JP2012025296A - Pneumatic tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a bead part.SOLUTION: This pneumatic tire includes shock-absorbing rubber 16 which is mounted on a normal rim and is arranged from an intersection P in which a reference line S passing a tire width direction outermost end 11a of a bead core 11 and extending in a tire width direction crosses an inner peripheral surface of a steel reinforcing layer 14 toward the tire radial direction outside between a carcass layer 12 and the steel reinforcing layer 14 by making the intersection P as a base point on a bead heel side in a non-load state filled with normal internal pressure. A relation between a tire radial direction dimension H from the reference line S to a tire radial direction outside end of the shock-absorbing rubber 16, a tire radial direction dimension HS from the reference line S to a tire width direction outside end of the steel reinforcing layer 14 and a tire radial direction dimension HC from the reference line S to a tire width direction outside end of the carcass layer 12 is made HS<H≤HC. The carcass layer 12 is formed into a projection shape at the tire width direction inside in a part where the shock-absorbing rubber 16 is arranged.

Description

  The present invention relates to a heavy-duty pneumatic tire with improved bead durability.

  The bead portion of the heavy duty pneumatic tire receives a reaction force from the rim flange at the portion in contact with the rim flange and undergoes a shear stress at the portion in contact with the rim flange when the tire is rolling while being loaded. Concentrate. For this reason, when a high load is applied, a crack may occur between the steel reinforcing layer and the rim cushion rubber disposed outside the steel reinforcing layer in the bead portion.

  Conventionally, in a heavy-duty pneumatic tire (heavy-duty radial tire) described in Patent Document 1, a steel reinforcing layer (wire chafer) is provided outside the carcass layer, and a rubber material is provided between the carcass layer and the steel reinforcing layer. The technique of placement is shown. Specifically, the carcass on the bead wire side from the intersecting line where the vertical surface passing through the center of curvature of the curved surface of the rim flange contact portion of the bead portion rotates 35 ° ± 5 ° to the bead wire side and the steel reinforcing layer intersects. The rubber thickness T1 between the metal cord of the layer and the wire of the steel reinforcing layer is set to 0.2 [mm] ≦ T1 ≦ 1.6 [mm], and on the outer side in the tire radial direction of the intersection line, the carcass layer The rubber thickness T2 between the metal cord and the wire of the steel reinforcing layer is set to T2> T1.

JP-A-3-262711

  However, in the heavy-duty pneumatic tire described in Patent Literature 1, the rubber thickness of the rubber material increases toward the ends of the carcass layer and the steel reinforcing layer. That is, since the rubber material is formed in a wedge shape from the ends of the carcass layer and the steel reinforcing layer toward the inside in the tire radial direction, cracks in the tire width direction from the ends of the steel reinforcing layer, or from the ends of the carcass layer There is a possibility that a crack toward the carcass layer on the inner side in the tire width direction may occur.

  This invention is made in view of the above, Comprising: It aims at providing the heavy-duty pneumatic tire which can improve the durability of a bead part.

  In order to solve the above-described problems and achieve the object, a heavy-duty pneumatic tire according to the present invention includes a carcass layer that is folded from the inside in the tire width direction to the outside in the tire width direction around the bead core in the bead portion, and the carcass layer. A heavy-duty pneumatic tire comprising a steel reinforcing layer folded back from the inner side in the tire width direction to the outer side in the tire width direction on the outer periphery of the tire and a rim cushion rubber disposed on the outer periphery of the steel reinforcing layer. In the no-load state filled with normal internal pressure, on the bead heel side, an intersection where a reference line extending in the tire width direction of the bead core and extending in the tire width direction intersects the inner peripheral surface of the steel reinforcing layer And a cushioning rubber disposed between the carcass layer and the steel reinforcing layer from the intersection point toward the outer side in the tire radial direction, the reference From the reference line to the tire radial direction outer end of the steel reinforcing layer, and from the reference line to the carcass layer. The relationship with the tire radial direction dimension HC up to the outer end in the tire width direction is set to HS <H ≦ HC, and the carcass layer is formed in a convex shape on the inner side in the tire width direction at the portion where the buffer rubber is disposed. It is characterized by being.

  According to this heavy-duty pneumatic tire, the shock absorbing rubber is disposed on the inner side in the tire width direction of the outer end of the steel reinforcing layer in the tire width direction. Moreover, due to the convex shape of the carcass layer inward in the tire width direction, the outer end of the steel reinforcing layer in the tire width direction does not deviate greatly from the end of the carcass layer in the tire width direction. For this reason, even when shear stress concentrates on the part that receives the reaction force from the rim flange and contacts the rim flange due to the bead part falling down and deforming toward the outer side in the tire width direction when rolling the tire, Since a sufficient rim cushion rubber gauge can be secured at the outer end in the tire width direction of the reinforcing layer, separation caused by the outer end in the tire width direction of the steel reinforcing layer is suppressed. In addition, the carcass layer has a convex shape toward the inner side in the tire width direction, and the stress caused by the reaction force from the rim is alleviated by both the rim cushion rubber disposed on the outer periphery of the steel reinforcing layer and the cushion rubber disposed on the convex portion. be able to. As a result, the durability of the bead portion can be improved.

  The heavy duty pneumatic tire of the present invention is characterized in that the cushion rubber 100% modulus MB is set to MB ≦ MR with respect to the rim cushion rubber 100% modulus MR.

  According to this heavy duty pneumatic tire, the buffer rubber is bent when the shear stress is concentrated by setting the 100% modulus MB of the buffer rubber equal to or less than the 100% modulus MR of the rim cushion rubber. The effect can be remarkably obtained.

  The heavy duty pneumatic tire of the present invention includes a straight line connecting the intersection and the outer end in the tire width direction of the carcass layer, and a straight line connecting the intersection and the outer end in the tire width direction of the steel reinforcing layer. The angle α is set in a range of 0 [°] ≦ α ≦ 5 [°].

  According to this heavy duty pneumatic tire, when the angle α is 5 ° or less, the outer end of the steel reinforcing layer in the tire width direction is prevented from spreading toward the outer side in the tire width, thereby Prevents thinning of the rubber gauge on the outer side in the tire width direction (bead heel side). As a result, since the concentration of the shear stress is suppressed, the durability of the bead portion can be further improved.

  Further, the heavy duty pneumatic tire of the present invention is configured such that the cushion rubber has a maximum thickness from the reference line to the tire radial dimension HS from the reference line to the outer end in the tire width direction of the steel reinforcing layer. The tire radial direction dimension HG up to the direction outside point is set to 0.3 ≦ HG / HS.

  According to this heavy-duty pneumatic tire, it is preferable that the bead portion is designed so as to contact the rim flange at the position of the reference line in order to obtain the strength of the rim assembly. In this regard, according to this heavy-duty pneumatic tire, by setting HG / HS to be 0.3 or more, the portion where the cushion rubber has the maximum thickness Tmax from the tire radial position in contact with the rim flange extends in the tire radial direction. Separated. As a result, since the concentration of the shear stress is suppressed, the durability of the bead portion can be further improved.

  The heavy duty pneumatic tire of the present invention is characterized in that the minimum thickness of the bead filler at the outer width direction end of the carcass layer is set to 10.5 [mm] or more.

  According to this heavy-duty pneumatic tire, the crack toward the bead filler at the position of the outer end in the tire width direction of the carcass layer can be suppressed by setting the minimum thickness of the bead filler.

  The heavy-duty pneumatic tire according to the present invention can improve the durability of the bead portion.

FIG. 1 is a meridional sectional view showing a bead portion of a heavy duty pneumatic tire according to an embodiment of the present invention. FIG. 2 is a partially enlarged view of FIG. FIG. 3 is a chart showing the results of performance tests of heavy duty pneumatic tires according to examples 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.

  In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the heavy-duty pneumatic tire, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire radial direction. The outside refers to the side away from the rotation axis in the tire radial direction. Further, the tire width direction means a direction parallel to the rotation axis, the inner side in the tire width direction is the side facing the tire equator plane in the tire width direction, and the outer side in the tire width direction is separated from the tire equator plane in the tire width direction. Say the side. Further, the tire circumferential direction refers to a direction around the rotation axis as a central axis.

  The heavy-duty pneumatic tire according to the present embodiment has a tread portion (not shown) that is formed on the outermost portion in the tire radial direction and comes into contact with the road surface at the time of traveling. A sidewall portion (not shown) is provided up to a predetermined position inside the tire radial direction. And the bead part 1 shown in FIG. 1 is provided in the tire radial direction inner side of the sidewall part. The bead portion 1 is provided at two positions at symmetrical positions on the tire equatorial plane of the heavy duty pneumatic tire, and is a portion that fits into the rim base 21 of the rim 2. In FIG. 1, only one of the bead portions 1 (left side of the meridional section) is shown.

  The bead portion 1 is mainly provided with a bead core 11, a carcass layer 12, a bead filler 13, a steel reinforcing layer 14, and a rim cushion rubber 15.

  The bead core 11 is formed by bundling a plurality of bead wires, which are steel wires, and winding them in a ring shape in the tire circumferential direction.

  The carcass layer 12 is a steel cord covered with a rubber material. The carcass layer 12 is wound in a toroidal shape in the tire circumferential direction, and the end of the steel cord in the tire width direction is the inner side in the tire width direction (bead toe). The tire skeleton is constituted by being rolled back from the side) to the outside in the tire width direction (bead heel side) through the inside in the tire radial direction of the bead core 11. The steel cord of the carcass layer 12 is provided with an angle of approximately 90 degrees (radial direction) with respect to the tire equator line of the heavy duty pneumatic tire.

  The bead filler 13 is a rubber material disposed on the inner side where the carcass layer 12 is folded.

  The steel reinforcing layer 14 is made of a steel cord, and is disposed along the outer periphery of the carcass layer 12 wound around the bead core 11.

  The rim cushion rubber 15 is disposed on the outer side in the tire width direction of the carcass layer 12 and on the outer end in the tire width direction of the steel reinforcing layer 14 among the rubber materials disposed on the outer periphery of the carcass layer 12. Is. In the rim cushion rubber 15 in the present embodiment, 100% modulus MR according to JIS K 6251 is set in a range of 2.0 [MPa] ≦ MR ≦ 3.5 [MPa].

  In such a configuration, the heavy-duty pneumatic tire according to the present embodiment includes the cushion rubber 16. The shock absorbing rubber 16 is attached to a normal rim, and in a no-load state in which normal internal pressure is filled, on the bead heel side, a reference line S that passes through the outermost end 11a in the tire width direction of the bead core 11 and extends in the tire width direction is The intersection point P intersecting with the inner peripheral surface of the steel reinforcing layer 14 is a base point, and is disposed between the carcass layer 12 and the steel reinforcing layer 14 from the intersection point P toward the outer side in the tire radial direction.

  Here, the regular rim is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, “standard rim” for JATMA, “Design Rim” for TRA, ETRTO means “Measuring Rim”. In addition, the normal internal pressure is an air pressure determined by the standard for each tire, for example, “maximum air pressure” for JATMA, maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for TRA, If it is ETRTO, it means “INFLATION PRESSURES”.

  The buffer rubber 16 is configured as a tire radial direction dimension H from the reference line S to the tire radial direction outer end. And this dimension H, the tire radial direction dimension HS from the reference line S to the outer end in the tire width direction of the steel reinforcing layer 14, and the tire radial direction dimension HC from the reference line S to the outer end in the tire width direction of the carcass layer 12 Is set to HS <H ≦ HC.

  Further, in the portion where the buffer rubber 16 is disposed, the carcass layer 12 is formed in a convex shape on the inner side in the tire width direction. That is, the buffer rubber 16 is formed to protrude in a convex shape toward the carcass layer 12 side.

  That is, according to the heavy-duty pneumatic tire according to the present embodiment, the shock absorbing rubber 16 is disposed on the inner side in the tire width direction of the outer end of the steel reinforcing layer 14 in the tire width direction. In addition, due to the convex shape of the carcass layer 12 inward in the tire width direction, the outer end in the tire width direction of the steel reinforcing layer 14 does not deviate greatly from the end in the tire width direction of the carcass layer 12 in the tire width direction. For this reason, the shear stress concentrates on the part that receives the reaction force from the rim flange 22 and contacts the rim flange 22 due to the bead portion 1 falling and deforming toward the outer side in the tire width direction when the tire is loaded and rolled. In addition, since a sufficient rim cushion rubber gauge can be secured at the outer end of the steel reinforcing layer 14 in the tire width direction, separation due to the outer end of the steel reinforcing layer 14 in the tire width direction is suppressed. Further, due to the convex shape on the inner side in the tire width direction of the carcass layer 12, both the rim cushion rubber disposed on the outer periphery of the steel reinforcing layer 14 and the shock absorbing rubber 16 disposed on the convex portion are caused by the reaction force from the rim. It is possible to relax.

  Further, in the heavy duty pneumatic tire of the present embodiment, 100% modulus MB of the cushion rubber 16 according to JIS K 6251 is set to MB ≦ MR with respect to the 100 [%] modulus MR of the rim cushion rubber 15. . Specifically, the 100% modulus MB of the buffer rubber 16 is preferably set in a range of 2.0 [MPa] ≦ MB ≦ 3.0 [MPa].

  According to this heavy duty pneumatic tire, the buffer rubber 16 is bent when the shear stress is concentrated by setting the 100% modulus MB of the buffer rubber 16 to be equal to or less than the 100% modulus MR of the rim cushion rubber 15. Therefore, the above effects can be obtained remarkably.

  Further, as shown in FIG. 2, the heavy duty pneumatic tire of the present embodiment includes a straight line LC connecting the intersection P and the outer end in the tire width direction of the carcass layer 12, and the tire width of the intersection P and the steel reinforcing layer 14. The angle α around the intersection P formed by the straight line LS connecting the outer ends in the direction is set in a range of 0 [°] ≦ α ≦ 5 [°].

  According to this heavy duty pneumatic tire, when the angle α is 5 ° or less, the outer end of the steel reinforcing layer 14 in the tire width direction is prevented from spreading outward in the tire width direction, and the bead portion thereby formed 1 to prevent the rubber gauge on the outer side in the tire width direction (bead heel side) from thinning. As a result, since the concentration of the shear stress is suppressed, the durability of the bead portion 1 can be further improved.

  Further, as shown in FIG. 1, the heavy duty pneumatic tire of the present embodiment is buffered from the reference line S with respect to the tire radial dimension HS from the reference line S to the outer end of the steel reinforcing layer 14 in the tire width direction. The tire radial direction dimension HG up to the outer point in the tire width direction where the rubber 16 has the maximum thickness Tmax is set to 0.3 ≦ HG / HS.

  The bead portion 1 is preferably designed so as to contact the rim flange 22 at the position of the reference line S in order to obtain rim assembly strength. In this regard, according to this heavy duty pneumatic tire, when HG / HS is set to 0.3 or more, the portion where the cushioning rubber 16 has the maximum thickness Tmax from the position in the tire radial direction contacting the rim flange 22 is the tire diameter. Separated in the direction. As a result, since the concentration of the shear stress is suppressed, the durability of the bead portion 1 can be further improved. Note that HG / HS is preferably set in a range of 0.3 ≦ HG / HS ≦ 1.0 in order to suppress the concentration of shear stress and to obtain a remarkable effect of the suppression.

  In the heavy duty pneumatic tire of the present embodiment, the minimum thickness W of the bead filler 13 at the position of the outer end in the tire width direction of the carcass layer 12 is set to 10.5 [mm] or more.

  According to this heavy-duty pneumatic tire, by setting the minimum thickness W of the bead filler 13, it is possible to suppress cracks toward the bead filler 13 at the position of the outer end of the carcass layer 12 in the tire width direction.

  In the present embodiment, a performance test on bead portion durability was performed on a plurality of types of heavy-duty pneumatic tires having different conditions (see FIG. 3).

  In this performance test, a heavy-duty pneumatic tire having a tire size of 11R22.5 was assembled to a regular rim, filled with a regular internal pressure, and 150% of the regular load was applied. 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 means the “maximum load capacity” defined in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “LOAD CAPACITY” defined in ETRTO.

  The evaluation method is as follows. Performance test (1) of bead part durability is performed by attaching a test tire to an indoor drum testing machine, traveling at 15,000 [km] at a speed of 45 [km / h], and then determining the position of the tire. A fan-shaped sample cut in eight equal parts on the tire circumference was created using the meridional section as the base point, and each section (16 sections in total) was observed to measure the number of cracks between the steel reinforcing layer and the rim cushion rubber. Based on the result, index evaluation is performed with the conventional example as a reference (100). This evaluation shows that the larger the numerical value, the fewer the cracks and the better the durability.

  In the performance test (2) of the bead part durability, the test tire is mounted on an indoor drum tester, traveled at a speed of 45 [km / h], and traveled until the heavy-duty pneumatic tire is destroyed. Based on this result, index evaluation is performed with the conventional example as a reference (100). This evaluation shows that the larger the numerical value, the fewer the cracks and the better the durability of the entire bead portion.

  The conventional heavy-duty pneumatic tire does not include a cushion rubber. The heavy-duty pneumatic tire of the comparative example includes a buffer rubber, but the tire radial dimension from the reference line: HS <H ≦ HC, the convex shape of the carcass layer, the 100% modulus of the buffer rubber, and the rim cushion rubber 100% modulus relationship: MB ≦ MR, angle between carcass layer and steel reinforcing layer: α, position relationship of buffer rubber maximum thickness Tmax: HG / HS, and bead filler gauge: W is not optimized. On the other hand, the heavy-duty pneumatic tires of Examples 1 to 8 are provided with a buffer rubber, and the tire radial direction dimension from the reference line: HS <H ≦ HC and the convex shape of the carcass layer are optimized. Yes. In the heavy duty pneumatic tire of Example 2, the relationship between the 100% modulus of the cushioning rubber and the 100% modulus of the rim cushion rubber: MB ≦ MR is optimized. In the heavy duty pneumatic tires of Example 3 and Example 4, the angle α between the carcass layer and the steel reinforcing layer is further optimized. Further, in the heavy duty pneumatic tires of Example 5 and Example 6, the positional relationship of the buffer rubber maximum thickness Tmax: HG / HS is optimized. Further, in the heavy duty pneumatic tires of Example 7 and Example 8, the bead filler gauge W is further optimized.

  As shown in the test results of FIG. 3, the heavy-duty pneumatic tires of Examples 1 to 8 are free from cracks between the steel reinforcing layer and the carcass layer, compared with the conventional example and the comparative example, It can be seen that the durability of the bead portion is improved.

  As described above, the heavy duty pneumatic tire according to the present invention is suitable for improving the durability of the bead portion.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Rim 21 Rim base 22 Rim flange 11 Bead core 11a Outermost end in the tire width direction 12 Carcass layer 13 Bead filler 14 Steel reinforcement layer 15 Rim cushion rubber 16 Buffer rubber S Reference line P Passes the outermost end of the bead core in the tire width direction And the intersection where the reference line extending in the tire width direction intersects the inner peripheral surface of the steel reinforcing layer H The tire radial dimension from the reference line to the outer end of the cushion rubber in the tire radial direction HC The reference line to the tire width of the carcass layer Dimension in the tire radial direction to the outer edge in the tire direction Dimension in the tire radial direction from the HS reference line to the outer edge in the tire width direction of the steel reinforcing layer HG A tire radial direction dimension from the reference line to the outer point in the tire width direction where the cushioning rubber becomes the maximum thickness MB 100% modulus of buffer rubber MR 100% modulus of rim cushion rubber LC Angle linear α linearly LC, the LS is formed connecting the tire width direction outer end of the straight line LS intersection and steel reinforcing layers connecting the tire width direction outer end of the carcass layer and

Claims (5)

A carcass layer folded from the inside in the tire width direction to the outside in the tire width direction around the bead core in the bead portion, a steel reinforcing layer folded from the inside in the tire width direction to the outside in the tire width direction on the outer periphery of the carcass layer, and the steel reinforcement In a heavy duty pneumatic tire provided with a rim cushion rubber disposed on the outer periphery of the layer,
A reference line extending in the tire width direction through the tire width direction outermost end of the bead core on the bead heel side in an unloaded state in which the normal rim is mounted and filled with a normal internal pressure is an inner circumference of the steel reinforcing layer. A shock absorbing rubber disposed from the intersection point to the outer side in the tire radial direction between the carcass layer and the steel reinforcing layer, with an intersection point intersecting the surface as a base point,
A tire radial dimension H from the reference line to the outer end in the tire radial direction of the buffer rubber, a tire radial dimension HS from the reference line to an outer end in the tire width direction of the steel reinforcing layer, and the reference line to the above The relationship between the carcass layer and the tire radial direction dimension HC up to the outer end in the tire width direction is set to HS <H ≦ HC, and the carcass layer has a convex shape on the inner side in the tire width direction at the portion where the buffer rubber is disposed. A heavy duty pneumatic tire characterized by being formed.   2. The heavy duty pneumatic tire according to claim 1, wherein a 100% modulus MB of the cushion rubber is set to MB ≦ MR with respect to a 100 [%] modulus MR of the rim cushion rubber. 3.   An angle α formed by a straight line connecting the intersection and the outer end in the tire width direction of the carcass layer and a straight line connecting the intersection and the outer end in the tire width direction of the steel reinforcing layer is 0 [°] ≦ α ≦ 5 The heavy duty pneumatic tire according to claim 1 or 2, wherein the pneumatic tire is set in a range of [°].   The tire radial direction dimension HG from the reference line to the outer point in the tire width direction where the buffer rubber has the maximum thickness is compared to the tire radial direction dimension HS from the reference line to the outer end in the tire width direction of the steel reinforcing layer. The heavy-duty pneumatic tire according to claim 1, wherein 0.3 ≦ HG / HS is set.   The heavy load according to any one of claims 1 to 4, wherein a minimum thickness of the bead filler at a position of the outer end in the tire width direction of the carcass layer is set to 10.5 [mm] or more. Heavy duty pneumatic tire.

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