JP3163449B2 - Pneumatic radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having improved driving stability without impairing ride comfort.

[0002]

2. Description of the Related Art Hitherto, in order to improve the steering stability of a pneumatic radial tire, a means has been generally applied in which a bead portion reinforcing layer is inserted into a bead portion to increase the rigidity of the bead portion. However, with the increase in the power of the vehicle, it has become impossible to say that the rigidity of the bead portion is not necessarily sufficient if only one bead portion reinforcing layer is used. Tires employing the structure have come to market. However, when a plurality of bead portion reinforcing layers are used, a great effect can be obtained in increasing the rigidity of the bead portion, but it is inevitable that the ride comfort is significantly reduced.

The present inventor has searched for a technique for improving steering stability without increasing the number of bead portion reinforcing layers, and based on a load applied to a radial tire mounted on a vehicle during running and a lateral force at cornering. While analyzing the behavior of the resulting bead core, it was discovered that the placement of the bead core had a very significant effect on steering stability. That is, according to the conventional general perception, the bead core is:
When the tightening force is small, the tire may slip in the circumferential direction due to the traction force or braking force received, but does not locally deform in the tire cross-sectional direction due to the load load or the lateral force at the time of cornering. Was considered. However, according to the detailed research results, it was found that the bead core was locally deformed in the tire cross-sectional direction just below the tire ground due to the applied load and the lateral force. In addition, it has been found that the magnitude of the deformation has a significant effect on steering stability. Based on such knowledge, the inventor has made an invention in which the bead portion reinforcing layer is made into a single layer and the steering stability is improved as described below.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the steering stability of a plurality of layers without reducing the ride comfort by leaving the bead portion reinforcing layer as a single layer. Provided is a radial tire including a tire.

[0005]

The radial tire according to the present invention that achieves the above object has a bead core formed by spirally winding a steel wire on at least the outermost layer and disposing the bead cores on the right and left bead portions. In a pneumatic radial tire in which a single-layer bead portion reinforcing layer is disposed on each bead portion, when the tire is attached to a vehicle and viewed from the front of the vehicle from the front, the outermost layer of the steel wire of the bead core of the left-side bead portion is wound. The winding direction is Z- twisted, the winding direction of the outermost steel wire of the bead core in the right bead portion is S- twisted, and the lower end portion of the bead portion reinforcing layer disposed in the bead portion is in direct contact with the bead core. And the cord direction of the bead portion reinforcing layer is the same as the winding direction of the outermost steel wire of the bead core. It is intended to.

When a bead core in which a steel wire is spirally wound on at least the outermost layer is used, when the tire is mounted on a vehicle and viewed from the front of the vehicle from the front, the outermost layer of the bead core on the left bead portion is formed. In the Z twist direction, the outermost layer of the bead core in the right bead portion is in the S twist direction, so that the tightening force of each bead core by the twist effect is generated by the twist torque generated in the right and left bead cores when the tire is fitted to the rim. Therefore, it is possible to suppress the bead core from being locally deformed in the tire cross-sectional direction immediately below the tire ground due to a load or a lateral force, thereby improving steering stability. Further, a bead portion reinforcing layer was arranged, and the lower end portion was brought into direct contact with the bead core, and the reinforcing cord direction was made to be the same as the winding direction of the outermost steel wire of the bead core. Tension is applied to the reinforcing cord of the bead portion reinforcing layer by the movement (action), and the bead portion rigidity can be further increased. For this reason, even if the bead portion reinforcing layer is a single layer, it is possible to achieve a high level of rigidity comparable to a plurality of layers. Therefore, it is possible to improve the steering stability while maintaining the riding comfort comparable to that of the single-layer bead portion reinforcing layer.

Hereinafter, the tire of the present invention will be specifically described with reference to the drawings. FIG. 1 is a sectional view showing an example of the tire of the present invention when attached to a vehicle and viewed from the front. As shown in FIG. 1, the tire includes a tread portion 1, left and right sidewall portions 2L and 2R, and bead portions 3L and 3R. Bead cores 4L and 4R are buried annularly in the bead portions 3L and 3R on both left and right sides, respectively, and the carcass layer 6 is folded from the inside of the tire to the outside so as to surround the bead filler 5 around these bead cores 4L and 4R. . Between the turn-back portion of the carcass layer 6 and the bead filler 5, one bead portion reinforcing layer 8L, 8R is sandwiched with its lower end in contact with the bead cores 4L, 4R. The tread portion 1 is provided with two belt layers 7.

The bead core 4L embedded in the left bead portion 3L is formed by spirally winding a plurality of steel wires 11 around the outer periphery of a steel wire core 10 in the Z twist direction as shown in FIG. , And the right bead
The bead core 4R embedded in 3R is formed by spirally winding a plurality of steel wires 11 around the outer periphery of a steel wire core 10 in the S twist direction as shown in FIG.

The bead reinforcing layer 8L on the left side, which is sandwiched between the bead filler 5 and the folded portion of the carcass layer 6 with its lower end in contact with the bead core 4L, has a reinforcing cord 8c as shown in FIG. Is arranged in the same direction as the winding direction of the outermost steel wire 11 of the bead core 4L. As shown in FIG. 5, the right bead reinforcing layer 8R has a reinforcing cord 8c whose direction is the same as that of the bead core 4R. The outermost steel wire 11 is arranged in the same direction as the winding direction.

As described above, when mounted on a vehicle and viewed from the front, the outermost layer of the bead core 4L of the left bead portion 3L is in the Z twist direction, and the bead core 4R of the right bead portion 3R.
By setting the outermost layer in the S twist direction, a strong tightening force can be applied to each bead core when the tire is assembled on a rim or when a load is applied, for the reasons described below. It is possible to suppress local deformation of the bead core in the tire cross-sectional direction due to the lateral force or the lateral force.

As shown in FIG. 7, when fitting the tire T to the rim 9, the internal pressure P is applied to spread the right and left bead portions 3L and 3R outwardly while sliding on the rim base. By such an action, the left and right bead portions 3L,
An external twist torque is applied to each of the bead cores 4L and 4R in the 3R, so that a left-handed twist is applied to the left bead core 4L and a right-handed torsion is applied to the right bead core 4R. Therefore, the bead cores 4L and 4R in which the twist direction is set to the outermost bead wire as described above are more and more twisted, so that a strong tightening force is applied. The "tightening force due to the twisting effect" applied to the bead cores 4L and 4R as described above suppresses local deformation of the bead portion in the tire cross-sectional direction immediately below the tire ground due to a load or lateral force during tire running. Acts as a force to do.

The bead core used in the present invention has a steel wire 11 wound spirally as shown in FIGS. 2 and 3 as the outermost layer only, and also has a spirally wound inner layer side as shown in FIG. A steel wire wound in a shape may be provided. The left bead core 4L in FIG. 6 is configured by winding a steel wire core 10 ′ in the S twist direction, and winding the outermost steel wire 11 thereon in the Z twist direction. Even if the inner steel wire layer is spirally wound in this way, the tire is attached to the vehicle, and the twist direction of the outermost steel wire when viewed from the front of the vehicle is used for the right bead portion. Must be S twisted, and the one used for the left bead portion must be Z twisted. The reason why at least the outermost steel wire is configured as described above is that the bead core as a whole has a "tightening force due to twisting".
This is because the number of steel wires is the largest.

Further, the wire diameter, cord structure and the like of the steel wire constituting the bead core used in the present invention are not particularly limited, and the steel wire used in the conventional bead core is used to improve the adhesion to rubber. Which has been subjected to metal plating or an adhesive treatment. When the tire of the present invention, in which the winding direction of the outermost steel wire of the bead core arranged in the bead portion is specified, is rim-assembled or a load is applied, the twisting effect of the outermost steel wire 11 causes the twisting effect of FIG. The movement shown by the arrow in FIG. 3 occurs. This movement is caused by the bead portion reinforcing layer 8.
L. When the direction of the reinforcing cord 8c of the 8R is the same as the twisting direction of the steel wire 11 of the outermost layer of the bead core, the bead portion reinforcing layer 8L. 8R is tensioned. Therefore, even if the bead portion reinforcing layer is a single layer, the bead portion rigidity can be sufficiently increased, so that the steering stability can be improved, and the reduction in ride comfort can be suppressed as much as possible. .

[0014]

【Example】

Example 1 and Comparative Examples 1 to 5 All have the tire structure shown in FIG. 1 and the tire size of 195 / 60R14, and share the point that a 6JJ × 14 rim is used. The tire of the present invention, the comparative tire 1 and the comparative tire 2 having different types of bead cores arranged on the right and left bead portions when viewed from the front and the winding direction of the steel wire and the cord direction and position of the bead reinforcing layer. Comparative tire 3, comparative tire 4, and comparative tire 5 were produced.

[0015]

[Table 1] Left and middle columns of the right bead core in Table 1, the type A, the outermost lay direction Z: Z steel wire 11 of the outermost layer of seven diameter 2.2mm around a steel wire core 10 having a diameter of 3mm helically Figure 2 wound in the twisting direction
Type B, outermost layer twist direction S : seven outermost layer steel wires 11 having a diameter of 2.2 mm are spirally wound around a steel wire core 10 having a diameter of 3 mm in the S twist direction. Figure 2 turned
In the column of the left and right bead reinforcing layers in Table 1, ○: indicates that the twist direction of the outermost bead wire matches the direction of the reinforcing cord of the bead reinforcing layer. .

X: Indicates that the twist direction of the outermost bead wire does not match the direction of the reinforcing cord of the bead portion reinforcing layer. Bias lamination: Two bead portion reinforcing layers were used, a reinforcing layer having a bias structure shown in FIG. 8 was arranged on the left bead portion, and a reinforcing layer having a bias structure shown in FIG. 9 was arranged on the right bead portion.

The above six radial tires were evaluated for steering stability and ride comfort by the following methods. The results are shown in Table 2. Driving stability : The test tires used 6JJ × 14 rims,
When mounted on the vehicle and viewed from the front, the rim is assembled so that the twist directions of the bead cores on the left and right sides are as shown in Table 1, filled with 2.0 kg / cm ² air pressure, mounted on the passenger car, and the pylon is mounted. Driving stability was evaluated based on the average speed of a real vehicle running on a slalom test road that was set up at regular intervals. The evaluation results were compared using the reciprocal of the measured value, and indicated by an index using the value of the comparative tire 1 as a reference (100). The larger the index value, the better the steering stability. Ride comfort : The test tires are mounted on a vehicle using 6 JJ x 14 rims, and are assembled into rims so that the twist directions of the bead cores on the left and right sides are as shown in Table 1 when viewed from the front. Attached to a testing machine, air pressure 2.0 kg / cm ² , load 300 kg, speed 80 k
Under the condition of m / hr, the axial force in the front-rear direction (front-rear direction impact force) at the time of passing over a semicircular protrusion having a diameter of 20 mm attached at one place on the circumference of the drum was detected. The evaluation results are compared using the reciprocal of the measured value, and the value of the comparative tire 1 is used as a reference (10
0). The larger the index value, the better the ride comfort.

[0018] From Table 2, it can be seen that the tire of the present invention has substantially the same ride comfort as the comparative tire 1, but has improved steering stability. On the other hand, the comparative tires 2 and 3 have the same riding comfort as the comparative tire 1, but have reduced steering stability. Further, the comparative tire 4 has no difference in both the riding comfort and the driving stability, and the comparative tire 5 has improved driving stability but decreased riding comfort.

[0019]

According to the present invention, when a bead core in which a steel wire is spirally wound around at least the outermost layer is used, when this tire is mounted on a vehicle and viewed from the front of the vehicle from the front, the left bead portion is formed. The outermost layer of the bead core is Z
In the twist direction, the outermost layer of the bead core in the right bead portion is in the S twist direction, so that the twisting force generated in the right and left bead cores when fitting the tire to the rim reduces the tightening force due to the twist effect on each bead core. Since the bead core can be added, it is possible to suppress the bead core from being locally deformed in the tire cross-sectional direction immediately below the tire ground due to a load or a lateral force, and it is possible to improve steering stability. Further, a bead portion reinforcing layer was arranged, and the lower end portion was brought into direct contact with the bead core, and the reinforcing cord direction was made to be the same as the winding direction of the outermost steel wire of the bead core. A tension is applied to the reinforcement cord of the bead portion reinforcing layer by the movement (action), and the bead portion rigidity can be further increased. For this reason, even if the bead portion reinforcing layer is a single layer, it is possible to achieve a high level of rigidity comparable to a plurality of layers. Therefore, it is possible to improve the steering stability while maintaining the riding comfort comparable to that of the single-layer bead portion reinforcing layer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one example of a case where a pneumatic tire of the present invention is mounted on a vehicle and viewed from the front.

Figure 2 is twisting direction of the outermost layer of the steel wire is a perspective view showing an example of a bead core of a Z twist.

[Figure 3] twisting direction of the outermost layer of steel wire is a perspective view showing an example of a bead core twist S.

FIG. 4 is a plan view showing an example of a bead portion reinforcing layer disposed on the left bead core side.

FIG. 5 is a plan view showing an example of a bead portion reinforcing layer arranged on the right bead core side.

FIG. 6 is a perspective view showing another example of a bead core used in the present invention.

FIG. 7 is a cross-sectional view showing a situation when a pneumatic tire is assembled to a rim.

FIG. 8 is a plan view showing an example of a bead portion reinforcing layer having a bias structure disposed on the left bead core side.

FIG. 9 is a plan view showing an example of a bead portion reinforcing layer having a bias structure disposed on the right bead core side.

[Explanation of symbols]

3L Left bead part 3R Right bead part 4L Left bead core 4R Right bead core 8L Left bead part reinforcement layer 8R Right bead part reinforcement layer 8c Bead part reinforcement cord 9 Rim 10 Steel wire core 10 'Steel wire 11 Outermost layer Steel wire

Claims (1)

(57) [Claims] 1. A pneumatic radial in which a bead core formed by spirally winding a steel wire at least on the outermost layer is arranged on both left and right bead portions, and a single-layer bead portion reinforcing layer is arranged on each bead portion. In the tire, when the tire is attached to the vehicle and viewed from the front of the vehicle, the winding direction of the outermost steel wire of the bead core of the left bead portion is Z- twisted, and the outermost layer of the bead core of the right bead portion is twisted. The winding direction of the steel wire is S- twisted, and the lower ends of the bead portion reinforcing layers disposed on the right and left bead portions are respectively brought into direct contact with the bead cores, and the cord direction of the bead portion reinforcing layer is changed to the bead core. Pneumatic radial tire in the same winding direction as the outermost steel wire.