JP2006096153A - Pneumatic radial tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further improve durability of a belt, in a pneumatic radial tire for heavy load having the belt of a three-layered structure for reducing weight. <P>SOLUTION: In this radial tire 1, an inner liner 5 and the belt 6 made of three rubber coated cord layers are provided. An inclined angle of each cord 7a and 8a of an innermost cord layer 7 and an intermediate cord layer 8 of the belt 6 is made 10 to 25° in relation to plane including the circumference of a tread part. An inclined angle of a cord 9a of an outermost cord layer 9 is made 45 to 115°. The outermost cord layer 9 is made to have a width extending beyond an outermost side groove edge of an outermost side peripheral direction groove 12 toward an end of the tread part. A compressive elastic modulus of the coated rubber 9b of the outermost cord layer 9 is 200 kgf/cm<SP>2</SP>or more. A rubber composition made by blending layered or planar mineral having an aspect ratio of ≥3 and ∠30 in relation to a rubber component is applied to the inner liner 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heavy-duty pneumatic radial tire, and more particularly to a tire for heavy vehicles such as trucks and buses. In particular, the belt is composed of three rubber-coated cord layers for weight reduction, and an inner liner. By applying a rubber composition that contains a layered or plate-like mineral to the tire, the belt rubber is improved in deterioration resistance while maintaining the tire weight, and as a result, the belt is improved in cut resistance and travels on rough roads. This relates to a long-life pneumatic radial tire for heavy loads with improved durability.

  In heavy-duty pneumatic radial tires used for heavy vehicles such as trucks and buses, the tread belt is generally composed of four rubber-coated cord layers, and the cord of the first cord layer located closest to the carcass is treaded. Are arranged at a relatively large inclination angle with respect to a plane including the circumference of the portion (that is, a plane parallel to the tire equatorial plane E), and the cords of the second cord layer and the third cord layer intersect with each other across the plane. (For this reason, the second code layer and the third code are called the code crossing layers), and the fourth code layer code is arranged in the same direction as the third code layer code, and the inclination angle is also the third code. The inclination angle is almost the same as the layer code. A steel cord is generally used as the cord of the belt cord layer.

  When a tire having a belt composed of the above four rubber-coated cord layers rolls under a load on a rough road, for example, a rough road where crushed stones and small rocks are scattered, the tread portion is crushed stone and small rocks. Stepping on the sharp corners of the belt often leads to cut wounds that reach the belt. Therefore, the main role of the fourth cord layer is protected so that the belt's cut injury is stopped at the fourth cord layer, which is the outermost cord layer, with the aim of avoiding even the slightest possible belt damage due to the cut. Layered configurations have been proposed.

  On the other hand, as with pneumatic radial tires for passenger cars, there is an increasing demand for weight reduction for heavy duty pneumatic radial tires, and belts that occupy a large proportion of the weight of the tire are changed from four cord layers to three cord layers. Has been proposed. In the belt composed of the three-layer cord layers, the cords of the first cord layer closest to the carcass are arranged at a relatively large inclination angle with respect to the plane described above, and the second cord layer and the third cord layer are touched first. A cord crossing layer is used, and each cord of the cord crossing layer is arranged with a relatively small inclination angle with respect to the plane.

  Regarding tires having this type of three-layer belt configuration, for example, a tire described in Japanese Patent Laid-Open No. 7-186613 (the following Patent Document 1) includes a belt composed of three cord layers (breakers) and counted from the carcass. Under the knowledge that the third third code layer has the least strength, the third code layer is characterized in that the strength per unit width of the third code layer is higher than that of the first code layer and the second code layer. As a result, when the tread portion of the tire rides on foreign matter such as crushed stones and small rocks, at least the cord of the third cord layer is stopped, and a fatal failure such as a burst can be prevented at low cost and effectively. Yes.

  However, when actually verifying the tire described in JP-A-7-186613, the belt of the tire has the second cord layer and the third cord layer as a cross cord layer, and the cross angle of the cords of these layers. Therefore, when the tire is filled with a predetermined internal pressure, a large tension acts on the cords of the second cord layer and the third cord layer, and the cord strength per unit width of the third cord layer ( Specifically, it was found that even if the tensile strength was increased, cord breakage due to foreign matters such as crushed stones and small rocks could not be sufficiently suppressed. This is because a cord on which a large tension is applied has a significantly reduced remaining force against the cut input.

  Also, when the tread part of the tire rides on a large amount of foreign matter such as crushed stones or rocks on the road surface, bending force acts on the belt, resulting in local buckling (back Ring) phenomenon is likely to occur, and repeated buckling repeatedly causes fatigue of the cord and eventually leads to failure leading to cord breakage.

  Furthermore, when the tread part of a tire that rolls under a load load rides on crushed stones and small rocks, the tread part is a groove provided in the tread rubber to form a pattern in the tread part, particularly in the both sides of the tread part. When the sharp corner edges of crushed stones and small rocks bite into the circumferential grooves extending in the circumferential direction, the tread rubber thickness from the circumferential groove bottom to the belt is thin, so the sharp corner edges of crushed stones and small rocks are relatively The belt easily penetrates the tread rubber to reach the belt, and there is a problem that sharp corner edges of crushed stones and small rocks easily cut the belt.

On the other hand, Japanese Patent Laid-Open No. 2000-153702 (Patent Document 2 below) includes a belt comprising three layers of an innermost cord layer, an intermediate cord layer, and an outermost cord layer, and an innermost cord layer and an intermediate cord layer. The cord layer is a cord crossing layer, and the inclination angle of each cord of the innermost cord layer and the intermediate cord layer is 10 to 25 ° with respect to the tire equator plane, and the cord of the outermost cord layer is 45 with respect to the tire equator plane. With an inclination angle of ˜115 °, and further, by keeping the compression elastic modulus of the cord-coated rubber of the outermost cord layer at 200 kgf / cm ² or more, while maintaining the weight reduction of the tire, the separation resistance of the belt, While the cornering performance, etc. is equal to or better than that of conventional tires, the belt's overall cut resistance, including the cut resistance in the circumferential grooves on both sides of the tread portion of the tread pattern on rough roads, and the outermost belt Over de layer encoding long life heavy duty pneumatic radial tire with greatly improved and fatigue resistance typified by the breakage resistance have been disclosed.

JP-A-7-186613 JP 2000-153702 A

  However, even in the tire described in Japanese Patent Laid-Open No. 2000-153702, the oxygen concentration in the cord-coated rubber of the cord layer increases due to oxygen that permeates from the inside of the tire and reaches the belt, and the cord-coated rubber is deteriorated by oxygen. There is a problem that durability is lowered.

  On the other hand, it is particularly effective to increase the gauge of the inner liner in order to suppress an increase in the oxygen concentration in the belt cord-coated rubber. However, in this case, since the tire weight increases, the temperature of the rubber constituting the tire case increases during traveling, and as a result, the air (oxygen) permeation rate of the case rubber increases, and the cord-coated rubber of the belt There is a problem that oxygen deteriorates.

  Therefore, an object of the present invention is to solve the above-mentioned problems and to reduce the weight by constituting the belt with three cord layers, and without increasing the thickness of the inner liner gauge, An object of the present invention is to provide a heavy-duty pneumatic radial tire for a long life that suppresses an increase in oxygen concentration and greatly improves the durability of the belt.

  As a result of intensive studies to achieve the above object, the present inventor makes the structure of the belt composed of three cord layers a specific structure and has a specific aspect ratio in the rubber composition applied to the inner liner. By blending layered or plate-like minerals, the belt cuts the air (oxygen) permeation rate of the inner liner while significantly improving the cut resistance of the belt and the fatigue resistance of the outermost cord layer cord of the belt. As a result, it was found that the durability of the cord-coated rubber can be greatly improved, and the present invention has been completed.

That is, the heavy duty pneumatic radial tire of the present invention is
A carcass made of one or more ply rubber-coated radial array cords that reinforces the pair of sidewall portions and the tread portion between the bead cores embedded in the pair of bead portions; an inner liner disposed inside the carcass; A belt that reinforces the tread portion on the outer periphery of the carcass, and the belt is composed of three rubber-coated cord layers, and the innermost cord layer and the intermediate cord layer of the cord layers have a tread portion circle. In a heavy-duty pneumatic radial tire that forms a cord crossing layer that intersects with each other across a plane including the circumference, and the tread portion includes at least one circumferential groove in each of its both side regions,
The inclination angle of each cord of the innermost cord layer and the intermediate cord layer is 10 to 25 ° with respect to the plane, and the inclination angle of the cord of the outermost cord layer is different from the plane of the cord of the intermediate cord layer. Measured in the same direction as the direction of measuring the inclination angle, the width is 45 to 115 ° with respect to the plane, and the outermost cord layer extends beyond the outermost groove edge of the outermost circumferential groove toward the tread end. Having a compression elastic modulus of the cord-coated rubber of the outermost cord layer of 200 kgf / cm ² or more,
A rubber composition comprising a layered or plate-like mineral having an aspect ratio of 3 or more and less than 30 with respect to the rubber component is applied to the inner liner.

  Here, the compression elastic modulus is a value calculated according to the following method. That is, a rubber test piece is filled in a hollow portion of a metal jig having a cylindrical cavity with a diameter d of 14 mm and a height h of 28 mm, for example, steel, without gaps, and this jig is used as a compression tester. Set and load a load w on the upper and lower surfaces of the rubber test piece at a speed of 0.6 mm / min, measure the amount of displacement of the rubber test piece at this time with a laser displacement meter, and compressive elasticity from the relationship between the load w and displacement Calculate the rate.

  Further, the both side regions of the tread portion refer to both side regions of a central region in which the tread width of the tread portion is equally divided into four and the quarter width is distributed to both sides of the tire equator surface.

  In a preferred example of the heavy-duty pneumatic radial tire of the present invention, the surface of the layered or plate-like mineral is oriented in a direction crossing the thickness direction of the inner liner.

  In another preferred embodiment of the heavy-duty pneumatic radial tire of the present invention, at least one cord layer end portion of the innermost cord layer and the intermediate cord layer has a sheet-like end cover rubber that wraps around the end portion, At least one of the inner and outer surfaces of the end portion of the cord layer having the end cover rubber has a corrugated surface that forms a crest at a position where the cord exists and a trough at a position between adjacent cords. The height difference between them is 0.05 to 0.25 mm.

  In another preferred embodiment of the heavy-duty pneumatic radial tire of the present invention, at least one of the innermost cord layer and the intermediate cord layer has a rubber layer bonded to the entire width of the cord layer, and the rubber. The width of the layer is 0.05 to 5.00 mm.

In the inner liner of the heavy-duty pneumatic radial tire of the present invention, the rubber component comprises 40 to 100% by mass of butyl rubber and 60% by mass or less of diene rubber, and the layer or plate with respect to 100 parts by mass of the rubber component The amount A (parts by mass) of the mineral and the thickness D (mm) of the inner liner are expressed by the following formula (I):
1 <A × D <200 (I)
It is preferable to satisfy this relationship. Here, the butyl rubber preferably includes halogenated butyl rubber. More preferably, the halogenated butyl rubber is at least one butyl rubber selected from the group consisting of brominated butyl rubber and chlorinated butyl rubber.

  In the inner liner of the heavy duty pneumatic radial tire of the present invention, the rubber component preferably contains 60 to 100% by mass of a diene rubber. In this case, the heavy-duty pneumatic radial tire of the present invention is suitable as an aircraft tire or a truck / bus tire used under cryogenic conditions.

  Moreover, as the layered or plate-like mineral, kaolin clay, sericite clay, and a hydrous composite of silica and alumina are preferable.

The rubber composition applied to the inner liner is further softened with 0.1 to 40 parts by mass of carbon black having a nitrogen adsorption specific area (N ₂ SA) of 26 to 170 m ² / g with respect to 100 parts by mass of the rubber component. What mix | blends 1 mass part or more of agents is preferable. Here, the compounding amount of the layered or plate-like mineral is 20 to 160 parts by mass with respect to 100 parts by mass of the rubber component, and the total compounding amount of the layered or plate-like mineral and the carbon black is the rubber. More preferably, the rubber composition is 60 to 220 parts by mass with respect to 100 parts by mass of the component. Further, 10 to 50 parts by mass of the layered or plate-like mineral and 10 to 60 parts by mass of the carbon black are blended with 100 parts by mass of the rubber component, and the rubber component is selected from butyl rubber and halogenated butyl rubber. A rubber composition comprising at least one butyl rubber is also preferable, and it is further preferable that the total amount of the layered or plate-like mineral and the carbon black is 50 parts by mass or more with respect to 100 parts by mass of the rubber component. The carbon black preferably has an iodine adsorption of 40 mg / g or less and a dibutyl phthalate oil absorption of 100 mL / 100 g or less.

  According to the present invention, the weight of a tire is maintained by applying a rubber composition in which a belt is composed of three cord layers to reduce the weight of a tire and a layered or plate-like mineral is blended in an inner liner. Reducing the air (oxygen) permeation speed of the inner liner, greatly improving the durability of the belt cord-coated rubber, and as a result, improving the belt's cut resistance and improving durability on rough roads. It is possible to provide a heavy-duty pneumatic radial tire with a long service life that is significantly improved.

  The heavy duty pneumatic radial tire of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view in which a part of a tread portion of a heavy-duty pneumatic radial tire according to the present invention is taken out, a part of the tread rubber is cut out, and a belt and a carcass are exposed, and FIG. 2 is shown in FIG. It is explanatory drawing which shows the front development of a part of tread part of a tire, combines the belt development view which cut off the tread rubber, and gave the step-down cut, and the tread pattern development view. FIG. 3 is a perspective view of an example of one layer end of the cord cross layer of the belt, and FIG. 4 is an enlarged cross-sectional view of either layer end of the cord cross layer of the belt. FIG. 5 is a perspective view of another example of the layer end portion of one of the cord cross layers of the belt. FIG. 6 is a partial cross-sectional view of the inner liner of the tire according to the present invention.

  In FIG. 1, a heavy-duty pneumatic radial tire 1 has a pair of bead portions (not shown), a pair of sidewall portions (not shown), and a tread portion 2 connected to both sidewall portions. Has tread rubber 3 on the tread side. Further, the tire 1 has one or more plies (in the illustrated example, one ply) that reinforce the pair of bead portions, the pair of sidewall portions, and the tread portion 2 between bead cores (not shown) embedded in the pair of bead portions. A carcass 4 made of a rubber-coated radial array code, an inner liner 5 disposed inside the carcass 4, and a belt 6 that reinforces the tread portion 2 on the outer periphery of the carcass 4.

  1 and 2, the belt 6 is composed of three rubber-coated cord layers 7, 8, and 9, and the cords 7 a and 8 a of the innermost cord layer 7 and the intermediate cord layer 8 closest to the carcass 4 are tread portions. The innermost cord layer 7 and the intermediate cord layer 8 form a cord crossing layer 10 with a plane P including two circumferences (the tire equatorial plane in the illustrated example) sandwiched therebetween. The cord 7a of the innermost cord layer 7 and the cord 8a of the intermediate cord layer 8 are inclined with respect to the plane P within a range of 10 to 25 °, preferably within a range of 15 to 22 °. The measurement direction of the inclination angle δ with respect to the plane P of the cord 7a is indicated by an arrow, and the measurement direction of the inclination angle α with respect to the plane P of the cord 8a is indicated by an arrow. Although the plane P shown in FIGS. 1 and 2 exists on the tire equatorial plane, the plane P may be located on any of the tread portions 2.

In the lower view of FIG. 2, the cord 9a of the outermost cord layer 9 has the same direction (in the direction of the arrow in the drawing) as the direction of measuring the inclination angle α from the plane P of the cord 8a of the intermediate cord layer 8 (the direction of the arrow in the drawing). ) Measured with respect to the plane P and having an inclination angle β in the range of 45 to 115 °, preferably in the range of 50 to 100 °, and the covering rubber 9b of the cord 9a of the outermost cord layer 9 is 200 kgf. / cm ² and having a higher compression modulus.

  In the development view of the tread pattern shown in the upper part of FIG. 2, the tread pattern of the tire includes four circumferential grooves 11 and 12 formed in the tread rubber 3 (see FIG. 1) and extending straight in the circumferential direction. Each of the blocks 16, 17, 18 defined by the circumferential grooves 11, 11 adjacent to each other and a plurality of lateral grooves 13, 14, 15 opening in the circumferential grooves between the circumferential grooves 11, 12. A block row is provided in the central region of the tread portion 2, and both row regions of the tread portion are provided with block rows of blocks 20 that are partitioned by a circumferential groove 12 and a plurality of lateral grooves 19 that open to the circumferential groove 12.

  The example shown in FIG. 2 is an example of a block pattern in which the entire region of the tread portion 2 is formed of blocks, but the tread portion 2 of the tire of the present invention has one or more circumferential grooves (see FIG. In the example shown in the figure, a single circumferential groove) 12 is provided, and the central region may be a land portion such as a rib other than the block, and both side regions of the tread portion 2 may be similar ribs, that is, the tread portion. 2 can be entirely a rib pattern or a combination pattern of ribs and blocks. In the illustrated example, the circumferential grooves 11 and 12 are straight grooves, but may be zigzag grooves.

In the tire according to the present invention, the outermost cord layer 9 includes the tread portion beyond the outermost groove edge of the outermost circumferential groove (circumferential groove 12 in the illustrated example) among the circumferential grooves on both sides of the tread portion 2. It shall have the width extended toward the edge of 2. This is the same for the circumferential grooves 12 located on either side. In the developed view shown in FIG. 2, the width Lb of the outermost code layer 9 is made larger than the distance Lg between the planes P ₁ and P ₂ parallel to the plane P passing through the outermost groove edge of the circumferential groove 12. That is, the width end 9E of the outermost cord layer 9 is always located on the tire outer side from the planes P ₁ and P ₂ .

  In the tire of the present invention, the cord 7a of the innermost cord layer 7 and the cord 8a of the intermediate cord layer 8 are inclined with respect to the plane P within a range of 10 to 25 °, preferably within a range of 15 to 22 °. On the other hand, the cord 9a of the outermost code layer 9 is measured in the same direction as the direction of measuring the inclination angle α of the cord 8a of the intermediate cord layer 8 from the plane P, and within the range of 45 to 115 ° with respect to the plane P In the circumferential direction of the tread portion 2 generated in the belt 6 when the tire 1 is filled with the internal pressure, as indicated by an arrow Fx below the FIG. The tension Fx is mainly borne by the cord 7a and cord 8a of the innermost cord layer 7 and the intermediate cord layer 8 that form the cord crossing layer 10 having a small inclination angle with respect to the plane P, and the tension that the outermost cord layer 9 should bear. Can be greatly reduced. Therefore, even when the tread portion 2 of the tire 1 that rolls under a load load rides on a foreign object such as crushed stone or small rock having sharp corner edges, the corner edges penetrate the tread rubber 3 and reach the belt 6. The cord 9a of the outermost cord layer 9 is difficult to cut, and the durability of the tire 1 based on cut resistance is improved.

  In FIG. 2, the belt 6 has a tendency to protrude in the radial direction of the tire 1 due to the tension Fx generated in the belt 6 when the tire 1 is filled with the internal pressure. Shrinking inward, the cords 7a, 8a, 9a of the layers 7, 8, 9 of the belt 6 tend to change in the direction in which the inclination angles δ, α, β decrease, respectively. However, under the configuration of the belt 6, the cord 9a of the outermost cord layer 9 has an inclination angle β that is significantly larger than the inclination angles of the cords 7a and 8a of the innermost cord layer 7 and the intermediate cord layer 8, respectively. The degree of decrease in the inclination angle is extremely small compared to the cords 7a and 8a, and as a result, the outermost cord layer 9 is difficult to contract in the width direction. For this reason, the cord 9a of the outermost cord layer 9 acts on the cord crossing layer 10 like a so-called stick, and the outermost cord layer 9 works to suppress contraction in the width direction of the cord crossing layer 10. . In the cord crossing layer 10 in which the shrinkage in the width direction is suppressed, the circumferential rigidity of the tread portion 2 is increased, and as a result, the cornering power (hereinafter referred to as CP) is improved even in the tire 1 including the belt 6 having the three-layer configuration. Cornering performance equal to or better than that of a tire including a conventional belt having a four-layer structure can be exhibited. Furthermore, the increase in the circumferential rigidity of the cord crossing layer 10 greatly contributes to suppressing the tire diameter growth when the tire 1 is filled with the internal pressure.

Note that the inclination angles α and δ with respect to the planes P, P ₁ and P ₂ of the cords 7a and 8a of the innermost cord layer 7 and the intermediate cord layer 8 are mutually different from the viewpoint of equally applying tension to the cords 7a and 8a. It is preferable to make them approximately equal. The reason why the inclination angles α and δ of the cords 7a and 8a are within the range of 10 to 25 ° is that the end portions of the innermost cord layer 7 and the intermediate cord layer 8 when the inclination angles α and δ are less than 10 °. When the inclination angles α and δ exceed 25 °, the tension Fx acting on the belt 6 in the internal pressure-filled tire 1 becomes the maximum. The effect of suppressing the shrinkage in the width direction of the outer cord layer 9 is not sufficiently exerted, the rigidity in the circumferential direction of the cord crossing layer 10 is remarkably lowered, the CP characteristics are deteriorated, and the tire diameter growth can be sufficiently suppressed. Because it disappears. Furthermore, the inclination angle β of the cord 9a of the outermost cord layer 9 is set within the range of 45 to 115 °, even if the inclination angle β is less than 45 ° or the inclination angle β exceeds 115 °, compared to the conventional tire. This is because the CP characteristics deteriorate.

Further, when the tire 1 rolls on a road surface on which foreign matters such as relatively large crushed stones and rocks are scattered and rides on these large foreign matters, the outermost cord layer 9 of the belt 6 is strongly bent and deformed with a large curvature. As a result, when a large compressive force acts locally and buckling occurs in the cord 9a of the outermost cord layer 9, the compression elastic modulus of the covering rubber 9b of the cord 9a of the outermost cord layer 9 is 200 kgf / cm ² or more. By applying this rubber, it becomes possible to increase the compression resistance of the covering rubber 9b and to prevent the buckling deformation of the cord 9a of the outermost cord layer 9. As a result, even if the tire 1 often rides on foreign matters such as relatively large crushed stones and rocks, the occurrence of cord breakage due to buckling fatigue of the cord 9a of the outermost cord layer 9 can be prevented. Note that this effect is insufficient when the compression elastic modulus of the covering rubber 9b is less than 200 kgf / cm ² .

  Even if sharp corner edges of foreign matter such as crushed stones and small rocks on the rolling road bite along the groove bottoms of the circumferential grooves 11 and 12 of the tire, the outermost cord layer 9 exists in both side regions of the tread. Since the width of the outermost circumferential groove 12 extends beyond the outermost groove edge toward the end of the tread portion 2, the corner edge of the foreign matter penetrates the thin tread rubber 3 below the groove bottom and the belt 6. Even in this case, there are always a large number of cords 9a in the outermost code layer 9, and these cords 9a exhibit sufficient resistance to cut input as described below.

When the corner edge of the foreign material bites along the groove bottom of the circumferential groove 12, the numerous cords 9a of the outermost cord layer 9 exist at the tip of the corner edge of the foreign material because the circumferential groove 12 is a straight groove. Then, the angle formed by the groove bottom and the cord 9a of the outermost cord layer 9 is 45 ° or more. In this respect, if the circumferential groove 12 is a zigzag groove, the groove plane P ₁ , The difference between the inclination angle with respect to P ₂ and the inclination angle of the cord 9a of the outermost cord layer 9 is preferably 20 ° or more. This is because if the difference in inclination angle is less than 20 °, the number of the cords 9a for receiving the entry of the corners of the foreign matter is too small.

  In any case, the cord 9a of the outermost cord layer 9 that receives the cut input of the sharp corner edge of the foreign matter has a small tension load ratio and a sufficient margin to resist the cut. Can be stopped at the outermost cord layer 9, and the cord 8a of the intermediate cord layer 8 can be prevented from being cut. For this reason, the outermost cord layer 9 needs to have a width that exceeds the outermost groove edge of the outermost circumferential groove 12 toward the tire outer side. If the circumferential groove 12 is a zigzag groove, the outermost cord layer 9 has a width extending beyond the groove edge apex at the outermost position of the mountain-shaped groove.

  As shown in FIG. 2, the width of the outermost code layer 9 (deployment width Lb) may be narrower than the width of the intermediate code layer 8, but in order to ensure complete cut resistance, Further, in order to further improve the separation resistance between the end portion of the innermost cord layer 7 forming the end portion of the cord crossing layer 10 and the intermediate cord layer 8, the width of the outermost cord layer 9 is set to the middle cord layer. The outermost code layer 9 may cover both width ends of the intermediate code layer 8 so as to have a width of 8 or more. By setting the width of the outermost code layer 9 to be equal to or greater than the width of the intermediate code layer 8, in the end region of the intermediate code layer 8, there is a code between the end of the intermediate code layer 8 and the end of the outermost code layer 9. As a result, a part of the shear rigidity of the cross layer 10 is taken over. As a result, the inter-layer shear strain of the cord cross layer 10 in the end region of the intermediate cord layer 8 is reduced, so that the separation failure is less likely to occur. Here, in practice, the width of the outermost code layer 9 is preferably in the range of 1.0 to 1.2 times the width of the intermediate code layer 8. This is because, as the width of the outermost cord layer 9 becomes wider, the tensile strain in the tire rotation axis direction at the end of the outermost cord layer 9 immediately below the load load of the tire increases, and the width of the outermost cord layer 9 becomes an intermediate cord. This is because if the width of the layer 8 exceeds 1.2 times, the tensile strain at the end of the outermost cord layer 9 becomes too large, and a separation failure is likely to occur at the end of the outermost cord layer 9.

  Further, in order to alleviate the interlaminar shear stress of the cord crossing layer 10, as shown in FIGS. 3 and 4, it is wrapped around at least one of the innermost cord layer 7 and the middle cord layer 8 in the width direction. It is preferable to dispose a sheet-like end cover rubber 21. At least one surface (in the illustrated example, both inner and outer surfaces 22a and 22b) of the innermost cord layer 7 provided with the end cover rubber 21, the inner surface 22a of the tire in the tire radial direction (hereinafter referred to as the radial direction) and the outer surface 22b in the radial direction. ) Forms a crest at the position where the cords 7a and 8a exist, and forms a trough at a position between the cords 7a and 8a adjacent to each other in the layer. In accordance with this, the surface 23 of the end cover rubber 21 also has a corrugated surface of peaks 23a and valleys 23b. The crest 23a corresponds to the existing position 24 of the cords 7a and 8a, and the trough 23b corresponds to the position 25 between the adjacent cords 7a and 8a. The height difference H between the peaks 23a and the valleys 23b is in the range of 0.05 to 0.25 mm. By providing this height difference H, it is possible to sufficiently suppress the occurrence of separation at the end portions of the innermost cord layer 7 and the intermediate cord layer 8 that form the cord intersection layer 10. Here, when the height difference H is less than 0.05 mm, there is practically no effect of suppressing the separation at the end of the cord crossing layer 10. On the other hand, when the height difference H exceeds 0.25 mm, unvulcanized tire molding is performed. At the time, when the cord layer members of the belt are stuck together, a large amount of air is wrapped in the recess that becomes the valley 23b in the tire 1, and this air wrapping part does not adhere to each other even by vulcanization molding of the unvulcanized tire. Separation occurs from the part.

  For example, the cord layer of the cord crossing layer 10 of the belt 6 may be formed by corrugating the innermost cord layer 7, the inner surface 22 a and the outer surface 22 b of the end portion of the intermediate cord layer 8, and the surface 23 of the end cover rubber 21. 7 and 8 unvulcanized cord layer members are produced by using a roll similar to a comb roll that aligns steel cords used in the production of long cord layer members with a calender roll in the arrangement direction. Examples include a method of pressing at least one end of at least an end portion of the vulcanized rubber-coated cord layer member, and a method of thinning the gauge of the unvulcanized coated rubber of the cords 7a and 8a. When the latter method is used, if the coated rubber gauge is too thin, the cords 7a and 8a are likely to be exposed at the stage of the unvulcanized member. Therefore, it is necessary to set the gauge in consideration of this.

  Further, as shown in FIG. 5, instead of the end cover rubber 21, a rubber layer 26 covering the entire circumference of the cord layer is bonded to the width end face of at least one of the innermost cord layer 7 and the intermediate cord layer 8. Also good. By providing the rubber layer 26, the protrusion of the end of the cord 7a of the innermost cord layer 7 and the end of the cord 8a of the intermediate cord layer 8 into the tread rubber 3 can be eliminated. Separation resistance can be improved. Here, the width W of the rubber layer 26 is preferably in the range of 0.05 to 5.00 mm. If the width W of the rubber layer 26 is less than 0.05 mm, the effect of suppressing the occurrence of separation failure is too small. If the width W exceeds 5.00 mm, the inner cord layer 7 The unvulcanized cord layer member and the unvulcanized cord layer member to be the rubber layer 26 when the unvulcanized cord layer member is fed from the feeding device for feeding the unvulcanized cord layer member of the intermediate cord layer 8 onto the molding drum. The rubber member hangs down or rolls up, and workability is impaired.

  In the case where the rubber layer 26 is provided, the end cover rubber 21 may not be provided, but both the rubber layer 26 and the end cover rubber 21 may be applied. In the case of both applications, the surface 23 of the end cover rubber 21 described above does not necessarily need to be the corrugated surfaces 23a and 23b. From the viewpoint of productivity, the rubber layer 26 is preferably made of the same composition rubber as the cord-coated rubber of the innermost cord layer 7 and the cord-coated rubber of the intermediate cord layer 8. In this case, the rubber layer 26 can protect the end of the cord 7a of the innermost cord layer 7 and the end of the cord 8a of the intermediate cord layer 8 with the same rubber, which is advantageous in improving the separation resistance. Further, the end cover rubber 21 preferably has a larger 100% modulus than the cord-covered rubber.

  In the heavy-duty pneumatic radial tire of the present invention, a rubber composition obtained by blending the inner liner 5 with a layered or plate-like mineral having an aspect ratio of 3 or more and less than 30 with respect to the rubber component is applied. As shown in FIG. 6, the layered or plate-like mineral particles 27 dispersed in the inner liner 5 have a direction in which the surface intersects the thickness direction of the inner liner 5 (that is, parallel or parallel to the surface of the inner liner 5. Orientation). In FIG. 6, the arrows indicate the air flow (air leakage) from the inside of the tire to the radial carcass 4. Here, the air passing through the inner liner 5 is forced to detour due to the presence of the layered or plate-like mineral particles 27, and the distance to pass through the inner liner 5 becomes longer. Therefore, in the inner liner 5 of the heavy-duty pneumatic radial tire of the present invention, the passage of air from the inside of the tire is hindered, and the air permeability is reduced. However, when using a high aspect ratio filler such as clay that has been used in conventional inner liners, it is difficult to uniformly disperse the filler during kneading of the rubber composition, resulting in agglomeration, There is a problem that the agglomerates serve as fracture nuclei in the vulcanized rubber composition, causing a decrease in the flex resistance and low temperature durability of the inner liner 5 and reducing the durability of the entire tire. Therefore, in the present invention, by using a plate-like or layered mineral having a specific aspect ratio of 3 or more and less than 30, the air permeability of the inner liner 5 is reduced without impairing the bending resistance and the low temperature durability. To do. As described above, the inner liner 5 of the heavy-duty pneumatic radial tire according to the present invention has a sufficiently reduced air permeability without increasing the gauge, and thus reaches the belt without increasing the tire weight. The amount of oxygen to be reduced can be reduced, the oxygen concentration in the belt covering rubber can be reduced, and oxygen deterioration of the covering rubber can be suppressed. As a result, the cut resistance of the belt is improved, durability on rough roads is further improved, and the life of the tire can be extended.

  As the rubber component of the rubber composition for the inner liner, butyl rubber and diene rubber can be used. In addition, when using butyl-type rubber, what contains halogenated butyl rubber is preferable. The halogenated butyl rubber includes chlorinated butyl rubber, brominated butyl rubber and modified rubber thereof. Here, examples of the chlorinated butyl rubber include a trade mark “Enjay Butyl HT10-66” manufactured by Enjay Chemical Co., Ltd., and examples of the brominated butyl rubber include a trade mark “Bromobutyl 2255” manufactured by Exxon Corporation. Further, as the modified rubber, a chlorinated or brominated modified copolymer of a copolymer of isomonoolefin and paramethylstyrene can be used. Specifically, the trademark “Exxpro50” manufactured by Exxon Corporation, etc. Can be mentioned. Examples of the diene rubber blended with the halogenated butyl rubber include natural rubber (NR), polyisoprene synthetic rubber (IR), cis-1,4-polybutadiene rubber (BR), syndiotactic-1,2- Polybutadiene rubber (1,2BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), and the like. These diene rubbers may be used alone or in combination. Two or more kinds may be mixed and used. The rubber component is preferably composed of 40 to 100% by mass of butyl rubber and 60% by mass or less of diene rubber from the viewpoint of oxygen resistance (air) permeability. However, in the case of aircraft tires and truck / bus tires used under cryogenic conditions, the rubber component preferably contains 60 to 100% by mass or more of a diene rubber, and a rubber component mainly composed of natural rubber is particularly preferable.

  The layered or plate-like mineral used in the rubber composition for the inner liner may be either a natural product or a synthetic product, and is not particularly limited as long as the aspect ratio is 3 or more and less than 30, for example, kaolin clay and sericite. Clays such as clay, mica, feldspar, silica and alumina-containing composites. Among these, kaolin clay, sericite clay and mica are preferable, and kaolin clay is particularly preferable. These layered or plate-like minerals preferably have a particle size of 0.2 to 2 μm, an aspect ratio of preferably 5 or more and less than 30, and more preferably 8 to 20. By setting the aspect ratio to 3 or more, an effect of improving oxygen resistance (air) permeability can be sufficiently obtained, and by setting the aspect ratio to less than 30, deterioration of workability of the rubber composition can be suppressed. Here, the aspect ratio is obtained as a / b from the average major axis a and the average minor axis b by observing the layered or plate-like mineral with an electron microscope, measuring the major axis and minor axis of 50 arbitrary particles. It is done. In addition, the compounding quantity of the said layered or plate-like mineral has the preferable range of 20-160 mass parts with respect to 100 mass parts of said rubber components.

Further, the blending amount A (parts by mass) of the layered or plate-like mineral with respect to 100 parts by mass of the rubber component and the thickness D (mm) of the inner liner are expressed by the following formula (I):
1 <A × D <200 (I)
It is preferable to satisfy this relationship. In this case, oxygen resistance (air) permeability can be sufficiently improved.

Carbon black can be used as a filler in the rubber composition for the inner liner. The compounding amount of the carbon black is preferably in the range of 0 to 60 parts by mass, more preferably in the range of 0.1 to 40 parts by mass, and particularly preferably in the range of 5 to 35 parts by mass with respect to 100 parts by mass of the rubber component. Further, the total amount of the layered or plate-like mineral and carbon black is preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component, from the viewpoint of air permeation resistance, bending fatigue resistance and workability. A range of 60 to 220 parts by mass is more preferable. The type of the carbon black is not particularly limited, and can be appropriately selected from those conventionally used as reinforcing fillers for rubber compositions. For example, FEF, SRF, HAF, ISAF, SAF Grade carbon black can be used. Among these carbon blacks, those having a nitrogen adsorption specific area (N ₂ SA) of 26 to 170 m ² / g are preferable. N ₂ SA is measured according to ASTM D3037-88. The carbon black preferably has an iodine adsorption (IA) of 40 mg / g or less, and a dibutyl phthalate oil absorption (DBP) of 100 mL / 100 g or less. The iodine adsorption amount is measured according to ASTM D1510-95, and the dibutyl phthalate oil absorption amount is measured according to ASTM D2414-97.

  As the rubber composition for the inner liner, 10 to 50 parts by mass of the layered or plate-like mineral with respect to 100 parts by mass of a rubber component composed of at least one butyl rubber selected from the butyl rubber and the halogenated butyl rubber, A rubber composition obtained by blending 10 to 60 parts by mass of the above carbon black is also preferred, and here, the total blending amount of the layered or plate-like mineral and the carbon black is more preferably 50 parts by mass or more.

Moreover, you may mix | blend softeners, such as a naphthenic oil, paraffinic oil, aroma oil, and a blown asphalt, with the said rubber composition for inner liners. The blending amount of the softening agent is not particularly limited, but is preferably in the range of 1 part by mass or more, more preferably in the range of 3 to 20 parts by mass with respect to 100 parts by mass of the rubber component. Here, naphthenic oil, ring analysis (m-d-M added) in accordance% C _N is one of 30 or more, paraffinic oil,% C _P is of 60 or more.

  The rubber composition for the inner liner includes various chemicals commonly used in the rubber industry, such as silane coupling agents, dimethyl stearyl amine, trimethylamine, in addition to the rubber component, layered or plate-like mineral, carbon black, and softener. A dispersion improver such as ethanolamine, a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, an anti-scorch agent, zinc white, stearic acid, etc. may be appropriately selected and blended within a range that does not impair the purpose of the present invention. it can. As these compounding agents, commercially available products can be suitably used.

  The rubber composition for an inner liner is produced by, for example, blending a rubber component with a layered or plate-like mineral and various compounding agents appropriately selected as necessary, kneading, heating, extruding, and the like. can do. The kneading may be performed in one stage or may be performed in two or more stages, and can be appropriately selected according to the total blending amount of the filler and the like.

  The heavy-duty pneumatic radial tire of the present invention is manufactured by an ordinary method using the belt 6 and the inner liner 5 having the three-layer structure. By using the inner liner, the durability of the belt can be improved by reducing the air (oxygen) permeability and reducing the oxygen concentration in the belt without increasing the gauge of the inner liner. The thickness D of the inner liner 5 can be appropriately changed according to the tire size, and is usually in the range of 0.2 to 2.5 mm, but is preferably in the range of 0.8 to 2.5 mm for truck and bus tires. For tires, the range of 1-2 mm is preferred. In addition, as gas with which the heavy-duty pneumatic radial tire of the present invention is filled, inert gas such as nitrogen, argon, helium, etc. can be used in addition to normal or air with adjusted oxygen partial pressure.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

A rubber composition comprising 100 phr of chlorinated butyl rubber, 70 phr of carbon black (GPF), 0 phr of flat clay, 3 phr of stearic acid, 1 phr of sulfur, 2 phr of vulcanization accelerator (DM, dibenzothiazyl disulfide), and 15 phr of spindle oil was prepared, An inner liner A is prepared from the rubber composition, and also comprises 100 phr of chlorinated butyl rubber, 30 phr of carbon black (GPF), 40 phr of flat clay, 3 phr of stearic acid, 1 phr of sulfur, 2 phr of vulcanization accelerator (DM), and 15 phr of spindle oil. A rubber composition was prepared, an inner liner B was produced from the rubber composition, and air permeability was measured by the following method. The chlorinated butyl rubber is a trade mark “Enjay Butyl HT10-66” manufactured by Enjay Chemical Co., and the carbon black (GPF) has an N ₂ SA of 35 m ² / g and an iodine adsorption amount of 36 mg / g. The DBP oil absorption is 90 mL / 100 g, and the above flat clay is manufactured by J. M. Huber, trademark “POLYFIL DL”, and aspect ratio (L / D) = 10.

(1) Air permeability The air permeability coefficient of each inner liner was measured according to method A (differential pressure type) of JIS K7126-1987 “Testing method for gas permeability of plastics film and sheet”. The air permeability coefficient of the liner was taken as 100 and indicated as an index. The smaller the index value, the lower the air permeability and the better.

  Using the inner liner A or B, in the structure shown in FIGS. 1 to 5, the distance between the outermost groove edges of the straight circumferential groove 12 provided in both side regions of the tread portion (corresponding to the distance Lg in FIG. 2). A radial tire for trucks and buses having a chord dimension of 100 mm and a size of 11R22.5 was manufactured. In the example in which the end cover rubber or the rubber layer is disposed, the end cover rubber or the rubber layer is provided on both the innermost cord layer and the intermediate cord layer. In the table, the cord inclination angle is shown as the cord inclination angle of the code layer given the reference numerals 1B, 2B, 3B, 4B in order from the carcass 4 side. In addition, the code | symbol R attached | subjected before the numerical value of an inclination angle represents a code | cord | chord which goes up to the right, and the code | symbol L represents a code | cord | chord which goes up to the left. The cords of each cord layer are all steel cords of 1 × 0.34 + 6 × 0.34, and the number of cords to be driven is 18.0 pieces / 50 mm. Further, the carcass 4 is one ply, and the ply is obtained by rubber-coating a radial arrangement of (3 + 9 + 15) × 0.175 steel cords. Other configurations were in accordance with convention. Next, after oxygen-deteriorating the test tire for two months, the oxygen concentration and durability at the end portion of the intermediate cord layer were evaluated by the following method. The results are shown in Table 1.

2 code between the blanket and the collection of oxygen concentration intermediate cord layer end of the intermediate cord layer end portion was evaluated by measuring the O ₂ wt% in the rubber, the O ₂ wt% of Comparative Example 1 as 100 The index was displayed.

(3) Durability A truck / bus radial ply tire of size 11R22.5 was run under the conditions of a filling internal pressure of 7.5 kgf / cm ² , a load load of 2750 kgf, and a running distance of 1000 km. .

  As is clear from the comparison between the tires of Comparative Examples 2 to 5 and the tires of Comparative Examples 6 to 9, when the inner liner gauge was thickened to reduce the air permeability, the improvement in durability was small. On the other hand, as is clear from the comparison between the tires of Comparative Examples 2 to 5 and the tires of Examples 1 to 4, when the inner liner was filled with flat clay to reduce the air permeability, the durability was improved. The width was large. However, as is clear from the results of Comparative Example 10, the belt structure is a three-layer structure, and the cord crossing layer is formed by the innermost cord layer and the intermediate cord layer, and the inclination angle of each layer and the outermost cord layer coating are formed. If the compression elastic modulus of the rubber is not within the range specified by the present invention, a sufficient durability improvement effect cannot be obtained.

1 is a perspective view of a part of a tread portion of an example of a heavy-duty pneumatic radial tire of the present invention. It is explanatory drawing which expand | deployed the one part front of the tread part of the tire shown in FIG. It is a perspective view of the cord crossing layer end part of the belt of the tire according to the present invention. It is an expanded sectional view of the cord crossing layer end part shown in FIG. It is a perspective view of the other cord crossing layer end part of the belt of the tire according to the present invention. It is a fragmentary sectional view of an example of the inner liner of the heavy-duty pneumatic radial tire of the present invention.

Explanation of symbols

1 Heavy load pneumatic radial tire 2 Tread part 3 Tread rubber 4 Carcass 5 Inner liner 6 Belt 7 Inner cord layer 7a Inner cord layer cord 8 Intermediate cord layer 8a Intermediate cord layer cord 9 Outer cord layer 9a Outer Cord of the cord layer 9b Cord coated rubber of the outermost cord layer 9E Width end of the outermost cord layer 10 Cord crossing layer 11, 12 Circumferential groove 13, 14, 15, 19 Lateral groove 16, 17, 18, 20 Block 21 End cover rubber 22a Inner surface of cord crossing layer 22b Outer surface of cord crossing layer 23 End cover rubber surface 23a Mountain 23b Valley 24 Cord existing position 25 Cord position 26 Rubber layer 27 Layered or plate-like mineral particles P, P ₁ , P ₂ Plane including the tread circumference α Cord inclination angle of intermediate cord layer β Cord inclination of outermost cord layer Outermost groove edge between the developed width Lb of the cord inclination angle Lg outermost circumferential groove in degrees δ innermost cord layer Outermost cord layer width H Wave height difference W Rubber layer width Fx Tension

Claims (15)

A carcass that becomes a one-ply or more rubber-coated radial array cord that reinforces a pair of sidewall portions and a tread portion between bead cores embedded in a pair of bead portions, an inner liner disposed inside the carcass, A belt that reinforces the tread portion on the outer periphery of the carcass, and the belt has three rubber-coated cord layers. Of these cord layers, the innermost cord layer and the intermediate cord layer have a tread portion circle. In the heavy duty pneumatic radial tire, which is a cord crossing layer that intersects with each other across a plane including the circumference, and the tread portion has at least one circumferential groove in each of the both side regions,
Each cord of the innermost cord layer and the intermediate cord layer has an inclination angle within a range of 10 to 25 degrees with respect to the plane, and the cord of the outermost cord layer is from the plane of the cord of the middle cord layer The outermost cord layer has an inclination angle in the range of 45 to 115 ° with respect to the plane as measured in the same direction as the inclination angle of the outermost circumferential groove toward the tread end. Having a width extending beyond the edge of the side groove, the cord covering rubber of the outermost cord layer has a compressive elastic modulus of 200 kgf / cm ² or more,
A heavy-duty pneumatic radial tire characterized by applying a rubber composition comprising a layered or plate-like mineral having an aspect ratio of 3 or more and less than 30 to the rubber component to the inner liner.   2. The heavy-duty pneumatic radial tire according to claim 1, wherein a surface of the layered or plate-like mineral is oriented in a direction intersecting with a thickness direction of the inner liner.   At least one cord layer end portion of the innermost cord layer and the intermediate cord layer has a sheet-like end cover rubber that wraps the end portion, and at least one of both inner and outer surfaces of the cord layer end portion having the end cover rubber The surface has a corrugated surface that forms a crest at a position where a cord exists and a trough at a position between adjacent cords, and the height difference between the crests and valleys is 0.05 to 0.25 mm. The heavy-duty pneumatic radial tire according to claim 1.   The at least one of the innermost cord layer and the intermediate cord layer has a rubber layer bonded to the entire width of the cord layer, and the width of the rubber layer is 0.05 to 5.00 mm. 1. A heavy-duty pneumatic radial tire according to 1. The rubber component comprises 40 to 100% by mass of butyl rubber and 60% by mass or less of diene rubber, and the amount A (parts by mass) of the layered or plate-like mineral with respect to 100 parts by mass of the rubber component, the inner liner The thickness D (mm) of the following formula (I):
1 <A × D <200 (I)
The heavy-duty pneumatic radial tire according to claim 1, wherein:   The pneumatic radial tire for heavy loads according to claim 1, wherein the rubber component contains 60 to 100% by mass of a diene rubber.   The heavy-duty pneumatic radial tire according to claim 5, wherein the butyl rubber includes a halogenated butyl rubber.   The heavy-duty pneumatic radial tire according to any one of claims 1, 2, and 5, wherein the layered or plate-like mineral contains kaolin clay or sericite clay.   The heavy-duty pneumatic radial tire according to any one of claims 1, 2, and 5, wherein the layered or plate-like mineral contains a hydrous composite of silica and alumina. The rubber composition applied to the inner liner is further softened with 0.1 to 40 parts by mass of carbon black having a nitrogen adsorption specific area (N ₂ SA) of 26 to 170 m ² / g with respect to 100 parts by mass of the rubber component. The heavy-duty pneumatic radial tire according to claim 1, comprising 1 part by mass or more of an agent.   The amount of the layered or platy mineral is 20 to 160 parts by mass with respect to 100 parts by mass of the rubber component, and the total amount of the layered or platy mineral and the carbon black is 100 parts by mass of the rubber component. The heavy-duty pneumatic radial tire according to claim 10, wherein the weight is 60 to 220 parts by mass with respect to the part.   The rubber composition applied to the inner liner is obtained by blending 10 to 50 parts by mass of the layered or plate-like mineral and 10 to 60 parts by mass of the carbon black with respect to 100 parts by mass of the rubber component, 11. The heavy-duty pneumatic radial tire according to claim 5, wherein the tire is made of at least one butyl rubber selected from butyl rubber and halogenated butyl rubber.   The heavy-duty pneumatic radial tire according to claim 12, wherein a total amount of the layered or plate-like mineral and the carbon black is 50 parts by mass or more with respect to 100 parts by mass of the rubber component.   The heavy-duty pneumatic radial tire according to any one of claims 10 to 13, wherein the carbon black has an iodine adsorption of 40 mg / g or less and a dibutyl phthalate oil absorption of 100 mL / 100 g or less. The heavy-duty pneumatic radial tire according to claim 7, wherein the halogenated butyl rubber is at least one butyl rubber selected from the group consisting of brominated butyl rubber and chlorinated butyl rubber.

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