JP5976989B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can improve the wear resistance of a center region while maintaining the wear resistance of a shoulder region under a high internal pressure condition.

  In recent years, it has been studied to reduce the rolling resistance of a tire and realize fuel efficiency reduction of a vehicle by increasing the working air pressure of the tire. However, when the internal pressure of the tire is increased, the contact pressure in the center area of the tread portion is increased and the friction energy at the time of tire rolling is increased. As a result, the center region is likely to wear, and the wear resistance of the center region may be reduced.

  Here, in order to reduce the contact pressure in the center region, it is effective to reduce the amount of depression of the tread shoulder region. However, if the amount of depression of the shoulder region is reduced, the contact pressure is concentrated on the shoulder region, and the wear resistance of the shoulder region may be reduced.

  The technique described in patent document 1 is known for the conventional pneumatic tire regarding such a subject.

JP 2008-307948 A

  An object of the present invention is to provide a pneumatic tire capable of improving the wear resistance of a center region while maintaining the wear resistance of a shoulder region under a high internal pressure condition.

In order to achieve the above object, a pneumatic tire according to the present invention is a tire for a passenger car used at an internal pressure exceeding 260 [kPa], and includes a carcass layer, a belt layer, and a belt reinforcing layer, The carcass layer is configured by arranging a carcass cord made of organic fibers at an angle of 90 ° ± 5 ° with respect to the tire circumferential direction, and the belt layer has a cord made of steel or organic fibers with respect to the tire circumferential direction. The belt includes at least two layers of belts arranged side by side at an angle of 20 degrees to 30 degrees, and the two layers of the belts are stacked with the cord angles intersecting each other to have a multilayer structure and the carcass layer The belt reinforcing layer is disposed on the outer side of the tire in the tire radial direction, and is formed by arranging a cord made of steel or organic fiber at an angle of ± 5 degrees with respect to the tire circumferential direction. Are arranged on the outer side of the belt layer in the tire radial direction and are located at the center of the tire in the width direction of the tire, the side of the tread at the outermost side of the tire in the width direction of the tire, and the tire width of the arc of the center In a pneumatic tire formed of an arc having a plurality of different radii of curvature including at least a first shoulder-side arc continuous in the direction outer side and a second shoulder-side arc continuous in the tire width direction of the side portion arc, In a state in which 5% of the normal internal pressure is incorporated into the normal rim and filled with the internal pressure, the virtual extension line of the first shoulder side arc and the side portion arc (21d) are seen in a sectional view in the tire meridian direction. The intersection point with the virtual extension line is defined as a reference point P, the intersection point between the tire equatorial plane and the profile of the tread surface is defined as a center crown, and the reference point and the center crown are defined as An 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 curvature radius of the central arc is Rc, the curvature radius of the shoulder-side arc is Rs, A reference developed width that is an arc length from the tire equator plane to the inner end position of the first shoulder side arc in the tire width direction is L, and a reference line that passes through the reference point and is parallel to the tire equator plane is The tread surface has a width of 0.025 × β + 1.0 ≦ θ ≦ 0, where TDW is the tread developed width, which is the arc length in the tire width direction between points intersecting the tread surface, and the flatness ratio is β. 0.045 × β + 2.5 20 ≦ Rc / Rs ≦ 50 0.2 ≦ L / (TDW / 2) ≦ 0.7, and a belt reinforcing layer disposed outside the belt layer in the tire radial direction Comprising the shoulder A on the side arc to the position of the point Q of 85 [%] of the tread half width TDW / 2 from the equatorial plane of the tire constituting said perpendicular line drawn to the shoulder-side arc from the point Q belt reinforcing layer cord The distance ts between the point Q and the point R is in the range of 4.0 [mm] ≦ ts ≦ 8.0 [mm] when the intersection point with the outer surface in the tire radial direction is the point R.

  In this pneumatic tire, (1) the amount of depression of the tread shoulder region (angle θ) and the radius-of-curvature ratio Rc / Rs between the center region and the shoulder region are optimized. The relationship with the ground pressure is optimized. Thereby, there is an advantage that the wear resistance of the center region can be improved while maintaining the wear resistance of the shoulder region. Further, (2) since the tread gauge (distance ts) in the shoulder region is optimized, there is an advantage that the cornering power of the tire can be further improved while appropriately maintaining the wear resistance of the shoulder region.

  In the pneumatic tire according to the present invention, a region from the tire equator surface to a position of 70 [%] of the tread deployment half width TDW / 2 is referred to as a center region, and 70 of the tread deployment half width TDW / 2. When the region from the position [%] to the position 90 [%] is referred to as a shoulder region, the groove depth gs of the groove having the maximum groove depth in the shoulder region is 0.5 [mm] ≦ gs ≦ 2. Within the range of 0.0 [mm].

  In this pneumatic tire, since the sub-groove gauge gs is optimized, there is an advantage that the cornering power of the tire can be further improved while appropriately maintaining the wear resistance of the shoulder region.

  In the pneumatic tire according to the present invention, the tread rubber of the tread portion includes a cap tread rubber layer that constitutes a tread surface of the tire, and an under tread rubber layer that is disposed on the inner side in the tire radial direction of the cap tread rubber layer. , JIS hardness Hs at 20 [° C.] of the undertread rubber layer is in the range of 67 ≦ Hs ≦ 78.

  In this pneumatic tire, there is an advantage that the cornering power of the tire is further improved by disposing an under tread rubber layer having a high JIS hardness Hs.

Further , in the pneumatic tire according to the present invention, the belt reinforcing layer is composed of at least two laminated reinforcing layers, and the reinforcing layer on the outer side in the tire radial direction is only at an end in the tire width direction of the belt layer. It arrange | positions and covers the tire width direction edge part of the said belt layer.

  The pneumatic tire according to the present invention has an advantage that the wear resistance of the center region can be improved while maintaining the wear resistance of the shoulder region under high internal pressure conditions.

FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view illustrating a tread gauge of the pneumatic tire illustrated in FIG. 1. FIG. 3 is a tread plan view showing the pneumatic tire depicted in FIG. 1. 4 is an enlarged cross-sectional view showing a sub-groove gauge of the pneumatic tire shown in FIG. FIG. 5 is a sectional view in the tire meridian direction showing a modification of the pneumatic tire depicted in FIG. 1. FIG. 6 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 7 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 8 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 9 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 10 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 11 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 12 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. FIG. 13 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view illustrating a tread gauge of the pneumatic tire illustrated in FIG. 1.

  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 plane) 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 1. The tire width is the width in the tire width direction between the portions located outside in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane CL in the tire width direction. The tire equator plane refers to a line on the tire equator plane CL along the circumferential direction of the pneumatic tire 1. In the present embodiment, the same sign “CL” as that of the tire equator plane is attached to the tire equator plane. In addition, since the pneumatic tire 1 described below is configured to be substantially symmetric about the tire equator plane CL, the pneumatic tire 1 is cut along a plane passing through the rotation axis of the pneumatic tire 1. In the meridional sectional view (FIG. 1), only one side (right side in FIG. 1) centered on the tire equatorial plane CL is illustrated and only one side is described, and the other side (left side in FIG. 1). Description of is omitted.

  The pneumatic tire 1 of the present embodiment has a tread portion 2 as shown in FIG. The tread portion 2 is made of a rubber material (tread rubber), is exposed at the outermost side in the tire radial direction of the pneumatic tire 1, and the surface thereof is the contour of the pneumatic tire 1. The surface of the tread portion 2 is formed as a tread surface 21 that is a surface that comes into contact with the road surface when a vehicle (not shown) on which the pneumatic tire 1 is mounted travels.

  The tread surface 21 has a land portion formed by a plurality of grooves. As an example, in the pneumatic tire 1 of the present embodiment, the tread surface 21 is provided with a plurality of vertical grooves 22 extending along the tire circumferential direction, as shown in FIGS. 1 and 2. The longitudinal groove 22 in the present embodiment includes four circumferential main grooves 22 a provided on the tread surface 21 and two circumferential narrow grooves 22 b provided on the tread surface 21. The tread surface 21 extends along the tire circumferential direction by a plurality of circumferential main grooves 22a, and a plurality of rib-like land portions 23 parallel to the tire equator surface CL are formed. In the present embodiment, five land portions 23 are provided on the tread surface 21 with the circumferential main groove 22a as a boundary, and the first land portion 23a disposed on the tire equator surface CL and the first land portion 23a. A second land portion 23b disposed on the outer side in the tire width direction; and a third land portion 23c disposed on the outermost side in the tire width direction of the tread surface 21 on the outer side in the tire width direction of the second land portion 23b. ing. A circumferential narrow groove 22b is provided in the second land portion 23b.

  Moreover, the tread surface 21 is provided with a lateral groove 24 that intersects the longitudinal groove 22 for each land portion 23 (23a, 23b, 23c). The lateral groove 24 provided in the first land portion 23a is formed as a protruding groove 24a having one end opened in the circumferential main groove 22a and the other end closed, and inclined with respect to the tire width direction and the tire circumferential direction. Yes. The protruding groove 24a is formed so that the inclination direction from the circumferential main groove 22a is opposite to the tire equatorial plane CL.

  Further, the lateral groove 24 provided in the second land portion 23b has one end opened in the circumferential main groove 22a on the outer side in the tire width direction, the other end opened in the circumferential narrow groove 22b, and the tire width direction and the tire circumference. It is formed as an inclined groove 24b that is inclined while being inclined with respect to the direction. The inclined groove 24b is formed so that the inclination direction from the circumferential main groove 22a is opposite to the tire equatorial plane CL.

  Further, the lateral groove 24 provided in the third land portion 23c is curvedly extended from the outermost end in the tire width direction of the tread surface 21 to the inner side in the tire width direction, and the extended end opens into the circumferential main groove 22a. It is formed as an arc groove 24c. The arc groove 24c is formed so that the curve direction is opposite to the tire equatorial plane CL.

  Moreover, the tread surface 21 is provided with sipes 24d and 24e that intersect the tire circumferential direction as the lateral grooves 24 with respect to the second land portion 23b and the third land portion 23c. The sipe 24d provided in the second land portion 23b is curved while being inclined with respect to the tire width direction and the tire circumferential direction, with one end opening in the circumferential main groove 22a on the outer side in the tire width direction and the other end closed. Is formed. The sipe 24d is formed so that the inclination direction from the circumferential main groove 22a is opposite to the tire equatorial plane CL. The sipe 24e provided in the third land portion 23c has one end opened in the circumferential main groove 22a on the outer side in the tire width direction and the other end closed, and is inclined with respect to the tire width direction and the tire circumferential direction. While being curved, it is formed. The sipe 24e is formed so that the inclination direction from the circumferential main groove 22a is opposite to the tire equatorial plane CL.

  Here, the circumferential main groove 22a is a groove extending in the tire circumferential direction with a groove width of 4 mm or more. Moreover, the circumferential direction narrow groove 22b shows the groove | channel extended in the tire circumferential direction whose groove width is less than 4 [mm]. Sipes 24d and 24e indicate grooves that cross the tire circumferential direction with a groove width of 1 mm or less. The protruding grooves 24a, the inclined grooves 24b, and the circular arc grooves 24c are collectively referred to as lug grooves, and indicate grooves that cross the tire circumferential direction with a groove width exceeding 1 [mm] except for the sipes 24d and 24e. In addition, the structure of a groove | channel or a land part is not limited to the example mentioned above, There exist various structures by arrangement | positioning of the vertical groove 22 or the horizontal groove 24. FIG. Although not clearly shown in the figure, the tread surface 21 may have a configuration in which only the lateral groove 24 that is bent or curved in the tire width direction is provided without the longitudinal groove 22.

  The pneumatic tire 1 according to the present embodiment includes a carcass layer 6, a belt layer 7, and a belt reinforcing layer 8.

  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 (not shown), and is wound around in a toroidal shape in the tire circumferential direction. It constitutes. 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.). As shown in FIG. 1, the carcass layer 6 is provided in two layers in the present embodiment, but may be provided in 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.

[Profile structure for high internal pressure]
In recent years, it has been studied to reduce the rolling resistance of a tire and realize fuel efficiency reduction of a vehicle by increasing the working air pressure of the tire. However, when the internal pressure of the tire is increased, the contact pressure in the center area of the tread portion is increased and the friction energy at the time of tire rolling is increased. As a result, the center region is likely to wear, and the wear resistance of the center region may be reduced.

  Here, in order to reduce the contact pressure in the center region, it is effective to reduce the amount of depression (an angle θ described later) in the tread shoulder region. However, if the amount of depression of the shoulder region is reduced, the ground pressure is concentrated on the shoulder region, the wear resistance of the shoulder region is lowered, and the cornering power may be lowered.

  Therefore, in this pneumatic tire 1, the following configuration is adopted in order to improve the wear resistance of the center region while maintaining the wear resistance of the shoulder region under a high internal pressure condition.

  First, 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. 1, the tread surface 21 includes a central arc 21a, a shoulder-side arc 21b, a shoulder region 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 region arc 21c is formed continuously outside the shoulder side arc 21b in the tire width direction. The side portion arc 21d is formed continuously on the outer side in the tire width direction of the shoulder region arc 21c, and is located on the outermost side in the tire width direction of the tread portion 2.

  The virtual extension of the shoulder-side arc 21b in the tire meridian cross-sectional view shown in FIG. 1 in a no-load state in which the pneumatic tire 1 is incorporated in a normal rim and filled with 5% of the normal internal pressure. The intersection point between the line and the virtual extension line of the side arc 21d is defined as a reference point P. The intersection of the tire equatorial plane CL and the profile of the tread surface 21 is a center crown CC, a straight line A connecting the reference point P and the center crown CC, and a straight line passing through the center crown CC and parallel to the tire width direction. The angle formed by B is θ. Further, the radius of curvature of the central arc 21a is Rc. The radius of curvature of the shoulder-side arc 21b is Rs. Further, let L be the reference developed width that is the arc length from the tire equatorial plane CL to the position of the inner end of the shoulder-side arc 21b in the tire width direction. Further, a tread developed width which is an 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 1 of the present embodiment is formed to satisfy the following formulas (1) to (3).
0.025 × β + 1.0 ≦ θ ≦ 0.045 × β + 2.5 (1)
10 ≦ Rc / Rs ≦ 50 (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 cross-sectional height to the cross-sectional width of the tire. The cross-sectional width is a width excluding patterns and characters on the side surface of the tire in a no-load state in which the tire is assembled on a regular rim and filled with a regular internal pressure. The cross-sectional height is ½ of the difference between the outer diameter and the rim diameter of the unloaded tire in which the tire is assembled on the normal rim and filled with the normal internal pressure.

  In the pneumatic tire 1, the amount of depression (angle θ) of the shoulder region is preferably in the range of 0.03 × β + 1.2 ≦ θ ≦ 0.04 × β + 2.3.

  Moreover, it is preferable that the curvature radius ratio Rc / Rs between the center region and the shoulder region is in a range of 12 ≦ Rc / Rs ≦ 30.

  The ratio L / (TDW / 2) between the reference development width L and the tread development half width TDW / 2 is preferably in the range of 0.4 ≦ L / (TDW / 2) ≦ 0.5.

[Tread gauge for shoulder area]
A position Q on the shoulder-side arc 21b (usually the tread contour line) and 85 [%] of the tread development half-width TDW / 2 from the tire equatorial plane CL is defined as a point Q, and from this point Q to the shoulder-side arc 21b. A point R is an intersection of the drawn vertical and the outer side surface of the cord constituting the belt reinforcing layer 8 in the tire radial direction (see FIGS. 1 and 2). At this time, the distance ts between the point Q and the point R is preferably in the range of 4.0 [mm] ≦ ts ≦ 8.0 [mm], 5.5 [mm] ≦ ts ≦ 6.5 [ mm] is more preferable.

  The distance ts is measured in a no-load state in which the tire is incorporated in a normal rim and filled with an internal pressure of 5% of the normal internal pressure, and is generally approximately equal to the tread gauge in the shoulder region. In addition, when the belt reinforcing layer has a multilayer structure formed by laminating a plurality of reinforcing layers, a point R is defined for the reinforcing layer on the outer side in the tire radial direction. Moreover, the tire radial direction outer side surface of the cord constituting the belt reinforcing layer is a plane connecting the tire radial direction outer side points of adjacent cords.

  For example, in this embodiment, the belt reinforcing layer 8 has a two-layer structure in which a pair of reinforcing layers 81 and 82 are laminated (see FIGS. 1 and 2). The reinforcing layer 81 (82) is made of a rolled material obtained by coating a steel or organic fiber cord 811 (821) with cord rubber. Further, the perpendicular drawn from the point Q to the shoulder-side arc 21b does not intersect the cord 811 of the reinforcing layer 81 on the outer side in the tire radial direction. For this reason, a plane connecting the outer side points in the tire radial direction of the adjacent cords 811 and 811 (the outer side surface in the tire radial direction of the cords) is taken, and an intersection of this plane and the perpendicular from the point Q is a point R. The distance ts between the point R and the point Q is a tread gauge for the shoulder region.

  Further, a region from the tire equator surface to a position of 70 [%] of the tread deployment half width TDW / 2 is referred to as a center region, and 90 [%] from the position of 70 [%] of the tread deployment half width TDW / 2. The region up to the position is called a shoulder region (see FIG. 3). At this time, the groove depth gs of the groove having the maximum groove depth in the shoulder region (for example, the arc groove 24c of the third land portion 23c) is in the range of 0.5 [mm] ≦ gs ≦ 2.0 [mm]. It is preferable that it exists in the range of 1.0 [mm] <= gs <= 1.5 [mm] (refer FIG. 4).

  The maximum groove depth in the shoulder region refers to the maximum value applied to the groove depths of all the grooves formed in the shoulder region. For example, in this embodiment, the position of 70% of the tread development half width TDW / 2 is slightly outside the edge portion on the circumferential main groove 22a side of the third land portion 23c, and this position is A center region and a shoulder region are partitioned as a boundary (see FIG. 3). For this reason, the groove depth of the arc groove 24c in the third land portion 23c is the maximum groove depth in the shoulder region (see FIG. 1). The sub-groove gauge gs of the arc groove 24c is set within the above range (see FIG. 4).

  Further, depending on the tire specifications, the circumferential main groove 22a that partitions the second land portion 23b and the third land portion 23c may be located in the shoulder region (not shown). In such a case, the groove having the maximum groove depth in the shoulder region is defined by comparing the groove depths of the circumferential main groove 22a and the arc groove 24c. Further, when the lug groove such as the arc groove 24c is not in the shoulder region (not shown), the maximum groove depth is obtained by comparing the groove depths of other grooves (for example, sipe 24e, 24f, see FIG. 3). A groove is defined.

  The sub-groove gauge gs is a distance from the groove bottom to the outer surface of the belt reinforcing layer 8 in a no-load state in which the tire is incorporated in a normal rim and filled with an internal pressure of 5% of the normal internal pressure. Here, this sub-groove gauge gs is measured for the arc groove 24c in the shoulder region (see FIG. 4).

  Moreover, in this pneumatic tire 1, the tread rubber of the tread portion 2 includes a cap tread rubber layer 2A constituting the tread surface of the tire, and an under tread rubber layer disposed on the inner side in the tire radial direction of the cap tread rubber layer 2A. 2B is laminated (see FIG. 5). At this time, the JIS hardness Hs at 20 [° C.] of the under tread rubber layer 2B of the tread portion 2 is preferably in the range of 67 ≦ Hs ≦ 78, and more preferably in the range of 70 ≦ Hs ≦ 75. .

[effect]
As described above, in this pneumatic tire 1, (1) the angle θ, the ratio Rc / Rs between the curvature radius Rc of the center region and the curvature radius Rs of the shoulder region, and the reference deployment width L and the tread deployment half width TDW. / 2 ratio L / (TDW / 2) is 0.025 × β + 1.0 ≦ θ ≦ 0.045 × β + 2.5, 10 ≦ Rc / Rs ≦ 50, and 0.2 ≦ L / (TDW / 2) Within the range of ≦ 0.7. In this configuration, the amount of depression (angle θ) of the tread shoulder region and the radius-of-curvature ratio Rc / Rs between the center region and the shoulder region are optimized, so the relationship between the ground pressure in the center region and the ground pressure in the shoulder region Is optimized. Thereby, there is an advantage that the wear resistance of the center region can be improved while maintaining the wear resistance of the shoulder region. For example, when θ <0.025 × β + 1.0, the wear resistance of the shoulder region deteriorates, and when θ> 0.045 × β + 2.5, the improvement effect on the wear resistance of the center region is small, which is not preferable. . Further, when Rc / Rs <10, the improvement effect on the wear resistance of the center region is small, which is not preferable.

  Further, (2) the position of 85 [%] of the tread deployment half width TDW / 2 from the tire equatorial plane CL on the shoulder side arc 21b is a point Q, and the vertical and belt drawn from this point Q to the shoulder side arc 21b. When the intersection of the cord constituting the reinforcing layer 8 and the outer surface in the tire radial direction is a point R, the distance ts between the point Q and the point R is 4.0 [mm] ≦ ts ≦ 8.0 [mm]. Within range (see FIGS. 1 and 2). In such a configuration, since the tread gauge (distance ts) in the shoulder region is optimized, there is an advantage that the cornering power of the tire can be further improved while appropriately maintaining the wear resistance of the shoulder region.

  Moreover, in this pneumatic tire 1, the groove depth gs of the groove having the maximum groove depth in the shoulder region (for example, the arc groove 24c of the third land portion 23c) is 0.5 [mm] ≦ gs ≦ 2.0. It is in the range of [mm] (see FIG. 3). In such a configuration, since the sub-groove gauge gs is optimized, there is an advantage that the cornering power of the tire can be further improved while maintaining the wear resistance of the shoulder region appropriately. For example, if gs <0.5, the cord of the belt reinforcing layer 8 (reinforcing layer 81) may be damaged because the sub-groove gauge gs is too small, and if gs ≧ 2.0, the cornering power characteristics may be reduced. Since the improvement effect cannot be obtained sufficiently, it is not preferable.

  Further, in the pneumatic tire 1, the JIS hardness Hs at 20 [° C.] of the under tread rubber layer 2B of the tread portion 2 is in the range of 67 ≦ Hs ≦ 78. With such a configuration, there is an advantage that the cornering power of the tire is further improved by disposing the under tread rubber layer 2B having a high JIS hardness Hs. For example, when Hs <67, the effect of improving the cornering power is not sufficiently obtained, and when Hs> 78, the durability of the tire is deteriorated.

[Applicable to]
The pneumatic tire 1 is preferably applied to a tire for a passenger car that is used with an internal pressure exceeding 260 [kPa], more preferably an internal pressure of 280 [kPa] to 350 [kPa]. In passenger car tires that are used under such high internal pressure conditions, the contact pressure in the center area of the tread portion is high, and therefore the wear resistance of the center area tends to decrease. Therefore, by using such a tire as an application target, there is an advantage that the effect of wear resistance can be remarkably obtained.

  In this embodiment, for a plurality of pneumatic tires with different conditions, (1) wear resistance in the center region, (2) wear resistance in the shoulder region, (3) cornering power, and (4) durability. A performance test was conducted (see FIGS. 6 to 13). In these performance tests, a pneumatic tire with a tire size of 215 / 55R17 93V (flatness 55) is assembled to an aluminum wheel with a rim size of 17 × 7J, or a pneumatic tire with a tire size of 245 / 35ZR19 93Y (flatness 35). Is assembled to an aluminum wheel with a rim size of 19 × 81. Further, the maximum load capacity specified by JATMA is given to this pneumatic tire. As a test vehicle, a domestic sedan having a displacement of 3000 [cc] and an FR vehicle is used.

  In a performance test regarding (1) wear resistance in the center area (center wear) and (2) wear resistance in the shoulder area (shoulder wear), a test vehicle equipped with pneumatic tires has a predetermined paved road of 10,000 [km]. The remaining groove amount of the groove having the maximum groove depth dc in the center region and the remaining groove amount of the groove having the maximum groove depth ds in the shoulder region are measured. Based on this measurement result, index evaluation is performed with the conventional example 2 as a reference (100). This evaluation is preferable as the numerical value increases. The wear resistance of the center region is determined to be superior at 103 or higher, and if the wear resistance of the shoulder region is 100 or higher, it is determined that the wear resistance is maintained at an appropriate level.

  (3) In the performance test concerning cornering power, the pneumatic tire is filled with the internal pressure shown in FIGS. 6 to 13 and attached to a drum testing machine, and a load of 450 [kg] is applied and 10 [km / h] is applied. The vehicle is run at a running speed, and the lateral force when the slip angle is 1 ° to the right and the lateral force when the slip angle is 1 ° to the left are measured. Then, based on the average value of these lateral forces, index evaluation is performed with the conventional example 2 as a reference (100). This evaluation is preferable as the numerical value increases.

(4) In the performance test relating to durability, the pneumatic tire was filled with an internal pressure of 1.4 [kg / cm ² ] and attached to a drum testing machine, and a load of 450 [kg] was applied and 15 km / h. ] Slow ram travel of 2000 [km] at a travel speed of Thereafter, the belt layer portion of the tire is cut out, and the presence or absence of the belt cord is observed. When the belt cord is not broken, a “◯” evaluation is performed, when there is a slight break, a “Δ” evaluation is performed, and when a break is apparent, a “×” evaluation is performed.

  Conventional examples 1 and 2 are tires disclosed in Japanese Patent Application Laid-Open No. 2008-307948. In Conventional Example 1, an internal pressure of 230 [kPa] is applied, and in Conventional Example 2, an internal pressure of 300 [kPa] is applied.

  Examples 1-33 are the pneumatic tire 1 described in FIG. 1, and the internal pressure 300 [kPa] is provided. Further, (1) the angle θ, the ratio Rc / Rs of the curvature radius Rc of the center region and the curvature radius Rs of the shoulder region, and the ratio L / (TDW / 2) of the reference developed width L and the tread developed half width TDW / 2. ) Has been optimized. Further, (2) the tread gauge (distance ts) of the shoulder region is within a predetermined range. Further, the arc groove 24c has the maximum groove depth in the shoulder region, and the sub-groove gauge gs is measured for the arc groove 24c. As described above, the angle θ is set in the range of 0.03 × β + 1.2 ≦ θ ≦ 0.04 × β + 2.3. For example, when the flat rate β is β = 55, the angle θ is 2.375 ≦ θ ≦ 4.975, and when β = 35, the angle θ is 1.875 ≦ θ ≦ 4.075. .

  As shown in the test results, in the pneumatic tires 1 of Examples 1 to 33, it is understood that the wear resistance of the center region can be improved while maintaining the wear resistance of the shoulder region as compared with the conventional examples 1 and 2. . Moreover, it turns out that the cornering power property of a tire improves. Moreover, it turns out that durability of a tire is ensured appropriately (refer FIGS. 6-13).

  Further, comparing Examples 1 to 4 and Comparative Examples 1 and 2, it can be seen that by optimizing the angle θ, the wear resistance of the center region can be improved while maintaining the wear resistance of the shoulder region (see FIG. 6). Moreover, when Examples 5-8 are compared with Comparative Examples 3 and 4, it can be seen that by optimizing the ratio Rc / Rs, the wear resistance of the center region can be improved while maintaining the wear resistance of the shoulder region. (See FIG. 7). Moreover, when Examples 9-12 are compared with Comparative Examples 5 and 6, it can be seen that the wear resistance of the shoulder region can be properly maintained by optimizing the ratio L / (TDW / 2) (see FIG. 8). ).

  Further, when Examples 13 to 16 are compared with Comparative Examples 7 and 8, even when the angle θ is changed by changing the flatness β, the wear resistance of the shoulder region can be improved by optimizing the angle θ. It can be seen that the wear resistance of the center region can be improved while maintaining (see FIG. 9).

  Further, when Examples 17 to 20 and Comparative Examples 9 and 10 are compared, by adjusting the tread gauge (distance ts) of the shoulder region, the cornering power of the tire while appropriately maintaining the wear resistance of the shoulder region. It can be seen that the performance can be improved (see FIG. 10). In addition, when Examples 21 to 26 are compared, the cornering power of the tire can be improved while maintaining the durability of the tire by optimizing the sub-groove gauge gs of the groove having the maximum groove depth in the shoulder region. You can see (see Figure 11). Further, when Examples 27 to 32 are compared, it can be seen that the cornering power of the tire can be improved while maintaining the durability of the tire by optimizing the JIS hardness Hs of the undertread rubber layer 2B (FIG. 12 and FIG. 12). 13).

  As described above, the pneumatic tire according to the present invention is useful in that the wear resistance of the center region can be improved while maintaining the wear resistance of the shoulder region under a high internal pressure condition.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire, 2 tread part, 2B under tread rubber layer, 2A cap tread rubber layer, 21 tread surface, 21a center part arc, 21b shoulder side arc, 21d side part arc, 21c shoulder area arc, 22 vertical groove, 22a Circumferential main groove, 22b circumferential narrow groove, 23 land portion, 23a first land portion, 23c third land portion, 23b second land portion, 24 transverse groove, 24a protrusion groove, 24b inclined groove, 24c arc groove, 24d, 24e sipes, 6 carcass layers, 7 belt layers, 71, 72 belts, 8 belt reinforcing layers, 81, 82 reinforcing layers

Claims (4)

It is a tire for passenger cars used at an internal pressure exceeding 260 [kPa],
A carcass layer; a belt layer; and a belt reinforcing layer, wherein the carcass layer is configured by arranging a carcass cord made of organic fibers at an angle of 90 degrees ± 5 degrees with respect to a tire circumferential direction. Has at least two layers of belts formed by attaching cords made of steel or organic fibers at an angle of 20 degrees to 30 degrees with respect to the tire circumferential direction, and the two layers of belts have the angle of the cords Are laminated with crossing each other and have a multilayer structure, and are arranged on the outer side in the tire radial direction of the carcass layer, and the belt reinforcing layer has an angle of ± 5 degrees with respect to the tire circumferential direction with respect to the cord made of steel or organic fiber. And arranged at the outer side in the tire radial direction of the belt layer,
A central arc positioned at the center in the tire width direction, a side arc positioned at the outermost side in the tire width direction of the tread portion, a first shoulder side arc continuous to the outer side in the tire width direction of the central arc, and the In a pneumatic tire formed of an arc having a plurality of different radii of curvature including at least a second shoulder side arc that is continuous on the inner side in the tire width direction of the side portion arc,
In a state in which 5% of the normal internal pressure is incorporated into the normal rim and filled with the internal pressure, the virtual extension line of the first shoulder side arc and the side portion arc (21d) are seen in a sectional view in the tire meridian direction. The intersection point of the virtual extension line is defined as a reference point P, the intersection point of the tire equator plane and the profile of the tread surface is defined as a center crown, and a straight line connecting the reference point and the center crown passes through the center crown. The angle between the straight line parallel to the tire width direction is θ, the radius of curvature of the central arc is Rc, the radius of curvature of the shoulder side arc is Rs, and the first shoulder side arc from the tire equatorial plane The reference developed width which is the arc length to the inner end position in the tire width direction is L, and the reference line passing through the reference point and parallel to the tire equator plane intersects the tread surface. The tread width is the arc length in the tire width direction and TDW, when the aspect ratio and β in,
The tread surface is
0.025 × β + 1.0 ≦ θ ≦ 0.045 × β + 2.5
20 ≦ Rc / Rs ≦ 50
0.2 ≦ L / (TDW / 2) ≦ 0.7
Formed to meet the
Furthermore, a belt reinforcing layer disposed on the tire radial direction outside of the belt layer is provided,
On the shoulder side arc, the position of 85 [%] of the tread development half width TDW / 2 from the tire equatorial plane is a point Q, and a vertical line drawn from the point Q to the shoulder side arc and the belt reinforcing layer are configured. When the point of intersection with the outer surface of the cord in the tire radial direction is point R,
A pneumatic tire characterized in that a distance ts between the point Q and the point R is in a range of 4.0 [mm] ≦ ts ≦ 8.0 [mm]. A region from the tire equator surface to a position of 70 [%] of the tread deployment half width TDW / 2 is referred to as a center region, and 90% from a position of 70 [%] of the tread deployment half width TDW / 2. When the area up to the position is called the shoulder area,
The pneumatic tire according to claim 1, wherein a sub-groove gauge gs of a groove having the maximum groove depth in the shoulder region is in a range of 0.5 [mm] ≤ gs ≤ 2.0 [mm]. When the tread rubber of the tread portion is formed by laminating a cap tread rubber layer constituting a tread surface of a tire and an under tread rubber layer disposed on the inner side in the tire radial direction of the cap tread rubber layer,
3. The pneumatic tire according to claim 1, wherein a JIS hardness Hs at 20 [° C.] of the undertread rubber layer is in a range of 67 ≦ Hs ≦ 78. The belt reinforcing layer is composed of at least two laminated reinforcing layers,
The pneumatic according to any one of claims 1 to 3, wherein the reinforcing layer on the outer side in the tire radial direction is disposed only at an end portion in the tire width direction of the belt layer and covers the end portion in the tire width direction of the belt layer. tire.

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