equatorial line)
E Pattern end L Reference development width P Reference point Rc Curvature radius of central arc Rs Curvature radius of shoulder side arc SW Tire cross section width SH Tire cross section height TDW Tread development width β Flatness θ Angle

Claims (7)

A belt layer is disposed on the outer side in the tire radial direction of the carcass layer in the tread portion, and the tread surface of the tread portion is located on the outer side in the tire width direction of the central portion arc in the center in the tire width direction and the central portion arc. In a pneumatic tire formed of a plurality of arcs of different curvature radii including at least a shoulder-side arc of a continuous shoulder,
In the state where the normal internal pressure is 5% and the internal pressure is filled, the virtual extension line of the shoulder-side arc and the outermost side in the tire width direction in the tread portion in a sectional view in the tire meridian direction A point of intersection with the virtual extension line of the partial arc 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 center crown An angle formed by a straight line passing through and parallel to the tire width direction is θ, a radius of curvature of the central arc is Rc, a radius of curvature of the shoulder-side arc is Rs, and the shoulder-side arc of the shoulder-side arc is from the tire equatorial plane. The reference development width, which is the arc length to the inner end position in the tire width direction, is L, and a reference line passing through the reference point and parallel to the tire equatorial plane is The tread spread width, which is the arc length in the tire width direction between points intersecting the plane, is TDW, the flatness is β, the tire cross section width is SW, the tire cross section height is SH, and the tire radial direction outermost position When the tire radial dimension from to the pattern end is a, and the effective belt width in the belt layer is BW,
The tread surface is
0.04 × β + 2.0 ≦ θ ≦ 0.06 × β + 3.5
12 ≦ Rc / Rs ≦ 30
0.2 ≦ L / (TDW / 2) ≦ 0.7
0.55 ≦ TDW / SW ≦ 0.65
0.21 ≦ a / SH ≦ 0.32
1.00 ≦ BW / TDW ≦ 1.10
A pneumatic tire characterized by being formed to satisfy the above.   A curvature radius SHR of a shoulder arc in which one end portion is in contact with the shoulder-side arc and the other end portion is in contact with the outermost side arc in the tire width direction of the tread portion is formed so as to satisfy 32 ≦ SHR ≦ 40 The pneumatic tire according to claim 1, wherein the pneumatic tire is provided.   The pneumatic tire according to claim 1 or 2, wherein an average thickness of rubber outside the tire near the pattern end is 2 [mm] or more and 7 [mm] or less.   At least two main grooves extending in the tire circumferential direction are provided in the tread portion in the tire width direction, and a plurality of land portions are defined in the tire width direction on the tread surface, and at least the outermost shoulder land in the tire width direction is defined. A plurality of sub-grooves extending in the tire circumferential direction are juxtaposed in the tire cross direction, and the number of the sub-grooves in one shoulder land portion is 90 or more and 160 or less. The pneumatic tire according to any one of claims 1 to 3.   5. The air according to claim 4, wherein all the sub-grooves of the shoulder land portion are formed as lug grooves, and the number of the lug grooves in one shoulder land portion is 75 or more and 100 or less. Enter tire.   At least two main grooves extending in the tire circumferential direction are provided in the tread portion in the tire width direction, the outermost shoulder land portion in the tire width direction on the tread surface, and the center in the tire width direction on the shoulder land portion A land portion is defined, and a plurality of sub-grooves extending in the tire circumferential direction are juxtaposed in a direction intersecting the main groove in each land portion, and the number of sub-grooves in one center land portion 6. The pneumatic tire according to claim 1, wherein the number of sub-grooves in one shoulder land portion is smaller.   The pneumatic tire according to any one of claims 1 to 6, which is applied to a pneumatic tire for a passenger car having a high internal pressure.

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