JP2012153193A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can improve a belt durability of a first belt.SOLUTION: In a pneumatic tire 1, which has an aspect ratio of 65 [%] or below, keeps a belt layer 7, including at least three layers of steel code belts laminated in orders of: a first belt 71, a second belt 72, and a third belt 73 on an outer side in a tire diameter direction of a carcass layer 6 of a tread part 2 from the carcass layer 6, arranged on the outer side in a tire diameter direction, and has a code angle of 50[°] or above and 80[°] or below with respect to a tire circumferential direction of the innermost first belt 71 in the tire diameter direction, a code diameter of the first belt 71 is larger than the maximum code diameters of the second belt 72 and the third belt 73, and a product of a code cross-sectional area and a number of code rammings per a width of 50[mm] has a relation of 0.5≤(first belt)/(second belt+third belt)≤0.65.

Description

  The present invention relates to a pneumatic tire that improves belt durability of a first belt.

  In a pneumatic tire in which a belt layer having a plurality of belts is provided on the outer side in the tire radial direction of the carcass layer, particularly in a heavy tire with a low flatness (for example, a flatness ratio of 65 [%] or less) Buckling of the tread portion (the center portion of the tread portion is pushed inward in the tire radial direction by the load at the time of ground contact) occurs. Buckling occurs in the tire circumferential direction and the tire width direction, and the buckling in the tire width direction causes compression in the steel cord of the first belt closest to the carcass layer. And when a big compression force is applied, there exists a possibility that the strand of the strand of the said code | cord | chord may fall, and the resistance force with respect to compression of the code | cord | chord of a 1st belt will fall. As a result, the belt durability of the first belt is lowered. If the belt durability of the first belt is reduced, the cord of the first belt may be bent or cut when an unspecified compression force is applied.

Conventionally, in order to improve the durability of the belt, for example, a pneumatic tire described in Patent Document 1 (a heavy-duty pneumatic radial tire) is disclosed. The pneumatic tire has a first belt and the maximum width W ₁₂ of the second belt of the belt layer, the maximum width W ₃₄ of the third belt and fourth belt, the maximum width W ₅₆ of the fifth belt and sixth belts And W ₅₆ > W ₃₄ > W ₁₂ , and the relationship between the cord diameter D _{12 of} the first belt and the second belt and the cord diameter D _{34 of} the third belt and the fourth belt is 1> D ₁₂ / D ₃₄ > 0.6, and the steel cord of each belt has a double twisted structure in which 2 to 10 twisted cables are twisted together.

Conventionally, in order to improve high-speed durability, for example, a pneumatic tire (radial tire) described in Patent Document 2 is disclosed. This pneumatic tire comprises a cross belt having two belt layers, and at least one circumferential belt on the outer side in the tire radial direction of the cross belt, a cross-sectional area of a steel cord of the circumferential belt, and a circumferential belt. The product with the number of cords driven per 50 [mm] width is 3.0 [mm ² ] or more.

JP 2008-6969 A JP 2006-69338 A

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can improve the belt durability of a 1st belt.

  In order to solve the above-described problems and achieve the object, the pneumatic tire of the present invention has an aspect ratio of 65 [%] or less, and from the carcass layer to the tire radial direction outside the tire radial direction of the carcass layer of the tread portion. A belt layer having at least three steel cord belts laminated in the order of the first belt, the second belt, and the third belt is disposed on the outer side, and the tire circumferential direction of the first belt on the innermost side in the tire radial direction In the pneumatic tire in which the cord angle with respect to is 50 [°] or more and 80 [°] or less, the cord diameter of the first belt is not less than the cord diameter of the maximum diameter of the second belt and the third belt, In addition, the product of the cord cross-sectional area and the number of cords driven per width of 50 [mm] has a relationship of 0.5 ≦ (first belt) / (second belt + third belt) ≦ 0.65. Special It is a sign.

  Conventionally, when a large compressive force is applied due to buckling of the tread portion at the time of ground contact, particularly buckling in the tire width direction, the strand of the first belt cord closest to the carcass layer is scattered, and the first belt The resistance to compression of the cord may be reduced. In this regard, according to the pneumatic tire of the present invention, the decrease in resistance to compression is suppressed by improving the rigidity of the cord of the first belt. As a result, the belt durability (cord folding resistance) of the first belt can be improved.

  The pneumatic tire of the present invention has a thickness not less than 55% and not more than 90% of the cord diameter of the first belt on the inner side in the tire radial direction of the first belt, A rubber material having a width of 50 [%] or more in the tire width direction dimension and a modulus at 50 [%] elongation of 1.0 [MPa] or more and 1.8 [MPa] or less is arranged. To do.

  As described above, when the rigidity of the cord of the first belt is improved, the belt rigidity tends to increase, and when the tread portion buckles at the time of ground contact, the escape of the cord of the first belt becomes small. If force is applied, belt failure (separation) may occur. In this regard, according to the pneumatic tire of the present invention, by arranging the rubber material, it is possible to ensure the escape of the cord of the first belt when the tread portion is buckled at the time of ground contact. As a result, the belt durability (separation resistance) of the first belt can be improved.

  The pneumatic tire of the present invention has a thickness of 55% to 90% of the cord diameter of the first belt on the outer side in the tire radial direction of the first belt, A rubber material having a width of 50 [%] or more in the tire width direction dimension and a modulus at 50 [%] elongation of 1.0 [MPa] or more and 1.8 [MPa] or less is arranged. To do.

  As described above, when the rigidity of the cord of the first belt is improved, the belt rigidity tends to increase, and when the tread portion buckles at the time of ground contact, the escape of the cord of the first belt becomes small. If force is applied, belt failure (separation) may occur. In this regard, according to the pneumatic tire of the present invention, by arranging the rubber material, it is possible to ensure the escape of the cord of the first belt when the tread portion is buckled at the time of ground contact. As a result, the belt durability (separation resistance) of the first belt can be improved.

  The pneumatic tire of the present invention has a total thickness of 55% to 90% of the cord diameter of the first belt on the inner side and the outer side in the tire radial direction of the first belt. A rubber material having a width of 50 [%] or more of the dimension of the first belt in the tire width direction and a modulus at 50 [%] elongation of 1.0 [MPa] or more and 1.8 [MPa] or less. It is arranged.

  As described above, when the rigidity of the cord of the first belt is improved, the belt rigidity tends to increase, and when the tread portion buckles at the time of ground contact, the escape of the cord of the first belt becomes small. If force is applied, belt failure (separation) may occur. In this regard, according to the pneumatic tire of the present invention, by arranging the rubber material, it is possible to ensure the escape of the cord of the first belt when the tread portion is buckled at the time of ground contact. As a result, the belt durability (separation resistance) of the first belt can be improved.

  In the pneumatic tire according to the present invention, the total thickness of the rubber excluding the cord diameter of the first belt from the tire radial dimension between the cords on both sides in the tire radial direction of the first belt has a cord of the first belt. It is characterized by being 124 [%] or more and 157 [%] or less of the diameter.

  As described above, when the rigidity of the cord of the first belt is improved, the belt rigidity tends to increase, and when the tread portion buckles at the time of ground contact, the escape of the cord of the first belt becomes small. If force is applied, belt failure (separation) may occur. In this regard, according to the pneumatic tire of the present invention, by arranging the rubber material, it is possible to ensure the escape of the cord of the first belt when the tread portion is buckled at the time of ground contact. As a result, the belt durability (separation resistance) of the first belt can be improved. When this configuration is defined by the total thickness of the rubber, the total effect of the rubber is not less than 124 [%] and not more than 157 [%] of the cord diameter of the first belt. It is suitable in the above.

  The pneumatic tire according to the present invention can improve the belt durability of the first belt.

FIG. 1 is a partially cut meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of the belt layer of the pneumatic tire according to the embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view of the belt layer of the pneumatic tire according to the embodiment of the present invention. FIG. 4 is an enlarged cross-sectional view of the belt layer of the pneumatic tire according to the embodiment of the present invention. FIG. 5 is an enlarged cross-sectional view of the belt layer of the pneumatic tire according to the embodiment of the present invention. FIG. 6 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 7 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 8 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 9 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. FIG. 10 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  FIG. 1 is a partially cut meridian cross-sectional view of a pneumatic tire according to the present embodiment. In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire radial direction outer side. 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 C (tire equator line) 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 C. The tire equator plane C is a plane that is orthogonal to the rotation axis 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 1. In the present embodiment, the same sign “C” as that of the tire equator plane is attached to the tire equator line.

  As shown in FIG. 1, the pneumatic tire 1 includes a tread portion 2, shoulder portions 3 on both sides of the tread portion 2, sidewall portions 4 and bead portions (not shown) sequentially continuing from the shoulder portions 3. It is configured. Further, the pneumatic tire 1 has a carcass layer 6 and a belt layer 7.

  The tread portion 2 is exposed to the outside of the pneumatic tire 1, and the surface thereof is the contour of the pneumatic tire 1. 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 formed with a plurality of circumferential main grooves 22 extending in the tire circumferential direction and a plurality of ribs 23 forming a plurality of land portions defined by the circumferential main grooves 22.

  The shoulder portion 3 is a portion on both outer sides in the tire width direction of the tread portion 2. The sidewall portions 4 are exposed on both outer sides in the tire width direction of the pneumatic tire 1. Although not clearly shown in the figure, the bead portion is formed by winding a bead core, which is a steel cord, in a ring shape, and the carcass layer 6 being folded outward in the tire width direction at the position of the bead core. And a bead filler disposed in the designated space.

  In the tire width direction, the carcass layer 6 continuously straddles the tread portion 2, both sidewall portions 4, and both bead portions, and both side ends in the tire width direction are wound back around the pair of bead portions. The skeleton of the tire is configured by being toroidally wound in the circumferential direction. Further, the carcass layer 6 is formed by covering a cord 6a (see FIG. 2) made of steel with a rubber material. A plurality of cords 6a are arranged in parallel in the tire circumferential direction while being orthogonal to the tire equator line C of the pneumatic tire 1 and along the tire meridian direction (radial direction). The angle of the cord 6a in the carcass layer 6 with respect to the tire equator line C (tire circumferential direction) is substantially 90 [°], and is −5 [°] with respect to 90 [°] with respect to the tire equator line C. Including an angle in the range of +5 [°]. The carcass layer 6 serves as a pressure vessel when the pneumatic tire 1 is filled with air, and supports a load applied to the pneumatic tire 1 by the internal pressure.

  The belt layer 7 is provided on the outer side in the tire radial direction than the carcass layer 6 in the tread portion 2. The belt layer 7 is a cord formed of steel and covered with rubber, and covers the carcass layer 6 along the tire circumferential direction. The belt layer 7 in the present embodiment is laminated in the order of the first belt 71, the second belt 72, the third belt 73, and the fourth belt 74 from the inner side in the tire radial direction of the carcass layer 6 toward the outer side in the tire radial direction. 4 layers of steel cord belt.

  The first belt 71 is disposed such that a cord 71a (see FIG. 2) covered with rubber has an angle of 50 [°] to 80 [°] with respect to the tire circumferential direction, that is, the tire equator line C. This is a so-called high-angle belt. The first belt 71 is formed to have a smaller size in the tire width direction than a belt (second belt 72 in the present embodiment) having a large size in the tire width direction in the crossing belt.

  In the second belt 72 and the third belt 73, the cords 72a and 73a (see FIG. 2) covered with rubber are 10 [°] or more and 30 [°] or less with respect to the tire circumferential direction, that is, the tire equator line C. Are arranged at an angle of. Further, the second belt 72 and the third belt 73 form a cross belt in which cords that form an angle with respect to the tire circumferential direction are arranged so as to cross each other between the stacked belts.

  The fourth belt 74 is a so-called protective belt in which a cord covered with rubber is disposed with an angle of 10 [°] or more and 30 [°] or less with respect to the tire circumferential direction, that is, the tire equator line C. I am doing. The fourth belt 74 is formed to have a smaller dimension in the tire width direction than the second belt 72 and the third belt 73 that are crossing belts.

  Moreover, it is preferable that the pneumatic tire 1 of this Embodiment is applied as a heavy duty pneumatic tire with a flatness ratio of 65% or less. Here, the flatness ratio represents the tire height with respect to the total width in the tire width direction as a ratio. The total width in the tire width direction is the widest portion in the tire width direction in the pneumatic tire 1, and the distance between the outermost portions in the tire width direction among the sidewall portions 4 at both ends, that is, a pair of sidewall portions 4 is the distance between the parts farthest from the tire equatorial plane C. The tire height is the tire cross-sectional height along the tire radial direction from the inner end (rim base position) in the tire radial direction of the bead portion to the tread surface 21 (crown center) on the outermost side in the tire radial direction.

  In the pneumatic tire 1 of the present embodiment, the cord diameter D1 of the cord 71a of the first belt 71 is equal to the cord 72a of the second belt 72 and the third belt 73, as shown in the enlarged sectional view of the belt layer in FIG. 73a is equal to or greater than the maximum cord diameter D2. Note that the cords 72a and 73a of the second belt 72 and the third belt 73 are generally the same cord diameter, and in FIG. 2, the cord diameter D2 of the cord 72a of the second belt 72 is shown. . The cord diameter means the entire outer diameter of the twisted strands when the strands are twisted together.

  Furthermore, the product P1 of the cord cross-sectional area of one cord 71a of the first belt 71 and the number of cords driven (number of ends) per 50 [mm] width is the cord of one cord 72a of the second belt 72. The product P2 of the cross-sectional area and the number of cords driven (number of ends) per 50 [mm] in width, the cord cross-sectional area of one cord 73a of the third belt 73, and the number of cords driven per 50 [mm] in width The relationship of 0.5 ≦ P1 / (P2 + P3) ≦ 0.65 is established with respect to the product P3 with (the number of ends). In addition, a cord cross-sectional area means what added the cross-sectional area of each strand twisted together, when a strand is twisted together.

  Conventionally, when a large compressive force is applied conventionally due to buckling of the tread portion 2 (the center portion of the tread portion 2 is pushed inward in the tire radial direction by a load at the time of ground contact), in particular, buckling in the tire width direction, There is a possibility that the strands of the cord 71a of the first belt 71 closest to the carcass layer 6 may be unwound and resistance to compression of the cord 71a of the first belt 71 may be reduced. In this regard, according to the pneumatic tire 1 of the present embodiment, the cord diameter D1 of the cord 71a of the first belt 71 is the maximum cord diameter D2 of the cords 72a and 73a of the second belt 73 and the third belt 73. And the relationship of the product of the cord cross-sectional area and the number of cords driven (number of ends) per 50 [mm] width is 0.5 ≦ P1 / (P2 + P3) ≦ 0.65 By improving the rigidity of the cord 71a of the first belt 71, a decrease in resistance to compression is suppressed. As a result, the belt durability (cord folding resistance) of the first belt 71 can be improved.

  If P1 / (P2 + P3) is less than 0.5, the mass of the cord 71a of the first belt 71 is small, so that the belt durability is not improved and the effect is small. On the other hand, if P1 / (P2 + P3) exceeds 0.65, the mass of the cord 71a of the first belt 71 is too large, and the belt durability decreases. Therefore, 0.5 ≦ P1 / (P2 + P3) ≦ 0.65 is suitable for improving the belt durability of the first belt 71.

  Further, the pneumatic tire 1 of the present embodiment has a rubber material 8 between the first belt 71 and the carcass layer 6 as shown in the enlarged sectional view of the belt layer in FIG. Is arranged. The rubber material 8 is formed with a thickness T in the tire radial direction that is 55% or more and 90% or less of the cord diameter D1 of the cord 71a of the first belt 71. Further, as shown in FIG. 1, the rubber material 8 has a width of 50% or more of the tire width direction dimension W of the first belt 71, and is preferably disposed near the center in the tire width direction. . That is, as shown in FIG. 1, the rubber material 8 has a tire width direction dimension W of the first belt 71 of 1/4 and a W / 2 range in the tire width direction on the tire equatorial plane C as a boundary. It is preferable that at least be arranged. Further, the rubber material 8 has a modulus at 50 [%] elongation at normal temperature according to JIS K 6251 of 1.0 [MPa] or more and 1.8 [MPa] or less.

  As described above, if the rigidity of the cord 71a of the first belt 71 is improved, the belt rigidity tends to increase, and the escape of the cord 71a of the first belt 71 is reduced when the tread portion 2 is buckled at the time of ground contact. If an unspecified compression force is applied, belt failure (separation) may occur. In this regard, according to the pneumatic tire 1 of the present embodiment, the rubber material 8 is disposed, so that the escape of the cord 71a of the first belt 71 is ensured when the tread portion 2 is buckled at the time of ground contact. As a result, the belt durability (separation resistance) of the first belt 71 can be improved.

  If the thickness T of the rubber material 8 is less than 55% of the cord diameter D1 of the cord 71a of the first belt 71, the escape of the cord 71a of the first belt 71 is small when the tread portion 2 is buckled. The contribution of the one belt 71 to the separation resistance is reduced. On the other hand, if it exceeds 90 [%], the heat generation is increased and the heat resistance is lowered, so that the contribution of the first belt 71 to the separation resistance is lowered. Therefore, the separation T of the first belt 71 is improved by forming the thickness T of the rubber material 8 to 55 [%] or more and 90 [%] or less of the cord diameter D1 of the cord 71a of the first belt 71. Suitable for Further, when the width of the rubber material 8 is less than 50% of the tire width direction dimension W of the first belt 71, the escape of the cord 71a of the first belt 71 is small when the tread portion 2 is buckled. The contribution of the one belt 71 to the separation resistance is reduced. Therefore, setting the width of the rubber material 8 to 50 [%] or more of the tire width direction dimension W of the first belt 71 is suitable for improving the separation resistance of the first belt 71. Further, if the modulus of the rubber material 8 is less than 1.0 [MPa], the elastic modulus is too low, and the contribution of the first belt 71 to the cord breakage resistance is reduced. On the other hand, if it exceeds 1.8 [MPa], the elastic modulus is too high, and the contribution of the first belt 71 to the separation resistance is reduced. Therefore, the modulus of the rubber material 8 at 50 [%] elongation at normal temperature in accordance with JIS K 6251 is 1.0 [MPa] or more and 1.8 [MPa] or less so that the resistance of the first belt 71 is increased. Suitable for improving cord breakage and separation resistance.

  Further, the pneumatic tire 1 of the present embodiment is a rubber material between the second belt 72 and the outer side in the tire radial direction of the first belt 71, as shown in the enlarged sectional view of the belt layer in FIG. 9 is arranged. The rubber material 9 is formed with a thickness T in the tire radial direction that is 55% or more and 90% or less of the cord diameter D1 of the cord 71a of the first belt 71. Further, as shown in FIG. 1, the rubber material 9 has a width of 50% or more of the tire width direction dimension W of the first belt 71, and is preferably disposed near the center in the tire width direction. . That is, as shown in FIG. 1, the rubber material 9 has a tire width direction dimension W of the first belt 71 of 1/4 and a W / 2 range in the tire width direction on the tire equatorial plane C as a boundary. It is preferable that at least be arranged. In addition, the rubber material 9 has a modulus at 50 [%] elongation at normal temperature in accordance with JIS K 6251 of 1.0 [MPa] to 1.8 [MPa].

  According to the pneumatic tire 1, the rubber material 9 is disposed, so that the escape of the cord 71 a of the first belt 71 can be ensured when the tread portion 2 is buckled at the time of ground contact. Belt durability (separation resistance) can be improved.

  If the thickness T of the rubber material 9 is less than 55% of the cord diameter D1 of the cord 71a of the first belt 71, the escape of the cord 71a of the first belt 71 is small when the tread portion 2 is buckled. The contribution of the one belt 71 to the separation resistance is reduced. On the other hand, if it exceeds 90 [%], the heat generation is increased and the heat resistance is lowered, so that the contribution of the first belt 71 to the separation resistance is lowered. Therefore, forming the thickness T of the rubber material 9 to 55 [%] or more and 90 [%] or less of the cord diameter D1 of the cord 71a of the first belt 71 improves the separation resistance of the first belt 71. Suitable for Further, when the width of the rubber material 9 is less than 50 [%] of the tire width direction dimension W of the first belt 71, the escape of the cord 71a of the first belt 71 is small when the tread portion 2 is buckled. The contribution of the one belt 71 to the separation resistance is reduced. Therefore, it is suitable for improving the separation resistance of the first belt 71 that the width of the rubber material 9 is 50% or more of the tire width direction dimension W of the first belt 71. Further, if the modulus of the rubber material 9 is less than 1.0 [MPa], the elastic modulus is too low, and the contribution of the first belt 71 to the cord breakage resistance is reduced. On the other hand, if it exceeds 1.8 [MPa], the elastic modulus is too high, and the contribution of the first belt 71 to the separation resistance is reduced. Therefore, the modulus of elasticity of the first belt 71 of the rubber material 9 is set to 1.0 [MPa] or more and 1.8 [MPa] or less when the modulus at 50 [%] elongation at normal temperature according to JIS K 6251 is set. Suitable for improving cord breakage and separation resistance.

  In addition, as shown in the enlarged sectional view of the belt layer in FIG. 5, the pneumatic tire 1 of the present embodiment is on the inner side in the tire radial direction of the first belt 71 and between the carcass layer 6 and in the tire radial direction. Each rubber material 10 is arranged between the outer side and the second belt 72. The rubber material 10 is formed with a total thickness T in the tire radial direction that is 55% or more and 90% or less of the cord diameter D1 of the cord 71a of the first belt 71. The total thickness T is obtained by adding the thickness Ta of each rubber material 10. Further, as shown in FIG. 1, the rubber material 10 has a width of 50% or more of the tire width direction dimension W of the first belt 71 and is preferably disposed near the center in the tire width direction. . That is, as shown in FIG. 1, the rubber material 10 has a width W in the tire width direction on the inner side of the tire equatorial plane C with the tire width direction dimension W of the first belt 71 being 1/4. It is preferable that at least be arranged. Further, the rubber material 10 has a modulus at 50 [%] elongation at normal temperature according to JIS K 6251 of 1.0 [MPa] or more and 1.8 [MPa] or less.

  According to this pneumatic tire 1, since the rubber material 10 is arranged, it is possible to ensure the escape of the cord 71 a of the first belt 71 when the tread portion 2 is buckled at the time of ground contact. Belt durability (separation resistance) can be improved.

  If the total thickness T of the rubber material 10 is less than 55% of the cord diameter D1 of the cord 71a of the first belt 71, the escape of the cord 71a of the first belt 71 is small when the tread portion 2 is buckled. The contribution of the first belt 71 to the separation resistance is reduced. On the other hand, if it exceeds 90 [%], the heat generation is increased and the heat resistance is lowered, so that the contribution of the first belt 71 to the separation resistance is lowered. Therefore, forming the total thickness T of the rubber material 10 to be 55 [%] or more and 90 [%] or less of the cord diameter D1 of the cord 71a of the first belt 71 improves the separation resistance of the first belt 71. Suitable for that. Further, when the width of the rubber material 10 is less than 50% of the tire width direction dimension W of the first belt 71, the escape of the cord 71a of the first belt 71 is small when the tread portion 2 is buckled. The contribution of the one belt 71 to the separation resistance is reduced. Therefore, it is suitable to improve the separation resistance of the first belt 71 by setting the width of the rubber material 10 to 50 [%] or more of the tire width direction dimension W of the first belt 71. Further, if the modulus of the rubber material 10 is less than 1.0 [MPa], the elastic modulus is too low, and the contribution of the first belt 71 to the cord breakage resistance is reduced. On the other hand, if it exceeds 1.8 [MPa], the elastic modulus is too high, and the contribution of the first belt 71 to the separation resistance is reduced. Therefore, the modulus of 50 [%] elongation at normal temperature according to JIS K 6251 of the rubber material 10 is 1.0 [MPa] or more and 1.8 [MPa] or less, so Suitable for improving cord breakage and separation resistance.

  Further, the pneumatic tire 1 of the present embodiment has a tire radial dimension between cords 72a and 6a on both sides in the tire radial direction of the first belt 71, as shown in the enlarged sectional views of the belt layer in FIGS. The total rubber thickness excluding the cord diameter D1 of the cord 71a in the first belt 71 from Tmix (Tmix-D1), that is, the cord 72a of the second belt 72 on both sides in the tire radial direction of the first belt 71 and the cord of the carcass layer 6 6a, the tire radial direction dimension of the rubber material 8, the rubber material 9 or the rubber material 10 excluding the cord diameter D1 of the cord 71a of the first belt 71, and the second belt 72 The total rubber thickness (Tmix-D1) including the rubber on the first belt 71 side and the tire radial direction dimension of the rubber on the first belt 71 side in the carcass layer 6 is the first. It is preferable 124 of the cord diameter D1 of the cord 71a of the belt 71% or more and 157% or less.

  According to this pneumatic tire 1, the first belt 71 is provided when the tread portion 2 is buckled at the time of grounding by arranging the rubber material 8, the rubber material 9 or the rubber material 10 as shown in FIGS. 3 to 5. The escape of the cord 71a can be ensured. As a result, the belt durability (separation resistance) of the first belt 71 can be improved. When this configuration is defined by the total thickness (Tmix-D1) of the rubber, the total thickness (Tmix-D1) of the rubber is equal to or greater than 124 [%] of the cord diameter D1 of the cord 71a of the first belt 71 157 [ %] Or less is preferable for remarkably obtaining the above effect.

  In this example, performance tests regarding belt durability (cord breakage resistance, separation resistance) were performed on a plurality of types of pneumatic tires having different conditions (see FIGS. 6 to 10).

  In this performance test, a pneumatic tire having a tire size of 385 / 65R22.5 160J was assembled to a regular rim and filled with a regular internal pressure as a test tire. The regular rim here refers to “standard rim” defined in JATMA, “Design Rim” defined in TRA, or “Measuring Rim” defined in ETRTO. The normal internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load described later means “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. .

  In the belt durability performance test, the above test tire with a normal load applied was tested with a drum-type durability performance tester at a running speed of 45 [km / h] and a slip angle of ± 2 [degrees] of 10 [seconds]. ], And after running for 2 hours at normal load, increase 115% of normal load and then increase load by 5% of normal load every 24 [hour], causing the tire to break Is done. In the performance test of the cord breakage resistance, the cord breakage or breakage of the first belt is confirmed after breaking. In the separation resistance performance test, the distance traveled until the vehicle breaks is measured and the details of the separation failure are confirmed. In such a separation resistance performance test, the travel distance is preferably 3400 [km] or more, and the separation resistance is excellent.

  Here, in FIGS. 6 to 10, the first belt cord cross-sectional area and the second and third belt cord cross-sectional areas are indicated by indices based on the first belt cord cross-sectional area of Comparative Example 1 as a reference (100). Yes.

  The performance test shown in FIG. 6 is a performance test related to resistance to cord breakage. In this performance test, in the pneumatic tires of Comparative Examples 1 to 3, the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the first belt The ratio (P1 / (P2 + P3)) of the product P1 of the cord cross-sectional area and the number of ends to the products P2 and P3 of the cord cross-sectional areas of the second belt and the third belt and the number of ends is out of the specified range. . On the other hand, in the pneumatic tires of Examples 1 to 4, the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the cord breakage of the first belt A ratio (P1 / (P2 + P3)) of the product P1 of the area and the number of ends to the products P2 and P3 of the cord cross-sectional areas of the second belt and the third belt and the number of ends is set to a specified range. In the schematic diagram of the belt structure shown in FIG. 6, the first to third belts are indicated by solid lines.

  The performance test shown in FIG. 7 is a performance test related to cord breakage resistance and separation resistance (failure content: second and third belt edge separation), which is on the inner side in the tire radial direction of the first belt and with the carcass layer. A rubber material is disposed between them. In this performance test, in the pneumatic tire of Comparative Example 4, the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the cord cross-sectional area of the first belt The ratio (P1 / (P2 + P3)) of the product P1 of the number of ends and the number of ends to the products P2 and P3 of the cord cross-sectional areas of the second belt and the third belt and the numbers of ends is within a specified range. The thickness, width, and modulus of this are outside the specified ranges. Further, in the pneumatic tire of Comparative Example 5, the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, the cord cross-sectional area and the number of ends of the first belt The ratio (P1 / (P2 + P3)) of the product P1 to the products P2 and P3 of the cord cross-sectional areas of the second belt and the third belt and the number of ends is within a specified range. The modulus is outside the specified range. Further, in the pneumatic tire of Comparative Example 6, the thickness, the width, and the modulus of the rubber material are within the specified ranges, but the second belt having the product P1 of the cord cross-sectional area and the number of ends of the first belt and The ratio (P1 / (P2 + P3)) of the cord cross-sectional area and the number of ends of the third belt to the products P2 and P3 is out of the specified range. On the other hand, in the pneumatic tires of Examples 5 to 9, the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the cord breakage of the first belt The ratio (P1 / (P2 + P3)) of the product P1 of the area and the number of ends to the products P2 and P3 of the cord cross-sectional area and the number of ends of the second belt and the third belt is within a specified range, and the rubber material Thickness, width, and modulus are within the prescribed ranges. In the schematic diagram of the belt structure shown in FIG. 7, the first to third belts are indicated by solid lines, and the rubber material is indicated by broken lines.

  The performance test shown in FIG. 8 is a performance test related to cord breakage resistance and separation resistance (failure content: second and third belt edge separation), and is the outer side in the tire radial direction of the first belt and the second belt. A rubber material is arranged between them. In this performance test, in the pneumatic tire of Comparative Example 7, the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the cord cross-sectional area of the first belt The ratio (P1 / (P2 + P3)) of the product P1 of the number of ends and the number of ends to the products P2 and P3 of the cord cross-sectional areas of the second belt and the third belt and the numbers of ends is within a specified range. The thickness, width, and modulus of this are outside the specified ranges. Further, in the pneumatic tire of Comparative Example 8, the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the cord cross-sectional area and the number of ends of the first belt The ratio (P1 / (P2 + P3)) of the product P1 to the products P2 and P3 of the cord cross-sectional areas of the second belt and the third belt and the number of ends is within a specified range. The modulus is outside the specified range. In the pneumatic tire of Comparative Example 9, the thickness, width, and modulus of the rubber material are within the specified ranges, but the second belt having the product P1 of the cord cross-sectional area and the number of ends of the first belt and The ratio (P1 / (P2 + P3)) of the cord cross-sectional area and the number of ends of the third belt to the products P2 and P3 is out of the specified range. On the other hand, in the pneumatic tires of Examples 10 to 14, the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the cord breakage of the first belt The ratio (P1 / (P2 + P3)) of the product P1 of the area and the number of ends to the products P2 and P3 of the cord cross-sectional area and the number of ends of the second belt and the third belt is within a specified range, and the rubber material Thickness, width, and modulus are within the prescribed ranges. In the belt structure schematic diagram shown in FIG. 8, the first belt to the third belt are indicated by solid lines, and the rubber material is indicated by broken lines.

  The performance test shown in FIG. 9 is a performance test related to cord breakage resistance and separation resistance (failure content: second and third belt edge separation), and is the inner side in the tire radial direction of the first belt and the carcass layer. A rubber material is disposed between and between the second belt and the outer side in the tire radial direction of the first belt. In this performance test, the pneumatic tire of Comparative Example 10 has the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the cord cross-sectional area of the first belt. The ratio (P1 / (P2 + P3)) of the product P1 of the number of ends and the number of ends to the products P2 and P3 of the cord cross-sectional areas of the second belt and the third belt and the numbers of ends is within a specified range. The thickness, width, and modulus of this are outside the specified ranges. Further, in the pneumatic tire of Comparative Example 11, the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the cord cross-sectional area and the number of ends of the first belt The ratio (P1 / (P2 + P3)) of the product P1 to the products P2 and P3 of the cord cross-sectional areas of the second belt and the third belt and the number of ends is within a specified range. The modulus is outside the specified range. Further, in the pneumatic tire of Comparative Example 12, the thickness, width, and modulus of the rubber material are within the specified ranges, but the second belt having the product P1 of the cord cross-sectional area and the number of ends of the first belt and The ratio (P1 / (P2 + P3)) of the cord cross-sectional area and the number of ends of the third belt to the products P2 and P3 is out of the specified range. On the other hand, in the pneumatic tires of Examples 15 to 19, the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the cord breakage of the first belt The ratio (P1 / (P2 + P3)) of the product P1 of the area and the number of ends to the products P2 and P3 of the cord cross-sectional area and the number of ends of the second belt and the third belt is within a specified range, and the rubber material Thickness, width, and modulus are within the prescribed ranges. In the belt structure schematic diagram shown in FIG. 9, the first to third belts are indicated by solid lines, and the rubber material is indicated by broken lines.

  The performance test shown in FIG. 10 is a performance test related to cord breakage resistance and separation resistance (failure content: second and third belt edge separation), and in the tire radial direction inner side of the first belt as in FIG. A rubber material is disposed between the carcass layer. In this performance test, the pneumatic tire of Comparative Example 13 has the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the cord cross-sectional area of the first belt. The ratio (P1 / (P2 + P3)) of the product P1 of the number of ends and the number of ends to the products P2 and P3 of the cord cross-sectional areas of the second belt and the third belt and the numbers of ends is within a specified range. The total rubber thickness ((Tmix-D1) / D1), width, and modulus with respect to the belt cord diameter are out of the specified ranges. Further, in the pneumatic tire of Comparative Example 14, the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the cord cross-sectional area and the number of ends of the first belt The ratio (P1 / (P2 + P3)) of the product P1 of the second belt and the third belt to the products P2 and P3 (P1 / (P2 + P3)) is within a specified range, but the total rubber thickness (( Tmix-D1) / D1) and modulus are out of specified range. In the pneumatic tire of Comparative Example 15, the total rubber thickness ((Tmix-D1) / D1), the width, and the modulus with respect to the cord diameter of the first belt are within the specified ranges. The ratio (P1 / (P2 + P3)) of the product P1 of the cross-sectional area and the number of ends to the products P2 and P3 of the cord cross-sectional areas of the second belt and the third belt and the number of ends is out of the specified range. On the other hand, in the pneumatic tires of Examples 20 to 24, the cord diameter ratio (D1 / D2 or D3) of the cord of the first belt to the cord of the second belt and the third belt, and the cord breakage of the first belt. The ratio (P1 / (P2 + P3)) of the product P1 of the area and the number of ends to the products P2 and P3 of the cord cross-sectional areas and the numbers of ends of the second belt and the third belt is within a specified range, and the first belt The total rubber thickness ((Tmix-D1) / D1), the width, and the modulus with respect to the cord diameter are within the specified ranges.

  As shown in the test results of FIG. 6, it can be seen that the pneumatic tires of Examples 1 to 4 have improved belt durability (cord folding resistance). Moreover, as shown in the test results of FIGS. 7 to 10, it can be seen that the pneumatic tires of Examples 5 to 24 have improved belt durability (cord breakage resistance and separation resistance).

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 21 Tread surface 22 Circumferential main groove 23 Rib 3 Shoulder part 4 Side wall part 6 Carcass layer 6a cord 7 Belt layer 71 1st belt 71a cord 72 2nd belt 72a cord 73 3rd belt 73a cord 74 Fourth belt 8, 9, 10 Rubber material C Tire equator surface (tire equator line)

Claims (5)

The flatness is 65% or less, and at least three layers are laminated in the order of the first belt, the second belt, and the third belt on the outer side in the tire radial direction of the carcass layer in the tread portion and on the outer side in the tire radial direction from the carcass layer. In the pneumatic tire in which the belt layer having the steel cord belt is arranged, and the cord angle with respect to the tire circumferential direction of the first belt on the innermost side in the tire radial direction is 50 [°] or more and 80 [°] or less,
The cord diameter of the first belt is equal to or greater than the cord diameter of the maximum diameter of the second belt and the third belt, and the product of the cord cross-sectional area and the number of cords driven per 50 [mm] width is 0. 5. A pneumatic tire characterized by a relation of 5 ≦ (first belt) / (second belt + third belt) ≦ 0.65.   On the inner side in the tire radial direction of the first belt, the cord has a thickness of 55% to 90% of the cord diameter of the first belt, and is 50% or more of the tire width direction dimension of the first belt. 2. A pneumatic tire according to claim 1, wherein a rubber material having a width of 50 [%] and a modulus at expansion of 50 [%] of 1.0 [MPa] to 1.8 [MPa] is disposed. .   On the outer side in the tire radial direction of the first belt, the thickness is 55 [%] or more and 90 [%] or less of the cord diameter of the first belt, and is 50 [%] or more of the tire width direction dimension of the first belt. 2. A pneumatic tire according to claim 1, wherein a rubber material having a width of 50 [%] and a modulus at expansion of 50 [%] of 1.0 [MPa] to 1.8 [MPa] is disposed. .   A total thickness of 55% or more and 90% or less of a cord diameter of the first belt on a tire radial direction inner side and a tire radial direction outer side of the first belt, and a tire width direction dimension of the first belt. A rubber material having a width of 50 [%] or more and having a modulus at 50 [%] elongation of 1.0 [MPa] or more and 1.8 [MPa] or less is disposed. Pneumatic tire described in 2.   The total thickness of the rubber excluding the cord diameter of the first belt from the tire radial dimension between the cords on both sides in the tire radial direction of the first belt is 124 [%] or more and 157 [%] of the cord diameter of the first belt. The pneumatic tire according to any one of claims 2 to 4, wherein:

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