JP2006137372A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of effectively delaying generation of cracks and separation in the vicinity of a belt end. <P>SOLUTION: Reinforcing layers 36 are arranged between widest and second-widest belt plies 24, 25 so as to be across an outer end 25a in the width direction, and a rubber gage therebetween is increased. In addition, reinforcing elements 39, 40 of a large angle of inclination in the same direction as that of reinforcing cords 26, 27 in the belt plies 24, 25 are embedded in the two reinforcing plies 34, 35 to constitute the reinforcing layers 36. The reinforcing plies 34, 35 demonstrate the effect, the angle E of intersection between the reinforcing cords 26, 27 is divided into two or three parts, and the shear strain in a vicinity of the outer end 25 in the width direction is effectively reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

    The present invention relates to a pneumatic tire that can effectively delay the occurrence of cracks in the vicinity of a belt end.

    In general, a tread portion of a pneumatic tire is provided with a belt layer composed of a plurality of belt plies in which a non-stretch reinforcing cord inclined in the opposite direction to the tire equator is embedded. When the pneumatic tire is deformed from an arc shape to a flat shape in the ground contact area, the reinforcing cord in the belt ply is inclined so as to approach the tire equator, and the width direction outer end of the belt layer, in particular, the width direction of the next wide belt ply. A large shear strain is generated at the outer edge.

  Here, the end of the reinforcing cord embedded in the belt ply is exposed in the form of a cut surface to which the adhesive member is not applied at the outer end in the width direction of the belt ply. When such a large shear strain acts repeatedly, cracks are generated in the vicinity of the end of the reinforcing cord, particularly in the vicinity of the outer end in the width direction of the next wide belt ply, and progress to separation. In addition, the inclination of the reinforcing cord as described above also occurs when the pneumatic tire is filled with internal pressure or the tread portion expands radially outward when the pneumatic tire travels at a high speed.

Therefore, in order to delay the occurrence of such cracks and separation in the vicinity of the belt end, for example, the one described in Patent Document 1 below has been proposed.
JP 58-061005 A

  This is provided with a pair of reinforcing layers by disposing a reinforcing ply straddling the outer end in the width direction of the next wide belt ply on the inner side in the radial direction at both ends in the width direction of the widest belt and the next wide belt ply, and In the belt ply, the heat-shrinkable fiber embedded in each reinforcing ply, for example, a strength holder made of polyester is inclined in the opposite direction to the belt ply to which the strength holder is closely attached, and the inclination angle of the strength holder to the tire equator is closely attached This is smaller than the inclination angle of the reinforcing cord.

    However, in such a conventional pneumatic tire, although the inclination of the reinforcing cord at the outer end in the width direction of the belt layer, particularly the next wide belt ply, can be suppressed to some extent by the effect of the reinforcing layer, the reinforcing layer Since the inner strength holder is made of polyester or the like, the above-described effect is not sufficient, and as a result, there is a problem that cracks and separation in the vicinity of the belt end cannot be effectively delayed.

  An object of the present invention is to provide a pneumatic tire that can effectively delay the occurrence of cracks and separation in the vicinity of the belt end.

    The purpose of this is to provide a substantially toroidal carcass layer whose ends are folded around a bead core, and a non-extensible cord that is disposed radially outward of the carcass layer and is inclined with respect to the tire equator. A belt layer composed of at least two belt plies embedded therein, a carcass layer, and a tread disposed radially outward of the belt layer, of the belt plies, a reinforcing cord in the widest belt ply, In a pneumatic tire in which the reinforcement cord in the next wide belt ply arranged in close contact with the widest belt ply is inclined in the opposite direction with respect to the tire equator, the next between the widest belt ply and the next wide belt ply It is possible to straddle two reinforcing plies that straddle the widthwise outer edge of the wide belt ply and that the widthwise inner edge is positioned on the widthwise outer side of the tire equator. A pair of these reinforcing layers are arranged, and among these reinforcing plies, the reinforcing element embedded in the first reinforcing ply in close contact with the widest belt ply is inclined in the same direction as the reinforcing cord in the widest belt ply. In addition, the angle of inclination of the reinforcing element with respect to the tire equator is set to be greater than the angle of inclination of the reinforcing cord in the widest belt ply and not more than 80 degrees, while being embedded in the second reinforcing ply in close contact with the next wide belt ply. The reinforcing element is inclined in the same direction as the reinforcing cord in the next wide belt ply, and the inclination angle of the reinforcing element with respect to the tire equator is not less than 80 degrees and not more than the inclination angle of the reinforcing cord in the next wide belt ply. Can be achieved.

  In this invention, first, a reinforcing layer composed of two first and second reinforcing plies is straddled between the widest belt ply and the next wide belt ply across the outer end in the width direction of the next wide belt ply. As a result, two layers of reinforcing ply coating rubber having a predetermined thickness are interposed between the outer end portions in the width direction of the widest and next wide belt plies. The rubber gauge between the reinforcing cord in the widest belt ply and the reinforcing cord in the next wide belt ply becomes thick, and the shear strain at the outer end in the width direction of the next wide belt ply is reduced.

  In addition, since the reinforcing elements in the first and second reinforcing plies are inclined in opposite directions and intersect each other, the width direction of the next width belt ply is arranged at the outer end in the width direction of the first or second reinforcing ply. Although there is a possibility that a larger shear strain than the outer end may occur, both of these reinforcing plies are considerably narrower than the belt ply, so that the reinforcing element in each reinforcing ply is in the tire equator direction from the reinforcing cord in the belt ply, It can be easily displaced in any direction of the width direction, whereby the value of the shear strain becomes a low value.

  Further, since the reinforcing elements that are inclined in the opposite directions and intersect each other are embedded in the first and second reinforcing plies constituting the reinforcing layer, the first and second reinforcing plies are effective as a whole. As a result, the shear strain at the outer end in the width direction of the next wide belt ply overlapping the first and second reinforcing plies is effectively reduced.

  Moreover, either between the reinforcing cord in the widest belt ply and the reinforcing element in the first reinforcing ply, or between the reinforcing cord in the next wide belt ply and the reinforcing element in the second reinforcing ply. When there is an angle difference, a large crossing angle (obtuse angle) between the reinforcement cord in the widest belt ply and the reinforcement cord in the next wide belt ply is the reinforcement cord in the widest belt ply and the first reinforcement. A first intersection angle (acute angle) between the reinforcing element in the ply and the rest between the reinforcing element in the first reinforcing ply and the reinforcing cord in the next wide belt ply (the reinforcing element in the second reinforcing ply) A first intersection angle (acute angle) between the reinforcement cord in the next wide belt ply and the reinforcement element in the second reinforcement ply, and the reinforcement element in the second reinforcement ply Reinforcement cord in the widest belt ply ( It is divided remaining in the second angle of intersection between the first reinforcing element in the reinforcing ply).

  Further, there is an angular difference between the reinforcing cord in the widest belt ply and the reinforcing element in the first reinforcing ply and between the reinforcing cord in the next wide belt ply and the reinforcing element in the second reinforcing ply. Is present, the large crossing angle (obtuse angle) between the reinforcing cord in the widest belt ply and the reinforcing cord in the next wide belt ply is the same as the reinforcing cord in the widest belt ply and the first reinforcing ply. A first intersecting angle (acute angle) between the reinforcing element and a second reinforcing angle between the reinforcing cord in the next wide belt ply and the reinforcing element in the second reinforcing ply, and the first reinforcing ply. And the remaining third crossing angle between the reinforcement element in the inner reinforcement element and the reinforcement element in the second reinforcement ply. Thus, in any case, the crossing angle between the reinforcing cord and the reinforcing element is reduced, and the shear strain at the outer end in the width direction of the next wide belt ply and the shear strain at the outer end in the width direction of the first and second reinforcing plies are further increased. Reduced.

According to the second aspect of the present invention, the displacement of the reinforcing element in each reinforcing ply can be sufficient while the effect of reducing the shear strain is sufficient.
Furthermore, if constituted as in claim 3, since the cross-sectional area of the end (cut surface) of the reinforcing element exposed at the outer end in the width direction of the reinforcing ply is reduced, the outer end in the width direction of the reinforcing ply is reduced. It is possible to strongly delay the occurrence of cracks.

Moreover, if comprised as described in Claim 4, it will become slow that the crack which generate | occur | produced in the width direction outer side end (cut surface of a reinforcement element) vicinity of a reinforcement ply is connected, and the progress to a separation will be suppressed.
Furthermore, if comprised as described in Claim 5, compared with the case where the width direction deviation | shift amount of the 1st, 2nd reinforcement ply is made into zero, the rigidity level difference in these reinforcement ply ends can be relieved. At the same time, it is possible to delay the connection between the cracks generated near the outer end in the width direction of the reinforcing ply.

Moreover, if comprised as described in Claim 6, since adhesiveness with coating rubber is high compared with the organic fiber reinforcement element which consists of aromatic polyamide, crack generation | occurrence | production can be delayed effectively.
Furthermore, if comprised as described in Claim 7, since the diameter of a reinforcement element can be made small, the crack generation in the width direction outer end vicinity of a reinforcement ply can be delayed strongly.

Embodiment 1 of the present invention will be described below with reference to the drawings.
In FIGS. 1 and 2, reference numeral 11 denotes a pneumatic radial tire for a passenger car that can run at a high speed. The pneumatic tire 11 includes a pair of bead portions 13 in which bead cores 12 are embedded, and a radial direction from the bead portions 13. Side wall portions 14 extending outward are provided, and a substantially cylindrical tread portion 15 that connects the outer ends in the radial direction of the side wall portions 14 is provided.

  The pneumatic tire 11 has a carcass layer 18 that extends in a toroidal shape between the bead cores 12 and reinforces the sidewall portions 14 and the tread portions 15. Both end portions of the carcass layer 18 surround the bead cores 12. Is folded from the axially inner side toward the axially outer side. The carcass layer 18 is composed of at least one carcass ply 19 in this case, and the carcass ply 19 intersects the tire equator S at a cord angle of 70 to 90 degrees, that is, in a radial direction ( A plurality of mutually parallel reinforcing cords 20 made of nylon, aromatic polyamide, steel, etc. (here, nylon) extending in the meridian direction are embedded.

  23 is a belt layer arranged radially outside the carcass layer 18, and this belt layer 23 is constituted by laminating at least two (here, two) belt plies 24, 25 in the radial direction. A large number of mutually parallel non-stretchable reinforcement cords 26 and 27 are embedded in the belt plies 24 and 25, respectively. The reinforcing cords 26 and 27 are inclined at an angle of 10 to 60 degrees with respect to the tire equator S and at an angle of 20 to 30 degrees when the belt rigidity is maximized.

  Here, one of the belt plies, in this embodiment, the belt ply 24 disposed radially inward is the widest belt ply, while the remaining one, in this embodiment, is disposed radially outward. The belt ply 25 is the next wide belt ply arranged in close contact with the widest belt ply 24. The reinforcing cord 26 in the widest belt ply 24 and the reinforcing cord 27 in the next wide belt ply 25 are tires. It inclines in the opposite direction with respect to the equator S and crosses each other.

  Reference numeral 28 denotes a pair of auxiliary layers disposed radially outward at both ends in the width direction of the belt layer 23, and each auxiliary layer 28 is embedded with a reinforcing cord 29 made of nylon extending substantially parallel to the tire equator S. The auxiliary ply 30 is composed of at least one sheet, here, one sheet. 31 is a tread made of rubber disposed radially outside the carcass layer 18 and the belt layer 23. The outer surface (grounding surface) of the tread 31 is wide and has a plurality of continuously extending in the circumferential direction. Then, four main grooves 32 are formed. In addition, a large number of lateral grooves extending in the width direction may be formed on the outer surface of the tread 31.

  When the pneumatic tire 11 is caused to travel while being loaded, the pneumatic tire 11 is deformed from an arc shape to a flat shape in the ground contact region, and as a result, the reinforcing cords 26 in the belt plies 24 and 25 are , 27 is inclined so as to approach the tire equator S, and a large shear strain is generated at the belt layer 23, particularly, the outer end 25 a in the width direction of the next wide belt ply 25. Since such shear strain is repeatedly generated by the running of the pneumatic tire 11, a crack is generated in the vicinity of the widthwise outer end 25a of the next wide belt ply 25 (cutting end of the reinforcing cord 27) and progresses to separation. To do. The inclination of the reinforcing cords 26 and 27 as described above is also caused by the tread portion 15 expanding radially outward when the pneumatic tire 11 is filled with internal pressure or the pneumatic tire 11 travels at a high speed. appear.

  For this reason, in this embodiment, as shown in FIGS. 1, 2, and 3, a pair of reinforcing layers 36 formed by laminating two first and second reinforcing plies 34 and 35 in the radial direction are provided as the uppermost layers. The wide belt ply 24 and the next wide belt ply 25 are arranged so as to straddle the widthwise outer end 25a of the next wide belt ply 25. As a result, the inner end in the width direction of each reinforcing layer 36 is located on the inner side in the width direction from the outer end 25a in the width direction of the next wide belt ply 25, and the outer end in the width direction from the outer end 25a in the width direction of the next wide belt ply 25. Although the inner end in the width direction of the reinforcing layer 36 is located on the outer side in the width direction, the inner end in the width direction is located outside the tire equator S in order to avoid overlapping in the vicinity of the tire equator S. While the outer edge in the width direction must not exceed the tread edge.

  When the reinforcing layer 36 is disposed at the position as described above, the reinforcing layer 36 between the outermost ends in the width direction of the widest and next wide belt plies 24, 25, specifically, the first, which has a predetermined thickness, Two coating rubbers 37 and 38 of the second reinforcement ply 34 and 35 are interposed, and as a result, the reinforcement cord 26 in the widest belt ply 24 and the reinforcement cord 27 in the next wide belt ply 25 are connected. In the meantime, the rubber gauge G becomes thick, and the shear strain at the outer end 25a in the width direction of the next wide belt ply 25 is reduced.

  The reinforcing elements 39 and 40 in the first and second reinforcing plies 34 and 35 are the widest belt ply 24 and the next wide belt ply 25 which are in close contact with the first and second reinforcing plies 34 and 35, respectively. It is inclined in the same direction as the inner reinforcing cords 26 and 27. For this reason, when the grounding area is reached as described above, the inclination angles of the reinforcing elements 39 and 40 change in the same direction as the reinforcing cords 26 and 27, respectively, so that the first and second reinforcing plies 34 and 35 A large shear strain does not occur at the outer end in the width direction.

  Here, since the reinforcing elements 39 and 40 are inclined in the same direction as the reinforcing cords 26 and 27 as described above, they are inclined in the opposite direction and intersect each other. As a result, when reaching the ground contact region as described above, a greater shear strain may occur at the outer end in the width direction of the first or second reinforcing ply 34 or 35 than at the outer end 25a in the width direction of the next belt ply 25. However, since the inner ends of the first and second reinforcing plies 34 and 35 are located outside the tire equator S in the width direction, the width is considerably narrower than the widest and next wide belt plies 24 and 25. As a result, the reinforcing elements 39, 40 in the first and second reinforcing plies 34, 35 are positioned in both the tire equator S direction and the width direction from the reinforcing cords 26, 27 in the belt plies 24, 25. It can be easily displaced, so that the value of the shear strain is low.

  Further, since the reinforcing elements 39 and 40 that are inclined in the opposite directions and intersect each other are embedded in the first and second reinforcing plies 34 and 35 constituting the reinforcing layer 36 as described above, these first elements are buried. The second reinforcing plies 34 and 35 are effective as a whole, so that the second and the second widening plies 34 and 35 are overlapped with the first and second reinforcing plies 34 and 35. The inclination of the reinforcing cords 26 and 27 toward the tire equator S is suppressed, and the shear strain at the widthwise outer end 25a of the next wide belt ply 25 is effectively reduced.

  The inclination angle A of the reinforcing element 39 embedded in the first reinforcement ply 34 with respect to the tire equator S is greater than the inclination angle B of the reinforcement cord 26 with respect to the tire equator S in the widest belt ply 24 and 80 degrees or less. In addition, the inclination angle C of the reinforcing element 40 embedded in the second reinforcement ply 35 with respect to the tire equator S is greater than the inclination angle D of the reinforcement cord 27 with respect to the tire equator S in the next wide belt ply 25 and less than 80 degrees. It is said. Here, when the inclination angles A and B and the inclination angles C and D are both the same angle, the shear strain at the widthwise outer end 25a of the next wide belt ply 25 is reduced for the reason described above.

  On the other hand, when the inclination angle A is larger than the inclination angle B and there is an angle difference between the two, while the inclination angles C and D are the same angle, the reinforcing cord 26 in the widest belt ply 24 is provided. And the reinforcing cord 27 in the next wide belt ply 25 has a large crossing angle E (for example, an obtuse angle of 132 degrees), the reinforcing cord 26 in the widest belt ply 24 and the reinforcing element 39 in the first reinforcing ply 34. Between the first reinforcing ply 34 and the reinforcing cord 27 in the second wide belt ply 25 (the reinforcing element 40 in the second reinforcing ply 35). ) To the remaining second crossing angle (96 degrees).

  On the other hand, when the inclination angle C is larger than the inclination angle D and there is an angle difference between them, when the inclination angles A and B are the same angle, the reinforcement cord 26 in the widest belt ply 24 and the next A large crossing angle E (for example, an obtuse angle of 132 degrees) between the reinforcing cord 27 in the wide belt ply 25 is formed between the reinforcing cord 27 in the next wide belt ply 25 and the reinforcing element 40 in the second reinforcing ply 35. A first intersection angle between them (for example, an acute angle of 36 degrees), a reinforcing element 40 in the second reinforcing ply 35, a reinforcing cord 26 in the widest belt ply 24 (a reinforcing element 39 in the first reinforcing ply 34), Divided into the remaining second crossing angle (96 degrees).

  Further, when the inclination angle A is larger than the inclination angle B and there is an angle difference between them, and the inclination angle C is larger than the inclination angle D and there is an angle difference between them, A large crossing angle E (for example, an obtuse angle of 132 degrees) between the reinforcing cord 26 in the wide belt ply 24 and the reinforcing cord 27 in the next wide belt ply 25 is the same as that of the reinforcing cord 26 in the widest belt ply 24. The first crossing angle (for example, an acute angle of 36 degrees) between the reinforcing element 39 in the first reinforcing ply 34, the reinforcing cord 27 in the next wide belt ply 25, and the reinforcing element 40 in the second reinforcing ply 35. Between the reinforcing element 39 in the first reinforcing ply 34 and the reinforcing element 40 in the second reinforcing ply 35 (e.g., an acute angle of 36 degrees) between 60 degrees).

  As described above, in any case, the crossing angle between the reinforcing cords 26 and 27 and the reinforcing elements 39 and 40 and between the reinforcing elements 39 and 40 is smaller than the crossing angle E. The shear strain at the outer end 25a in the width direction of the ply 25 and the shear strain at the outer ends in the width direction of the first and second reinforcing plies 34, 35 are further reduced. However, as described above, when the inclination angles A and C of the reinforcing elements 39 and 40 with respect to the tire equator S both exceed 80 degrees, the reinforcing elements 39 and 40 do not cross each other, so the first and second reinforcing plies 34, No effect can be expected due to the intersection of the reinforcing elements 39 and 40 in 35. For this reason, the inclination angles A and C must be 80 degrees or less.

  Here, the width W of the first and second reinforcing plies 34 and 35 is preferably in the range of 10 to 50 mm. The reason is that if the width W is less than 10 mm, the effect of reducing the shear strain by the first and second reinforcing plies 34 and 35 is insufficient, while if the width W exceeds 50 mm, the first and second reinforcing plies 34 are increased. This is because the amount of displacement of the reinforcing elements 39 and 40 in 35 is insufficient, and the shear strain at the widthwise outer end 25a of the next wide belt ply 25 cannot be sufficiently reduced. The width W is more preferably 30 mm or more.

  Further, the diameter L of the reinforcing elements 39, 40 in the first and second reinforcing plies 34, 35 may be smaller than the diameter K of the reinforcing cords 26, 27 in the widest and next wide belt plies 24, 25. preferable. This is because the cross-sectional area of the cut surfaces of the reinforcing elements 39 and 40 exposed at the outer ends in the width direction of the first and second reinforcing plies 34 and 35 is reduced in this way. This is because the generation of cracks in the vicinity of the outer ends in the width direction of the reinforcing plies 34 and 35 can be strongly delayed.

  Further, the number of driven elements per unit length of the reinforcing elements 39, 40 embedded in the first and second reinforcing plies 34, 35 is set to the reinforcement cord 26 embedded in the widest and next wide belt plies 24, 25, It is preferable that the distance between the former reinforcing elements 39 and 40 be wider than the distance between the latter reinforcing cords 26 and 27, so that the number of driven per unit length is smaller than 27. The reason for this is that the cracks generated in the vicinity of the outer ends in the width direction of the first and second reinforcing plies 34 and 35 (cut surfaces of the reinforcing elements 39 and 40) are slow to be connected to each other. This is because progress is suppressed.

  The first and second reinforcing plies 34 and 35 constituting the reinforcing layer 36 are preferably laminated while being shifted in the width direction. The reason for this is that, in this way, the outer end in the width direction of the first and second reinforcing plies 34 and 35 is compared with the case where the displacement in the width direction of the first and second reinforcing plies 34 and 35 is zero. This is because it is possible to relieve the rigidity step and to delay the connection of cracks generated near the outer ends in the width direction of the first and second reinforcing plies 34 and 35.

  Further, the reinforcing elements 39 and 40 can be made of non-stretchable steel, aromatic polyamide, nylon or the like, but are more closely attached to the coating rubbers 37 and 38 than organic fibers made of aromatic polyamide or the like. It is preferable to make it from steel with high properties. Note that if the reinforcing cords 26 and 27 in the widest and next wide belt plies 24 and 25 are made of aromatic polyamide, the adhesiveness to the coating rubber is low. Although cracks are likely to occur in 25a, if the reinforcing elements 39, 40 are made of steel as described above, the width direction outer end 25a of the next wide belt ply 25 and the width direction of the first and second reinforcing plies 34, 35 Crack generation in the vicinity of the outer end can be effectively delayed.

  The reinforcing elements 39 and 40 can be formed of a cord in which a plurality of filaments are twisted or a monofilament (single wire). When the reinforcing elements 39 and 40 are formed of a monofilament, the diameter of the reinforcing elements 39 and 40 is reduced. Therefore, the occurrence of cracks in the vicinity of the outer ends in the width direction of the first and second reinforcing plies 34 and 35 can be strongly delayed. For this reason, it is preferable that the reinforcing elements 39 and 40 are made of monofilament.

    4 and 5 are views showing Embodiment 2 of the present invention. The pneumatic tire 11 in this embodiment is for trucks and buses, and the carcass layer 18 is composed of one carcass ply 19 and the pair of auxiliary layers 28 is omitted. A narrow belt ply 45 having a narrower width than the next wide belt ply 25 is disposed outside the next wide belt ply 25 in the radial direction. The narrow belt ply 45 has a reinforcement inside the next wide belt ply 25. An inextensible reinforcement cord 46 having the same inclination direction with respect to the cord 27 and the tire equator S and having a larger inclination angle than the inclination cord 27 is embedded. Other configurations and operations are the same as those in the first embodiment.

    Next, the first test example will be described. In this test, a steel cord is embedded in the widest and next wide belt ply, but a pair of the conventional tire 1 not provided with a reinforcing layer and the widest and next wide belt plies of the conventional tire 1 are paired. Tires 1 to 7 in which a reinforcing layer is disposed, a conventional tire 2 in which an aromatic polyamide cord is embedded in the widest and next wide belt ply, but no reinforcing layer is provided, and the conventional tire Example tires 8 and 9 in which a pair of reinforcing layers are disposed between the two widest and next wide belt plies were prepared.

  Here, each of the tires described above was a tire for a high-performance passenger car, and the size was 225 / 50R16. As shown in FIGS. 1 and 2, the tire skeleton structure has a carcass layer composed of two carcass plies embedded with a nylon cord that intersects the tire equator S at 90 degrees, and the tire equator S. The widest belt ply with a left-up 24 degrees cord and a width of 210 mm was laminated on the outer side in the radial direction of the widest belt ply. A belt layer comprising a next wide belt ply having a width of 180 mm, and an auxiliary layer in which a nylon cord extending substantially parallel to the tire equator S is disposed at both ends in the width direction of the belt layer and extending substantially parallel to the tire equator S It is a thing.

  On the other hand, each reinforcing layer disposed between the widest belt ply and the widest belt ply has a width of a first reinforcing ply that contacts the widest belt ply with a width of 25 mm and a second reinforcing ply that touches the next wide belt ply with a width of 25 mm. It is constructed by laminating while shifting by 5mm in the direction (overall width is 30mm). The widest belt, the next wide belt ply, and the first and second reinforcing plies include a widthwise outer end of the widest belt ply, a widthwise outer end of the first reinforcing ply, a widthwise outer end of the second reinforcing ply, and The next wide belt ply is arranged with its outer end in the width direction shifted sequentially by 5 mm toward the inner side in the width direction. Other specifications of each tire are shown in Table 1 below.

  In Table 1, the inclination angle refers to an inclination angle (degree) of the reinforcing element with respect to the tire equator S, and a rightward increase is represented by plus (+) and a leftward increase is represented by minus (−). In Table 1, element type S1 is a 1 × 3 type reinforcing element composed of three steel filaments with a wire diameter of 0.28 mm, and element type S2 is a steel filament with a wire diameter of 0.17 mm. The element type S3 is a reinforcing element made of a steel monofilament having a wire diameter of 0.28 mm. Furthermore, in Table 1, the element spacing (mm) is the distance between adjacent reinforcing elements. For example, when 100 reinforcing elements are driven in a width of 160 mm, the element spacing is 1.6 mm.

  The cords embedded in the widest belt plies of the conventional tires 1 and 2 and the implementation tires 1 to 9 all have an inclination angle of −24 degrees and a cord interval of 1.6 mm. The cords embedded in the cable had an inclination angle of +24 degrees and a cord interval of 1.6 mm. The cords embedded in the widest and next wide belt plies of the conventional tire 1 and the working tires 1 to 7 are made by twisting three steel filaments having the same wire diameter as the element type S1 and having a wire diameter of 0.28 mm. On the other hand, the cord embedded in the widest and next wide belt ply of the conventional tire 2 and the working tires 8 and 9 is a twist of 0.9 mm in diameter made of an aromatic polyamide. It was a line code.

  Then, after mounting each of such tires on an indoor test machine, the tire was run at 100 km / h with a slip angle of 3 degrees on a drum having a diameter of 3 m while applying a load of 6 kN. At this time, in order to cause a failure near the belt end at an early stage, the internal pressure was set to 140 kPa, which is lower than the normal internal pressure (220 kPa). Then, after running for 10 hours under the conditions described above, each tire was dissected and the crack length in the direction perpendicular to the tire equator S near the belt end was measured. As shown in Table 1. Here, the crack length of the conventional tire 1 was 12 mm, and the crack index of the conventional tire 2 was 142.

    Next, Test Example 2 will be described. For this test, a conventional tire 3 without a reinforcing layer and an implementation tire 10 in which a pair of reinforcing layers are arranged between the widest and next wide belt plies were prepared. Here, each of the tires described above was a truck tire and had a size of 245 / 70R19.5. Further, as shown in FIGS. 4 and 5, the tire skeleton structure has a carcass layer composed of one carcass ply in which a steel cord intersecting the tire equator S at 90 degrees is embedded, and the tire equator S. The widest belt ply with a cord of 25 degrees rising to the left and having a width of 230 mm, the width of the widest belt ply laminated on the radially outer side of the widest belt ply, and the cord of 25 degrees rising to the right with respect to the tire equator S A belt comprising: a next wide belt ply having a width of 200 mm, and a narrow belt ply having a width of 170 mm, which is laminated on the outer side in the radial direction of the next wide belt ply and in which a cord extending 60 degrees to the right with respect to the tire equator S is embedded. And a layer.

  Here, the cords embedded in the three belt plies are all 1 + 5 type cords formed by twisting six steel filaments having a wire diameter of 0.28 mm. The cord spacing was 2mm, and for narrow belt plies the cord spacing was 2.5mm. On the other hand, the reinforcing layer disposed between the widest and next wide belt plies is constructed by laminating the first and second reinforcing plies having a width of 30 mm while shifting by 5 mm in the width direction (the overall width is 35 mm). 2 The center in the width direction of the reinforcing ply is arranged at a position overlapping the outer end in the width direction of the next wide belt ply.

  Further, reinforcing elements made of steel monofilaments having a diameter of 0.35 mm are embedded in the first and second reinforcing plies at an element interval of 3 mm, but the reinforcing elements in the first reinforcing ply in contact with the widest belt ply. Was 60 degrees to the left with respect to the tire equator S, while the reinforcing element in the second reinforcement ply in contact with the next wide belt ply was inclined to 50 degrees with respect to the tire equator S.

  Next, after preparing four trucks from a transportation company running on a paved road in Japan almost all day long, for the two trucks, the conventional tire 3 is used for the front and right rear wheels, and the left rear wheel is used. While the implementation tire 10 is mounted, the remaining two trucks are in regular business running for 18 months with the conventional tire 3 mounted on the front wheel and the left rear wheel and the implementation tire 10 mounted on the right rear wheel (both approximately 100,000 km). Then, each tire was dissected and the crack length in the direction perpendicular to the equator near the belt end was measured. As a result, in the conventional tire 3 attached to the rear wheel, cracks occurred in the vicinity of the end of the next wide belt ply, and the average length was 2 mm. I did not.

  The present invention can be applied to the industrial field of pneumatic tires.

1 is a meridian cross-sectional view of a tire showing Embodiment 1 of the present invention. It is a partially broken plan view of the tread portion. It is meridian sectional drawing of the reinforcement layer vicinity. It is a meridian sectional view of a tire showing a second embodiment of the present invention. It is a partially broken plan view of the tread portion.

Explanation of symbols

11 ... Pneumatic tire 12 ... Bead core
18 ... Carcass layer 23 ... Belt layer
24 ... Widest belt ply 25 ... Next wide belt ply
25a ... Outer edge 26, 27 ... Reinforcement cord
31 ... Tread 34 ... First reinforcement ply
35 ... Second reinforcement ply 36 ... Reinforcement layer
39, 40 ... Reinforcing element S ... Tire equator W ... Width K ... Diameter L ... Diameter

Claims (7)

    At least 2 in which both end portions are folded around a bead core and a substantially toroidal carcass layer, and a non-stretchable reinforcing cord that is disposed radially outside the carcass layer and is inclined with respect to the tire equator is embedded therein A belt layer composed of a plurality of belt plies, a carcass layer, and a tread disposed radially outward of the belt layer. Among the belt plies, a reinforcing cord in the widest belt ply and the widest belt ply In a pneumatic tire in which the reinforcing cord in the next wide belt ply arranged in close contact with the tire equator is inclined in the opposite direction, the width of the next wide belt ply is between the widest belt ply and the next wide belt ply. A reinforcing layer formed by laminating two reinforcing plies that straddle the outer end in the direction and the inner end in the width direction is positioned on the outer side in the width direction from the tire equator The reinforcing elements embedded in the first reinforcing ply that are arranged in pairs and are in close contact with the widest belt ply are inclined in the same direction as the reinforcing cord in the widest belt ply, and the reinforcing plies While the inclination angle of the element with respect to the tire equator is not less than 80 degrees and not less than the inclination angle of the reinforcing cord in the widest belt ply, the reinforcing element embedded in the second reinforcing ply is in close contact with the next wide belt ply. The air characterized in that it is inclined in the same direction as the reinforcing cord in the next wide belt ply, and the inclination angle of the reinforcing element with respect to the tire equator is not less than the inclination angle of the reinforcing cord in the next wide belt ply and not more than 80 degrees. Enter tire.     The pneumatic tire according to claim 1, wherein a width of the first and second reinforcing plies is in a range of 10 to 50 mm.     The pneumatic tire according to claim 1 or 2, wherein the diameter of the reinforcing element in the first and second reinforcing plies is smaller than the diameter of the reinforcing cord in the belt ply.     The number of driving per unit length of the reinforcing element embedded in the first and second reinforcing plies is less than the number of driving per unit length of the reinforcing cord embedded in the belt ply. The pneumatic tire according to any one of the above.     The pneumatic tire according to any one of claims 1 to 4, wherein the first and second reinforcing plies are arranged shifted in the width direction.     The pneumatic tire according to claim 1, wherein the reinforcing element is made of steel.     The pneumatic tire according to claim 6, wherein the reinforcing element is made of a steel monofilament.

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