JP5321103B2 - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire increased in wear resistance while maintaining high drainage property. <P>SOLUTION: This pneumatic tire has, in a tread part 2, a plurality of main grooves 22 extending in the circumferential direction of the tire. The pneumatic tire satisfies the requirement 0.3(TW/2)&le;L0&le;0.6(TW/2) when a tire ground-contact width is TW and the length of the tire in the tire width direction from the side wall 22ba of the second main groove 22b on the outer side of the tire in the tire width direction to the equator C of the tire on the outermost side of the tire in the tire width direction is L0. A belt layer 7 is provided to the tire radial outer side of a carcass 6, and a belt reinforcement layer 8 is provided to the tire radial outer side of the belt layer 7. The belt reinforcement layer 8 is configured in such a manner that the ratio Ec/Es of the tension rigidity exponent Ec in the center area Lc in the tire width direction to the tension rigidity exponent Es in the outer area Ls of the tire in the tire width direction satisfies the requirement 1.0&le;Ec/Es. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a pneumatic tire suitable as a tire mounted on a general passenger car.

  In conventional pneumatic tires, the improvement of drainage is an important factor to ensure running stability on road surfaces wet with rain, etc., so the main groove generally formed along the tire circumferential direction By improving the drainage, the drainage is improved.

  For example, in the pneumatic tire described in Patent Document 1, a range of 50% of the tire ground contact width from the tire equator line on the tread surface to both outer sides in the tire width direction is a tire ground contact central region. Some have a plurality of main grooves extending along the circumferential direction.

Japanese Patent No. 3667261

  In the conventional pneumatic tire described in Patent Document 1 described above, the drainage can be improved by the main groove. However, in this pneumatic tire, since the main groove is arranged in the tire ground contact central region, the interval between the main grooves becomes narrow. For this reason, in the land portion formed between the main grooves and extending in the tire circumferential direction, the tire width direction dimension of the land portion in the tire ground contact central region is narrowed, so that the rigidity is lowered. As a result, in the tire contact area, the center part in the tire width direction is long in the tire circumferential direction, the wear energy in the center part in the tire width direction is increased, and center wear (wear near the tire equator line) occurs. It tends to be easy to do.

  The present invention is intended to solve such problems, and an object thereof is to provide a pneumatic tire that can improve wear resistance while maintaining high drainage.

In order to achieve the above object, in the pneumatic tire according to the present invention, the tread portion is provided with a plurality of main grooves extending in the tire circumferential direction, the tire ground contact width is TW, and the main groove on the outermost side in the tire width direction A pneumatic tire that satisfies the condition of 0.3 (TW / 2) ≦ L0 ≦ 0.6 (TW / 2), where L0 is the length in the tire width direction from the outer side wall in the tire width direction to the tire equator line A belt layer is provided on the outer side in the tire radial direction of the carcass, and further a belt reinforcing layer is provided on the outer side in the tire radial direction of the belt layer, and the belt reinforcing layer is pulled in the center region in the tire width direction. The ratio Ec / Es between the stiffness index Ec and the tensile stiffness index Es in the outer region in the tire width direction satisfies the condition of 1.2 ≦ Ec / Es ≦ 4.0 .

According to this pneumatic tire, the restraining force of the belt reinforcing layer in the center region in the tire width direction is increased. For this reason, it is a pneumatic condition that satisfies the condition of 0.3 (TW / 2) ≦ L0 ≦ 0.6 (TW / 2) so that the main groove is provided at a position close to the tire equator line side and has high drainage performance. Even in the case of a tire, it is possible to prevent a situation where the contact length of a land portion arranged in the vicinity of the tire equator line becomes long, and to make the contact length in the tire circumferential direction of each land portion uniform. As a result, since center wear is suppressed, it is possible to improve wear resistance while maintaining high drainage. In addition, according to this pneumatic tire, by defining the range of the ratio Ec / Es of the tensile stiffness index, the center wear can be appropriately suppressed, so that the wear resistance is improved while maintaining high drainage. it can.

  In the pneumatic tire of the present invention, the tire width direction central region Lc is set in a range of 0.5 ≦ Lc / L0 ≦ 1.1.

  According to this pneumatic tire, by defining the center region Lc in the tire width direction, the pneumatic tire is applied to the pneumatic tire that satisfies the condition of 0.3 (TW / 2) ≦ L0 ≦ 0.6 (TW / 2). Since wear can be appropriately controlled, wear resistance can be improved while maintaining high drainage.

  In the pneumatic tire according to the present invention, the land portion defined by the main groove in the tread portion is a rib-like land portion extending in the tire circumferential direction.

  It is suitable for pneumatic tires that satisfy the condition of 0.3 (TW / 2) ≦ L0 ≦ 0.6 (TW / 2) so that the main groove is provided at a position close to the tire equator line side and has high drainage. Therefore, the rigidity of the rib-like land portion close to the tire equator line tends to decrease. Therefore, according to this pneumatic tire, by using a pneumatic tire having a rib-like land portion as an application target, there is an advantage that the effect of improving wear resistance can be obtained more significantly while maintaining high drainage. is there.

  The pneumatic tire according to the present invention is provided with wear resistance while maintaining high drainage even if the main groove is provided at a position close to the tire equator line and the tread pattern is configured to have high drainage. Can be improved.

  Embodiments of a pneumatic tire according to 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 plan view showing a tread portion of a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is a meridional sectional view of the pneumatic tire shown in FIG.

  In the following description, the tire width direction refers to a direction parallel to the rotation axis (not shown) of the pneumatic tire 1, and the inner side in the tire width direction refers to the tire equator plane (tire equator line) C in the tire width direction. The heading direction and the outer side in the tire width direction refer to the side away from the tire equatorial plane C in the tire width direction. The tire circumferential direction is a circumferential direction with the rotation axis as a central axis. Further, the tire radial direction refers to a direction orthogonal to the rotation axis, the tire radial inner side is the side toward the rotation axis in the tire radial direction, and the tire radial direction outer side is the side away from the rotation axis in the tire radial direction. Say.

  The pneumatic tire 1 described below is configured to be substantially symmetric with respect to the tire equatorial plane C. The tire equatorial plane C is a plane that is orthogonal to the rotational axis of the pneumatic tire 1 and passes through the center of the tire width of the pneumatic tire 1. The tire width is the width in the tire width direction between the portions located outside in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane C in the tire width direction. The tire equator line is a line on the tire equator plane C and along the circumferential direction of the pneumatic tire. In the present embodiment, the same sign “C” as that of the tire equator plane is attached to the tire equator line. Since the pneumatic tire 1 described below is configured to be substantially symmetric about the tire equatorial plane C, 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. 2), only one side (right side in FIG. 2) centering on the tire equatorial plane C is illustrated and only one side is described, and the other side (left side in FIG. 2). Description of is omitted.

  First, the pattern of the pneumatic tire 1 will be described. The pneumatic tire 1 of the present embodiment is suitable as a tire that is mounted on a general passenger car. The pneumatic tire 1 has a tread portion 2 as shown in FIGS. The tread portion 2 is made of a rubber material and 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 is provided with a pair of tire contact width ends T at predetermined positions on both outer sides in the tire width direction, and an interval in the tire width direction between the tire contact width ends T is set as a tire contact width TW. ing.

  Here, the tire ground contact width TW is the tread of the pneumatic tire 1 when the pneumatic tire 1 is assembled on a regular rim and filled with a regular internal pressure (for example, 230 KPa) and 70% of the regular load is applied. This is the maximum width in the tire width direction of the tire contact area where the surface 21 is in contact with the road surface. Further, the tire contact width end T refers to both outermost ends in the tire width direction of the tire contact area, and in FIG. 1, the tire contact width end T is continuously illustrated in the tire circumferential direction.

  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 normal load is “maximum load capacity” defined by JATMA, a maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  Further, the pneumatic tire 1 of the present embodiment is provided with a plurality of main grooves 22 that are straight main grooves extending in the tire circumferential direction and parallel to the tire equator line C on the tread surface 21. In the present embodiment, four main grooves 22 are provided on the tread surface 21, and a first main groove 22a disposed closest to the tire equator line C and a second main groove disposed on the outermost side in the tire width direction. 22b. A plurality of rib-like land portions 23 extending along the tire circumferential direction and parallel to the tire equator line C are formed on the tread surface 21 by the plurality of main grooves 22. In the present embodiment, five land portions 23 are provided on the tread surface 21, and the first land portions 23a disposed on the tire equator line C between the first main grooves 22a, the first main grooves 22a, The second land portion 23b disposed on the outer side in the tire width direction from the first land portion 23a between the second main groove 22b and the tire width of the tread surface 21 on the outer side in the tire width direction of the second main groove 22b. And a third land portion 23c disposed on the outermost side in the direction.

  Further, on the tread surface 21, a plurality of protruding grooves 24 communicating with the first main groove 22a are provided at predetermined intervals in the tire circumferential direction on the first land portion 23a on the inner side in the tire width direction of each first main groove 22a. It has been. The projecting grooves 24 are opposed to each other with the tire equator line C therebetween, and the projecting grooves 24 facing each other are not communicated with each other and are spaced apart. Furthermore, the protruding groove 24 is inclined with respect to the tire width direction, and the inclined direction is provided in the opposite direction between the protruding grooves 24. In the tread surface 21, a plurality of inclined grooves 25 communicating with the second main groove 22b are provided at predetermined intervals in the tire circumferential direction on the second land portion 23b on the inner side in the tire width direction of each second main groove 22b. It has been. The inclined groove 25 is provided so as not to communicate with the first main groove 22a. Further, the inclined groove 25 is inclined with respect to the tire width direction, and the inclined direction is provided in the opposite direction between the inclined grooves 25 facing each other across the tire equator line C.

  In the pneumatic tire 1 of the present embodiment having such a pattern, the tire from the tire width direction outer side wall 22ba to the tire equator line C of the second main groove 22b which is the main groove located on the outermost side in the tire width direction. When the length in the width direction is L0, the relationship between this L0 and the tire ground contact width TW satisfies the condition of 0.3 (TW / 2) ≦ L0 ≦ 0.6 (TW / 2). The side wall 22ba on the outer side in the tire width direction of the second main groove 22b refers to the position in the tire width direction at the opening of the second main groove 22b. In addition, the groove width (tire width direction width) of the 1st main groove 22a and the 2nd main groove 22b is set to the range of 5 mm or more and 20 mm or less. The groove width of the second main groove 22b is formed to be larger than the groove width of the first main groove 22a in a range of 1.05 times to 1.4 times the groove width of the first main groove 22a. .

  According to the pneumatic tire 1, by setting the relationship between the tire width direction length L0 from the side wall 22ba on the tire width direction outer side of the second main groove 22b to the tire equator line C and the tire ground contact width TW, Compared to a general pneumatic tire for passenger cars, the second main groove 22b is provided at a position closer to the tire equator line C side. For this reason, while improving drainage, it becomes possible to reduce medium frequency road noise (200 Hz-300 Hz). The relationship between L0 and the tire ground contact width TW is in the range of 0.33 (TW / 2) ≦ L0 ≦ 0.55 (TW / 2), which improves drainage and reduces medium frequency road noise. It is preferable in terms of reduction.

  Further, in the pneumatic tire 1 of the present embodiment, the third land portion 23c disposed between the second main groove 22b and the tire ground contact width end T and on the outermost side in the tire width direction of the tread surface 21 is provided. A plurality of first lug grooves 26 and second lug grooves 27 extending in the tire width direction are alternately provided in the tire circumferential direction. The first lug groove 26 is provided such that one end portion 26a communicates with the second main groove 22b located on the outermost side in the tire width direction, and the other end portion 26b does not communicate (intersect) with the tire ground contact width end T. Yes. Further, the first lug groove 26 has a shape curved in the tire circumferential direction. The second lug groove 27 is cut so that one end portion 27a does not communicate with the second main groove 22b located on the outermost side in the tire width direction, and the other end portion 27b communicates (crosses) with the tire ground contact width end T. It has been. Further, the second lug groove 27 is curved in the same tire circumferential direction as the first lug groove 26. The first lug groove 26 and the second lug groove 27 are curved in the opposite direction on one side in the tire width direction (right side in FIG. 1) and on the other side in the tire width direction (left side in FIG. 1). It has become. The first lug groove 26 and the second lug groove 27 are provided with a gap between the end portions (the other end portion 26b of the first lug groove 26 and the one end portion 27a of the second lug groove 27) so as to be separated from each other. ing.

  In the pneumatic tire 1, the length in the tire width direction from the other end portion 26b of the first lug groove 26 to the tire contact width end T is L1, and the second main groove 22b extends from the side wall 22ba on the outer side in the tire width direction to the second. When the length in the tire width direction to the one end portion 27a of the lug groove 27 is L2, and the tire width direction length LW from the side wall 22ba on the outer side in the tire width direction of the second main groove 22b to the tire ground contact width end T is these lengths. The relationship between the lengths L1 and L2 and the length LW is 0.1 ≦ L1 / LW ≦ 0.45, which satisfies the condition of 0.1 ≦ L2 / LW ≦ 0.45. And the other end part 26b of the 1st lug groove 26 and the one end part 27a of the 2nd lug groove 27 overlap in the tire width direction, and the overlap allowance L3 is provided.

  According to the pneumatic tire 1, in the pneumatic tire 1 in which the second main groove 22b is provided at a position close to the tire equator line C side, the drainage performance is maintained by the overlap margin L3 of the lug grooves 26 and 27. Driving stability can be improved. In addition, since the lug grooves 26 and 27 are formed so as not to communicate with each other, air column resonance noise generated in the second main groove 22b is transmitted from the lug groove to the outside as high-frequency road noise (800 Hz to 1 kHz). Therefore, noise can be suppressed and quietness can be improved. It should be noted that the relationship between the lengths L1, L2 and the length LW is 0.3 ≦ L1 / LW ≦ 0.4, and is in the range of 0.2 ≦ L2 / LW ≦ 0.4. It is preferable for improving the high frequency road noise.

  Further, in the pneumatic tire 1 of the present embodiment, the overlap margin L3 between the first lug groove 26 and the second lug groove 27 is the tire ground contact width end T from the side wall 22ba on the outer side in the tire width direction of the second main groove 22b. Is set to 10% or more of the tire width direction length LW. For this reason, it becomes possible to ensure the overlap allowance L3 which improves drainage. The overlap margin L3 is preferably 80% or less of the LW in order to suppress noise.

  In addition, the groove width of the 1st lug groove 26 and the 2nd lug groove 27 is set to 1.5 mm or more and 8.0 mm or less, Preferably, it is good to set it to 1.8 mm or more and 4.0 mm or less. The groove width of the second lug groove 27 is formed larger than the groove width of the first lug groove 26. That is, it is possible to suppress the deterioration of pattern noise by narrowing the groove width of the first lug groove 26 and to improve drainage performance by increasing the groove width of the second lug groove 27. Specifically, if the groove width of the second lug groove 27 is set to be not less than 1.2 times and not more than 2.5 times the groove width of the first lug groove 26, pattern noise is ensured while ensuring sufficient drainage. It becomes possible to suppress the deterioration of.

  Moreover, the 1st lug groove 26 and the 2nd lug groove 27 are provided in the range of 45 to 90 in 1 round of a tire circumferential direction. In this case, the pitch length of the first lug groove 26 itself, the pitch length of the second lug groove 27 itself, or the pitch length of the first lug groove 26 and the second lug groove 27 may be changed. That is, it is preferable to employ a pitch variation structure with respect to the arrangement in the circumferential direction of the first lug groove 26 and the second lug groove 27. Thereby, there is an advantage that the pattern noise is reduced and the noise performance of the tire is improved.

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

  The shoulder portion 3 is a portion on both outer sides in the tire width direction of the tread portion 2. Further, the sidewall portion 4 is exposed at the outermost side in the tire width direction of the pneumatic tire 1. 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 disposed in a space formed by folding the end of the carcass 6 outward in the tire width direction at the position of the bead core 51.

  The carcass 6 is configured such that each tire width direction end portion is folded with respect to the pair of bead portions 5 and is wound around in a toroidal shape in the tire circumferential direction to constitute a tire skeleton. The carcass 6 is a carcass cord such as organic fiber (nylon, polyester, rayon, etc.) or steel covered with a rubber material. A plurality of carcass cords are arranged in parallel in the tire circumferential direction while being along the tire meridian direction perpendicular to the tire equator line C of the pneumatic tire 1. It should be noted that the carcass cord has an angle with respect to the tire equator line C (tire circumferential direction) substantially 90 [degrees], and is from -5 [degrees] to +5 [degrees] with respect to 90 degrees with respect to the tire equator line C. Includes range angles. In addition, the carcass 6 is composed of one layer as shown in FIG. 2, but it may have a multilayer structure in order to improve tire rigidity.

  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 6. The tread portion 2 covers the carcass 6 in the tire circumferential direction. The belts 71 and 72 are made of a cord made of organic fiber (nylon, polyester, rayon, etc.) or steel covered with a rubber material, and the cord is at a predetermined angle with respect to the tire circumferential direction, that is, the tire equator line C. Is placed. Further, the belts 71 and 72 are arranged with their cords inclined in opposite directions with respect to the tire equator line C.

  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 is made of an organic fiber (nylon, polyester, rayon, etc.) cord covered with a rubber material, and the cord is substantially at 0 degrees with respect to the tire circumferential direction, that is, the tire equator line C (tire The angle with respect to the circumferential direction is ± 5 [degrees] or less). The belt reinforcing layer 8 is formed by winding a strip (for example, width 10 [mm]) in the tire circumferential direction. The ends of the strip in the tire width direction may be overlapped with each other or may be in contact with each other. The belt reinforcing layer 8 may be composed of one layer. However, in order to further reinforce the end portion of the belt layer 7, it may have a multilayer structure at both ends in the tire width direction.

  In the pneumatic tire 1 of the present embodiment having such a configuration, the belt reinforcing layer 8 has a belt reinforcing layer 81 in the center region in the tire width direction and a belt reinforcing layer 82 in the outer region in the tire width direction. . As shown in FIG. 1, the tire width direction central region is a region Lc that is about 50% of the tire ground contact width TW (TW / 2) on both sides of the tire equator line C in the tire width direction. The outer region is a region Ls obtained by subtracting the center region Lc in the tire width direction from the tire contact width TW. The ratio Ec / Es between the tensile stiffness index Ec in the center region in the tire width direction and the tensile stiffness index Es in the outer region in the tire width direction satisfies the condition of 1.0 ≦ Ec / Es.

  Here, the tensile stiffness index Es is expressed as Ds / Ss. Ds is the number of cords driven per predetermined length (50 [mm]) in the center region in the tire width direction, and Ss is when a load of 50 [N] is applied to one cord in the center region in the tire width direction The elongation rate of [%]. The tensile stiffness index Ec is expressed as Dc / Sc. Dc is the number of cords driven per predetermined length (50 [mm]) in the outer region in the tire width direction, and Sc is a load of 50 [N] applied to one cord in the outer region in the tire width direction The elongation rate of [%].

  Further, in the belt reinforcing layer 8, in order to increase the tensile stiffness index Ec of the belt reinforcing layer 81 in the center region in the tire width direction as compared with the tensile stiffness index Es of the belt reinforcing layer 82 in the outer region in the tire width direction, This can be realized by increasing the number of windings (overlapping amount) of the strip forming the belt reinforcing layer 81 in the central region in the width direction as compared with the strip forming the belt reinforcing layer 82 in the outer region in the tire width direction. Further, it can be realized by increasing the number of cords driven in the strip forming the belt reinforcing layer 81 in the central region in the tire width direction as compared with the strip forming the belt reinforcing layer 82 in the outer region in the tire width direction. Further, the elastic modulus of the strip forming the belt reinforcing layer 81 in the central region in the tire width direction can be realized by making it larger than the strip forming the belt reinforcing layer 82 in the outer region in the tire width direction. Furthermore, it can be realized by laminating a plurality of belt reinforcing layers 8 in the central region in the tire width direction.

  According to the pneumatic tire 1, in the belt reinforcing layer 8, the tensile stiffness index Ec in the center region in the tire width direction is increased as compared with the tensile stiffness index Es in the outer region in the tire width direction. The restraining force of the belt reinforcing layer 8 in the center region in the direction is increased. For this reason, even if the main groove 22 is provided at a position close to the tire equator line C side and the pattern of the tread portion 2 is configured to have high drainage, the pneumatic tire 1 is assembled on the regular rim, In addition, when a normal internal pressure (for example, 230 KPa) is filled and 70% of the normal load is applied, the contact length of the first land portion 23a disposed on the tire equator line C is prevented from being increased. The contact lengths in the tire circumferential direction of 23a, 23b, and 23c can be made uniform. As a result, since center wear can be suppressed, it is possible to improve wear resistance while maintaining high drainage.

  Further, in the pneumatic tire 1 of the present embodiment, the tire width direction central region Lc has a tire width direction length L0 from the tire width direction outer side wall 22ba of the second main groove 22b to the tire equator line C, The range is set to 0.5 ≦ Lc / L0 ≦ 1.1.

  According to the pneumatic tire 1, by defining the tire width direction central region Lc, the condition of 0.3 (TW / 2) ≦ L0 ≦ 0.6 (TW / 2) (preferably 0.33 ( (Tw / 2) ≦ L0 ≦ 0.55 (Tw / 2) range) is applied to the pneumatic tire 1 and center wear can be appropriately suppressed, so that wear resistance is maintained while maintaining high drainage. It becomes possible to improve.

  Further, in the pneumatic tire 1 of the present embodiment, the tensile stiffness index ratio Ec / Es is set in the range of 1.2 ≦ Ec / Es ≦ 4.0.

  When the ratio Ec / Es of the tensile stiffness index is less than 1.2, the effect of suppressing the center wear is small. On the other hand, when the ratio Ec / Es of the tensile stiffness index exceeds 4.0, the restraint force of the belt reinforcing layer 8 in the center region in the tire width direction is too high, so that wear in the outer region in the tire width direction (shoulder wear) ) May occur. According to the pneumatic tire 1, since the center wear can be appropriately suppressed by defining the range of the tensile stiffness index ratio Ec / Es, the wear resistance is improved while maintaining high drainage. It becomes possible.

  Further, in the pneumatic tire 1 of the present embodiment, the land portion 23 defined by the main groove 22 in the tread portion 2 is a rib-like land portion extending in the tire circumferential direction.

  When the main groove 22 is provided at a position close to the tire equator line C and the pattern of the tread portion 2 is configured to have high drainage, the rigidity of the rib-like land portion close to the tire equator line C is likely to be reduced. There is a tendency. Therefore, according to this pneumatic tire 1, by applying the pneumatic tire 1 having a rib-like land portion as an application target, the effect of improving wear resistance can be obtained more significantly while maintaining high drainage. There are advantages.

  FIG. 3 is a chart showing results of performance tests of pneumatic tires according to examples of the present invention, and FIG. 4 is a chart showing cord types of cords of the belt reinforcing layer. In this example, for a plurality of types of pneumatic tires with different conditions, a wear resistance ratio (center wear resistance), a wear amount ratio between a tire width direction central region and a tire width direction outer region, and a performance test on wear life. Was done.

  In this performance test, a pneumatic tire with a tire size of 215 / 55R17 is assembled to a regular rim, filled with regular internal pressure, a regular load is applied, and a rear wheel drive test vehicle (domestic 3.0-liter class sedan-type passenger car) Attached to the driving wheel.

  As for the evaluation method, in terms of the amount of wear, the test vehicle traveled on a paved road surface at 10,000 [km], and after running, applied to the center region in the tire width direction, and the groove depth in each main groove was set at four locations in the tire circumferential direction. The average of the groove depths of all the main grooves is obtained from the sum of the averages of the groove depths to obtain the wear amount Mc in the center region in the tire width direction. Moreover, it covers the outer region in the tire width direction, and the groove depth in the first lug groove is measured at four locations in the tire circumferential direction to obtain an average to obtain the wear amount Ms in the outer region in the tire width direction. Then, the wear amount ratio Ms / Mc is calculated from these wear amounts Mc and Ms. If this evaluation is in the range of 1.0 ≦ Ms / Mc ≦ 1.6, the wear resistance (center wear resistance) is excellent. Also, in the wear life, based on the amount of wear (unit: mm) obtained by running 10,000 [km] on the paved road surface with a test vehicle and measuring the groove depth in each main groove after running. The travelable distance [km] that can be traveled until the remaining groove depth reaches 1.6 mm is calculated, and the wear life is obtained by calculating the average travelable distance of each groove. This evaluation is indicated by an index value with a conventional pneumatic tire as a reference (100), and the larger the index value, the longer the wear life is preferable.

  The pneumatic tires of the conventional example, the comparative example, and the example are provided with four main grooves extending along the tire circumferential direction in the tread portion, and rib-shaped land portions are defined by the main grooves. The relationship between the tire width direction length L0 of the main groove located on the outermost side in the tire width direction to the side wall on the outer side in the tire width direction and the tire ground contact width TW is 0.3 (TW / 2) ≦ L0 ≦ 0.6. A pneumatic tire that satisfies the condition of (TW / 2). Moreover, the code | cord | chord of the code | cord | chord type number shown in FIG. 4 is applied to the cord type of the pneumatic tire of a prior art example, a comparative example, and an Example.

  In the conventional pneumatic tire, the same cord type cord is applied to both the belt reinforcing layer in the center region in the tire width direction and the belt reinforcing layer in the outer region in the tire width direction, and the number of cord ends in each region ( The number of cords driven per predetermined length) is the same, and the tensile stiffness indices Ec and Es are also the same. In the pneumatic tire of Comparative Example 1, the ratio of tensile stiffness index (Ec / Es) is out of specification. In the pneumatic tire of Comparative Example 2, the center region Lc in the tire width direction is not specified. On the other hand, in the pneumatic tires of Examples 1 to 6, the cord type in each region, the number of cord ends in each region, and the tensile stiffness index Ec, Es are optimized, and the ratio of the tensile stiffness index (Ec / Es ) And the center region Lc in the tire width direction are within the specified range.

  As shown in the test results of FIG. 3, in the pneumatic tires of Examples 1 to 6, the wear amounts in the tire width direction central region and the tire width direction outer region, which are wear resistance (center wear resistance), respectively. It can be seen that the ratio and wear life are improved.

  As described above, the pneumatic tire according to the present invention is suitable for improving wear resistance while maintaining high drainage.

It is a top view which shows the tread part of the pneumatic tire concerning embodiment of this invention. FIG. 2 is a meridional sectional view of the pneumatic tire shown in FIG. 1. It is a graph which shows the result of the performance test of the pneumatic tire concerning the Example of this invention. It is a chart which shows the cord type of the cord of a belt reinforcement layer.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 21 Tread surface 22 Main groove 22a First main groove 22b Second main groove 22ba Side wall 23 Land part 23a First land part 23c Third land part 23b Second land part 3 Shoulder part 4 Side wall part 5 Bead portion 6 Carcass 7 Belt layer 8 Belt reinforcing layer 81 Belt reinforcing layer 82 Belt reinforcing layer C Tire equator surface (tire equator line)
T tire contact width edge TW tire contact width Lc tire width direction center region Ls tire width direction outer region Ec tensile stiffness index of tire width direction center region Es tensile strength index of outer region of tire width direction

Claims (3)

The tread portion is provided with a plurality of main grooves extending along the tire circumferential direction, the tire ground contact width is TW, and the tire width direction from the tire width direction outer side wall to the tire equator line in the outermost main groove in the tire width direction When the length is L0, the pneumatic tire satisfies the condition of 0.3 (TW / 2) ≦ L0 ≦ 0.6 (TW / 2),
A belt layer is provided on the outer side in the tire radial direction of the carcass, and a belt reinforcing layer is further provided on the outer side in the tire radial direction of the belt layer.
The belt reinforcing layer has a ratio Ec / Es of the tensile stiffness index Ec in the central region in the tire width direction and the tensile stiffness index Es in the outer region in the tire width direction of 1.2 ≦ Ec / Es ≦ 4.0 . A pneumatic tire characterized by satisfying the conditions.   2. The pneumatic tire according to claim 1, wherein the tire width direction central region Lc is set in a range of 0.5 ≦ Lc / L0 ≦ 1.1. The pneumatic tire according to claim 1 or 2 , wherein the land portion defined by the main groove in the tread portion is a rib-like land portion extending in a tire circumferential direction.

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