JP3403545B2 - Pneumatic radial tire - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces the weight by forming a belt layer with a steel wire composed of a plurality of pairs of two spiral wires molded into a predetermined shape. And a pneumatic radial tire that achieves low fuel consumption. 2. Description of the Related Art In recent years, there has been a strong demand for lower fuel consumption of vehicles due to the problem of global environmental pollution. As part of this, weight reduction of pneumatic radial tires has attracted attention as one of the major technical issues. Are gathering. Steel wires are used for belt layers of pneumatic radial tires because of their remarkably superior tensile strength and tensile modulus compared to other organic fibers. However, since the steel wire has a very large specific gravity, it has been an obstacle to reducing the weight and fuel consumption of the tire.
However, there is no existing organic fiber capable of exhibiting a tire performance comparable to that of a steel wire, and for the time being, it is necessary to rely on a steel wire for the time being. [0003] As measures for achieving weight reduction on the premise of using steel wires, it is conceivable to reduce the amount of wire used and the rubber gauge. As one of the means, it can be proposed that a steel wire, in which a plurality of wires are stranded, is constituted only by a single wire. By using a single wire cord in this manner, the cord diameter can be made smaller with the same wire cross-sectional area as compared to a stranded wire, and thereby a tread under-groove gauge (rubber gauge) or a belt-to-cord gauge ( (Rubber gauge) can be reduced, so that the amount of rubber can be reduced and the weight can be reduced. Moreover, in the case of a single wire, the rubber completely covers the periphery of the wire, so that it is possible to improve the corrosion fatigue resistance due to water absorption and the durability against the decrease in adhesion. However, a single-wire wire cord having such a feature also has a drawback that it is rigid because it has no twist, and therefore has low durability against bending deformation and compression deformation due to repeated loads. Insufficient durability causes wire breakage more frequently than tires using a stranded wire cord, causing a reduction in belt durability. [0004] Pneumatic radial tires using a steel wire for the belt layer are disclosed, for example, in JP-A-4-95506, JP-A-5-78990 and JP-A-5-117983.
No., for example. Japanese Patent Laying-Open No. 4-95505 discloses a radial tire in which several single wires are bundled and arranged in a rubberized layer. Japanese Patent Application Laid-Open No. 5-78990 discloses a steel cord comprising a substantially straight wire and a substantially spiral wire.
Further, JP-A-5-117983 discloses that 1 × n (n = 3
Among the steel cords of the measures (5) to (5), a steel cord for reinforcing rubber products using at least one spiral wire is disclosed. SUMMARY OF THE INVENTION An object of the present invention is to achieve a steering stability and a rolling resistance while achieving a reduction in weight and fuel consumption as compared with the case of using a stranded wire by using a single wire. Another object of the present invention is to provide a pneumatic radial tire having excellent tire performance and good workability. According to the present invention, in a pneumatic radial tire in which at least one of the belt layers disposed on the outer peripheral side of the carcass layer of the tread is made of a steel wire, the steel wire has a spiral shape. To type
Attach the two attached single wires to each other, and
So that the circumscribed circles of each of the wire wires are substantially contiguous
A plurality of pairs are arranged in a belt, and the diameter d of the single wire, the spiral diameter D, the pitch length P of the spiral, and the parameter F for specifying the spiral shape F = (D−d) / P
Provided pneumatic radial tires satisfying 0.01 ≦ F ≦ 0.05 0.28 (mm) ≦ d ≦ 0.60 (mm) 2.0 (mm) ≦ P ≦ 8.0 (mm), respectively. Is done. [0007] According to the present invention, the rigidity of the single wire itself is reduced by forming the single wire in a spiral shape, and excellent wire durability (belt durability) against repeated bending deformation and compression deformation is obtained. be able to. However, even if the single wire is too large, the cornering power (steering stability) of the tire is reduced due to a decrease in the tensile modulus. This is to harmonize the above two characteristics by setting the parameter F specified from the single wire diameter d, its spiral diameter D, and the spiral pitch length P in the range of 0.01 to 0.05 as described above. Is made possible. Further, according to the present invention, since the above-mentioned spiral single-wire wires are arranged two by two and arranged on a plurality of pairs of tire belt layers whose spiral diameters are substantially in contact with each other, high compressive rigidity is exhibited. In addition, it is possible to achieve both weight reduction and tire performance such as steering stability and rolling resistance. Here, "the two single-wires are substantially in contact with each other in spiral diameter" means that the gap t between the two single-wires in each cross section in the length direction is t ≦ (D
-D) x2. According to the present invention, since the pair of single wires are both spirally processed, the two single wires do not come into continuous contact with each other. Shows corrosion resistance. In addition, such a pair of single wire can be efficiently produced by simultaneously drawing two single wire by using a wire drawing machine having a double die and forming a spiral . Also, rubber
In the process, two can be handled together, so one by one
Workability is better than wire wire. Hereinafter, the configuration of the present invention will be specifically described with reference to the drawings. In FIG. 1 showing a partially cutaway pneumatic radial tire for a passenger car, reference numeral 1 denotes a tread portion;
Is a carcass layer, which is wound around the pair of left and right bead cores 5 from the inside to the outside of the tire. The cord angle of the carcass layer 2 with respect to the tire circumferential directions E and E 'is substantially 90 degrees. On the outer peripheral side of the carcass layer 2 of the tread portion 1, a pair of inner belt layers 4 and an outer (outermost) belt in which a pair of spiral single-wire wires 40 are embedded as reinforcing steel cords as shown in FIG. The layers 4 'are each arranged over the entire circumference of the tire. The cord angles of these belt layers 4, 4 'with respect to the tire circumferential direction E, E' are 5 to 40 [deg.] And cross each other. On the surface of the tread portion 1, the tire circumferential direction E, E '
Are provided, and a sub-groove 7 intersecting the main groove 6 is provided. In the present invention, the single wire for reinforcing the belt layer is formed into a spiral shape as shown in FIG. That is, the single wire 40 having a diameter d is formed with a spiral diameter D and a spiral pitch length P larger than the diameter d. The spiral diameter D corresponds to an outer circumferential circle of a spiral shape projected on a plane orthogonal to the longitudinal direction of the wire, which is indicated by a broken line in FIG. [0012] The rigidity of the single-wire wire is reduced by being shaped in a spiral as described above.
The tensile modulus is lower than that of a straight single wire. Therefore, even with a single wire that is not a stranded wire cord, the durability (fatigue resistance) against repeated bending loads and compressive loads is improved, and the durability when formed into a belt layer is equal to or higher than that of a stranded wire cord. Can be improved. However, if the degree of shaping of the single wire is too large, the tensile modulus is significantly reduced, so that the lateral rigidity of the belt layer is reduced. As a result, the cornering power is reduced, and it becomes difficult to maintain the steering stability equivalent to the use of the stranded wire cord. [0013] The spiral shape imprinted on the single-wire wire has an amount (D-
d) and the pitch length P of the spiral can be characterized.
Parameter F = (D−d) / P, which is the ratio of d) and P
The correlation with the fatigue resistance and tensile modulus of the wire described above can be further clarified, and thus the correlation with the durability and cornering power (steering stability) of the belt layer. Clarify gender. In the present invention, the parameter F is in the range of 0.01 ≦ F ≦ 0.05. FIG. 4 shows a single wire (d) as shown in FIG.
= 0.4 mm) and the cornering power (Cp) when the parameters F are arranged as a pair as shown in the figure.
FIG. 4 is a graph showing a relationship with the values of FIG. In this figure, according to the present invention, the Cp value when F = 0 (control example: broken wire) is set to 100, and the Cp value when the value of F changes is indicated by an index, and FIG. Value of 0.01 to
It is clear that it should be 0.05. Further, in the present invention, the diameter d of the single wire and the pitch length P of the spiral are 0.28 (mm) ≦ d ≦ 0.60 (mm) 2.0 (mm) ≦ P ≦ 8.0 ( mm). The diameter d of the single wire is 0.2
By setting the spiral pitch length P to 8.0 mm or less and the spiral layer pitch length P to 8.0 mm or less, the thickness of the belt layer becomes excessively large, preventing reduction in belt rigidity and weight increase, and reducing the diameter d to 0.60 mm or less. By setting the pitch length P to 2.0 mm or more, the fatigue resistance of the single wire is further improved. In the present invention, as described above, since a pair of single-wire steel wires are used as the steel cords constituting the belt layer, the periphery thereof is completely covered with the coating rubber, and is excellent in water-resistant adhesion and rust resistance. Can be something. Further, since the wire is a single wire, the cord diameter can be reduced when the wire has the same wire cross-sectional area as compared with the stranded wire cord. Therefore, the outermost belt layer 4 ′ from the groove bottom of the main groove 6 formed in the tread is formed. The gauge t (see FIG. 2) below the groove up to the single wire 40 can be reduced, thereby reducing the amount of rubber and reducing the weight.
For the same reason, the interval a (gauge between cords) of the spiral diameter D of the single wire 40 constituting the inner belt layer 4 and the outer belt layer 4 'can be reduced, so that the weight can be further reduced. Further, since the interlayer shear force is increased by reducing the gauge a between the cords, the cornering power can be increased. In the present invention, it is preferable that the under-groove gauge t obtained by the above-mentioned effect be in the range of 1.5 to 3.5 mm. Moreover, inter-cord gauges a, in the radial tire for passenger cars 0.15～0.8Mm, trucks, it is preferable in the range of 0.4~1.2mm a heavy duty radial tire such as a bus. The present invention is suitable mainly for application to pneumatic radial tires for passenger cars, but is also applicable to pneumatic tires for other uses such as for trucks and buses. Examples of the present invention will be described below, but it goes without saying that the technical scope of the present invention is not limited to the following examples. Tire size 175 / 70R1
3. Carcass cord is polyester fiber cord 1500
D / 2, the width of the inner belt layer was 120 mm, the width of the outer belt layer was 110 mm, the gauge under the groove t was 3.5 mm, the gauge a between the cords was 0.64 mm, and the steel cords of the inner belt layer and the outer belt layer were used. As shown in FIG. 2, two single-wire steel wires shown in FIG. 3 are composed of a plurality of pairs, and the intersection with each other is set at an angle of 20 ° with respect to the tire circumferential direction. The diameter d of the single wire was set to 0.40 mm, and the parameter P was changed by changing the pitch length P and the diameter of the spiral, and the tires of Comparative Examples 1 to 4 and the tires 1 to 6 of the present invention of Examples 1 to 5 were changed. Various kinds of radial tires were manufactured. For comparison, a steel cord in which two strands of wire having a diameter d = 0.28 mm and a stranded wire having a cord structure × 2 were used, and a belt layer was formed with 49/50 mm width end numbers. A conventional tire (control example) having the same configuration as the comparative tire 1 was produced. With respect to these 11 types of radial tires, a cornering power Cp, a high-speed durability by a drum test after moisture absorption, a slalom durability (belt durability), and a weight reduction index were evaluated by the following methods. The results are shown in Table I, and the relationship between F and Cp is shown in FIG. Cornering power Cp : A test tire was 13 × 5 at 200 kPa (2.0 kgf / cm ² ) of air alkyl.
-The rim is assembled on a rim of -J, and is run on a drum having a diameter of 1707.6 mm with a load of 2942N (300 kgf / cm ² ) at a speed of 10 km / hr. The average of the absolute values of the lateral force and the lateral force when the slip angle was 1 ° to the left was measured. Based on the measured value of the conventional tire (1
00). The larger the index value is, the larger the Cp is, indicating that the steering stability is excellent. Slalom durability : The test tire was subjected to an air pressure of 1
At 70 kPa (1.7 kgf / cm ² ), the rim was assembled on a 13 × 5-J rim, and the humidity was adjusted in the same manner as in high-speed durability. A slip angle of 0 ± 5 ° was applied on a 1707.6 mm diameter drum, and the load was adjusted. 3432N (350kgf) ± 2157N (220kgf)
The vehicle was run for 300 km with the load and slip angle varied with a rectangular wave of 0.067 Hz under the above-mentioned variation conditions. After running, the test tire was incised and the presence or absence of a belt cord was shown in Table I. [Table 1] According to the present invention, the steel cord of the belt layer can be reduced in weight by arranging a plurality of pairs of two single-wire wires so that the spiral diameters thereof are substantially in contact with each other. Moreover, since the single wire is shaped in a spiral shape and used as a pair, and the parameter F for specifying the spiral shape is set within a certain range, the rigidity inherent in the single wire is relaxed, and a good resistance is obtained. Since it is a collection of single wires that have fatigue properties and are not twisted with each other, they exhibit high compression rigidity and achieve weight reduction, good steering stability (cornering power) and rolling resistance, and are also excellent in corrosion resistance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an essential part perspective sectional view showing an example of a pneumatic radial tire for a passenger car according to an embodiment of the present invention, with a part cut away. FIG. 2 is an enlarged cross-sectional view schematically illustrating an example of a state where a pair of single-wire wires spirally formed in accordance with the present invention are arranged on an inner belt layer of the tire of FIG. 1; FIG. 3 is a side view showing one example of a spirally shaped single wire used in the present invention. FIG. 4 is a graph showing a relationship between a parameter F of a single wire and a cornering power Cp in the example of the present invention. [Description of Signs] 1 ... Tread portion 4 ... Inner belt layer 4 '... Outer (outermost) belt layer 6 ... Main groove 40 ... Single wire d ... Wire diameter D ... Spiral diameter P ... Spiral pitch length

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-270212 (JP, A) JP-A-4-95507 (JP, A) JP-A-6-255312 (JP, A) JP-A-4-254 95505 (JP, A) JP-A-48-63961 (JP, A) JP-A-4-84395 (JP, U) JP-A-5-46997 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 9/00, 9 / 18-9 / 20 D07B 1/06

Claims (1)

(57) [Claim 1] In a pneumatic radial tire in which at least one of the belt layers disposed on the outer peripheral side of a carcass layer of a tread is formed of a steel wire, a single wire in which the steel wire is spirally formed. Pull two wires at a time
The circumcircle of each of the two solid wires is substantially
It consists of a plurality of pairs arranged in a belt so as to be in contact with each other,
The diameter d of the single wire, the spiral diameter D, the spiral pitch length P, and the parameter F = (D−d) / P for specifying the spiral shape are 0.01 ≦ F ≦ 0.05 0.28 (mm), respectively. ≤ d ≤ 0.60 (mm) 2.0 (mm) ≤ P ≤ 8.0 (mm) A pneumatic radial tire.