JP6010932B2 - Pneumatic tire - Google Patents

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 (see, for example, 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, since the ground contact pressure of the shoulder area increases, the shoulder area 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, a pneumatic tire according to the present invention includes a carcass layer and a belt layer disposed on the outer side in the tire radial direction of the carcass layer. A steel reinforcing layer formed by juxtaposing a steel cord of substantially 90 degrees with respect to the tire circumferential direction side by side in the tire circumferential direction is further provided on the outer side in the tire radial direction, and the steel reinforcing layer has an effective belt width in the belt layer. Is a pneumatic tire formed in a range including at least an area of 15 [%] of the effective belt width from the outer end in the tire width direction toward the inner side in the tire width direction, and the tread surface of the tread portion is A plurality of different curvatures including at least a central arc located at the center in the tire width direction and a shoulder-side arc continuous to the outside in the tire width direction of the central arc. A circular arc of a diameter, which is incorporated in a normal rim and filled with 5% of the normal internal pressure, and in a sectional view in the tire meridian direction, a virtual extension line of the shoulder side arc and the tread portion The intersection point between the imaginary extension line of the outermost side arc of the tire width direction is used as a reference point, the intersection point between the tire equatorial plane and the tread surface profile is used as a center crown, and the reference point is connected to the center crown. The angle formed by a straight line and 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 tire equator The reference development width, which is the arc length from the surface to the inner end position in the tire width direction of the shoulder-side arc, is L, and passes through the reference point and is parallel to the tire equatorial plane The tread surface is 0.02 × β + 0.4, where TDW is the tread development width, which is the arc length in the tire width direction between points where a simple reference line intersects the tread surface, and β is the flatness ratio. ≦ θ ≦ 0.035 × β + 1.7, 12 ≦ Rc / Rs ≦ 30, 0.2 ≦ L / (TDW / 2) ≦ 0.7.

  By forming the steel reinforcing layer in a range including at least 15% of the effective belt width from the outer end in the tire width direction of the effective belt width in the belt layer toward the inner side in the tire width direction, the steel reinforcing layer Since the contact pressure of the shoulder region is reduced by the tagging effect, wear of the shoulder region of the tread surface is suppressed. Moreover, by providing the steel reinforcing layer, an angle θ formed by a straight line connecting the reference point P 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, the steel reinforcing layer is arranged between the belt innermost belt in the tire radial direction of the belt layer and the carcass layer.

  The vicinity of the belt edge of the innermost belt in the tire radial direction of the belt layer and the carcass layer are greatly compressed and deformed at the time of contact. Therefore, the steel reinforcing layer is formed in a range including at least an area of 15 [%] of the effective belt width from each outer end in the tire width direction of the effective belt width in the belt layer toward the inner side in the tire width direction. By disposing the layer between the innermost belt in the tire radial direction of the belt layer and the carcass layer, it is possible to further suppress the wear of the shoulder region of the tread surface in order to complement both compression rigidity.

  In the pneumatic tire of the present invention, the steel reinforcing layer is disposed separately in the tire width direction across the tire equatorial plane, and the total width in the tire width direction is 30% of the effective belt width. It is characterized by being formed in the range of 50 [%] or less.

  In order to suppress wear in the shoulder region of the tread surface, the steel reinforcing layer may be formed at least in the region of 15% of the effective belt width. Therefore, in order to suppress an increase in rolling resistance due to an increase in mass, the steel reinforcing layer is preferably configured as described above.

In the pneumatic tire of the present invention, the steel reinforcing layer has a product of one cross-sectional area of the steel cord and the number of driven portions per 50 [mm] of 4.0 [mm ² ] or more and 7.0 [ mm ² ] or less and the strength is 3200 [MPa].

When the product of the cross-sectional area of one steel cord and the number of driven wires per 50 [mm] is less than 4.0 [mm ² ], it is difficult to secure the compression rigidity of the steel reinforcing layer, and deformation near the steel reinforcing layer Insufficient suppression tends to increase rolling resistance. On the other hand, when the product of the cross-sectional area of one steel cord and the number of driven wires per 50 [mm] exceeds 7.0 [mm ² ], the compression rigidity of the steel reinforcing layer tends to be too high, affecting the cornering power. May occur. Therefore, by setting it as the said range, the increase in rolling resistance can be suppressed and the influence on cornering power can be reduced.

  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 when the tread development width TDW is made relatively small by the regulation of the steel 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 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 wear resistance of the center region of the tread surface can be significantly 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 schematic view showing the arrangement of the steel reinforcing layers. FIG. 4 is a schematic view showing the arrangement of the steel reinforcing layers. FIG. 5 is a schematic view showing the arrangement of the steel reinforcing layers. FIG. 6 is a schematic view showing the arrangement of the steel reinforcing layers. FIG. 7 is a schematic view showing the arrangement of the steel reinforcing layers. FIG. 8 is a schematic view showing the arrangement of the steel reinforcing layers. FIG. 9 is a schematic view showing the arrangement of the steel reinforcing layers. FIG. 10 is a schematic view showing the arrangement of the steel reinforcing layers. 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. FIG. 14 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 15 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 16 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 17 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 18 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 FIGS. It is the schematic which shows arrangement | positioning of a steel reinforcement layer.

  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. 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 reinforcing layer 8 shown in FIG. 1 is disposed so that the reinforcing layer 81 and the reinforcing layer 82 cover only the end portion of the belt layer 7 in the tire width direction. 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. The reinforcing layer 81 on the belt layer 7 side is formed to be larger in the tire width direction than the belt layer 7 so as to cover the entire belt layer 7, and the reinforcing layer 82 on the outer side in the tire radial direction of the reinforcing layer 81. May be disposed only at the end portion of the reinforcing layer 81 in the tire width direction so as to cover 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.

  The pneumatic tire includes a steel reinforcing layer 9. The steel reinforcing layer 9 has a steel cord (not shown) arranged in parallel in the tire circumferential direction at an angle of 90 degrees (including an error of ± 5 degrees) with respect to the tire circumferential direction, and is coated with a coat rubber. Yes. The steel cord (metal cord) of the steel reinforcing layer 9 is made of, for example, steel or carbon steel. The steel reinforcing layer 9 is disposed outside the carcass layer 6 in the tire radial direction. 1 to 3 and 7 to 10, the steel reinforcing layer 9 shows a form in which the belt layer 7 is disposed between the innermost belt 71 in the tire radial direction and the carcass layer 6. In addition, the steel reinforcement layer 9 may be arrange | positioned between each belt 71,72 of the belt layer 7, as shown in FIG. Moreover, the steel reinforcement layer 9 may be arrange | positioned between the belt layer 7 and the belt reinforcement layer 8, as shown in FIG. Moreover, the steel reinforcement layer 9 may be arrange | positioned in the tire radial direction outer side of the belt reinforcement layer 8, as shown in FIG. Further, in each arrangement in the tire radial direction, the steel reinforcing layers 9 may be arranged apart in the tire width direction with the tire equatorial plane CL interposed therebetween as shown in FIGS. Further, as shown in FIGS. 1 and 3 to 10, the steel reinforcing layer 9 has an effective belt width W from the outer end in the tire width direction of the effective belt width W of the belt layer 7 toward the inner side in the tire width direction. It is formed in a range including at least the 15% region W1. The effective belt width W of the belt layer 7 indicates the tire width direction dimension of the belt (the belt 72 in the present embodiment) having the shortest tire width direction dimension in the belt layer 7. The steel reinforcing layer 9 preferably has an outer end in the tire width direction within the maximum width of the belt layer 7 in the tire width 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.

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 is the ratio of the tire cross-section height 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 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.

  As described above, the pneumatic tire according to the present embodiment includes a steel reinforcing layer in which steel cords of substantially 90 degrees with respect to the tire circumferential direction are juxtaposed in the tire circumferential direction outside the carcass layer 6 in the tire radial direction. 9 is provided. The steel reinforcing layer 9 is formed in a range including at least an area of 15% of the effective belt width W from the outer end in the tire width direction of the effective belt width W of the belt layer 7 toward the inner side in the tire width direction. ing. Further, when the intersection point of each extension line of the shoulder side arc 21b and the side portion arc 21d is defined as the reference point P, the straight line A connecting the reference point and the center crown CC with respect to the flatness β passes through the center crown CC. The angle θ with the straight line B in the tire width direction is 0.02 × β + 0.4 ≦ θ ≦ 0.035 × β + 1.7, and the curvature radius Rc of the central arc 21a and the curvature radius Rs of the shoulder-side arc 21b are 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.

  By forming the steel reinforcing layer 9 in a range including at least 15% of the effective belt width W from the outer end in the tire width direction of the effective belt width W in the belt layer 7 toward the inner side in the tire width direction, Since the contact pressure of the shoulder region GS is reduced by the hoop effect of the steel reinforcing layer 9, wear (shoulder wear) of the shoulder region GS of the tread surface 21 is suppressed. As shown in FIGS. 7, 9, and 10, when the steel reinforcing layer 9 is formed in a part of the region W1 of 15 [%] of the effective belt width W, at least 50 [ %] Is preferable for obtaining the above effect.

  Moreover, according to the pneumatic tire of the present embodiment, by including the steel reinforcing layer 9, the straight line A connecting the reference point P and the center crown CC and the center crown CC are passed through and parallel to the tire width direction. The angle θ formed by the straight line B is in the range of 0.02 × β + 0.4 ≦ θ ≦ 0.035 × β + 1.7 from the central arc 21a to the shoulder-side arc 21b and toward the inside in the tire radial direction. It is possible to make the angle θ, which is the amount of sagging, smaller. It is preferable to reduce the angle θ in order to improve the wear (center wear) of the center region GC of the tread surface 21. However, if the angle θ is too small, the wear of the shoulder region GS of the tread surface 21 tends to be deteriorated.

  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 GS of the tread surface 21 and the wear of the center region GC of the tread surface 21. That is, it is possible to improve the wear of the center region GC while suppressing the deterioration of the wear of the shoulder region GS.

  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 wear of the shoulder region GS of the tread surface 21 is suppressed. The effect is reduced. 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 of the center region GC 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 GC of the tread surface 21 can be significantly obtained while suppressing the wear of the shoulder region GS of the surface 21.

  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.

  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 significantly obtained.

  As a result, according to the pneumatic tire of the present embodiment, the wear of the center region GC of the tread surface 21 is improved while suppressing the deterioration of the wear of the shoulder region GS of the tread surface 21. The wear resistance can be improved.

  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 70 [%] 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 TDW from the position of 70% of TDW / 2 (outermost position in the tire width direction of the center region GC) to the outer side in the tire width direction from the tire equator surface CL in the ground contact region G. The range up to the 90% position of / 2. 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, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  Moreover, in the pneumatic tire of the present embodiment, the steel reinforcing layer 9 includes the belt 71 and the carcass layer 6 on the innermost side in the tire radial direction of the belt layer 7 as shown in FIGS. 1 to 3 and 7 to 10. It is preferable to arrange | position between.

  The vicinity of the belt edge of the belt 71 on the innermost side in the tire radial direction of the belt layer 7 and the carcass layer 6 are greatly compressed and deformed when touched. For this reason, like this pneumatic tire, the steel reinforcing layer 9 is made 15% of the effective belt width W from the outer end in the tire width direction of the effective belt width W of the belt layer 7 toward the inner side in the tire width direction. The tread surface 21 is further formed to complement the compression rigidity of the belt layer 7 by forming it in a range including at least the region W1 and disposing the belt layer 7 between the innermost belt 71 in the tire radial direction and the carcass layer 6. It becomes possible to suppress wear of the shoulder region GS.

  Moreover, in the pneumatic tire of the present embodiment, as shown in FIGS. 8 to 10, the steel reinforcing layer is disposed apart in the tire width direction across the tire equatorial plane, and has a total width in the tire width direction. It is preferably formed in a range W3 of 30 [%] to 50 [%] of the effective belt width W.

  In order to suppress wear of the shoulder region GS of the tread surface 21, the steel reinforcing layer 9 only needs to be formed in the region W1 of at least 15% of the effective belt width W. Therefore, in order to suppress an increase in rolling resistance due to an increase in mass, the steel reinforcing layer 9 is preferably configured as described above.

In the pneumatic tire of the present embodiment, the steel reinforcing layer 9 has a product of one cross-sectional area of the steel cord and the number of driven portions per 50 [mm] of 4.0 [mm ² ] or more and 7.0. [Mm ² ] or less and the strength is preferably 3200 [MPa].

When the product of the cross-sectional area of one steel cord and the number of driven wires per 50 [mm] is less than 4.0 [mm ² ], it is difficult to secure the compression rigidity of the steel reinforcing layer 9 and the vicinity of the steel reinforcing layer 9 Suppression of deformation becomes insufficient, and the rolling resistance tends to increase. On the other hand, when the product of the cross-sectional area of one steel cord and the number of driven wires per 50 [mm] exceeds 7.0 [mm ² ], the compression rigidity of the steel reinforcing layer 9 tends to be too high, and the cornering power is increased. Impact may occur. Therefore, by setting it as the said range, it becomes possible to suppress the increase in rolling resistance and to reduce the influence on cornering power. Note that the product of the cross-sectional area of one steel cord and the number of driven wires per 50 [mm] is 6.0 [mm ² ] or more in order to prevent an increase in rolling resistance and influence on cornering power. It is preferable to be within a range of 0.0 [mm ² ] or less.

  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 profiles of the steel reinforcing layer 9 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.

  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 obtain the effect of improving the wear resistance of the center region GC 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. 11 to 18).

  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 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.

  11 to 18, the pneumatic tires of Conventional Examples 1 to 3 are the pneumatic tires of Patent Document 1 (Japanese Patent Application No. 2008-307948), and the pneumatic tires of Conventional Examples 1 and 2 are used. The tire had an internal pressure of 230 [kPa], and the pneumatic tire of Conventional Example 3 had an internal pressure of 300 [kPa].

  In FIG. 11, the pneumatic tires of Comparative Example 1 and Comparative Example 2 have a prescribed steel reinforcing layer, but θ in the tread surface profile is out of the prescribed range. On the other hand, the pneumatic tires of Examples 1 to 9 had a prescribed steel reinforcing layer, had a tread surface profile within a prescribed range, and varied θ. The pneumatic tire of this performance test has an aspect 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. 12, the pneumatic tires of Comparative Example 3 and Comparative Example 4 have a prescribed steel reinforcing layer, but Rc / Rs in the tread surface profile was out of the prescribed range. On the other hand, the pneumatic tires of Examples 10 to 17 had a prescribed steel reinforcing layer, had a tread surface profile within a prescribed range, and varied Rc / Rs.

  In FIG. 13, the pneumatic tires of Comparative Example 5 and Comparative Example 6 have a prescribed steel reinforcing layer, but L / (TDW / 2) in the profile of the tread surface is out of the prescribed range. . On the other hand, the pneumatic tires of Examples 18 to 26 had a prescribed steel reinforcing layer, had a tread surface profile within a prescribed range, and varied L / (TDW / 2).

  In FIG. 14, the pneumatic tires of Comparative Example 7 and Comparative Example 8 have a tread surface profile within a specified range, but do not have a specified steel reinforcing layer. On the other hand, the pneumatic tires of Example 27 to Example 31 had a specified steel reinforcing layer between the belt layer and the carcass layer, and had a tread surface profile within a specified range.

  In FIG. 15, the pneumatic tires of Comparative Example 9 and Comparative Example 10 have a tread surface profile within a specified range, but do not have a specified steel reinforcing layer. On the other hand, the pneumatic tires of Examples 32 to 35 had a prescribed steel reinforcing layer divided across the tire equatorial plane, and had a tread surface profile within a prescribed range.

  In FIG. 16, the pneumatic tire of Comparative Example 11 has a tread surface profile within a specified range, but does not have a specified steel reinforcing layer. On the other hand, the pneumatic tires of Examples 36 to 40 have a steel reinforcing layer having a specified steel reinforcing layer, a tread surface profile within a specified range, and a steel cord having a steel cord having a strength of 3200 [MPa]. The product of the cross-sectional area of the cord and the number of driven cords was changed.

  In FIG. 17, the pneumatic tire of Comparative Example 12 has a tread surface profile in a specified range, but does not have a specified steel reinforcing layer. On the other hand, the pneumatic tires of Examples 41 to 45 had a prescribed steel reinforcing layer, had a tread surface profile in a prescribed range, and varied TDW / SW.

  In FIG. 18, the pneumatic tire of Comparative Example 13 has an internal pressure of 300 [kPa] and has a tread surface profile within a specified range, but does not have a specified steel reinforcing layer. On the other hand, the pneumatic tires of Example 46 to Example 51 had an internal pressure of 300 [kPa], had a prescribed steel reinforcing layer, and had a tread surface profile in a prescribed range.

  As shown in the test results of FIGS. 11 to 18, it can be seen that the pneumatic tires of Examples 1 to 51 have improved wear life, shoulder wear, 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 3 Shoulder portion 6 Carcass layer 7 Belt layers 71, 72 Belt 9 Steel reinforcement layer CC Center crown CL Tire equatorial plane (tire equatorial line) )
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 TDW Tread development width W Effective belt width β Flatness θ Angle

Claims (4)

A carcass layer and a belt layer disposed on the outer side in the tire radial direction of the carcass layer, and a steel cord substantially 90 degrees in the tire circumferential direction on the outer side in the tire radial direction of the carcass layer. The steel reinforcing layer is further provided in parallel in the circumferential direction, and the steel reinforcing layer has an effective belt width of 15 from the outer end in the tire width direction of the effective belt width of the belt layer toward the inner side in the tire width direction. A pneumatic tire formed in a continuous range in the tire width direction including the area of [%] and the position of the tire equatorial plane ;
Further, the tread surface of the tread portion is formed by 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 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 a virtual extension line of the side arc of the tire 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 The angle formed by a straight line passing through the crown and parallel to the tire width direction is θ, the radius of curvature of the central arc is Rc, and the curvature of the shoulder-side arc is Let Rs be the diameter, and let L be the reference development width that is the arc length from the tire equatorial plane to the inner edge position of the shoulder-side arc in the tire width direction, the reference passing through the reference point and parallel to the tire equatorial plane When the tread development width, which is the arc length in the tire width direction between the points where the line intersects 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
A pneumatic tire characterized by being applied to a pneumatic tire for passenger cars having a high internal pressure of 280 [kPa] to 350 [kPa] .   2. The pneumatic tire according to claim 1, wherein the steel reinforcing layer is disposed between a belt radially innermost belt of the belt layer and the carcass layer. The steel reinforcing layer has a product of one cross-sectional area of the steel cord and the number of driven portions per 50 [mm] of 4.0 [mm ² ] or more and 7.0 [mm ² ] or less, and has a strength. the pneumatic tire according to claim 1 or 2, characterized in that it is 3200 [MPa]. The pneumatic tire according to any one of claims 1 to 3 , wherein when the tire cross-sectional width is SW, the tire is formed so as to satisfy 0.55≤TDW / SW≤0.75.

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