JP2006035958A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire displaying excellent steering stability, even when large lateral force is generated in a vehicle. <P>SOLUTION: In this tire, a carcass layer 4 is mounted between a pair of bead parts 3, and the carcass layer 4 is wound up from the tire inside to the tire outside around a bead core 5. A bead auxiliary layer 7 made by winding a steel coil 10 machined into a strip shape in a tire peripheral direction so that a plurality of loop parts may be successively partially overlapped, is arranged together with a bead filler 8 made of hard rubber between a main body part 4a and a winding up part 4b in the carcass layer 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire in which a carcass layer is mounted between a pair of bead portions. More specifically, the present invention can exhibit excellent steering stability even when a large lateral force is generated in a vehicle. This relates to a pneumatic radial tire.

  Generally, a pneumatic radial tire has a structure in which a carcass layer is mounted between a pair of bead portions and the carcass layer is wound around the bead core from the inside of the tire to the outside. In such a winding structure, a bead filler having a triangular cross section made of hard rubber is disposed between the main body portion and the winding portion of the carcass layer. In order to increase the rigidity of the bead portion, a steel reinforcing layer formed by arranging a plurality of steel cords at a small angle with respect to the tire circumferential direction is embedded in the bead portion along the carcass layer. (For example, refer to Patent Document 1).

However, it is difficult from the viewpoint of durability to dispose the steel reinforcing layer to a high position toward the tread side. For this reason, even if a steel reinforcing layer is added to the bead portion, sufficient steering stability cannot be obtained at present. In particular, in a liquid transport vehicle such as a bottle delivery vehicle or a tank truck, a large lateral force is generated during cornering. Therefore, if the lateral rigidity of the tire bead portion is insufficient, good steering stability cannot be exhibited.
JP 52-81801 A

  An object of the present invention is to provide a pneumatic radial tire that can exhibit excellent steering stability even when a large lateral force is generated in a vehicle.

  In order to achieve the above object, a pneumatic radial tire of the present invention is a pneumatic radial tire in which a carcass layer is mounted between a pair of bead portions, and the carcass layer is wound around the bead core from the inside of the tire to the outside. A steel coil that has been processed into a strip shape so that a plurality of loop portions partially overlap each other together with a bead filler made of hard rubber is wound between the main body portion and the winding portion of the carcass layer in the tire circumferential direction. This is characterized in that a bead auxiliary layer is arranged.

  In the present invention, a steel coil that has been processed into a strip shape so that a plurality of loop portions partially overlap each other along with a bead filler made of hard rubber between a main body portion and a winding portion of a carcass layer in a tire circumferential direction. By arranging the bead auxiliary layer formed by winding, the bead auxiliary layer and the bead filler function integrally, and the rigidity of the bead portion can be effectively increased. Therefore, in a vehicle having a liquid load and a high center of gravity such as a bottle delivery vehicle or a tank lorry vehicle, excellent steering stability can be exhibited even when a large lateral force is generated during cornering. In addition, the bead auxiliary layer made of a steel coil easily follows the deformation of the bead portion at the time of tire molding, and thus has an advantage that a manufacturing failure hardly occurs.

  The bead auxiliary layer may be embedded in the bead filler, but is disposed between at least one of the carcass layer body portion and the bead filler and between the carcass layer roll-up portion and the bead filler. It is preferable. The bead auxiliary layer is preferably arranged so that the carcass layer winding terminal is included between the upper end position and the lower end position in the tire radial direction. By arranging the bead auxiliary layer made of the steel coil as described above, an optimal reinforcing structure can be formed.

  In the present invention, the steel coil constituting the bead auxiliary layer preferably satisfies the following conditions in order to maximize its function. That is, the width of the strip-shaped steel coil is preferably 30.0 mm to 60.0 mm. The steel coil is preferably composed of a single strand. The wire diameter of the steel coil is preferably 0.15 mm to 0.5 mm. The number of wraps in the loop portion of the steel coil is preferably 3-10. Furthermore, the flatness ratio of the diameter in the tire radial direction to the diameter in the tire circumferential direction of the loop portion of the steel coil is preferably 1/3 to 3.

  The present invention relates to various types of pneumatic radial tires (PC) for passenger cars, pneumatic radial tires (LT) for small trucks, pneumatic radial tires (TB) for trucks and buses, pneumatic radial tires (OR) for construction vehicles, and the like. Although it can be applied to a pneumatic radial tire, particularly when applied to a pneumatic radial tire having a tire flatness ratio of 50% or less, it has a remarkable effect.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a pneumatic radial tire for trucks and buses according to an embodiment of the present invention, and FIG. 2 shows an enlarged bead portion thereof. In FIG. 1, CL is a tire center line, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 is composed of a plurality of carcass cords arranged in the tire radial direction. An organic fiber cord or a steel cord is used as the carcass cord. A bead core 5 is embedded in each bead portion 3, and a carcass layer 4 is wound around the bead core 5 from the tire inner side to the outer side. Thereby, the carcass layer 4 forms the main body part 4a and the winding part 4b with the bead core 5 as a boundary, and terminates at the winding terminal 4e. Further, a steel reinforcing layer 3 a is embedded in the bead portion 3 so as to wrap the bead core 5 and the carcass layer 4. The steel reinforcing layer 3a is composed of a plurality of steel cords arranged so as to be inclined with respect to the tire circumferential direction. Further, a bead filler 8 having a triangular cross section made of hard rubber is disposed between the main body portion 4 a and the winding portion 4 b of the carcass layer 4 on the outer peripheral side of the bead core 5. As the hard rubber constituting the bead filler 8, it is preferable to use a rubber having a hardness (JIS-A) in the range of 55 to 75.

  On the other hand, on the outer peripheral side of the carcass layer 4 in the tread portion 1, a plurality of belt layers 6a to 6d are embedded over the entire circumference of the tire. These belt layers 6a to 6d include a plurality of belt cords inclined at an angle of 15 to 70 ° with respect to the tire circumferential direction, and the belt cords are arranged so as to cross each other at least between a pair of layers.

  In the pneumatic radial tire, as shown in FIGS. 1 and 2, the steel processed into a strip shape together with the bead filler 8 made of hard rubber between the main body portion 4 a and the winding portion 4 b of the carcass layer 4. At least one bead auxiliary layer 7 formed by winding the coil 10 in the tire circumferential direction is disposed. In the present embodiment, two bead auxiliary layers 7 are interposed between the main body portion 4 a of the carcass layer 4 and the bead filler 8 and between the rolled-up portion 4 a of the carcass layer 4 and the bead filler 8, respectively. Yes. However, the bead auxiliary layer 7 may be disposed only in one of the two locations. Further, at least one bead auxiliary layer 7 is arranged so that the winding terminal 4e of the carcass layer 4 is included in a range X defined between the upper end position P1 and the lower end position P2 in the tire radial direction. . At this time, it is preferable that the end of the steel reinforcing layer 3a is also included in the range X. The bead auxiliary layer 7 gives a further improvement effect of the tire performance to the tire structure that already has the minimum function of the radial tire.

  FIGS. 3A to 3B show a steel coil constituting the bead auxiliary layer. As shown in FIGS. 3A to 3B, the steel coil 10 has a plurality of loop portions 11, and is processed into a strip shape so that the loop portions 11 partially overlap each other. For example, a linear brazing portion 12 is formed between the adjacent loop portions 11 and 11.

  The method for forming the steel coil 10 is not particularly limited, but the following methods can be exemplified. That is, after the steel wire is formed into a cylindrical coil shape, a portion between the loop portion of the terminal and the loop portion connected thereto is brazed with the loop portion of the terminal shifted in a direction orthogonal to the coil axis direction. And by repeating this brazing process, the strip-shaped steel coil 10 provided with the brazing part 12 between the adjacent loop parts 11 and 11 is obtained.

  As described above, the bead auxiliary layer 7 formed by winding the steel coil 10 processed in a strip shape so that the plurality of loop portions 11 are partially overlapped in the tire circumferential direction is wound up with the main body portion 4a of the carcass layer 4. When it arrange | positions with the bead filler 8 which consists of hard rubber between the parts 4b, these bead auxiliary layers 7 and the bead filler 8 function integrally, and the rigidity of the bead part 3 can be improved effectively. Therefore, for example, in a vehicle with a liquid load and a high center of gravity, such as a bottle delivery vehicle or a tank truck, excellent maneuvering stability can be achieved even when a large lateral force is generated during cornering as well as during normal driving. Can demonstrate its sexuality. Further, the bead auxiliary layer 7 made of the steel coil 10 easily follows the deformation of the bead portion at the time of molding the tire, so that a manufacturing failure hardly occurs.

  The width W of the steel coil 10 is set in the range of 30.0 mm to 60.0 mm, more preferably in the range of 40.0 mm to 50.0 mm. If this width W is less than 30.0 mm, it becomes difficult to wind the steel coil 10 at a position corresponding to the winding terminal 4 e of the carcass layer 4, so that the productivity of the tire decreases, and conversely, 60.0 mm is reduced. If it exceeds, it becomes difficult to increase the rigidity of the bead portion.

  The steel coil 10 can be composed of a single strand (steel wire) or a steel wire such as a steel cord formed by twisting a plurality of strands, but is desirably composed of a single strand. . Here, the strand diameter d of the steel coil 10 is selected from the range of 0.15 mm to 0.5 mm. If the strand diameter d is less than 0.15 mm, it is difficult to increase the rigidity of the bead portion. Conversely, if it exceeds 0.5 mm, rubber peeling tends to occur in the bead auxiliary layer 7.

  The wrap number N of the loop portion 11 of the steel coil 10 is set in a range of 3-10. If the number N of laps is less than 3, it becomes difficult to increase the rigidity of the bead part. Conversely, if it exceeds 10, the rigidity becomes too high and the load durability deteriorates. Here, the number N of laps of the loop portion 11 of the steel coil 10 is a deviation amount of the loop portion 11 with respect to the diameter D1 in the tire circumferential direction, where δ is the deviation amount of the adjacent loop portions 11 and 11 in the tire circumferential direction. It is the reciprocal of the ratio of δ (δ / D1). That is, when the deviation amount δ in the tire circumferential direction of the adjacent loop portions 11 and 11 is ３ of the diameter D1 of the loop portion 11 in the tire circumferential direction, the number of laps N is three. Therefore, the wrap number N is 3 in the steel coil 10 shown in FIGS.

  The flatness ratio (D2 / D1) of the diameter D2 in the tire radial direction to the diameter D1 in the tire circumferential direction of the loop portion 11 of the steel coil 10 is set in a range of 1/3 to 3. If the flatness ratio (D2 / D1) is out of the above range, the effect of increasing the rigidity of the bead portion becomes insufficient. A more preferable range of the aspect ratio (D2 / D1) is 1/2 to 2.

  4 to 7 are enlarged views of a bead portion of a pneumatic radial tire for trucks and buses according to another embodiment of the present invention.

  In FIG. 4, two layers of bead auxiliary layers 7 are arranged between the main body part 4a and the winding part 4b of the carcass layer 4, and each bead auxiliary layer 7 has two rows of strip-shaped steel coils 10. They are arranged so that they touch each other.

  In FIG. 5, two bead auxiliary layers 7 are arranged between the main body portion 4 a and the winding portion 4 b of the carcass layer 4. Each bead auxiliary layer 7 includes two rows of strip-shaped steel coils 10. They are arranged so that some of them overlap each other. In this case, the overlapping portion of the steel coil 10 is preferably matched with the winding terminal 4 e of the carcass layer 4.

  In FIG. 6, one bead auxiliary layer 7 is disposed between the main body portion 4 a and the winding portion 4 b of the carcass layer 4. The bead auxiliary layer 7 is interposed between the winding portion 4 b of the carcass layer 4 and the bead filler 8.

  In FIG. 7, the steel reinforcing layer is not embedded in the bead part 3, and only the two bead auxiliary layers 7 are arranged between the main body part 4 a and the winding part 4 b of the carcass layer 4.

  In a pneumatic radial tire for trucks and buses having a tire size of 435 / 45R22.5, a steel carcass belt layer in the tread portion, and a steel reinforcing layer embedded in the bead portion so as to wrap the bead core and the carcass layer, Tires of Comparative Examples 1 and 2 and Examples 1 and 2 having different structures only were manufactured.

  In Comparative Example 1, a bead filler made of hard rubber is disposed between the main body portion and the rolled-up portion of the carcass layer, while one steel reinforcing layer having a cord angle of 35 ° with respect to the tire circumferential direction is replaced with another steel reinforcing layer. It is arranged on the outer side in the tire width direction of the rolled-up portion of the carcass layer so that the cord intersects the steel reinforcing layer (see FIG. 8). Comparative Example 2 is a carcass layer in which a two-layer bead auxiliary layer formed by winding a steel coil made of a steel wire having a diameter of 0.4 mm processed in a strip shape in the tire circumferential direction together with a bead filler made of hard rubber. The width W (W = D1) of the steel coil is 14.0 mm, and the number of wraps N is 1. N = 1 is a state where adjacent loop portions do not overlap.

  In Example 1, a two-layer bead auxiliary layer formed by winding a steel coil made of a steel wire having a diameter of 0.4 mm processed into a strip shape in the tire circumferential direction together with a bead filler made of hard rubber and a carcass layer The steel coil width W (W = D1) is 14.0 mm, and the number of wraps N is three. In addition, in Example 2, a two-layer bead auxiliary layer formed by winding a steel coil made of a steel wire having a diameter of 0.4 mm processed in a strip shape in the tire circumferential direction, together with a bead filler made of hard rubber, It arrange | positions between the main-body part of a carcass layer, and the winding-up part, the width W (W = D1) of the steel coil is 10.0 mm, and the number of laps N is 3.

  These test tires were evaluated for steering stability by the following test methods, and the results are shown in Table 1.

Steering stability:
The test tire was mounted on a truck with an air pressure of 900 kPa and a maximum loading capacity of 10 tons, and a feeling evaluation was performed by a test driver on a dry road surface in a full state. The evaluation results are shown as an index with Comparative Example 1 as 100. The larger the index value, the better the steering stability.

表１から判るように、実施例１〜２のタイヤは、操縦安定性が優れていた。一方、比較例１〜２のタイヤは、操縦安定性の改善効果が不十分であった。

As can be seen from Table 1, the tires of Examples 1 and 2 were excellent in steering stability. On the other hand, the tires of Comparative Examples 1 and 2 were insufficient in improving the steering stability.

1 is a meridian half sectional view showing a pneumatic radial tire for trucks and buses according to an embodiment of the present invention. It is sectional drawing which expands and shows the bead part of the pneumatic radial tire of FIG. The steel coil which comprises a bead auxiliary | assistant layer is shown, (a) is a top view, (b) is a side view. It is sectional drawing which expands and shows the bead part of the pneumatic radial tire for trucks and buses which consists of other embodiment of this invention. FIG. 5 is an enlarged cross-sectional view of a bead portion of a pneumatic radial tire for trucks and buses according to still another embodiment of the present invention. FIG. 5 is an enlarged cross-sectional view of a bead portion of a pneumatic radial tire for trucks and buses according to still another embodiment of the present invention. FIG. 5 is an enlarged cross-sectional view of a bead portion of a pneumatic radial tire for trucks and buses according to still another embodiment of the present invention. 3 is an enlarged cross-sectional view of a bead portion of the pneumatic radial tire of Comparative Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 3a Steel reinforcement layer 4 Carcass layer 5 Bead core 6a-6d Belt layer 7 Bead auxiliary layer 8 Bead filler 10 Steel coil 11 Loop part 12 Brazing part

Claims (9)

In a pneumatic radial tire in which a carcass layer is mounted between a pair of bead portions and the carcass layer is wound around the bead core from the inside to the outside of the tire, a hard rubber is provided between the main body portion and the winding portion of the carcass layer. A pneumatic radial tire in which a bead auxiliary layer is formed by winding a steel coil processed into a strip shape in the tire circumferential direction together with a bead filler composed of 2. The pneumatic radial according to claim 1, wherein the bead auxiliary layer is disposed between at least one of a body portion of the carcass layer and the bead filler and between a winding portion of the carcass layer and the bead filler. tire. The pneumatic radial tire according to claim 1 or 2, wherein the bead auxiliary layer is disposed so that a winding terminal of the carcass layer is included between an upper end position and a lower end position in the tire radial direction. The pneumatic radial tire according to any one of claims 1 to 3, wherein a width of the steel coil is 30.0 mm to 60.0 mm. The pneumatic radial tire according to any one of claims 1 to 4, wherein the steel coil is composed of a single strand. The pneumatic radial tire according to any one of claims 1 to 5, wherein a wire diameter of the steel coil is 0.15 mm to 0.5 mm. The pneumatic radial tire according to any one of claims 1 to 6, wherein the number of laps in the loop portion of the steel coil is 3 to 10. The pneumatic radial tire according to any one of claims 1 to 7, wherein a flatness ratio of a diameter in a tire radial direction to a diameter in a tire circumferential direction of a loop portion of the steel coil is 1/3 to 3. The pneumatic radial tire according to any one of claims 1 to 8, wherein a tire flatness ratio is 50% or less.

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